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BACKGROUND: Interleukin-4 can promote the osteogenic effect of bone substitute materials, but its molecular mechanism is not yet clear. Further elucidating the mechanism of interleukin-4 promoting osteogenic effect can help find safe, economical, and effective methods for the regeneration treatment of alveolar bone defects in patients. OBJECTIVE: To explore the effect of interleukin-4 intervention on polarization transformation of macrophages and osteogenic differentiation of bone marrow mesenchymal stem cells and its possible mechanism. METHODS: RAW264.7 cells in the M1 group were induced with interferon gamma + lipopolysaccharide for 24 hours. RAW264.7 cells in the interleukin-4+M1 group were induced with interferon gamma + lipopolysaccharide for 24 hours and then interleukin-4 was added for 24 hours. RAW264.7 cells in the interleukin4+AG+M1 group were induced with interferon gamma + lipopolysaccharide for 24 hours, and then interleukin-4 and AG-490, a JAK/STAT pathway inhibitor, were added for 24 hours. After intervention, immunofluorescence staining was used to analyze the expression of inducible nitric oxide synthase and CD206, the phenotypic marker protein of macrophages. ELISA kit was used to detect the expression of interleukin-10 and tumor necrosis factor-α in the supernatant of cell culture. The gene expressions of nodular receptor protein-3 (NLRP3), interleukin-1β, and caspase-1 were detected by RT-qPCR. The expression levels of tyrosine protein kinase 1 (JAK1)/ phosphorylated tyrosine protein kinase 1 (p-JAK1), signal transduction and transcription activator 6 (STAT6)/phosphorylated signal transduction and transcription activator 6 (p-STAT6), NLRP3, pro-interleukin-1β and pro-caspase-1 were detected by western blot assay. Then, RAW264.7 cells in the above four groups were indirectly co-cultured with bone marrow mesenchymal stem cells by transwell for 24 hours, followed by alkaline phosphatase staining and alizarin red staining. The mRNA expressions of alkaline phosphatase, collagen type I, and osteocalcin were detected by RT-qPCR. RESULTS AND CONCLUSION: (1) Immunofluorescence and ELISA results showed that interleukin-4 intervention could promote the expression of CD206 and interleukin-10 in M2 macrophages, and inhibit the secretion of inducible nitric oxide synthase and tumor necrosis factor-α. (2) RT-qPCR results showed that interleukin-4 could suppress the expression of NLRP3, interleukin-1β, and caspase-1 mRNAs. (3) Western blot assay showed that interleukin-4 could promote the expression of JAK1/p-JAK1, STAT6/p-STAT6 and NLRP3 proteins. (4) The alkaline phosphatase staining and alizarin red staining of bone marrow mesenchymal stem cells co-cultured with the interleukin-4+M1 group were significantly enhanced, and the mRNA expressions of alkaline phosphatase, collagen type I, and osteocalcin were significantly increased. It is concluded that interleukin-4 may inhibit the activation of NLRP3 by up-regulating JAK1/STAT6 pathway, thus promoting the transformation of macrophages from M1 polarization to M2 polarization, and finally enhancing the osteogenic differentiation ability of bone marrow mesenchymal stem cells. [ABSTRACT FROM AUTHOR]

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