Semaphorin 3A Induces Odontoblastic Phenotype in Dental Pulp Stem Cells

Objectives: In cases of pulp exposure due to deep dental caries or severe traumatic injuries, existing pulp capping materials have a limited ability to reconstruct dentin/pulp complexes. Therefore, the development of more effective therapeutic agents for direct pulp capping has been required. Here, we investigated the effects of Semaphorin 3A (Sema3A) on various functions of human dental pulp stem cells (DPSCs) in vitro and reparative dentin formation in a rat dental pulp exposure model in vivo.
Methods: The expression of Sema3A and its receptors, Neuropilin 1 and Plexins (PlxnA1 or A2) in human DPSCs was examined by semi-quantitative RT-PCR, immunofluorescence staining and western blotting analysis. The effects of Sema3A on cell migration, chemotaxis, proliferation and odontoblastic differentiation of DPSCs were examined by scratch wound healing assay, transwell assay, WST-1 proliferation assay, quantitative RT-PCR and Alizarin Red S staining, respectively. The capacity of Sema3A to promote reparative dentin formation was assessed using a rat dental pulp exposure model, when it was applied as a direct pulp capping agent. Nuclear accumulation of β-catenin, the expression of FARP2 gene and activated Rac1 in Sema3A-treated DPSCs were examined by immunofluorescence staining, western blotting analysis, quantitative RT-PCR and Rac1 pull-down assay, respectively.
Results: Sema3A and its receptors were expressed in rat dental pulp tissues and human DPSCs. Sema3A promoted cell migration, chemotaxis, proliferation and odontoblastic differentiation of human DPSCs. In a rat dental pulp exposure model, Sema3A facilitates reparative dentin formation with dentin tubules and well-aligned odontoblast-like cell layer after direct pulp capping treatment. Exogenous application of Sema3A to human DPSCs increased nuclear accumulation of β-catenin, and also induced the expression of FARP2 gene and the activation of Rac1.
Conclusions: Sema3A plays crucial roles in various events associated with dentin regeneration, probably via canonical Wnt/β-catenin signaling. Therefore, Sema3A might be an alternative agent for direct pulp capping.