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. 2017 Feb 9;2(3):e89676. doi: 10.1172/jci.insight.89676

Figure 3. Mitochondrial density and structure in mouse heart after hyperoxia.

Figure 3

(A) Photomicrographs of immunofluorescence staining of citrate synthase (CS, green) in the hearts. Control WT/Cre heart shows normal mitochondrial labeling with CS in the cardiomyocytes; WT/Cre heart 8d after hyperoxia shows increased CS labeling and mitochondrial fluorescence intensity; HO-1(CM)–/– mouse heart kept on air only shows modest decreases in mitochondrial density; HO-1(CM)–/– mouse hearts 8d after hyperoxia show decreased CS labeling and loss of intensity of mitochondrial fluorescence, suggesting that hyperoxia had caused persistent mitochondrial damage and cell degeneration in HO-1 deficiency. Original magnification, 200×; scale bar = 100 μm. (B) By Western blotting, mitochondrial CS and Tfam expression were significantly increased 8d after hyperoxia in WT/Cre mice but not in HO-1(CM)–/– mice (mean ± SEM; horizontal bars represent mean values.*P < 0.05 for pre- vs. posthyperoxia; n = 6 per group). (C) Electron microscopic findings of myocardial ultrastructure. Electron photomicrographs of cardiomyocytes of control WT/Cre mice showing linear myofibril arrangement and normal mitochondria; WT/Cre mouse exposed to hyperoxia showing enhanced autophagy, and arrows indicating mitophagosomes; electron micrograph from HO-1(CM)–/– mouse showing dilated intramembranous spaces (long arrows); HO-1(CM)–/– after hyperoxia have severe injury, including disoriented myofilaments and aggregates of enlarged mitochondria (M). The images reveal swollen and disorganized mitochondria with abnormal cristae structure (short arrow) and fragmented mitochondria (long arrow), suggesting poor respiratory capacity (n = 6/group). Note lack of mitophagosomes. Original magnification, 12,000×; scale bar = 1 μm. (D) Drp1 mRNA expression in hearts determined by qPCR. (E) Opa1 mRNA expression in hearts determined by qPCR. Values normalized to 18S levels (mean ± SEM; horizontal bars represent mean values.*P < 0.05 for pre- vs. posthyperoxia; n = 6/group; 2-way ANOVA).