Effect of bone morphogenetic protein-2 (BMP-2) on matrix production, other BMPs, and BMP receptors in rat intervertebral disc cells

Objective: An in vitro experiment study using rat disc cells was carried out to determine the effect of bone morphogenetic protein-2 (BMP-2) on extracellular matrix production, other BMPs, and BMP receptors (BMPRs). Methods: Cells from the anulus fibrosus and transition zone were harvested and cultured. When the cells reached 80% confluence, BMP-2 was added to reach a final concentration of 200 ng/mL. Three days later, the culture media were collected for the assay of sulfated glycosaminoglycans (sGAG) and collagen types I and II. The cells were harvested for RNA extraction to determine the genes expressed. All experiments were performed at least three times to ensure repeatability. Results: BMP-2 significantly increased aggrecan and collagen type II mRNA expression 8.30 and 4.61 times, respectively, and decreased versican mRNA expression 0.54 times as compared with control. Collagen type I production and mRNA level were not changed. BMP-2 significantly increased transforming growth factor-beta(1) (TGFbeta(1)) and BMP-7 mRNA expression 2.32 and 2.45 times, respectively, compared with control. There was no significant change in BMP-6 mRNA expression. BMPR type IB and II mRNA expressions were increased and BMPR type 1A mRNA expression was decreased, but none of these differences was significant. Conclusions: The results of this study show that in rat intervertebral disc cells, BMP-2 increases aggrecan and collagen type II mRNA expression and decreases versican gene expression. BMP-2 also upregulates mRNA expression for BMP-7 and TGFbeta but has no significant effect on the BMPRs.