[IL-6 upregulates the expression of human placental MSC SPP1 through the NF-κB signaling pathway and promotes M2 macrophage polarization].

Objective To investigate the molecular mechanism of IL-6 regulating the expression of secretory phosphoprotein 1 (SPP1) in human placental-derived mesenchymal stem cells (hfPMSCs) and influencing the polarization of macrophages. Methods hfPMSCs were prepared by enzymatic digestion and cultured in a defined, serum-free medium. The morphology of hfPMSCs was observed under a microscope, and the expression of surface markers CD14, CD34, CD45, CD73, CD90, CD105, and human leukocyte antigen DR (HLA-DR) was detected by flow cytometry. hfPMSCs were treated with IL-6 at the final dosage of 100 ng/mL for 24 hours. ELISA, Western blot, and real-time quantitative PCR were used to detect the expression of SPP1 at the protein and mRNA levels; after being treated with IL-6, hfPMSCs infected with SPP1 interference lentivirus were co-cultured with activated macrophage THP-1 cells induced by 100 ng/mL lipopolysaccharide (LPS) and 80 ng/mL phorbol 12-myristate 13-acetate (PMA), and flow cytometry was used to detect the proportion of CD11c and CD206 positive cells in THP-1 cells; hfPMSCs were treated with IL-6 and/or specific inhibitors of nuclear factor kappa B p65 (NF-κB p65), SC75741, and Western blot was used to detect the expression of genes in the NF-κB signaling pathway and SPP1. Results IL-6 significantly upregulates the expression of SPP1 in protein and mRNA levels in hfPMSCs; interference of SPP1 significantly downregulates the expression of SPP1 in hfPMSCs and significantly reduces the positive cell ratio of CD206 in co-cultured macrophages; IL-6 significantly upregulates the expression of p-p65 in hfPMSCs, activating the NF-κB signaling pathway; SC75741 significantly downregulates the expression of p-p65 and SPP1 in hfPMSCs treated with IL-6. Conclusion IL-6 upregulates the expression of SPP1 through the NF-κB signaling pathway in hfPMSCs, which enhances the capability to induce macrophages to polarize towards the M2 phenotype.