ED-71 Protects Against Glucocorticoid-Triggered Osteoporosis by Influencing Osteoblast Differentiation through Notch and Wnt/β-Catenin Pathways

Prolonged exposure to glucocorticoids frequently results in glucocorticoid-induced osteoporosis (GIOP). This work investigated whether eldecalcitol (ED-71), a new active analog of vitamin D3, can counteract GIOP and sought to clarify the molecular pathways responsible for its protective action. A GIOP mouse model was generated by administering methylprednisolone (MPED) or dexamethasone (DEX) intraperitoneally to C57BL/6 mice, while ED-71 was concurrently delivered by oral gavage. Bone morphology, microarchitectural characteristics, newly synthesized bone, and osteogenic marker expression were assessed using HE staining, micro-CT, calcein/tetracycline double labeling, and IHC analysis. In vitro experiments employed MC3T3-E1 pre-osteoblasts exposed to DEX, and osteogenic differentiation and mineral deposition were examined through ALP staining, AR staining, qPCR, Western blotting, and immunofluorescence. ED-71 alleviated the loss of bone mass and defects in microstructural parameters observed in GIOP mice, while simultaneously enhancing bone formation and stimulating osteoblast function, accompanied by suppression of osteoclast activity. In cultured MC3T3-E1 cells, ED-71 restored osteogenic differentiation and mineralization hindered by DEX and markedly increased the expression of osteogenesis-associated molecules. ED-71 exposure also elevated GSK3-β and β-catenin levels while diminishing Notch expression. The use of the Wnt pathway inhibitor XAV939 or forced Notch activation eliminated the pro-osteogenic influence of ED-71. ED-71 counteracts GIOP by promoting osteogenic differentiation through coordinated modulation of Notch and Wnt/GSK-3β/β-catenin signaling pathways. These findings indicate that ED-71 holds promising translational potential as a therapeutic strategy for preventing GIOP.