NERVE GROWTH-FACTOR INDUCES PROCESS FORMATION IN MENINGEAL CELLS - IMPLICATIONS FOR SCAR FORMATION IN THE INJURED CNS

Nerve growth factor (NGF) induces the differentiation and supports the survival of subpopulations of neurons in the PNS and CNS. Here we rep ort that meningeal cells in the pia mater express immunoreactivity and mRNA for both known NGF receptors, the low-affinity receptor p75 and the tyrosine kinase receptor trkA. NGF induces rapid tyrosine phosphor ylation of trkA in meningeal cells in vitro. NGF does not stimulate pr oliferation of primary meningeal cells but induces process outgrowth. p75- and trkA-immunoreactive meningeal cells with long processes, rese mbling NGF-treated cells in vitro, are abundant in the scar tissue tha t forms at spinal cord lesions in rat and cat. These data suggest that NGF, which is expressed at increased levels in the brain and spinal c ord after lesions, may be involved in scar formation in the injured CN S.