COL2A1 and Intervertebral disk degeneration: Of note, HIF1Ahigh_NP2 showed high expression of COL2A1 and NR4A1. COL2A1 encodes type II collagen fibers, which increase intervertebral disc stability (Trefilova et al., 2021), while NR4A1 has been reported to participate in the regulatory process of inhibiting intervertebral disc degeneration (Feng et al., 2017).