Prevention of heart failure with preserved ejection fraction (HFpEF): reexamining microRNA-21 inhibition in the era of oligonucleotide-based therapeutics

Heart failure with preserved ejection fraction (HFpEF) accounts for 50% of cases of heart failure, which is the most common cause of hospitalization in US patients over the age of 65. HFpEF pathogenesis is increasingly believed to be due to pathological hypertrophy and fibrosis of the myocardium that may be a result of systemic inflammation from comorbid conditions such as hypertension, diabetes mellitus, chronic obstructive pulmonary disease, anemia, chronic kidney disease and others. It is believed that oxidative stress triggers a process of pathological hypertrophy and fibrosis in cardiac endothelial cells, which leads to increased left ventricle filling pressures and, eventually, symptoms of heart failure. Numerous recent major clinical trials that have examined various therapies aimed at improving mortality in HFpEF have emerged empty-handed and thus the search for effective management strategies continues. Over the last several years, there have been many new developments in the field of antisense oligonucleotide-based therapeutics, which involves using noncoding nucleic acid particles such as microRNA and small interfering RNA to repress the expression of specific messenger RNA. In this article, we review the concept of using oligonucleotide-based therapeutics to prevent or treat HFpEF by targeting a specific microRNA that has been implicated in the pathogenesis of myocardial fibrosis and hypertrophy, microRNA-21 (miR-21). We review the various evidence that implicates miR-21 in the process of myocardial fibrosis and discuss recent attempts to use antimiR-21 compounds to prevent fibrosis. We also discuss proposed methods for screening patients at high risk for HFpEF for diastolic dysfunction in order to determine which patients.

MicroRNA-21 and Dicer are dispensable for hepatic stellate cell activation and the development of liver fibrosis

Fibrosis and cancer represent two major complications of chronic liver disease. MicroRNAs have been implicated in the development of fibrosis and cancer, thus constituting potential therapeutic targets. Here, we investigated the role of microRNA-21 (miR-21), a microRNA that has been implicated in the development of fibrosis in multiple organs and has also been suggested to act as an "oncomir." Accordingly, miR-21 was the microRNA that showed the strongest up-regulation in activated hepatic stellate cells (HSCs) in multiple models of fibrogenesis, with an 8-fold to 24-fold induction compared to quiescent HSCs. However, miR-21 antisense inhibition did not suppress the activation of murine or human HSCs in culture or in liver slices. Moreover, genetic deletion of miR-21 in two independently generated knockout mice or miR-21 antisense inhibition did not alter HSC activation or liver fibrosis in models of toxic and biliary liver injury. Despite a strong up-regulation of miR-21 in injury-associated hepatocellular carcinoma and in cholangiocarcinoma, miR-21 deletion or antisense inhibition did not reduce the development of liver tumors. As inhibition of the most up-regulated microRNA did not affect HSC activation, liver fibrosis, or fibrosis-associated liver cancer, we additionally tested the role of microRNAs in HSCs by HSC-specific Dicer deletion. Although Dicer deletion decreased microRNA expression in HSCs and altered the expression of select genes, it only exerted negligible effects on HSC activation and liver fibrosis.

CONCLUSION

Genetic and pharmacologic manipulation of miR-21 does not inhibit the development of liver fibrosis and liver cancer. Moreover, suppression of microRNA synthesis does not significantly affect HSC phenotype and activation. (Hepatology 2018;67:2414-2429).

MicroRNAs in the Stressed Heart: Sorting the Signal from the Noise

The short noncoding RNAs, known as microRNAs, are of undisputed importance in cellular signaling during differentiation and development, and during adaptive and maladaptive responses of adult tissues, including those that comprise the heart. Cardiac microRNAs are regulated by hemodynamic overload resulting from exercise or hypertension, in the response of surviving myocardium to myocardial infarction, and in response to environmental or systemic disruptions to homeostasis, such as those arising from diabetes. A large body of work has explored microRNA responses in both physiological and pathological contexts but there is still much to learn about their integrated actions on individual mRNAs and signaling pathways. This review will highlight key studies of microRNA regulation in cardiac stress and suggest possible approaches for more precise identification of microRNA targets, with a view to exploiting the resulting data for therapeutic purposes.

Extracellular matrix secretion by cardiac fibroblasts: role of microRNA-29b and microRNA-30c

RATIONALE

MicroRNAs (miRNAs), in particular miR-29b and miR-30c, have been implicated as important regulators of cardiac fibrosis.

OBJECTIVE

To perform a proteomics comparison of miRNA effects on extracellular matrix secretion by cardiac fibroblasts.

METHODS AND RESULTS

Mouse cardiac fibroblasts were transfected with pre-/anti-miR of miR-29b and miR-30c, and their conditioned medium was analyzed by mass spectrometry. miR-29b targeted a cadre of proteins involved in fibrosis, including multiple collagens, matrix metalloproteinases, and leukemia inhibitory factor, insulin-like growth factor 1, and pentraxin 3, 3 predicted targets of miR-29b. miR-29b also attenuated the cardiac fibroblast response to transforming growth factor-β. In contrast, miR-30c had little effect on extracellular matrix production but opposite effects regarding leukemia inhibitory factor and insulin-like growth factor 1. Both miRNAs indirectly affected cardiac myocytes. On transfection with pre-miR-29b, the conditioned medium of cardiac fibroblasts lost its ability to support adhesion of rat ventricular myocytes and led to a significant reduction of cardiac myocyte proteins (α-actinin, cardiac myosin-binding protein C, and cardiac troponin I). Similarly, cardiomyocytes derived from mouse embryonic stem cells atrophied under pre-miR-29 conditioned medium, whereas pre-miR-30c conditioned medium had a prohypertrophic effect. Levels of miR-29a, miR-29c, and miR-30c, but not miR-29b, were significantly reduced in a mouse model of pathological but not physiological hypertrophy. Treatment with antagomiRs to miR-29b induced excess fibrosis after aortic constriction without overt deterioration in cardiac function.

CONCLUSIONS

Our proteomic analysis revealed novel molecular targets of miRNAs that are linked to a fibrogenic cardiac phenotype. Such comprehensive screening methods are essential to define the concerted actions of miRNAs in cardiovascular disease.

A New Level of Complexity

The discovery of the regulatory role of noncoding RNAs, and micro (mi)RNAs in particular, has added a new layer of complexity to our understanding of cardiovascular development. miRNAs regulate and modulate various steps of cardiovascular morphogenesis, cell proliferation, differentiation, and phenotype modulation. miRNAs simultaneously regulate multiple targets, and many miRNAs can bind to the same target, allowing for a complex pattern of regulation of gene expression. miRNA families are continuously added during evolution paralleling the increased complexity of the cardiovascular system in vertebrates compared with invertebrates. Several lines of evidence suggest that the appearance of miRNAs is at least in part responsible for the formation of complex organ systems and stable regulatory mechanisms in vertebrates. We review the current understanding of miRNAs during cardiovascular development. Further progress in this area will help to decipher quantitative changes in gene expression that provide robustness to cellular phenotypes and regulatory options to diseases processes. miRNAs might also provide clues to better understand congenital heart defects, which are the most common birth defects in human newborns.