Local inhibition of nitrergic activity in tenotomized rats accelerates muscle regeneration by increasing fiber area and decreasing central core lesions

Muscular atrophy is a progressive degeneration characterized by muscular proteolysis, loss of mass and decrease in fiber area. Tendon rupture induces muscular atrophy due to an intrinsic functional connection. Local inhibition of nitric oxide synthase (NOS) by Nω-nitro-L-arginine methyl ester (L-NAME) accelerates tendon histological recovery and induces functional improvement. Here we evaluate the effects of such local nitrergic inhibition on the pattern of soleus muscle regeneration after tenotomy. Adult male Wistar rats (240 to 280 g) were divided into four experimental groups: control (n=4), tenotomized (n=6), vehicle (n=6), and L-NAME (n=6). Muscular atrophy was induced by calcaneal tendon rupture in rats. Changes in muscle wet weight and total protein levels were determined by the Bradford method, and muscle fiber area and central core lesion (CCL) occurrence were evaluated by histochemical assays. Compared to tenotomized (69.3±22%) and vehicle groups (68.1%±17%), L-NAME treatment induced an increase in total protein level (108.3±21%) after 21 days post-injury. A reduction in fiber areas was observed in tenotomized (56.3±1.3%) and vehicle groups (53.9±3.9%). However, L-NAME treatment caused an increase in this parameter (69.3±1.6%). Such events were preceded by a remarkable reduction in the number of fibers with CCL in L-NAME-treated animals (12±2%), but not in tenotomized (21±2.5%) and vehicle groups (19.6±2.8%). Altogether, our data reveal that inhibition of tendon NOS contributed to the attenuation of atrophy and acceleration of muscle regeneration.

肌肉萎缩是一种以肌肉蛋白水解、质量丢失及肌纤维面积减小为特征的进行性退行性病变。由于内在的功能关联，肌腱断裂可诱发肌肉萎缩。通过局部给予Nω-硝基-L-精氨酸甲酯（L-NAME）以抑制一氧化氮合酶（nitric oxide synthase, NOS）的活性，可加速肌腱组织学修复并改善其功能。本研究旨在探讨该局部氮能抑制作用对肌腱切断术后比目鱼肌再生模式的影响。选取体重240~280g的成年雄性Wistar大鼠，随机分为4组：对照组（n=4）、肌腱切断组（n=6）、溶剂对照组（n=6）及L-NAME处理组（n=6）。本实验通过切断大鼠跟腱构建肌肉萎缩模型。采用布拉德福德（Bradford）法检测肌肉湿重与总蛋白水平变化，通过组织化学染色评估肌纤维面积及中央核病变（central core lesion, CCL）的发生情况。损伤后21天，与肌腱切断组（69.3±22%）及溶剂对照组（68.1%±17%）相比，L-NAME处理组的总蛋白水平升高至108.3±21%。肌腱切断组与溶剂对照组的肌纤维面积分别降至56.3±1.3%与53.9±3.9%，均出现显著降低；而L-NAME处理组的该指标则升高至69.3±1.6%。值得注意的是，L-NAME处理组出现中央核病变的肌纤维数量显著减少至12±2%，而肌腱切断组与溶剂对照组的该数值分别为21±2.5%与19.6±2.8%，无明显变化。综上，本研究结果表明，抑制肌腱NOS活性可减轻肌肉萎缩并加速肌肉再生。