From Pigs to Humans

What you're witnessing here is an unprecedented event: a pig heart beating inside a human body. This groundbreaking experiment not only involves gene editing but also a surprising ingredient—cocaine. Let's delve into the fascinating world of xenotransplantation and explore the potential it holds for solving the global organ shortage.

Xenotransplantation refers to the transfer of cells or tissues across species. Despite sounding like science fiction, it's not entirely new. For the past three decades, pig heart valves have been successfully replacing worn-out human heart valves. This is because pig hearts share striking similarities in structure and size with their human counterparts. However, replacing an entire human heart with one from a different species ventures into uncharted territory.

One significant challenge in xenotransplantation lies in our immune systems. Pig cells possess surface structures that our bodies perceive as non-human, triggering a response called graft rejection. This rejection can even occur with human-to-human organ transplants.

The urgency for whole hearts is immense. Heart disease stands as the leading cause of death worldwide. Even in regions with sufficient resources for valve replacements or heart transplants, there simply aren't enough organs available. In the United States alone, thousands of individuals are on the waitlist for a new heart, and an average of 17 people on organ transplant waitlists lose their lives every day.

Until now, human hearts have been the only viable option for whole organ transplants. However, pig hearts show promise in alleviating this problem. Yet, what about the persistent immune response? Genetic modification might hold the answer. The same company responsible for cloning Dolly the sheep has been genetically engineering pigs specifically for organ transplantation. In 2021, these pigs successfully transplanted kidneys into two legally brain-dead individuals being kept alive on ventilators. Encouraged by these results, researchers proceeded to focus on hearts.

Through gene-editing technology, scientists made ten major genetic modifications to these pigs. They "knocked out" three pig genes responsible for triggering the human immune response, removed a tissue proliferation gene, ensured the pig heart wouldn't continue growing after transplantation, and introduced six human genes to potentially enhance immune acceptance.

Furthermore, several other innovative techniques were employed, such as administering an experimental drug to suppress the recipient's immune system and using a new machine to circulate fluid through the heart while awaiting transplantation. Remarkably, this fluid contained standard cortisol and adrenaline, along with the unconventional addition of cocaine.

Although the exact mechanism is unclear, cocaine seems to assist in maintaining the heart's readiness for transplantation between pigs and humans. Securing approval to use the drug proved challenging, but the team believes it played a beneficial role. Nevertheless, xenotransplantation carries the risk of disease transfer between species, as pigs harbor various viruses within their genomes. Scientists made precise alterations to remove these viruses, aiming to reduce the likelihood of disease transmission. However, only time will reveal the true extent of their success.

Now, the question arises: who would willingly accept this extraordinary procedure? Meet 57-year-old David Bennett, the recipient of the pig heart. Unfortunately, Bennett's terminal heart disease left him with no other options; it was either this experimental surgery or death. The FDA granted emergency approval for this specific procedure, making Bennett the sole patient eligible for the surgery.

While the scientists continue testing the procedure on baboons, their ultimate goal is to proceed to clinical trials involving even more human subjects. Undoubtedly, this breakthrough raises profound ethical questions. The prospect of "farming" hearts in this manner could provide a reliable supply of organs when patients need them most.

However, raising intelligent animals like pigs solely for organ donation has sparked outrage among animal rights activists. Moreover, from a medical ethics standpoint, offering a potentially dangerous procedure with numerous unknowns to terminally ill individuals, essentially making them human guinea pigs, is a complex dilemma.

As of February 2022, David Bennett appears to be progressing well, showing no signs of rejection and retaining his ability to breathe and speak independently. It is too early to determine the long-term success of the surgery, but it undoubtedly marks an exciting initial step towards addressing the global organ shortage. Who knows? Perhaps in the future, genetically modified xenotransplantation could become the norm for other organs, bringing hope to countless lives in need.