PKCβ expression contributes to M1 macrophage-induced impairment in the osteogenic differentiation of periodontal ligament stem cells.

Protein kinase Cβ (PRKCB) is expressed in THP-1 cells and has been found upregulated in periodontitis. Exploring the specific molecular mechanisms that promote the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) is beneficial to optimizing periodontal regeneration. THP-1 cells were induced to differentiate into macrophages, and the levels of PRKCB in macrophages with different phenotypes were examined, including PKC activity. The effect of pg-LPS induction on osteogenic differentiation of hPDLSCs was measured by measuring alkaline phosphatase, osteocalcin, osteogenic-related proteins, and mineralized nodules. Ruboxistaurin, an inhibitor of PRKCB, was used to treat M1 macrophages to examine its effect on macrophage polarization. Additionally, the cascade effect of ruboxistaurin on osteogenic differentiation was investigated by co-incubating hPDLSCs with medium from macrophages. The results indicated that PRKCB upregulation and increased PKC activity were induced in M1 macrophages upon stimulation with LPS/IFN-γ. pg-LPS resulted in decreased levels of osteogenic-related genes in hPDLSCs, accompanied by a decrease in mineralized nodules. PRKCB inhibitor reduced PKC activity, inhibited macrophage M1 polarization, and reduced M1-related inflammatory cytokine secretion. Exposure of hPDLSCs to M1 macrophage-derived conditioned medium impaired their osteogenic differentiation potentials, which was significantly attenuated by pretreatment of M1 macrophages with ruboxistaurin. Together, inhibition of PRKCB suppressed inflammatory M1 macrophage polarization, thus attenuating M1 macrophage-induced impairment in the osteogenic differentiation of hPDLSCs. These results provide a theoretical and scientific basis for optimizing the potential clinical application of hPDLSC therapy in periodontal regeneration.