Different spatial and temporal protein expressions of repulsive guidance molecule a and neogenin in the rat optic nerve after optic nerve crush with and without lens injury

The failure of lesioned mammalian CNS neurons to regenerate their axons remains a challenge. Evidence is emerging that repulsive proteins contribute to this failure. The repulsive guidance molecule A (RGMA) induces growth cone collapse in vitro, accumulates in the scar after spinal cord injury, and is up-regulated in glaucoma. In this study, we evaluated the spatial and temporal localization pattern of RGMA and its receptor neogenin in the optic nerve after optic nerve crush (ONC) without or with lens injury (LI) at up to nine time points (6 hr to 20 days) postsurgery by performing immunohistochemistry and Western blots. We found RGMA at the crush site (CS) and in the developing scar of ONC rats at every time point investigated, whereas it was absent in the CS of ONC + LI rats. Independent of the model, many cells were RGMA(+) in the ON: nerve fibers, blood vessels, astrocytes, oligodendrocytes, some microglia, some macrophages, and the sheath of the ON. Western blots showed a significantly lowered amount of RGMA in ONC + LI animals at 2, 4, and 6 days after crush compared with ONC animals. Furthermore, LI in sham-operated animals showed an increase of RGMA in six of eight time points compared with the sham-operated animals. Moreover, the effects of LI on the morphology of the ON were characterized at a level of detail never reported before. Our results show that RGMA is present and might contribute to the inhibitory environment in the ON, especially in and around the CS after ONC.