They’re not true zombies — but these pig brains showed signs of cellular life long after the animals had died.
Scientists have kept cells alive in the brains of dead pigs. This first-of-its-kind feat was done with a sophisticated system of artificial fluid. The pigs had died four hours earlier at a slaughterhouse.
“This is a huge breakthrough,” says Nita Farahany. An ethicist and legal scholar at Duke University in Durham, N.C., Farahany wasn’t involved in the research. “It fundamentally challenges existing beliefs in neuroscience,” she says. The research hints that in some cases, the loss of brain function doesn’t have to be permanent. The findings appeared April 17 in Nature.
In the study, the brains showed no signs of consciousness. For that, they’d need more widespread activity. But individual nerve cells were still firing. “There’s this gray zone between dead animals and living animals,” says Farahany. She coauthored another piece in Nature offered as a commentary on the new study.
The goal was never to create true zombies. Instead, the results may one day lead to better treatments for brain damage. Strokes and other types of injuries can harm brain tissue by starving it of oxygen. The study also raises major ethical questions about research on brains that are neither alive nor yet completely dead.
How to make an undead brain
“No animals died for this study,” the authors of the new work write in their paper. They did the experiments on pigs that had been killed in a food processing plant. These animals were destined to become pork.
An artificial fluid flows through this pig brain after death. It kept the cells oxygenated and fed. CREDIT: Z. Vrselja et al/Nature 2019
After death, the heads of some 300 pigs were put on ice. They they were sent to a lab at Yale University in New Haven, Conn. There, researchers cut out the brains.
Four hours after the animals had died, researchers put 32 of these brains in an artificial system called BrainEx. It includes a fluid designed to stay at the animal’s body temperature and replace its blood. The fluid moves through the blood vessels, carrying oxygen, sugar and other ingredients needed to keep the brain cells fed.
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. That suggested some cells in the brains were still alive. Some of the nerve cells in the hippocampus and prefrontal cortex looked healthy under a microscope. These are key brain areas for complex thinking. And studies on brain slices showed that individual nerve cells could still fire off signals. In contrast, brains that weren’t in the BrainEx system broke down over those six hours.
Ten hours after death, cells in a pig brain have deteriorated (left). But a new system called BrainEx kept cells healthy. In the image on the right, nerve cells are green, and support cells called astrocytes are red. CREDIT: Stefano G. Daniele, Zvonimir Vrselja/Sestan Lab/Yale School Of Medicine
