Whenever a scientist talks about the potential of xenotransplantation, using tissue or cells from genetically modified animals to correct a human ailment, the conversation usually turns quickly to pigs. Pigs have long been spotlighted for hearts that bear a resemblance to their human counterparts. Genetic modification make them ideal subjects to develop tissues that can be used to potentially cure diabetes or serious brain diseases like Parkinson's. And Dr. Burcin Ekser and Dr. David K. C. Cooper from the Thomas E Starzl Transplantation Institute at the University of Pittsburgh have been discussing their work on xenotransplantation in The Lancet.
An animal study is underway now that transplants pig pancreatic islets into nonhuman diabetic primates, with more studies being planned for the future. Investigators are working now on guarding the pancreatic islets from the immune system, to protect them from almost certain destruction as well as avoiding the need for powerful immunosuppressants to keep the host from rejecting the transplant.
Transplanting pig neuronal cells into monkeys with Parkinson's disease also improved locomotor function. And while it triggered lymphoproliferative disease in some of the primates, the scientists say that once that safety issue is resolved they may be ready for a small human study involving patients who were not responding to therapy.
But not everyone is satisfied that the field has cleared all the safety hurdles standing in the way of human studies. "I don't think the risk issues have been resolved," UCL's resident retrovirus expert Robin Weiss tells The Independent. "That doesn't mean clinical trials shouldn't go ahead but there would need to be very close monitoring of patients to ensure they were not picking something up from pigs."