Synergistic effect of optic and peripheral nerve grafts on sprouting of axon-like processes of axotomized retinal ganglion cells in adult hamsters

Abstract

We investigated the sprouting response of retinal ganglion cells (RGCs) following the transplantation of peripheral nerve (PN) and/or optic nerve (ON) into the vitreous of the eye and the intraorbital transection of the optic nerve in hamsters. Our previous results showed that an intravitreal PN graft could induce sprouting of axon-like processes in axotomized RGCS [3] (Cho, E.Y. and So, K.F., Characterization of the sprouting response of axon-like processes from retinal ganglion cells after axotomy in adult hamsters: a model using intravitreal implantation of a peripheral nerve, J. Neurocytol., 21 (1992) 589–603). In this model, we have examined the effect of intravitreal ON graft on the sprouting of RGCs both following a co-transplantation of PN and ON into the vitreous and transplantation of ON alone. The present results show that sprouting is increased by more than two-fold in retinas having PN and ON grafts than a PN graft alone. However, the ON graft by itself rarely induced sprouting in RGCs. These results suggest that the ON graft enhance the number of RGCs to sprout axon-like processes in the presence of PN graft by exerting a synergistic rather than an additive effect, since ON graft alone did not induce sprouting. In addition, no diffusible inhibitory effect of ON graft on PN induced sprouting was observed.