Nearly 3,400 organ transplants were facilitated in 2020/21. There is still, however, an estimated 7,000 people on the UK organ Transplant Waiting List. Donating an organ can save someone’s life, but sadly it is difficult to find a match that the body will accept as its own. Last year in the UK over 470 people died whilst waiting for an organ transplant, a shocking figure which illustrates the need for more human donors, or an alternative.
To successfully donate an organ, the blood and tissue type must match the patients, which is why living donations often come from close relatives. Donations from close relatives reduces the risk of the body rejecting the organ, which occurs when the body identifies the new organ as foreign, and the immune system attacks it.
The study of animal to human organ transplantation, known as xenotransplantation, has been studied for many years as an alternative to the human organ shortage. Pigs are often the animal of choice as they are anatomically similar to humans. In October 2021, surgeons in New York successfully attached a pig kidney to a human patient and witnessed the organ function normally for 54 hours. In short, the kidney quickly started producing urine.
This was the first successful pig kidney transplantation to a living human patient, which wasn’t instantly rejected. The patient was brain-dead but kept alive on a ventilator as consented by her family. Robert Montgomery, the surgeon at NYU Langone Health who led the surgical team said, “In a time of profound grief [the patient’s family] found a way to help their loved one realize her desire to give a gift to humanity at the time of her death”. The kidney functioned “just like a human kidney” for 54 hours, after which the monitoring ended due to ethical considerations.
Such procedures have previously been completed on primate subjects, but this is the first of its kind on a living human body. This breakthrough marks a life-saving new chapter in the world of organ donations, with the end goal being a solution to organ shortage. The reason transplantation had been previously rejected in primates was due to the presence of a specific sugar molecule.
The sugar molecule, named alpha-gal, is found in pig blood vessels which are found in abundance in the pig’s kidney. The human immune system has specific antibodies which identify the sugar molecule as non-self, triggering the originally detected aggressive immune response. In the recent decades, scientists have found a way to genetically engineer the pig genome to prevent instant rejection. Genetic removal of the alpha-gal molecule allowed pig organs to be successfully transplanted onto primates, however the surgery had never been attempted on a human body.
So, what is next? Although this study provides the crucial first step to making pig-grown organs accessible, it is necessary to prove they can stay in the human body for not just 54 hours, but for months to years. A potential world where pigs are harvested for their organs raises a multitude of ethical questions.
Supporters of xenotransplantation argue that providing an expansion for organ supply is worth any injury to pigs, but the ethical question remains. For now, however, an NHS spokesperson suggested the main priority remains finding human donor matches. This leading-edge surgery is an exciting starting point for alternatives to the clearly limited current donor programme.
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