A pig and his nose pressed against a fence.
Reuters/Michaela Rehle
The work in pigs opens the door for life-saving clinical applications in the future.
NOT DEAD YET

Pig brain cells revived after death show that the brain may be more resilient than we thought

By Katherine Ellen Foley

The brain is the hardest-working organ in the body with the most daunting tasks: controlling the rest of our internal organs, our voluntary and involuntary movement, and creating consciousness. It’s a huge amount of responsibility for a 3 lb (1.3 kg) grey blob, but it handles them expertly. For all its might, though, the brain has a molecular Achilles heel: an oxygen dependency.

All organs need blood to routinely deliver oxygen to them. The brain, however, is the neediest. Within seconds of interrupted blood flow to the brain, the body will suspend consciousness in an effort to save energy. Ideally, gravity will then take over as the body goes horizontal, allowing blood to flow more freely towards the brain. If that doesn’t work, brain cells die within minutes, which could lead to catastrophic damage, or even a person’s death.

However, brain-cell death as a result of oxygen depletion may not be as fast or as permanent as scientists previously thought. In a first, an international team led by scientists at Yale University showed it may be possible to reanimate brain cells after death, according to a paper published today in the Nature.

The researchers worked on the brains of 32 pigs that had been killed and decapitated at a food-processing plant. Applying a system called BrainEx, the scientists were able to get cells in these brains to carry out some normal function for six hours. Although these brains never regained full working capacity or consciousness, the development opens doors for future treatments for events that acutely choke the brain of oxygen, like stroke.

First, the brains and their blood vessels were carefully removed from the pigs’ bodies. Then, after raising the temperature of the brains to 37°C (98.6°F), the normal body temperature of pigs, scientists flushed them with a synthetic solution that works like blood. The brain cells took in oxygen and glucose and flushed out carbon dioxide, which suggests they were using energy. Some brain cells even started signaling one another. These functions are both typical in living brain cells. It appeared that the artificial system either revived some brain cells that had died, or postponed their death.

However, the brain never regained its overarching electrical connections. In other words, the organ was never fully revived. “This is not a living brain,” Nenad Sestan, a neuroscientist at Yale who led the study, said in a press conference. “But it’s a cellularly active brain.” At the end of a six-hour period, the brains themselves had largely deteriorated, creating an automatic end to the experiment.

There was no evidence that the brains here regained any kind of consciousness; in fact, the solution used to provide oxygen to cells contained a drug that inhibits neurons from fully functioning like they are alive. This is crucial, Stephen Latham, a bioethicist at Yale, explained in the press conference, because bringing consciousness back to an organ like a brain is still an ethically grey area. Before that kind of research can be done, he said, international scientists and ethicists will have to decide whether or not the ends of such experimentation justifies the potential suffering of the animal (or in this case, pain that could possibly by felt by the brain itself). In this particular experiment, the scientists were ready to administer anesthesia to and lower the temperature of the brains immediately to alleviate any pain and suffering should it become clear the brains were completely reanimated.

“The main implication of this finding is that cell death in the brain occurs over a gradual time,” said Sestan. “Some of those processes can be postponed or even reversed.” This technology opens the doors for different modes of studying activity in the brain post-mortem, to try to understand what happens in the final days of diseases like Alzheimer’s or Parkinson’s. It could also lead to restoring the function to brain cells in people who have suffered a stroke or other trauma that deprived their cells of oxygen. But, the team says, the work is a long way from having any practical application in humans.