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

Purpose: Retinal ganglion cells (RGCs) of adult mammals can regenerate thei r axons along a segment of the peripheral nerve (PN) that is transplanted t o the cut optic nerve. There have been many trials of PN transplantation to induce axonal regeneration of RGCs in adult rodents, cats and ferrets. How ever, because of the technical difficulty in transplant operation, PN trans plantation in adult mice has not been carried out in spite of the availabil ity of many kinds of gene-manipulated animals. Here we report the procedure s for successful PN transplantation in this species. Methods: We made intraretinal (IR) and retrobulbar (RB) approaches for PN t ransplantation. Four weeks after PN transplantation, RGCs with regenerated axone 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 RE transp lantation (n = 11). As previously shown in other species, the regenerated R GCs were predominantly larger-bodied cells in comparison to intact cells. Conclusion: Possible reasons for the difference in regeneration ratio betwe en the two transplant approaches and the feature of soma size of regenerate d RGCs are discussed.