Sourcing organs from genetically engineered pigs is one of the options under development for the production of organs on demand for patients who need transplants. Ethically, growing organs from cells would be a better option, but we live in a world in which animals are widely seen only as tools to be used and consumed; one might hope that our descendants will grow to be better than us in that regard. Major surgery is a high risk undertaking in older people, and the best of all options would be to find ways to spur controlled regrowth and repair in native tissues. That remains more of an aspirational goal at this point, and engineered pigs already exist. Following on from a test of kidney transplants from pigs to brain-dead patients, researchers recently successfully transplanted an engineered porcine heart into a conscious human patient.
The first person to receive a transplanted heart from a genetically modified pig is doing well after the procedure. Physicians and scientists worldwide have for decades been pursuing the goal of transplanting animal organs into people, known as xenotransplantation. Last week's procedure marks the first time that a pig organ has been transplanted into a human who has a chance to survive and recover. In 2021, surgeons transplanted kidneys from the same line of genetically modified pigs into two legally dead people with no discernible brain function. The organs were not rejected, and functioned normally while the deceased recipients were sustained on ventilators.
Xenotransplantation has seen significant advances in recent years with the advent of CRISPR-Cas9 genome editing, which made it easier to create pig organs that are less likely to be attacked by human immune systems. The latest transplant used organs from pigs with ten genetic modifications. The researchers had applied to the US Food and Drug Administration (FDA) to do a clinical trial of the pig hearts in people, but were turned down. The agency was concerned about ensuring that the pigs came from a medical-grade facility and wanted the researchers to transplant the hearts into ten baboons before moving on to people.
But a 57-year-old patient team a chance to jump straight to a human transplant. The patient had been on cardiac support for almost two months and couldn't receive a mechanical heart pump because of an irregular heart beat. Neither could he receive a human transplant, because he had a history of not complying with doctors' treatment instructions. Given that he otherwise faced certain death, the researchers got permission from the FDA to give the patient a pig heart.
For now, transplantation is limited by the supply of pigs as well as regulatory hurdles. There is currently just one company - Revivicor, owned by United Therapeutics - that has suitable facilities and clinical-grade pigs. To make the pig heart used in the transplant, the company knocked out three pig genes that trigger attacks from the human immune system, and added six human genes that help the body to accept the organ. A final modification aims to prevent the heart from responding to growth hormones, ensuring that organs from the 400-kilogram animals remain human-sized.