- Xenotransplantation is the science of transplanting organs from animals such as pigs to humans.
- Scientists have transplanted genetically modified pig kidneys and hearts into humans so far.
- The safety of such procedures and their adverse effects remains debatable.
Organ transplantation is a life-saving procedure. It involves the replacement of a defunct or degenerating tissue of the body to prolong life. Transplants can be done in multiple acquired clinical conditions such as chronic kidney failure and even in congenital conditions such as corneal blindness.
For successful transplantation, there are mainly two requisites. Number one is an immunosuppressive agent which includes drugs such as cyclosporine which tends to lower the body’s immune response and prevent subsequent rejection of the transplanted tissue.
The second requisite is a suitable “graft”. A graft is essentially the tissue that is obtained from the donor and replaced in the body of the recipient. Such grafts can be of three types,
- Autograft: a graft taken from the recipient’s own body. For example skin grafts or bone grafts
- Allograft: a graft taken from the recipient’s close family member. For example an organ such as kidneys
- Xenograft: a graft taken from a different species source than that of the recipient. For example, a genetically modified pig acting as a donor
While the traditional form of organ transplantation allows grafts to be taken from even “recently” deceased patients such as corneal grafts that can cure blindness, the newer methods of using xenografts are still under research specifically in terms of their safety.
The science of xenografting
Doctors have been spreading awareness about the importance of organ donation for ages but only to little avail. There are numerous patients on waitlists of numerous hospitals around the world suffering due to a lack of suitable grafts available for transplantation.
Hence the lack of an adequate number of organ donors tends to emerge as the primary cause of shifting towards xenografting.
However, xenografting does not involve obtaining organs from any animal. The scientists use “GMO”(genetically modified organisms) whose DNA is modified accordingly via in-vitro or laboratory-based biotechnological applications to suit our purpose.
Also xenografting wasn’t immediately outlined in human trials. The first recorded attempt at xenografting was observed when a genetically modified pig liver was transplanted into non-human primates as an experiment. According to the scientists, the recipient baboon went on to live for almost two years despite the basic immunological differences between the two species.
Xenografts in humans
In January 2022, doctors at the University of Maryland Medical Center successfully transplanted a genetically modified pig heart into a 57-year-old patient named David Bennett.
Bennet was suffering from a terminal disease which had let his plea on the waitlist for a human heart be denied as is often decided in the case of an older patient. This move allowed him to take a shot in the dark and consent to the unique surgery following which he lived well for around 2 months without showing any signs of graft rejection. He passed away in March 2022.
In October 2021, surgeons in New York announced that they had successfully transplanted a pig’s kidney into a brain-dead person. A team also tested with a complex graft known as “them kidney” which includes a pig thymus with each kidney on two people, who had been confirmed as dead. Scientists studied the role of the kidney in preventing graft rejection in the recipient’s body and the safety of xenotransplantation.
Safety of xenotransplantation
So far scientists have managed to successfully conduct studies only on dead or brain dead patients. Such patients’ data cannot be considered absolute since even while being on life support systems their metabolic functions might show distorted results.
Even though the organ graft used is from a GMO whose genome is modified to lack the genes which trigger graft rejection, the greatest concern scientists face is the probability of developing late immune reactions to the foreign graft. Such reactions include weak pulse, itchy skin, edema of the face, respiratory distress, pale skin, and confusion.