Survival for 271 Days Without Dialysis After Xenotransplantation of a Genetically Modified Pig Kidney, Followed by Successful Engraftment of a Human Kidney
Background
Kidney transplantation is the most ideal treatment for patients with end-stage renal disease. However, the shortage of donated organs has been a challenge faced by the global transplant medicine community for decades. Every year, numerous patients on waiting lists fail to find suitable donors and rely on hemodialysis, leading to worsening conditions or death. While the development of artificial kidneys and regenerative medicine approaches are accelerating, they have been insufficient to resolve the immediate and severe shortage of donated organs.
Xenotransplantation using gene-edited pigs has been steadily researched as a promising alternative to resolve this organ donation imbalance. Pigs are suitable as organ sources because their organ size and physiological functions are similar to humans. However, interspecies immune rejection among species including primates and the risk of zoonotic infections have long been major obstacles. In the past three years, researchers have verified safety through primate preclinical trials and trials on brain-dead donors, finally entering the clinical application stage for living patients.
Key Findings
A research team led by Dr. Leonardo Riella at Massachusetts General Hospital (MGH) in the United States reported in The Lancet that a patient with end-stage renal disease who received a genetically modified pig kidney transplant maintained stable kidney function for 271 days without dialysis. This is the longest dialysis-free survival record among reported cases of living human-to-human heterotopic kidney transplantation in the academic literature to date.
The kidney used by the research team was harvested from a transgenic pig in which porcine antigens responsible for hyperacute rejection were removed and human immunomodulatory genes were inserted. After transplantation into the body, the kidney immediately began producing urine and demonstrated biocompatibility by stably filtering creatinine, a waste product in the body. Through a combination of immunosuppressive therapy and a detailed infection surveillance program, signs of rejection were controlled for nearly nine months.
Subsequently, when functional abnormalities were observed in the transplanted xenograft, the research team retrieved the organ, prioritizing patient safety. The patient then successfully received a human kidney from a deceased donor. This demonstrated that life could be maintained without hemodialysis while the pig kidney was functioning, and that a safe transition to a subsequent human kidney transplant is possible.
Significance and Outlook
This achievement demonstrates that xenotransplantation can establish itself as a safe bridge therapy for organ transplant candidates, rather than merely serving as a temporary life-support measure. It has fulfilled the role of a practical stepping stone by maintaining the patient's systemic health and reducing the risk of cardiovascular complications until a donor becomes available.
Challenges remain to be overcome. It is necessary to elucidate the mechanisms of chronic vascular rejection associated with long-term graft retention and to support precise protocols that minimize the risk of infection resulting from long-term immunosuppression. It is also essential to optimize the combination of gene editing techniques to ensure long-term survival of xenogeneic kidneys for more than one year. If the medical community and regulatory authorities establish standard guidelines, a foundation will be laid to drastically shorten the organ donation waiting period experienced by many patients with chronic renal failure.
The shortage of human kidneys remains a central problem in transplantation, and many candidates die or are removed from the waiting list before an organ becomes available.1 Genetically engineered porcine kidneys have long been proposed to expand the donor pool,2 and over the past 3 years the field has rapidly moved from preclinical models to decedent models to living recipients.3–5 In their Article, Leonardo Riella and colleagues report a porcine kidney xenograft that supported a living human recipient for 271 days—the longest dialysis-free xenograft function described to date—followed by explantation and a subsequent deceased-donor human kidney transplantation.
These clinical results present a concrete treatment pathway for many patients on organ transplant waiting lists. This is because genetically modified pig kidneys can mitigate the vascular damage and worsening of cardiovascular disease that chronic renal failure patients experience during years of continuous hemodialysis. Instead of waiting indefinitely for a deceased donor organ and becoming physically weakened, a multi-stage transplantation strategy—where patients receive a xenograft to maintain their condition and live daily lives for over nine months before transitioning to a human organ—has become clinically feasible. The medical device and pharmaceutical industries have also gained momentum to actively establish infrastructure for producing gene-edited animals and developing specialized immunomodulators for xenotransplantation.