Abstract
ObjectivesSteroid-induced osteoporosis (SIOP) is a secondary osteoporosis, which is a systemic bone disease characterized by low bone mass, bone microstructure damage, increased bone fragility, and easy fracture. However, the specific mechanism remains unclear. Glucocorticoid-induced death of osteoblasts and bone marrow mesenchymal stem cells (BMSCs) is an important factor in SIOP. Ferroptosis is an iron-dependent programmed cell death that differs from apoptosis, cell necrosis, and autophagy, which can be induced by many factors. Herein, we aimed to explore whether glucocorticoids (GCs) cause ferroptosis in BMSCs and determine possible treatment pathways and mechanisms of action. Melatonin (MT), a hormone secreted by the pineal gland, displays strong antioxidant abilities to scavenge free radicals and alleviates ferroptosis in many tissues and organs. MethodsIn this study, we used high-dose dexamethasone (DEX) to observe whether glucocorticoids induced ferroptosis in BMSCs. We then assessed whether MT can inhibit the ferroptotic pathway, thereby providing early protection against GC-induced SIOP, and investigated the signaling pathways involved.ResultsIn vitro experiments showed that MT intervention significantly improved GC-induced ferroptosis in BMSCs and significantly improved SIOP in vivo. Pathway analysis showed that MT improves ferroptosis by activating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) axis. MT upregulates expression of PI3K, which is an important regulator of ferroptosis resistance. PI3K activators mimic the anti-ferroptosis effect of MT, but after blocking the PI3K pathway, the effect of MT is weakened. Obviously, MT can protect against SIOP induced by GC. Notably, even after GC-induced ferroptosis begins, MT can confer protection against SIOP. ConclusionOur research confirms that GC-induced ferroptosis is closely related to SIOP. Melatonin can inhibit ferroptosis by activating the PI3K-AKT-mTOR signaling pathway, thereby reducing the occurrence of steroid-induced osteoporosis. Therefore, MT may provide a novel strategy for preventing and treating SIOP.
In VivoTracking of Systemically Administered Allogeneic Bone Marrow Mesenchymal Stem Cells in Normal Rats through Bioluminescence Imaging
