CONTACTS BETWEEN REGENERATING AXONS AND THE SCHWANN-CELLS OF SCIATIC-NERVE SEGMENTS GRAFTED TO THE OPTIC-NERVE OF ADULT-RATS

The relation between Schwann cells, basal laminae and axons during ret inal ganglion cell regeneration was studied by using cellular, acellul ar and partially acellular sciatic nerve autografts into the optic ner ve. Acellular grafts were achieved by temporary compression which elim inates living Schwann cells and axons. The compressed sciatic nerve to gether with the intact portion was used as a partially acellular graft . The compressed portion was anastomosed to the optic nerve and the in tact portion was situated distally. After 3-21 days post-operation, th e grafts were studied by thin sectioning and freeze-fracture. Axons we re seen to regenerate into cellular grafts in cont ct with Schwann cel ls after one week, but not into acellular grafts for the entire period . In the partially acellular grafts, regenerating axons were first obs erved after two weeks and were always in contact with Schwann cells mi grating from the intact portion. Moreover, membrane specializations, f uzzy materials in the space between apposed membranes, and putative ti ght junctions, were found between regenerated axons including growth c one and Schwann cells, and between adjoining Schwann cells. An extensi ve meshwork Of putative tight junctions was displayed between reformin g perineurial cells surrounding the groups of Schwann cells and associ ated axons. Gap junctions were seen between adjoining Schwann cells, a nd between reforming perineurial cells. These results Suggest that the axonal contact with Schwann cell surfaces plays an important role in retinal ganglion cell regeneration.