Distal-less homeobox 5 promotes the osteo-/dentinogenic differentiation potential of stem cells from apical papilla by activating histone demethylase KDM4B through a positive feedback mechanism

Understanding the mechanism of osteo-/dentinogenic differentiation is beneficial for jaw bone and dental tissue regeneration. DLX5 is highly expressed in dental tissue-derived mesenchymal stem cells (MSCs) and is upregulated by lysine-specific demethylase 4B (KDM4B), enabling it to regulate osteo-/dentinogenic differentiation, while the function of DLX5 in osteo-/dentinogenesis has not been thoroughly elucidated to date. Therefore, we investigated DLX5 function using stem cells from apical papilla (SCAPs). SCAPs were obtained from the human wisdom tooth. Alkaline phosphatase (ALP) assay, Alizarin red staining (ARS), quantitative analysis of calcium, osteo-/dentinogenesis-related gene expression and in vivo transplantation were used to determine the osteo-/dentinogenic differentiation potential. Luciferase and ChIP assays were used to investigate the physical relationship between DLX5 and KDM4B. DLX5 and KDM4B were upregulated during osteogenic induction and were induced by BMP4 in SCAPs. Next, we found that DLX5 enhanced ALP activity, mineralization in vitro, and the expression of dentin sialophosphoprotein (DSPP), dentin matrix acidic phosphoprotein 1 (DMP1), osteopontin (OPN), and the key transcription factor osterix (OSX). Moreover, transplant experiments showed that DLX5 promoted osteo-/dentinogenesis in vivo. Interestingly, DLX5 enhanced KDM4B transcription by directly binding with its promoter. In addition, KDM4B upregulated DLX5 in SCAPs. These results indicate that DLX5 and KDM4B are positive effectors of BMP signaling and regulate each other via a positive feedback mechanism. DLX5 enhanced osteo-/dentinogenic differentiation via upregulated KDM4B in SCAPs, suggesting that activation of the DLX5/KDM4B signaling pathway might serve as an intrinsic mechanism that promotes tissue regeneration mediated by dental-derived MSCs.