Macrophages Modulate Optic Nerve Crush Injury Scar Formation and Retinal Ganglion Cell Function.

Purpose: Optic nerve (ON) injuries can result in vision loss via structural damage and cellular injury responses. Understanding the immune response, particularly the role of macrophages, in the cellular response to ON injury is crucial for developing therapeutic approaches which affect ON injury repair. The present study investigates the role of macrophages in ON injury response, fibrotic scar formation, and retinal ganglion cell (RGC) function. Methods: The study utilizes macrophage Fas-induced apoptosis (MaFIA) mice to selectively deplete hematogenous macrophages and explores the impact macrophages have on ON injury responses. Histological and immunofluorescence analyses were used to evaluate macrophage expression levels and fibrotic scar formation. Pattern electroretinogram (PERG) recordings were used to assess RGC function as result of ON injury. Results: Successful macrophage depletion was induced in MaFIA mice, which led to reduced fibrotic scar formation in the ON post-injury. Despite an increase in activated macrophages in the retina, RGC function was preserved, as demonstrated by normal PERG waveforms for up to 2 months post-injury. The study suggests a neuroprotective role for macrophage depletion in ON damage repair and highlights the complex immune response to ON injury. Conclusions: To our knowledge, this study is the first to use MaFIA mice to demonstrate that targeted depletion of hematogenous macrophages leads to a significant reduction in scar size and the preservation of RGC functionality after ON injury. These findings highlight the key role of hematogenous macrophages in the response to ON injury and opens new avenues for therapeutic interventions in ON injuries. Future research should focus on investigating the distinct roles of macrophage subtypes in ON injury and potential macrophage-associated molecular targets to improve ON regeneration and repair.