Article Text

  1. S Kalkhoran1,
  2. AR Hall1,
  3. A Cole1,
  4. I White2,
  5. DM Yellon1,
  6. DJ Hausenloy1
  1. 1The Hatter Cardiovascular Institute, University College London, UK
  2. 2MRC Laboratory for Molecular Cell Biology, University College London, UK


Rationale Modulating mitochondrial morphology may alleviate cardiac disease by preventing mitochondrial dysfunction. Mitofusin-2 (Mfn2) tethers junctional sarcoplasmic reticulum (jSR) to mitochondria. Standard 2D electron microscopy (2D-EM) does not allow the accurate assessment of mitochondrial morphology and jSR in the adult heart. Here, we investigate whether 3D-EM tomography, which allows one to image the mitochondria and jSR in 3-dimensions, can provide a more objective and accurate assessment of these features.

Methodology Electron micrographs of serially sectioned samples, obtained from left ventricular tissue harvested from either 8 week-old wild-type (WT) and Mfn2−/− mice, were imaged using either standard 2D-EM or 3D-EM tomography. Specific regions containing juxtaposed mitochondria and jSR were aligned, segmented, and reconstructed in 3D using Amira V.5.

Results In 2D-EM the Mfn2−/− mitochondria appeared to be larger, whereas in 3D-EM tomography the mitochondria appeared to be either similar or smaller in size, when compared to WT. Measuring the distance between mitochondria and jSR using 2D-EM gave highly variable results. However, 3D-EM allowed one to reconstruct the space between the juxtaposed organelles in 3D allowing a more accurate measurement of this distance.

Conclusions Here, we show that 3D-EM tomography is superior to 2D-EM in the assessment of mitochondrial morphology and can be used to more accurately measure the distance between mitochondrial and jSR in the adult heart. 3D-EM tomography will enable one to accurately assess mitochondrial morphology in different cardiac diseases (acute IRI, heart failure, LVH) and in the presence of co-morbidities (diabetes, metabolic syndrome, age).

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