SHED-derived conditioned exosomes enhance the osteogenic differentiation of PDLSCs via Wnt and BMP signaling in vitro

The exosomes from human exfoliated deciduous teeth (SHED-Exos) have exhibited potential therapeutic role in dental and oral disorders. The biological effects of exosomes largely depend on cellular origin and physiological status of donor cell. In the present study, we explored the influence of conditioned exosomes from SHED with osteogenic induction on periodontal ligament stem cells (PDLSCs) in vitro. Conditioned SHED-Exos from a 3-day osteogenic supernatant were applied during PDLSCs osteogenic differentiation. We found that conditioned SHED-Exos had no cytotoxicity on PDLSCs viability assessed by CCK-8 assay. These SHED-Exos promoted PDLSCs osteogenic differentiation with deep Alizarin red staining, high alkaline phosphatase (ALP) activity and upregulated osteogenic gene expression (RUNX2, OPN and OCN). We further found BMP/Smad signaling and Wnt/β-catenin were activated by enhanced Smad1/5/8 phosphorylation and increased nuclear β-catenin protein expression. Inhibiting these two signaling pathways with specific inhibitors (cardamonin and LDN193189) remarkably weakened the enhanced osteogenic differentiation. Furthermore, Wnt3a and BMP2 were upregulated in SHED and SHED-Exos. Silencing Wnt3a and BMP2 in SHED-Exos partially counteracts the enhanced osteogenic differentiation. Our findings indicate that conditioned SHED-Exos-enhanced PDLSCs osteogenic differentiation was partly due to its carrying Wnt3a and BMP2. These data provide new insights into the use of SHED-Exos in periodontitis-induced bone defects therapy.