By Rohan Kundra

Have you ever imagined what it would be like to have a piece of an animal be part of your body? Ever since the mythologies of the Hindu part-elephant lord, Ganesha, and the Egyptian part-dog god, Anubis, people have imagined the fusion of animal and human (Siems, Chesney et al). But what if this concept left the world of mythology and became reality…welcome to xenotransplantation.

Xenotransplantation is not just a funny word that starts with an X. It is the process of transplanting animal tissues or organs into humans. In 1906, the first xenotransplantation attempt was recorded of a pig kidney to a 48-year-old-woman. However, this attempt failed, as did many more for the rest of the 20th century. Since then, we have learned a lot about the process of xenotransplantation, improving safety and success of this procedure (Cooper, David K C et al). 

The main issue for transplanting animal parts into humans is the risk of tissue rejection. Our immune system is constantly scanning through the body, checking to see if there is any foreign material inside. If it detects something foreign, it mounts an immune response and destroys the invader. This is an extremely powerful system that defends us against disease-causing pathogens, but it also hinders organ transplant. The immune system thinks that the transplanted organ is a foreign invader, and mounts an attack against the organ. Before this problem could be solved, most people who received transplants died within a few hours (Cooper, David K C et al).

Eventually, we were able to design immunosuppressants that could suppress the rejection response. Immunosuppressants can reduce the activity of the immune system, which can prevent it from attacking the transplant. Still, after using the strongest possible immunosuppressants, transplant recipients still only survived for a few weeks after receiving the organ. We then realized that we needed even more than just immunosuppression to make xenotransplantation a viable reality (Siems, Chesney et al). 

In 1992, scientists in the UK created a pig genetically modified with a human-decay accelerating factor (hDAF). Using modified pigs proved more viable when testing in primates. In the past 20 years, new gene modification systems such as CRISPR have been used to create pigs with organs specifically designed to be used for xenotransplantation (Siems, Chesney et al). 

The most recent transplants have proven even more promising. In 2022, a pig heart was transplanted into a human which survived for 2 months. In 2024, a woman received a genetically modified kidney that lasted 130 days before needing to be removed due to immunological rejection, the longest recorded successful xenotransplantation. Most recently, on January 25, 2025, a patient at Massachusetts General Hospital received a pig kidney, and he is living well today (Dance, Amber and Knowable Magazine). 

But why do we even need to transplant animal organs in the first place? Some diseases in humans cause a whole organ to fail, meaning that the only way for the patient to survive is for them to get a replacement organ. When a patient needs to request an organ, they are added to a long transplant list of people waiting for a human donor organ to become available for them. The national transplant waiting list in the U.S. includes over 100,000 people, with a new name added approximately every 9 minutes. Sadly, an average of 17 people die each day while waiting for a transplant. Imagine if we could transplant organs from animals into humans, preventing the need for such a long waiting time for human donors (Dance, Amber and Knowable Magazine)! Maybe we could save 17 lives every day…thanks to xenotransplantation. 

Sources:

Cooper, David K C et al. “A brief history of clinical xenotransplantation.” International journal of surgery (London, England) vol. 23,Pt B (2015): 205-210. doi:10.1016/j.ijsu.2015.06.060

Dance, Amber and Knowable Magazine. “The Future of Transplanting Pig Organs in People.” Smithsonian Magazine, 7 Mar. 2025, www.smithsonianmag.com/innovation/the-future-of-transplanting-pig-organs-in-people-180986182.Siems, Chesney et al. “A Brief History of Xenotransplantation.” The Annals of Thoracic Surgery vol. 113,3 (2022): 706-710. doi:10.1016/j.athoracsur.2022.01.005