Lee and B

Lee and B.R. pathways. Furthermore, exogenous supply of HGF around the injury site, by intramuscular injection of a plasmid DNA Nelfinavir expressing human HGF, enhanced the myelin thickness and axon diameter in injured nerves. Taken together, our results indicate that HGF and c-met play important functions in Schwann cell-mediated nerve repair, and also that HGF gene transfer may provide a useful tool for treating peripheral neuropathy. Introduction When the peripheral nerve gets wounded, SCs formed myelin structure are dedifferentiated and initiate the regeneration process1. Dedifferentiated SCs begin to produce not only cytokines and chemokines such as TNF-, LIF, and CCL2/MCP-1, but also secret various neurotrophic factors, for example, GDNF, NGF, and VEGF to promote axon elongation and activate other cells for nerve repair1C3. In addition, SCs directly interact with the peripheral nerves to guide regenerating axons to the distal nerve. Once axons regrow, SCs in close proximity to newly regenerated neurons bind to axons and start the re-myelination process. As a result, axons regrow and innervate to their target tissues, and new myelin structures are formed4,5. A variety of neurotrophic factors have been studied for their involvement in nerve regeneration. The most extensively studied genes include GDNF, NGF and VEGF for their functions and actions in the peripheral nerve regeneration process6C9. These growth factors are highly expressed in injured nerve and activate neuronal and non-neuronal cells for repair of the injured nerves10. For instance, VEGF directly increases FAZF the neuron survival rate and axon outgrowth. VEGF also promotes the vascularization of the injured nerve to reconstitute its microenvironment, leading to the facilitation of the nerve repair process11C13. Hepatocyte growth factor (HGF) is another angiogenic factor that has been reported to Nelfinavir work on the nervous system directly or indirectly14. HGF has been shown to promote angiogenesis, cell survival, cell migration and anti-inflammation in a variety of cell types15, and also produce neurotrophic effects in both CNS and PNS14. This multifunctional protein is secreted mainly by mesenchymal lineage cells, and receptor tyrosine kinase c-met is the only known cellular receptor15. In the case of PNS, HGF can enhance survival and axon outgrowth of cultured motor neurons16C19, and it is also known to interact with NGF to exert neurotrophic effects on sensory neurons20. Recently, it has been reported that Gab2 protein is required for the migration and proliferation of SCs and HGF could induce the activation of Gab2 to show such cellular effects21. However, whether c-met receptor has any role in peripheral nerve injury is largely unknown. In this study, we investigated the role(s) of HGF and c-met in peripheral nerve regeneration, using the mouse nerve crush model. It was found that HGF expression was highly induced at the nerve injury site, while the level Nelfinavir of phosphorylated c-met as well as total c-met activation was greatly increased mainly in SCs distal from the injury site. When the c-met inhibitor (PHA665752) was administrated to mice, the re-myelination process was suppressed. Treatment of rat primary SCs with recombinant human HGF protein enhanced both?migration and proliferation. HGF also increased the expression of neurotrophic factors and inflammatory cytokines such as GDNF, LIF, and TNF-. We also found that HGF could activate downstream signaling pathways such as ERK/RSK, AKT and S6K, but not mTOR, STAT3 or JNK pathways. When HGF was exogenously introduced around the injury site by intramuscular injection of plasmid DNA engineered to express HGF, myelin thickness of injured nerve was significantly improved, indicating that the nerve regeneration process was?facilitated. Taken together, our data suggested that HGF could induce the activation of Schwann cells to promote re-myelination of damaged nerves, and that exogenous addition of HGF could expedite the nerve regeneration process. Results HGF expression is increased in injured Nelfinavir peripheral nerves To investigate the role(s) of.