In the orthodontic treatment process, orthodontic tooth movement is a mechanobiological reaction resulting from appropriate orthodontic forces, which is based on a series of periodontal tissue changes, including bone remodeling. Bone remodeling involves a dynamic equilibration between osteoblasts, which form bone, and osteoclasts, which absorb bone (Sims & Martin, 2014). A variety of cytokines, proteins, and transcription factors, such as alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), runt-related transcription factor 2 (Runx2), and osteocalcin (OCN), are involved in mediating osteoblastogenesis and bone formation (Hu et al., 2005, Leboy and Osyczka, 2005).

Osteoblasts are important in the process of Piezo1-regulated bone remodeling. As an important mechanoreceptor cell for transforming mechanical stimuli into biochemical signals, osteoblasts are responsible for the regulation of bone formation and tissue mineralization. They can also secrete bone matrix and produce the cytokines necessary for osteoclast differentiation (Wozniak et al., 2000, Yoneda et al., 2019). For example, removing Piezo1 from mice osteoblasts led to bone loss and increased bone resorption, suggesting that Piezo1 may play a role in regulating mechanoload-dependent bone formation and remodeling in osteoblasts (L. Wang, You, et al., 2020; Zhou et al., 2020). However, the mechanical response properties and the mechanism of mechanical transduction of these cytokines produced by osteoblasts remain unclear. Among many osteoblast cell lines, MC3T3-E1 is a mouse embryonic osteoblast precursor cell, which has strong osteogenic ability and the ability to differentiate into osteoblasts, chondrocytes, and other cell types and can form bone tissue in vitro. These properties make it an ideal tool for studying bone formation.

The mechanosensitive Piezo channels are large transmembrane proteins, which have been identified as non-selective mechanosensitive cation channels (Coste et al., 2010, Ge et al., 2015; Q. Zhao et al., 2016; Qiancheng Zhao et al., 2018). These proteins, which are conserved among various species, mediate mechanical responses in various cell types (Coste et al., 2012). The family of Piezo channels includes Piezo1 (Fam38A) and Piezo2 (Fam38B) in vertebrates (Coste et al., 2010). In the field of bone biology, the Piezo1 and Piezo2 channels have been shown by many previous studies to contribute to bone remodeling. In osteocytes cultured in vitro, mechanical stress activates the Piezo1–Akt pathway, which is crucial for suppressing the expression of Sost, which encodes Sclerostin (Sasaki et al., 2020). Piezo1 in osteocytes can also sense fluid shear stress (FSS) and then upregulate Wnt1 by activating YAP1 and TAZ. In vivo studies have demonstrated that knockout of Piezo1 in bone tissue cells leads to the pathological manifestation of osteoporosis in mice, which can be improved by treatment with the Piezo1 agonist Yoda1 (X. Li et al., 2019). The osteogenesis of osteoblasts is disrupted by Piezo1 knockout, severely impairing bone structure and strength (Sun et al., 2019). In hydrostatic pressure-treated human marrow mesenchymal stem cells, Piezo1 senses the mechanical stimuli and activates ERK1/2 and p38 MAPK signaling, which in turn upregulate BMP-2, Runx2, and Osterix to promote osteoblast differentiation (Sugimoto et al., 2017). TRPV4 and Piezo1 modify the proliferation of osteoblasts under fluid shear force, suggesting their involvement in the mechanical transduction of osteoblasts. Additionally, TRPV4-dependent Ca2+ response under fluid shear stress (FSS) can be generated by Yoda1 through the activation of Piezo1 (Yoneda et al., 2019). Meanwhile, the osteoclastogenesis of periodontal ligament cells (PDLCs) in periodontal tissues resulting from mechanical load is mediated by the Piezo1 channel. The NF–kB signaling pathway plays a mediating role in this process (Jin et al., 2015).

Although Piezo1 channels are now widely recognized for their influence on cellular mechanotransduction in bone biology, limited information is available regarding the factors and signaling pathways involved in Piezo1-mediated effects in osteoblasts. Thus, we aimed to evaluate the impact of Piezo1 on the osteogenic and osteoclast factors in osteoblasts under mechanically load.