In vitro myelination of regenerating adult rat retinal ganglion cell axons by Schwann cells.

Schwann cell cultures provide a highly favorable substrate for retinal ganglion cell (RGC) survival and axon growth in vitro (Bähr and Bunge, Exp Neurol 106:27, 1989; Hopkins and Bunge, Glia 4:46, 1991). In this report we have extended former studies to obtain axon regeneration, long-term survival, and myelination of adult rat RGC axons in co-cultures of retinal explants with purified Schwann cells. By using modified co-culture conditions, we observed myelination of regenerating adult RGC axons by Schwann cells after 3-4 weeks in vitro. Myelination was associated with a one-to-one Schwann cell-axon relationship, characteristic of the formation of peripheral myelin. Under culture conditions that supported myelination, long-term survival (more than 12 weeks) of a small population of RGCs was observed. These findings highlight the remarkable ability of Schwann cells to support long-term survival of adult rat RGCs in the absence of either central nervous system (CNS) target tissue or other peripheral nervous system (PNS) components. This tissue culture system may serve as a model for the systematic study of the molecular mechanisms which are involved in axon regeneration and myelination of adult CNS neurons.