A mosaic of pig and human pancreatic cells may make insulin injections obsolete within five years, according to scientists.
However, many technical and ethnical issues must be tackled before xenotransplantation — from animal to human — becomes routine.
The pigs researchers have in mind have been specially engineered to be compatible with humans. In January, two companies, Scotland’s PPL Therapeutics and U.S.-based Immerge BioTherapeutics Inc., reported they had successfully created pigs that lacked one of the copies of a gene for a molecule that can trigger an organ rejection response. The researchers hope to breed these pigs to produce offspring that lack both copies of the gene.
David Cooper of Massachusetts General Hospital said he believes that in “five years at most” one of the companies will have successfully transplanted pig organs into primates, and revealed some of the “complex interaction between pig and primate.”
Cooper was part of an international panel of researchers who discussed the future of xenotransplantation at the annual meeting of the American Association for the Advancement of Science in Boston Feb. 14-19. While the biotech pigpen may ease the global organ shortage, potential risks in the porcine-human combination remain.
Researchers must address the risk of infection by a pig virus, said Fritz Bach of Beth Israel Deaconess Medical Center. In 1997, Robin Weiss of the University College of London detected a previously unknown pig virus that could infect cultured human cells. In an interview with PBS’ Frontline in 2000, Weiss said the worst-case scenario is a worldwide pandemic, but added that although it was possible, he didn’t expect it to happen.
The risk of viral infection is “the major ethical concern,” said George Annas, a BU bioethicist. “All others pale in comparison.”
According to Bach, Americans have had little opportunity to participate in the xenotransplantation discussion. Annas, however, doubts the public would willingly involve themselves in a discussion about “hypothetical” treatments. “They’re skeptical,” Annas said. “I don’t think they see this as something that’s going to impact their lives soon.”
Xenotransplants have been sporadically performed since 1967 with little success. Although U.S. federal agencies have drafted several sets of guidelines on xenotransplantation, the guidelines remain voluntary. In fact, privately funded experiments do not have to follow them at all.
“As an American, I speak with great trepidation about this field,” said David Cooper.
He stressed that guidelines must be established in individual countries and that an international governing body, such as the World Health Organization, should take on a watchdog role. Bach and another panelist, Edna Einsiedel of the University of Calgary, pushed for more public involvement in the decision-making process. The informed public should define and determine the technology and the precautions that will be used in future xenotransplants, Bach said.
Einsiedel presented a study of Canadians’ opinions on xenotransplantation. The study, which was carried out before the government began to discuss regulations, revealed that Canadians feel the technology needs to mature and the risks need to be better defined before researchers proceeded to clinical trials.
“I fully agree with the Canadians,” said Cooper. “We’re not quite ready. The more discussion we have, the better.”
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