The time-dependent expression of α7nAChR during skeletal muscle wound healing in rats

The study on time-dependent expression of alpha 7 nicotine acetylcholine receptor (alpha 7nAChR) was performed by immunohistochemistry, Western blotting, and real-time PCR during skeletal muscle wound healing in rats. Furthermore, co-localization of alpha 7nAChR with macrophage or myofibroblast marker was detected by double immunofluorescence. A total of 50 Sprague-Dawley male rats were divided into control and contusion groups (3 h, 6 h, 12 h, 1 day, 3 days, 5 days, 7 days, 10 days, and 14 days post-injury). In the uninjured controls, alpha 7nAChR positive staining was observed in the sarcolemma and sarcoplasm of normal myofibers. In wounded specimens, a small number of polymorphonuclear cells, a number of macrophages and myofibroblasts showed positive reaction for alpha 7nAChR in contused zones. Morphometrically, the average ratios of alpha 7nAChR-positive cells were over 50 % from 3 to 10 days after contusion, and exceeded 60 % at 5 and 7 days post-injury. Besides, the positive ratios of alpha 7nAChR were < 50 % at the other posttraumatic intervals. By Western blotting analysis, the average ratio of alpha 7nAChR protein expression maximized at 7 days after injury, which was > 2.13. Similarly, the relative quantity of alpha 7nAChR mRNA expression peaked at 7 days post-wounding as compared with control by real-time PCR detection, showing a relative quantity of > 2.65. In conclusion, the expression of alpha 7nAChR is upregulated and temporally distributed in macrophages and myofibroblasts during skeletal muscle wound healing, which might be closely involved in inflammatory response and fibrotic repair after injury. Moreover, alpha 7nAChR is promising as a useful marker for wound age determination of skeletal muscle.