Interleukin-1β disrupts macrophage mitochondrial protein homeostasis and PDLSC osteogenic differentiation

Aging is a complex, multi-dimensional biological process characterized by dysregulation of mitochondrial protein homeostasis and elevated SASP-related inflammatory factors (IL-1β). This study investigates the biological mechanisms by which macrophage polarization in the aging-associated inflammatory microenvironment suppresses the osteogenic differentiation of human periodontal ligament stem cells (PDLSCs). A Transwell indirect co-culture system of PDLSCs and THP-1-derived macrophages was established. The inflammatory microenvironment was mimicked by treating the co-culture system with IL-1β (6.25 ng/mL), while IL-4/IL-13 (20 ng/mL each) were used to induce M2 macrophage polarization. Mitochondrial function was assessed by detecting reactive oxygen species (ROS) levels, ATP content, and mitochondrial Complex V activity. The expression of mitochondrial protein homeostasis-related genes was quantified using quantitative real-time PCR (qRT-PCR). Osteogenic differentiation of PDLSCs was assessed via alkaline phosphatase (ALP) staining/activity assay, Alizarin Red S staining, and qRT-PCR detection of osteogenic markers (RUNX2, OCN). IL-1β treatment significantly increased ROS levels and decreased ATP content and mitochondrial Complex V activity in both macrophages and PDLSCs. qRT-PCR results showed that IL-1β downregulated the expression of TIMM50, DNAJC19, XPNPEP3, and HTRA2, while upregulating MIPEP in macrophages; in PDLSCs, only TIMM50 and DNAJC19 were significantly downregulated. Osteogenic differentiation assays demonstrated that IL-1β-induced M1 macrophage polarization significantly reduced ALP staining intensity/activity, calcium nodule formation, and the mRNA expression of RUNX2 and OCN in PDLSCs. However, IL-4/IL-13-induced M2 polarization did not reverse these inhibitory effects or enhance osteogenic differentiation. An aging-associated inflammatory microenvironment, established via IL-1β treatment, impairs mitochondrial function and alters mitochondrial protein homeostasis-related gene expression, which subsequently modulates macrophage polarization and suppresses the osteogenic differentiation of PDLSCs. These findings provide a mechanistic basis for SASP-mediated periodontal regenerative decline in aging.