Bone Marrow Mesenchymal Stem Cells Regulate Microglial Polarization And Alleviate Deafferentation Pain In Rats By Secreting Glial Cell-derived Neurotrophic Factors

Objective:1.In vitro study on the role and mechanism of bone marrow mesenchymal stem cells(BMSCs)in regulating microglial differentiation.2.In vivo study on the role and mechanism of BMSCs in intramedullary transplantation for deafferentation pain(DP).Method:1.In vitro study,microglia was stimulated by lipopolysaccharide to simulate the occurrence and development of neuroinflammation,and then co-cultured with BMSCs,GDNF or siRNA GDNF-BMSCs.The expression of IL-1?,TNF-? and IL-10 were detected by RT-PCR and ELISA;RT-PCR and flow cytometry were used to detect the expression of microglial surface markers,and Western blot was used to detect the expression levels of pNF-Kb,pPI3K,and pAKT signaling pathway in microglia;2.In vivo study,an animal model of deafferentation pain was constructed.BMSCs or siRNA GDNF-BMSCs was transplanted intramedullarily on the 21st day after surgery.The behavioral changes were detected 7 days after transplantation.The main changes were to observe the changes in pain-related behaviors.Serum samples were examined by RT-PCR and ELISA to detect the expression levels of IL-1?,TNF-? and IL-10.Immunofluorescence staining was used to detect microglial differentiation;Western blot method was used to detect the expression levels of pNF-icb,pPI3K,and pAKT.3.All data are expressed as the mean ± SD.Statistical analysis was performed using SPSS 20.0 statistical software.Statistical significance was tested by a two-tailed Student's t-test.One-way analysis of variance was used for comparisons among groups and pairwise comparisons between sample means were performed using the Bonferroni method.Statistical significance was set at p<0.05.Result:1.After lipopolysaccharide stimulated,microglial expression levels of inflammatory factors IL-1?,TNF-?,and M1 microglial surface marker CD86 and pNF-?B signaling pathway were significantly increased,while there was no significant change in the anti-inflammatory factors IL-10 and M2 microglial surface marker CD206 and pPI3K/pAKT signaling pathway.When co-cultured with BMSCs or GDNF,the expression of IL-1?,TNF-a,CD86 and pNF-?B signaling pathway decreased significantly,while the expression level of IL-10,CD206 and pPI3K/pAKT signaling pathway increased significantly.The regulatory effect of BMSCs was more significant than that of GDNF and was partially attenuated by GDNF siRNA and PI3K inhibitor LY294002.2.After surgery,the exercise capacity of the rats was not impaired,and the affected limb was fully functional but mechanical stimulation could not cause pain symptom.Thus the DP model was successfully constructed.Pain-related behaviors changed significantly on the 21st day after surgery,showing the protection and autophagy of the affected limb.After intramedullary transplantation of BMSC,the pain symptom of DP rats were alleviated.The relieving effect can be partially attenuated by GDNF siRNA.After the surgery,the expression levels of serum inflammatory factors IL-1?,TNF-? and the M1 microglial surface marker CD 16/32 and pNF-?B signaling pathway in the spinal cord tissue of rats were significantly increased,while anti-inflammatory factor IL-10 and M2 microglial surface marker CD206 and pPI3K/pAKT signaling pathway did not show significant changes.After intramedullary transplantation of BMSCs,rats serum IL-1?,TNF-?,and CD 16/3 2 and pNF-?B signaling pathway in the injured spinal cord decreased significantly,while the expression level of IL-10,CD206 and pPI3K/pAKT signaling pathway increased significantly.This regulatory effect can be partially attenuated by GDNF siRNA.Conclusion:1.BMSCs downregulate the NF-?B signaling pathway and upregulate the PI3K/AKT signaling pathway by secreting GDNF to regulate microglial differentiation and thus inhibit the development of neuroinflammation;2.BMSCs downregulate the NF-?B signaling pathway and upregulate the PI3K/AKT signaling pathway by secreting GDNF to regulate microglial differentiation and thereby alleviate the symptoms of DP in rats..