Smith Cheryl A, Stauber Franciose, Waters Christopher, Alway Stephen E, Stauber William T
Department of Physiology and Pharmacology, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia, USA.
J Appl Physiol (1985). 2007 Feb;102(2):755-61. doi: 10.1152/japplphysiol.01503.2005. Epub 2006 Oct 26.
Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine implicated in inflammatory processes, wound healing, and fibrosis. In muscle diseases (i.e., dystrophy and inflammatory myopathy) and in animal models of muscle injury (i.e., produced by cardiotoxin, laceration, and eccentric contractions), increased TGF-beta was associated with muscle fibrosis and healing. Although TGF-beta transcript abundance was increased following injury, many studies presume that TGF-beta protein was also active as evident by increases in collagen transcript abundance. The purpose was to determine whether TGF-beta protein is present and active 48 h following injury. Using female rats, muscle strains were produced by stretching (50 stretches) the plantar flexor muscles. Forty-eight hours following injury, the medial gastrocnemius was removed and compartmentalized into five equal segments. Damaged myofibers with intracellular concanavalin A staining were counted. The percentage of damaged myofibers was significantly greater in the distal-most segment. TGF-beta was assessed by using immunohistochemistry, RT-PCR, and immunoblot analysis. Immunohistochemistry revealed the presence of TGF-beta1 in areas of myofiber injury, whereas TGF-beta2 was not detected. Increases in TGF-beta1 and TGF-beta2 transcript abundance following strain injury were documented by RT-PCR analysis. Increases in TGF-beta1 and TGF-beta2 precursor abundance were observed following strain injury by using immunoblot analysis but there was no change in active TGF-beta abundance. Although there was no correlation between the amount of cellular injury and TGF-beta transcript and protein abundance, elevated levels of TGF-beta1 and TGF-beta2 precursor proteins were present in strain-injured skeletal muscles 48 h after injury.
转化生长因子-β（TGF-β）是一种多功能细胞因子，参与炎症过程、伤口愈合和纤维化。在肌肉疾病（如营养不良和炎性肌病）以及肌肉损伤的动物模型（如由心脏毒素、撕裂伤和离心收缩产生的模型）中，TGF-β水平升高与肌肉纤维化和愈合有关。尽管损伤后TGF-β转录本丰度增加，但许多研究推测TGF-β蛋白也具有活性，这从胶原蛋白转录本丰度的增加可以明显看出。本研究的目的是确定损伤后48小时TGF-β蛋白是否存在并具有活性。使用雌性大鼠，通过拉伸（50次拉伸）跖屈肌造成肌肉拉伤。损伤后48小时，取出内侧腓肠肌并将其分成五个相等的部分。对细胞内伴刀豆球蛋白A染色的受损肌纤维进行计数。最远端部分受损肌纤维的百分比显著更高。通过免疫组织化学、RT-PCR和免疫印迹分析评估TGF-β。免疫组织化学显示在肌纤维损伤区域存在TGF-β1，而未检测到TGF-β2。RT-PCR分析记录了拉伤后TGF-β1和TGF-β2转录本丰度的增加。免疫印迹分析观察到拉伤后TGF-β1和TGF-β2前体丰度增加，但活性TGF-β丰度没有变化。尽管细胞损伤量与TGF-β转录本和蛋白丰度之间没有相关性，但损伤后48小时，拉伤的骨骼肌中TGF-β1和TGF-β2前体蛋白水平升高。
