Okay, so in my last post i chatted a bit about biohacking, and how it could be a good thing. However in the wrong hands, it could be a dangerous thing, most likely to the user.
The first danger comes from the scientific equipment itself. The people at DIYbio will likely have thought a bit about this, and understood the risks involved. People following in their footsteps may not. For instance, they may be working with equipment that they rig up themselves, that could be faulty. Electrophoresis gel tanks will give a nasty shock, but they are nothing compared to centrifuges when they go wrong. These people may be working with substandard equipment that is second hand. This is more a mental danger, as I have known of grown men reduced to gibbering wrecks upon finding out that a -80 freezer died taking with it ten years of hard work.
So anyway, I'm going to assume that these people know what they are doing, because otherwise what's the point. Even when you know what you're doing in biology, most of your experiments will fail to work.
Anyway, another danger will be the bacteria themselves. Not necessarily the laboratory strains you can get from a catalogue, but wild contaminants, which will start growing on these plates as soon as possible. If you start growing up lots of bacteria, they will get everywhere. If you are doing these experiments in the kitchen, it is almost like shitting where you eat. One solution would be to do these sorts of experiments in a garage, or somewhere isolated, and using antibiotic selective media.
Only problem with that is that you start enriching for antibiotic resistant bacteria in the home environment. So MRSA, which generally is outcompeted by non-resistant strains when there is no selection present, will do better. If an amateur is really careless, they may just infect themselves if MRSA. But this will only happen with extreme carelessness, like if a person decides to chuck their plates out with the trash rather than autoclaving them immediately after they see contamination (something that most people would do, as contamination often indicates that your experiment just fucked up)
also, many experimental bacterial models, such as e.coli, are derived from human microbial flora, which can turn into pathogens at the drop of a hat. Some people are making the switch to using B. subtilis as a model to build constructs in, as it is practically non-pathogenic (for a given value of practically).
But considering that most labs avoid these problems shows that they aren't insurmountable. However, someone who may want to try doing these sorts of things may have the mad scientist urge without the experience to back it up. That is when problems occur, and if it happens to just one person, it will affect the whole community. Which brings me to probably the biggest danger facing backyard scientists.
Media hysteria. The moment anything untoward happens , the media will most certainly turn against these innovators. If someone mentions that we're modifying e.coli, alomost certainly there will be a sentence afterwards describing the diseases it causes. followed by a vox pop from some next door neighbour who now lives in abject fear of the mad scientist who lives next door. Then they talk to an expert scientist who says that theoretically these labs could be dangerous, and the rest of what he says is cut from the text because it's deemed too boring for use in national newspapers.
It'll be only a matter of time before some dumb arse brings out this quote
Dr. Ian Malcolm: I'll tell you the problem with the scientific power that you're using here: it didn't require any discipline to attain it. You read what others had done and you took the next step. You didn't earn the knowledge for yourselves, so you don't take any responsibility... for it. You stood on the shoulders of geniuses to accomplish something as fast as you could and before you even knew what you had you patented it and packaged it and slapped it on a plastic lunchbox, and now you're selling it, you want to sell it
and the part of the human brain designed to fear raptors kicks into gear, and people run screaming into the streets. okay, maybe not. But from reading the headlines of these not yet written papers, you could be forgiven for thinking that this is what's happening.
I'll be honest here as well, I feel quite snobbish towards amateur science. Partly because of an irrational reflex action that says "Science can't possibly happen outside of a lab" and partly because like many scientists I worked long and hard to get the right to work in a lab, and somehow this biohacking on the surface seems like a way to backdoor this process, even though for the reasons above it clearly is not easy in any way.
I half remember an eminent professor telling me "If research was easy, everybody would be doing it". If you don't understand why that statement now chills me, i'm not really going to bother to explain.
Thursday, 1 January 2009
Biohacking, Brilliant
It's been a long time since I posted, been busy doing science and other such things.
There has been some hoo-ha recently as to the relatively new fad of "Biohacking". The concept itself is quite interesting. Many different technologies have in the past benefited from experiments developed by amateurs. The thing that immediately springs to mind is the clockwork radio.
What I find incredibly interesting is how these amateurs manage to perform expensive techniques using household equipment. I recommend looking at this link:
http://www.scq.ubc.ca/the-macgyver-project-genomic-dna-extraction-and-gel-electrophoresis-experiments-using-everyday-materials/
Whilst the DNA extraction process is nothing new (In science class, I remember extracting DNA from a kiwi fruit) the way in which electrophoresis is performed is ingenious, using non-toxic products and stains.
However, looking on their website there are very few techniques available which allow for effective cloning. So amateur enthusiasts will have to shell out a lot of money to buy the appropriate equipment. There is the possibility of getting used items. But not all DIY enthusiasts will have this oppurtunity. I look forward to seeing how people will solve these problems.
The biggest problem facing these enthusiasts is PCR. This is the one technique that is essential for cloning genes, which is necessary if they are going to do the things they set out to do on their website. The lowest cost for these machines (outside of eBay) is around a thousand pounds.
one backyard solution to this would be to use a multiple waterbath (or heat block) system. You could use a kettle, and stick a variable resistor on the circuit, and then use a thermometer to optimise the temperatures. you would then spend several hours switching your samples between water baths (each step takes about 30 seconds, so don't even think about taking a break during your 5 hour home PCR). Automation can be achieved by using a lego mindstorms kit or something like that to automatically switch samples. An even better machine would have a hotplate on the top of the rack where you would place your DNA and primer mix, which removes the need to use mineral oil in your reactions. No doubt, there is probably someone working on this as I speak.
The people working on this project have high expectations, which I hope that they can achieve without electrocuting or poisoning themselves and their environment. The most achievable goal of this movement would be to test and increase the diversity of plasmids available on the parts registry. This is completely open source, and available to all scientists. Not only that, but creating cheaper science without losing quality is extremely desirable for pure science labs which will no doubt be the target of budget cuts over the next few years.
So actually, the best thing that is likely to come out of this project is not necessarily a tangible biological product, but efficient and cheap machinery for doing biological reactions. The unique challenges of amateur sciences will require the application of safer techniques, that are limited by the amount of disposable income of the user.
This can only be good for labs.
There has been some hoo-ha recently as to the relatively new fad of "Biohacking". The concept itself is quite interesting. Many different technologies have in the past benefited from experiments developed by amateurs. The thing that immediately springs to mind is the clockwork radio.
What I find incredibly interesting is how these amateurs manage to perform expensive techniques using household equipment. I recommend looking at this link:
http://www.scq.ubc.ca/the-
Whilst the DNA extraction process is nothing new (In science class, I remember extracting DNA from a kiwi fruit) the way in which electrophoresis is performed is ingenious, using non-toxic products and stains.
However, looking on their website there are very few techniques available which allow for effective cloning. So amateur enthusiasts will have to shell out a lot of money to buy the appropriate equipment. There is the possibility of getting used items. But not all DIY enthusiasts will have this oppurtunity. I look forward to seeing how people will solve these problems.
The biggest problem facing these enthusiasts is PCR. This is the one technique that is essential for cloning genes, which is necessary if they are going to do the things they set out to do on their website. The lowest cost for these machines (outside of eBay) is around a thousand pounds.
one backyard solution to this would be to use a multiple waterbath (or heat block) system. You could use a kettle, and stick a variable resistor on the circuit, and then use a thermometer to optimise the temperatures. you would then spend several hours switching your samples between water baths (each step takes about 30 seconds, so don't even think about taking a break during your 5 hour home PCR). Automation can be achieved by using a lego mindstorms kit or something like that to automatically switch samples. An even better machine would have a hotplate on the top of the rack where you would place your DNA and primer mix, which removes the need to use mineral oil in your reactions. No doubt, there is probably someone working on this as I speak.
The people working on this project have high expectations, which I hope that they can achieve without electrocuting or poisoning themselves and their environment. The most achievable goal of this movement would be to test and increase the diversity of plasmids available on the parts registry. This is completely open source, and available to all scientists. Not only that, but creating cheaper science without losing quality is extremely desirable for pure science labs which will no doubt be the target of budget cuts over the next few years.
So actually, the best thing that is likely to come out of this project is not necessarily a tangible biological product, but efficient and cheap machinery for doing biological reactions. The unique challenges of amateur sciences will require the application of safer techniques, that are limited by the amount of disposable income of the user.
This can only be good for labs.
Tuesday, 22 April 2008
Coughs and Sneezes Spread.....Schizophrenia ?
There has been a recent article in Scientific American which links schizophrenia to Infection by a disease, such as influenza. Now this may seem strange to you, but it is not completely bollocks.
It is already well known that if a mother gets especially stressed during preganacy, her stress hormones can cross the placenta and this can cause problems for the baby.
When you get an infection, your immune system produces cytokines, which can trigger stress through the hypothalamo-pituitary-adrenal axis, which can cause an upregulation in stress hormones.
So essentially, when the baby recieves these hormones, it is essentially bieng told that the world outside is a stressful place. Because of this, it changes the sensory apparatus in it's brain to adapt to this situation. It has been shown that animals whom are born in stressful pregnancies have a tendency be more alert to stressful stimuli. This means that they generally become more stressed, more easily.[11] This is known as Foetal programming, and is believed to have an effect on many disorders.
It has been hyopothesised that one possible adaptation to this sort of stress is schizophrenia[10]. However, there has been no study which has been able to conclusively say that influenza infection causes schizophrenia.
That is mostly because in order to do this, you will have to actually get a statistically significant number of young mothers to agree to be infected with influenza, so that we can see whether the children develop schizophrenia. It just isn't going to happen, and even if you did find the right number of mothers, few researchers would have the patience to wait that long for results. Because of this lack of conclusive evidence, it is still a hypothesis rather than a theory.
There are lots of studies which have tried find correlations between schizophrenia and a variety of factors. One problem with this is that they often look exclusively at schizophrenic patients, and work backwards from there. There was one study that found that a large number of schizophrenic people had mothers who were infected with flu during pregnancy. However, they were not able to show any evidence that the number of mothers infected with influenza was any different from the rest of the population [1] However, there have been some convincing articles which have shown that in years with epidemic influenza, there has been an increase in schizophrenia incidence [2]. However, it could be that the stress induced by the pandemic itself could cause this, and there are flaws to the methodology which have not been adequately been addressed. [3]
The most strongest factor at the moment i.e. the one you should worry about the most is genetics. it is possible to screen people genetically, and give them a probability telling them how likely they are to get schizophrenia.
But this does not explain everything. There are still people who get schizophrenia without having these genes, and there are people who have these genes that don't. It is possible that infection could explain this, but it's still only a hypothesis at the moment, and one of many [4][5][6][7].
The fact that schizophrenia is such a hard to define disorder is not helping either. It is possible that it is an umbrella term for a number of disorders which show the same symptoms. it is likely that there are distinctly different diseases , like "Genetically Induced Schizophrenia" , "Stress Induced Schizophrenia" , "Perinatal Infection-Induced Schizophrenia" or "Genetically, Perinatal Infection and Stress induced Schizophrenia", which can interract with eachother to make schizophrenia development more likely.
Because of this, it is unlikely that there will be any definate cure for everybody, as people who have schizophrenia often have it as a result of different factors.
However, this is not a problem for Big Pharmaceutical companies, because they prefer to treat symptoms rather than create cures. ("if you cure someone, they won't come back for another prescription")
And to be honest, this is the only appropriate way to control schizophrenia until we actually can determine the root causes.
Should we panic about Influenza causing schizophrenia?
No, not yet. At the moment there is is a much greater level of evidence showing that genetics correlate better to schizophrenia [8]. The evidence that anxiety during pregnancy can cause schizophrenia in children is also higher. So panicking itself would cause things to worsen. If there are any pregant women reading this blog, I have just increased their chances of giving birth to someone who will be schizophrenic in later life [9]. Read that again if it doesn't scare you.
Okay, i'm being overdramatic here, but you should get my point. You should not panic about this. But don't take my word for it. I have supplied a long list of references, and it is likely that I have missed out some important points.If you can find the time read through them yourself, and make up your own mind.
