Size matters: Finding growth pathways that protect the heart

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions. Prolonged cardiovascular stress causes cardiomyocytes and non-myocardial cells to enter an activated state releasing numerous pro-hypertrophic, pro-fibrotic, and pro-inflammatory mediators such as vasoactive hormones, growth factors, and cytokines, i.e., commencing signaling events that collectively cause cardiac hypertrophy. Fibrotic remodeling is mediated by cardiac fibroblasts as the central players, but also endothelial cells and resident and infiltrating immune cells enhance these processes. Many of these hypertrophic mediators are now being integrated into computational models that provide system-level insights and will help to translate our knowledge into new pharmacological targets. This perspective article summarizes the last decades' advances in cardiac hypertrophy research and discusses the herein-involved complex myocardial microenvironment and signaling components.

A quantitative detection of Cardiotrophin-1 in chronic heart failure by chemiluminescence immunoassay

Background

Cardiotrophin‐1 (CT‐1) is a cytokine that could induce cardiomyocytes hypertrophy and dysfunction. Plasma CT‐1 might serve as a cardiac biomarker both in diagnosis, staging, and prognostic assessment of heart failure.

Methods

In this study, a one‐step paramagnetic particles‐based chemiluminescence immunoassay (MPs‐CILA) for rapid and sensitive detection of plasma CT‐1 was established. Plasma samples were directly incubated with biotin‐labeled anti‐CT‐1 antibody (bio‐Ab) and acridine ester labeled anti‐CT‐1 antibody (AE‐Ab) to form sandwiched complex. The sandwiched CT‐1 was then captured by streptavidin modified paramagnetic particles (MPs‐SA) for rapid separation and signal generation.

Results

The proposed MPs‐CLIA presents a laudable linear relationship ranging from 7.8 pg/mL to 200 ng/mL with a detection limit of 1.0 pg/mL. The recoveries of spiked human plasma samples at low (10pg/mL), medium (100 pg/mL), and high (800 pg/mL) levels of CT‐1 were 96%, 104%, and 110% respectively. The intra‐analysis coefficient variation (CVs) of the 3 samples was 8.92%, 6.69%, and 3.54%, respectively. And the inter‐analysis coefficient variation (CVs) was 9.25%, 10.9%, and 4.3%, respectively. These results strongly indicate high sensitivity, wide linear range, acceptable precision, and applicable reproducibility of the proposed method to detect plasma level of CT‐1. Finally, Plasma CT‐1 from 140 subjects with or without chronic heart failure was analyzed to assess the clinical application of MPs‐CILA.

Conclusions

Noteworthily, the MPs‐CLIA method is highly automated such that it is suitable for high‐throughput detection of CT‐1 in clinical inspection.

CITED4 Protects Against Adverse Remodeling in Response to Physiological and Pathological Stress

RATIONALE

Cardiac CITED4 (CBP/p300-interacting transactivators with E [glutamic acid]/D [aspartic acid]-rich-carboxylterminal domain4) is induced by exercise and is sufficient to cause physiological hypertrophy and mitigate adverse ventricular remodeling after ischemic injury. However, the role of endogenous CITED4 in response to physiological or pathological stress is unknown.

OBJECTIVE

To investigate the role of CITED4 in murine models of exercise and pressure overload.

METHODS AND RESULTS

We generated cardiomyocyte-specific CITED4 knockout mice (C4KO) and subjected them to an intensive swim exercise protocol as well as transverse aortic constriction (TAC). Echocardiography, Western blotting, qPCR, immunohistochemistry, immunofluorescence, and transcriptional profiling for mRNA and miRNA (microRNA) expression were performed. Cellular crosstalk was investigated in vitro. CITED4 deletion in cardiomyocytes did not affect baseline cardiac size or function in young adult mice. C4KO mice developed modest cardiac dysfunction and dilation in response to exercise. After TAC, C4KOs developed severe heart failure with left ventricular dilation, impaired cardiomyocyte growth accompanied by reduced mTOR (mammalian target of rapamycin) activity and maladaptive cardiac remodeling with increased apoptosis, autophagy, and impaired mitochondrial signaling. Interstitial fibrosis was markedly increased in C4KO hearts after TAC. RNAseq revealed induction of a profibrotic miRNA network. miR30d was decreased in C4KO hearts after TAC and mediated crosstalk between cardiomyocytes and fibroblasts to modulate fibrosis. miR30d inhibition was sufficient to increase cardiac dysfunction and fibrosis after TAC.

CONCLUSIONS

CITED4 protects against pathological cardiac remodeling by regulating mTOR activity and a network of miRNAs mediating cardiomyocyte to fibroblast crosstalk. Our findings highlight the importance of CITED4 in response to both physiological and pathological stimuli.