Thanks to stem cells grown in the laboratory, researchers hope to cure lots of vision problems linked to retinal damage.
It is sometimes said that humans watch over certain things. as in the apple of his eye “. The expression was not chosen at random; the eye is a marvel of natural engineering, but it is also exceedingly fragile. When important tissues are damaged, it results in vision loss that is often irreversible. But while waiting for a possible revolution brought about by brain-machine interfaces, the progress of certain researchers could still help people who are partially sighted or completely blind in the relatively near future.
In any case, this is what researchers from the University of Wisconsin-Madison, in the United States, suggest. They work on the retina, the most important tissue in the eye. It is lined with a host of small structures called photoreceptors. They are the ones that make it possible to translate a light signal into an electrical signal which can then be processed by the brain.
Retinal damage is one of those concerns traditionally considered irreversible. For years, researchers have therefore been trying to cultivate individual photoreceptors. The goal is to graft them to a damaged retina to restore its capabilities.
Artificial retinas grown in the laboratory
This work kicked into high gear in 2014, when Professor David Gamm’s team succeeded for the first time in generating drafts of artificial retinas. More specifically, it wasorganoids, that is, clusters of cells that function much like the model organ. There are loads of different organoids that are used in research, like this mini artificial brain that can play Pong.
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To produce them, the team simply collected so-called pluripotent stem cells. These are somewhat special objects that are above all precursors; during development, these cells respond to different biological signals by transforming themselves (we speak of differentiation). They can thus form the specialized cells that make up other tissues, such as the retina.
Gamm and his team showed that these lab-grown retinas were able to respond to different light signals by producing an electrical signal, just like the human eye. From there, in theory, all that remains is to transplant these synthetic cells with the aim of replacing the damaged tissue. ” We wanted to use the cells from these organoids as spare parts to replace those that have been lost to retinal disease. says Gamm.
The challenge of cellular communication
But his team still had to overcome one last obstacle, and not the least. Because to function properly, all these beautiful people must belong to the same functional unit, as is the case in a healthy retina. In other words, if cells can’t talk to each other, they can’t work together.
The researchers therefore had to find a way to force these nerve cells to mend themselves. More precisely, it was necessary to show that their synapses (the interface between a nerve cell and the object with which it wishes to communicate) were functional.
To achieve this, they infected certain cells in the organoids with a genetically modified variant of the rabies virus, which travels through nerve connections. They embedded a fluorescent marker in it to track his whereabouts. The cells were then separated to give them the opportunity to reconnect.
By the end of the experiment, many cells had formed synapses. And above all, a large number of them presented these famous fluorescent markers.
This indicates that the rabies virus has successfully crossed the synapse. By extension, this means that the junction is functional, and that the cells are able to communicate. In theory, they could therefore be used to treat a damaged retina.
In a statement from his university, Gamm says the work represents the ” last piece » of this great puzzle; they succeeded in definitively proving that the synapses of the organoids were indeed functional.
Towards a potentially historic clinical trial
They now hope to be able to launch a clinical trial in the relatively near future. The idea would be to take a few healthy retina cells from a patient, put them in culture, and then transplant them with great precision. They could thus reconnect with each other to participate in the functioning of the retina.
It should be noted that until proven otherwise, this outcome is still theoretical. Moreover, even if the clinical trial brings conclusive results, this technique will not cure all sight problems. For example, it would not be suitable for glaucoma, which results from a problem with the optic nerve.
But if necessary, it would still be a real revolution for medicine applied to vision. Photoreceptor-related problems remain extremely common, according to the study authors. Such therapy could therefore represent real added value for public health.
It will therefore be necessary to follow this work with particular attention. Because with brain-machine interfaces (see our article below), this approach based on cell culture is one of the most promising ways to put an end once and for all to these extremely heavy afflictions to bear on a daily basis.
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