References
[1]Exposure to Influenza in the Womb May Increase Risk of Schizophrenia by Amanda Barrett, MA @ http://www.swedish.org/19559.cfm
[2] SCHIZOPHRENIA AFTER PRENATAL EXPOSURE TO 1957 A2-INFLUENZA EPIDEMIC by OCALLAGHAN E, SHAM P, TAKEI N, GLOVER G, MURRAY RM in LANCET Volume: 337 Issue: 8752 Pages: 1248-1250 Published: MAY 25 1991
[3] "On the plausibility of ''The neurodevelopmental hypothesis'' of schizophrenia" by Weinberger DR in NEUROPSYCHOPHARMACOLOGY Volume: 14 Issue: 3 Pages: S1-S11 Supplement: Suppl. S Published: MAR 1996
[4] "Maternal household crowding during pregnancy and the offspring's risk of schizophrenia" by Kimhy D (Kimhy, David), Harlap S (Harlap, Susan), Fennig S (Fennig, Shmuel), Deutsch L (Deutsch, Lisa), Draiman BG (Draiman, Benjamin G.), Corcoran C (Corcoran, Cheryl), Goetz D (Goetz, Deborah), Nahon D (Nahon, Daniella), Malaspina D (Malaspina, Dolores) in Schizophrenia Research Volume: 86 Issue: 1-3 Pages: 23-29 Published: SEP 2006
[5] "Season of birth and schizophrenia in Northeast Brazil - Relationship to rainfall" by Messias E (Messias, Erick), Mourao C (Mourao, Carine), Maia J (Maia, Juliana), Campos JPM (Campos, Joao Paulo Mendes), Ribeiro K (Ribeiro, Kersia), Ribeiro L (Ribeiro, Luciana), Kirkpatrick B (Kirkpatrick, Brian) in JOURNAL OF NERVOUS AND MENTAL DISEASE Volume: 194 Issue: 11 Pages: 870-873 Published: NOV 2006
[6] "Schizophrenia-proneness, season of birth and sleep: Elevated schizotypy scores are associated with spring births and extremes of sleep" by ): Reid HM (Reid, Howard M.), Zborowski MJ (Zborowski, Michael J.) in PERSONALITY AND INDIVIDUAL DIFFERENCES Volume: 41 Issue: 7 Pages: 1185-1193 Published: NOV 2006
[7] "Biological hypotheses of schizophrenia: Possible influences of immunology and endocrinology" by Sperner-Unterweger B in FORTSCHRITTE DER NEUROLOGIE PSYCHIATRIE Volume: 73 Pages: S38-S43 Supplement: Suppl. 1 Published: NOV 2005
[8] "Linkage of a neurophysiological deficit in schizophrenia to a chromosome 15 locus" by Freedman R, Coon H, MylesWorsley M, OrrUrtreger A, Olincy A, Davis A, Polymeropoulos M, Holik J, Hopkins J, Hoff M, Rosenthal J, Waldo MC, Reimherr F, Wender P, Yaw J, Young DA, Breese CR, Adams C, Patterson D, Adler LE, Kruglyak L, Leonard S, Byerley W in PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Volume: 94 Issue: 2 Pages: 587-592 Published: JAN 21 1997
[9] "Higher risk of offspring schizophrenia following antenatal maternal exposure to severe adverse life events" by Khashan AS (Khashan, Ali S.), Abel KM (Abel, Kathryn M.), McNamee R (McNamee, Roseanne), Pedersen MG (Pedersen, Marianne G.), Webb RT (Webb, Roger T.), Baker PN (Baker, Philip N.), Kenny LC (Kenny, Louise C.), Mortensen PB (Mortensen, Preben Bo) in ARCHIVES OF GENERAL PSYCHIATRY Volume: 65 Issue: 2 Pages: 146-152 Published: FEB 2008
[10] "Schizophrenia and phenotypic plasticity: Schizophrenia may represent a predictive, adaptive response to severe environmental adversity that allows both bioenergetic thrift and a defensive behavioral strategy" by Reser, Jared E in MEDICAL HYPOTHESES Volume: 69 Issue: 2 Pages: 383-394 Published: 2007
[11] "Prenatal glucocorticoids and long-term programming" in EUROPEAN JOURNAL OF ENDOCRINOLOGY Volume: 151 Pages: U49-U62 Supplement: Suppl. 3 Published: NOV 2004
It is already well known that if a mother gets especially stressed during preganacy, her stress hormones can cross the placenta and this can cause problems for the baby.
When you get an infection, your immune system produces cytokines, which can trigger stress through the hypothalamo-pituitary-adrenal axis, which can cause an upregulation in stress hormones.
So essentially, when the baby recieves these hormones, it is essentially bieng told that the world outside is a stressful place. Because of this, it changes the sensory apparatus in it's brain to adapt to this situation. It has been shown that animals whom are born in stressful pregnancies have a tendency be more alert to stressful stimuli. This means that they generally become more stressed, more easily.[11] This is known as Foetal programming, and is believed to have an effect on many disorders.
It has been hyopothesised that one possible adaptation to this sort of stress is schizophrenia[10]. However, there has been no study which has been able to conclusively say that influenza infection causes schizophrenia.
That is mostly because in order to do this, you will have to actually get a statistically significant number of young mothers to agree to be infected with influenza, so that we can see whether the children develop schizophrenia. It just isn't going to happen, and even if you did find the right number of mothers, few researchers would have the patience to wait that long for results. Because of this lack of conclusive evidence, it is still a hypothesis rather than a theory.
There are lots of studies which have tried find correlations between schizophrenia and a variety of factors. One problem with this is that they often look exclusively at schizophrenic patients, and work backwards from there. There was one study that found that a large number of schizophrenic people had mothers who were infected with flu during pregnancy. However, they were not able to show any evidence that the number of mothers infected with influenza was any different from the rest of the population [1] However, there have been some convincing articles which have shown that in years with epidemic influenza, there has been an increase in schizophrenia incidence [2]. However, it could be that the stress induced by the pandemic itself could cause this, and there are flaws to the methodology which have not been adequately been addressed. [3]
The most strongest factor at the moment i.e. the one you should worry about the most is genetics. it is possible to screen people genetically, and give them a probability telling them how likely they are to get schizophrenia.
But this does not explain everything. There are still people who get schizophrenia without having these genes, and there are people who have these genes that don't. It is possible that infection could explain this, but it's still only a hypothesis at the moment, and one of many [4][5][6][7].
The fact that schizophrenia is such a hard to define disorder is not helping either. It is possible that it is an umbrella term for a number of disorders which show the same symptoms. it is likely that there are distinctly different diseases , like "Genetically Induced Schizophrenia" , "Stress Induced Schizophrenia" , "Perinatal Infection-Induced Schizophrenia" or "Genetically, Perinatal Infection and Stress induced Schizophrenia", which can interract with eachother to make schizophrenia development more likely.
Because of this, it is unlikely that there will be any definate cure for everybody, as people who have schizophrenia often have it as a result of different factors.
However, this is not a problem for Big Pharmaceutical companies, because they prefer to treat symptoms rather than create cures. ("if you cure someone, they won't come back for another prescription")
And to be honest, this is the only appropriate way to control schizophrenia until we actually can determine the root causes.
Should we panic about Influenza causing schizophrenia?
No, not yet. At the moment there is is a much greater level of evidence showing that genetics correlate better to schizophrenia [8]. The evidence that anxiety during pregnancy can cause schizophrenia in children is also higher. So panicking itself would cause things to worsen. If there are any pregant women reading this blog, I have just increased their chances of giving birth to someone who will be schizophrenic in later life [9]. Read that again if it doesn't scare you.
Okay, i'm being overdramatic here, but you should get my point. You should not panic about this. But don't take my word for it. I have supplied a long list of references, and it is likely that I have missed out some important points.If you can find the time read through them yourself, and make up your own mind.
References
[1]Exposure to Influenza in the Womb May Increase Risk of Schizophrenia by Amanda Barrett, MA @ http://www.swedish.org/19559.cfm
[2] SCHIZOPHRENIA AFTER PRENATAL EXPOSURE TO 1957 A2-INFLUENZA EPIDEMIC by OCALLAGHAN E, SHAM P, TAKEI N, GLOVER G, MURRAY RM in LANCET Volume: 337 Issue: 8752 Pages: 1248-1250 Published: MAY 25 1991
[3] "On the plausibility of ''The neurodevelopmental hypothesis'' of schizophrenia" by Weinberger DR in NEUROPSYCHOPHARMACOLOGY Volume: 14 Issue: 3 Pages: S1-S11 Supplement: Suppl. S Published: MAR 1996
[4] "Maternal household crowding during pregnancy and the offspring's risk of schizophrenia" by Kimhy D (Kimhy, David), Harlap S (Harlap, Susan), Fennig S (Fennig, Shmuel), Deutsch L (Deutsch, Lisa), Draiman BG (Draiman, Benjamin G.), Corcoran C (Corcoran, Cheryl), Goetz D (Goetz, Deborah), Nahon D (Nahon, Daniella), Malaspina D (Malaspina, Dolores) in Schizophrenia Research Volume: 86 Issue: 1-3 Pages: 23-29 Published: SEP 2006
[5] "Season of birth and schizophrenia in Northeast Brazil - Relationship to rainfall" by Messias E (Messias, Erick), Mourao C (Mourao, Carine), Maia J (Maia, Juliana), Campos JPM (Campos, Joao Paulo Mendes), Ribeiro K (Ribeiro, Kersia), Ribeiro L (Ribeiro, Luciana), Kirkpatrick B (Kirkpatrick, Brian) in JOURNAL OF NERVOUS AND MENTAL DISEASE Volume: 194 Issue: 11 Pages: 870-873 Published: NOV 2006
[6] "Schizophrenia-proneness, season of birth and sleep: Elevated schizotypy scores are associated with spring births and extremes of sleep" by ): Reid HM (Reid, Howard M.), Zborowski MJ (Zborowski, Michael J.) in PERSONALITY AND INDIVIDUAL DIFFERENCES Volume: 41 Issue: 7 Pages: 1185-1193 Published: NOV 2006
[7] "Biological hypotheses of schizophrenia: Possible influences of immunology and endocrinology" by Sperner-Unterweger B in FORTSCHRITTE DER NEUROLOGIE PSYCHIATRIE Volume: 73 Pages: S38-S43 Supplement: Suppl. 1 Published: NOV 2005
[8] "Linkage of a neurophysiological deficit in schizophrenia to a chromosome 15 locus" by Freedman R, Coon H, MylesWorsley M, OrrUrtreger A, Olincy A, Davis A, Polymeropoulos M, Holik J, Hopkins J, Hoff M, Rosenthal J, Waldo MC, Reimherr F, Wender P, Yaw J, Young DA, Breese CR, Adams C, Patterson D, Adler LE, Kruglyak L, Leonard S, Byerley W in PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Volume: 94 Issue: 2 Pages: 587-592 Published: JAN 21 1997
[9] "Higher risk of offspring schizophrenia following antenatal maternal exposure to severe adverse life events" by Khashan AS (Khashan, Ali S.), Abel KM (Abel, Kathryn M.), McNamee R (McNamee, Roseanne), Pedersen MG (Pedersen, Marianne G.), Webb RT (Webb, Roger T.), Baker PN (Baker, Philip N.), Kenny LC (Kenny, Louise C.), Mortensen PB (Mortensen, Preben Bo) in ARCHIVES OF GENERAL PSYCHIATRY Volume: 65 Issue: 2 Pages: 146-152 Published: FEB 2008
[10] "Schizophrenia and phenotypic plasticity: Schizophrenia may represent a predictive, adaptive response to severe environmental adversity that allows both bioenergetic thrift and a defensive behavioral strategy" by Reser, Jared E in MEDICAL HYPOTHESES Volume: 69 Issue: 2 Pages: 383-394 Published: 2007
[11] "Prenatal glucocorticoids and long-term programming" in EUROPEAN JOURNAL OF ENDOCRINOLOGY Volume: 151 Pages: U49-U62 Supplement: Suppl. 3 Published: NOV 2004
Thursday, 17 January 2008
Hearts without cells? What is this Madness?
Nature medicine has (or is about to, I can never really tell with Advanced online publishing) come out with the news that a group of scientists have made a breakthrough in regenerative heart medicine
What they have done (in simple terms) is take out the heart of a dead rat, removed all the cells, leaving this ghostly shadow of an organ, and then added a fresh batch of stem cells to the mix, thus creating (as if by magic) a new heart.
However, it’s a more complicated than that (otherwise we could all do it in our backyard sheds) and I’ll try to explain it as best as I can.
What this new finding represents is a new step in developing stem cells for curing heart disorders.
One of the main causes of death in the UK is Heart disease. This “disease” in itself is usually a conglomeration of various different disorders, which are caused by defects in the cells of the heart, or in the vasculature.
What is Heart Disease ?
Cardiomyopathy- Your heart is basically a muscle designed to pump blood around your body. All of the heart cells are essentially muscle cells, each containing a series of muscle fibres (Actin and Myosin), which tug on each other to create a contraction. Cardiomyopathy is a disease where these muscle cells die off, reducing the contractile strength of the heart muscles, and their ability to conduct contraction to the rest of the heart. This disease can lead to arrhythmias, and sudden cardiac death. There are many different cardiomyopathies, which can be caused by environmental factors (restriction in blood flow, immune reactions, drugs) or by genetic factors.
Cardiovascular disease: This is generally caused by any blockage of blood vessels supplying the heart. This can lead to some parts of the heart being oxygen starved, and dying off, which can lead to cardiomyopathy.
Coronary Heart Disease: this is usually caused by a build up of plaques within blood vessel that supply the heart. This disease can cause Angina, and heart attacks.
Hypertensive Heart disease: this is caused by a high blood pressure. This can cause increased growth of the left side of the heart as the muscle tries to cope with the pressure (Left side hypertrophy), death of cells ( Hypertensive cardiomyopathy) and cardiac arrhythmias.
Valvular heart disease: This sort of disease shows up as a heart murmur. These effect the pumping ability of the heart, and can have a number of causes , ranging from the genetic, to the immunological. These can lead to angina, hypertrophy of the heart muscles. The symptoms depend on which valves in the heart are damaged.
Inflammatory Heart Disease: this is where an immune response causes the heart walls to swell up, which can block heart valves. Also, if the muscle is affected, it can lead to a cadiomyopathy, and leads to rapid signs of heart failure, and sudden death.
Heart Failure: This is a catastrophic failure of the heart to fill up with blood, or pump it out of the body, and can result from a variety of disorders, such as the ones described above.
