Japan faces one of the most severe organ donor shortages among developed nations. According to the Japan Organ Transplant Network, approximately 16,000 people are currently waiting for organ transplants, yet only about 4% receive the organs they need each year. When comparing organ donor rates per million population internationally, Spain leads with 46.03 donors, followed by the United States at 44.50, while Japan registers a mere 0.88, a stark contrast that highlights the severity of the issue.

The kidney transplant waiting list is particularly critical, with over 14,000 patients awaiting a transplant. The average waiting period extends to approximately 15 years, during which many patients continue dialysis treatment while their health deteriorates. Tragically, an estimated eight patients die each week while waiting for a transplant that never comes.

A University Startup Takes on Xenotransplantation

Amid this challenging landscape, a technology called "xenotransplantation," the transplantation of organs from animals such as pigs into humans, has emerged as a potential game-changer. Pormedtec, a startup spun out of Meiji University based in Kawasaki City, is targeting Japan's first clinical trials of pig-to-human organ transplantation by fiscal year 2027.

The company has partnered with US biotechnology firm eGenesis, which provides genetically modified pig cells engineered to reduce human immune rejection. Pormedtec produces clone pigs domestically using these cells, establishing a complete production pipeline in Japan.

In February 2024, three pigs specifically bred for xenotransplantation were born in Japan for the first time. These animals carry 10 genetic modifications designed to minimize immune rejection responses. The company plans to open a specialized breeding facility in Osaka Prefecture in late 2027, implementing automated feeding and cleaning systems along with sensor-based health monitoring to minimize human-pig contact and reduce infection risks.

Breakthrough Results from US Clinical Research

Clinical research in the United States has achieved remarkable progress. In September 2025, eGenesis announced that a patient who received a genetically modified pig kidney has survived more than seven months, setting a new world record for xenotransplant organ survival. This demonstrates that transplanted pig organs can function long-term in the human body.

Other companies are also advancing toward clinical applications. United Therapeutics received regulatory approval for kidney transplant clinical trials, and multiple organizations are actively pursuing human trials. In March 2024, Massachusetts General Hospital performed the world's first pig kidney transplant into a living patient, marking a historic milestone.

Technological Advances and Remaining Challenges

The feasibility of xenotransplantation has dramatically improved due to revolutionary advances in genome editing technology. Pig cells naturally express carbohydrate antigens on their surface that the human immune system recognizes as foreign, previously triggering hyperacute rejection that destroyed transplanted organs within minutes.

Modern genome editing tools like CRISPR-Cas9 now enable researchers to knock out genes responsible for these rejection-triggering antigens while introducing human genes that help evade immune detection. Scientists have created pigs with up to 69 genomic edits, achieving survival periods of up to 758 days in cynomolgus monkey transplant recipients.

However, significant challenges remain. The risk of porcine endogenous retroviruses (PERVs) potentially infecting human recipients continues to concern researchers, necessitating stringent health management of donor pigs. Long-term immune responses and interactions between pig-derived factors and human physiology also require further investigation.

Prospects and Social Considerations in Japan

Professor Hiroshi Nagashima of Meiji University, founder of Pormedtec, emphasizes that "Japan has fewer donors than other developed countries. The need for xenotransplantation may actually be higher here than in the US, where trials are progressing." The company's clinical trial goal is to achieve six months of dialysis-free survival post-transplant. If successful, this could enable various clinical applications, from lifetime organ use to bridging patients until human donor organs become available.

Beyond technical challenges, gaining social acceptance remains crucial for xenotransplantation's implementation. Psychological resistance to receiving animal organs and ethical concerns about using animals for human benefit require careful dialogue through patient and public symposiums.

Additionally, a team from Jikei University School of Medicine and the National Center for Child Health and Development is planning clinical research to transplant pig kidneys into fetuses with Potter syndrome, a condition where kidneys fail to form properly, representing a uniquely Japanese approach to the technology.

What Does Organ Transplantation Look Like in Your Country?

In Japan, the severe donor shortage has intensified expectations for xenotransplantation as a new option. For patients enduring years of dialysis while waiting for transplants, and for their families, these technological advances represent profound hope.

At the same time, ethical debates about using animal organs and concerns about unknown risks persist. What is the organ transplantation situation in your country? What opinions exist about animal-to-human organ transplants? We would love to hear your thoughts and perspectives on this groundbreaking medical frontier.

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