Catabolic gene expression is upregulated by tumor necrosis factor-alpha, interleukin-1beta, and limited nutrition. Expression of matrix metalloproteinase 3 (MMP-3) mRNA in nucleus pulposus (NP) (A) and annulus fibrosus (AF) (B) tissues. Expression is significantly induced in both tissues after the treatment for 3 and 10 days. Results are shown as the mean ± standard error for three independent experiments (n = 6 discs/group per experiment). *P <0.05. (C) Western blot analysis of MMP-3 in NP and AF tissue lysates after 3 days in culture confirms the expression of MMP-3. (D) Representative photomicrographs of the immunohistochemical reactivity for MMP-3 in tissue sections from treated discs for 3 days (c,d). Sections were also stained with Alcian blue and hematoxylin and eosin (HE) for visualization of morphological details (a,b). Owing to extremely low signal intensity, data for untreated tissue sections are not shown. Original magnification: 20×. (E) The expression of MMP-3 tends to increase in the experimental group. Ctr., control group; Exp, experimental group.