TLR2 and IRF8 are the biomarkers associated with hypoxia in steroid-induced osteonecrosis of the femoral head via bioinformatics analysis and experimental validation

Accumulating evidence has shown that hypoxia harbors a dominant role in pathophysiological mechanisms of steroid-induced osteonecrosis of the femoral head (SONFH), but the significance of hypoxia in SONFH is still rarely explored. By integrating SONFH gene expression matrix GSE123568 and hypoxia gene sets, the hypoxia-related differentially expressed genes (DEGs) were screened out. Functional and gene set enrichment analyses were conducted to reveal the underlying mechanisms of hypoxia-related DEGs. Protein and protein interaction (PPI) model was preformed to identify hub genes. The receiver operating characteristic (ROC) curve of hub genes was analyzed. Furthermore, the expression levels of hub genes were validated in clinical serum samples of SONFH patients and healthy volunteers. A total of 185 hypoxia-related DEGs were obtained between SONFH and non-SONFH controls. Functional and gene set enrichment analyses showed that those hypoxia-related DEGs are enriched in cytokine-cytokine receptor interaction, lipid and atherosclerosis, osteoclast differentiation, and HIF-1 signaling pathway. Depending on PPI network, we screened out five hub genes, including TLR2, IRF8, CXCL8, CD86, and MAPK1 which may serve as biomarkers for SONFH. The ROC results showed that all five hub genes had high diagnostic accuracy for patients with SONFH. The results of both qRT-PCR and enzyme-linked immunosorbent assay (ELISA) showed that TLR2 and IRF8 were markedly increased in blood samples of SONFH patients. TLR2 and IRF8 might act as promising biomarkers for SONFH patients. The findings would offer new insights for identifying potential biomarkers and drug targets for SONFH.