The extracellular environment regulates the dynamic behaviors of cells. However, the effects of hydrostatic pressure (HP) on cell fate determination of mesenchymal stem cells (MSCs) are not clearly understood. Here, we established a cell culture chamber to control HP. Using this system, we found that the promotion of osteogenic differentiation by HP is depend on bone morphogenetic protein 2 (BMP2) expression regulated by Piezo type mechanosensitive ion channel component 1 (PIEZO1) in MSCs. The PIEZO1 was expressed and induced after HP loading in primary MSCs and MSC lines, UE7T-13 and SDP11. HP and Yoda1, an activator of PIEZO1, promoted BMP2 expression and osteoblast differentiation, whereas inhibits adipocyte differentiation. Conversely, PIEZO1 inhibition reduced osteoblast differentiation and BMP2 expression. Furthermore, Blocking of BMP2 function by noggin inhibits HP induced osteogenic maker genes expression. In addition, in an in vivo model of medaka with HP loading, HP promoted caudal fin ray development whereas inhibition of piezo1 using GsMTx4 suppressed its development. Thus, our results suggested that PIEZO1 is responsible for HP and could functions as a factor for cell fate determination of MSCs by regulating BMP2 expression.

Signal transmission from the mechanical forces to the various intracellular activities is a fundamental process during tissue development. Despite their critical role, the mechanism of mechanical forces in the biological process is poorly understood. In this study, we demonstrated that in the response to hydrostatic pressure (HP), the piezo type mechanosensitive ion channel component 1 (PIEZO1) is a primary mechanosensing receptor for odontoblast differentiation through coordination of the WNT expression and ciliogenesis. In stem cells from human exfoliated deciduous teeth (SHED), HP significantly promoted calcium deposition as well as the expression of odontogenic marker genes, PANX3 and DSPP, and WNT related-genes including WNT5b and WNT16, whereas HP inhibited cell proliferation and enhanced primary cilia expression. WNT signaling inhibitor XAV939 and primary cilia inhibitor chloral hydrate blocked the HP-induced calcium deposition. The PIEZO1 activator Yoda1 inhibited cell proliferation but induced ciliogenesis and WNT16 expression. Interestingly, HP and Yoda1 promoted nuclear translocation of RUNX2, whereas siRNA-mediated silencing of PIEZO1 decreased HP-induced nuclear translocation of RUNX2. Taken together, these results suggest that PIEZO1 functions as a mechanotransducer that connects HP signal to the intracellular signalings during odontoblast differentiation.

Abstract. In this study, we examined the effect of forced mastication on neurogenesis in the hippocampal dentate gyrus (DG) of adult mice. Six-week-old mice were subjected to either a hard or normal diet for 13 weeks. They received a daily injection of bromodeoxyuridine (BrdU) for 12 consecutive days beginning at 14 weeks of age. The number of BrdU-positive cells in the DG was counted 1 day after and 5 weeks after the final BrdU injection. The number of BrdU-positive cells 1 day after injection did not differ between the 2 diet groups. However, the number of BrdU-positive cells in the group fed the hard diet was significantly increased 5 weeks after BrdU injection compared to the group fed the normal diet. The results of the Morris water maze test showed that mice fed a hard diet required significantly less time to reach the platform than the control mice when tested at 10 days. Moreover, mice in the group fed the hard diet spent significantly more time in the former platform area than the group fed the normal diet, indicating that hard diet feeding improved spatial memory compared to normal diet feeding. Real-time PCR analysis showed that the expression of glutamate receptor 1 mRNA was significantly increased in the group fed the hard diet compared with the group fed the normal diet. These results suggest that mastication increases the survival of adult neural stem cells in the hippocampal DG.

Wound healing is a dynamic process that involves highly coordinated cellular events, including proliferation and migration. Oral gingival fibroblasts serve a central role in maintaining oral mucosa homeostasis, and their functions include the coordination of physiological tissue repair. recently, surface pre-reacted glass-ionomer (S-PRG) fillers have been widely applied in the field of dental materials for the prevention of dental caries, due to an excellent ability to release fluoride (F). In addition to F, S-PRG fillers are known to release several types of ions, including aluminum (Al), boron (B), sodium (Na), silicon (Si) and strontium (Sr). However, the influence of these ions on gingival fibroblasts remains unknown. The aim of the present study was to examine the effect of various concentrations of an S-PRG filler eluate on the growth and migration of gingival fibroblasts. The human gingival fibroblast cell line HGF-1 was treated with various dilutions of an eluent solution of S-PrG, which contained 32.0 ppm al, 1,488.6 ppm B, 505.0 ppm Na, 12.9 ppm Si, 156.5 ppm Sr and 136.5 ppm F. Treatment with eluate at a dilution of 1:10,000 was observed to significantly promote the migration of HGF-1 cells. in addition, the current study evaluated the mechanism underlying the mediated cell migration by the S-PRG solution and revealed that it activated the phosphorylation of extracellular signal-regulated kinase 1/2 (erK1/2), but not of p38. Furthermore, treatment with a MEK inhibitor blocked the cell migration induced by the solution. Taken together, these results suggest that S-PRG fillers can stimulate HGF-1 cell migration via the erK1/2 signaling pathway, indicating that a dental material containing this type of filler is useful for oral mucosa homeostasis and wound healing.

Dental pulp cells (DPCs), including dental pulp (DP) stem cells, play a role in dentine repair under certain conditions caused by bacterial infections associated with caries, tooth fracture and injury. Mesenchymal stem cells (MSCs) have also been shown to be involved in this process of repair. However, the mechanisms through which MSCs are recruited to the DP have not yet been elucidated. Therefore, the aim of the present in vitro study was to investigate whether stromal cell-derived factor 1α (SDF1)-C-X-C chemokine receptor type 4 (CXCR4) signaling is involved in tissue repair in the DP of deciduous teeth. A single-cell clone from DPCs (SDP11) and UE7T-13 cells were used as pulp cells and MSCs, respectively. The MG-63 and HuO9 cells, two osteosarcoma cell lines, were used as positive control cells. Reverse transcription polymerase chain reaction (RT-PCR) revealed that all cell lines (SDP11, UE7T-13 MG-63 and HuO9) were positive for both SDF1 and CXCR4 mRNA expression. Moreover, immunocytochemical analysis indicated that SDF1 and CXCR4 proteins were expressed in the SDP11 and UE7T-13 cells. SDF1 was also detected in the cell lysates (CLs) and conditioned medium (CM) collected from the SDP11 and UE7T-13 cells, and AMD3100, a specific antagonist of CXCR4, inhibited the migration of the UE7T-13 cells; this migration was induced by treatment with CM, which was collected from the SDP11 cells. In addition, real-time PCR showed that the expression of SDF1 in the SDP11 cells was inhibited by treatment with 20 ng/ml fibroblast growth factor (FGF)-2, and exposure to AZD4547, an inhibitor of the FGF receptor, blocked this inhibition. Collectively, these data suggest that SDF1 produced by DP plays an important role in homeostasis, repair and regeneration via the recruitment of MSCs.