Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 114, Issue 2, Pages 161-171Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.01096.2012
Keywords
skeletal muscle mitochondria; myofiber; outer mitochondrial membrane; scanning and transmission electron microscopy; mitochondrial reticulum
Categories
Funding
- National Science and Engineering Research Council of Canada (NSERC)
- Institute of Neuroscience as part of the Canadian Epigenetics, Environment and Health Research Consortium (CEEHRC)
- Biotechnology and Biological Sciences Research Council (BBRC)
- Engineering and Physical Sciences Research Council (EPSRC)
- Economic and Social Research Council (ESRC)
- Medical Research Council (MRC)
- Wellcome Trust Centre for Mitochondrial Research
- National Institute for Health Research Newcastle Biomedical Research Centre
- Medical Research Council [G0700718, MR/K000608/1] Funding Source: researchfish
- National Institute for Health Research [NF-SI-0510-10187] Funding Source: researchfish
- MRC [MR/K000608/1, G0700718] Funding Source: UKRI
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Mitochondrial morphology, topology, and membrane interactions in skeletal muscle: a quantitative three-dimensional electron microscopy study. J Appl Physiol 114: 161-171, 2013. First published October 25, 2012; doi:10.1152/japplphysiol.01096.2012.-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 mu m(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.
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