Histological characteristics of exercise-induced skeletal muscle remodelling.

This study aims to analyse the pathological features of skeletal muscle injury repair by using rats to model responses to different exercise intensities. Eighty-four rats were randomly divided into five groups for treadmill exercise. The short-term control, low-intensity, medium-intensity and high-intensity groups underwent gastrocnemius muscle sampling after 6, 8 and 12 weeks of exercise. The long-term high-intensity group underwent optical coherence tomography angiography and sampling after 18 weeks of exercise. RNA sequencing was performed on the muscle samples, followed by the corresponding histological staining. Differentially expressed genes were generally elevated at 6 weeks in the early exercise stage, followed by a decreasing trend. Meanwhile, the study demonstrated a negative correlation between time and the gene modules involved in vascular regulation. The modules associated with muscle remodelling were positively correlated with exercise intensity. Although the expression of many genes associated with common angiogenesis was downregulated at 8, 12 and 18 weeks, we found that muscle tissue microvessels were still increased, which may be closely associated with elevated sFRP2 and YAP1. During muscle injury-remodelling, angiogenesis is characterized by significant exercise time and exercise intensity dependence. We find significant differences in the spatial distribution of angiogenesis during muscle injury-remodelling, which be helpful for the future achievement of spatially targeted treatments for exercise-induced muscle injuries.