PATHOPHYSIOLOGY OF OSTEOPOROSIS IN AGING WOMEN

我们的中心假设是，雌激素（E）缺乏对骨有直接和间接的影响，这两种影响通过不同的机制引起骨丢失，大多数老年妇女的骨丢失可以用这两种影响共同作用来解释。绝经后妇女经历两个不同的骨丢失阶段-一个快速的、短暂的阶段，开始于绝经期（由于E对骨细胞功能的直接抑制作用的丧失），和一个缓慢的、随后的阶段，无限期地持续（主要由于E对外周钙代谢的作用的丧失，导致继发性甲状旁腺功能亢进（HPT），以及间接地， 骨丢失）。尽管近年来对老年妇女骨丢失的病理生理学已经了解了很多，但最重要的剩余研究需要是确定这些直接（仅E缺乏）和间接（E缺乏加上甲状旁腺激素[PTH]过量）骨骼效应产生骨丢失的机制。虽然已经有大量使用体外系统和实验动物的研究，但在妇女中的数据非常有限。我们将采用新的方法学方法，使我们能够直接在人类中研究这些机制。在目标1中，我们将明确地确定IL-1 β和TNF α是否是通过干预IL-1 β阻断剂阿那白滞素和TNF α阻断剂依那西普而引起的急性E-戒断引起的骨吸收增加的重要介质。在目标2和3中，我们将 应用我们开发的新方法从骨髓中分离成骨细胞和破骨细胞前体细胞，研究它们的分化和功能，并评估它们的假定调节细胞因子和细胞因子受体的mRNA含量。这些方法利用双色流式细胞术/FACS、荧光探针强度和真实的时间RT-PCR。在目标2中，我们将确定E是否通过直接作用抑制破骨细胞谱系细胞的分化，如果是，这是否通过调节c-Fms或RANK表达或其他机制发生。最后，在目标3中，我们将定义PTH对骨转换的双相作用的分子机制（间歇给药主要增加骨形成，而连续给药主要增加骨吸收）以及E如何改变它们。除了帮助确定绝经后妇女骨丢失两个阶段的病理生理学，这些数据还将有助于解释新批准的间歇性PTH（1-34）合成代谢方案治疗绝经后妇女骨丢失的分子机制。 骨质疏松

Our central hypotheses are that estrogen (E) deficiency has both direct and indirect effects on bone, that these two effects cause bone loss by different mechanisms, and that most of the bone loss of aging women can be explained by both effects acting in concert. Postmenopausal women undergo two distinct phases of bone loss - a rapid, transient phase that begins at menopause (due to loss of the direct suppressive effects of E on bone cell function) and a slow, subsequent phase that continues indefinitely (due mainly to loss of E effects on peripheral calcium metabolism leading to secondary hyperparathyroidism (HPT) and, indirectly, to bone loss). Although much has been learned in recent years about the pathophysiology of bone loss in aging women, the most important remaining research need is to define the mechanisms by which these direct (E deficiency only) and indirect (E deficiency plus parathyroid hormone [PTH] excess) skeletal effects produce bone loss. Although there have been extensive studies using in vitro systems and experimental animals, there are very limited data in women. We will apply novel methodological approaches that will allow us to study these mechanism directly in humans. In Aim 1, we will determine unequivocally whether IL-1beta and TNFalpha are essential mediators of the increased bone resorption induced by acute E-withdrawal by intervening with the IL-1beta blocker, anakinra, and the TNFalpha blocker, etanercept. In Aims 2 and 3, we will apply a new method that we have developed to isolate osteoblast and osteoclast precursors from bone marrow, to study their differentiation and function, and to assess their content of mRNA for putative regulatory cytokines and cytokine receptors. These methods utilize 2-color flow cytometry/FACS, intensity of fluorescent probes, and real time RT-PCR. In Aim 2, we will determine if E inhibits differentiation of osteoclast lineage cells through a direct action and, if so, if this occurs by regulating c-Fms or RANK expression or by other mechanisms. Finally, in Aim 3, we will define the molecular mechanisms of the biphasic action of PTH on bone turnover (intermittent administration increases mainly formation whereas continuous increases mainly resorption) and how E modifies them. In addition to helping define the pathophysiology of the two phases of bone loss in postmenopausal women, these data will also help explain molecular mechanisms for the newly approved anabolic regimen of intermittent PTH(1-34) for treating osteoporosis.