Pritchard Scott, Erickson Geoffrey R, Guilak Farshid
Department of Surgery, Duke University Medical Center, 374 Medical Sciences Research Building, Durham, NC 27710, USA.
Biophys J. 2002 Nov;83(5):2502-10. doi: 10.1016/S0006-3495(02)75261-2.
Loading of the spine alters the osmotic environment in the intervertebral disk (IVD) as interstitial water is expressed from the tissue. Cells from the three zones of the IVD, the anulus fibrosus (AF), transition zone (TZ), and nucleus pulposus (NP), respond to osmotic stress with altered biosynthesis through a pathway that may involve calcium (Ca(2+)) as a second messenger. We examined the hypothesis that IVD cells respond to hyperosmotic stress by increasing the concentration of intracellular calcium (Ca(2+)) through a mechanism involving F-actin. In response to hyperosmotic stress, control cells from all zones decreased in volume and cells from the AF and TZ exhibited Ca(2+) transients, while cells from the NP did not. Extracellular Ca(2+) was necessary to initiate Ca(2+) transients. Stabilization of F-actin with phalloidin prevented the Ca(2+) response in AF and TZ cells and decreased the rate of volume change in cells from all zones, coupled with an increase in the elastic moduli and apparent viscosity. Conversely, actin breakdown with cytochalasin D facilitated Ca(2+) signaling while decreasing the elastic moduli and apparent viscosity for NP cells. These results suggest that hyperosmotic stress induces volume change in IVD cells and may initiate Ca(2+) transients through an actin-dependent mechanism.
脊柱负荷会改变椎间盘（IVD）的渗透环境，因为组织中的间质水会被排出。来自IVD三个区域，即纤维环（AF）、过渡区（TZ）和髓核（NP）的细胞，通过一条可能涉及钙（Ca(2+)）作为第二信使的途径，以改变生物合成的方式对渗透应激作出反应。我们检验了这样一个假设，即IVD细胞通过一种涉及F-肌动蛋白的机制，通过增加细胞内钙浓度（Ca(2+)）来应对高渗应激。在高渗应激下，所有区域的对照细胞体积减小，AF和TZ区域的细胞表现出Ca(2+)瞬变，而NP区域的细胞则没有。细胞外Ca(2+)是启动Ca(2+)瞬变所必需的。用鬼笔环肽稳定F-肌动蛋白可防止AF和TZ细胞中的Ca(2+)反应，并降低所有区域细胞的体积变化率，同时弹性模量和表观粘度增加。相反，用细胞松弛素D破坏肌动蛋白则促进了NP细胞的Ca(2+)信号传导，同时降低了弹性模量和表观粘度。这些结果表明，高渗应激会诱导IVD细胞的体积变化，并可能通过一种肌动蛋白依赖性机制启动Ca(2+)瞬变。
