Sunday, 29 July 2007

Would you like a pig’s heart?

Is it right to clone animals for human transplants? July 29, 2007 Several research groups, and companies, are trying to make transgenic and cloned pigs to alleviate the organ donor shortage. Opponents have said that it raises serious ethical issues over the use of animals and poses a major safety question for humans. Do you think this marks a scientific breakthrough in cloning and availability of organs for transplants? Or does it raise concerns over the methods being used in cloning technology? Could you think of receiving a pig organ or tissue yourself, if needed? Pigs are very suitable for many reasons, they haven’t been chosen without thought: they are about the same size (body weight) as we are, they have a very similar internal anatomy as we, they grown fast (full size within a year) and are genetically well characterised. Several research groups, and now companies, are trying to make transgenic pigs for many years now, which would lack one of the major immunological obstacles to this xenotransplantation (transplanting organs between different animals and humans). It’s a simple sugar molecule on the surface of pig cells that now has been removed in these new breeds, and before was known to be the major immunological reactant in humans transplanted with pig tissues. The animals lack the gene responsible for "alpha-1,3-galactosyltransferase" (GT) — an enzyme normally present in the pig vascular system. Humans have natural, preformed antibodies to GT, resulting in immediate (acute) rejection of any pig-to-human transplant. The fact that these genetically engineered "GT-knockout" pigs lack GT removes one obstacle to cross-species transplantation, or xenotransplantation, between pigs and humans. Apart from the possible transplantation of organs such as the kidney or heart, pigs are also viewed as a potentially invaluable source of islet cells — the insulin-producing cells of the pancreas — for use in transplantation as a treatment for type-1 diabetes. Preliminary studies have reported encouraging results with transplantation of organs from GT-KO pigs into nonhuman primates. Hearts transplanted from GT-KO pigs into baboons have survived for several months, without the need for intensive drug treatment to suppress the recipient animal's immune system. However, many obstacles remain to be overcome before exploratory studies of xenotransplantation from GT-KO pigs to humans can begin. The transplanted hearts do not show the pattern of acute, overwhelming rejection typical of cross-species transplantation. However, there is evidence of another type of rejection, characterized by blood clots developing in the small blood vessels. This suggests a possible "coagulation dysregulation" between pigs and primates. New approaches will be needed to address the problem: either improved approaches to immunosuppressant drug therapy or further genetic manipulation of the donor animals. A lot is also known about pig’s physiology during medical procedure’s which make them suitable for this kind of treatment. Do you know that live sedated pigs are used for many training purposes for catastrophe medicine (surgeons who need training on complex wounds) and military doctors (shot gun and shell wounds)! Some argue these issues can be very emotional and scary for many people. True, but that’s exactly why they need to be discussed, to take away the scary part. It is usually when you don’t know, or don’t talk about something straight out, it becomes more and more scary. When you get to know the details and ventilating your anxiety it usually becomes easier to live with. Some people ask “Why spend so much money and effort on this?” This kind of work to develop donor organs from pigs, is not particular expensive compared to other things our societies put money on. And in the long run there will be a lot of savings instead, when people can live a healthy life instead. And they are definitely not impractical experiments. If you think so, you have not understood the slightest of what can be done to help people. ......... ZenMaster

For more on stem cells and cloning, go to CellNEWS at

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