IGF1 and intervertebral disk degenerative disorder: Studies have revealed that among the top signaling pathways potentially regulated by miRNAs, the TGF-β, platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and epidermal growth factor (EGF) pathways have been implicated in the pathogenesis of IDD (Hegewald et al., 2014; Koerner et al., 2014; Li et al., 2008).