This year is tens of thousands
of Americans hoping for a transplant will eagerly await the call telling them that an organ has been found. Some of the patients who are sick with congestive heart failure will wait for a heart. Those with end-stage renal disease who become persistent with dialysis will wait for a kidney. Others with liver disease or failing lungs will also wait their turn. There are currently more than 100,000 people
which is on the waiting list for an organ transplant, according to the United Network for Organ Sharing. In 2021, only about 41,000 organ transplants were performed – the highest annual number since at least 1988, according to UNOS
. Due to the high demand, some patients will continue to wait. Others will eventually die. More than anything else, the problem is lack of donor organs.
Over the next half century, while surgical techniques have become very sophisticated for preserving and transplanting solid organs such as the heart, kidneys, lungs and liver, some of the greatest advances have promoted the development of new drugs that enable patients to live for many years without the risk of organ rejection. Now the majority of heart transplant recipients survive at least 10 years
While the safety and effectiveness of transplantation has improved immensely over the last several decades, the supply of donor organs remains a problem. There are several barriers to organ donation, including family reluctance and a general lack of social education about the life-saving nature of organ transplantation. The net result is one eternal lack
of donor organs. The groundbreaking implication of Mr. Bennett’s recent surgery is not only what it does for heart transplants, but also what it does for the supply of organs for transplant surgery as a whole.
Xenotransplantation, transplantation into a human by an organ from a non-human animal, has previously been attempted without success. In 1984, Stephanie Fae Beauclair (who was called Baby Fae) was born with hypoplastic left heart syndrome
. In an attempt to save her life, she underwent heart transplantation with the heart of a baboon. She died of organ rejection 21 days after surgery.
For a non-human donor organ to function adequately in a human host, it must be anatomically similar (to allow surgical implantation), function well in a human environment, and not be rejected. (Graft rejection is a risk that all transplant recipients face, but it is especially challenging when the donor organ comes from a non-human source.)
Although the heart of an adult pig anatomically resembles a human heart, researchers at the University of Maryland changed to Bennett’s surgery. 10 gener
in the pig. Some pig genes were disabled or “knocked out” to prevent acute rejection. Another gene was modified to prevent the donor heart from continuing to grow to an unacceptably large size after transplantation. Several human genes were given to the pig to prevent coagulation abnormalities in the new heart. As is also required for this type of transplant, powerful anti-rejection agents were also given.
We know relatively soon whether the daring operation will restore Bennett’s health. Although his recovery is uncertain and perhaps even a long shot, it is certain that the door to using biomanipulated non-human organs has been opened – and with it the promise of an almost unlimited supply of donor organs could follow. While the road ahead is certainly filled with new physiological, technical and even ethical challenges, we can one day look at this courageous procedure that we now see in Dr. Christaan Barnard’s first heart transplant.