Nerve fibroblast impact on Schwann cell behavior.

In order to reveal non-neuronal cell interactions after peripheral nerve lesions, we began to analyze the impact of sciatic nerve fibroblasts on Schwann cells in vitro. Both cell types are considered to have opposite effects on axonal regeneration. Few data are available on how repulsive nerve fibroblasts affect neuritotrophic Schwann cells and thus might indirectly influence axonal regrowth. Using different culture systems in conjunction with time-lapse video recording, metabolic labeling, pharmacological intervention, RNAi knockdown, Western blotting and RT-PCR analysis, we found that nerve fibroblasts differentially modify the various responses of Schwann cells. In the presence of collagen type IV and heparan sulfate proteoglycan but not of laminin, diffusible fibroblast factors slow down Schwann cell proliferation. In contrast, fibroblast factors increase the migratory activity of Schwann cells without being chemoattractive. One pro-migratory fibroblast factor turned out to be neuregulin. The pro-migratory activity of nerve fibroblasts and of recombinant neuregulin-1beta1 can be counteracted by neuregulin-specific pharmacological intervention and by neuregulin RNA interference. We show for the first time that nerve fibroblasts play antagonistic and agonistic roles for Schwann cells in a context-dependent manner. The data shed light on cellular mechanisms and have implications for some neuro-tissue engineering strategies.