Abstract
BACKGROUND: Regulatory T (Treg) cells are essential for maintaining immune tolerance and have been implicated in tissue regeneration; however, their role in periodontal regeneration remains poorly understood. This study aimed to elucidate the effect of Treg cell-derived exosomes (Treg-Exos), particularly those carrying microRNA-21 (miR-21), on the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) and periodontal tissue regeneration. METHODS: After co-culturing Treg cells or Treg-Exos with PDLSCs respectively in vitro, the osteogenic differentiation of treated PDLSCs was assessed through Alkaline phosphatase (ALP) activity, Alizarin Red staining, and the expression of osteogenic markers runt-related transcription factor 2 (Runx-2) and Osterix. The functional role of miR-21 in Treg-Exos was assessed via gain- and loss-of-function experiments, involving transfection of Treg cells with miR-21 mimics or inhibitors. In vivo, a mice periodontal defect model was established via silk ligation and Porphyromonas gingivalis inoculation. Subsequently, Treg-Exos were locally administered into defects to assess their potential in promoting periodontal tissue regeneration. The regenerative efficacy was evaluated using micro-CT and histological analysis. RESULTS: Treg cell levels were significantly elevated in periodontitis patients compared to healthy controls. Both Treg cells and Treg-Exos markedly promoted the osteogenic differentiation of PDLSCs in vitro, as evidenced by increased ALP activity, enhanced mineralization, and upregulated Runx-2/Osterix expression. Exosomes derived from miR-21-overexpressing Treg cells further promoted PDLSC osteogenesis, whereas exosomes with miR-21 knockdown exhibited an inhibitory effect. In vivo, Treg-Exos injection alleviated periodontal damage and improved tissue morphology compared to PBS controls, as demonstrated by micro-CT and histological analyses. CONCLUSION: Treg cell-derived exosomal miR-21 promotes the osteogenic differentiation of PDLSCs, enhancing periodontal tissue regeneration in vivo, suggesting that Treg cells and their exosomal miR-21 may serve as promising therapeutic targets for periodontitis.