Transforming growth factor-β controls human osteoclastogenesis through the p38 MAPK and regulation of RANK expression
Transforming growth factor-β controls human osteoclastogenesis through the p38 MAPK and regulation of RANK expression
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DOI：
10.1074/jbc.m303905200
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发表时间：
2003-11-07
影响因子：
4.8
通讯作者：
Foged, NT
中科院分区：
文献类型：
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作者：
Karsdal, MA;Hjorth, P;Foged, NT
虽然RANK-L对破骨细胞的形成是必不可少的，但转化生长因子-β(转化生长因子-β)等因子是破骨细胞生成刺激的有力调节器。为了系统地研究转化生长因子-β在人类破骨细胞形成中的作用，通过三种不同的方法从外周血中分离出单核细胞，结果要么是淋巴细胞丰富的，要么是淋巴细胞贫乏的，要么是纯破骨细胞前体细胞(CD14阳性)。在这些破骨细胞前体群体中的每一个中，研究了转化生长因子-β对增殖、TRAP活性和骨吸收的影响。当使用高纯度的CD14破骨细胞前体细胞群时，转化生长因子-β的作用强烈依赖于破骨细胞成熟的阶段。当单核细胞在培养初期(第1~7天)暴露于转化生长因子-β时，TRAP活性和骨吸收增加40%，而细胞数量减少25%。在整个培养过程中(第1-21天)，当存在转化生长因子-β时，细胞数量也有类似的减少，但与之形成直接对比的是，TRAP活性、细胞融合、组织蛋白酶K和基质金属蛋白酶(MMP)-9的表达以及骨吸收几乎完全被取消。此外，我们发现潜伏的转化生长因子-β在与基质金属蛋白酶-9的孵育中被强烈激活，提示这可能是一种高度相关的调节破骨细胞活性的机制。为了进一步研究持续和间断暴露于转化生长因子-β的分化效应的分子机制，我们检测了RANK的表达和p38MAPK的激活。我们发现，转化生长因子-β在单核细胞中强烈诱导p38MAPK，但在成熟的破骨细胞中不能，且持续暴露于单核细胞可下调RANK的表达。目前的结果表明，转化生长因子-β通过刺激p38MAPK促进人单核细胞破骨细胞的生成，而持续暴露于转化生长因子-β通过下调RANK的表达从而减弱RANK-RANK-L信号而抑制破骨细胞的生成。
Although RANK-L is essential for osteoclast formation, factors such as transforming growth factor-beta (TGF-beta) are potent modulators of osteoclastogenic stimuli. To systematically investigate the role of TGF-beta in human osteoclastogenesis, monocytes were isolated from peripheral blood by three distinct approaches, resulting in either a lymphocyte-rich, a lymphocyte-poor, or a pure osteoclast precursor (CD14-positive) cell population. In each of these osteoclast precursor populations, the effect of TGF-beta on proliferation, TRAP activity, and bone resorption was investigated with respect to time and length of exposure. When using the highly pure CD14 osteoclast precursor cell population, the effect of TGF-beta was strongly dependent on the stage of osteoclast maturation. When monocytes were exposed to TGF-beta during the initial culture period ( days 1 - 7), TRAP activity and bone resorption were increased by 40%, whereas the cell number was reduced by 25%. A similar decrease in cell number was observed when TGF-beta was present during the entire culture period ( days 1 - 21), but in direct contrast, TRAP activity, cell fusion, cathepsin K, and matrix metalloproteinase (MMP)-9 expression as well as bone resorption were almost completely abrogated. Moreover, we found that latent TGF-beta was strongly activated by incubation with MMP-9 and suggest this to be a highly relevant mechanism for regulating osteoclast activity. To further investigate the molecular mechanism responsible for the divergent effects of continuous versus discontinuous exposure to TGF-beta, we examined RANK expression and p38 MAPK activation. We found the TGF-beta strongly induced p38 MAPK in monocytes, but not in mature osteoclasts, and that continuous exposure of TGF-beta to monocytes down-regulated RANK expression. The current results suggest that TGF-beta promotes human osteoclastogenesis in monocytes through stimulation of the p38 MAPK, whereas continuous exposure to TGF-beta abrogates osteoclastogenesis through down-regulation of RANK expression and therefore attenuation of RANK-RANK-L signaling.