Abstract: Objective To observe the effect of miR-335-5p derived from human bone marrow mesenchymal stem cell (hBMMSCs) exosomes on osteogenic differentiation of human periodontal ligament stem cell (PDLSCs) model of periodontitis and explore its mechanism. Methods The exosomes extracted from hBMMSCs were identified by transmission electron microscopy, Western blotting and PKH67 labeling. The human PDLSC model of TNF-α-induced periodontitis were co-cultured with the extracted exosomes, and qRT-PCR was performed to detect the changes in the expressions of miR-335-5p and the mRNA levels of pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) and the osteogenic marker genes (RunX2, OCN and BMP-2). Alizarin red staining and ALP staining were used to detect the formation of calcium nodules in the treated cells, and the expression level of DKK1 protein was detected with Western blotting. Dual luciferase reporter gene assay was used to verify the targeting relationship between miR-335-5p and DKK1. Results High expressions of CD9 and CD81 were detected in the extracted hBMMSC exosomes (P<0.05). In TNF-α-induced hPDLSCs, treatment with the extracted exosomes significantly reduced the mRNA expressions of IL-1β, IL-6 and IL-8, enhanced the mRNA expressions of RunX2, OCN, and BMP-2, and promoted the formation of calcium nodules. MiR-335-5p was highly expressed in hBMMSC-derived exosomes, and overexpression of miR-335-5p significantly downregulated DKK1 protein expression, inhibited the mRNA expressions of IL-1β, IL-6 and IL-8, and promoted the mRNA expressions of osteogenic markers and the formation of calcium nodules in hPDLSCs. Conclusion HBMMSC exosome-derived miR-335-5p promotes osteogenic differentiation of hPDLSCs and inhibits the development of periodontitis by downregulating DKK1.

Key words: periodontitis; bone marrow mesenchymal stem cells; exosomes; miR-335-5p; periodontal ligament stem cells; osteogenic differentiation