Osteoactivin upregulates expression of MMP-3 and MMP-9 in fibroblasts infiltrated into denervated skeletal muscle in mice
Osteoactivin upregulates expression of MMP-3 and MMP-9 in fibroblasts infiltrated into denervated skeletal muscle in mice
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DOI：
10.1152/ajpcell.00565.2004
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发表时间：
2005-09-01
影响因子：
5.5
通讯作者：
Yasui, N
中科院分区：
文献类型：
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作者：
Ogawa, T;Nikawa, T;Yasui, N
在这项研究中，我们研究了骨激活素（一种功能未知的I型膜糖蛋白）在小鼠骨骼肌因去神经支配（坐骨神经切除术）而萎缩中的病理生理作用。去神经支配增加小鼠腓肠肌骨活化素、波形蛋白、基质金属蛋白酶-3 （MMP-3）和MMP-9的含量。有趣的是，免疫组织化学分析显示，vimentin、MMP-3和MMP-9主要存在于浸润到失神经小鼠腓肠肌的成纤维细胞样细胞中，而骨激活素则表达在邻近成纤维细胞样细胞的肌纤维的肌膜中。基于这些发现，我们推断肌细胞中的骨激活素参与了浸润成纤维细胞的活化。为了解决这个问题，我们在体外和体内研究了骨激活素对成纤维细胞中MMPs表达的影响。骨活化素在NIH-3T3成纤维细胞中过表达可诱导MMP-3的表达，但在小鼠C2C12成肌细胞中不表达，表明骨活化素可能在功能上靶向成纤维细胞。重组小鼠骨活素处理增加了小鼠NIH-3T3成纤维细胞中I型胶原、MMP-3和MMP-9的数量。这些成纤维细胞标记蛋白的上调表达被肝素显著抑制，而整合素抑制剂则没有，这表明肝素结合基序在细胞外区域可能是骨活素的活性位点。在骨活素转基因小鼠中，与野生型小鼠相比，去神经支配进一步增强了浸润腓肠肌的成纤维细胞中MMP-3和MMP-9的表达。我们目前的研究结果表明，骨激活素可能作为成纤维细胞浸润到失神经骨骼肌的激活剂，并在调节细胞外基质的变性/再生中发挥重要作用。
In this study, we examined pathophysiological roles of osteoactivin, a functionally unknown type I membrane glycoprotein, in mouse skeletal muscle atrophied by denervation (sciatic neurectomy). Denervation increased the amounts of osteoactivin, vimentin, matrix metalloproteinase-3 (MMP-3), and MMP-9 in mouse gastrocnemius muscle. Interestingly, immunohistochemical analysis revealed that vimentin, MMP-3, and MMP-9 were mainly present in fibroblast-like cells infiltrated into denervated mouse gastrocnemius muscle, whereas osteoactivin was expressed in the sarcolemma of myofibers adjacent to the fibroblast-like cells. On the basis of these findings, we reasoned that osteoactivin in myocytes was involved in activation of the infiltrated fibroblasts. To address this issue, we examined effects of osteoactivin on expression of MMPs in fibroblasts in vitro and in vivo. Overexpression of osteoactivin in NIH-3T3 fibroblasts induced expression of MMP-3, but not in mouse C2C12 myoblasts, indicating that osteoactivin might functionally target fibroblasts. Treatment with recombinant mouse osteoactivin increased the amounts of collagen type I, MMP-3, and MMP-9 in mouse NIH-3T3 fibroblasts. The upregulated expression of these fibroblast marker proteins was significantly inhibited by heparin, but not by an integrin inhibitor, indicating that a heparin-binding motif in the extracellular domain might be an active site of osteoactivin. In osteoactivin-transgenic mice, denervation further enhanced expression of MMP-3 and MMP-9 in fibroblasts infiltrated into gastrocnemius muscle, compared with wild-type mice. Our present results suggest that osteoactivin might function as an activator for fibroblasts infiltrated into denervated skeletal muscles and play an important role in regulating degeneration/regeneration of extracellular matrix.