Small Extracellular Vesicles from Lipopolysaccharide-Preconditioned Dental Follicle Cells Promote Periodontal Regeneration in an Inflammatory Microenvironment

Lipopolysaccharide (LPS)-induced inflammatory microenvironment can enhance the dental follicle cells (DFCs) proliferation, differentiation, and adhesion abilities beneficial to periodontal regeneration, which possibly attributes the success to exosomes according to recent studies. This study aimed to investigate the therapeutic efficacy and underlying mechanisms of LPS-preconditioned DFC-derived small extracellular vesicles (sEVs), which enriched exosomes for periodontal regeneration in an inflammatory microenvironment. LPS preconditioning could significantly increase the secretion of sEVs derived from DFCs. Both LPS-preconditioned dental follicle cell-derived sEV (L-DsEV) and DFC-derived sEV (D-sEV) promoted the proliferation of periodontal ligament cells from periodontitis (p-PDLCs) with a dose-dependent and saturable manner and also enhanced the migration and differentiation of p-PDLCs. Furthermore, L-D-sEV showed a modest benefit than D-sEV to promote p-PDLCs differentiation. In vivo, an L-D-sEV-loaded hydrogel applied in the treatment of periodontitis was beneficial to repair lost alveolar bone in the early stage of treatment and to maintain the level of alveolar bone in the late stage of treatment in experimental periodontitis rats, which could partly decrease the expression of the RANKL/OPG ratio. In conclusion, L-D-sEV was beneficial to p-PDLCs forming an integrity periodontal tissue. The biological injectable L-D-sEV-loaded hydrogel could be used as a treatment method for experimental periodontitis in rats, promoting periodontal tissue regeneration and providing a new alternative cell therapy method for periodontal tissue regeneration.