Figure 6: Ultrastructural Morphology, Mitochondrial Volume Density, and Mitochondrial DNA Content in the Normal Donor Heart and in the Failing Human Heart Before and After LVAD Unloading

(A) Transmission electron microscopy photomicrographs depicting longitudinal rows of mitochondria located in parallel with the sarcomeres/contractile apparatus. The magnification is 15,000×, and the scale bar indicates the length of 2 μm. (B) Higher magnification of mitochondrial ultrastructure at 50,000×. Compared with the normal donor heart, the mitochondria at the pre-LVAD time point were smaller, had disorganized cristae, and had decreased matrix density, whereas the mitochondria after LVAD unloading consistently showed improvement in these specific morphological characteristics. The scale bar indicates the length of 1 μm. Mitochondrial volume density (C) and mitochondrial DNA (mtDNA) content (D) were lower in the failing human heart compared with the nonfailing donor heart. mtDNA levels and volume density remained unchanged after LVAD unloading. The number of large mitochondria in the normal control group were higher than the failing human heart (E). The average size of mitochondria improved slightly after LVAD unloading. *Significant difference in comparison to the normal donor heart; p < 0.05. +Significant difference in comparison to the pre-LVAD time point. Abbreviations as in Figure 2.