The main problems people get with their heart stem from the death of cardiomyocytes (the heart muscle cells). The heart is not very good at regenerating itself after these cells die off [3]. Often, the heart will simply develop scar tissue, which covers the area where cells have died, but does not replace their vital function. So after you have one heart problem, you will have more and more.
Stem Cells to the Rescue !!
Many of these diseases can be treated with drugs or minor surgery. If there is a blockage of some of the blood vessels, heart bypass surgery can be used to allow the reperfusion of the blood to the heart.
When someone is in the terminal stages of heart failure, when there is widespread cardiomyopathy, the only way to effectively save their lives is to give them a heart transplant. This in itself has a lot of problems. Firstly, you need to find a heart with matching tissue type. This can be quite difficult, as not many people allow themselves to be organ donors (unless Gordon Brown gets his way) and most people who die generally don’t die with perfectly preserved hearts.
So other ways have been sought out to replenish the levels of cardiomyocytes within the heart, in order to reverse previous damage. Research into this field has been going on for over ten years.
In the first attempts, people attempted to graft skeletal muscle cells onto the heart, as heart muscle and skeletal muscle are in many ways similar. They used myoblasts, which are a form of stem cells which are present in the muscle, and whenever damage occurs to muscle, they grow and repair the damage.
The only problem with this method is that while in many ways, skeletal muscle is similar to heart muscle, in many other ways it is quite dissimilar. Heart muscle cells have to perform two main functions. They have to respond to electrical stimulation produced by the pacemaker cells of the heart (usually found in the sino-atrial node and the atrio-ventricular node of the heart) by contracting. Skeletal muscles can perform this function quite well, as skeletal muscles have to respond to electrical signals (provided by the nerves connected to the muscles via the neuromuscular junction)
However, cardiomyocytes also need to conduct the electrical signals to their adjacent cells via gap junctions. Skeletal muscles are one of the few cell types that cannot form these junctions, and so cannot conduct electrical stimulation. [2] However, the therapeutic effect of using these cells was indisputable, and clinical trials were carried out in the year 2000.
Ideally, the right cells to use would be cardiomyocytes. However, the Adult stem cells for cardiomyocytes have been difficult to find. Foetal stem cells for the heart have been isolated, and they are able to implant into the hosts heart with little or no trouble [1]. Later experiments showed that foetal cardiomyocytes are perfectly capable of repairing damage inflicted upon the heart [3]
However, the degree of repair that these cells can perform is limited by the massive amounts of necrosis that they encounter when they reach the heart. When necrosis occurs, lots of toxic substances are released, and these can cause a lot of problems for growing stem cells.
At the end of the 20th Century, scientists were beginning to experiment with embryonic stem cells, in order to obtain a new source of cardiomyocytes.
But even more recently, things have taken a strange turn, in that an adult stem cell line, known as mesenchymal stem cells, have shown themselves to be able to differentiate into a whole variety of cells, including cardiomyocytes. I have already waxed lyrical on these cells in a previous post.
There have been trials of mesenchymal stem cells that have showed that as a cell based therapy, these cells can elicit some improvement in patients [4]. However, it should be noted that in studies in Doberman dogs (which have a natural predisposition to heart failure) the administration of mesenchymal stem cells triggered lots of small micro infarctions. So far nothing of this sort has been observed in humans or rats, but it is something to keep an eye out for.
Stem cells in general can help regenerate some of the heart’s function. However, in the case of heart failure, where large portions of the heart are no longer functional, it is nearly impossible to get enough cells to the right location and in high enough concentration to get an effective response.
Because of this problem, research has been done into taking these stem cells, and putting them together so that you can grow a patch of heart muscle which can then be grafted onto an organ. This will work a lot like transplantation, but the stem cells will have to be taken from the individual with the problem, thus avoiding any graft vs. host complications. The dream pursued by people performing this sort of research is that they would some day be able to create an artificial heart to replace the old one.
However, this sort of tissue engineering is harder than it would first appear.
How would you go about growing heart muscle in the lab ?
One of the main problems with doing this is that heart muscle is a complicated tissue, and the heart itself is not a simple tissue. The heart has many different types of cells , which are organised in a specific way. The pericardium has to be on the outside of the heart, to minimise friction with the lungs when it beats. The myocardium has to be thick, and also be well vascularised, to allow the flow of blood into it. Not to mention the different electrophysiological properties of the heart which need to be replicated in order to a regular rhythmic beating motion. You will need to make sure that purkinje cells segregate into the septum of the heart, and that the cells in the atrium don’t beat at the same time as the ventricles (that would bring the heart close to exploding).
This science has quite long roots in the past; the first attempts at growing isolated heart tissue had begun in the 1950’s. These experiments used chick embryo’s to generate artificial heart tissue [5]. After 18 hours in a bioreactor, Moscona found that the embryonic heart cells arranged themselves into a structure similar to that found in the heart. They even had a similar functionality. Cardiomyocytes had a compulsion to aggregate and form tissue, and what’s more this tissue could be observed to start beating rhythmically.
This finding was later expanded upon in the 1980’s, when researchers decided to grow these cardiomyocytes on a collagen membrane. The cardiomyocytes in a normal cell are bound by the extracellular matrix, which provides them with a solid surface to attach to so that they can contract. This matrix is made up mostly of a long stringy molecule known as collagen. When researchers grew their cardiomyocytes on the collagen gel, they found that these cells began more differentiated, and more heart-like.
In later experiments, it was found that the cardiac muscle cells aligned themselves according to the direction of the collagen molecule.
The efficiency of these tissue grafts is dependant on the type of scaffold they are grown on. This scaffold has to be constructed along the lines of the target organ. The tissue you generate has to be as similar as possible.
However, there is a limit to how big a tissue you can make. Heart tissue needs to be heavily vascularised, in order that the cardiomyocytes all get enough oxygen to survive. However, in the lab it is quite difficult to produce tissue with vascular cells within it that can conduct blood, because you will need to link them to the systemic circulation, which is quite difficult. Because of this, there is a critical size for tissue grafts, which is defined by the ability of oxygen to diffuse through that particular tissue.
In order to combat this, there is some research going into impregnating the scaffolds upon which these tissues are built with angiogenic factors within them, so that when the tissue is implanted, blood vessel naturally grow into it, and fill up all the layers with blood. Another technique is to input the cells which will later develop into blood vessels into the construct, in the hope that they will mature into blood vessels.
So where does the De-Cellularised heart fit into this ?
Sometimes, it’s best to go back to nature and see how evolution solved the problem that we are trying to tackle. Instead of trying to construct complex collagen gels impregnated with all sorts of nutrient factors, why not go and see how the actual heart solves this problem?
This was what a group at the University of Minnesota decided to find out [7]. So they decided to do something quite ambitious and remove all the cells from a rat heart, and see what was left over.
They did these using a series of different detergent solutions. Not like fairy liquid, I mean proper detergents, a chemical detergent is designed to mix itself with lipids, but still have an end poking out which is attracted to water. They took the heart out of a dead rat, and then flushed PBS (to clean out the cells) and then SDS detergent under pressure for 12 hours. At the end of this, all of the cells ended up getting washed off of the heart, in theory leaving only the extracellular matrix scaffolds that make up the heart. In order to check that they got rid of all the cells, they looked at the histology of their “ghost hearts” (I’m always slightly sceptical of histological evidence, because what it involves is looking under a microscope at the tissue. It’s easy for even the best scientists to miss something).
But anyway, they looked at a variety of ways to make sure that no cells from the original host were left, and found that they were all gone.
So now they have a de-cellularised heart. What next? What was the point?
Now they have a fantastic scaffold upon which they can build a “new” heart. It should be the ideal scaffold, because it is this structure which tissue engineers have been spending a lot of time trying to mimic, so it should be a good scaffold.
What they did next was stick on foetal cardiomyocytes onto this scaffold.
Before doing this, the heart had to be perfused with the right nutrient medium at the right temperature, and the right pressure, before you could introduce your first cells. These cells then began growing, and 8 days after the cells were injected, the hearts became responsive to electrical stimulation, showing that the cells had grown and re-populated the heart.
Then, endothelial cells were injected (these are the cells that develop into blood vessels) to hopefully improve the growth of cells within the heart. However, the cellularisation was not evenly distributed, it was found to be the best at points where the cells were injected.
So what does this new piece of research leave us with ?
The important thing here is that for the first time, we are now able to look at how the extracellular matrix of the heart is arranged in a clear way. The structure of this natural scaffold will be incredibly for the tissue engineers trying to mimic it. So in this respect it is quite important.
The fact that they were able to re-cellularise the heart is also a big step. This leaves a new gateway open for the organ transplant. Most individuals in the population don’t have the same tissue type. This experiment could potentially show another way for organ transplants to work. Instead of just transplanting the heart from a cadaver, what could be done is the donor heart could be de-cellularised and re-populated with stem cells from the recipient, to create a heart tissue with no tissue incompatibility problems.
However, I would not start goring a huge amount of hamburgers yet, because just because they could do this in rats does not mean that it’s possible in humans.
For a start , a rat heart is really small. Much smaller than a human heart. It’s also not just a smaller version of the human heart either. If the human heart was shrunk to the size of a rat’s, it would still have thicker walls.
The method that was used to de-cellularise these cells is very dependant on size and pressure. If you were to do the same treatment with a human, you would need the put the detergent through it at a higher pressure, and you will have to do it for a lot longer. The human heart has much more cells than a rat’s heart, and to get rid of all the cells would take a lot of time. The risk of using higher pressures and taking more time over this experiment is that there is no guarantee that changing these will not severely alter the structure of the structure of the collagen.
Rat hearts are generally quite different from humans, and even rat cells are very different. The rat heart beats at 300bpm, the electrochemical coupling of these cells is also quite different, and the force frequency relationship between heartbeats is negative (whereas in humans, this relationship is positive). So looking at the structure of the cellular matrix of the rat may be useful, but because of these intrinsic differences between rats and humans, I would not say that the problems of tissue engineering the heart are all solved.
Ideally, this experiment should be replicated in animals which are more similar to humans, such as pigs, or even sheep. But even then, I wouldn’t start celebrating until they had a viable heart transplant with these re-cellularized hearts, and we are a way off that yet.
However, this experiment has opened up a whole new area of research, and I suspect we will see more experiments with de-cellularized hearts popping up next year. Not many, because it is still quite an expensive procedure, which requires a lot of time as well.
1. Soonpaa MH, Koh GY, Klug MG, Field LJ: Formation of nascent intercalated disks between grafted fetal cardiomyocytes and host myocardium. Science 1994, 264(5155):98-101.
2. Scorsin M, Hagege A, Vilquin J-T, Fiszman M, Marotte F, Samuel J-L, Rappaport L, Schwartz K, Menasche P: COMPARISON OF THE EFFECTS OF FETAL CARDIOMYOCYTE AND SKELETAL MYOBLAST TRANSPLANTATION ON POSTINFARCTION LEFT VENTRICULAR FUNCTION. J Thorac Cardiovasc Surg 2000, 119(6):1169-1175.
3. Caspi O, Gepstein L: Stem cells for myocardial repair. Eur Heart J Suppl 2006, 8(suppl_E):E43-54.
4. Chen SL: Effect on left ventricular function of intracoronary transplantation of autologous bone marrow mesenchymal stem cell in patients with acute myocardial infarction. The American journal of cardiology 2004, 94(1):92-95.
5. Moscona A, Moscona H. The dissociation and aggregation of cells from organ rudiments of the early chick embryo. J Anat. 1952; 86: 287–301
6. Leor J, Aboulafia-Etzion S, Dar A, Shapiro L, Barbash IM, Battler A, Granot Y, Cohen S Bioengineered cardiac grafts:A new approach to repair the infarcted myocardium? Circulation. 2000; 102: III56–61.
7. Ott HC, Matthiesen TS, Goh S-K, Black LD, Kren SM, Netoff TI, Taylor DA: Perfusion-decellularized matrix: using nature's platform to engineer a bioartificial heart. Nat Med 2008, advanced online publication.
What they have done (in simple terms) is take out the heart of a dead rat, removed all the cells, leaving this ghostly shadow of an organ, and then added a fresh batch of stem cells to the mix, thus creating (as if by magic) a new heart.
However, it’s a more complicated than that (otherwise we could all do it in our backyard sheds) and I’ll try to explain it as best as I can.
What this new finding represents is a new step in developing stem cells for curing heart disorders.
One of the main causes of death in the UK is Heart disease. This “disease” in itself is usually a conglomeration of various different disorders, which are caused by defects in the cells of the heart, or in the vasculature.
What is Heart Disease ?
Cardiomyopathy- Your heart is basically a muscle designed to pump blood around your body. All of the heart cells are essentially muscle cells, each containing a series of muscle fibres (Actin and Myosin), which tug on each other to create a contraction. Cardiomyopathy is a disease where these muscle cells die off, reducing the contractile strength of the heart muscles, and their ability to conduct contraction to the rest of the heart. This disease can lead to arrhythmias, and sudden cardiac death. There are many different cardiomyopathies, which can be caused by environmental factors (restriction in blood flow, immune reactions, drugs) or by genetic factors.
Cardiovascular disease: This is generally caused by any blockage of blood vessels supplying the heart. This can lead to some parts of the heart being oxygen starved, and dying off, which can lead to cardiomyopathy.
Coronary Heart Disease: this is usually caused by a build up of plaques within blood vessel that supply the heart. This disease can cause Angina, and heart attacks.
