CCND1 and intervertebral disk degenerative disorder: Compared with IDD patients showing mild degeneration, caspase-3, Bax, Wnt3a, Wnt5a, Wnt10a, GSK-3β, cyclin-D1, and β-catenin expression was significantly increased with IDD progression, while Bcl-2 expression was significantly decreased in patients with severe IDD.