| Multifidus muscle (MD) which is located under erector spinae is one of the most important muscle groups to keep spinal stability. MD’s injury, atrophy or dysfunction is closely related to the occurrence of chronic low back pain. Acupuncture for low back pain has a unique effect. Some researches have shown that acupuncture can improve the regeneration of injured skeletal muscle through promoting the proliferation of satellite cells which involved in tissue repair. The mechanism maybe involved in conditioning microcirculation, increasing the activity of free radicals, regulating the secretion of cytokines or other ways, yet there are no reports about treating multifidus muscle injury with acupuncture methods recently. Objective1. To cause the MD toxicity of rats with intramuscular injection of 0.5%bupivacaine to the lumber MD and accomplish the duplication of the MD injury model.2. To observe the effect of electro-acupuncture on MD injury by morphological observation, fiber cross cectional area (fCSA), insulin like growth factor 1 (IGF-1) expression and MyoD expression of rats with BPVC induced MD toxicity, and discuss the possible mechanism of muscle tissue regeneration with the effects of Weizhong (BL40) and Shenshu (BL23).Methods1. The dumplication of multifidus muscles injury model of rats after injection of BPVC. 72 male Sprague-Dawley rats were randomly divided into three groups that included blank group (BG, n=24), model group (MG, n=24) and model control group (CG), each group then divided evenly into four subgroups (2hr, day 4, day 7 and day 14) and each subgroup has 6 samples. MD (L4 and L5 sections) toxicity was established by injecting 0.5% bupivacaine hydrochloride, and normal saline injection as control (CG). The serum creatine kinase (CK) was detected after 2 hours of modeling. The multifidus muscle of each rodent was stained with HE and Masson to observe pathological changes, and immunohistochemical staining was used to observe caspase-3 expression.2. The effects of Electroacupuncture at BL40 on regeneration and IGF-1/MyoD Expression of BPVC induced rats with MD injury.72 male Sprague-Dawley rats were randomly divided into four groups that included blank group (BG, n=18), model group (MG, n=18), Weizhong (BL40) electroacupuncture group (WG, n=18) and Shenshu (BL23) electroacupuncture group (SG, n=18), each group then divided evenly into three subgroups (day 4, day 7 and day 14) and each subgroup has 6 samples. MD (L4 and L5 sections) toxicity was established by injecting 0.5% bupivacaine hydrochloride. The WG and LG accepted electroacupuncture treatment for 20min once a day until the day before draw meterials. The multifidus muscle of each rodent was stained with HE to observe pathological changes and make statistical of the regenerated new fibers’CSA, immunohistochemical staining was used to observe IGF-1 and MyoD expressions, thus discussed the mechanism of the regenerative effects of electro-acupuncture at Weizhong (BL40) and Shenshu (BL23) points on rats MD injury.Results1. BPVC injection can accurately reach the rat MD, causing localized necrosis of the lumbar MD of rats. The tissue morphology with HE staining and Masson staining were significantly changed before and after modeling at different time points. There were a large number of macrophages infiltration and some newborn fibers at day 4, and more young fibers were found at day 7. At day 14, some new fibers had merged into myotubes, but the myotubes still immature. BPVC caused a process of degeneration-regeneration of the muscle fibers and did not normalize at day 14. Serum CK levels were significantly increased (P<0.01) after 2 hours of modeling. The expression of caspase-3 with cytoplasm was observed at day 4 and significatelly high than BG (P＜0.01) and CG (P<0.01), and decreased gradually at day 7 and day 14, but still high than the other two groups statistically. There were no differences between BG and CG.2. The effects of Electroacupuncture at BL40 on regeneration and IGF-1/MyoD Expression of BPVC induced rats with MD injury. WG and SG were recovered fast and better than MG with morphological changes. The expression of IGF-1 at day4 ranked as WG, SG, MG and BG (P＜0.01), while ranked as SG=WG=MG and BG (P＜0.01) at day 7. There were no difference between MG and BG, but SG was significant higher than WG and MG (P<0.01) at day 14. MyoD expression at day 4 ranked as WG, SG, MG and CG (P<0.01). The expression of MyoD were marked declined at day 7 and ranked as MG, WG=SG and BG (P＜0.01). WG of muscle fibers’CSA were bigger than MG (P<0.05, P<0.01) at day 7 and day 14. The fibers’CSA of SG at day 7 had no significant difference with MG, but higher than MG at day 14 (P＜0.05). There were no statistically difference both at day 7 and day 14 between WG and SG, but WG had the ascending trend compared with SGConclusion1. BPVC muscular injection caused the rat lumbar MD injury accurately, markly increased CK level in 2 h, caused the cell membranes’damagement.and induced morphological changes at different times. BPVC caused not only necrosis, but apoptosis as well with caspase-3 positive expression.2. Electroacupuncture at Weizhong (BL40) and Shenshu (BL23) can promote rat lumbar multifidus muscles’regeneration after BPVC injury. BL40 worked better than BL23 on the regeneration of MD at the early phase, which may be related to the up-regulation of IGF-1 and MyoD, and complete the myoblast differentiation in advance.
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