OSTEOCLASTS--GLUCOCORTICOIDS AND APOPTOSIS

破骨细胞在骨质疏松症的发病机制中起关键作用， 其他代谢性骨疾病。 虽然我们对起源和 近年来，破骨细胞的调节有了很大的改善， 仍然几乎完全不知道破骨细胞的命运。 一部分 对糖皮质激素的细胞机制的研究 诱导骨质疏松症，我们已经获得的证据表明，破骨细胞 表现出凋亡或程序性细胞死亡，这是一种独特的， 一种与坏死有根本区别的故意的细胞死亡 在其性质和生物学意义上。 受此影响， 根据观察，这一修订后的申请集中在假设上， 细胞凋亡在决定破骨细胞寿命中起生理作用 并由此调节骨吸收。 的意义 这一假设在于，它有可能提供一个 理解骨骼重要方面的新概念框架 生物学目前知之甚少，例如， 糖皮质激素和雌激素对骨的作用。 这一建议的具体目标是：1）检验假设， 在糖皮质激素的存在下，破骨细胞表现出凋亡， 体外，阐明细胞凋亡的细胞内机制， 破骨细胞，并探测凋亡的分子标志物， 破骨细胞; 2）检测糖皮质激素对破骨细胞的影响 成骨细胞的存在改变了存活和活性， 确定糖皮质激素对破骨细胞募集的影响; 3） 为了确定哺乳动物和鸟类破骨细胞是否表达 糖皮质激素受体;和4）测试破骨细胞 在体内表现出凋亡。 这些目标将通过一个 技术组合，包括分解破骨细胞 骨吸收测定，破骨细胞的透射电子显微镜， 原位杂交、免疫细胞化学和骨组织形态计量学。

The osteoclast plays a key role in the pathogenesis of osteoporosis and other metabolic bone diseases. While our understanding of the origin and regulation of the osteoclast has improved greatly in recent years, we are still almost completely ignorant of the fate of the osteoclast. As part of an investigation of the cellular mechanisms underlying glucocorticoid- induced osteoporosis, we have obtained evidence that the osteoclast exhibits apoptosis, or programmed cell death, a distinctive and deliberate type of cell death that differs fundamentally from necrosis in both its nature and biological significance. Prompted by this observation, this revised application is focused on the hypothesis that apoptosis plays a physiological role in determining osteoclast life span and, thereby, in the regulation of bone resorption. The significance of this hypothesis lies in the fact that it has the potential to provide a new conceptual framework for understanding important aspects of skeletal biology that are currently poorly understood, for example, the mode of action of glucocorticoids and estrogens on bone. The specific aims of this proposal are: 1) to test the hypothesis that in the presence of glucocorticoids, osteoclasts exhibit apoptosis in vitro, to elucidate the intracellular mechanisms underlying apoptosis in osteoclasts, and to probe for molecular markers of apoptosis in dying osteoclasts; 2) to examine how effects of glucocorticoids on osteoclast survival and activity are modified by the presence of osteoblasts and to determine the effects of glucocorticoids on osteoclast recruitment; 3) to determine whether mammalian and avian osteoclasts express glucocorticoid receptors; and 4) to test the hypothesis that osteoclasts exhibit apoptosis in vivo. These aims will be pursued using a combination of techniques, including the disaggregated osteoclast resorption assay, transmission electron microscopy of the osteoclasts, in situ hybridization, immunocytochemistry, and bone histomorphometry.