Increases in plasma corin levels following experimental myocardial infarction reflect the severity of ischemic injury

Figures

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  Fig 1. A schematic diagram showing the detailed animal groups involved in this study. Experimental mice were randomly assigned into four groups, including Non-MI, MI-3 h, MI-24 h and MI-72 h. Non-surgical mice served as non-MI control [17] and were euthanized after echocardiography. Mice in MI groups were euthanized at 3 h, 24 h and 72 h post-MI respectively after echocardiography. Blood samples and organs were collected from all experimental animals to measure plasma corin, troponin, cardiac corin, ANP and BNP, and to do histologic examination.

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  Fig 2. Pathological features observed in AMI mouse model. (A) Representative images of H&E stained myocardium from the LV at baseline and at 3 h, 24 h and 72 h post-MI. (B) Plasma troponin T levels were measured by ELISA in non-MI group and at 3 h, 24 h and 72 h post-MI. (C) & (D) Dynamic changes of heart weight (HW), lung weight (LW) and body weight (BW) (C) and HW/BW % and LW/BW % (D). Scale bar = 100 μm. Differences between MI and non-MI groups were analyzed by one-way ANOVA. Data presented as mean ±SE of n = 7–9 mice per group. *P<0.05, **P<0.01, ***P<0.001 vs. non-MI control.

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  Fig 3. The changes in plasma and cardiac corin in early phase of AMI. (A) Plasma corin levels were measured by ELISA in non-MI group and at 3 h, 24 h and 72 h post-MI. (B) Corin cardiac transcript levels in infarct hearts assessed by qRT-PCR analysis in non-MI group and at the indicated time points post-MI. (C) Cardiac corin protein expression assessed by immunofluorescence (IF) staining with an anti-corin antibody. The total intensity of corin immuno-fluorescence (artificial units) and total myocardium area in each heart were measured in heart cross sections using Image-Pro Plus software, and the fluorescence intensity per myocardial area was calculated for each heart and expressed relative to average fluorescence intensity per myocardial area in control, non-MI mouse hearts. (D) Representative images of the same border zone on two serial heart sections of a MI heart from 24 h post-MI group, showing corin IF staining (left) and H&E staining (right) respectively. Scale bar = 100 μm. The lower corin expression area (LCA, or the area of decreased green fluorescence, left panel) in the heart was identical to the infarct area (IFA, eosinophilic staining area, right panel). The dotted line…

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  Fig 4. Spatial character of corin reduction in different regions of injured myocardium 24 hours post-MI. Corin protein expression in non-MI and MI hearts assessed by double immunofluorescence (IF) staining on heart coronary sections with corin antibody followed by labelling with anti-rabbit AlexaFluor® 488 (green), WGA-Rhodomine (red) and counterstaining with DAPI (blue). Representative image of normal left ventricle myocardium from non-MI hearts (row 1 & 2 panels), infarct core region (row 3 & 4 panels) and border zone (row 5 & 6 panels) as well as remote area (row 7 & 8 panels) in MI hearts at low and high magnification (top vs. bottom panels, bar = 100 μm). When compared to non-MI heart, corin expression in infarct core and border zone was significantly decreased, while corin expression was relatively preserved in remote area. In addition, the integrity of cell membrane in infarct core was completely lost suggesting necrotic death. Border zone was the transition area in which the cardiomyocytes with or without cell membrane integrity co-existed. Yellow arrows indicate three individual myocytes which show reduced corin expression (green channel) though the integrity of the cell…

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  Fig 5. Correlation between corin level, cardiac function and myocardial infarct size. Plasma corin levels were negatively correlated with EF (A) and FS (B). (C) Plasma corin levels were positively correlated with infarct size while (D) Corin cardiac transcript levels were negatively correlated with infarct size. Cardiac corin transcript levels were positively correlated with EF (E) and FS (F). All mice from 3 h, 24 h and 72 h post-MI are presented. P-values provided in each individual panel.

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  Fig 6. The changes in the ventricular transcripts of ANP and BNP in the early phase of AMI. (A & B) Relative cardiac ANP and BNP expressions assessed by qRT-PCR analysis. Transcripts are means of averages of triplicate measures. (C & D) Graphs showed a negative correlation (rs) between cardiac ANP/or BNP transcript levels and cardiac corin transcript levels. Data represent mean ±SE of n = 7–9 mice per group. *P<0.05, **P<0.01, ***P<0.001.