BIOPHYSICAL INHIBITION OF OSTEOCLAST FORMATION

生理负荷产生大量的物理力， 力阻止骨吸收的机制还不清楚。 在 在过去的资助期间，我们证明了一个外源电场 与骨骼负荷期间产生的类似， 抑制破骨细胞生成。 我们已经证明，另外两个 载荷产生的力也抑制破骨细胞的募集。 连续施加1.37（或2 atm）的压力抑制 破骨细胞形成33 ± 5%。 产生的机械应变 拉伸细胞抑制破骨细胞形成60 ± 5%。 这 这项工作提出了一个范例，即力通过以下方式限制骨吸收： 破骨细胞数量减少。 我们已经开始开发关于细胞的信息 和破骨细胞募集过程中的分子靶点。 压力和拉伸都是有效的，如果剂量在 破骨细胞前体细胞增殖和分化的培养期 分化发生。 巨噬细胞集落刺激因子 （MCSF）是这些早期文化事件的关键。 使用RT- PCR我们已经表明，压力和拉伸降低水平， 编码MCSF的膜结合亚型的mRNA， 由成骨细胞表达。 由于成骨细胞和 MCSF是破骨细胞生成所必需的， 力诱导的成骨细胞膜表达减少 结合MCSF可能是破骨细胞减少的原因 阵 因此，我们认为，生物物理刺激抑制破骨细胞 通过调节成骨细胞旁分泌信号的募集。 我们假设，在限制骨吸收，生物物理， 力直接针对成骨细胞。 成骨细胞对 通过信号传导， 破骨细胞前体或减少这些前体进入 破骨细胞谱系。 这些效应可以通过 成骨细胞MCSF表达降低。 阐明本 在这个系统中，我们将1）量化 对压力和拉伸的抑制剂量反应，并指定一个 最小限度的“力敏感性”窗口，以限制可能的目标， 及时发力。 2)我们将定义哪个单元格是关键直接 有效力的目标-破骨细胞前体和/或 成骨细胞前体3)然后我们将澄清远端是否 武力的目标是扩散或早期分化， 破骨细胞前体 最后，我们希望至少能区分出 一种分子机制参与了这一过程， 坚持力诱导膜减少的观点 结合MCSF导致破骨细胞形成的抑制。

Physiologic loading generates a host of physical forces which force prevents bone resorption are not well understood. In the past funding period we proved that an exogenous electrical field similar to that generated during skeletal loading is capable of inhibiting osteoclastogenesis. We have shown that two other load-generated forces inhigit osteoclast recruitment as well. Continuous application of 1.37 (or 2 atm) of pressure inhibits osteoclast formation by 33+5%. Mechanical strain created by stretching cells inhibits osteoclast formation by 60+5%. This work suggested a paradigm - that force limits bone resorptio by decreasing osteoclast numbers. We have begun to develop information regarding the cellular and molecular targets of force during osteoclast recruitment. Both pressure and stretch are effective if dosed during the period of culture when osteoclast precusor proliferation and erly differentiation occur. Macrophage colony stimulating factor (MCSF) is crtical for these early events in culture. Using RT- PCR we have shown that presure and stretch decrease the level of mRNA encoding the membrane-bound isoform of MCSF, which is expressed by osteoblasts. Since both osteoblasts and MCSF are necessary for osteoclastogenesis, it is possible that a force-induced decrease in osteoblast expression of membrane bound MCSF could be responsible for decreased osteoclast formation. We therefore propose that biiphysical stimuli inhibit osteoclast recruitment through modulation of osteoblast paracrine signals. We postulate that in limiting bone resorption, biopphysical forces directly target the osteoblast. The osteoblast responds to force by signalling for either decreased proliferation of osteoclast precursors or decreased entry of these precursors into the osteoclast lineage. These effects may be transduced by decreases in osteoblast MCSF expression. To elucidate the mechanisms of force in this system we will 1) quantify an inhibitory dose-response to pressure and stretch and assign a minimal window of "force sensitivity" to limit possible targets of force in time. 2) We will define which cell is the critical direct target of effective forces - the osteoclast precursors and/or osteoblast precursor. 3) We will then clarify whether the distal target of force is the proliferation or eraly differentiation of osteoclast precursors. Finally, we hope to 4) distinguish at least one molecular mechanism involved in this process, and will pursue the idea that force induced decrements in membrane bound MCSF lead to an inhibition of osteoclast formation.