Genetically modified pig hearts transplanted into baboons can function in the long-term through a refined procedure, reports a paper published online this week in Nature. Although further testing is required, this approach - the first to consistently produce successful outcomes - represents a major step towards the clinical use of pig donor hearts in human patients.

Transplantation is the only long-term intervention available for patients with terminal heart failure. However, the supply of viable donor organs is insufficient to meet present clinical demand. The use instead of genetically-modified pig hearts has been proposed as a potential solution to this deficit, with pre-clinical tests having been undertaken in baboon models. However, to date the longest survival duration of a baboon recipient of a transplanted, life-supporting pig heart had been 57 days on one occasion.

Bruno Reichart and colleagues now demonstrate that longer-term transplants of life-supporting pig hearts into baboons can be repeatedly achieved. The authors refined the procedure with three successive groups of transplant subjects (16 baboons in total). They achieved successful long-term transplantation in the final group by keeping the hearts oxygenated through the circulation of blood (rather than static cold storage) during the transplant process, and preventing the transplanted organs from detrimentally enlarging by lowering the baboons’ blood pressure and using compounds known to control cell growth. Four of the five baboons in the final group remained healthy for at least 90 days (when the experiment was terminated), including one that was in good health after 195 days.