From injury to recovery: Spatiotemporal dynamics of the visual pathway during spontaneous structural and functional regeneration after optic nerve transection in zebrafish

In adult mammals, optic nerve injury leads to irreversible vision loss due to its extremely limited regenerative capacity. In contrast, adult zebrafish possess a robust capacity for spontaneous visual system regeneration, although the spatiotemporal coordination of recovery across the retina, optic nerve, and brain remains poorly understood. In the present study, the regenerative dynamics following optic nerve transection were systematically characterized in adult zebrafish over a 5 week period using hematoxylin-eosin staining, immunohistochemistry, transmission electron microscopy, single-cell RNA sequencing, and optokinetic response (OKR) behavioral assessments. At 1 week post-injury (1 wpi), retinal ganglion cell depletion was evident but showed significant recovery by 2 wpi. Concurrently, the injured optic nerve displayed a marked increase in diameter and cell number at 2 wpi, including widespread expression of proliferating cell nuclear antigen, consistent with heightened proliferative activity. Single-cell transcriptomic profiling at 2 wpi revealed five principal cell populations: fibroblasts, mural cells, immune cells, mature oligodendrocytes, and myelin-forming oligodendrocytes. By 4-5 wpi, remyelination within the optic nerve and re-establishment of synaptic architecture in the optic tectum were strongly correlated with functional restoration of OKR behavior. These findings provide a comprehensive spatiotemporal framework of visual pathway regeneration in zebrafish, establishing a valuable model for elucidating conserved mechanisms of neural repair with translational potential for human vision restoration.