Labelle D, Jumarie C, Moreau R
Laboratoire du métabolisme osseux, Centre BioMed, Université du Québec à Montréal, Québec, Canada.
Cell Prolif. 2007 Dec;40(6):866-84. doi: 10.1111/j.1365-2184.2007.00477.x.
Adult bone tissue is continuously being remodelled and bone mass is maintained by a balance between osteoclastic bone resorption and osteoblastic bone formation. Alteration of osteoblastic cell proliferation may account in part for lack of balance between these two processes in bone loss of osteoporosis. There is calcium (Ca2+) control in numerous cellular functions; however, involvement of capacitative Ca2+ entry (CCE) in proliferation of bone cells is less well investigated.
The study described here was aimed to investigate roles of CCE in the proliferation of osteoblast-like MG-63 cells.
Pharmacological characterizations of CCE were undertaken in parallel, with evaluation of the expression of transient receptor potential canonical (TRPC) channels and of cell proliferation.
Intracellular Ca2+ store depletion by thapsigargin induced CCE in MG-63 cells; this was characterized by a rapid transient increase of intracellular Ca2+ followed by significant CCE, induced by conditions that stimulated cell proliferation, namely serum and platelet-derived growth factor. Inhibitors of store-operated Ca2+ channels (2-APB and SKF-96365) prevented CCE, while voltage-dependent Ca2+ channel blockers had no effect. Expression of various TRPC channels was shown in the cells, some having been shown to be responsible for CCE. Voltage-dependent Ca2+ channel blockers had no effect on osteoblast proliferation while thapsigargin, 2-APB and SKF-96395, inhibited it. Cell cycle analysis showed that 2-APB and SKF-96395 lengthen the S and G2/M phases, which would account for the reduction in cell proliferation.
Our results indicate that CCE, likely attributed to the activation of TRPCs, might be the main route for Ca2+ influx involved in osteoblast proliferation.
成人骨组织不断进行重塑，骨量通过破骨细胞骨吸收和成骨细胞骨形成之间的平衡得以维持。成骨细胞增殖的改变可能部分解释了骨质疏松症骨丢失时这两个过程之间缺乏平衡的原因。钙（Ca2+）在众多细胞功能中发挥调控作用；然而，钙库操纵性钙内流（CCE）在骨细胞增殖中的作用研究较少。
本研究旨在探讨CCE在成骨样MG-63细胞增殖中的作用。
对CCE进行药理学特征分析，同时评估瞬时受体电位香草酸亚型（TRPC）通道的表达及细胞增殖情况。
毒胡萝卜素使细胞内Ca2+储存耗竭，从而诱导MG-63细胞发生CCE；其特征为细胞内Ca2+迅速短暂升高，随后在刺激细胞增殖的条件下，即血清和血小板衍生生长因子作用下，出现显著的CCE。钙库操纵性钙通道抑制剂（2-氨基乙氧基二苯硼酸和SKF-96365）可阻止CCE，而电压依赖性钙通道阻滞剂则无此作用。细胞中显示出多种TRPC通道的表达，其中一些已被证明与CCE有关。电压依赖性钙通道阻滞剂对成骨细胞增殖无影响，而毒胡萝卜素、2-氨基乙氧基二苯硼酸和SKF-96395可抑制其增殖。细胞周期分析表明，2-氨基乙氧基二苯硼酸和SKF-96395使S期和G2/M期延长，这可以解释细胞增殖的减少。
我们的结果表明，可能归因于TRPC激活的CCE可能是参与成骨细胞增殖的Ca2+内流的主要途径。
