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Single-cell sequencing reveals the cardio-protective role of overexpressing Cox7B in hypertrophic cardiomyopathy

ABSTRACT: Hypertrophic cardiomyopathy (HCM) is an important cause leading to heart failure. Preserving cardiac function particularly in cardiomyocytes (CMs) is essential for improving prognosis in HCM patients. Therefore, understanding single-cell transcriptome characteristics of CMs in HCM would be indispensable to investigate potential therapeutic targets. We applied single-cell tagged reverse transcription (STRT-seq) approach and obtained 338 CM transcriptomes. The human heart samples were collected from HCM patients who had extended septal myectomy and healthy donors. Our results revealed that in nonfailing HCM heart CMs could be categorized into three subsets: high energy synthesis cluster, high cellular metabolism cluster and intermediate cluster. The expression of mitochondrial and electron transport chain (ETC) was up-regulated in larger-sized CMs from high energy synthesis cluster. Of note, we found the expression of Cytochrome c oxidase subunit 7B (Cox7B), a subunit of Complex IV in ETC was positively correlated with CMs size. Further, after assessing Cox7B expression in HCM patients, we speculated that Cox7B was compensatory up-regulated at early-stage but down-regulated at end-stage of HCM. To test the hypothesis that Cox7B might play a cardioprotective role in the early-stage of HCM, we used adeno associated virus 9 (AAV9) to mediate the expression of Cox7B in pressure overload-induced mice. Mice in vivo data supported that knockdown of Cox7B would accelerate heart failure progression and Cox7B overexpression could restore partial cardiac function in hypertrophy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE227734 | GEO | 2024/02/07

REPOSITORIES: GEO

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Project description:Compelling evidence suggests that mitochondrial dysfunction contributes to the pathogenesis of heart failure, including defects in the substrate oxidation, and the electron transport chain (ETC) and oxidative phosphorylation (OXPHOS). However, whether such changes occur early in the development of heart failure, and are potentially involved in the pathologic events that lead to cardiac dysfunction is unknown. To address this question, we conducted transcriptomic/metabolomics profiling in hearts of mice with two progressive stages of pressure overload-induced cardiac hypetrophy: i) cardiac hypertrophy with preserved ventricular function achieved via transverse aortic constriction for 4 weeks (TAC) and ii) decompensated cardiac hypertrophy or heart failure (HF) caused by combining 4 wk TAC with a small apical myocardial infarction. Transcriptomic analyses revealed, as shown previously, downregulated expression of genes involved in mitochondrial fatty acid oxidation in both TAC and HF hearts compared to sham-operated control hearts. Surprisingly, however, there were very few changes in expression of genes involved in other mitochondrial energy transduction pathways, ETC, or OXPHOS. Metabolomic analyses demonstrated significant alterations in pathway metabolite levels in HF (but not in TAC), including elevations in acylcarnitines, a subset of amino acids, and the lactate/pyruvate ratio. In contrast, the majority of organic acids were lower than controls. This metabolite profile suggests “bottlenecks” in the carbon substrate input to the TCA cycle. This transcriptomic/metabolomic profile was markedly different from that of mice PGC-1a/b deficiency in which a global downregulation of genes involved in mitochondrial ETC and OXPHOS was noted. In addition, the transcriptomic/metabolomic signatures of HF differed markedly from that of the exercise-trained mouse heart. We conclude that in contrast to current dogma, alterations in mitochondrial metabolism that occur early in the development of heart failure reflect largely post-transcriptional mechanisms resulting in impedance to substrate flux into the TCA cycle, reflected by alterations in the metabolome. Microarray gene expression profiling was performed with bi-ventricle RNA isolated from (1) 3 month-old female C57Bl6/J mice with transverse aortic constriction (CH), vs sham-operated control (Sham-CH), (2) 3 month-old female C57Bl6/J mice with heart failure (HF), vs. sham-operated control (Sham-HF); (3) 2 month-old female C57Bl6/J mice with voluntary wheel training for 2 months (Run), vs. Sedentary control (Sed). Five biological replicates are included for each group.

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Single-cell sequencing reveals the cardio-protective role of overexpressing Cox7B in hypertrophic cardiomyopathy

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