Brain death may be less irreversible than previously thought

Brain death may be less irreversible than previously thought

Researchers have managed to “resurrect” retinal cells, which could redefine ophthalmology but also general neurology.

In works cited by ScienceAlert, American researchers come from “resurrect” partially human retinal cells by restoring their ability to communicate with each other. A very important step in a long series of works that could weigh heavily on ophthalmology… but also on clinical neurology in general.

Among all the elements with which animals have been endowed during natural selection, the retina is one of the most resounding successes. It is a structure based on a complex tangle of carefully organized nerve cells that converts a light signal into an electrical signal for the brain.

But like all other cells of the central nervous system, those of the retina tend to degenerate and then die during aging. In practice, this results in a decrease in visual acuity. For decades, researchers have therefore been trying to understand how these cells die in the hope of reversing the process.

These are traditionally very complicated works to carry out for several reasons. Because as in any complex system of this type, it is not simply a question of having each part repaired individually; we must also and above all allow them to work together.

Previous studies had already managed to restore some semblance of life to the photoreceptors – the elements responsible for capturing light – in the retina in the past. But these cells had also lost their ability to communicate with the rest of the retina. They were therefore not able to participate properly in the vision. At the time, the researchers had deduced that it was a concern for the supply of oxygen.

Eyes back from the dead

And recently, researchers from the University of Utah in the United States believed that they could overcome this obstacle. To achieve this, they partnered with a local hospital which provided them with eyes from organ donors at very short notice.

Less than twenty minutes after the patient’s death, they were sent to the researchers in a container specially designed for the occasion. They then designed a device capable of electrically stimulating the retina. And the machine worked admirably well.

Like the heart in an electrocardiogram (ECG) or the brain in an electroencephalogram (ECG), the retina can be subjected to an examination called an electroretinogram (ERG). On these ERGs, ophthalmologists are particularly interested in certain patterns: the a-, b-, c- and d-waves. Without going into detail, it is a graphic representation of certain elements of communication between the cells of the retina. Their analysis can help doctors determine whether the eye is healthy or not; these patterns can therefore only be found in retinas that are very much alive and in good health.

Or at least, that was the case until the work of these researchers. They have in fact succeeded in restore the “b-waves of their revived retinas. “These cells were able to respond to bright flashes, colored lights, and even very low intensity flashes“, explains Fatima Abbas, one of the authors of the study. A spectacular result, and even a world first.

We managed to make the cells of the retina talk to each other, the same way they do in a living eye to manage human vision”, exults Frans Vinberg, the great architect of this stimulation system. “Previous studies had restored very limited electrical activity in donor organs, but no one had achieved this level in the macula. [une couche de la rétine bardée de photorécepteurs, ndlr].”

A great lead in clinical ophthalmology…

In the wake of this great success, researchers sought to validate the procedure. The objective: to ensure that this was not an exception. They therefore confirmed the process on about forty new eyes. This allowed them to lay a solid working foundation; they could lead to new techniques to slow down or even reverse the degeneration of vision.

And that’s great news, because vision work is traditionally complicated to do. In this discipline, researchers depend almost exclusively on animal models; they mainly work with primates and rodents. An approach that has allowed some progress; but it also has obvious limitations since the results are not necessarily applicable to humans.

This work on the retina could lead to progress in general neurology. © Robina Weermeijer – Unsplash

With a technique that makes it possible to “wake up” a dead retina, each eye provided by a deceased organ donor could become a formidable research platform. Researchers will be able to experiment in real conditions to prevent a living retina from experiencing the same fate. “The scientific community can now study human vision in a way that was simply not possible with laboratory animals.”, explains Vinbverg.

From now on, we will be able to use this approach to develop treatments to improve vision and light signaling in degenerating retinas, particularly in the context of aging.” welcomes Anne Hanneken, a biologist associated with the study.

…and maybe also in general neurology?

But what is most interesting is certainly the very long-term scope of this work. Indeed, the retina is not the only element of the nervous system that could benefit from it. It is only the tip of a huge neurological iceberg. Eventually, the researchers hope that their approach may open the door to much broader studies of the central nervous system.

They believe that this work raises a lot of questions about the reversibility of neuron death. And that could have very real clinical implications. For example, we can imagine a process that would restore neurons damaged by trauma, pathology, or by aging.

© Geralt – Pixabay

So many elements that will certainly be very interesting for practitioners. But they would also serve many fundamental research laboratories. We think in particular of those who are working to drastically extend human life expectancy, as Jeff Bezos intends to do (see our article). If we push the reasoning to the extreme, we can even imagine rescue humanity from the clutches of neurological death.

These are obviously tracks that still remain very abstract at present. It is certainly not tomorrow that we will be able to content ourselves with pushing a button to pull a large accident victim out of a deep coma. But it is work of this type that will make it possible to approach it step by step. And if some teams manage to advance clinical ophthalmology in the meantime, there is no reason not to!

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