4. Fish eyes could help regenerate human retinas
Fish retinas can repair themselves in a few weeks after being damaged. Researchers at Vanderbilt University have identified a signal that starts the self-repair process. They hope this discovery will lead to treatments to repair damage from degenerative retinal diseases and injury in humans.
“The prevailing belief has been that the regeneration process in fish retinas is triggered by secreted growth factors, but our results indicate that the neurotransmitter GABA might initiate the process instead,” said James Patton, Vanderbilt biological sciences professor and director of the study, in a news release. “All the regeneration models assume that a retina must be seriously damaged before regeneration takes place, but our studies indicate that GABA can induce this process even in undamaged retinas.”
The study suggests that fish and human retinas are structured similarly. A retina has 3 layers of nerve cells: light detecting photoreceptors, horizontal cells that integrate signals from photoreceptors, and ganglion cells that receive the visual information and send it to the brain.
Retinas also have adult stem cells called Müller glia that are in all 3 layers and give mechanical support and electrical insulation. In fish retinas, the Müller glia dedifferentiate, proliferate, then differentiate to start replacing damaged nerve cells. While present in mammalian retinas, Müller glia don’t regenerate like they do in fish.
Researchers discovered that high concentrations of GABA in the retinas kept the Müller glia dormant. The Müller glia began dedifferentiating and proliferating when the GABA concentration dropped, the first stage in the regeneration process. When injecting blinded zebrafish with high levels of GABA concentration, the regeneration process was suppressed.