PDF(Pubmed)
Abstract：
Dynamic remodeling of mitochondrial morphology through membrane dynamics are linked to changes in mitochondrial and cellular function. Although mitochondrial membrane fusion/fission events are frequent in cell culture models, whether mitochondrial membranes dynamically interact in postmitotic muscle fibers in vivo remains unclear. Furthermore, a quantitative assessment of mitochondrial morphology in intact muscle is lacking. Here, using electron microscopy (EM), we provide evidence of interacting membranes from adjacent mitochondria in intact mouse skeletal muscle. Electron-dense mitochondrial contact sites consistent with events of outer mitochondrial membrane tethering are also described. These data suggest that mitochondrial membranes interact in vivo among mitochondria, possibly to induce morphology transitions, for kiss-and-run behavior, or other processes involving contact between mitochondrial membranes. Furthermore, a combination of freeze-fracture scanning EM and transmission EM in orthogonal planes was used to characterize and quantify mitochondrial morphology. Two subpopulations of mitochondria were studied: subsarcolemmal (SS) and intermyofibrillar (IMF), which exhibited significant differences in morphological descriptors, including form factor (means ± SD for SS: 1.41 ± 0.45 vs. IMF: 2.89 ± 1.76, P < 0.01) and aspect ratio (1.97 ± 0.83 vs. 3.63 ± 2.13, P < 0.01) and circularity (0.75 ± 0.16 vs. 0.45 ± 0.22, P < 0.01) but not size (0.28 ± 0.31 vs. 0.27 ± 0.20 μm(2)). Frequency distributions for mitochondrial size and morphological parameters were highly skewed, suggesting the presence of mechanisms to influence mitochondrial size and shape. In addition, physical continuities between SS and IMF mitochondria indicated mixing of both subpopulations. These data provide evidence that mitochondrial membranes interact in vivo in mouse skeletal muscle and that factors may be involved in regulating skeletal muscle mitochondrial morphology.
摘要：
通过膜动力学的线粒体形态的动态重塑与线粒体和细胞功能的变化有关。尽管线粒体膜融合/裂变事件在细胞培养模型中很常见，线粒体膜是否在体内有丝分裂后肌纤维中动态相互作用尚不清楚。此外，缺乏完整肌肉中线粒体形态的定量评估。这里,使用电子显微镜（EM），我们提供了完整小鼠骨骼肌中相邻线粒体膜相互作用的证据。还描述了与线粒体外膜束缚事件一致的电子致密线粒体接触位点。这些数据表明，线粒体膜在体内线粒体之间相互作用，可能会引起形态转变，亲吻和奔跑的行为，或其他涉及线粒体膜之间接触的过程。此外，使用正交平面中的冷冻断裂扫描EM和透射EM的组合来表征和量化线粒体形态。研究了线粒体的两个亚群：肌膜下（SS）和肌间纤维（IMF），在形态学描述符上表现出显著差异，包括形状因子(SS的平均值±SD：1.41±0.45与IMF：2.89±1.76，P<0.01）和纵横比（1.97±0.83vs.3.63±2.13，P<0.01）和圆度（0.75±0.16vs.0.45±0.22，P<0.01），但不是大小（0.28±0.31vs.0.27±0.20μm(2))。线粒体大小和形态参数的频率分布高度偏斜，表明存在影响线粒体大小和形状的机制。此外,SS和IMF线粒体之间的物理连续性表明两个亚群混合。这些数据提供了证据，表明线粒体膜在小鼠骨骼肌中体内相互作用，并且因子可能参与调节骨骼肌线粒体形态。
