ACAN and intervertebral disk degenerative disorder: Currently, the research on mechanisms of action of IDD mainly focuses on tissue fibrosis (Wang X. et al., 2019), inflammatory responses (Chang et al., 2021), the anabolism of extracellular matrix (Wang R. et al., 2020), insufficient transport of metabolites (Ge et al., 2020), enhanced aggrecan and collagen degradation (Du et al., 2021), and the structural and functional abnormalities in mitochondria (Song et al., 2021).