Isolation and identification of bone morphogentic protein and its potentiator from bovine serum

我们从胎牛血清中纯化了一种蛋白质因子，它可以增强成骨细胞的分化。虽然该因子本身没有表现出这样的刺激活性，但它在少量骨形态发生蛋白（BMP）存在下刺激成骨细胞分化，表明该因子是BMP增效剂。该因子来源于血小板。该因子表达缺陷的小鼠表现出延迟性骨折听力。与此相反，骨折听力加速在转基因小鼠的这个因素。此外，我们还在胎牛血清中发现了一种BMP样因子，并通过一系列的柱层析分离了这种活性。该血清BMP的生物学活性被BMP受体的显性负性形式和BMP拮抗剂Noggin阻断。LC-MS/MS分析表明，高度纯化的级分含有成熟BMP的保守序列。这些结果表明血清因子在骨形成中起重要作用。此外，我们发现硫酸多糖如肝素和硫酸乙酰肝素也增强BMP的生物活性。当BMP与肝素一起植入小鼠体内时，BMP在体内的异位骨诱导活性也被肝素增强。综上所述，这表明骨形成蛋白及其增强剂在血清中正调节脊椎动物骨形成。

We purified a protein factor, which potentiates osteoblast differentiation, from fetal bovine serum. Although this factor itself did not show such stimulatory activity, it stimulated the osteoblast differentiation in the presence of small amount of bone morphogenetic proteins (BMPs), suggesting that this factor is a BMP potentiator. This factor is derived from platelets. Deficient mice in this factor expression showed delayed bone fracture hearing. In contrast, the fracture hearing was accelerated in transgenic mice of this factor. Moreover, we found a BMP-like factor in fetal bovine serum and isolated this activity using a series of column chromatography. The biological activity of this serum BMP was blocked by dominant negative form of BMP receptor and Noggin, a BMP antagonist. LC-MS/MS analysis indicated that the highly purified fraction contained a conserved sequence of a mature BMP. These results indicate that serum factors play a important role in bone formation. Moreover, we found that sulfated polysaccharides such as heparin and heparan sulfate also potentiated the biological activities of BMPs. When BMP was implanted together with heparin in mice, the ectopic bone-inducing activity of BMP in vivo was also potentiated by heparin. Taken together, it was suggested that BMPs and their potentiators in serum positively regulate bone formation in vertebrates.