METTL3-m6A methylase regulates the osteo-/odontogenic potential of stem cells from apical papilla via NFIC in apical periodontitis

Stem cells from the apical papilla (SCAPs) show strong odontogenic ability and can form root dentin. However, the underlying mechanisms that control the odontogenic differentiation of SCAPs in an inflammatory environment need further exploration. In the present study, we explored the regulatory role of METTL3 in the differentiation of SCAPs originating from tooth with apical periodontitis. Stem cells from the apical papilla derived from healthy teeth (SCAPs) and teeth with apical periodontitis (AP-SCAPs) were successfully isolated and cultured. The expressions of tumor necrosis factor-a (TNF-a) and interleukin-6 (IL-6) were higher in AP-SCAPs. A decrease in METTL3 expression accompanied the decreased osteo-/odontogenic differentiation ability of AP-SCAPs. Exploring the role of METTL3 on the osteo-/odontogenic differentiation of AP-SCAPs revealed that overexpression of METTL3 upregulated the odontogenic ability of AP-SCAPs. However, silencing METTL3 exerted the opposite effect. Overexpression of METTL3 suppressed the expression of TNF-α and IL-6 in AP-SCAPs, whereas knockdown of METTL3 in these cells enhanced TNF-α and IL-6 expression. METTL3 regulates the osteo-/odontogenic differentiation of SCAPs and modulates their inflammatory response. Furthermore, overexpression of METTL3 upregulated the methylation level, mRNA, and protein expression of nuclear factor-IC (NFIC) during mineralization induction. NFIC silencing attenuated osteo-/odontogenic differentiation of METTL3-overexpressed AP-SCAPs. In conclusion, METTL3-mediated-m6A upregulated the odontogenic differentiation of AP-SCAPs via NFIC. This paper elucidates a novel mechanism regulating the odontogenic differentiation of AP-SCAPs, and METTL3 may be a new target for regenerative endodontic treatment.