CHARACTERIZATION OF THE BONE FORMING FACTORS IN SERUM

骨形态发生蛋白（BMPs）是骨形成的重要调控因子，可诱导间充质细胞成骨细胞分化。BMP-2在细胞内1小时内诱导Idlan抑制剂的转录，促进肌生成。人类Idl基因-985 bp和-957 bp之间富含gc的区域被鉴定为bmp响应元件。BMP-2在BRE上诱导了一种独特的dna -蛋白复合物。BMP-2诱导的复合体含有Smadl和Smad4，可能是两者的复合体。BMP的活性是由靶细胞内部和外部的许多分子调控的。我们检测了肝素对bmp诱导的C2C12成肌细胞成骨细胞分化的影响。肝素剂量依赖性地增强100 ng/ml BMP-2诱导的ALP活性。然而，化学脱硫肝素衍生物失去了这种刺激能力。肝素没有增加bmp受体复合物的数量。我们使用报告结构监测bmp应答细胞，其中不稳定的增强绿色荧光蛋白在Idl启动子中bmp应答元件的控制下驱动。肝素处理增加了30 h时表达egfp的细胞数量，保护bmp不积聚到细胞层可能在肝素的刺激活性中起重要作用。这些结果表明，多糖，如肝素和硫酸肝素，参与骨形成的系统和/或局部调节。

Bone morphogenetic proteins (BMPs), which can induce osteoblast differentiation in mesenchymal cells, are important regulators for bone formation. BMP-2 induces transcription of Idlan inhibitor for myogenesis, within 1 h in the cells. A GC-rich region between -985 bp and -957 bp of the human Idl gene was identified as a BMP-responsive element. A unique DNA-protein complex was induced in response to BMP-2 on the BRE. The complex induced by BMP-2 contained Smadl and Smad4, possibly as a complex of both Smads. BMP activity is regulated by a number of molecules at the outside and the inside of the target cells. We examined the effects of heparin on the BMP-induced osteoblast differentiation in C2C12 myoblasts. Treating with heparin dose- dependently enhanced the ALP activity induced by 100 ng/ml of BMP-2. However, chemically desulfated heparin-derivatives have lost this stimulatory capacity. The amount of BMP-receptor complex was not increased by heparin. We monitored the BMP-responding cells using a reporter construct in which the destabilized enhanced green fluorescent protein was driven under the control of the BMP-responsive element in the Idl promoter. Heparin-treatment increased a number of the EGFP-expressing cells at 30 h.Protection of BMPs against accumulation into the cell layer may play an important role in the stimulatory activity of heparin. These results suggest that polysaccharides, such as heparin and heparan sulfate, are involved in systemic and/or local regulation of bone formation.