Scientists believe the hope of using pig hearts to solve the chronic donor shortage for humans is now truly in reach. The current wait for most patients is six months or longer, a time span many patients don’t have the luxury of surviving. A new review of hearts harvested for pigs indicates that these transplants could vastly expedite the process and begin saving lives as early as next year.
A heart transplant is often the only hope of survival for patients with severe heart failure and certain other cardiac conditions that don’t respond to other treatments. In 2019, surgeons in the United States performed 3,552 heart transplants, according to the United Network for Organ Sharing. But for many, the wait for an available heart is too long. That’s why xenotransplantation has been a longtime goal of researchers and scientists across the globe, as it could mean a readily available supply that could save all lives, not just a lucky few.
The major obstacle in transplanting organs from one species to another is that the new organ risks being attacked by the recipient’s immune system. In the paper, researchers at Massachusetts General Hospital (MGH) discuss the technological advances that have been made in overcoming these obstacles. In particular, they highlight the advancements in genetic engineering and the development of drugs that enabled the successful transplantation of pig hearts into baboons by researchers in Germany.
To mitigate rejection risks, scientists have created genetically engineered pigs with organs that lack specific carbohydrates that serve as the key target for the immune system of primates. Lead author Richard N. Pierson III, MD, an investigator in MGH’s Division of Cardiac Surgery, believes the same process could work for humans.
Pigs have also been engineered to solve another significant issue often connected to cardiac xenotransplantation. Experiments have shown that an incompatibility between proteins in the lining of pig blood vessels and proteins in human blood could cause blood clots. The paper’s authors have actually contributed to research in this area by creating genetically engineered pigs produce a protein called thrombomodulin, which keeps clotting under control.
The studies authors also discuss drug developments that make cardiac xenotransplantation realistic. As they explain, transplant recipients must take drugs that suppress the immune system to prevent organ rejection. “But those drugs don’t work when you put a pig organ into a baboon,” says Pierson, suggesting that conventional immune suppression wouldn’t work in humans, either. To solve for that, Pierson and his colleagues have developed new drugs that suppress the specific immune system molecules and prevent it from attacking organs from pigs.
The paper also addresses concerns about the transmission of infectious disease across species, which have been heightened due to the possible animal origins of the current coronavirus. But Pierson says such an occurrence is highly unlikely and fully believes that pig-to-human heart transplantation is now feasible. He predicts that the first humans could receive transplanted pig hearts by the end of 2021. The full paper is available HERE. (Sources: Feedstuffs, BioWorld, Science Codex)
