Abstract
Purpose :
Unlike mammals, zebrafish regenerate neurons in response to an acute retinal damage. This regeneration requires Müller glia (MG) to reprogram and divide asymmetrically to produce neuronal progenitor cells (NPCs). However, most forms of retinal degeneration in humans result from chronic neuronal loss. Therefore, it is important to understand how zebrafish MG respond to chronic damage if we are to ultimately stimulate neuronal regeneration in humans. We utilized three different chronic zebrafish photoreceptor degeneration mutant gosh (early onset cone degeneration), cep290 (late onset cone degeneration), and rho (rod degeneration) to evaluate the potential of MG and NPCs to proliferate and regenerate retinal neurons in different acute damage models.
Methods :
Adult wild-type (WT) and photoreceptor mutants (gosh, cep290, and rho) were subjected to two distinct acute injury models: constant light-induced loss of rod and cone photoreceptors and N-methyl-D-aspartate (NMDA)-mediated excitotoxicity of amacrine and ganglion cells. Retinal cryosections were immunostained with a PCNA antibody to assess MG and NPC proliferation. Retinas were also labeled with 5-ethynyl-2′-deoxyuridine (EdU) to determine the fate of the proliferating NPCs in the regenerated retinas.
Results :
Each mutant possessed different proliferative responses without acute damage, with rho mutants displaying PCNA-positive cells in the outer nuclear layer (ONL), gosh mutants possessing PCNA-positive cells in the inner nuclear layer (INL) and ONL, and cep290 mutants lacking any PCNA-positive cells. When challenged with acute light or NMDA damage, all three mutants exhibited an increased number of PCNA-positive cells, however fewer than control WT fish. Further, the different mutant retinas exhibited a shift in the neuronal cell types regenerated relative to control WT retinas following an acute damage.
Conclusions :
Our findings demonstrate that zebrafish photoreceptor degeneration mutants, which exhibit limited to no regeneration response, can be stimulated by an acute damage to induce MG and NPC proliferation and neuronal regeneration. Further elucidating mechanisms underlying the regeneration response in zebrafish can potentially lead to the development of regeneration mechanisms in humans.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.