PIEZO1 promotes odontoblast-mediated reactionary dentinogenesis via Ca2+-SEMA3A axis

The odontoblasts are specialized cells responsible for dentin synthesis and nociceptive signal detection in response to external stimuli. Recent studies have shown that the mechanosensitive ion channel PIEZO1 is involved in bone formation and remodeling through the influx of calcium ions, and it is abundantly expressed in odontoblasts. However, the specific role of PIEZO1 in reactionary dentinogenesis by odontoblasts and the underlying mechanisms still remain elusive. In this study, we found intense PIEZO1 expression in the plasma membrane and cytoplasm of odontoblasts in human and mouse mandibular molars, and human odontoblast-like cells (hOBLCs). In hOBLCs, PIEZO1 positively regulated DSPP, DMP1, and COL1A1 expression through the Ca2+/PI3K-Akt/SEMA3A signaling pathway. Additionally, exogenous SEMA3A supplementation effectively reversed reduced mineralization capacity in PIEZO1-knockdown hOBLCs. In vivo, Piezo1 expression peaked at day 7 and returned to baseline at day 21 in a wild-type (WT) mice dentin injury model, with Sema3a presenting a similar expression pattern. To investigate the specific role of PIEZO1 in reactionary dentinogenesis, mice with a conditional knockout of PIEZO1 in odontoblasts were generated, and no significant differences of teeth phenotypes were observed between the control and conditional knockout (cKO) mice. Nevertheless, cKO mice exhibited reduced reactionary dentin formation, and decreased Sema3a and Dsp positive staining after dentin injury, indicating impaired dental pulp repair mediated by odontoblasts. In summary, these findings suggest that PIEZO1 enhances mineralization capacity of hOBLCs in vitro via the Ca2+/Akt/SEMA3A signaling pathway and contributes to dental pulp repair through enhancing reactionary dentinogenesis in vivo. To investigate the signaling pathways involved in the regulation of PIEZO1 on odontoblasts, we established human odontoblast-like cells (hOBLCs) in which PIEZO1 was either activated by Yoda1 or knocked down by small interfering RNA (siRNA) sequences. We then performed gene expression profiling analysis using data obtained from RNA-seq of hOBLCs under different treatments.