Effects Of Exhaustive Exercise And Blunt Contusion On Proliferation And AXIN And GSK-3β Contents Of Rat Skeletal Muscle Satellite Cells In

Objective:To study the effect of exhaustive exercise and contusion on rat satellite cells and AXIN、GSK-3β contents.Methods:Five-week-old male SD rats, were randomly divided into 4 groups,6 rats in each group:control group (Control C), exhaustive exercise group (Exhaustive E0), post-exhaustive exercise group 24h (E24), post-exhaustive exercise group 48h (E48). The exhaustive group performed an exhaustive downhill running to exhaustion state.18 more SD rats are taken and randomly divided into 3 groups,6 rats in each group:contusion immediate group (contusion Do),post-contusion 24h group (D24), post-contusion 48h group (D48). The exhaustive exercise groups and contusion groups were anesthetized with 20%urethane by an intraperitoneal injection at different time points after exhaustive exercise and the contusion respectively while the control group was at resting state.5ml bloods sample was taken from the abdominal aorta to make serum to measure AXIN and GSK-3β contents. The left quadriceps femoris was divided into two parts:one part was used immediately for cell culture experiments, the other was preserved by liquid nitrogen to measure AXIN and GSK-3β contents. In addition, take the left gastrocnemius for frozen section, observing the type of muscle fiber. And take the quadriceps femoris of three neonatal rats for cell culture experiment.Results:(1) The results of muscle satellite cell culture showed that, by separating the rat muscle tissue of digestion, satellite cells with myogenic ability and high purity could be obtained in vitro. During the early stages of culture, the satellite cells of each group were growing slowly except the newborn rats. On the fifth day, each group began to proliferate in quantity and they reached the peak of proliferation on the seventh day. Then the proliferation rate began to decrease. By comparing the results of each group, we concluded that the content of skeletal satellite cell in control group was the lowest and its proliferation rate was slowest, but the content of skeletal satellite cells in newborn rats was highest and the proliferation rate was fastest while the number of skeletal satellite cells in contusion groups was significantly larger than the exhaustive exercise groups, the proliferation rate was also faster than the exhaustive groups.(2) mATPase staining results showed that:Fast skeletal muscle fibers were dark brown while slow muscle fibers were grey. From the same visual field, the cross-sectional area of slow muscle fibers was significantly less than the fast muscle fiber, and the density of muscle fiber in exhaustive exercise group was higher than contusion group. Compared with the control group, the percentage of type Ⅰ muscle fibers had significantly reduced in exhaustive group from the same visual field (P<0.01). And the percentage of type Ⅱ muscle fibers in exhaustive group had increased (P<0.01). On the other hand, the percentage of type Ⅰ muscle fibers in contusion group had decreased (P<0.01), and the percentage of type Ⅱ muscle fibers had increased (P <0.01).(3) The results of Elisa showed that:the contents of AXIN, GSK-3β in skeletal muscle in exhaustive groups and contusion groups, compared to the control group, were significantly decreased while there is no significant differences between exhaustive group and contusion group.Conclusions:(1) Exhaustive exercise and contusion can effect on skeletal satellite cells, and activate the skeletal satellite cells to proliferate. The number of skeletal satellite cells in the contusion groups was significantly larger than that of exhaustive group. It may be induced to the stronger stimulus by contusion. The newborn rats satellite cells own the strongest and proliferation in the period.(2) The percentage of type Ⅰ muscle fibers in exhaustive group has reduced while the percentage of type Ⅱ muscle fibers in exhaustive group has increased. On the other hand, the percentage of type Ⅰ muscle fibers in contusion group has decreased while the percentage of type Ⅱ muscle fibers in contusion group has increased. There was the tendency from slow to fast.(3) Compared with the control group, the contents of AXIN, GSK-3P in skeletal muscle were evidently decreased in exhaustive groups and contusion groups while there was no significant difference between the groups of exhaustive and contusion. The contents of AXIN, GSK-3β can be decreased by exhaustive exercises and contusion. The AXIN and GSK-3β may play a negative regulatory roles in terms of activating skeletal satellite cells and repairing of skeletal muscle injury.