Effect of Dental Follicle Stem Cells on Dental Pulp Cells

Objectives: Lipopolysaccharide (LPS) infection triggers inflammatory cascade, and thus reducing the regenerative ability of dental pulp cells (DPCs). Dental follicle stem cells (DFSCs), possessing stronger immunomodulatory effects than other odontogenic cells, are capable of regulating inflammation and promoting tissue repair through the paracrine pathway. This study aims to investigate the paracrine role of DFSCs on LPS challenged DPCs.
Methods: Conditioned medium (CM) was generated from rat DFSCs. LPS (0.5 mg/L) was used for establishment of inflamed DPCs. Inflammatory cytokine expressions of DPCs were measured by RT-PCR following CM treatment. Activation of the MAPK and NF-κB pathway were analyzed by western blot and immunofluorescence staining. The effect of CM on the regenerative capacity of inflamed DPCs were also examined by multiple assays.
Results: We found that CM suppressed the synthesis of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6), whereas promoted the cellular production of anti-inflammatory factors (IL-10 and TGF-β) in LPS treated DPCs. CM repressed ERK MAPK and p38 MAPK phosphorylation, but did not affect JNK in LPS-activated DPCs. In addition, the NF-κB pathway was also deactivated after application of CM. Cell proliferation, viability, migration, and odontoblastic ability in vitro were significantly enhanced upon incubation with CM. Production of TGF-β3 and Thrombospondin-1 (TSP-1) were detected in CM. Furthermore, we demonstrated that TGF-β3 and TSP-1 promoted cell viability and migration of DPCs, and that TGF-β3 stimulated the osteogenic differentiation of DPCs.
Conclusions: Taken together, our study demonstrated that the paracrine factors secreted by DFSCs could inhibit the inflammatory translation initiation of DPCs via p38/ERK MAPK/NF-κB signaling pathway, and significantly promote the regenerative capacity of DPCs, which might be used in treatment of pulpitis.