Involvement of miR-146a-5p/neurogenic locus notch homolog protein 1 in the proliferation and differentiation of STRO-1+ human dental pulp stem cells: The effect of miR-146a-5p in STRO-1+hDPSCs

: Dental pulp stem cells (DPSCs) and stem cells from the apical papilla (SCAPs) are oral mesenchymal stem cells capable of self-renewal and have a potential for multilineage differentiation. Increasing evidence shows that microRNAs (miRNAs) play important roles in stem cell biology. Here, we focused on exploring miR-146a-5p and its relationship to the undifferentiated status of STRO-1+ SCAPs and STRO-1+ DPSCs, as well as its role during STRO-1+ DPSC differentiation and proliferation. Our data indicated that baseline miR-146a-5p expression is significantly lower in STRO-1+ SCAPs than in STRO-1+ DPSCs and increased in the latter during osteogenic induction. Moreover, we identified miR-146a-5p as a key miRNA that promotes osteo/odontogenic differentiation of STRO-1+ DPSCs and attenuates cell proliferation. Additionally, it was observed that STRO-1+ DPSC mineralization results in the downregulation of notch receptor 1 (NOTCH1) and hes family bHLH transcription factor 1 (HES1). Interference with neurogenic locus notch homolog protein 1 (Notch 1) signaling was verified to enhance differentiation and suppress STRO-1+ DPSC proliferation. It was further observed that miR-146a-5p directly targets the 3'-untranslated region (3'-UTR) of NOTCH1 and inhibits expression of both NOTCH1 and HES1mRNAs and Notch 1 and transcription factor HES-1 (HES-1) proteins in STRO-1+ DPSCs. We conclude that miR-146a-5p exerts its regulatory effect on STRO-1+ DPSC differentiation and proliferation partially by suppressing Notch signaling.