Hypertensive Heart disease: this is caused by a high blood pressure. This can cause increased growth of the left side of the heart as the muscle tries to cope with the pressure (Left side hypertrophy), death of cells ( Hypertensive cardiomyopathy) and cardiac arrhythmias.
Valvular heart disease: This sort of disease shows up as a heart murmur. These effect the pumping ability of the heart, and can have a number of causes , ranging from the genetic, to the immunological. These can lead to angina, hypertrophy of the heart muscles. The symptoms depend on which valves in the heart are damaged.
Inflammatory Heart Disease: this is where an immune response causes the heart walls to swell up, which can block heart valves. Also, if the muscle is affected, it can lead to a cadiomyopathy, and leads to rapid signs of heart failure, and sudden death.
Heart Failure: This is a catastrophic failure of the heart to fill up with blood, or pump it out of the body, and can result from a variety of disorders, such as the ones described above.
The main problems people get with their heart stem from the death of cardiomyocytes (the heart muscle cells). The heart is not very good at regenerating itself after these cells die off [3]. Often, the heart will simply develop scar tissue, which covers the area where cells have died, but does not replace their vital function. So after you have one heart problem, you will have more and more.
Stem Cells to the Rescue !!
Many of these diseases can be treated with drugs or minor surgery. If there is a blockage of some of the blood vessels, heart bypass surgery can be used to allow the reperfusion of the blood to the heart.
When someone is in the terminal stages of heart failure, when there is widespread cardiomyopathy, the only way to effectively save their lives is to give them a heart transplant. This in itself has a lot of problems. Firstly, you need to find a heart with matching tissue type. This can be quite difficult, as not many people allow themselves to be organ donors (unless Gordon Brown gets his way) and most people who die generally don’t die with perfectly preserved hearts.
So other ways have been sought out to replenish the levels of cardiomyocytes within the heart, in order to reverse previous damage. Research into this field has been going on for over ten years.
In the first attempts, people attempted to graft skeletal muscle cells onto the heart, as heart muscle and skeletal muscle are in many ways similar. They used myoblasts, which are a form of stem cells which are present in the muscle, and whenever damage occurs to muscle, they grow and repair the damage.
The only problem with this method is that while in many ways, skeletal muscle is similar to heart muscle, in many other ways it is quite dissimilar. Heart muscle cells have to perform two main functions. They have to respond to electrical stimulation produced by the pacemaker cells of the heart (usually found in the sino-atrial node and the atrio-ventricular node of the heart) by contracting. Skeletal muscles can perform this function quite well, as skeletal muscles have to respond to electrical signals (provided by the nerves connected to the muscles via the neuromuscular junction)
However, cardiomyocytes also need to conduct the electrical signals to their adjacent cells via gap junctions. Skeletal muscles are one of the few cell types that cannot form these junctions, and so cannot conduct electrical stimulation. [2] However, the therapeutic effect of using these cells was indisputable, and clinical trials were carried out in the year 2000.
Ideally, the right cells to use would be cardiomyocytes. However, the Adult stem cells for cardiomyocytes have been difficult to find. Foetal stem cells for the heart have been isolated, and they are able to implant into the hosts heart with little or no trouble [1]. Later experiments showed that foetal cardiomyocytes are perfectly capable of repairing damage inflicted upon the heart [3]
However, the degree of repair that these cells can perform is limited by the massive amounts of necrosis that they encounter when they reach the heart. When necrosis occurs, lots of toxic substances are released, and these can cause a lot of problems for growing stem cells.
At the end of the 20th Century, scientists were beginning to experiment with embryonic stem cells, in order to obtain a new source of cardiomyocytes.
But even more recently, things have taken a strange turn, in that an adult stem cell line, known as mesenchymal stem cells, have shown themselves to be able to differentiate into a whole variety of cells, including cardiomyocytes. I have already waxed lyrical on these cells in a previous post.
There have been trials of mesenchymal stem cells that have showed that as a cell based therapy, these cells can elicit some improvement in patients [4]. However, it should be noted that in studies in Doberman dogs (which have a natural predisposition to heart failure) the administration of mesenchymal stem cells triggered lots of small micro infarctions. So far nothing of this sort has been observed in humans or rats, but it is something to keep an eye out for.
Stem cells in general can help regenerate some of the heart’s function. However, in the case of heart failure, where large portions of the heart are no longer functional, it is nearly impossible to get enough cells to the right location and in high enough concentration to get an effective response.
Because of this problem, research has been done into taking these stem cells, and putting them together so that you can grow a patch of heart muscle which can then be grafted onto an organ. This will work a lot like transplantation, but the stem cells will have to be taken from the individual with the problem, thus avoiding any graft vs. host complications. The dream pursued by people performing this sort of research is that they would some day be able to create an artificial heart to replace the old one.
However, this sort of tissue engineering is harder than it would first appear.
How would you go about growing heart muscle in the lab ?
One of the main problems with doing this is that heart muscle is a complicated tissue, and the heart itself is not a simple tissue. The heart has many different types of cells , which are organised in a specific way. The pericardium has to be on the outside of the heart, to minimise friction with the lungs when it beats. The myocardium has to be thick, and also be well vascularised, to allow the flow of blood into it. Not to mention the different electrophysiological properties of the heart which need to be replicated in order to a regular rhythmic beating motion. You will need to make sure that purkinje cells segregate into the septum of the heart, and that the cells in the atrium don’t beat at the same time as the ventricles (that would bring the heart close to exploding).
This science has quite long roots in the past; the first attempts at growing isolated heart tissue had begun in the 1950’s. These experiments used chick embryo’s to generate artificial heart tissue [5]. After 18 hours in a bioreactor, Moscona found that the embryonic heart cells arranged themselves into a structure similar to that found in the heart. They even had a similar functionality. Cardiomyocytes had a compulsion to aggregate and form tissue, and what’s more this tissue could be observed to start beating rhythmically.
This finding was later expanded upon in the 1980’s, when researchers decided to grow these cardiomyocytes on a collagen membrane. The cardiomyocytes in a normal cell are bound by the extracellular matrix, which provides them with a solid surface to attach to so that they can contract. This matrix is made up mostly of a long stringy molecule known as collagen. When researchers grew their cardiomyocytes on the collagen gel, they found that these cells began more differentiated, and more heart-like.
In later experiments, it was found that the cardiac muscle cells aligned themselves according to the direction of the collagen molecule.
The efficiency of these tissue grafts is dependant on the type of scaffold they are grown on. This scaffold has to be constructed along the lines of the target organ. The tissue you generate has to be as similar as possible.
However, there is a limit to how big a tissue you can make. Heart tissue needs to be heavily vascularised, in order that the cardiomyocytes all get enough oxygen to survive. However, in the lab it is quite difficult to produce tissue with vascular cells within it that can conduct blood, because you will need to link them to the systemic circulation, which is quite difficult. Because of this, there is a critical size for tissue grafts, which is defined by the ability of oxygen to diffuse through that particular tissue.
In order to combat this, there is some research going into impregnating the scaffolds upon which these tissues are built with angiogenic factors within them, so that when the tissue is implanted, blood vessel naturally grow into it, and fill up all the layers with blood. Another technique is to input the cells which will later develop into blood vessels into the construct, in the hope that they will mature into blood vessels.
So where does the De-Cellularised heart fit into this ?
Sometimes, it’s best to go back to nature and see how evolution solved the problem that we are trying to tackle. Instead of trying to construct complex collagen gels impregnated with all sorts of nutrient factors, why not go and see how the actual heart solves this problem?
This was what a group at the University of Minnesota decided to find out [7]. So they decided to do something quite ambitious and remove all the cells from a rat heart, and see what was left over.
They did these using a series of different detergent solutions. Not like fairy liquid, I mean proper detergents, a chemical detergent is designed to mix itself with lipids, but still have an end poking out which is attracted to water. They took the heart out of a dead rat, and then flushed PBS (to clean out the cells) and then SDS detergent under pressure for 12 hours. At the end of this, all of the cells ended up getting washed off of the heart, in theory leaving only the extracellular matrix scaffolds that make up the heart. In order to check that they got rid of all the cells, they looked at the histology of their “ghost hearts” (I’m always slightly sceptical of histological evidence, because what it involves is looking under a microscope at the tissue. It’s easy for even the best scientists to miss something).
But anyway, they looked at a variety of ways to make sure that no cells from the original host were left, and found that they were all gone.
So now they have a de-cellularised heart. What next? What was the point?
Now they have a fantastic scaffold upon which they can build a “new” heart. It should be the ideal scaffold, because it is this structure which tissue engineers have been spending a lot of time trying to mimic, so it should be a good scaffold.
What they did next was stick on foetal cardiomyocytes onto this scaffold.
Before doing this, the heart had to be perfused with the right nutrient medium at the right temperature, and the right pressure, before you could introduce your first cells. These cells then began growing, and 8 days after the cells were injected, the hearts became responsive to electrical stimulation, showing that the cells had grown and re-populated the heart.
Then, endothelial cells were injected (these are the cells that develop into blood vessels) to hopefully improve the growth of cells within the heart. However, the cellularisation was not evenly distributed, it was found to be the best at points where the cells were injected.
So what does this new piece of research leave us with ?
The important thing here is that for the first time, we are now able to look at how the extracellular matrix of the heart is arranged in a clear way. The structure of this natural scaffold will be incredibly for the tissue engineers trying to mimic it. So in this respect it is quite important.
The fact that they were able to re-cellularise the heart is also a big step. This leaves a new gateway open for the organ transplant. Most individuals in the population don’t have the same tissue type. This experiment could potentially show another way for organ transplants to work. Instead of just transplanting the heart from a cadaver, what could be done is the donor heart could be de-cellularised and re-populated with stem cells from the recipient, to create a heart tissue with no tissue incompatibility problems.
However, I would not start goring a huge amount of hamburgers yet, because just because they could do this in rats does not mean that it’s possible in humans.
For a start , a rat heart is really small. Much smaller than a human heart. It’s also not just a smaller version of the human heart either. If the human heart was shrunk to the size of a rat’s, it would still have thicker walls.
The method that was used to de-cellularise these cells is very dependant on size and pressure. If you were to do the same treatment with a human, you would need the put the detergent through it at a higher pressure, and you will have to do it for a lot longer. The human heart has much more cells than a rat’s heart, and to get rid of all the cells would take a lot of time. The risk of using higher pressures and taking more time over this experiment is that there is no guarantee that changing these will not severely alter the structure of the structure of the collagen.
Rat hearts are generally quite different from humans, and even rat cells are very different. The rat heart beats at 300bpm, the electrochemical coupling of these cells is also quite different, and the force frequency relationship between heartbeats is negative (whereas in humans, this relationship is positive). So looking at the structure of the cellular matrix of the rat may be useful, but because of these intrinsic differences between rats and humans, I would not say that the problems of tissue engineering the heart are all solved.
Ideally, this experiment should be replicated in animals which are more similar to humans, such as pigs, or even sheep. But even then, I wouldn’t start celebrating until they had a viable heart transplant with these re-cellularized hearts, and we are a way off that yet.
However, this experiment has opened up a whole new area of research, and I suspect we will see more experiments with de-cellularized hearts popping up next year. Not many, because it is still quite an expensive procedure, which requires a lot of time as well.
1. Soonpaa MH, Koh GY, Klug MG, Field LJ: Formation of nascent intercalated disks between grafted fetal cardiomyocytes and host myocardium. Science 1994, 264(5155):98-101.
2. Scorsin M, Hagege A, Vilquin J-T, Fiszman M, Marotte F, Samuel J-L, Rappaport L, Schwartz K, Menasche P: COMPARISON OF THE EFFECTS OF FETAL CARDIOMYOCYTE AND SKELETAL MYOBLAST TRANSPLANTATION ON POSTINFARCTION LEFT VENTRICULAR FUNCTION. J Thorac Cardiovasc Surg 2000, 119(6):1169-1175.
3. Caspi O, Gepstein L: Stem cells for myocardial repair. Eur Heart J Suppl 2006, 8(suppl_E):E43-54.
4. Chen SL: Effect on left ventricular function of intracoronary transplantation of autologous bone marrow mesenchymal stem cell in patients with acute myocardial infarction. The American journal of cardiology 2004, 94(1):92-95.
5. Moscona A, Moscona H. The dissociation and aggregation of cells from organ rudiments of the early chick embryo. J Anat. 1952; 86: 287–301
6. Leor J, Aboulafia-Etzion S, Dar A, Shapiro L, Barbash IM, Battler A, Granot Y, Cohen S Bioengineered cardiac grafts:A new approach to repair the infarcted myocardium? Circulation. 2000; 102: III56–61.
7. Ott HC, Matthiesen TS, Goh S-K, Black LD, Kren SM, Netoff TI, Taylor DA: Perfusion-decellularized matrix: using nature's platform to engineer a bioartificial heart. Nat Med 2008, advanced online publication.
Monday, 7 January 2008
Focus on Obesity
Okay, last night, I saw a programme, called the Half ton mum (oh my f#cking god I linked to the daily mail... how much lower can this blog get?)
It was about an extremely fat woman, although she wasn't half a ton (more like 70 stone..... The combined weight of me and my family isn't that much)
but anyway, this documentary left me with the indelible question in my mind. How can someone let themselves get so fat that they cannot walk? or in her case, it got to the point where she literally couldn't move. She had weeping sores (which she never saw) and if she tried to roll over or move her legs, her skin would rip apart. And I'm not even going to start on the bedsores.
