Merrihew Charis, Soeder Stephan, Rueger David C, Kuettner Klaus E, Chubinskaya Susan
J Bone Joint Surg Am. 2003;85-A Suppl 3:67-74. doi: 10.2106/00004623-200300003-00012.
Osteogenic protein-1 (OP-1, BMP-7) induces bone formation and cartilage growth. Since OP-1 is an anabolic factor expressed by human articular chondrocytes, we examined the response of endogenous OP-1 to interleukin-1beta (IL-1beta) in human articular cartilage.
Normal adult human articular cartilage explants were cultured for twenty-five days in the presence of medium only or were treated with a low dose (0.1 ng/mL) or high dose (1.0 ng/mL) of IL-1beta for forty-eight or ninety-six hours. Alternately, cartilage explants were cultured forty-eight hours with IL-1beta, followed by forty-eight hours in standard medium (recovery). Tissue was analyzed for OP-1 message (by means of the reverse transcriptase-polymerase chain reaction), protein (by means of enzyme-linked immunosorbent assay and Western blot analysis) and proteoglycan content. Medium was analyzed for released proteoglycans and OP-1.
In the presence of medium, OP-1 maintained its steady state of mRNA and protein expression for as long as twenty-five days in culture. A low dose of IL-1beta led to some upregulation in message and a twofold (p < 0.02) increase in OP-1 protein characterized by enhanced processing and activation of OP-1. Removal of IL-1beta (recovery experiments) did not reverse its effect on OP-1 synthesis. A high dose of IL-1beta caused stronger upregulation of message and a twofold decrease in OP-1 protein content (p < 0.007) in the cartilage matrix. However, this decrease in the matrix was primarily due to a release of active OP-1 into the medium. After removal of the 1.0-ng/mL IL-1beta, the levels of OP-1 protein did not recover.
The results of the present study indicate that human adult chondrocytes have an ability to respond anabolically to initial or early catabolic events through an upregulation of endogenous OP-1.
成骨蛋白-1（OP-1，骨形态发生蛋白-7）可诱导骨形成和软骨生长。由于OP-1是人类关节软骨细胞表达的一种合成代谢因子，我们研究了人类关节软骨中内源性OP-1对白细胞介素-1β（IL-1β）的反应。
将正常成人人类关节软骨外植体在仅含培养基的条件下培养25天，或用低剂量（0.1 ng/mL）或高剂量（1.0 ng/mL）的IL-1β处理48或96小时。或者，将软骨外植体与IL-1β一起培养48小时，然后在标准培养基中培养48小时（恢复）。分析组织中的OP-1信息（通过逆转录聚合酶链反应）、蛋白质（通过酶联免疫吸附测定和蛋白质印迹分析）和蛋白聚糖含量。分析培养基中释放的蛋白聚糖和OP-1。
在仅含培养基的条件下，OP-1在培养长达25天的时间内维持其mRNA和蛋白质表达的稳定状态。低剂量的IL-1β导致信息略有上调，OP-1蛋白增加两倍（p < 0.02），其特征是OP-1的加工和激活增强。去除IL-1β（恢复实验）并未逆转其对OP-1合成的影响。高剂量的IL-1β导致信息更强的上调，软骨基质中OP-1蛋白含量降低两倍（p < 0.007）。然而，基质中的这种降低主要是由于活性OP-1释放到培养基中。去除1.0 ng/mL的IL-1β后，OP-1蛋白水平未恢复。
本研究结果表明，人类成年软骨细胞有能力通过上调内源性OP-1对初始或早期分解代谢事件作出合成代谢反应。
