Pig heart beats in baboon for two years – US expert reaction

International scientists may have overcome an key obstacle in xenotransplantation, successfully transplanting a heart from a pig into a baboon which survived for two years, 

An effective immune-suppressing drug therapy has enabled the longest-to-date survival of a heart transplant from a pig to a baboon, published in Nature Communications this week. The implanted pig organ did not replace the baboon’s heart, but was instead connected to the baboon’s circulatory system, which allowed it to beat for more than two years.

The heart came from a previously established line of donor pigs with three genetic modifications that allowed for a degree of immune tolerance in recipient baboons, close relatives of humans.

Read more about the research on Scimex.org.

The US-based Genetic Expert News Service collected the following expert commentary. Feel free to use these quotes in your reporting.

Dr. Kenneth Bondioli, Professor of Animal Sciences, Louisiana State University (webpage):

“I think this paper represents progress towards clinical application of xenotransplantation.  Survival times reported here are approaching clinical relevance especially for ‘bridge transplants’ until a human organ becomes available.  I think the combination of genetic modification and immunosuppressive regimen reported here is particularly important.  Clinical success of xenotransplantation will rely upon a combination of genetic modification and immunosuppressive regimen and both must be developed.  It is likely that the best combinations will occur when the immunosuppressive regimen is tailored for the specific genetic modification rather than blanket suppression of the immune response.”

Dr Max Rothschild, Distinguished Professor in Agriculture and Life Sciences, Iowa State University (webpage):

“Too few organs exist from humans to provide all the transplants required in the US and other places in the world. In addition, to be transplanted human organs must have the same or nearly the same ’tissue type’, combined with medications that prevent rejection of the transplanted organs.  So generally speaking, under the best situations both the right genetics and anti-rejection medicines are needed. 

“One long term way to supplement human to human organ transplants would be to use organs of similar size from a domestic species.  This could only happen if they were genetically engineered so they expressed human antigens.  Research using pig organs, hearts in particular, have been ongoing for some time. They are tested in primate (baboon) models.  In the past all animals in these types of experiments have died from delayed graft rejection in  periods of 179-236 days.  The combination of genetically engineered hearts and new drug therapy discussed in this research has allowed the median survival to be 298 days and in one case 945 days; a considerable improvement.

“Does this bring us any closer to human trials? The simple answer is yes but the finish line is still quite far away. However, progress like this allows for other strategies and combinations to be examined and may eventually point the way to eventual trials in humans.”

Dr Willard Eyestone, Research Associate Professor, Reproductive Biology / Biotechnology, Virginia Tech (webpage): 

“This paper presents some very encouraging data on the development of xenotransplantation for organ replacement.  Here, genetically-modified pig hearts were transplanted into baboons, where they functioned for nearly 3 years in one case, much longer than previously reported.  Success was attributed to genetic knockout in pig hearts of alpha 1-3 galactosyltransferase and knock in of of two thrombomodulatory proteins, plus an aggressive immunosuppressive regime in the baboons.  The good news emanating from these findings is that the system used to achieve these results, perhaps with some modifications, should be applicable to early-stage human trials using pig hearts with similar genetic modifications. Refinement of these promising results should go a long way to translating xenograft technology for human medicine, and relieve the vast shortage of human hearts, kidneys and livers required to save the many patients who die every day waiting for an organ that never comes.”