She had been stuck in her house for the past five years. I tend to go a bit crazy if I've been in the house for five days, so I cannot imagine the hell this woman was exposed to.
Not to mention that this documentary was helpfully followed by another, called "half ton man" this was about a man, who was actually half a ton in size.
Why Do People Become Obese ?
There is a very simple answer to this question. They eat a lot. According to a nutritional biochemist I know, An average human male has a recommended daily allowance of 2500 calories per day, and the average female requires 2100 on average.
However, these are rough estimates, and they depend on your activity level.
If i was stuck at a desk all day, I only need 2000 calories to survive. If I live an active athletic life, I may need as much as 3500, so actually following recommended daily caloric intake may not be the best guide. You can calculate your recommended daily caloric intake at this website (although I cannot vouch for whether it's trustworthy or not , because I never use it to look at how much I need to eat)
What I do is similar to what most people do. I trust my brain to tell me how much I'm supposed to eat. When most people eat, they become full after they've fulfilled their calorie needs, and stop eating. Some people don't eat much, and some people eat more, but their weight stays stable, because they fulfil their particular requirements.
This is what happens in animals, which is why you don't see fat foxes toddling around city streets, event though there is an abundance of food waste in the city. The same goes for rats.
However, these days there are a lot more people who seem to be ignoring their brain, or at least have stopped being able to tell (by natural means) when they have fulfilled their daily caloric requirement. these people eat more and more calories, and become overweight, then fat, then obese and (if they haven't died of a heart attack, diabetes or cancer by now) then super-obese.
The question we should be really asking is why are these people eating more, and putting on more weight?
Why Do People Over-Eat ?
Scientists have been trying to solve this particular problem for a while, and there are two factors which are believed to contribute to obesity:
It was about an extremely fat woman, although she wasn't half a ton (more like 70 stone..... The combined weight of me and my family isn't that much)
but anyway, this documentary left me with the indelible question in my mind. How can someone let themselves get so fat that they cannot walk? or in her case, it got to the point where she literally couldn't move. She had weeping sores (which she never saw) and if she tried to roll over or move her legs, her skin would rip apart. And I'm not even going to start on the bedsores.
She had been stuck in her house for the past five years. I tend to go a bit crazy if I've been in the house for five days, so I cannot imagine the hell this woman was exposed to.
Not to mention that this documentary was helpfully followed by another, called "half ton man" this was about a man, who was actually half a ton in size.
Why Do People Become Obese ?
There is a very simple answer to this question. They eat a lot. According to a nutritional biochemist I know, An average human male has a recommended daily allowance of 2500 calories per day, and the average female requires 2100 on average.
However, these are rough estimates, and they depend on your activity level.
If i was stuck at a desk all day, I only need 2000 calories to survive. If I live an active athletic life, I may need as much as 3500, so actually following recommended daily caloric intake may not be the best guide. You can calculate your recommended daily caloric intake at this website (although I cannot vouch for whether it's trustworthy or not , because I never use it to look at how much I need to eat)
What I do is similar to what most people do. I trust my brain to tell me how much I'm supposed to eat. When most people eat, they become full after they've fulfilled their calorie needs, and stop eating. Some people don't eat much, and some people eat more, but their weight stays stable, because they fulfil their particular requirements.
This is what happens in animals, which is why you don't see fat foxes toddling around city streets, event though there is an abundance of food waste in the city. The same goes for rats.
However, these days there are a lot more people who seem to be ignoring their brain, or at least have stopped being able to tell (by natural means) when they have fulfilled their daily caloric requirement. these people eat more and more calories, and become overweight, then fat, then obese and (if they haven't died of a heart attack, diabetes or cancer by now) then super-obese.
The question we should be really asking is why are these people eating more, and putting on more weight?
Why Do People Over-Eat ?
Scientists have been trying to solve this particular problem for a while, and there are two factors which are believed to contribute to obesity:
- A genetic malfunction in the bodily systems which allow for the brain to regulate it's food intake.
- An environmentally induced malfunction in the body systems which control food intake.
The only way to discern how these factors are effected, the bodily systems involved with the regulation of food intake needed to be analysed and understood.
Since the late 19th century it has been believed that obesity was related to a problem in the hypothalamus. In those days, they didn't have the high fat food that we do today and so obesity was a much rarer condition. In Clinical literature of this time traced a correlation between obesity and tumours within the hypothalamus. Frolich and Babinski claimed that obesity was due to a malfunction in the pituitary gland (which was right next to the hypothalamus) while Erdhiem, on of their contemporaries believed it to have been due to a problem in the hypothalamus. [1] However, neither of these two groups were really sure about their theories. In order to test these theories, they had to use animal models. (I am not going to go into my opinions or the ethics of using animals for experimental use in this post. but I promise I will dedicate a post to this topic at a later date)
These models could not simply be animals that had been force fed food to make them fat. they had to have some sort of imbalance in their metabolism in order to make them want to become fat.
One of the first attempts to do this was in 1913, where Camus and Roussy performed a hypophysectomy on a dog (they lifted out it's hypothalamus) and showed that this did not in fact cause obesity unless the dog received brain damage at the same time. [1] The problem with this experiment was that it lacked repeatability, and therefore credibility.
It was only in 1939 when the role of the hypothalamus in the regulation of food intake could be confirmed, in an experiment performed by S.W. Ranson. In this experiment, an electrode was used to damage some sections of a rat hypothalamus, without touching the pituitary. This caused the experimental animals to become obese, proving that it was the hypothalamus, and not the pituitary which controlled obesity.
This is not to say that obesity is caused by damage to the hypothalamus, even 50 years ago, when they were doing these experiments they did not believe that. It was proposed by GC Kennedy in 1953 that in humans and animals, food intake is controlled by the adipostat mechanism [2].
Adipostat Mechanism
Adipo (meaning Fat) Stat (meaning stability)
Kennedy observed that rats keep their weight within certain limits. And they can do this even if you give them more exercise, or less exercise. they manipulate their food intake so that their body fat index remains constant [2]. This only fails to occur when rats have damage to their hypothalamus. Kennedy came to the conclusion that in order for this to occur, the brain must be able to detect the body fat levels of the mouse via the hypothalamus. In order to do this, the fat cells (when you get fat, the excess fat deposits in special cells called Adipocytes) themselves must be secreting a messenger molecule to tell the brain how fat the mouse has gotten. This is the Adipostat response.
Kennedy suggested that obesity was not caused by damage to the hypothalamus , but in fact was due to a fault in this adipostat response.
Obese Mice
Not long after the proposal of the adipostatic response, a new strain of mouse was found in laboratories, which grew incredibly fat. These were named the obese or ob/ob mice. These mice eat a lot of food, and they tend to eat until they literally cannot move. If you try to restrict their food for their own welfare, they will become incredibly aggressive. In fact , they behaved a lot like mice whom had experimental destruction of parts of their hypothalamus, except that these mice had perfectly healthy brains. So if the problem wasn't in the hypothalamus, these mice must have had a problem in their fat cells, in that they weren't secreting the messenger molecule telling the mouse's brain how fat the mouse had become.
How did the researchers test this?
Parabiotic Experiments
In hypothalamically damaged mice, there had been experiments in which the blood of these mice was shared with that of normal mice (there is not usually much problem with rejection in inbred laboratory mice)
These mice stayed fat, and the normal mice became thinner. This was because in the fat mice, the fat cells were producing messenger like mad, but since the hypothalamus was damaged, the fat mouse's brain could not detect the messenger. However, the normal mouse still had an intact hypothalamus, which reacted to the hormone stimulus, telling the mouse that it had too much fat. And so the normal mouse stopped eating, and became thinner.
However, when a normal mouse was strapped to the ob/ob mouse, it was the obese mouse which reduced it's food intake. So it had a functional hypothalamus, but the fat cells within the obese mouse did not function.
The molecular messenger however evaded identification for nearly 30 years, until in 1994. This peptide molecule was named leptin (from the greek Leptos meaning "thin") The ob/ob mouse strain was caused by a deficiency in the leptin producing genes.
By 1997, these genes were isolated, and moreover it was found that some human children also had a leptin deficiency[3], similar to that seen in ob/ob mice. These children exhibited rapid weight gain, and extreme hyperphagia (one child was observed to eat 3000 calories...in one sitting)
However, these children were treated with injections of leptin, and they were "cured" of their obesity. Leptin made them reduce their food intake, and they slimmed down to a healthy bodyweight.
Can we not cure all forms of obesity using Leptin treatment?
In theory, if we give leptin shots to all fat people, they should end up losing the weight that they've gained. However, this does not work in reality for two reasons:
- Leptin Deficiency is not the cause of all obesity. in fact, only about ten people in the world have been reported to have this disease
- Leptin was trialled as an anti-obesity drug. A clinical trial was done to investigate whether leptin could inhibit food intake in obese people [4]. What was found was quite disheartening to the drug company. the Leptin had no effect. Why? Because many people who become obese are resistant to the effects of leptin[5].
So while we are no closer to finding the cure for obesity, we do at least have a clue as to one of the factors which determines obesity. In the same way that in type 2 diabetes , you can become resistant to the effects of insulin, if you become too fat, you become resistant to the effects of leptin. This can go some way as to explaining how an ordinary fat person can progress to hyper-obesity without getting proper signals to the brain.
What causes Leptin Resistance?
In short, no-one knows for sure . A lot of scientists are trying to solve this problem at the moment. It is thought that Leptin resistance must originate in the hypothalamus. So how do researchers investigate this?
This is investigated through the use of diet induced obese mice. These mice are fed on a high fat diet, until they become quite fat. They aren't the perfect models of leptin resistance, because they don't become as fat as the Leptin deficient obese mouse strains I mentioned earlier. this means that these mice are still not completely resistant to leptin.
Their leptin resistance was measured through looking at how much P-STAT3 (a downstream signalling molecule affected by how successful leptin binding is) is expressed in different parts of the Hypothalamus [5].
What they found was that leptin resistance was confined to a specific part of the hypothalamus, known as the Arcuate Nucleus. Cells within this part of the brain stop responding to leptin. But nobody knows why these cells stop responding to leptin. However, it is significant that leptin signalling in the arcuate nucleus is down-regulated ,as opposed to other leptin receptors in the brain. for a start, Leptin has more than just one function it also acts on the reproductive system, and helps regulate gonadotrophin secretion in the pituitary. A lack of leptin can stop puberty (because the body needs fat for certain aspects of reproduction and puberty. Similar effects can be seen in anorexic children, who suffer from a leptin deficiency simply because they don't have enough fat cells.)
However, in induced leptin resistance, the cells in the arcuate nucleus ( the part of the brain which helps to regulate appetite) are more highly affected than other cells in the brain. This suggests that the downstream signals (rather than a specific receptor-receptor interaction) causes leptin resistance [5].
Arcuate Nucleus
What is the arcuate nucleus? and how does it help control your food intake?
The Arcuate nucleus consists of a bundle of neurones at the base of the hypothalamus, which is situated near to the 3rd ventricle of the brain (ventricles are filled with cerebro-spinal fluid which keeps brain cells alive)
The arcuate nucleus is made up of two types of neuroens. the first type are identified by their expression of neuropeptide Y (NPY) and agouti related peptide (AgRP), and the second type are identified pro-opiomelanocortin (POMC) and Cocaine and Amphetamine regulated transcript (CART). These neurones have opposing functions, with the 1st type stimulates feeding, the second type inhibits feeding.
Each of these neurones responds to specific appetite hormone signals, and in response can communicate to other parts of the brain, and with the gut to change feeding habits.
Through these different signals, it is able to "talk" to the stomach, the Duodenum, the jejunum, the ileum, the colon, the pancreas and the fat cells.
The arcuate nucleus is essentially the part of the brain which is supposed to tell you that you are full when you have had enough to eat.
How do my Organs tell my Brain that I'm Hungry?
Your body likes to keep itself in stable conditions, with stable blood sugar, stable fat content etc.
We've already talked about how fat cells secrete leptin to tell you how fat you are. If you have lots of fatty stores, the leptin produced by these stores should tell your brain to not eat so much. If there is not that much leptin around (I.e. if you've been starved for a while, or just have a low body fat content) then you will seek out fatty foods.
Your stomach also tells you when you are hungry, especially if you keep to a regular daily meal schedule. The Stomach produces a hormone known as ghrelin. This hormone reacts in an opposite way to leptin, in that it increases those hunger pangs you feel, rather than decreases them.
It has been found that the levels of ghrelin increase just before a meal [6] , and there is evidence that it is influenced by the circadian rhythm of the body. This would be advantageous, because ghrelin increases acid production in the stomach in preparation for a meal. Studies have shown that the brain can induce expression of ghrelin when it expects food to be served [8], and there is a sharp increase in ghrelin at customary meal times. So to some extent, ghrelin production is trained at an early age to orient towards meal times. But these rhythms can be changed via habituation. If you are used to having 5 meals a day, your brain trains itself to be hungry at those times of day.
There is a rare syndrome, prader -willi syndrome, which is one of the few forms of genetic obesity around. One of the ways of characterising it is that sufferers have 2-3 times more ghrelin production than normal people. so they feel much more hungry than a normal person.
In contrast, in normal obese patients , the levels of ghrelin are in fact lower, as it's production is believed to be in some way inhibited by leptin.
