Two signals make eye support cells regrow neurons in mice
When retinal cells die in mammals, they are gone for good. That makes vision loss from retinal damage nearly irreversible. But researchers have now found how two combined signals can prompt support cells in the mouse retina to generate new neurons.
The retina contains light-sensitive nerve cells that send visual information to the brain. When these cells are lost to disease or aging, they do not grow back in humans. In fish like zebrafish, it is different: there, supporting glial cells called Müller glia can transform into new nerve cells after injury. In mammals, that capacity is almost entirely absent.
Researchers report in the journal eLife how they partially overcame this barrier in mice. The study shows that two simultaneous interventions are needed: blocking Notch signaling (a molecular pathway that keeps cells in a support state) and forcing cell division. Each intervention alone had little effect. Together, they caused Müller glia to divide and convert into cell types resembling bipolar and amacrine neurons, two types of retinal nerve cells.
Promising but far from complete
The newly formed cells survived long-term in the mouse retina, which is encouraging. However, they did not fully mature. The researchers describe them as cell types that resemble neurons but do not yet fully function. Whether they can actually detect light and transmit signals was not demonstrated in this study.
For longevity, this is relevant because age-related eye diseases, such as macular degeneration, involve the loss of retinal cells. If it ever becomes possible to regenerate those cells, that would open a new avenue alongside existing treatments. This remains speculative for now: the step from mouse to human is large, and restoring fully functional neurons is a very different challenge from cell division alone.
What this research adds
The combination of Notch inhibition and forced cell division is a new mechanistic insight. It was previously unclear why stimulating retinal cell regeneration in mammals is so difficult. This study points to Notch signaling as a brake that must be actively released before cell division and conversion can follow. That provides a more concrete starting point for further research.
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