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Tests re-open animal transplant debate Tuesday, 29 August, 2000, 21:26 GMT 22:26 UK - Grafts of pig cells have been used to repair the spinal cords of rodents in an experiment that is set to re-open the debate over animal-to-human transplants. Researchers in the United States transplanted tissues taken from the snout of pigs into rats with severed spinal cords. The cells had been genetically engineered to prevent them from being rejected as foreign tissues. Nerve fibres grew back, restoring nerve signals and function in seven out of 10 of the rats. Dr Jeffery Kocsis, from Yale University School of Medicine, led the research. His team engineered pig cells to express a human protein that suppresses immune rejection responses. The donor grafts came from the snout of the pig - an accessible source of different types of cell. Function restored When transplanted into rats which had their spinal cords severed, the engineered pig cells were tolerated by the animals' immune systems. The cells stimulated regeneration of rat nerves, formed new myelin (the substance that insulates nerve fibres), and restored the relay of nerve signals up and down the severed spinal cords of seven out of 10 treated rats. The nerve fibre growth occurred at a rate of about one millimetre per day, and the regenerated nerves conducted impulses faster than normal nerves. The new data is reported in the journal Nature Biotechnology. [Cloned pigs] Writing in the journal, Dr Kocsis speculates that the transformed pig cells could soon be used for the same purpose in humans - to regenerate spinal cord nerves without being rejected by the body. However, many questions remain over the safety of transplanting animal organs into humans because of concerns over the potential transmission of infectious viral agents. Separately, another team of scientists, also in the US, says it has bred pigs that do not seem to transmit potentially dangerous viruses to human cells. BioTransplant Inc., based in Charlestown, Massachusetts, says its miniature swine carried the viruses, but for some reason did not transmit them to human cells the way normal pigs do. The company hopes it can now genetically engineer its pigs so that human bodies will accept their tissue and organs. Earlier this month, Daniel Salomon, of the Scripps Institute in California, reported he had shown that pig viruses, known as porcine endogenous retroviruses, could infect human cells. BBC News Online: Sci/Tech "http://news.bbc.co.uk/low/english/sci/tech/newsid_901000/901661.stm" janet paterson 53 now / 44 dx cd / 43 onset cd / 41 dx pd / 37 onset pd tel: 613 256 8340 url: "http://www.geocities.com/janet313/" email: [log in to unmask] smail: POBox 171 Almonte Ontario K0A 1A0 Canada