Survival of axotomized retinal ganglion cells in peripheral nerve-grafted ferrets

PURPOSE. Peripheral nerve (PN) grafting to the optic nerve stump stimulates not only axonal regeneration of the axotomized retinal ganglion cells (RGC s) into the grafted PN but also their survival. The purpose of the present study mas to determine the number, distribution and soma diameter of only s urviving RGCs without regenerated axons and surviving RGCs with regenerated axons in PN-grafted mammals. METHODS. A segment of PN was grafted to the optic nerve stump of adult ferr ets. Two months after the PN grafting, surviving RGCs with regenerated axon s were retrogradely labeled with granular blue (GB) and stained with RGC-sp ecific antibody C38. Surviving RGCs without regenerated axons were identifi ed as C38-positive cells without GB labeling. RESULTS. Twenty-one percent of RGCs survived axotomy after PN grafting in t he area centralis (AC), whereas 47% survived in the peripheral retina. Twen ty-six percent of surviving RGCs in the AC exhibited axonal regeneration, w hich was higher than that in the peripheral retina, Soma diameter histogram s revealed that RGCs with regenerated axons showing both GB and C38 positiv ity were in the large soma diameter ranges. In contrast, the soma diameter distribution of surviving RGCs that did not have regenerated axons showed a peak in the smaller soma diameter ranges. CONCLUSIONS. The present data suggest that PN grafting promotes survival of axotomized RGCs more effectively in the peripheral retina than in the AC. Among surviving RGCs, the larger cells exhibited axonal regeneration into t he grafted PN, whereas the axons of smaller cells did not to regenerate in either the AC or the peripheral retina.