Study On The Mechanism Of Gut Microbiota Regulating Bone Marrow Mesenchymal Stem Cells

Objectives: Bone marrow mesenchymal stem cells(BMMSCs)are non-hematopoietic stem cells that display important role in maintaining bone homeostasis via multiple-differentiation and immunoregulation.However,increasing studies have indicated that these profound capacities are not innate but modified by gut microbiota,but the underlying mechanism remains elusive.The purpose of this study was to illustrate the mechanism by which gut microbiota influences BMMSCs function.Materials and Methods: The biological function of BMMSCs from conventionally raised(CONV)mice and germ free(GF)mice were evaluated including self-renewal,proliferation,multi-differetiation,and immunomodulation.Co-housing with CONV mice under SPF conditions was employed to investigate the influence of gut microbiota on the skeletal phenotype of GF mice and the function of unchallenged GF BMMSCs.Western Blot was used to screen the target protein of gut microbiota acting on BMMSCs.The si RNA and plasmid transfection were performed to detect the mechanism of target protein in regulating the biological function of BMMSCs.Results: Compared with CONV mice,osteogenic differentiation and immunomodulatory abilities of GF-derived BMMSCs were decreased,while there was no difference in their proliferative and adipogenic differentiation abilities.After gut microbiota colonization,the serum levels of IFN-γ and TNF-α in GF mice were increased,both of which promoted the expression of Fas in BMMSCs and maintained their osteogenic differentiation.In addition,gut microbiota colonization also upregulated the serum level of LPS in GF mice,which promoted Fas L expression and maintained the immunoregulatory ability of BMMSCs.Conclusions: The gut microbiota is an essential prerequisite for the osteogenic differentiation and immunoregulation of BMMSCs via regulation of the immune environment.These data reveal novel mechanisms by which gut microbiota influences BMMSCs function,which may provide an accessible approach in regulating BMMSCmediated bone homeostasis.