A patient’s failing heart was replaced with the heart of a genetically engineered pig, known as the process of xenotransplantation, in a groundbreaking operation at the University of Maryland Medical Centre in Baltimore, United States. But he died two months later on Tuesday (March 8).
On January 10, the successful transplantation procedure was in news, just days after doctors performed it on 57-year-old David Bennett. He was suffering from severe arrhythmia, a life-threatening illness that affected the rhythm of his heartbeats.
On December 31, 2021, the US Food and Drug Administration (FDA) gave emergency authorization for the experimental technique. Bennett had been found ineligible for both a conventional and an artificial heart transplant by major transplant centers.
What is xenotransplantation?
According to the FDA, xenotransplantation is “any procedure that involves the transplantation, implantation or infusion into a human recipient of either (a) live cells, tissues, or organs from a nonhuman animal source, or (b) human body fluids, cells, tissues or organs that have had ex vivo contact with live nonhuman animal cells, tissues or organs”.
Xenotransplantation could be a viable alternative to the clinical transplantation of human organs. It is in high demand around the world.
Human xenotransplantation of the heart was first attempted in the 1980s. Stephanie Fae Beauclair, also known as Baby Fae, was an American baby who was born with congenital heart disease. Baby Fae then had a baboon heart transplant in 1984.
The procedure went well. But Baby Fae died just a month after the transplant when her immune system rejected the baboon’s heart. Despite this, Baby Fae was able to survive the xenotransplantation for a considerably longer period than in previous tests.
If found to be compatible in the long term, xenotransplantation could assist give an alternative supply of organs to patients suffering from life-threatening conditions. Bennett initially responded well to the pig’s heart transplant, and he exhibited no signs of rejection for several weeks. Bennett spent time with his family, went to physical therapy, and watched the Super Bowl, according to hospital authorities quoted by The New York Times.
It was not immediately obvious whether his death was a cause of his body rejecting the xenotransplanted heart.
What is the significance of a pig’s heart?
For more than 50 years, pig heart valves have been useful to replace damaged valves in people. The domesticated or farmed pig (Sus scrofa domestica) as a donor animal for xenotransplantation has various advantages.
Pigs have anatomical and physiological characteristics that are similar to humans, and pig breeding in farms is common and cost-effective. Furthermore, several different pig breeds are farmed. Thus, allowing the size of the harvested organs to match the precise demands of the human recipient.
Genetically engineered pig
The molecular incompatibility between pigs and humans can cause several immunological issues after the transplant, leading to xenograft rejection. To avoid this, genetic engineering is useful to alter the pig’s genome in such a way that the human recipient’s immune system does not recognize it. Thus, the processes that lead to xenograft rejection are not active
Bennett’s donor pig had undergone ten genetic alterations to ‘deactivate’ or knock-off four pig genes and replace them with six human genes. A pig named “GalSafe” was in the use of the study. A gene that codes for Alpha-gal (a sugar molecule) was eliminated. Alpha-gal can provoke a severe immunological response in humans. GalSafe pigs have undergone comprehensive testing and have received USFDA approval for use in pharmacology.
Revivicor, a regenerative medicine business, provided the pig. The researchers extracted the pig’s heart the morning of the procedure and placed it in a special machine to keep it alive until the surgery.