Research Of Healing Promotion Following Skeletal Muscle Injury

Part IResearch of Insulin-like Growth Factors (IGF) in Promoting the Healing Following Skeletal Muscles InjuryObjective : The study was undertaken to investigate the effect of insulin-like growth factors(IGF)on the healing course and healing quality following skeletal muscles contusion in Sprague-Dawley (SD) rats in histology,ultrastructure and molecular biology, to discuss the possible mechanisms of insulin-like growth factors in promoting the healing. Methods: The rats undergone anesthesia with 1％ thiopental sodium (0.5ml/100g)received a single impact trauma at the medial-middle gastrocnemius muscle of the right leg, and then a following injection was given at the subcutaneous part of contusion site with one of following three, 0.9% sodium chloride (S group) , IGF－I 1.5(g (I group) , IGF－II 1.5(g (II group). The rats were divided into three groups. The following observations were made. (1) mRNA analysis (n=44): The rats were sacrificed under thiopental sodium anesthesia and cervical vertebra dislocation at 1,2,3,4,6,9,13 day after the muscle trauma. (Two experimental-rats sacrificed each time and another 2 for control). The medial gastrocnemius muscles including injuried areas were resected. The corresponding area on the same side of the normal rats were resected as control. The samples were treated through reverse transcription(RT),polymerase chain reaction(PCR) and agarose gel electrophoresis. (2) The histological analysis (n=20): The rats were sacrificed at 1,4,6 day after the muscle trauma (two rats sacrificed each time, two normal for control). The samples were fixed in 4% formaldehyde and cut at the midline-medial half was embedded in paraffin. Serial 5 (m sections were cut for morphological investigation. (3)Ultrastructural analysis (n=32): The rats were sacrificed at 1,4,6,9,13 day after the muscle trauma (2 rats sacrificed each time, two normal for control). The samples were fixed in 2.5% glutaraldehyde and then in 1% OsO4, dehydrated and emdedded in Epon. Sections were double stained with uranyl acetate and lead citrate and examined in a JEM 100 CX electron microscope.Results: (1) mRNA: (S) IGF-I mRNA is increased at 2,3,4,6,9,13d after tauma, IGF-II mRNA is increased at 3,4,6,9d after tauma, especially at 4,6d. (I) IGF-I mRNA is increased at 1,2,3,4,6,9d after tauma, IGF-II mRNA is also increased at 1,2,3,4,6,9,13d after tauma. (II) IGF-I mRNA is increased at 1,2,3,4d after tauma, IGF-II mRNA is increased at 1,2,3,4,6,9,13d after tauma. (2)Histological changes: the gastrocnemius had congestion,edema and rupture after trauma. The myoblasts and myotubes grew more and faster in groups I and II than group S, the myotubes fused to myofibres earlier in I and II. (3) Ultrastructural changes: groups I and II formed basement membrane "borders"myofibrils and myotubes earlier than group S. Conclusion: We tested the expression of the endogenic IGF mRNA with RT-PCR methods for the first time. We found that Local injection of IGF could promote earlier secretion of endogenic IGF mRNA; could stimulate the proliferation of myoblasts, to hasten the formation and fusion of myotubes, to accelerate the healing of skeletal muscular injury. Key words: Insulin-like growth factor,skeletal muscle,injury,heal...