ACAN and intervertebral disk degenerative disorder: Complementarily, Ge et al. [36] reported that melatonin treatment produced the upregulation of collagen II and aggrecan while downregulating collagen X. In addition, this compound was noted to significantly enhance the activity of the ERK signaling pathway, affecting the biological properties of IDD, both in vivo (i.e., a rabbit model of IDD) and in vitro (i.e., human NP cells).