Eccentric Exercise Improves Chronic Achilles Tendinopathy Healing Via Up-regulate Scx To Increases Type Ⅰ Collagen Synthesis

Objective:The healing of chronic tendinopathy has always been a difficult problem in the field of sports medicine.In this study,the animal model of chronic Achilles tendinopathy was used to study the repair effect of eccentric exercise on chronic Achilles tendinopathy,explore its relationship with Scx,type I collagen and type III collagen,and reveal the mechanism of eccentric exercise promoting the healing of chronic Achilles tendinopathy.Methods:Firstly,the rat model of chronic Achilles tendinopathy was established.Thirty six 8-week old SPF male SD rats,weighing 200-250 g,were randomly divided into control group,model group and exercise group,with 12 rats in each group.The model of chronic Achilles tendinopathy was made in the Achilles tendon of the right lower limb in model group and exercise group.Methods: 2% Pentobarbital Sodium(0.2ml / 100g)was injected intraperitoneally for anesthesia,the lower limbs were depilated,the Achilles tendon was located,and 30 ul type I collagenase(10mg / ml)prepared in PBS was injected into the middle of the Achilles tendon.After that,the rats in the control group and the model group were fed conventionally.After 15 days of routine feeding,the rats in the exercise group began to receive eccentric exercise intervention.The intervention method was carried out in the way of animal running downhill.The exercise intensity was-15°,15m/min,30min/d,three times per week(with an interval of one day)for 4 weeks.After 4 weeks,the Achilles tendon was examined by ultrasound,and then the rats in each group were sacrificed.The Achilles tendon tissues were collected for general observation.The pathological changes of Achilles tendon tissues were examined by HE staining.The protein and m RNA expressions of col Ⅰ,col Ⅲand Scx were tested by immunohistochemistry and realtime PCR,and the protein expressions of col Ⅰ,col Ⅲ,Scx,MMP-2 and MMP-9 were tested by Western blot.Results:1.The general observation.Compared with the control group,the Achilles tendon tissue of the model group was off-white,the surface was rough and matte,and the tissue hyperplasia and adhesion were serious.The color of Achilles tendon tissue in the exercise group was white,with slight hyperplasia and adhesion,and the overall situation was significantly better than that in the model group.2.The ultrasound images.Compared with the normal group,the local echo signals of the lesions in the model group were not uniform and the ultrasound images were disordered.There was no significant difference between the exercise group and the normal group.3.The results of HE staining.The tendon tissue of the model group showed disorganized collagen fibers with partial fracture,hypervascularity and increased cells accompanied by round and enlarged nuclei.The tissue morphology of exercise group was significantly improved and similar to normal tendon tissue.4.Immunohistochemical results.In the model group,the positive expression of type I collagen decreased significantly,while the positive expression of type III collagen increased significantly,and the positive expression of Scx protein around the nucleus increased,compared with control group.In the exercise group,the positive expression of type I collagen increased significantly,the positive expression of type III collagen decreased significantly,and the positive expression of Scx protein increased significantly.5.The m RNA expression results.In model group,the m RNA expression of type I collagen decreased,while the m RNA expression of type III collagen increased,and the m RNA expression of Scx increased,compared with control group.The m RNA expression of type I collagen in the exercise group was significantly higher than that in the model group,which was equivalent to that in the control group;Type III collagen m RNA was still higher than that in the control group,but significantly lower than that in the control group and model group;The m RNA expression of Scx was significantly higher than that of the other two groups.6.Western blot showed that the protein expression of type I collagen,type III collagen and Scx were consistent with their m RNA expression.The protein expression of MMP2 and MMP9 in the model group was higher than that in the other two groups;There was no significant difference between the control group and the exercise group.Conclusion:1.In this animal model of Achilles tendinopathy,eccentric exercise promotes the repair of tendon tissue.2.Eccentric exercise can increase the synthesis of type I collagen in tendon by up regulating Scx,so as to promote the healing of chronic Achilles tendinopathy.3.The effect of eccentric exercise on the repair of chronic Achilles tendinopathy may also be related to its regulation of the expression of MMP2 and MMP9 in extracellular matrix.