Osteoclast differentiation plays a key role in orthodontic tooth movement (OTM). We aimed to explore the role of human periodontal ligament (hPDL) extracellular vesicles (EVs) in osteoclast differentiation and OTM.

The hPDL cells were exposed to 4.0 g/cm2 compression force (CF) and the hPDL-EVs were collected. The peripheral blood mononuclear cells were isolated, purified, and induced osteoclast differentiation. The OTM rat model was established through excess orthodontic force. Dual-luciferase reporter gene assay verified the targeting effect of miR-28 on RUNX1. In addition, tartrate-resistant acid phosphase (TRAP) staining, immunofluorescence, western blot, and quantitative real-time PCR were also carried out.

CF pretreated hPDL-EVs promoted osteoclast differentiation and down-regulated RUNX1 levels in in vitro and in vivo experiments. The addition of CF-hPDL-EVs also elevated tooth movement in OTM rats. Besides, miR-28 was significantly up-regulated in CF-pretreated hPDL-EVs. In addition, RUNX1 was negatively regulated by miR-28. Moreover, the addition of CF-lenti-miR-28 inhibitor-Evs down-regulated the expression of osteoclast marker genes and the number of TRAP positive (+) multinucleated cells (MNCs) in vitro. Furthermore, in vivo experiments confirmed that CF-lenti-miR-28 inhibitor-Evs injection down-regulated the number of TRAP (+) MNCs and inhibited tooth movement of OTM rats.

CF-treated hPDL-EVs promoted osteoclast differentiation by transporting miR-28 and inhibiting the expression of RUNX1, which provides new insight into the specific mechanism of hPDL-Evs affecting osteoclast differentiation.