Resistin Promotes Osteogenic Differentiation Of Bone Marrow Mesenchymal Stem Cells By Activating PI3K/AKT/mTOR Pathway

Background: The treatment of bone defects is a difficult problem in orthopedics.At present,the treatment mainly relies on autologous or allogeneic bone transplantation,which may lead to some complications such as foreign body rejection,local infection,pain,or numbness at the bone donor site.Local injection of conservative therapy to treat bone defects is one of the research hotspots at present.Bone marrow mesenchymal stem cells(BMSCs)can self-renew,significantly proliferate,and differentiate into various types of cells.Osteogenic differentiation(OD)of bone marrow mesenchymal stem cells(BMSCs)contributes significantly to the regeneration of bone defects.Resistin mainly comes from the secretion of human macrophages,which is one of the secretory proteins of resistin-like molecule(RELMs)family.Resistin,an adipose tissue-specific secretory factor,has been shown to involve many different functions,including metabolism,inflammation,cancer,and bone remodeling.This study explored the effects and mechanisms of resistin on the OD of Rat’s BMSCs.Materials and Methods: Rat BMSCs were obtained from Sprague Dawley rats.In vitro,The normal group and osteoinductive group were constructed,and the expression of Resistin was detected by real-time quantitative polymerase chain reaction and protein immunoblotting.In order to explore the effect of Resistin on osteogenesis differentiation,10 ng/ml Resistin was added to the osteogenic induction medium.The expression of osteogenic differentiation related genes(RUNX2,OCN and COL1A1)and PI3K/AKT/mTOR were detected by Western blot.The rat BMMSCs were transfected with si-Resistin and pc DNA3.1-resistin by RNA interference(RNAi).The effects of si-Resistin and pc DNA3.1-resistin on the osteogenic differentiation of rat BMMSCs were analyzed by RT-PCR and Western blot.Finally,uprosertib(AKT inhibitor)and pc DNA3.1-resistin were co-transfected into rat BMMSCs to detect the regulation of downstream target gene TAZ and analyze the mechanism of osteogenic differentiation of rat BMMSCs.In vivo,Rats were sacrificed 4 weeks after surgery and their femur specimens were collected.micro-CT imaging,hematoxylin,eosin staining,Masson staining,and immunofluorescent staining were performed to evaluate the role of resistin in healing rat femoral condyle defect.Results: Resistin was highly expressed in BMSCs with OD.Upregulation of resistin contributed to the progression of OD of BMSCs by activating PI3K/AKT/mTOR signaling pathway.In addition,resistin facilitated OD by targeting transcriptional co-activator with PDZ-binding motif(TAZ).In a rat femoral condyle bone defect model,local injection of resistin significantly promoted bone repair and improved bone formation.Conclusion: Resistin promotes OD of BMSCs by targeting TAZ through the PI3K/AKT/mTOR pathway and might provide a new therapeutic strategy for bone defect regeneration.