Macrophage Migration Inhibitory Factor(MIF) Inhibitor ISO-1 Promotes Staphylococcal Protein A-induced Osteogenic Differentiation By Inhibiting NF-κB Signaling Pathway

Objectives: Osteomyelitis is among the most difficult to treat diseases in the field of orthopedics,and there is a lack of effective treatment modalities.Exploring the mechanisms of its development is beneficial for finding molecular targets for treatment.Increasing evidence suggests that macrophage migration inhibitory factor(MIF),as a proinflammatory mediator,is not only involved in various pathophysiological processes of inflammation but also plays an important role in osteogenic differentiation,while its specific regulatory mechanism in osteomyelitis remains unclear.Methods: In the present study,staphylococcal protein A(SPA)-treated rat bone marrow mesenchymal stem cells(r BMSCs)were used to construct cell models of osteomyelitis.Rat and cell models of osteomyelitis were used to validate the expression levels of MIF,and to further explore the regulatory mechanisms of the MIF inhibitor methyl ester of(S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid(ISO-1)and MIF knockdown(MIF-KD)on cell model of osteomyelitis toward osteogenic differentiation.Results: We found that the expression level of MIF was upregulated in rat and cell models of osteomyelitis and subsequently demonstrated by the GSE30119 dataset that the expression level of MIF was also significantly upregulated in patients with osteomyelitis.Furthermore,SPA promotes MIF expression in r BMSCs while inhibiting the expression of osteogenic-related genes such as Runt-related transcription factor 2(RUNX2),osteocalcin(OCN),osteopontin(OPN)and collagen type-1(COL-1)through activation of the nuclear factor kappa-B(NF-κB)pathway.In vivo,we further demonstrated that local injection of i SO-1 significantly increased the osteogenic activity in rat model of osteomyelitis.Importantly,we also demonstrated that MIF knockdown and the MIF inhibitor i SO-1 reversed the SPA-mediated inhibition of osteogenic differentiation of r BMSCs by inhibiting the activation of the NF-κB pathway,as evidenced by the upregulation of osteogenic-related gene expression and enhanced bone mineralization.Conclusions: ISO-1 and MIF-KD can reverse the SPA-mediated inhibition of osteogenic differentiation in the r BMSCs model of osteomyelitis by inhibiting the NF-κB signaling pathway,providing a potential therapeutic target for osteomyelitis.