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Heterogeneity of Repolarization and Cell-Cell Variability of Cardiomyocyte Remodeling Within the Myocardial
Matthew Amoni1,2, Dylan Vermoortele3, Samaneh Ekhteraei-Tousi1
1Department of Cardiovascular Sciences, Experimental Cardiology (M.A., S.E.-T., R.D.P., G.G., M.Y., R.W., H.L.R., K.R.S.), KU Leuven, Belgium.
Insights
After myocardial infarction, the infarct border zone exhibits heterogeneous cardiomyocyte remodeling, leading to varied repolarization and increased arrhythmia risk. This remodeling is driven by altered gene expression and microenvironmental factors.
Area of Science:
- Cardiovascular Research
- Molecular Cardiology
- Cardiac Electrophysiology
Background:
- The infarct border zone (BZ) post-myocardial infarction is a key substrate for life-threatening arrhythmias due to fibrosis and abnormal repolarization.
- Understanding the heterogeneity of repolarization abnormalities and cardiomyocyte remodeling within the BZ is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the in vivo spatial heterogeneity of repolarization abnormalities within the infarct border zone after myocardial infarction.
- To determine if this heterogeneity correlates with heterogeneous cardiomyocyte remodeling at the cellular and molecular levels.
Main Methods:
- Myocardial infarction was induced in pigs, followed by assessment of remodeling and electroanatomical mapping to measure activation-recovery intervals (ARIs) in the BZ and remote regions.
- Cardiomyocytes were isolated for optical mapping of action potential duration (APD) and single-cell RNA sequencing to analyze gene expression, alongside assessing ventricular wall thickness.
Main Results:
- The BZ displayed longer and more spatially heterogeneous ARIs compared to remote regions, correlating with increased arrhythmia susceptibility.
- Heterogeneity of APD was significantly greater in BZ cardiomyocytes, correlating with in vivo ARI heterogeneity.
- Increased cell-cell gene expression heterogeneity in the BZ involved hypertrophy and ion channel genes, driven by stress-responsive transcription factors, with greater BZ left ventricular wall thickness heterogeneity.
Conclusions:
- Heterogeneous cardiomyocyte remodeling in the BZ, driven by altered gene expression and microenvironmental factors, results in heterogeneous repolarization.
- This cellular and molecular heterogeneity within the BZ directly translates to increased arrhythmia vulnerability in vivo.
Background:
After myocardial infarction, the infarct border zone (BZ) is the dominant source of life-threatening arrhythmias, where fibrosis and abnormal repolarization create a substrate for reentry. We examined whether repolarization abnormalities are heterogeneous within the BZ in vivo and could be related to heterogeneous cardiomyocyte remodeling.
Methods:
Myocardial infarction was induced in domestic pigs by 120-minute ischemia followed by reperfusion. After 1 month, remodeling was assessed by magnetic resonance imaging, and electroanatomical mapping was performed to determine the spatial distribution of activation-recovery intervals. Cardiomyocytes were isolated and tissue samples collected from the BZ and remote regions. Optical recording allowed assessment of action potential duration (di-8-ANEPPS, stimulation at 1 Hz, 37 °C) of large cardiomyocyte populations while gene expression in cardiomyocytes was determined by single nuclear RNA sequencing.
Results:
In vivo, activation-recovery intervals in the BZ tended to be longer than in remote with increased spatial heterogeneity evidenced by a greater local SD (3.5±1.3 ms versus remote: 2.0±0.5 ms, P=0.036, npigs=5). Increased activation-recovery interval heterogeneity correlated with enhanced arrhythmia susceptibility. Cellular population studies (ncells=635-862 cells per region) demonstrated greater heterogeneity of action potential duration in the BZ (SD, 105.9±17.0 ms versus remote: 73.9±8.6 ms; P=0.001; npigs=6), which correlated with heterogeneity of activation-recovery interval in vivo. Cell-cell gene expression heterogeneity in the BZ was evidenced by increased Euclidean distances between nuclei of the BZ (12.1 [9.2-15.0] versus 10.6 [7.5-11.6] in remote; P<0.0001). Differentially expressed genes characterizing BZ cardiomyocyte remodeling included hypertrophy-related and ion channel-related genes with high cell-cell variability of expression. These gene expression changes were driven by stress-responsive TFs (transcription factors). In addition, heterogeneity of left ventricular wall thickness was greater in the BZ than in remote.
Conclusions:
Heterogeneous cardiomyocyte remodeling in the BZ is driven by uniquely altered gene expression, related to heterogeneity in the local microenvironment, and translates to heterogeneous repolarization and arrhythmia vulnerability in vivo.
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