Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada.
Am J Physiol Heart Circ Physiol. 2011 Aug;301(2):H315-23. doi: 10.1152/ajpheart.00355.2010. Epub 2011 May 13.
Vascular smooth muscle cell (SMC) migration is characterized by extension of the lamellipodia at the leading edge, lamellipodial attachment to substrate, and release of the rear (uropod) of the cell, all of which enable forward movement. However, little is known regarding the role of intracellular cytosolic Ca(2+) concentration (Ca(2+)) in coordinating these distinct activities of migrating SMCs. The objective of our study was to determine whether regional changes of Ca(2+) orchestrate the migratory cycle in human vascular SMCs. We carried out Ca(2+) imaging using digital fluorescence microscopy of fura-2 loaded human smooth muscle cells. We found that motile SMCs exhibited Ca(2+) waves that characteristically swept from the rear of polarized cells toward the leading edge. Ca(2+) waves were less evident in nonpolarized, stationary cells, although acute stimulation of these SMCs with the agonists platelet-derived growth factor-BB or histamine could elicit transient rise of Ca(2+). To investigate a role for Ca(2+) waves in the migratory cycle, we loaded cells with the Ca(2+) chelator BAPTA, which abolished Ca(2+) waves and significantly reduced retraction, supporting a causal role for Ca(2+) in initiation of retraction. However, lamellipod motility was still evident in BAPTA-loaded cells. The incidence of Ca(2+) oscillations was reduced when Ca(2+) release from intracellular stores was disrupted with the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin or by treatment with the inositol 1,4,5-trisphosphate receptor blocker 2-aminoethoxy-diphenyl borate or xestospongin C, implicating Ca(2+) stores in generation of waves. We conclude that Ca(2+) waves are essential for migration of human vascular SMCs and can encode cell polarity.
血管平滑肌细胞（SMC）的迁移特征为前沿的片状伪足延伸、片状伪足与基质附着以及细胞后尾（足突）的释放，所有这些都能促进细胞向前运动。然而，关于细胞内细胞质钙离子浓度（[Ca2+]i）如何协调迁移SMC 的这些不同活动知之甚少。我们的研究目的是确定细胞内钙离子浓度的区域变化是否协调人血管平滑肌细胞的迁移周期。我们通过对负载有 fura-2 的人平滑肌细胞进行数字荧光显微镜钙离子成像来进行钙离子成像。我们发现，运动的 SMC 表现出特征性地从极化细胞的后尾向前沿扫过的钙离子波。在非极化的静止细胞中，钙离子波不太明显，尽管急性刺激这些 SMC 用血小板衍生生长因子-BB 或组胺作为激动剂可以引起 [Ca2+]i 的短暂升高。为了研究钙离子波在迁移周期中的作用，我们用钙离子螯合剂 BAPTA 加载细胞，BAPTA 可以消除钙离子波并显著减少回缩，这支持钙离子在回缩起始中的因果作用。然而，在 BAPTA 加载的细胞中仍然存在片状伪足运动。当通过肌浆网钙离子-ATP 酶抑制剂 thapsigargin 或用肌醇 1,4,5-三磷酸受体阻滞剂 2-氨基乙氧基二苯硼酸盐或 xestospongin C 破坏细胞内储存的钙离子释放时，钙离子振荡的发生率降低，这表明钙离子储存库参与了波的产生。我们得出结论，钙离子波是人类血管平滑肌细胞迁移所必需的，并且可以编码细胞极性。
