For many people with kidney disease, the best treatment option is a kidney transplant to replace their nonfunctioning organ. But there are almost 100,000 people on the kidney transplant waiting list, and the average wait time is three to five years. That’s a long time to be on dialysis, and much too long for the sickest patients to wait.
Organs can come from deceased or living donors, but demand far exceeds availability, and we don’t expect this trend to change anytime soon. So, what are patients to do?
As researchers scramble for options, one potential innovation is gaining momentum: xenotransplantation – the transplanting of healthy animal organs, tissues, and cells into humans. For kidney failure patients, recent studies suggest that pigs’ organs might provide the best outcomes.
Why pig kidneys?
For starters, pig and human kidneys are similar in size and function. However, while xenotransplantation using pig kidneys has been studied for several decades, there remain obstacles that must be overcome before we can consider pig-to-human kidney transplantation safe enough for human trials.
Xenografts, which are tissue grafts or organs that are transplanted from one species to another, typically cause more severe immune responses than what we’ve seen in same-species transplantation. In primate trials, researchers have observed non-human primate’s immune systems attacking the sugars and proteins found only on the cell surfaces of pig kidneys. This typically leads to xenograft failure, or the primate’s body being unable to accept the pig kidney, which results in the need for a new transplant, or return to dialysis.
The future of xenotransplantation
Researchers are now genetically engineering pig kidneys to potentially become more suitable for human transplantation in the future. By replacing certain pig kidney proteins with human proteins, researchers hope to reduce the severity of immune responses, and the incompatibilities between humans and pigs, and thus allow for humans to accept pig organs.
Initial data from these tests is promising. Researchers at Emory University reported that a rhesus macaque monkey lived more than 400 days with a genetically engineered pig kidney xenograft, surpassing the previous record of 250 days. Data suggest that further trials will show improved viability.
This was a monumental step in proving the effectiveness of using xenotransplantation for kidney transplantation. To put the technology into perspective, human-to-human organ transplantation was just beginning in the 1960s and 1970s, and now more than 33,000 organ transplants a year are performed in the U.S.
Other organs that have traditionally been transplanted from humans are being researched for xenotransplantation, such as the:
With each advancement, researchers are approaching human trials for xenotransplantation. The ongoing research is extensive, and it is hard to predict when it will become a reality – but it appears to be coming. And when the procedure and recovery are perfect, xenotransplantation will provide a new lease on life for thousands of people on the kidney transplant waitlist.
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