On a recent episode of Causes or Cures, I sat down with transplant surgeon and author Josh Mezrich to explore one of the most unsettling and potentially life-saving frontiers in modern medicine: xenotransplantation.
At its core, xenotransplantation is the use of animal organs (most often from pigs) to address a problem that hasn’t gone away despite decades of progress: there simply are not enough human organs for the people who need them.
Right now, more than 100,000 people in the United States are waiting for a transplant. Some will wait years. Some will never get one. This gap between need and availability has forced medicine into uncomfortable territory, and xenotransplantation is one of the most serious attempts to close it. But as this conversation makes clear, this is not a clean or simple solution. It is layered with scientific uncertainty, ethical tension, and questions that don’t have easy answers.
Dr. Mezrich walks through how we got here, from early and often controversial experiments using primate organs to the current wave of research focused on genetically engineered pigs. Some of it was uncomfortable for me to read. I’m a huge animal advocate. My dad’s a veterinarian. Animal rescue was and is a big part of my life, as is the mantra, “No life is too small.“
Today’s efforts are not just about transplanting organs from one species to another. They involve altering those organs at the genetic level—using tools like CRISPR—to reduce the risk of rejection and improve compatibility with human recipients. What once sounded like science fiction is now being tested in real patients, with cases that have drawn global attention.
But the science is only part of the story.
This episode spends just as much time in the gray areas that often get glossed over. What does it mean to raise animals for the purpose of harvesting their organs? How are those animals treated? And how should we weigh those concerns against the possibility of saving human lives?
Of course, one may argue that factory farms not xenotransplantatio should be our biggest concern when it comes to the ethical treatment of animals, though I’m not convinced that is the comparison we should make.
These aren’t abstract questions. They go to the core of ethics. They sit at the center of whether xenotransplantation becomes widely accepted, or deeply resisted…particularly at a time when there is a push to move away from animal research.
There are also practical concerns that go beyond ethics. The risk of cross-species disease transmission remains a real consideration, even as screening and genetic engineering improve. And there’s a broader question about focus: does investing in animal organs pull attention and resources away from improving human organ donation systems? For example, what about transplanting “less than par” human organs that currently get tossed to maintain the best clinical outcomes possible? (Even though the “less than par” organs would most likely have better outcomes than the current state of xenotransplantation.)
Dr. Mezrich brings a uniquely grounded perspective to this conversation, shaped by his work as a transplant surgeon and his writing in books like Every Living Creature and How Death Becomes Life. He is enthusiastic about xenotransplantation, but lays out the promise and the discomfort side by side, which is exactly where this topic lives.
If you’ve ever wondered what happens when medicine runs out of conventional options, this episode is worth your time.
Xenotransplantation forces a deeper question that goes beyond science: not just what we can do, but what we’re willing to accept in order to save lives.
🎧 Listen to the full episode of Causes or Cures to hear the full conversation with Dr. Mezrich.
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