Retinal damage might not be a permanent sentence to vision loss
In a Barcelona laboratory, scientists have found a way to awaken a regenerative capacity that human eyes were long thought to have surrendered in the course of evolution. By fusing retinal support cells with adult stem cells, researchers created hybrid cells that can become the very neurons vision depends upon — a process that doubles in efficiency when the retina itself signals distress. The discovery does not yet promise a cure, but it reframes retinal damage as a condition that biology may one day be persuaded to undo.
- Millions living with retinal disease face permanent vision loss because the human eye, unlike those of fish or salamanders, cannot regenerate its own neurons — but that assumption is now being challenged.
- A team in Barcelona fused retinal support cells with adult stem cells and watched the hybrids transform into functioning neurons inside a laboratory model of the human retina.
- The urgency sharpened when researchers discovered that chemical distress signals from injured retinal tissue doubled the rate of cell fusion, suggesting the eye may already be attempting to heal itself.
- The hybrid cells carry four sets of chromosomes instead of two, raising unresolved fears about genetic instability and cancer risk that must be answered before any human trial can begin.
- Scientists are now looking to the liver — which naturally harbors stable tetraploid cells — as a possible model for understanding whether the retina can safely manage the same chromosomal complexity.
In a Barcelona laboratory, researchers have coaxed human retinal cells into a regenerative state once thought exclusive to cold-blooded animals. By fusing Müller glia — the structural support cells of the retina — with adult stem cells derived from human fat and bone marrow, a team at the Centre for Genomic Regulation created hybrid cells capable of becoming neurons, the light-sensing cells on which vision depends.
Cell fusion is a rare but documented event in human biology, observed in the liver, brain, and gut. What the team demonstrated, published in eBioMedicine, is that it also occurs in the retina — and that it can be deliberately triggered. More striking still, when the researchers exposed the cells to chemical signals that an injured retina naturally releases, the fusion rate doubled, suggesting the retina may already be attempting self-repair through a mechanism evolution preserved in fish and salamanders but largely abandoned in mammals.
To test whether the hybrid cells could function in real tissue, the team injected them into a retinal organoid — a laboratory model that replicates the structure of a human retina. The cells integrated successfully and differentiated into ganglion cells, the neurons that relay visual information from the eye to the brain. The process worked.
The road to clinical use, however, remains long. The hybrid cells contain four complete sets of chromosomes rather than the normal two, a condition called tetraploidy that raises serious questions about genetic stability and cancer risk. Researchers speculate that the retina may harbor a regulatory mechanism similar to the liver's, which naturally manages stable tetraploid cells and uses them as a genetic reserve during tissue repair. Whether such a safeguard exists in the retina is still unknown.
For now, the work stands as a proof of concept — evidence that the human retina retains a latent regenerative potential, and that the boundary between permanent damage and possible recovery may be less fixed than science once assumed.
In a laboratory in Barcelona, researchers have discovered that human retinal cells can be coaxed into a state of regeneration that was thought to belong only to creatures with cold blood. By fusing Müller glia—support cells that maintain the retina's structure—with adult stem cells drawn from human fat and bone marrow, a team led by ICREA Research Professor Pia Cosma at the Centre for Genomic Regulation has created hybrid cells capable of becoming neurons, the light-sensing cells essential to vision.
Cell fusion itself is not new to biology. Two cells merging into one is a rare event in humans, but it has been documented in the liver, brain, and gastrointestinal tract. What is new is evidence that this process occurs in the retina and, more importantly, that it can be harnessed therapeutically. The findings, published in eBioMedicine, suggest a pathway toward treating retinal damage and the vision loss that follows.
The researchers worked in controlled conditions, fusing Müller glia with stem cells in a dish. The results were promising on their own, but something unexpected emerged: when the team exposed the cells to chemical signals that the retina naturally releases in response to injury, the fusion rate doubled. This observation was crucial. It suggested that the retina itself might be trying to heal, and that cell fusion is part of that mechanism—one that evolution has preserved in fish and salamanders but that mammals, including humans, appear to have lost.
To test whether these hybrid cells could actually function in tissue, the researchers injected them into a retinal organoid, a laboratory model that mimics the structure and behavior of a real human retina. The hybrid cells took hold. They integrated into the tissue and differentiated into cells resembling ganglion cells, the neurons that carry visual signals from the eye to the brain. The process worked.
"Our findings bring us one step closer to recovering this ability," Cosma said, referring to the regenerative capacity that mammals surrendered somewhere in evolutionary time. The implication is profound: if Müller glia in the human retina retain the latent potential to become neurons, then retinal damage—whether from age, disease, or injury—might not be a permanent sentence to vision loss.
But the path from laboratory success to clinical treatment is long and lined with obstacles. The hybrid cells created in this study contain four complete sets of chromosomes instead of the normal two. This tetraploidy raises an immediate concern: will these cells become unstable? Will they turn cancerous? The researchers do not yet know. They theorize that the retina may possess a regulatory mechanism similar to one found in the liver, which naturally contains tetraploid cells that remain stable and even serve as a genetic reservoir, activating when tissue is damaged. If such a mechanism exists in the retina, it could be the key to making this therapy safe.
The study involved collaboration across three institutions in Catalonia and received funding from multiple sources, including the European Union and the Spanish government. The work represents a convergence of expertise in genomics, bioengineering, and ophthalmology. What remains is the harder work: understanding the safety profile of these cells, optimizing the fusion process, and eventually moving toward human trials. For now, the discovery stands as a proof of concept—evidence that the human retina is not as locked into its limitations as once believed.
Citações Notáveis
Our findings bring us one step closer to recovering this ability— Pia Cosma, ICREA Research Professor, referring to the regenerative capacity mammals have lost
The process was more efficient in the presence of a chemical signal transmitted from the retina in response to damage, resulting in rates of hybridization increasing twofold— Sergi Bonilla, postdoctoral researcher and first author of the study
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that fish and salamanders can regenerate their retinas but humans can't?
Because for them, retinal damage is reversible. A salamander loses sight; its Müller glia turn into new neurons and vision returns. A human loses sight and it stays lost. We've essentially traded that regenerative capacity for something else in our evolution, and we don't fully understand why.
So these hybrid cells—they're not new cells being introduced. They're human cells being awakened?
Exactly. The Müller glia are already there in your retina, doing their job as support cells. The fusion with stem cells seems to flip a switch that lets them remember how to become neurons. It's not replacement; it's reactivation.
The chemical signal that doubled the fusion rate—is that something you could trigger artificially?
That's the question. If you could identify that signal and deliver it, you might be able to activate the retina's own repair machinery without needing to inject cells at all. But we're not there yet.
What about the cancer risk? Four sets of chromosomes instead of two sounds dangerous.
It does. But the liver has cells with four sets of chromosomes and they don't become cancerous. They're stable, even useful. The researchers think the retina might have a similar safeguard. If it does, this becomes viable. If it doesn't, you've created a therapy that heals vision but causes cancer, which solves nothing.
How long until this could be tested in people?
Years, probably. First they have to understand the chromosome stability question. Then animal studies. Then, if everything checks out, human trials. This is early-stage work. But the fact that it works at all in the lab—that's the breakthrough.