Podocytes are sensitive to fluid shear stress in vitro
Podocytes are sensitive to fluid shear stress in vitro
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DOI：
10.1152/ajprenal.00196.2005
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发表时间：
2006-10-01
影响因子：
4.2
通讯作者：
Endlich, Karlhans
中科院分区：
文献类型：
--
作者：
Friedrich, Colin;Endlich, Nicole;Endlich, Karlhans
足细胞暴露在肾小球毛细血管压力和滤过所产生的机械力中。已有研究表明，拉伸在体外影响足细胞生物学，并在体内肾小球硬化的发生发展中发挥重要作用。然而，足细胞是否对流体剪应力敏感是完全未知的。因此，在本研究中，我们将最近产生的条件永生化小鼠足细胞系的细胞暴露在流室中定义的流体剪应力下，模拟肾小球超滤液在Bowman间隙中足细胞表面的流动。当切应力大于0.25dyne/cm(2)时，足细胞大量丢失，但近端肾小管上皮细胞(LLCP1细胞)在0.015-0.25dyne/cm(2)切应力作用下，足细胞片状脂膜形成增加，肌动蛋白核蛋白Cortactin重新分布到细胞边缘。剪切应力进一步减少了局部粘连中的应力纤维和纽蛋白的存在。在低剪应力下，细胞-细胞接触处的线状闭锁带闭塞-1分布不受影响。在0.25dyne/cm(2)时，单层被打破，剩余的细胞-细胞接触被F-肌动蛋白和α-肌动蛋白加强。由于切应力引起的细胞骨架改变提示酪氨酸激酶(TKs)的参与，我们测试了几种TK抑制剂，它们在静态条件下对足细胞数都没有影响。然而，在0.25dyne/cm(2)时，TK抑制剂Genistein和AG 82与显著的足细胞丢失有关。我们的数据表明足细胞对流体剪应力高度敏感。剪切力诱导肌动蛋白细胞骨架的重组，并激活特定的酪氨酸激酶，这是承受流体剪切力所必需的。
Podocytes are exposed to mechanical forces arising from glomerular capillary pressure and filtration. It has been shown that stretch affects podocyte biology in vitro and plays a significant role in the development of glomerulosclerosis in vivo. However, whether podocytes are sensitive to fluid shear stress is completely unknown. In the present study, we therefore exposed cells of a recently generated conditionally immortalized mouse podocyte cell line to defined fluid shear stress in a flow chamber, mimicking flow of the glomerular ultrafiltrate over the surface of podocytes in Bowman's space. Shear stress above 0.25 dyne/cm(2) resulted in dramatic loss of podocytes but not of proximal tubular epithelial cells (LLC-PK1 cells) after 20 h. At 0.015-0.25 dyne/cm(2), lamellipodia formation in podocytes was enhanced and the actin nucleation protein cortactin was redistributed to the cell margins. Shear stress further diminished stress fibers and the presence of vinculin in focal adhesions. Linear zonula occludens-1 distribution at cell-cell contacts remained unaffected at low shear stress. At 0.25 dyne/cm(2), the monolayer was broken up and remaining cell-cell contacts were reinforced by F-actin and alpha-actinin. Because the cytoskeletal changes induced by shear stress suggested the involvement of tyrosine kinases (TKs), we tested several TK inhibitors that were all without effect on podocyte number under static conditions. At 0.25 dyne/cm(2), however, the TK inhibitors genistein and AG 82 were associated with marked podocyte loss. Our data demonstrate that podocytes are highly sensitive to fluid shear stress. Shear stress induces a reorganization of the actin cytoskeleton and activates specific tyrosine kinases that are required to withstand fluid shear stress.