ACAN and intervertebral disk degenerative disorder: Importantly, polymorphisms in ECM genes including ACAN, COL1, COL 2, COL9, COL11, FN, HAPLN1, THBS, CILP, ASPN; and ECM related genes: GDF5, MMP1, MMP2, MMP3, and TIMP have been correlated with human disc degeneration [12,13].