MMP9 and intervertebral disk degenerative disorder: Inhibition of MMP-9 expression—via siRNA-mediated gene silencing, small molecule inhibitors (e.g., SB-3CT), or modulation through upstream signaling pathways such as miR-21/PTEN/Akt/mTOR—has been shown to reduce ECM breakdown and inflammatory responses in vitro NP cell models and in vivo rat models of IDD (Li et al., 2017; Gong et al., 2023; Shin et al., 2016).