Scientists Transplant Genetically Modified Pig Heart Into a Human

David Bennett, a 57-year-old patient with terminal heart disease, received the transplant at the University of Maryland School of Medicine last week. Bennett was considered too ill to be placed on the waiting list for a human heart. Given the urgency of his case, Bennett was considered an acceptable candidate for the risky but scientifically-impactful pig heart transplant—a procedure that’s been years in the making.

Researchers and medical professionals have teamed up to perform xenotransplantation (the interspecies transfer of organs, bodily fluids, or other tissue) before, such as with pig kidneys into living humans. Scientists have historically worried that virus genes (known as porcine endogenous retroviruses) could infect human recipients, a concern that only began to fade with the successful transplant of pig pancreas cells into humans back in 2010. Since then, research teams have practiced transplanting pig hearts into baboons in the hope that a similar procedure could someday save a human life.

The heart Bennett received came from a pig developed by Revivicor, a firm responsible for genetically engineering “xeno-organs” prior to transplant. To prepare the heart, Revivicor modified 10 of the donor animal’s genes. Four genes were eliminated, as they would have otherwise produced antibodies typically responsible for transplant rejection or encouraged further growth of the heart following the completion of the transplant. The other six were introduced to human genes to help Bennett’s body have a better chance at accepting the donated heart.

Three days after the procedure, Bennett is reported as having shown signs of acceptance. While immune rejection can take several weeks to set in, a successful first few days can be promising. Bennett was supported by a heart-lung bypass machine following the transplant, as well as by immune-suppressing medications to stave off potential rejection.

“This pig heart has performed very well, beyond our expectations,” said Muhammad M. Mohiuddin, Professor of Surgery at the University of Maryland, in a video for NewScientist. “We have not seen any signs of rejection.”

Should Bennett’s transplant (and others following it) prove successful long-term, xenotransplanted hearts may offer a beacon of health and hope for those who’d otherwise sit on traditionally long waiting lists. Such lists are often six months long, if not longer.