Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025096
Ferroptosis, a novel form of regulated necrosis, has drawn the attention of the scientific community. Nevertheless, few studies have focused on the impact of ferroptosis on MC3T3-E1 cells in the context of steroid-induced osteonecrosis of the femoral head (SONFH). In this study, we explore the relationship between the degree of ferroptosis induced by dexamethasone (Dex) and the expression of silent information regulatory protein 1 (Sirt1). The results indicate that the ferroptosis level induced by Dex is mediated by the downregulation of Sirt1. Overexpression of Sirt1 increases the levels of the ferroptosis-related proteins SLC7A11 and GPX4 in MC3T3-E1 cells following Dex exposure. Moreover, the effect of Dex on Sirt1 expression is regulated by hypermethylation of the Sirt1 promoter, which is catalyzed by DNA methyltransferase 3a (DNMT3a). In summary, this study reveals that Dex can trigger ferroptosis by promoting DNMT3a-mediated DNA methylation and downregulating Sirt1 expression. Our findings provide an additional new mechanism for Dex-induced ferroptosis in MC3T3-E1 cells.
Chinese Journal of Tissue Engineering Research•2026•DOI: 10.12307/2026.21475
BACKGROUND: The pathogenesis of steroid-induced osteonecrosis of the femoral head remains unclear; however, it is closely associated with mitochondrial damage in osteoblasts. OBJECTIVE: To explore the impact of dexamethasone on mitochondrial dysfunction in osteoblasts following steroid-induced osteonecrosis of the femoral head and to analyze its regulatory roles in osteoblast apoptosis and autophagy. METHODS: MC3T3-E1 cells were cultured in vitro and divided into control group (no treatment) and dexamethasone group (1 μmol/L dexamethasone treatment for 24 hours). Osteoblast differentiation capacity was assessed by alizarin red staining and qRT-PCR. Mitochondrial morphology was examined using transmission electron microscopy, MitoTracker Red fluorescence staining, and flow cytometry. Mitochondrial membrane potential and energy metabolism were evaluated by JC-1 fluorescence staining and ATP content detection. Mitochondrial superoxide levels were measured using MitoSOX fluorescence probe and flow cytometry. Intracellular total reactive oxygen species and glutathione content were also measured to assess oxidative stress status. Additionally, Western blot and qRT-PCR were used to detect the expression of apoptosis-related proteins (Bax, Bcl-2) and autophagy markers (LC3B, p62), flow cytometry was used to analyze apoptosis rate, and autophagy flux was observed via mRFP-GFP-LC3 adenovirus transfection combined with confocal microscopy. RESULTS AND CONCLUSION: Compared with the control group, the dexamethasone group showed significantly reduced osteogenic differentiation capacity of MC3T3-E1 cells, abnormal mitochondrial structure (swelling, cristae disruption), decreased mitochondrial membrane potential, reduced ATP synthesis, increased mitochondrial superoxide and total reactive oxygen species levels, and increased glutathione consumption (P < 0.05). The dexamethasone group showed significantly upregulated pro-apoptotic protein Bax (P < 0.01), significantly downregulated anti-apoptotic protein Bcl-2 (P < 0.01), increased LC3B-II/I ratio (P < 0.01), and decreased p62 levels (P < 0.01); dexamethasone treatment significantly increased the apoptosis rate (P < 0.01). mRFP-GFP-LC3 adenovirus tracing revealed increased formation of autophagosomes and autolysosomes. These results indicate that dexamethasone induces mitochondrial dysfunction and oxidative stress, synergistically regulating apoptosis and autophagy in MC3T3-E1 cells, thereby impairing bone formation and repair function. This mechanism may be a key pathological basis for the pathogenesis of steroid-induced osteonecrosis of the femoral head.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025096
Steroid-induced osteonecrosis of the femoral head (SONFH) is a progressive bone disorder driven by prolonged glucocorticoid exposure, with limited therapeutic options. Ferroptosis, a regulated form of necrosis, has emerged as a potential contributor to SONFH pathogenesis, yet its mechanistic link to osteoblast dysfunction remains poorly defined. This study investigates the relationship between dexamethasone (Dex)-induced ferroptosis and silent information regulator 1 (Sirt1) in MC3T3-E1 osteoblastic cells. Dex treatment downregulated Sirt1 expression and increased ferroptosis markers, while Sirt1 overexpression elevated the ferroptosis-related proteins SLC7A11 and GPX4 following Dex exposure. Mechanistically, Dex promoted hypermethylation of the Sirt1 promoter via DNA methyltransferase 3a (DNMT3a), leading to Sirt1 suppression. These findings establish a novel epigenetic axis—DNMT3a-mediated Sirt1 promoter hypermethylation—that drives Dex-induced ferroptosis in osteoblasts. The study was conducted exclusively in vitro, and the pathophysiological relevance requires validation in animal models. Nevertheless, this work provides a foundation for understanding the epigenetic regulation of osteoblast ferroptosis and suggests potential therapeutic avenues for preventing SONFH.