By Naomi Fried
57-year-old David Bennett had been on cardiac support for almost two months and couldn’t receive a mechanical heart pump because of an irregular heartbeat. 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 Bennett a pig heart. A pig heart?? Yes! After much research and work, a surgeon’s team at University of Maryland School of Medicine performed the first Pig to Human heart transplant. Organ transplantation is not novel but this type is a first of its kind.
The first kidney transplant was successfully performed in 1954. This transplant belongs to a category labeled homograft, meaning a transplant from the same species such as from human to human. Following this, transplants were done with other organs as well. The ability to transplant organs has saved many people’s lives, but unfortunately, many who need transplants don’t live to receive them while on the waiting list.
Additionally, some organs are easier to receive than others; for instance, a liver can be donated by someone who is alive and healthy. A small portion of one’s liver is cut out and transplanted into another and the donor will grow back the missing part of the liver. The same goes for kidneys: people can live normally with just one, and thus it is easier to get donations. With a heart transplant, however, this is not the case because unless the donor dies, there is no way for the donor and the recipient to stay alive. According to Gift of Life, the nation’s leading organ procurement organization, 17 people die each day waiting for an organ transplant.
To combat this problem, scientists have been looking into alternatives. One alternative is xenotransplantation. This type of transplantation involves transplanting animal organs into humans. The first pig-to-human heart transplant occurred this past January and was a success. A long road lies ahead, but we are beginning to see the next step in transplantation. Prior to this surgery, the only successful xenotransplantation was when surgeons at New York University Langone Health used kidneys from the same set of GM (genetically modified) pigs in two legally dead people. The organs were not rejected and functioned normally while the deceased recipients were sustained on ventilators.
Animals must be genetically modified since otherwise, the human immune system would reject these organs. CRISPR–Cas9 genome editing was performed on the pigs and this made it easier to create pig organs that are less likely to be attacked by human immune systems. The latest transplant, performed at the University of Maryland Medical Center (UMMC), used organs from pigs with ten genetic modifications.
Although the technology is promising there is still much work that has to be done to receive the perfect genetic modification. There is also an ethical question that must be reviewed and policies that have to be made. Although there is a very good cause at hand, policies concerning animal cruelty must be reviewed.
This technology is not the only one in the works to make organs accessible. Three-dimensional printing of organs is also in the works. In this case, since it is created from the patient’s own cells, the problem of immunological rejection may be circumvented. As of mid-April 2019, an Israeli Scientist, Dr. Tal Dvir, has printed an entire heart including cells, blood vessels, ventricles and chambers. Although this grape-sized heart does not work yet, it is the early stages of this promising technology. Researchers also need to find a way in which they can create bigger cells that compare to those of humans and produce a large enough quantity of them that equals the number of cells in an adult human heart. Following this, clinical trials have to be run, first on animals and then on humans. Although this is far from actualization, here too, there will be ethical questions at hand primarily regarding socioeconomic classes and who will be able to afford to save their lives with that technology.
The first pig-to-human heart transplant was an event that will go down in history; many were very curious to see if the heart will be accepted by the human body. This has been tried many times before but has never been successful until now. The first heart transplant in a human ever performed was by Hardy in 1964, using a chimpanzee heart, but the patient died within 2 hours. Starzl carried out the first chimpanzee-to-human liver transplantation in 1966; in 1992, he obtained patient survival for 70 days following a baboon liver transplant. Many hoped that this transplant would not end similarly. As of now, David Bennet is doing well. “The heart is doing great. We have several cardiologists trying to find any fault in it but they have not been able to do it,” said lead surgeon Dr. Muhammad M. Mohiuddin, Professor of Surgery and Director of the Cardiac Xenotransplantation Program at the University of Maryland School of Medicine. “The heart is contracting vigorously as it should. It has shown no signs of rejection.”
Update: Unfortunately, the patient died on March 9, 2022, and although this is discouraging, the case still taught the scientific community a lot.