Abstract
Purpose :
Following acute damage, zebrafish Müller glia (MG) reenter the cell cycle to produce multipotent neuronal progenitor cells (NPCs) that regenerate lost neurons. In the avian and mammalian retina, acute damage triggers NF-kB signaling to mediate the inflammatory response and NF-kB signaling suppresses NPC proliferation. The goal of this study was to determine the expression of NF-kB components in zebrafish retinal degeneration mutants and to determine how NF-kB signaling impacts regeneration in both acutely damaged and diseased zebrafish retinas. Finally, we explored the role of microglia in mediating NF-kB signaling.
Methods :
Expression of NF-kB signaling components was assessed by qPCR using RNA purified from zebrafish cep290 and bbs2 mutant retinas at 6 months post fertilization (mpf). Elevation of NF-kB signaling was assessed using a zebrafish line expressing a transgenic Tg(nfkb:GFP) reporter gene. NF-kB signaling was inhibited using a synthetic NF-kB activation inhibitor (NAI; 6-Amino-4-(4-chlorophenethylamino)quinazoline). Rod photoreceptors were ablated with metronidazole (MTZ) induction in a transgenic line expressing a rod-specific nitroreductase gene, Tg(zOPS:ntr-YFP). Photoreceptor damage, cell numbers, and cell proliferation was quantified in retinal cryosections using immunohistochemistry for cone markers and PCNA, respectively.
Results :
Components of the NF-kB signaling pathway were upregulated in the zebrafish cep290 and bbs2 degeneration mutants, although not to the same extent as following acute photoreceptor ablation using a nitroreductase ablation paradigm. NF-kB inhibition increased proliferation of Muller glia and Muller glia-derived progenitors following MTZ-mediated photoreceptor ablation. NF-kB inhibition also significantly increased Muller glia proliferation in zebrafish retinal degeneration mutants.
Conclusions :
The NF-kB signaling pathway is an important regulator of retinal regeneration in the zebrafish. NF-kB is activated following acute damage and in disease models of retinal degeneration in zebrafish. As in the chick and mouse, Inhibition of NF-kB signaling increases Muller glia proliferation in zebrafish, strongly suggesting that this is a highly conserved mechanism to repress regeneration in vertebrates.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.