Figure 4.

Neurites extended from DRG sensory neurons in vitro become myelinated in co-cultures with chronically denervated SCs. Myelination of the axons is not evident in the absence of SCs but it proceeds normally in SC-DRG sensory neuronal co-cultures, even after chronic SC denervation. (A,B) DRG neurons (*) maintained in culture for 24 days without SCs, were not myelinated as indicated by the arrows and seen by absence of Sudan Black staining in the unmyelinated axon bundles. Magnification was 20× (A) and 40× (B). (C–E) DRG axons were myelinated when DRG neurons were co-cultured with SCs whether or not the SCs were acutely denervated (C: 7 days) or chronically for 7 weeks (D,E) or 17 months by transecting and ligating the sciatic nerve in vivo in the right and left hindlimbs, respectively, prior to co-culture. Scale bar = 30 μm.