Studies On The Relationship Between Inflammatory Response And Satellite Cell Regeneration In Skeletal Muscle Injury And Repair Process

Acute injury of skeletal muscle is one of common injuries in physical exercises and sporting trainings, and the incidence rate is high. Long inflammatory reaction time after injury and bad healing quality lead to hematoma organization and scar repairing of muscle tissue, which degrades muscle contraction performance so that the probability of muscle re-injury increases. It influences badly people's daily study,work and movement and has latent threatening to athlete's sporting capacity and sporting life. So, it is one crucial topic at the research domain of sporting medicine that studying enough skeletal muscle injury mechanism; exploring how to shorten inflammatory reaction time after injury, quickening muscle regeneration rate and elevating healing quality.After acute injury of skeletal muscle, firstly, the injury location takes place of disorganization, degeneration and necrosis of muscle fiber, and then inflammatory cells and inflammatory mediators infiltrate to impaired location. On the one hand, the inflammatory cells and inflammatory mediators phagocytize necrosis cells and impaired cell debris; on the other hand, they activate muscle satellite cells (locate among the basilar membrane and sarcolemma, and in dormancy state when quite) by secreting growth factor to proliferate to form new myotube cells which develop muscle fiber, repair impaired muscle fiber and accomplish muscle regenerative process. The inflammatory cells and inflammatory mediators have considerable regulation actions to muscle regeneration and the actions are accompanied.The method of treating skeletal muscle injury includes healing naturally and interfered healing non-naturally (drug,biology and abiology).In the experiment, construct 4 models of skeletal muscle injury (gastrocnemius, soleus,fast muscle and slow muscle). Draw materials from the models at 6;24 and 72 hours of healing naturally, do histological sections (HE stain) and observe microstructure under optical microscope. We find that eligible inflammatory cells may promote satellite cells activation. In other words, inflammatory cells can advance satellite cells activation when the quantity is more in one certain range, but they can inhibit SC activation when the quantity exceeds one range (the degree of muscle injury is worse).In 4 models, we select 2 skeletal muscle injury models induced by contusion and treadmill and cure them by drug (asperse Yunnan Baiyao at impaired location) in recovery phase after injury). Take gastrocnemius and soleus of treated side and untreated side from hind limbs of 4 rats respectively, do slices, mark by immunohistochemistry and HE staining at 24 hours;2 days;4 days;7 days;10 days and 14 days after administer respectively.In HE slice of skeletal muscle injury induced by treadmill, we find that the quantities of inflammatory cells and satellite cells show a regular change in treated group and untreated group after injury. Satellite cells in impaired muscle begin to appear at 24 hours after injury, but the quantity is not much on the second day of inflammatory cells peak; the quantity begins to rise at extent on the 7th day when inflammatory cells of impaired muscle decrease to suitable quantity; the satellite cells begin to low on the 10th and 14th days when the quantity of inflammatory cells is little. Meanwhile, the quantity of inflammatory cells in untreated group is higher obviously than it in treated group (* P﹤0.01). It indicates that Yunnan Baiyao may inhibit the inflammatory cells of rat impaired skeletal muscle at one certain degree.In immunohistochemistry slices of skeletal muscle injury induced by contusion, the expression conditions of MyoD protein (one molecule symbol during the differentiation of sarcoblast) in satellite cells are followings: it is expressed continuously in gastrocnemius (fast muscle) of treated group at 24 hours,2 days and 4 days after injury (positive); it is expressed at 4th day in fast muscle of untreated group; it is expressed at 2th day after injury in soleus (slow muscle) of treated group; it is negative in slow muscle of untreated group. The results show that the MyoD protein expression in muscle satellite cells is stronger in treated group / fast muscle than in untreated group / slow muscle.So, Yunnan Baiyao can inhibit the destruction of inflammatory cells to impaired muscle tissue, shorten inflammatory reaction process and promote the proliferation of satellite cells in order to taking action in repairing process of impaired skeletal muscle, and the action is notable in fast muscle fiber.For studying advanced the action mechanism about inflammatory cells of impaired skeletal muscle in recovery phase to satellite cells, we select LTB4 (one important inflammatory mediator in inflammatory process) and try to explore the relation of LTB4 in impaired skeletal muscle and proliferation and differentiation of satellite cells.We detect and find the expression of BLT1 and BLT2 (LTB4 receptor) during the cultivating course of primitive satellite cells in vitro. It has been proved that LTB4 can promote the proliferation and differentiation of sarcoblast by some experimental methods including immunofluorescence,fluorescence staining of sarcoblast and counting etc. The effect shows density dependence that LTB4 promotes the proliferation of sarcoblast and it has notable action when the density is 60 nM. LTB4 promotes the differentiation of sarcoblast by changing the expression of mRNA and protein about MyoD and M-cadherin.It is definite that LTB4 regulates the proliferation and differentiation of sarcoblast through signal path mediated by BLT1, after finishing detecting the influence about specific inhibitor of BLT1 and BLT2 to the proliferation and differentiation of sarcoblast.Above all, the research observes the influence about inflammatory cells to muscle satellite cells and the relations, on the base of studying four models about acute injury of skeletal muscle, in the stage of recovery phase of rat impaired skeletal muscle which is treated by healing naturally or interfering with Yunnan Baiyao. We explore the action mechanism of Yunnan Baiyao promoting muscle regeneration in the molecular level and study mainly if LTB4 (one inflammatory mediator produced in inflammatory reaction of acute injury of skeletal muscle) can induce the proliferation and differentiation of skeletal muscle satellite cells. The result dictates that LTB4 promotes the proliferation and differentiation of satellite cells in the course of recovery of impaired skeletal muscle through the signal path mediated by BLT1.