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Dead pig brains bathed in artificial fluid showed signs of cellular life

Nerve cell activity was detected hours after death

DEAD OR ALIVE Ten hours after death, cells in a pig brain normally deteriorate (left). But a new system called BrainEx kept nerve cells (green) and support cells called astrocytes (red) healthy (right).

Scientists have restored cellular activity to pig brains hours after the animals’ death — an unprecedented feat. This revival, achieved with a sophisticated system of artificial fluid, took place four hours after the pigs’ demise at a slaughterhouse. “This is a huge breakthrough,” says ethicist and legal scholar Nita Farahany of Duke University, who wasn’t involved in the research. “It fundamentally challenges existing beliefs in neuroscience. The idea of the irreversibility of loss of brain function clearly isn’t true.”

The results, reported April 17 in Nature, may lead to better treatments for brain damage caused by stroke or other injuries that starve brain tissue of oxygen. The achievement also raises significant ethical puzzles about research on brains that are not alive, but not completely dead either. In the study, the brains showed no signs of the widespread neural activity thought to be required for consciousness. But individual nerve cells were still firing. “There’s this gray zone between dead animals and living animals,” says Farahany, who coauthored a perspective piece in Nature.

The experiments were conducted on pigs that had been killed in a food processing plant. These animals were destined to become pork. “No animals died for this study,” the authors of the new work write in their paper. After decapitation, about 300 pig heads were put on ice and transported to a Yale University laboratory, where researchers surgically removed the brains. Four hours post mortem, researchers put 32 of these brains in an artificial system known as BrainEx — a chamber with specially designed blood replacement fluid that pumps through the blood vessels, delivering oxygen, sugar and other sustaining ingredients at body temperature to keep the brains operating.

During six hours in the BrainEx system, these dead brains showed signs of activity. Oxygen and sugar went into the brain tissue, and carbon dioxide came out, analyses of the fluid showed. That suggested the brains were still busy metabolically. Some of the nerve cells in the hippocampus and prefrontal cortex, key brain areas for complex thinking, appeared healthy under a microscope. And nerve cells could still fire off signals, studies on individual cells in brain slices showed. In contrast, brains that weren’t in the BrainEx system deteriorated.

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