Zhao Wanming, Wang Xingyu, Sun Kai-Hui, Zhou Lan
Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
Department of Medicine Lung Biology Lab, University of California, San Francisco, San Francisco, California, United States of America.
PLoS One. 2018 Jan 10;13(1):e0191031. doi: 10.1371/journal.pone.0191031. eCollection 2018.
α-Smooth muscle actin (α-SMA) is used as a marker for a subset of activated fibrogenic cells, myofibroblasts, which are regarded as important effector cells of tissue fibrogenesis. We address whether α-SMA-expressing myofibroblasts are detectable in fibrotic muscles of mdx5cv mice, a mouse model for Duchenne muscular dystrophy (DMD), and whether the α-SMA expression correlates with the fibrogenic function of intramuscular fibrogenic cells. α-SMA immunostaining signal was not detected in collagen I (GFP)-expressing cells in fibrotic muscles of ColI-GFP/mdx5cv mice, but it was readily detected in smooth muscle cells lining intramuscular blood vessel walls. α-SMA expression was detected by quantitative RT-PCR and Western blot in fibrogenic cells sorted from diaphragm and quadriceps muscles of the ColI-GFP/mdx5cv mice. Consistent with the more severe fibrosis in the ColI-GFP/mdx5cv diaphragm, the fibrogenic cells in the diaphragm exerted a stronger fibrogenic function than the fibrogenic cells in the quadriceps as gauged by their extracellular matrix gene expression. However, both gene and protein expression of α-SMA was lower in the diaphragm fibrogenic cells than in the quadriceps fibrogenic cells in the ColI-GFP/mdx5cv mice. We conclude that myofibroblasts are present in fibrotic skeletal muscles, but their expression of α-SMA is not detectable by immunostaining. The level of α-SMA expression by intramuscular fibrogenic cells does not correlate positively with the level of collagen gene expression or the severity of skeletal muscle fibrosis in the mdx5cv mice. α-SMA is not a functional marker of fibrogenic cells in skeletal muscle fibrosis associated with muscular dystrophy.
α-平滑肌肌动蛋白（α-SMA）被用作活化的纤维化细胞亚群——肌成纤维细胞的标志物，肌成纤维细胞被视为组织纤维化形成的重要效应细胞。我们研究了在杜氏肌营养不良症（DMD）的小鼠模型mdx5cv小鼠的纤维化肌肉中是否可检测到表达α-SMA的肌成纤维细胞，以及α-SMA的表达是否与肌肉内纤维化细胞的纤维化功能相关。在ColI-GFP/mdx5cv小鼠的纤维化肌肉中，未在表达I型胶原蛋白（GFP）的细胞中检测到α-SMA免疫染色信号，但在肌内血管壁内衬的平滑肌细胞中很容易检测到。通过定量逆转录-聚合酶链反应（RT-PCR）和蛋白质免疫印迹法在从ColI-GFP/mdx5cv小鼠的膈肌和股四头肌中分选的纤维化细胞中检测到了α-SMA的表达。与ColI-GFP/mdx5cv小鼠膈肌中更严重的纤维化一致，通过细胞外基质基因表达评估，膈肌中的纤维化细胞比股四头肌中的纤维化细胞具有更强的纤维化功能。然而，在ColI-GFP/mdx5cv小鼠中，膈肌纤维化细胞中α-SMA的基因和蛋白表达均低于股四头肌纤维化细胞。我们得出结论，肌成纤维细胞存在于纤维化的骨骼肌中，但通过免疫染色无法检测到它们表达α-SMA。肌肉内纤维化细胞中α-SMA的表达水平与mdx5cv小鼠中胶原蛋白基因表达水平或骨骼肌纤维化的严重程度无正相关。α-SMA不是与肌营养不良相关的骨骼肌纤维化中纤维化细胞的功能性标志物。
