Scientists restored partial cellular function in brains removed from pigs hours after slaughter, according to the new study published in the journal Nature. The achievement raises ethical and philosophical questions about death and how we define it.
A person is considered legally deceased when the brain stops functioning or when the heart and lungs are too compromised to supply enough blood to the oxygen-hungry organ, as Sara Reardon explains for Nature News.
But the veil between life and death is perhaps thinner than many have supposed. Since the early part of last century, researchers have tried to keep animal brains alive soon after death by cooling them and keeping them supplied with blood, but with inconclusive results. Other recent studies have shown that genes in some organs remain active well after death. That’s something Yale neuroscientist Nenad Sestan, one of the study’s authors, had noticed as well. Small tissue samples he worked with showed signs of cellular viability, even if the tissue had been harvested hours before.
He began to wonder if it was possible to awaken an entire brain after death. To find out, he and his team obtained the severed heads of 32 pigs from a meatpacking plant. They removed the brains from their skulls and placed the brains in a system they call BrainEx, in which the circulatory system of the organ is pumped full of a nutrient and preservative. It also contains a chemical that prevents neurons from firing, stopping any electrical activity from restarting in the brain.
The team found that neurons and other cells resumed normal metabolic function when hooked up to BrainEx. The team was able to keep one brain functional for 36 hours. In control brains without the synthetic blood, the cells began to collapse.
But that doesn’t meant they “revived” the brains. “At no point did we observe the kind of organized electrical activity associated with perception, awareness, or consciousness,” co-first author Zvonimir Vrselja of Yale says in a press release. “Clinically defined, this is not a living brain, but it is a cellularly active brain.”
Ed Yong at The Atlantic reports that the team showed that neurons in the brains could still fire, but they never sparked back to life. Just in case one of their porcine patients did resume consciousness inside its glass sphere, they had anesthetic on hand to stop the process. But that was not necessary. “The pigs were brain-dead when their brains came in the door, and by the end of the experiment, they were still brain-dead,” Stephen Latham, the Yale ethicist that advised the team says.
So is science on the edge of a world where we can preserve brains in jars after death or shuffle them from one body to another? Not really. Michael Greshko at National Geographic reports that the study shows that brains can be kept intact and working longer than we thought, but not conscious or aware.
That means, instead of ushering in an era of sci-fi body-swaps, the study is more likely to allow researchers to better study brain disorders and diseases. “We’re really excited about this as a platform that could help us better understand how to treat people who have had heart attacks and have lost normal blood flow to the brain,” Khara Ramos, director of the neuroethics program at the United States National Institute of Neurological Disorders and Stroke tells Greshko. “It really enhances our ability to study cells as they exist in connection with each other, in that three-dimensional, large, complicated way.”
The researchers say they have no intention of bringing brains back to consciousness and are taking pains to make sure that does not happen. Instead, they hope to continue working with the BrainEx system to extend the longevity of these brains.
Still, the entire concept is raising legal and ethical questions for many, and brings the long held concept of brain death under the microscope. “We had clear lines between ‘this is alive’ and ‘this is dead,’” bioethicist Nita A. Farahany at Duke University tells Gina Kolata at The New York Times. “How do we now think about this middle category of ‘partly alive’? We didn’t think it could exist.”
In an accompanying commentary to the paper, Farahany and her colleagues suggest that this study necessitates the establishment of immediate new guidelines, like using neural blockers and keeping anesthetic handy during this type of research. They also suggest transparency be at the top of the list and that a committee should be established to draw up guidelines and discuss ethical issues as neuroscience pushes the limits of what we thought was possible.