I have only named two hormones which are involved in hunger, but there are probably more out there which have yet to be discovered.
How do My Organs Tell me That I'm Full Up ?
This is a bit more complicated, as there are different reactions at different organs.
The Stomach: The Stomach is a muscular mass which churns up the food. the splanchnic and the sensory vagal nerves are heavily involved in telling you when you've had enough to eat. There are stretch receptors in the stomach that signal to the vagal and spinal sensory nerves that there is food in the stomach[9]. However, this is not usually a significant effect, because food is regularly taken out of the stomach and dumped into the intestine, so there isn't much opportunity for the stretch receptors to be stimulated in this way.
The Intestine: It is here that satiation can be best controlled. Unlike the stomach, the intestine has eneteroendocrine cells, which are able to detect the nutrients within the food, and therefore whether more or less food needs to be eaten. many of the signals produced by the intestine inhibit the emptying of the stomach, which leads to a build up of food within the stomach, activating the stretch receptors.
CCK (Cholecystokinin) is one of the main hormones secreted by the intestine. This is produced in the duodenum and the jejunum, and is produced by I cells. There have been attempts to turn this peptide into a viable treatment, but a single dose only protects against hunger for about half an hour.
GLP-1 (Glucagon-like peptide 1), this is expressed in the L cells of the lower GI tract, and in the pancreas as well. It acts to decrease food intake. More importantly, it has been found to accentuate insulin, and inhibit glucagon secretion. It is currently being developed as a drug to treat diabetes. Exenitide is a drug which stimulates the receptor for GLP-1 in the hypothalamus. However, there are GLP-1 receptors in the amygdala, which when stimulated, cause feelings of nausea.
Oxyntomodulin: this is also produced in L-cells, and it has been shown to not only decrease appetite, but also increase activity levels, although it is not known how it does these things.
PYY (Pancreatic polypeptide fold) is also mainly produced by L-cells in the intestine, and is secreted after a meal in proportion to the amount of calories within the meal. The intersting thing about this peptide is that when it is administered via the body to people, it is an inhibitor of food intake, but when it is administered via the brain, it is a stimulator. The reason for this is due to the administration of PYY to the brain allowing for receptors access to the hormone that they would not get through peripheral administration.
I could go on for years about all the different hormones that are stimulated. But basically, your intestine detects nutrient levels and sends messages to the brain. Each of these signals has been studied, and they are currently developing a whole swath of drugs based on these signals to combat obesity.
How Do People resist these Signals and Become Obese ?
This is a quite difficult question, mainly because it's not the same for everybody. I've already talked about Leptin deficient children, whom eat a lot because they have no leptin to tell them that they've had too much to eat. People with Prader-Willi syndrome have excess ghrelin production, and a deformation in their vagus berve which means that not only are they more hungry, but they are less able to tell when they are full.
But genetic diseases represent the extreme minority of cases of obesity. 50% of people in the UK are classed as overweight. It is predicted that by 2010 (2 years away) 12 million adults and 1 million children will be obese. This is not just about genetics, something significant in the environment has changed over the past hundred years which has caused obesity (it's not global warming)
The most obvious thing to point out is the existance of "fast food". Fifty years ago, there were no ready meals, or junk food outlets. The food we get from those shops is very different from what we would cook in our own kitchens. Try making burgers yourself, and then compare the ingredients you've used with those and those you see on the back of a burger meal.
So why doesn't your body immediately stop you eating a whole "super fun" meal from your local junk food outlet. Why doesn't the level of hormones in your intestine tell you exactly when you've reached your correct caloric intake? How come after eating at a junk food store, you find that you are still hungry?
Well, the effects of food extend beyond the hypothalamus of the brain. We have a whole gamut of emotions and behaviours associated with food. The touch, sight, smell and sound of food can stimulate hunger centres within our higher brain, which ends up dialling the pizza restaurant before the hypothalamus has anything to say about it. The fact that we attribute emotions, such as good feelings with some foods, can dictate a lot of our food habits. [10]
the memory of food has an effect on how much we behave towards it. You can catch a whiff of your favourite food on the air, and immediately you think about how it tastes, how it smells, its texture and you find yourself wanting to have it. (Do you feel hungry now? all this talk of food is making me hungry...I'll go off for a snack..)
The mu-opiod receptor is one of the receptors in the brain which affects this "want reflex". In mice injected with mu-opiod show a particular requirement for sucrose and fat rich foods. it is believed that opiods have some effect on the "pleasure" response involved in eating food [11]. This is response is likely to be due to the nucleus accumbens , a complicated structure within the brain which is also an integral region in drug reward.
So essentially, the brain gets "rewarded" every time it eats fatty foods. The desire for a person to get this reward can overrule other signals from your stomach and hypothalamus. Your higher brain has multiple inputs into the hypothalamus, which are theorised to "move the goalposts" of energy requirements.
They do this by interfering in the arcuate nucleus, and disabling the POMC/CART receptors, which are needed to tell you when you are full up [12]. This was found through an experiment in which mice had their nucleus accumbens stimulated by a neuropeptide (Muscimol, a GABA-ergic receptor agonist). It was found that these mice had increased food intake. Moreover, histochemical staining revealed that the cells in the arcuate nucleus of the hypothalamus were affected. The activity of these neurones was measured through their Fos expression (fos is an important transcription factor for hormones.) it was found that POMC/CART neurones had a lower Fos expression, and NPY/AgRP neurones had greater expression of POMC. this experiment demonstrates how higher brain functions can override the hypothalamus.
Companies who sell you foods want them to be as tasty and as palatable and as cheap as possible, so we find ourselves bombarded by literrally hundreds of products designed to elicit a positive response from our brains. Delicious, sweet, fatty unhealthy food has never been more readily available to the masses. There are adverts blaring on our TV screens, all targeted to elicit a reaction from our amygdala. Watching an advert about a delicious food can elicit an emotional response from your memory, and this stimulates the orbitofrontal cortex and your nucleus accumbens, making you desire that food.
The reward/pleasure circuits in our brains mean that we can get addicted to food very easily. (for more on addiction, look at my world of warcraft post). People who are depressed self medicate themselves with food, so as to stimulate the pleasure centres in their brains to combat the negative emotions they are feeling at the time. This is , of course, a Primary Addiction.
And while this happens, we find ourself in a society that requires us to sit at a desk more and more, and not do any sort of exercise to counterract the increase in nutrient intake [10] The very domesticity of our life is causing our waistlines to expand. Not only at work, but at home, our forms of entertainment are becoming less physical (unless you buy a wii). Even our pets are becoming fatter.
Is it any wonder that we have people who weigh half a ton in our society, when it seems so geared into tricking us to eat big and eat fast ?
It makes me wonder whether there is some alien conspiricy which has infiltrated our government, so that the fattest of our society can be shipped off to a far off world where they could feed millions of starving aliens. of course, this is incredibly unlikely. Fat humans are quite poor nutritionally, and even aliens need to watch their eight. We'd probably end up as engine fuel.
1. "Experimental hypothalamic obesity."KENNEDY GC Proc R Soc Med. 1951 Oct;44(10):899-902.
2. "The Role of Depot Fat in the Hypothalamic Control of Food Intake in the Rat"G. C. KennedyProceedings of the Royal Society of London. Series B, Biological Sciences, Vol. 140, No. 901 (Jan. 15, 1953), pp. 578-592
3. "A mutation in the human leptin receptor gene causes obesity and pituitary dysfunction"
Karine Clément, Christian Vaisse et al ,Nature 392, 398-401 (26 March 1998) doi:10.1038/32911
4. "Effect of three treatment schedules of recombinant methionyl human leptin on body weight in obese adults: a randomized, placebo-controlled trial." Diabetes, Obesity & Metabolism. 7(6):755-761, November 2005. Zelissen, P. M. J. 1; Stenlof, K. 2; Lean, M. E. J. 3; Fogteloo, J. 4; Keulen, E. T. P. 5; Wilding, J. 6; Finer, N. 7; Rossner, S. 8; Lawrence, E. 9; Fletcher, C. 9; McCamish, M.
5. "Region-Specific Leptin Resistance within the Hypothalamus of Diet-Induced Obese Mice" Heike Münzberg, Jeffrey S. Flier and Christian Bjørbæk , Endocrinology, doi:10.1210/en.2004-0726
6.A Preprandial Rise in Plasma Ghrelin Levels Suggests a Role in Meal Initiation in Humans David E. Cummings, Jonathan Q. Purnell, R. Scott Frayo, Karin Schmidova, Brent E. Wisse, and David S. Weigle, Diabetes 50:1714-1719, 2001
7. "Ghrelin Stimulates GH But Not Food Intake in Arcuate Nucleus Ablated Rats" Hideki Tamura, Jun Kamegai, Takako Shimizu, Shinya Ishii, Hitoshi Sugihara and Shinichi Oikawa, Endocrinology Vol. 143, No. 9 3268-3275
8. "Spontaneous 24-h ghrelin secretion pattern in fasting subjects: maintenance of a meal-related pattern ", G Natalucci, S Riedl, A Gleiss1, T Zidek2 and H Frisch , DOI: 10.1530/eje.1.01919European Journal of Endocrinology, Vol 152, Issue 6, 845-850
9. "Gut vagal afferent lesions increase meal size but do not block gastric preload-induced feeding suppression" Gary J. Schwartz, Cynthia F. Salorio, Chris Skoglund, and Timothy H. Moran Am J Physiol Regul Integr Comp Physiol 276
10. "Interactions between the “cognitive” and “metabolic” brain in the control of food intake " Hans-Rudolf Berthoud , Physiology & Behavior Volume 91, Issue 5, 15 August 2007, Pages 486-498 doi:10.1016/j.physbeh.2006.12.016
11. Enhanced intake of high-fat food following striatal mu-opioid stimulation: microinjection mapping and Fos expression
M. Zhang and A. E. Kelley Neuroscience Volume 99, Issue 2, 9 August 2000, Pages 267-277 ,doi:10.1016/S0306-4522(00)00198-6
12 . "Appetite-inducing accumbens manipulation activates hypothalamic orexin neurons and inhibits POMC neurons"
Zheng, H.a , Corkern, M.a , Stoyanova, I.a , Patterson, L.M.a , Tian, R.a , Berthoud, H.-R, American Journal of Physiology - Regulatory Integrative and Comparative Physiology Volume 284, Issue 6 53-6, 1 June 2003, Pages R1436-R1444
Sunday, 6 January 2008
Stem Cells Get Rid of Graft vs Host Disease
A New story has just broke in new scientist (yes, that is where i get all my science news... but for f*#ks sake it's the only news outlet that makes the effort to cite their original article sources.)
A clinical trial has just been done in which stem cells have been used to combat graft vs host disease.
What is Graft vs Host Disease
There are some diseases which affect white blood cells, and red blood cells. These include Sickle Cell anaemia, Leukaemia and countless other diseases. In some cases, the only way to cure these diseases is to have a bone marrow transplant operation.
Bone marrow is where all the blood cells originate, and contains hemapoietic stem cells (blood-making stem cells) If this is not producing functional white blood cells (e.g. in Severe Combined Immunodeficiency) or producing malfunctioning or dangerous white blood cells (leukaemia, and sickle cell anaemia), it can be replaced in a bone marrow transplant operation.
So a person (usually within the same family as the sufferer) will donate some bone marrow to the sick individual. if all goes well, this new bone marrow will grow and will cure the patients disease.
However, sometimes there are some of the donor's immune cells left over in the bone marrow graft. These cells are designed to recognise any antigen that does not belong to their host. So when they are placed in a new host, it is likely that they will see some antigens that they have never seen before, and they will start to attack the new host. This is Graft vs Host Disease.
The general way to tackle this disease is by depleting the levels of T-cells from the bone marrow transplants, and depressing the patient's immune system with drugs such as cyclosporin A.
However this is not a watertight treatment, and it is still possible to get Graft vs Host Disease after this
So How Can Stem Cells Help With This Disease ?
The popular definition of a stem cell is a cell which can "divide and differentiate into another type of cell". But this function is not very useful in Graft vs Host Disease, as the problem is with the immune system, and not with any particular cell deficiency.
However, some types of stem cells have different functions within the body, and don't just "replenish and grow". If that function could serve a purpose, it would surely be solved via an infusion of haemopoietic stem cells, which are found in the bone marr... oh wait.
However, a different type of stem cell exists, known as the Mesenchymal Stem Cell.
What are Mesenchymal Stem Cells ?
Mesenchymal stem cells are found in the bone marrow, although at a relatively low concentration (0.01-0.001% of the stem cell population) [1]. They differentiate into bone cells, cartilage cells, and bone marrow stromal cells.
However, they are more commonly found in the umbilical cord blood [3], and it is believed that they circulate through the babay and the mother during pregnancy [2], and these cells engraft in the mothers bone marrow. The extraordinary thing about this is that they do this without eliciting a host vs graft or graft vs host reaction. In fact, these cells can live in the mother up to ten years after pregnancy.
How do they do this?
It is thought that mesenchymal stem cells can act to modulate the immune system. it has been that they are able to block T-cell reactions, and prevent the rejection of a skin graft in baboons.[4]
In fact the degree of tolerance that these stem cells are capable of achieving is good enough to support a xenogeneic transplant, i.e. a transplantation between two species (rat and mouse) [6]
These cells have also been used to treat a patient for osteogenesis imperfecta [5], even though the tissue types of the donor and the host were vastly different.
it is thought that they cause tolerance through emitting special cytokines, like TGF-β and other products. the actual mechanism throuh which they induce this tolerance is still under investigation.
