Li Bo, Chen Liang, Gu Yu-Dong
Department of Hand Surgery, Huashan Hospital and Institutes of Biomedical Sciences, Fudan University; Shanghai Key Laboratory of Peripheral Nerve and Microsurgery, Shanghai, China.
Neural Regen Res. 2020 Sep;15(9):1678-1685. doi: 10.4103/1673-5374.276341.
The time window for repair of the lower trunk is shorter than that of the upper trunk in patients with obstetric brachial plexus palsy. The denervated intrinsic muscles of the hand become irreversibly atrophic much faster than the denervated biceps. However, it is unclear whether the motor endplates of the denervated interosseous muscles degenerate more rapidly than those of the denervated biceps. In this study, we used a rat model of obstetric brachial plexus palsy of the right upper limb. C5-6 was lacerated distal to the intervertebral foramina, with concurrent avulsion of C7-8 and T1, with the left upper limb used as the control. Bilateral interossei and biceps were collected at 5 and 7 weeks. Immunofluorescence was used to assess the morphology of the motor endplates. Real-time quantitative polymerase chain reaction and western blot assay were used to assess mRNA and protein expression levels of acetylcholine receptor subunits (α, β and δ), rapsyn and β-catenin. Immunofluorescence microscopy showed that motor endplates in the denervated interossei were fragmented, while those in the denervated biceps were morphologically intact with little fragmentation. The number and area of motor endplates, relative to the control side, were significantly lower in the denervated interossei compared with the denervated biceps. mRNA and protein expression levels of acetylcholine receptor subunits (α, β and δ) were significantly lower, whereas β-catenin protein expression was higher, in the denervated interossei compared with the denervated biceps. The protein expression of rapsyn was higher in the denervated biceps than in the denervated interossei at 7 weeks. Our findings demonstrate that motor endplates of interossei are destabilized, whereas those of the biceps remain stable, in the rat model of obstetric brachial plexus palsy. All procedures were approved by the Experimental Animal Ethics Committee of Fudan University, China (approval No. DF-187) in January 2016.
在产瘫性臂丛神经麻痹患者中，下干修复的时间窗比上干短。手部失神经支配的固有肌比失神经支配的肱二头肌发生不可逆萎缩的速度要快得多。然而，目前尚不清楚失神经支配的骨间肌运动终板是否比失神经支配的肱二头肌运动终板退变更快。在本研究中，我们采用了右侧上肢产瘫性臂丛神经麻痹的大鼠模型。在椎间孔远端切断C5-6，并同时撕脱C7-8和T1，以左侧上肢作为对照。在5周和7周时采集双侧骨间肌和肱二头肌。采用免疫荧光法评估运动终板的形态。采用实时定量聚合酶链反应和蛋白质印迹法评估乙酰胆碱受体亚基（α、β和δ）、rapsyn和β-连环蛋白的mRNA和蛋白质表达水平。免疫荧光显微镜检查显示，失神经支配的骨间肌运动终板破碎，而失神经支配的肱二头肌运动终板形态完整，几乎没有破碎。与失神经支配的肱二头肌相比，失神经支配的骨间肌运动终板的数量和面积相对于对照侧显著降低。与失神经支配的肱二头肌相比，失神经支配的骨间肌中乙酰胆碱受体亚基（α、β和δ）的mRNA和蛋白质表达水平显著降低，而β-连环蛋白的蛋白质表达水平较高。在7周时，失神经支配的肱二头肌中rapsyn的蛋白质表达高于失神经支配的骨间肌。我们的研究结果表明，在产瘫性臂丛神经麻痹大鼠模型中，骨间肌的运动终板不稳定，而肱二头肌的运动终板保持稳定。所有实验程序均于2016年1月获得中国复旦大学实验动物伦理委员会批准（批准号：DF-187）。
