Developmental Differences in Myocardial Mitochondrial Reticulum Networks in the Offspring Exposed to Diabetic Pregnancy

Figure 1. The schematic representation of the experimental design, examining the developmental differences in the mitochondrial reticulum network in the heart.

Figure 2. Three-dimensional reconstruction of mitochondrial reticulum in the myocardium from a 4-month-old male rat. Nucleus (blue), PN mitochondria (warm colors), and IF mitochondria (cool colors) were traced in the SBF-SEM images obtained from the left ventricular septum of the myocardium. Purple color indicates mitochondria undergoing mitophagy. Scale bars: 1 µm.

Figure 3. Myocardial mitochondrial counts in control and diabetes-exposed male offspring. The number of perinuclear (PN) mitochondria per cluster were counted and averaged over 10 slices for two ROIs per myocardial section. The number of interfibrillar (IF) mitochondria within a standardized 10 × 10 µm grid were counted and averaged in similar manner. Bar graphs represent mean ± SEM; n = 3 animals/group. p values denote group difference at each timepoint by Student’s t-test.

Figure 4. Myocardial mitochondrial volume was significantly different in diabetes-exposed male offspring at different developmental time periods. Average volume of mitochondria from 10 slices for two ROIs per myocardial section was used for group comparisons. Bar graphs represent mean ± SEM; n = 3 animals/group. p values denote group differences at each timepoint by Student’s t-test.

Figure 5. Developmental differences in mitochondrial reticulum in terms of number and volume of mitochondria in control and in diabetes-exposed myocardium in male offspring over time. Local regression fitting by locally estimated scatterplot smoothing (LOESS) was used to compare a moving average over developmental timepoints. Each line represents a regression for either IF or PN, and shaded bands represent a 95% confident interval that the true regression line falls within. Wherever the shaded regions are not touching, there is a significant difference between the bands (p = 0.05) at the point on the x-axis.

Figure 6. Diabetes-exposure altered the development of myocardial mitochondrial reticulum compared to controls. LOESS analysis shows that both the PN and IF mitochondrial volume was significantly different in diabetes-exposed myocardium in male offspring at different developmental stages regardless of the mitochondrial counts. Each line represents a regression for either the control or diabetes-exposed group, and shaded bands represent a 95% confident interval that the true regression line falls within. Wherever the shaded regions are not touching, there is a significant difference between the bands (p = 0.05) at the point on the x-axis.

Figure 7. Three-dimensional reconstruction of SBF-SEM images of control and diabetes-exposed myocardium in male offspring at different developmental stages. Detailed 3D models of control and diabetes-exposed myocardium reveal that despite having higher number of IF mitochondria, their volume was significantly reduced over time. Blue color represents nucleus, warm colors represent PN mitochondria, and cool colors represent IF mitochondria. Purple color represents electron dense material that indicates mitophagy. Scale bars: 1 µm.