Overuse Injury Histology Cause And Effect Of Acupuncture On The Prevention And Treatment In Skeletal Muscle

Objective:Overuse injuries are common musculoskeletal disorders in both workplace and athletic environments. Despit epidemiological evidence for the role of tissue microtraumas in the onset and progression of overuse injuries, complete understanding of overuse injuries requires further elucidation of pathophysiological mechanisms of the tissue response, particularly in the early stage of these disorders. This study investigated overuse injury cause and effect of acupuncture on the prevention and treatment in skeletal muscle.Methods:One hundred and fifty-six male Sprague-Dawley rats were assigned randomly to five groups, namely the control (C), training groups(TG), training+acupuncture groups(TAG),1 week recovery group(1WRG) and 1 week acupuncture+recovery group(1WARG). Animal model of overuse was experimentally induced through 4 weeks low-intensity eccentric contractions(treadmill running,-16°,60-90min/day, 5days/week). In rats of TG, there were not any therapeutic interventions during 4 weeks training; In rats of TAG, deep needling at oblique position was applied immediately on vastus intermedius after every day training during 4 weeks training. After 4 weeks training, there were not any therapeutic interventions in rats of 1WRG during 1 week recovery; In rats of 1WARG, deep needling at oblique position was applied on vastus intermedius every day during 1 week recovery. During 4 weeks training and after lweek recovery, vastus intermedius(VI) were collected at weekly time points of 1-5 weeks. Transmission electron microscope(TEM) and scanning electron microscopy(SEM), was used to investigate skeletal muscle ultrastructural damage and collagen deposition, respectively; CollagenⅠand collagen IV was used to identify the change of collagen content; ED2 macrophages was used to identify the immune cell reaction after skeletal muscle injury.Results:In 4th week TG and 1WRG, skeletal muscle ultrastructural abnormalities changes were found, including Z-band streaming, widened intermyofibrillar spaces, the myofibril degradation, subsarcolemmal mitochondrial aggregate and accumulation of products of mitochondria degradation; In lth week-4thweek TG and 1WRG, an increase collagen content in expanded ECM, especially perimysium was accompanied by a decrease in the numbers of ED2. Expanded endomysium was always around expanded perimysium, and ED2 activity in perimysium gradually increased; However, In 4th week TAG and 1WARG, skeletal muscle ultrastructural abnormalities changes were repaired, namely sarcomere structural abnormalities recovery, including a decrease in the myofibril degradation and an increase in the numbers of mitochondrial biogenesis. Increased mitochondria typically clustered in small groups and/or longitudinally oriented in rows between the myofibrils; In lth week-4th week TAG and 1WARG, a decrease collagen content in expanded ECM, especially perimysium was accompanied by an increase in the numbers of ED2. Expanded endomysium was few around expanded perimysium, and ED2 activity in perimysium decreased.Conclusions:(1) Overuse injury induced skeletal muscle ultrastructural damage accumulation, perimysium collagen I deposition, and disturbing macrophages ED2 migratory pathway from perimysium to endomysium; (2) Cause of overuse injury wae perimysium collagen I deposition resulting from skeletal muscle ultrastructural damage accumulation; (3) Acupuncture promoted mitochondrial proliferation. Increased mitochondria accelerated skeletal muscle ultrastructural damage recovery, and therefore decreased perimysium tension, so improved macrophages ED2 migratory pathway, and further repaired skeletal muscle ultrastructural damage. Acupuncture finally prevented or treat skeletal muscle overuse injury.