Axonal regeneration of mouse retinal ganglion cells by peripheral nerve transplantation; a quantitative study

Purpose: Retinal ganglion cells (RGCs) of adult mammals can regenerate their axons along a segment of the peripheral nerve (PN) that is transplanted to the cut optic nerve. There have been many trials of PN transplantation to induce axonal regeneration of RGCs in adult rodents, cats and ferrets. However, because of the technical difficulty in transplant operation, PN transplantation in adult mice has not been carried out in spite of the availability of many kinds of gene-manipulated animals. Here we report the procedures for successful PN transplantation in this species. Methods: We made intraretinal (IR) and retrobulbar (RB) approaches for PN transplantation. Four weeks after PN transplantation, RGCs with regenerated axons were identified by retrograde labeling with rhodamine or horseradish peroxidase applied into the PN segment. Results: A quantitative survey showed that the mean regeneration ratio was 1.0 % (n = 8) in IR transplantation, whereas it was only 0.1 % in RB transplantation (n = 11). As previously shown in other species, the regenerated RGCs were predominantly larger-bodied cells in com-parison to intact cells. Conclusion: Possible reasons for the difference in regeneration ratio between the two transplant approaches and the feature of soma size of regenerated RGCs are discussed.