Scientists at Yale University were able to revive cells in pigs a full hour after their deaths, groundbreaking research that could potentially extend human lives but also raises ethical questions.

An hour after stopping the hearts of anesthetized pigs, the researchers restored blood circulation and other cellular functions by pumping a cell-protective fluid to organs and tissues using a device similar to a heart-lung machine. 

After the heart stops beating, a lack of blood flow, oxygen and nutrients quickly begins to destroy the body’s cells and organs. But the researchers, whose work was published Wednesday in the journal Nature, set out to determine how long they might be able to stall that decay in pigs.

“All cells do not die immediately, there is a more protracted series of events,” David Andrijevic, associate research scientist in neuroscience at Yale School of Medicine and co-lead author of the study, said in a news release. “It is a process in which you can intervene, stop, and restore some cellular function.”

If the treatment worked in humans, it could someday extend the lives of organs, expand the availability of donor organs for transplant and treat organs or tissue damaged by ischemia — inadequate blood flow — during heart attacks or strokes.  

The study builds upon earlier research, published in 2019 and also conducted by Yale scientists, that restored circulation and certain cellular functions in the brain of a dead pig using a solution called BrainEx.

“If we were able to restore certain cellular functions in the dead brain, an organ known to be most susceptible to ischemia, we hypothesized that something similar could also be achieved in other vital transplantable organs,” said Nenad Sestan, a neuroscience professor at Yale who led both studies.

In the latest research, scientists used a modified version of BrainEx called OrganEx. The experimental fluid contains compounds that can promote cellular health and suppress inflammation.

Six hours after the treatment, the researchers found that certain key cellular functions were active — including in the heart, liver and kidneys — and that some organ function had been restored, including hearts beating.

“We were also able to restore circulation throughout the body, which amazed us,” Sestan said.

Vrselja said that under a microscope it was difficult to distinguish between a healthy organ and one that had been reactivated using OrganEx. 

The researchers also observed involuntary and spontaneous muscular movement in the pigs’ heads and necks, indicating some motor function was preserved, Sestan said. There, however, was no organized electrical activity in the brain to suggest the pigs, which remained under anesthesia for the entire experiment, were ever conscious, the study’s authors said.

The scientists said that additional studies are needed to better understand the restored motor functions in animals and that rigorous ethical review from outside scientists and bioethicists is required.

“There are numerous potential applications of this exciting new technology,” said Stephen Latham, director of the Yale Interdisciplinary Center for Bioethics. “However, we need to maintain careful oversight of all future studies, particularly any that include perfusion of the brain.”

Latham emphasized to The New York Times that the technology is “very far away from use in humans.”