What's on the Market?
A mesenchymal stem cell therapy marketed by Osiris therapeutics, known as Prochymal is currently in development.
Prochymal consists of mesenchymal stem cells prepared from the bone marrow of healthy donors.
In the phase 2 trial, 32 patients with graft vs host disease were treated with experimental infusions of this product in conjunction with steroid therapy, alongside a control group which recieved only steroid therapy.
of the treated patients, 72% showed a complete resolution of clinical symptoms, with 19% showing a partial effect and the remaining percentage with no effect.
These are incredibly encouraging results, and now a Phase 3 clinical trial has started. This Double Blind Randomised control trial may make or break this product.
If this trial does go really well, it will open up a whole can of worms in medicine.
For a start, mesenchymal stem cells can be used to help in a whole variety of tissue transplant situations. they can be used to help healing wounds, repairing bone. These cells have been used in the lab as a gene therapy delivery system. The whole face of medicine could be changed
However, let's not get too excited about this. One problem with basing therapies off any form of stem cells is that you need a reliable source for them. You can't simply extract the stem cells from one person, grow them up in culture and solve the problems of the world. For a start, cells dividing in culture acquire mutations. So you may end up accidentally giving a patient dangerously mutated stem cells.
The only way to prevent this is to make sure that lots of people give bone marrow. A bone marrow extraction operation is incredibly painful. Considering how many people turn up for blood donation, you can't really expect a great outpouring of people to give their bone marrow.
On the other hand, many people are happy to donate the umbilical cords of their babies, and these have been found to be quite rich in mesenchymal stem cells. the only problem is that these cells are a quite temperamental, and harder (and therefore more expensive) to work with. Nevertheless, there are umbilical cord blood banks in operation at the moment, whoch freeze the blood sample from the cord, and preserve them, until such time that cord blood based stem cell therapy becomes sufficiently advanced.
I have high hopes, but time will tell whether they are validated or not.
1. Campagnoli C, Roberts IAG, Kumar S, Bennett PR, Bellantuono I, Fisk NM: Identification of mesenchymal stem/progenitor cells in human first-trimester fetal blood, liver, and bone Marrow. Blood 2001, 98(8):2396-2402.
2. O'Donoghue K, Chan J, de la Fuente J, Kennea N, Sandison A, Anderson JR, Roberts IAG, Fisk NM: Microchimerism in female bone marrow and bone decades after fetal mesenchymal stem-cell trafficking in pregnancy. Lancet 2004, 364(9429):179-182.
3.Erices A, Conget P, Minguell JJ: Mesenchymal progenitor cells in human umbilical cord blood. British Journal of Haematology 2000, 109(1):235-242.
4. Bartholomew A, Sturgeon C, Siatskas M, Ferrer K, McIntosh K, Patil S, Hardy W, Devine S, Ucker D, Deans R et al: Mesenchymal stem cells suppress lymphocyte proliferation in vitro and prolong skin graft survival in vivo. Experimental Hematology 2002, 30(1):42-48.
5.Le Blanc K, Gotherstrom C, Ringden O, Hassan M, McMahon R, Horwitz E, Anneren G, Axelsson O, Nunn J, Ewald U et al: Fetal mesenchymal stem-cell engraftment in bone after in utero transplantation in a patient with severe osteogenesis imperfecta. Transplantation 2005, 79(11):1607-1614.
6.Saito T, Kuang JQ, Bittira B, Al-Khaldi A, Chiu RCJ: Xenotransplant cardiac chimera: Immune tolerance of adult stem cells. Annals of Thoracic Surgery 2002, 74(1):19-24.
A clinical trial has just been done in which stem cells have been used to combat graft vs host disease.
What is Graft vs Host Disease
There are some diseases which affect white blood cells, and red blood cells. These include Sickle Cell anaemia, Leukaemia and countless other diseases. In some cases, the only way to cure these diseases is to have a bone marrow transplant operation.
Bone marrow is where all the blood cells originate, and contains hemapoietic stem cells (blood-making stem cells) If this is not producing functional white blood cells (e.g. in Severe Combined Immunodeficiency) or producing malfunctioning or dangerous white blood cells (leukaemia, and sickle cell anaemia), it can be replaced in a bone marrow transplant operation.
So a person (usually within the same family as the sufferer) will donate some bone marrow to the sick individual. if all goes well, this new bone marrow will grow and will cure the patients disease.
However, sometimes there are some of the donor's immune cells left over in the bone marrow graft. These cells are designed to recognise any antigen that does not belong to their host. So when they are placed in a new host, it is likely that they will see some antigens that they have never seen before, and they will start to attack the new host. This is Graft vs Host Disease.
The general way to tackle this disease is by depleting the levels of T-cells from the bone marrow transplants, and depressing the patient's immune system with drugs such as cyclosporin A.
However this is not a watertight treatment, and it is still possible to get Graft vs Host Disease after this
So How Can Stem Cells Help With This Disease ?
The popular definition of a stem cell is a cell which can "divide and differentiate into another type of cell". But this function is not very useful in Graft vs Host Disease, as the problem is with the immune system, and not with any particular cell deficiency.
However, some types of stem cells have different functions within the body, and don't just "replenish and grow". If that function could serve a purpose, it would surely be solved via an infusion of haemopoietic stem cells, which are found in the bone marr... oh wait.
However, a different type of stem cell exists, known as the Mesenchymal Stem Cell.
What are Mesenchymal Stem Cells ?
Mesenchymal stem cells are found in the bone marrow, although at a relatively low concentration (0.01-0.001% of the stem cell population) [1]. They differentiate into bone cells, cartilage cells, and bone marrow stromal cells.
However, they are more commonly found in the umbilical cord blood [3], and it is believed that they circulate through the babay and the mother during pregnancy [2], and these cells engraft in the mothers bone marrow. The extraordinary thing about this is that they do this without eliciting a host vs graft or graft vs host reaction. In fact, these cells can live in the mother up to ten years after pregnancy.
How do they do this?
It is thought that mesenchymal stem cells can act to modulate the immune system. it has been that they are able to block T-cell reactions, and prevent the rejection of a skin graft in baboons.[4]
In fact the degree of tolerance that these stem cells are capable of achieving is good enough to support a xenogeneic transplant, i.e. a transplantation between two species (rat and mouse) [6]
These cells have also been used to treat a patient for osteogenesis imperfecta [5], even though the tissue types of the donor and the host were vastly different.
it is thought that they cause tolerance through emitting special cytokines, like TGF-β and other products. the actual mechanism throuh which they induce this tolerance is still under investigation.
What's on the Market?
A mesenchymal stem cell therapy marketed by Osiris therapeutics, known as Prochymal is currently in development.
Prochymal consists of mesenchymal stem cells prepared from the bone marrow of healthy donors.
In the phase 2 trial, 32 patients with graft vs host disease were treated with experimental infusions of this product in conjunction with steroid therapy, alongside a control group which recieved only steroid therapy.
of the treated patients, 72% showed a complete resolution of clinical symptoms, with 19% showing a partial effect and the remaining percentage with no effect.
These are incredibly encouraging results, and now a Phase 3 clinical trial has started. This Double Blind Randomised control trial may make or break this product.
If this trial does go really well, it will open up a whole can of worms in medicine.
For a start, mesenchymal stem cells can be used to help in a whole variety of tissue transplant situations. they can be used to help healing wounds, repairing bone. These cells have been used in the lab as a gene therapy delivery system. The whole face of medicine could be changed
However, let's not get too excited about this. One problem with basing therapies off any form of stem cells is that you need a reliable source for them. You can't simply extract the stem cells from one person, grow them up in culture and solve the problems of the world. For a start, cells dividing in culture acquire mutations. So you may end up accidentally giving a patient dangerously mutated stem cells.
The only way to prevent this is to make sure that lots of people give bone marrow. A bone marrow extraction operation is incredibly painful. Considering how many people turn up for blood donation, you can't really expect a great outpouring of people to give their bone marrow.
On the other hand, many people are happy to donate the umbilical cords of their babies, and these have been found to be quite rich in mesenchymal stem cells. the only problem is that these cells are a quite temperamental, and harder (and therefore more expensive) to work with. Nevertheless, there are umbilical cord blood banks in operation at the moment, whoch freeze the blood sample from the cord, and preserve them, until such time that cord blood based stem cell therapy becomes sufficiently advanced.
I have high hopes, but time will tell whether they are validated or not.
1. Campagnoli C, Roberts IAG, Kumar S, Bennett PR, Bellantuono I, Fisk NM: Identification of mesenchymal stem/progenitor cells in human first-trimester fetal blood, liver, and bone Marrow. Blood 2001, 98(8):2396-2402.
2. O'Donoghue K, Chan J, de la Fuente J, Kennea N, Sandison A, Anderson JR, Roberts IAG, Fisk NM: Microchimerism in female bone marrow and bone decades after fetal mesenchymal stem-cell trafficking in pregnancy. Lancet 2004, 364(9429):179-182.
3.Erices A, Conget P, Minguell JJ: Mesenchymal progenitor cells in human umbilical cord blood. British Journal of Haematology 2000, 109(1):235-242.
4. Bartholomew A, Sturgeon C, Siatskas M, Ferrer K, McIntosh K, Patil S, Hardy W, Devine S, Ucker D, Deans R et al: Mesenchymal stem cells suppress lymphocyte proliferation in vitro and prolong skin graft survival in vivo. Experimental Hematology 2002, 30(1):42-48.
5.Le Blanc K, Gotherstrom C, Ringden O, Hassan M, McMahon R, Horwitz E, Anneren G, Axelsson O, Nunn J, Ewald U et al: Fetal mesenchymal stem-cell engraftment in bone after in utero transplantation in a patient with severe osteogenesis imperfecta. Transplantation 2005, 79(11):1607-1614.
6.Saito T, Kuang JQ, Bittira B, Al-Khaldi A, Chiu RCJ: Xenotransplant cardiac chimera: Immune tolerance of adult stem cells. Annals of Thoracic Surgery 2002, 74(1):19-24.
Saturday, 5 January 2008
Fake Blood? This Is a Hospital NOT a Horror Movie
Yesterday, New Scientist broke the story about a company, known as HemoBiotech which has come up with a more realistic form of fake blood, called HemoTech. I don't mean that they've finally realised that cherryade is too pink for use in movies. No, I mean fake blood that can keep people alive.
Vampires around the globe are now at the edge of their seats (or coffins..or whatever..who cares, they don't really exist)
The companies claims about their product seem really quite impressive. They've just submitted a patent application for their product and they are hoping to start trials on it soon.
What is Fake Blood and Why Do we Need It ?
In our bodies, we need blood mainly to transport oxygen to the living cells of our bodies, and remove carbon-dioxides and other waste gases from our cells. This is done by red blood cells which contain haemoglobin, and this binds to oxygen and transports it to our body cells.
When a person has an accident, a lot of blood is lost, and so there are a lot of cells in the body which end up needing oxygen. If circulation isn't replaced, the body's cells can end up dying off.
This is why , during accidents, and in some traumatic surgical operations, people need blood transfusions. However, not every blood group is compatible, and immune reactions can occur in which the transfused blood can be rejected, leading to a systemic inflammatory response (which is not good)
However, if you could develop a hypoallergenic fake blood substitute which performs all the same functions as red blood cells. However, this fake blood cannot be a replacement, as blood has multiple other functions which need to be performed on a longer term basis. This is only a short term treatment.
A Short History of Blood transfusions
People have been experimenting with replacing blood for over a century. Animal to human blood transfusions have been attempted since the sixteenth century. Sir Christopher Wren suggested that ale, wine and opiates should be used as a substitute for blood (he may have ended up killing his patients, but they were a lot more happy) Animal transfusions were also performed, but ended up being banned in 1677
1878 is when the first successful human-to-human transfusions occurred (with a 50% success rate).
if you want to read more about this, look here
Types of Fake Blood
Haemoglobin protein
Normal red blood cells which transport oxygen to the body are packed with haemoglobin- this is the molecule which actually binds to and carries the oxygen. So the most logical step for creating fake blood would be to use this as a substitute. Amberson carried out investigations into this in the 1930's, and managed to keep his lab animals alive for 36 hours.[2] He soon moved on to trying it out on human patients with some success[3]. That is, he cured the disease he treated his patients for. One of the problems with using haemoglobin protein on it's own is that it is toxic to the kidneys. haemoglobin is usually only kept in red blood cells, and it isn't leaked out into the bloodstream usually. This means that the blood cells , and the haemoglobin molecules within them, are disposed of in the spleen (yes that's what your spleen is for).
However, when haemoglobin molecules are on their own, they can end up in the kidneys, where they can cause severe damage. Not only that, but haemoglobin on its own can also cause the build up of superoxide radicals, and it can dissolve in the blood vessel walls to cause over-oxygenation. In response to this , the blood vessels constrict, causing hypertension.
So there is a great need to make haemoglobin molecules less toxic
This is done by taking a bunch of haemoglobin molecules and joining them up to form a large bundle, which prevents them going out of control. This in itself is quite difficult, because by joining up haemoglobin molecules, you change their properties, and make it so that they don't bind the blood as well. However, this problem has been solved, and there have been animal trials in which artificial blood has kept animals alive for several days [4]
There are several haemoglobin-based blood substitutes in development.
