Scientists think brain death can be reversed

EYES harvested from organ donors have been “brought back to life” in a breakthrough scientists hope may indicate that brain death is reversible.

Researchers in the US proved that photo-sensitive neurons in the retina respond to light and communicate with each other for up to five hours after death, during which time they send signals “resembling those recorded from living subjects”.

Crucially, these neurons form part of the central nervous system (CNS) that encompasses the brain and spinal cord, indicating that other CNS cells may be similarly restored, perhaps bringing back consciousness.

Writing in the journal Nature, the authors said that their study “raises the question of whether brain death… is truly irreversible”.

Dr Fatima Abbas, of the Moran Eye Centre at the University of Utah, the study’s lead author, said: “We were able to wake up photoreceptor cells in the human macula, which is the part of the retina responsible for our central vision and our ability to see fine detail and colour. In eyes obtained up to five hours after… death, these cells responded to bright light, coloured lights, and even very dim flashes of light.”

In 2019, Yale University used a cocktail of chemicals to restart the brains of 32 pigs that had been slaughtered four hours earlier and succeeded in switching on blood circulation and metabolism. But experts said the new research had gone further to restore b-waves – the slow, rhythmic oscillations recorded in living brains.

Dr Frans Vinberg, assistant professor of ophthalmology and visual sciences at the University of Utah, said: “In Yale’s case, coordinated population activity of neurons in pig brains could not be revived. In our case we were able to revive population responses from photoreceptor cells even up to five hours after death in the human central retina, an important part of our central nervous system.

“We were able to make the retinal cells talk to each other, the way they do in the living eye. Past studies have restored very limited electrical activity in organ donor eyes, but this has never been achieved in the macula, and never to the extent we have now demonstrated… similar things might be seen also in the other parts of the brain.”

Researchers hope experimenting on human eyes instead of animal eyes will speed-up development of sight-loss therapies and improve the understanding of neurodegenerative diseases.