Scientists bring nerve cells from human eyes back from the dead

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In what is being heralded by experts as a groundbreaking study that could transform vision research, scientists from the University of Utah and Scripps Research have succeeded in reviving light-sensitive neuron cells in the eyes from a donor who died a few hours earlier. Nerve cells could communicate with each other again in the retina after the procedure, essentially reviving them.

“We were able to awaken 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 color,” Fatima Abbas of the John A. Moran Eye Center explains to the University. of Utah, lead author of the new study. “In eyes obtained up to five hours after the death of an organ donor, these cells responded to bright light, colored lights, and even very faint flashes of light.”

Some human organs remain functional and viable for transplantation for several hours after a patient dies. But that’s not something we can say about nervous system tissues, which are among the first to shut down completely due to oxygen deprivation.

Abbas and his colleagues embarked on this study to better understand why nerve cells are destroyed by lack of oxygen, and they chose the retina as a model of the central nervous system.

Scripps Research Associate Professor Anne Hanneken successfully procured the eyes of an organ donor within 20 minutes of death to minimize oxygen deprivation damage to nerve cells. The eyes were placed in a special transport unit which supplied artificial blood, oxygen and nutrients via a network of heaters and pumps.

Using a special device designed for this study, the researchers stimulated the retina of the donor’s eyes and measured the electrical activity of the cells inside. When we see things due to light hitting the retina, specific electrical signals called “b waves” are generated. But this signal is completely absent shortly after a person dies, even if you shine a flashlight directly into the eyes.

With this approach, however, the researchers were able to stimulate the retina and measure “b waves” for the first time in postmortem human eyes.

“We were able to get the retinal cells to talk to each other, as they do in the living eye to mediate human vision,” Frans Vinberg, a scientist at the Moran Eye Center, said in a statement. “Previous studies have restored very limited electrical activity in the eyes of organ donors, but this has never been achieved in the macula, and never to the extent that we have now demonstrated.”

This method is proof of concept for reviving neurons in the central nervous system as a whole, so it could be adapted to restore electrical communication in neural tissue in the spinal cord or perhaps even the brain. For now, a better understanding of how oxygen deprivation strangles the signals produced by the retina could help scientists treat specific neurodegenerative diseases that affect sight, including age-related macular degeneration.

But the findings also raise big questions about the nature of death itself. Formally, a person is declared dead when neural activity is lost. But if methods like these can be used to revive and restore communication between cells, could we bring some people back from the dead? Provided their neural activity is only lost for a few minutes, this could indeed be a plausible possibility in the future. Brain death, as currently defined, may not be truly irreversible, shocking as that may seem.

Already, there is progress. In 2019, a team from Yale University shocked everyone by successfully restoring circulation and cellular activity to a pig’s brain four hours after the animal died untimely. Scientists have discovered that many basic cellular functions, once thought to cease seconds or minutes after oxygen and blood flow stop, can be restored. However, they were unable to restore overall neural activity as well.

Resurrecting dead humans is, admittedly, a pretty lofty goal, which is why University of Utah researchers are content to make smaller gains, like revolutionizing human vision research.

“The scientific community can now study human vision in a way that is simply not possible with laboratory animals,” says Vinberg. “We hope this will motivate organ donor societies, organ donors and eye banks by helping them understand the exciting new possibilities that this type of research offers.”

The results are published in the journal Nature.

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