Effects of bone morphogenetic protein-2 and transforming growth factor-β1 on gene expression of decorin and biglycan by cultured osteoblastic cells.

研究了骨形态发生蛋白-2(BMP-2)和转化生长因子β(β)对克隆大鼠成骨细胞系ROS-C26(C26)小蛋白多糖、核心蛋白聚糖和双聚糖表达的影响。ROS-C26(C26)细胞是一种潜在的成骨前体细胞，经重组BMP-2诱导分化为成熟成骨细胞。在有或无rhBMP-2的条件下培养C26细胞3、6和9天后，与不加rhBMP-2的对照细胞相比，经rhBMP-2处理的细胞碱性磷酸酶活性增加与其向更成熟的成骨细胞分化成正比，而核心蛋白聚糖的mRNA表达减少。这些结果在治疗后6天明显。而重组人骨形态发生蛋白-2对Biglycan基因的表达无明显影响。去除培养液中的重组人骨形态发生蛋白-2后，以不同浓度的转化生长因子-β-1(0、0.1、1.0、5.0、10 ng/ml)继续培养24 h。转化生长因子-β-1呈剂量依赖性地降低细胞核心蛋白聚糖基因的表达，但不影响其双聚糖基因的表达。此外，去除培养液中的重组人骨形态发生蛋白-2或加入转化生长因子-β-1均可显著降低重组人骨形态发生蛋白-2诱导的细胞的碱性磷酸酶活性。结果表明，在成骨细胞分化过程中，伴随着碱性磷酸酶活性的升高和核心蛋白聚糖基因表达的降低，但Biglycan基因的表达持续存在。重组人骨形态发生蛋白-2和转化生长因子-β1在不同分化阶段均抑制成骨细胞核心蛋白聚糖基因的表达，但对Biglycan基因表达和碱性磷酸酶的影响不同。

The influence of bone morphogenetic protein-2 (BMP-2) and transforming growth factor β (TGF-β) on the expression of small proteoglycans, decorin and biglycan was investigated in a clonal rat osteoblastic cell line, ROS-C26 (C26) cells, which is a potential osteoblast precursor cell line and capable of differentiating into mature osteoblasts after treatment with recombinant BMP-2 (rhBMP-2). Following the culture of C26 cells for 3, 6, and 9 days in the presence or absence of rhBMP-2, alkaline phosphatase activity increased in the rhBMP-2 treated cells in direct proportion to their differentiation into more mature osteoblastic cells, whereas decorin mRNA decreased in the cells, when compared to control cells without rhBMP-2 treatment. These results were evident 6 days after treatment. However, rhBMP-2 treatment had no effect on biglycan mRNA expression in the cells. Subsequently, after removal of rhBMP-2 from the culture media, the cells were further cultured for 24 h with graded concentrations of TGF-β1 (0,0.1,1.0, 5.0, and 10 ng/ml). TGF-β1 decreased decorin mRNA expression in the cells dose dependently, but did not effect their biglycan mRNA expression. Furthermore, either removal of rhBMP-2 from the culture media or addition of TGF-β1 significantly decreased alkaline phosphatase activity of rhBMP-2-induced cells. There results indicate that osteoblastic differentiation is accompanied by increased alkaline phosphatase activity and decreased expression of decorin mRNA, but continuous expression of biglycan mRNA. Both rhBMP-2 and TGF-β1 inhibit decorin mRNA expression in osteoblasts at varying stages of differentiation, but their effects on biglycan mRNA expression and alkaline phosphatase are different.