Extracellular Vesicles From Dental Pulp Cells Promote Osteogenic Differentiation in Periodontal Ligament Cells

AimPeriodontal osseous defects are mainly caused by periodontitis, which seriously affects the quality of patient life. Dental pulp cells (DpCs)-derived extracellular vesicles (EVs) can effectively promote tissue regeneration. Homeobox A9 (HOXA9) mRNA is abundant in EVs derived from DSCs, which may be related to promoting alveolar bone regeneration, but the specific mechanism is unclear. We aimed to elucidate the mechanism through which HOXA9 from DPCs-derived EVs can impact the osteogenic differentiation of periodontal ligament cells (PDLCs).MethodsDPCs-derived EVs were isolated and characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot. Lipopolysaccharide (LPS) was employed to induce the inflammatory environment. Cell viability was assessed by CCK8 assay. Calcium deposition was determined by Alizarin red staining. H3K27ac enrichment in the FLI1 enhancer region and the interaction between C/EBP alpha, HOXA9, and FLI1 were analyzed by ChIP assay. The interaction between HOXA9 and FLI1 enhancer in 293T cells was analyzed by dual luciferase reporter gene assay.ResultsDPCs-derived EVs promoted PDLC osteogenesis under LPS treatment and increased HOXA9 expression in PDLCs. HOXA9 knockdown in DPCs reversed the promoting effect of DPCs-derived EVs on PDLC osteogenic differentiation. HOXA9 from DPCs-derived EVs promoted H3K27ac enrichment in the FLI1 enhancer region by facilitating HOXA9 competitively binding FLI1 enhancer region with C/EBP alpha. Moreover, HOXA9 from DPCs-derived EVs promoted PDLC osteogenesis by activating the PI3K/AKT pathway through upregulating FLI1.ConclusionHOXA9 from DPCs-derived EVs promoted PDLC osteogenic differentiation by activating the PI3K/AKT pathway through promoting H3K27ac enrichment in the FLI1 enhancer region and upregulating FLI1. Our study identified a previously unknown mechanism that HOXA9/FLI1 signaling axis participates in the processes of EVs derived from DPCs to treat bone tissue injury. Our research presents a theoretical basis for using EVs derived from DPCs to treat bone tissue injury.ConclusionHOXA9 from DPCs-derived EVs promoted PDLC osteogenic differentiation by activating the PI3K/AKT pathway through promoting H3K27ac enrichment in the FLI1 enhancer region and upregulating FLI1. Our study identified a previously unknown mechanism that HOXA9/FLI1 signaling axis participates in the processes of EVs derived from DPCs to treat bone tissue injury. Our research presents a theoretical basis for using EVs derived from DPCs to treat bone tissue injury.