Abstract
Optic nerve (ON) injury causes blindness in adult mammals as their retinal ganglion cells (RGCs) cannot regenerate axons. However, amphibian RGC axons do not experience the same regenerative failure. Studying the regeneration process of the ON in amphibians holds profound implications for regenerative medicine and human health. Using transgenic tadpoles and laser micro-optics, we developed a reproducible ON transection and regeneration model. Through microscopy, functional testing, TUNEL, EdU assays, and RNA-seq, we characterized the ON injury response and recovery. Our model suggests no chemoattractant gradient exists early in regeneration, with defasciculated axons sprouting in random directions from the globe-proximal cut end. Once individual axons reach the appropriate anatomical insertion point in the brain, their tract is reinforced by other regenerating axons, restoring normal ON morphology. Thus, guidance cues or scaffolding from brain-innervating axons likely support later stages of regeneration. After 14 days, the regenerated ON is morphologically indistinguishable from the naïve ON, and visual function is restored. We found no evidence of RGC death or new RGC formation in the model, suggesting that only pre-existing RGCs are involved in ON regeneration.