Death redefined: how pig brain function was restored after slaughter

Someone’s brought a pig back to life?

Not exactly. Neuroscientists at Yale University, led by Prof Nenad Sestan, temporarily restored some cellular function in pigs’ brains approximately four hours after the pigs had been slaughtered. It’s important to note, however, that the brains had been removed from the pigs’ heads.

So the pigs aren’t alive?

No. But for a while their brains weren’t dead either… well, not in the technical sense. Medically speaking, and in most countries legally, a sentient being is declared dead when their brain function has ceased. Without brain function, a person, or in this case a pig, is unable to breathe or pump blood around their body on their own, and without a supply of blood and oxygen their brain cannot regain consciousness. But by artificially pumping a blood substitute around the disembodied pig brains, Sestan’s team managed to keep the cells in the revived organs alive for 36 hours.

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How did they do it?

According to their research paper published in the journal Nature, the Yale scientists hooked the dead pigs’ brains up to a system called BrainEx. BrainEx has been specially developed to circulate a solution containing oxygen and nutrients around the disembodied organs. Once the solution was circulating, the team monitored the brain cells and saw that they were absorbing oxygen from the solution and releasing carbon dioxide – processes that are both indicative of normal metabolic function. The revived brain cells also showed decreased rates of decomposition compared to those in control brains that weren’t connected to the BrainEx system.

Perhaps most astonishing of all, however, was that Sestan’s team not only saw signs of an immune response in the revived brain cells (as if they were attempting to repair the damage that had been caused by their deaths) but also that the neurons in the revived brains were still capable of signal transfer.

How did the pigs feel about all this?

They didn’t. Although the revived brains were able to transfer signals, the solution being pumped around them carried chemicals to prevent widespread coordinated synaptic activity from being restored. In other words, the Yale scientists took steps to ensure the pigs’ brains wouldn’t regain consciousness, in order to prevent them from experiencing pain. But even if the brains did regain some measure of consciousness, Sestan’s team were on hand with anaesthetics, just in case.

What does all this mean?

It’s difficult to say with any degree of certainty. Although the technique shows that cell function can be restored in brains post mortem, currently it only works on brains that have been removed from their owners’ skulls. It does, however, provide a new avenue for studying brain function and may lead to new treatments for reducing brain injury as a result of depleted or disrupted blood flow, the kind caused by heart attacks or strokes.

Furthermore, if the technique can be successfully applied to human brains (which the Yale team points out is a long way off), it’s feasible that it could be used to test drugs that could not be ethically administered to living subjects. There are wider implications to consider, though, the main one being what this means for the current medical and legal definitions of death.