Acute effects of continuous caffeine exposure on cell regeneration in the zebrafish retina

The use of the zebrafish model is crucial to understand central nervous system regeneration, including the retina. Unlike mammals, in which retinal injuries and disease cause blindness, zebrafish repair their retinas through the reprogramming of Müller glia (MG). Investigating the molecular and genetic mechanisms that trigger self-repair enables the design of pharmacological and gene therapies applicable to ophthalmology, aimed at halting vision loss. We aimed to evaluate the effects of caffeine (non-selective adenosine receptor antagonist) on MG reprogramming and proliferation in the zebrafish retina. Retinas were injured via intravitreal injection of CoCl2 (1.3 mM). Zebrafish were exposed to caffeine (5 mg/L) in the tank water for 96h. Immunofluorescence for PCNA, GFAP, and microglia (IB4-positive) were detected in retinal cryosections and whole-mounts. Quantitative RT-PCR was used to determine the expression of GFAP, TNFα, adenosine receptors (A2aa, A1b, A2b), and proneural pluripotency factors (Ascl1a and Lin28). Caffeine decreased Ascl1a expression and increased Lin28a expression in injured retinas. Microglial cells and the transcriptional expression of A2aaR were reduced in caffeine-treated injured retinas. Caffeine treatment reduced MG gliosis in injured retinas. Our findings indicated that caffeine exerts neuroprotective effects in the retinal injury paradigm in zebrafish by modulating the inflammatory response that triggers the induction of retinal progenitors.