[Optic nerve regeneration in adult mammals]

Axons of central neurons can regenerate in a peripheral nervous system milieu, by macrophage activation or by inhibition of Rho pathways. Among retinal ganglion cells (RGCs) with axons regenerating into a transplanted peripheral nerve segment, Alpha/Y cells have the highest ability to regenerate axons and their axons extend fastest. OFF-center RGCs regenerate axons less effectively and are more vulnerable to axotomy than ON-center ones. RGC axons extended beyond the crushed site when oxidized galectine-1, a macrophage activator, was vitreously injected. Rho inhibitors were added to cultured retinae to learn their effect on axonal regeneration. Neurite extension from the retinae was promoted with 10-300 microM Y-27632 or 1-20 microM Y-39983 whereas glial processes extended in 100-300 microM Y-27632, 1-20 microM Y-39983 or 10-100 microM Fasudil. The injection of 100 microM Y-27632 or 10 microM Y-39983 into the vitreous and crush site resulted in robust regeneration of RGC axons while 10 microM Y-276932 caused fewer regenerated fibers and Fasudil caused no fibers. Thus neurite extension may be crucial for axonal regeneration and glial process extension may be beneficial for the regeneration.