Scientists have successfully revived dead pig brains—at least partially. A study published Wednesday in Nature reports a team restored some function in brains removed from pigs that had been dead for four hours. The technology still has a long way to go, but might eventually restore damaged brain cells in human patients.
Nenad Sestan, a neuroscientist at Yale School of Medicine, led the team of researchers. Their goal was to determine if circulatory systems in brains deprived of oxygen for more than a couple of minutes (and therefore technically dead) could start working again. The results show that the brain is better at cellular restoration than we thought.
“The study challenges the long-held assumption that large mammalian brains are irreversibly damaged a few minutes after blood stops circulating. It also raises the possibility that researchers could get better at salvaging a person’s brain even after the heart and lungs have stopped working,” Stuart Youngner and Insoo Hyun, experts not involved in the study, wrote in an accompanying commentary in Nature.
For six hours, the BrainEx system, as the researchers call it, mimicked a beating heart. It flooded vessels in the pigs’ brains with a blood-like fluid. The flow restored some blood vessel function and restarted a series of chemical reactions in certain brain cells which are crucial for living organisms to remain alive; some cells even responded to drugs. Tissue samples revealed electrical activity in some neurons—something that would have vanished after death.
None of the 32 pig brains involved in the experiment showed any sign of the global electrical activity associated with consciousness. However, total reanimation, which would essentially bring the brain back from the dead, was never the goal. Reviving consciousness is both currently technologically unattainable and something the global scientific community agrees they should consider thoroughly––like using CRISPR to modify the human genome––before it’s attempted. It would have also gone against animal cruelty regulations that all U.S. federally-funded research must abide by. Although the chances of the brains becoming conscious were very slim, the team still took measures to avoid it. If there was any indication that a brain was becoming conscious, the team would have administered an anesthetic and cooled the brain enough to halt the process.
The discovery that brains can become slightly alive hours after death opens up a trove of ethical dilemmas we must now consider.
“In most countries, a person can be legally declared dead if they show irreversible loss of all brain function (brain death) or irreversible loss of all circulatory function (circulatory death),” wrote Youngner and Hyun. If BrainEx is perfected successfully, it could blur those lines. The new technology could one day mend cells in patients who suffered a stroke or heart attack that cut off their brain’s oxygen supply. It could also make would-be organ donors candidates for brain reconstruction instead.
“Most fundamentally,” Youngner and Hyun wrote, “in our view, it throws into question long-standing assumptions about what makes an animal—or a human—alive.”