Historically, it was always thought that the moment of death of a human being occurred when circulatory, respiratory or brain activity was stopped.
Although many organs can be transplanted after death, using techniques to increase their lifespan, the tissues of the central nervous system are no longer “viable” for this type of procedure soon after blood circulation ceases. And that prevents them from being used for transplants.
The kidneys, for example, can remain useful outside the body for 24 to 36 hours. But the tissues of the central nervous system, the billions of neurons that transmit sensory information such as electrical signals, lose their transplant potential very quickly after death.
Until now, little was known about the mechanisms that cause neuronal death and what are the possibilities of reversing it and optimizing its viability for transplants.
Recently, a team of researchers from the John A. Moran Eye Center, at the University of Utah, in the United States, assured that they managed to “revive” the neuronal cells responsible for detecting light in the retinas of already dead donors.
In the study, published in the journal Nature, the scientists describe how they used these retinas to investigate how they can revive cells associated with vision, called “photoreceptor cells.” In addition to “reviving” the cells after the donor’s death, the scientists were able to re-establish communication between them.
“We were able to awaken photoreceptor cells in the human macula, which is the region of the retina responsible for our central vision and our ability to see details and colors,” explains scientist Fatima Abbas, lead author of the study and a researcher at the Moran Eye Center.
“In eyes taken up to five hours after the donor’s death, these cells responded to bright, colored light and even very faint flashes of light,” he added.
Ophthalmologist Santiago Abengoechea, a specialist in retina and treatments for macular degeneration at the Barraquer Ophthalmology Center in Spain, says the study “opens up a range of future therapeutic possibilities,” specifically for diseases of the macula, such as age-associated degeneration.
According to the study, the researchers used retinas — as a model of the central nervous system — collected from dead humans and mice. They found that they could “awaken” photoreceptor cells, which detect light and allow us to “see”, up to five hours after the death of an organ donor.
But the scientists found problems in the process. They found that photoreceptor cells were unable to communicate with other retinal cells and determined that the critical factor leading to this communication problem was a lack of oxygen.
To overcome this hurdle, the researchers were able to obtain donor eyes just 20 minutes after death and designed a special transport unit that delivers oxygen and nutrients to the donated eyes. Using this approach, they found they could make retinal cells communicate in the same way they do in living bodies.
“We were able to make retinal cells talk to each other, in the same way they do in the living eye to provide human vision,” explained Frans Vinberg, another of the study’s authors, in a press release.
“Previous research has restored very limited electrical activity in the eyes of organ donors, but this has never been achieved in the macula (the part of the retina responsible for our central vision) and never to the extent that we now show,” he added.
Experts say the study is a very important advance for two main reasons. It will now be possible to study human vision in ways that have not been previously investigated with laboratory animal tests. But more importantly, the research could lead to new therapies for eye diseases.
“Restoring the functional activity of the photoreceptors is an unprecedented discovery that could open the door to future treatments,” ophthalmologist Santiago Abengoechea, from the Barraquer Ophthalmology Center, told BBC News Mundo, the BBC’s Spanish service.
“Until now, one of the boundaries was marked by the no-return path of unresponsive photoreceptors.”
Abengoechea says this problem is the leading cause of vision loss in people over 60. He guarantees that the new research will open the door to a wide range of potential treatments.
“The fact of being able to observe this ‘return to activity’ in a fundamental part of the retina such as the macula is essential to be able to restore vision in pathologies such as dystrophies or macular degeneration”, explains the specialist.
