Scientists look to fish for retinal regeneration answers

Scientists have been researching retinal regeneration in zebrafish and, according to an article published in the journal St Cell Reports, the university group has discovered the signal that appears to trigger the self-repair process.“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,” research lead Professor James Patton of Vanderbilt’s Biological Sciences said.{{quote-A:R-W:450-I:2-Q: If we are correct, then it might be possible to stimulate human retinas to repair thselves by treating th with a GABA inhibitor, -WHO:James Patton, Research Lead Professor of Vanderbilt’s Biological Sciences}}“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 retinal regeneration process is not present in mammals, despite the structure of the retinas of fish and mammals being basically the same. GABA is believed to be supported by an adult st cell called Müller glia (MG), which spans all three layers of the retina and provides mechanical support and electrical insulation.During regeneration, MG regresses from a specialised state into a simpler one and begins to proliferate and differentiate into replacents for the damaged nerve cells. While MG is present in mammals, it does not regenerate.Researchers theorised that GABA – a rapid-response neurotransmitter – could be responsible for retinal regeneration after being inspired by the results of a study in the mouse hippocampus which found that GABA was controlling st cell activity.{{quote-A:L-W:450-Q: Scientists have been researching retinal regeneration in zebrafish and discovered the signal that appears to trigger the self-repair process. }}They then designed a series of experiments with zebrafish – an important animal model for studying regeneration – which determined that high concentrations of GABA in the retina kept MG dormant, and that they only began dedifferentiating and proliferating when GABA concentrations dropped.“Our theory is that a drop in GABA concentration is the trigger for regeneration. It initiates a cascade of events that includes the activation of the Müller glia and the production of various growth factors that stimulate cell growth and proliferation. If we are correct, then it might be possible to stimulate human retinas to repair thselves by treating th with a GABA inhibitor,” Patton said.The next step in the study is to determine if GABA is also responsible for producing new photoreceptors and specialised neurons in the retinas of zebrafish and mice.