SOX9 and intervertebral disk degenerative disorder: The results unveiled that estrogen receptor α (ESR1) ranked the highest and was a hub gene, suggesting that ESR1 could regulate a series of IDD-related genes, encompassing protective factors, such as SIRT1, Sox9, HIF-1α, and IGF1R, as well as catabolic factors, such as IL-6, MMP2/9, and CASP3 (Figures 1A,B).