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.

Neuro tissue engineering of glial nerve guides and the impact of different cell types.

The aim of neuro tissue engineering is to imitate biological features in order to enhance regeneration. Following lesions of peripheral nerves, Schwann cells (SCs) reorganize to form longitudinal bands of Büngner (boB) which function as guides for regrowing axons. In order to imitate boB in synthetic implants designed to bridge nerve lesions, we developed resorbable, semipermeable nerve guide conduits with microstructured internal polymer filaments. We utilized a novel microcell chip and identified three extracellular matrix components conducive for coating non-permissive polymer surfaces. In order to maximize SC alignment, seven different microtopographies were investigated via the silicon chip technology. Special longitudinal microgrooves directed SC orientation and growing axons of dorsal root ganglia (DRG), thus achieving stereotropism. When these results were applied to microgrooved polymer filaments inside nerve guide conduits, we observed highly oriented axon growth without meandering. Since scar-forming fibroblasts could potentially interfere with axonal regrowth, triple cultures with fibroblasts, SC and DRG were conducted. Fibroblasts positioned on the outer nanopore containing conduit wall, did not hamper neuronal and glial differentiation inside the tube. In summary, for more rapid regrowth, functional boB can be induced by guided microtissue engineering. By considering both the negative and positive effects of cell interactions, a more rational design of nerve implants becomes feasible.