The Effect Of TNF-α On Schwann Cell Dedifferentiation And Stem Cell Markers Expression

The peripheral nervous system has remarkable regenerative capabilities in that injury nerves are able to re-establish their function. The distinct regenerative ability hinges on the regenerative properties of its glia, the Schwann cells, which can be dedifferentiated after injury. A series of inflammatory responses has been activated during nerve regeneration, among which TNF-α is a core inflammatory mediators,although its effect on nerve regenerative is not well understood. Besides, adult stem cell dedifferentiation and reprogramming are two different process both related to the activation of some stem cell markers. After Yamanaka’s group found that fibroblasts can be reprogrammed to pluripotency with the four transcription factors Oct4, Klf4,Sox2 and c-Myc(OKSM), many studies have done effort to explore the factors that impact the expression of OKSM. However, the low efficiency of i PS cells is still a problem nowadays, and there is no ideal model to study the endogenous OKSM expression.Objective: 1.To determine the effect of TNF-α on nerve regeneration and Schwann cell dedifferentiation. 2.To determine the expression of OKSM in cultured sciatic nerve and the role of TNF-α on OKSM. 3. To determine the effects of TNF-αdownstream pathways on Schwann cell dedifferentiation. 4. To determine the effects of TNF-α downstream pathways on the expression of OKSM.Method: 1.Evaluation the role of TNF-α on nerve regeneration and expression of immature Schwann cell marker P75 in nerve regeneration chamber. 2.Evaluation the role of TNF-α on Schwann cell dedifferentiation in cultured sciatic nerve by TUNEL,Immunofluorescence staining and RT-PCR. 3.Evaluation the expression of OKSM in cultured sciatic nerve by RT-PCR. 4.Evaluation the activation of NF-κB, JNK, P38 and ERK in cultured sciatic nerve by Western blot analysis. 5.Evaluation the roles of NF-κB, JNK, P38, ERK on Schwann cell dedifferentiation and OKSM expression in cultured sciatic nerve by RT-PCR.Result: 1.TNF-α inhibit Schwann cell dedifferentiation and nerve regeneration in-vivo. 2.TNF-α activate NF-κB, JNK, P38 and ERK in cultured sciatic nerve.3.TNF-α inhibit Schwann cell dedifferentiation though NF-κB pathway with a dose-dependent manner in cultured sciatic nerve. 4.The transcription of OKSM are up-regulated and inhibited by TNF-α and its downstream pathways in cultured sciatic nerve.Conclusion: In this study, we found that TNF-α had a negative effect on nerve regeneration, at least partly due to the inhibition on Schwann cell dedifferentiation.Besides, the transcription of OKSM were up-regulated in cultured sciatic nerves,inspired us to use it for the research of i PS cell generation. We also demonstrated that TNF-α and its downstream pathways such as NF-κB, JNK, P38 and ERK inhibited the transcription of OKSM.