Word: pigged
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Those dismal numbers have prompted scientists to consider organs from other mammals--especially pigs, which are easily bred and whose physiology is similar to ours. But pig biology is different enough from human biology that rejection, a surmountable problem in human-to-human transplants, is disastrous in so-called xenotransplants. (Humans can receive pigs' heart valves and other tissues because they are treated to suppress the immune problem. That doesn't work for whole organs...
...solution may be on the horizon. Last week two research teams said they had removed the pig gene responsible for the most severe form of rejection. Not only that. Both teams--one from PPL Therapeutics, which in 1996 helped make Dolly the sheep, the first mammal cloned from an adult animal, and the other from the University of Missouri-Columbia and Immerge BioTherapeutics, of Charlestown, Mass.--then cloned their little pigs, producing five and four piglets, respectively...
...itself, this breakthrough won't lead directly to pig transplants. For one thing, pigs carry two copies of the gene, called GGTA1; the scientists knocked out only one. Researchers expect to create "double-knockout" pigs within a year, but until they do, rejection will remain an insurmountable problem. And even if they do eliminate the most problematic form of inter-species rejection, others exist, and they will have to be dealt with...
...Scientists used cloning methods to locate and remove the GGTA1 gene from the pigs. GGTA1 is one of two genes that trigger the human immune response and resulting organ rejection. If a strain of pig is developed that lacks these genes, scientists believe that they could harvest their vital organs, such as the heart and lungs, and use them successfully in human patients. Such a process could shorten the wait for organ transplants, saving human lives. There are currently almost 80,000 people in need of organs for transplant in the U.S., according to the United Network for Organ Sharing...
...Still, using pig organs as a viable option in transplant cases won't happen anytime soon. Scientists believe it will be roughly four years before pig organs will be available for transplant purposes. The odds were against success in the removal of the first gene copy from the pigs, and are even slimmer in the case of the second. "It was one in 5 million when we had two targets," said Julia L. Greenstein, of Immerge BioTherapeutics Inc. "Now we've got to be twice as good to get the other...