The pigs had dead for an hour. The cause: cardiac arrest. But six hours after Yale University researchers hooked their bodies to a machine pumping a nutrient-rich fluid, their organs were showing signs of life again.
Although the organs did not suddenly start working normally, some of the cellular damage caused by the loss of blood flow after death appeared to be reversed. The pigs’ hearts emitted electrical activity. Cells in their kidneys, livers, and lungs were functioning again and showing signs of self-repair. The discovery, published Wednesday in the journal Nature, suggests that cell death may be delayed longer than currently possible. If these processes could be slowed down, more organs could be saved for transplantation.
“This new system showed that not only can we slow down cell damage, but that we can actually activate processes at the genetic level for cell repair,” says Brendan Parent, an assistant professor of bioethics at New York University, who was not involved in the study but wrote a comment in Nature Besides. “This could force us to reconsider what we consider ‘dead’.”
In 2019, the Yale team challenged the idea that brain death is final when they reported that they had partially reanimated pigs’ brains for hours after the animals were slaughtered. For the current experiment, the researchers wanted to test whether the same method, in which a blood substitute is introduced into the animal’s circulatory system, can also be used to revive other organs.
“We restored some function to cells in several vital organs that should have been dead without our intervention,” author Nenad Sestan, a Yale neuroscientist, told reporters in a call Tuesday. “These cells function hours after they shouldn’t, and this tells us that cell death can be halted and their functionality restored in several vital organs even an hour after death.”
Deepali Kumar, president of the American Society of Transplantation and a professor of medicine at the University of Toronto, says that with further refinement, the system could one day be used to expand the pool of human organs available for donors. “There is a significant shortage of organs for transplantation, and we certainly need new technologies that can help improve organ supply,” she says.
In the US, about 106,000 people are on the national transplant waiting list, and 17 people die every day waiting for an organ, according to the Federal Health Resources and Services Administration. Despite the enormous demand, around 20 percent of organs are discarded every year due to poor quality. That could mean they’re too old or damaged, which can happen when organs are cut off from an oxygen-rich blood supply for too long.
The standard practice for preserving organs for transplantation is static cold storage. Rapid cooling of organs after removal reduces their oxygen requirements and can prevent cell death, but does not save every organ. There is also growing interest in using a technique called extracorporeal membrane oxygenation, or ECMO, for patients who cannot be resuscitated to preserve their organs for transplantation. Usually used to support patients whose heart or lungs are severely damaged, an ECMO machine pumps blood out of the body to remove carbon dioxide and add oxygen, and then puts it back into the body.