Dental pulp stem cell‑derived extracellular vesicles loaded with hydrogels promote osteogenesis in rats with alveolar bone defects

Alveolar bone defects caused by inflammation, trauma and tumors adversely affect periodontal health, causing tooth loosening or dentition defects, thus affecting denture or implant repair. Advancements in tissue engineering technology and stem cell biology have significantly improved the regenerative reconstruction of alveolar bone defects. The multiple trophic activities of extracellular vesicles (EVs) produced by mesenchymal stem cells play important roles in exerting their therapeutic effects. Several studies have reported the role of dental pulp stem cells (DPSCs) in bone regeneration, but the regenerative effects of DPSC‑EVs on alveolar bone defects are unclear. In the present study, the osteogenic effects of DPSC‑EVs on Hertwig's epithelial root sheath (HERS) cells <i>in vitro</i> and their osteoinductive effects in an alveolar bone defect rat model were investigated. The results showed that DPSC‑EVs significantly promoted the expression of osteogenic genes, such as runt‑related transcription factor 2 and alkaline phosphatase, and increased the osteogenic differentiation capability of HERS. These findings suggested that transforming growth factor β1 inhibition decreased DPSC‑EV‑induced Smad, MAPK and ERK phosphorylation in HERS. <i>In vivo</i>, DPSC‑EV‑loaded hydrogels were transplanted into the alveolar sockets of Sprague‑Dawley rats and observed for eight weeks. The new bone grew concentrically in the DPSC‑EV or DPSC‑EV‑loaded hydrogel group, with greater bone mass than that in the control group, and the bone volume/total volume increased notably. The results confirmed the osteogenic and osteoinductive effects of DPSC‑EVs and DPSC‑Exo‑loaded hydrogels on alveolar bone defects. Due to their low immunogenicity, high stability, good biocompatibility and osteogenic propensity, DPSC‑EV‑loaded hydrogels are a safe cell‑free therapeutic approach for defective alveolar bone regeneration.