Scientists Partially Revive Pig Brains Hours After Death

by Angela Cui ’21

For centuries, people have thought that once the heart stopped beating and the human stopped breathing, life was over. The developments of modern medicine, including devices such as defibrillators, have drastically changed these ideas, but brain death has always remained the final, unarguable verdict of death. However, for the first time in history, a group of scientists from Yale University have restored cellular function in pig brains hours after death by devising a system called BrainEx.

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The name BrainEx is short for “brain ex vivo,” or “brain out of the living,” and consists of three parts. First, scientists formulated a solution mimicking fluids in the brain and stored the solution at 37 degrees Celsius, close to body temperature. Next, a device pumped the solution through the brain, a process similar to perfusion where fluids are passed to organs or tissues using artificial blood pumps. Finally, the scientists obtained the pig heads from a meatpacking plant nearby, isolated the brains, and applied the BrainEx technology four hours after death. Researchers observed the brains for four hours and compared them to a control group. This process restored basic cellular function, including the ability for cells to produce energy and remove waste. 

“We found that tissue and cellular structure is preserved, and that cell death is reduced,” reported neuroscientist Nenad Sestan of Yale University. “In addition, some molecular and cellular functions were restored, including glial and vascular response to stimuli, as well as spontaneous synaptic activity along with active global metabolism.”

However, the brain did not show any signs of organized electrical neural activity required for awareness— in fact, consciousness was never one of the researchers’ goals, and anesthetics as well as temperature-reduction methods were prepared in case any signs appeared. 

“[The researchers] agreed in advance that experiments involving revived global activity couldn’t go forward without clear ethical standards and institutional oversight mechanisms,” said Stephen Latham, director of Yale’s Interdisciplinary Center for Bioethics.

The scientists also stated that it was unclear if the BrainEx system can be applied to human brains after death. BrainEx is drastically different from the real life situation, as the solution used lacks many of the components found in human blood, including the immune system and other blood cells. BrainEx is also unlikely to revive a dead animal, as the system requires the brain to be localized from the rest of the body. 

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Regardless, the development of BrainEx introduces many new opportunities for researchers to better study the brain and understand brain disorders, since, previously, scientists were only able to study the brain using small samples of brain tissue. Furthermore, although BrainEx currently has no clinical applications, this new method of research may one day help researchers find a way to treat brain disorders and diseases, such as reviving a brain after a stroke. However, this development also raises many controversial ethical questions for the future.

For one, the line between the brain being a dead tissue or a live animal research subject becomes blurred because of the possibility that the brain could become conscious. Furthermore, since the brain can become aware, some argue that the BrainEx research is not ethical and should not be continued. However, these ethical implications must be balanced against the promise that BrainEx holds to further brain research. 

As science and technology continue to advance, these ethical questions will only increase in number and frequency, and we will be forced to ask ourselves, “Where should we draw the line?”