α7nAChR is expressed in satellite cells at different myogenic status during skeletal muscle wound healing in rats

Recent study has reported that alpha 7 nicotine acetylcholine receptor (alpha 7nAChR) is expressed in regenerated multinucleated myotubes. But the distribution of alpha 7nAChR in satellite cells in different myogenic status is unknown. A preliminary study on the dynamic distribution of alpha 7nAChR in satellite cells was performed by double indirect immunofluorescent procedures during skeletal muscle wound healing in rats. An animal model of skeletal muscle contusion was established in 40 Sprague-Dawley male rats. Samples were taken at 1, 3, 5, 7, 9, 13, 17 and 21 days after injury, respectively (five rats in each post-traumatic interval). Five rats were employed as control. In normal muscle specimens, weak immunoreactivity for alpha 7nAChR was detected in a few satellite cells (considered as quiescent). alpha 7nAChR-positive signals were observed in proliferated and differentiated satellite cells and regenerated multinucleated myotubes in the wounded areas. By morphometric analysis, the average number of alpha 7nAChR(+)/Pax7(+) and alpha 7nAChR(+)/MyoD(+) cells climaxed at 5 days post-injury. The average number of alpha 7nAChR(+)/myogenin(+) cells was significantly increased from 3 to 9 days post-injury as compared with other posttraumatic intervals. The protein level of alpha 7nAChR maximized at 9 days post-injury, which implies that alpha 7nAChR was associated with the satellite cells status. Our observations on expression of alpha 7nAChR in satellite cells from quiescence to myotube formation suggest that alpha 7nAChR may be involved in muscle regeneration by regulating satellite cell status.