Regeneration of muscle fibers after myoblast injection into dystrophic muscle

1.肌肉再生：成年鸡慢肌(背阔肌前肌)和快肌(背阔肌后肌)表面冷损伤可诱导肌肉再生。在神经完整的纤维中，肌钙蛋白的表达比dystrophin早1d，在dystrophin出现与正常纤维相同的阶段后2周以上才转变为成体亚型。此外，尽管失神经肌肉中的再生纤维与神经肌肉中的肌钙蛋白表达类似，但其中许多纤维再次恢复到胚胎状态。然而，在神经完整的再生纤维和切除神经的再生纤维中，dystrophin的表达没有差异。这些结果表明，肌钙蛋白和肌营养不良蛋白基因的表达在再生过程中是独立调节的，前者的充分发育需要神经，而后者则不需要。分离的成肌细胞的培养：将肌动蛋白和肌球蛋白显微注射到体外培养的心肌细胞中，发现这些单体蛋白的掺入优先发生在发育中的肌原纤维的未成熟部分，在那里连接蛋白分布微弱而均匀。肌动蛋白的聚合和/或新形成的肌动蛋白细丝的添加似乎与肌原纤维中的肌球蛋白细丝发生解离，这些肌球蛋白产生于肌原纤维的A-I连接区。C2细胞注射后肌纤维形成：将PKH26标记的C2细胞注射到小鼠胫骨前肌(SCN和MDX)。这些被转移的C2细胞被看到与宿主肌肉纤维的成肌细胞融合并形成嵌合体纤维。该方法为遗传性肌肉疾病基因治疗的进一步基础研究奠定了基础。

1. Muscle regeneration : Muscle regeneration was evoked by a cold injury on the surface of slow (the anterior latissimus dorsi) and fast (the posterior latissimus dorsi) muscles of adult chickens. In the fibers with nerves intact, troponin was expressed 1 day earlier than dystrophin and changed to its adult isoform more than 2 weeks after the stage when dystrophin exhibited the same appearance as that in normal fibers. Further, although regenerating fibers in denervated muscle switched on the expression of troponin similarly to those in innervated muscle, many of them again reverted to an embryonic state. However, no difference was found in the dystrophin expression between regenerating fibers with nerves intact and those with nerves resected. These results indicate that the expression of troponin and dystrophin genes is regulated independently during regeneration and that nerves are required for the full development of the former protein while unnecessary for the latter.2. Culture of dissociated myoblasts : Microinjection of actin an myosin into cardiomyocytes in vitro revealed that incorporation of these monomeric proteins occurred preferentially at immature portions of developing myofibrils, where connectin was distributed faintly and uniformly. It seems that polymerization of actin and/or the addition of newly formed actin filaments occur in assoiation with myosin filaments in myofibrils and these of myosin arise from the A-I junctional regions of myofibrils.3. Muscle fiber formation after C2 cell injection : PKH26-labelled C2 cells were injected into the tibialis anterior muscle of mice (ScN and mdx). These transferred C2 cells were seen to fuse with myoblasts of the host muscle fibers and formed chimera fibers. This method will be useful for further basic investigations of gene therapy of genetic muscle diseases.