Fig. 5

The effect of osteoprotegerin (OPG) on the mRNA expression of matrix-degrading enzymes and proinflammatory cytokines with or without recombinant human interleukin-1 beta (rhIL-1β) stimulation. The mRNA expression of IL-1β (a, b), matrix metalloprotease (MMP)-3 (c, d), and MMP-13 (e, f) by annulus fibrosus (AF) (a, c, e) and nucleus pulposus (NP) (b, d, f) cells were quantified by real-time polymerase chain reaction. Treatment with OPG in the presence of rhIL-1β (1.0 ng/mL) significantly downregulated the mRNA expression levels of IL-1β by both AF and NP cells, MMP-3 by NP cells and MMP-13 by AF cells. There was a similar trend in the expression levels of MMP-3 by AF cells and that of MMP-13 by NP cells: *p < 0.05, **p < 0.01