ATG5 regulates autophagy-apoptosis-ER stress dysregulation in steroid-induced osteonecrosis of the femoral head (SONFH) pathogenesis

The aim is to investigate how ATG5 regulates autophagy, endoplasmic reticulum stress (ERS), and apoptosis in steroid-induced osteonecrosis of the femoral head (SONFH), and to evaluate ATG5-targeted inhibition as a SONFH intervention. Differentially expressed genes in SONFH were screened using GEO dataset GSE74089. Autophagy/apoptosis/ERS pathway activities were analyzed via GSEA, GO/KEGG enrichment, and GSVA. Rat bone marrow mesenchymal stem cells (BMSCs) were isolated for osteoblast modeling. Groups included: control (A), steroid-treated (B, methylprednisolone), and intervention (C, steroid + ATG5-siRNA). Autophagosome formation, apoptosis rate, and ATG5/PERK/LC3 expression were assessed by electron microscopy, flow cytometry, qPCR, and western blotting. Sixty SD rats were divided into three groups (as above). The SONFH model was established via intramuscular methylprednisolone injection, with intervention group receiving ATG5-siRNA. Bone pathology, cell death, and pathway regulation were evaluated using HE/TUNEL staining, electron microscopy, and molecular detection. Transcriptome analysis revealed synergistic activation of autophagy (ATG5/BECN1), apoptosis (CASP3/9/12), and ERS (PERK) pathways in SONFH, with ATG5 strongly correlating with all three. Steroids upregulated ATG5 to overactivate autophagy, triggering PERK-mediated ERS and ERS-specific apoptosis. ATG5-siRNA intervention inhibited autophagosome formation, reduced apoptosis, downregulated PERK, and alleviated trabecular fractures and empty lacunae. ATG5 deficiency blocked PERK signaling, suppressing both autophagic death and ERS-dependent apoptosis.ATG5 drives autophagy overactivation and ERS-apoptosis cascades via PERK pathway activation, constituting a core SONFH mechanism. Targeted ATG5 silencing effectively blocks this pathology, offering novel preventive/therapeutic strategies.