PD-1 Suppresses the Osteogenic and Odontogenic Differentiation of Stem Cells from Dental Apical Papilla via Targeting SHP2/NF-κB Axis

Abstract

Abstract Stem cells from the apical papilla (SCAPs) are important for tooth root development and regeneration of root dentin. Here, we examined the expression of programmed cell death protein-1 (PD-1) in SCAPs and investigated the effects of PD-1 on odontogenic and osteogenic differentiation, as well as the relationship between PD-1 and SHP2/NF-κB signals. SCAPs were obtained and cultured in the related medium. The proliferation ability was evaluated by the cell counting kit 8 (CCK-8) and the 5-ethynyl-20-deoxyuridine (EdU) assay. Alkaline phosphatase (ALP) activity assay, ALP staining, Western blot, real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR), Alizarin Red S (ARS) staining, and immunofluorescence (IF) staining were performed to explore the osteo/odontogenic potential and the involvement of SHP2/NF-κB pathways. Besides, we transplanted SCAPs components into mouse calvaria defects to evaluate osteogenesis in vivo. We found that human SCAPs expressed PD-1 for the first time. PD-1 knockdown enhanced the osteo/odontogenic differentiation of SCAPs by suppressing the SHP2 pathway and activating the NF-κB pathway. Overexpression of PD-1 inhibited the osteogenesis and odontogenesis of SCAPs via activation of SHP2 signal and inhibition of the NF-κB pathway. PD-1 activated SHP2 signal to block NF-κB signal and then played a vital role in osteo/odontogenic differentiation of SCAPs.