Hemopure: This product was developed by biopure, and is based on cow haemoglobin. It has been registered in South Africa for the treatment of clinical anaemia. It has shown positive results here, but there are some side effects.
PolyHeme and Hemalink are other blood products on the market which have also produced trials, albeit with slightly mixed results. Generally, they "Do what they say on the tin", they work as blood substitutes. But there are worries about side effects. (Hemalink may have caused heart problems in a clinical trial, Patients treated with PolyHeme seemed to do worse than patients treated with saline in one trial)
However, the main problem at the moment with these is that they are incredibly hard to produce. Extracting haemoglobin from blood donor cells, and then crosslinking it costs a lot of time energy and money.
Liposome Encapsulated Haemoglobin
Liposomes are small spheres constructed out of lipids. these can be used as carriers for haemoglobin. the advantages of these are that they don't have any blood group antigens to elicit an immune response, and they can be used as haemoglobin carriers, and thus prevent haemoglobin toxicity associated with the other treatments mentioned above.
However, the main problem here is that this technology is still in very early stages, and development has been difficult. For a start, its been difficult getting the size of the liposomes correct, in order to make sure they don't get trapped in capillaries.
There have been successful experiments in lab animals demonstrating the oxygen carrying capability of these constructs [5], but the research is seems to be a long time away from human trials, and pharmaceutical companies have not yet jumped on this bandwagon. Possibly it could be that with this treatment, you are taking the already expensive haemoglobin extraction process, and then getting it packaged into liposomes to industry quality.
Perfluorocarbons
Experiments with perfluorocarbons as oxygen carriers started in the 60's. Perfluorocarbons are good, because they are less poisonous than using pure haemoglobin, and cheaper to manufacture.
Also, they are able to bind to a lot of oxygen to the extent that it is possible for animals to survive if they are completely submersed in perfluorocarbon[1].
The perfluorocarbons are also good because they are readily excreted through the lungs- you end up breathing it out. So it is a relatively safe treatment. however, there are some problems with it:
HemoBiotech are offering a Crosslinked Bovine Haemoglobin based treatment, similar to the HemoPure treatment which is arguably one of the more successful blood replacement products.
The advantages of using bovine haemoglobin is that there is a ready supply. If there was enough human haemoglobin available, we wouldn't need blood substitutes.
However, where Hemotech differs from previous Haemoglobin treatments is that it has conjugated anti-inflammatory signals with it's haemoglobin. This is a direct effort to counter-act the toxic side effects encountered by other drugs. it is conjugated with glutathione and adenosine, both of which have anti-inflammatory , and more importantly vasodilatory effects, so hypertension should not (theoretically) be a side effect. HemoBiotech's Jan Simoni has spent some time studying the effects of haemoglobin on the circulatory system [6] and essentially identified that the main "nemesis of blood substitute developers" is the vasoconstriction effect.
So on paper, it seems that this could end up being a successful treatment. However, I would be very cautious about a product like this before a clinical trial.
This is mainly because for a clinical trial, there are often side effects that pop up that no-one expects. Putting an anti-inflammatory component could be a great idea, and it could work perfectly, and Nobel prizes and big cigars will be handed out. But then again, it may not be a great idea. What is being marketed is not a non-inflammatory version of fake blood, but an anti-inflammatory edition. The idea behind it is not to avoid a reaction altogether, but to counteract any inflammatory reaction enough so that there is no visible effect.
This means that any anti-inflammatory, or indeed pro-inflammatory drugs, will be affected by the artificial blood in the patients blood stream. If you are looking at major blood replacement, this dose of anti-inflammatory could be EXTREMELY high.
this is all complicated by the fact that regulatory authorities also have to account for athletes obtaining samples of fake blood, and using them to enhance their performance in competitions. If that fake blood is toxic, you may as well be giving out poison (which is NOT ethical).
Imagine you are on a life boat and suddenly it springs a leak. You stick your thumb in that leak, and two more pop up. This is what I imagine it's like for people developing fake blood. They get one problem solved, and two or three more pop up.
So if I were you, i wouldn't wait for scientists to come up with a fake blood solution. Go out and Donate Blood. Seriously.
Vampires around the globe are now at the edge of their seats (or coffins..or whatever..who cares, they don't really exist)
The companies claims about their product seem really quite impressive. They've just submitted a patent application for their product and they are hoping to start trials on it soon.
What is Fake Blood and Why Do we Need It ?
In our bodies, we need blood mainly to transport oxygen to the living cells of our bodies, and remove carbon-dioxides and other waste gases from our cells. This is done by red blood cells which contain haemoglobin, and this binds to oxygen and transports it to our body cells.
When a person has an accident, a lot of blood is lost, and so there are a lot of cells in the body which end up needing oxygen. If circulation isn't replaced, the body's cells can end up dying off.
This is why , during accidents, and in some traumatic surgical operations, people need blood transfusions. However, not every blood group is compatible, and immune reactions can occur in which the transfused blood can be rejected, leading to a systemic inflammatory response (which is not good)
However, if you could develop a hypoallergenic fake blood substitute which performs all the same functions as red blood cells. However, this fake blood cannot be a replacement, as blood has multiple other functions which need to be performed on a longer term basis. This is only a short term treatment.
A Short History of Blood transfusions
People have been experimenting with replacing blood for over a century. Animal to human blood transfusions have been attempted since the sixteenth century. Sir Christopher Wren suggested that ale, wine and opiates should be used as a substitute for blood (he may have ended up killing his patients, but they were a lot more happy) Animal transfusions were also performed, but ended up being banned in 1677
1878 is when the first successful human-to-human transfusions occurred (with a 50% success rate).
if you want to read more about this, look here
Types of Fake Blood
Haemoglobin protein
Normal red blood cells which transport oxygen to the body are packed with haemoglobin- this is the molecule which actually binds to and carries the oxygen. So the most logical step for creating fake blood would be to use this as a substitute. Amberson carried out investigations into this in the 1930's, and managed to keep his lab animals alive for 36 hours.[2] He soon moved on to trying it out on human patients with some success[3]. That is, he cured the disease he treated his patients for. One of the problems with using haemoglobin protein on it's own is that it is toxic to the kidneys. haemoglobin is usually only kept in red blood cells, and it isn't leaked out into the bloodstream usually. This means that the blood cells , and the haemoglobin molecules within them, are disposed of in the spleen (yes that's what your spleen is for).
However, when haemoglobin molecules are on their own, they can end up in the kidneys, where they can cause severe damage. Not only that, but haemoglobin on its own can also cause the build up of superoxide radicals, and it can dissolve in the blood vessel walls to cause over-oxygenation. In response to this , the blood vessels constrict, causing hypertension.
So there is a great need to make haemoglobin molecules less toxic
This is done by taking a bunch of haemoglobin molecules and joining them up to form a large bundle, which prevents them going out of control. This in itself is quite difficult, because by joining up haemoglobin molecules, you change their properties, and make it so that they don't bind the blood as well. However, this problem has been solved, and there have been animal trials in which artificial blood has kept animals alive for several days [4]
There are several haemoglobin-based blood substitutes in development.
Hemopure: This product was developed by biopure, and is based on cow haemoglobin. It has been registered in South Africa for the treatment of clinical anaemia. It has shown positive results here, but there are some side effects.
PolyHeme and Hemalink are other blood products on the market which have also produced trials, albeit with slightly mixed results. Generally, they "Do what they say on the tin", they work as blood substitutes. But there are worries about side effects. (Hemalink may have caused heart problems in a clinical trial, Patients treated with PolyHeme seemed to do worse than patients treated with saline in one trial)
However, the main problem at the moment with these is that they are incredibly hard to produce. Extracting haemoglobin from blood donor cells, and then crosslinking it costs a lot of time energy and money.
Liposome Encapsulated Haemoglobin
Liposomes are small spheres constructed out of lipids. these can be used as carriers for haemoglobin. the advantages of these are that they don't have any blood group antigens to elicit an immune response, and they can be used as haemoglobin carriers, and thus prevent haemoglobin toxicity associated with the other treatments mentioned above.
However, the main problem here is that this technology is still in very early stages, and development has been difficult. For a start, its been difficult getting the size of the liposomes correct, in order to make sure they don't get trapped in capillaries.
There have been successful experiments in lab animals demonstrating the oxygen carrying capability of these constructs [5], but the research is seems to be a long time away from human trials, and pharmaceutical companies have not yet jumped on this bandwagon. Possibly it could be that with this treatment, you are taking the already expensive haemoglobin extraction process, and then getting it packaged into liposomes to industry quality.
Perfluorocarbons
Experiments with perfluorocarbons as oxygen carriers started in the 60's. Perfluorocarbons are good, because they are less poisonous than using pure haemoglobin, and cheaper to manufacture.
Also, they are able to bind to a lot of oxygen to the extent that it is possible for animals to survive if they are completely submersed in perfluorocarbon[1].
The perfluorocarbons are also good because they are readily excreted through the lungs- you end up breathing it out. So it is a relatively safe treatment. however, there are some problems with it:
- They are not soluble with the blood, and therefore not bioavailable. the only way to get it to work would be to introduce emulsifying agents.
- They can cause inflammation, although this has been linked to the emulsifying agents which they have been administered alongside.
- The Excretion pathways for these products has not been fully mapped out. while we know that they can be excreted safely out of the lungs, it is possible that some of the metabolism occurs in the liver. in some animals exposed to these products, the Liver and the Spleen have been seen to expand, and they produce more enzymes. This could mean that they are toxic.
- These perfluorocarbons are not as good as haemoglobin at absorbing oxygen (if they were better at grabbing oxygen than haemoglobin, immersing a rat in a bath of perfluorocarbon would cause it to have the oxygen sucked out of it's blood cells, rather than sucked in) Patients undergoing this treatment have to breath pure oxygen in order for the treatment to be effective.
HemoBiotech are offering a Crosslinked Bovine Haemoglobin based treatment, similar to the HemoPure treatment which is arguably one of the more successful blood replacement products.
The advantages of using bovine haemoglobin is that there is a ready supply. If there was enough human haemoglobin available, we wouldn't need blood substitutes.
However, where Hemotech differs from previous Haemoglobin treatments is that it has conjugated anti-inflammatory signals with it's haemoglobin. This is a direct effort to counter-act the toxic side effects encountered by other drugs. it is conjugated with glutathione and adenosine, both of which have anti-inflammatory , and more importantly vasodilatory effects, so hypertension should not (theoretically) be a side effect. HemoBiotech's Jan Simoni has spent some time studying the effects of haemoglobin on the circulatory system [6] and essentially identified that the main "nemesis of blood substitute developers" is the vasoconstriction effect.
So on paper, it seems that this could end up being a successful treatment. However, I would be very cautious about a product like this before a clinical trial.
This is mainly because for a clinical trial, there are often side effects that pop up that no-one expects. Putting an anti-inflammatory component could be a great idea, and it could work perfectly, and Nobel prizes and big cigars will be handed out. But then again, it may not be a great idea. What is being marketed is not a non-inflammatory version of fake blood, but an anti-inflammatory edition. The idea behind it is not to avoid a reaction altogether, but to counteract any inflammatory reaction enough so that there is no visible effect.
This means that any anti-inflammatory, or indeed pro-inflammatory drugs, will be affected by the artificial blood in the patients blood stream. If you are looking at major blood replacement, this dose of anti-inflammatory could be EXTREMELY high.
this is all complicated by the fact that regulatory authorities also have to account for athletes obtaining samples of fake blood, and using them to enhance their performance in competitions. If that fake blood is toxic, you may as well be giving out poison (which is NOT ethical).
Imagine you are on a life boat and suddenly it springs a leak. You stick your thumb in that leak, and two more pop up. This is what I imagine it's like for people developing fake blood. They get one problem solved, and two or three more pop up.
So if I were you, i wouldn't wait for scientists to come up with a fake blood solution. Go out and Donate Blood. Seriously.
1. "Survival of mammals breathing organic liquids equilibrated with oxygen at atmospheric pressure".Clark LC, Gollan F (1966). Science: 1755-6.
2. "On the use of Ringer-Locke solutions containing hemoglobin as a substitute for normal blood in mammals". Amberson WR, Flexner J, Steggerda FR, et al J Cell Comp Physiol (1934);5:359-82.
3."Clinical experience with hemoglobin-saline solutions." Amberson WR, Jennings JJ, Rhode CM. J Appl Physiol (1949):469-89.
4."Effect of a single replacement of one of Ringer lactate, hypertonic saline/dextran, 7g% albumin, stroma-free hemoglobin, o-raffinose polyhemoglobin or whole blood on the long term survival of unanesthetized rats with lethal hemorrhagic shock after 67% acute blood loss." C hang TMS, Varma R. Biomater Artif Cells Immobil Biotechnol 1992;20:503-10.
5."Normovolemic hemodilution with Hb vesicle solution attenuates hypoxia in
ischemic hamster flap tissue." Erni, D., Wettstein, R., Schramm, S., Contaldo, C., Sakai, H., Takeoka, S., Tsuchida, E., Leunig, M.,Banic, A. (2003). Am. J Physiol. Heart Circ. Physiol. 284:H1702–H1709
6."Endothelial Cell Response to Hemoglobin Based Oxygen Carriers. Is the Attenuation of Pathological Reactions Possible? (2005) Artificial Oxygen Carrier- Frontline by J. Simoni
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