The pivotal role of the Hes1–Piezo1  pathway in the pathophysiology of glucocorticoid-induced osteoporosis
Glucocorticoid-induced osteoporosis (GIOP) lacks fully effective treatments. This study investigated the role of Piezo1, a mechanosensitive ion channel component 1, in GIOP. We found reduced Piezo1 expression in cortical bone osteocytes from patients with GIOP and a GIOP mouse model. Yoda1, a Piezo1 agonist, enhanced the mechanical stress response and bone mass and strength, which were diminished by dexamethasone (DEX) administration in GIOP mice. RNA sequencing revealed that Yoda1 elevated Piezo1 expression by activating the key transcription factor Hes1, followed by enhanced CaM kinase II and Akt phosphorylation in osteocytes. This improved lacuno-canalicular network and reduced sclerostin production and receptor activator of nuclear factor kappa beta/osteoprotegerin ratio, which were mitigated by DEX. Comparative analysis of mouse models and human GIOP cortical bone revealed downregulation of mechano-stimulated osteogenic factors, such as osteocrin, and cartilage differentiation markers in osteoprogenitor cells. In human periosteal-derived cells, DEX suppressed differentiation into osteoblasts, but Yoda1 rescued this effect. Our findings suggest that reduced Piezo1 expression and activity in osteocytes and periosteal cells contribute to GIOP, and Yoda1 may offer a novel therapeutic approach by restoring mechanosensitivity. Overall design: To investigate the mechanisms of glucocorticoid-mediated mechanical stress response, an RNA-seq analysis was conducted comparing the mouse tibial axial loading responses between the vehicle- and DEX-treated groups over five days.