CTSK and intervertebral disk degenerative disorder: IDD mice with TNFR1 and TNFR2 deficiencies exhibited diminished disc area and enhanced endplate ossification, notably, TNFR2-deficient IDD mice showed more severe morphological disruption of intervertebral discs, with elevated MMP13, Cathepsin K and Bax expression, decreased Bcl-2 levels, and increased OC (174).