Noncanonical WNT Activation in Human Right Ventricular Heart Failure

Wnt signaling in cardiac development and heart diseases

The Wnt signaling pathway is a fundamental cellular communication system with extensive implications in various organs including the heart. In cardiac homeostasis, it governs essential processes like cellular proliferation, differentiation, and apoptosis, ensuring the heart's structural and functional integrity from embryonic stages and throughout life. Both canonical and non-canonical Wnt signaling pathways play a critical role during embryonic heart development in a region- and stage-specific manner. Canonical Wnt signaling also plays a significant role in heart diseases such as myocardial infarction and heart failure. However, the role of non-canonical Wnt signaling in heart diseases has not been fully elucidated. Wnt5a is a major ligand that activates non-canonical Wnt pathway, and recent studies start to clarify the role of the Wnt5a signaling axis in cardiac health and disease. In this review, we will briefly summarize the previous findings on the role of Wnt signaling pathways in heart development and diseases, and then focus on the role of Wnt5a signaling in heart failure progression. The multifaceted roles of the Wnt signaling pathway highlight its therapeutic potential for various types of heart diseases.

Molecular mechanisms and targets of right ventricular fibrosis in pulmonary hypertension

Right ventricular fibrosis is a stress response, predominantly mediated by cardiac fibroblasts. This cell population is sensitive to increased levels of pro-inflammatory cytokines, pro-fibrotic growth factors and mechanical stimulation. Activation of fibroblasts results in the induction of various molecular signaling pathways, most notably the mitogen-activated protein kinase cassettes, leading to increased synthesis and remodeling of the extracellular matrix. While fibrosis confers structural protection in response to damage induced by ischemia or (pressure and volume) overload, it simultaneously contributes to increased myocardial stiffness and right ventricular dysfunction. Here, we review state-of-the-art knowledge of the development of right ventricular fibrosis in response to pressure overload and provide an overview of all published preclinical and clinical studies in which right ventricular fibrosis was targeted to improve cardiac function.

Wnt Signaling in Heart Development and Regeneration

PURPOSE OF REVIEW

Cardiovascular diseases are the leading cause of death worldwide, largely due to the limited regenerative capacity of the adult human heart. In contrast, teleost zebrafish hearts possess natural regeneration capacity by proliferation of pre-existing cardiomyocytes after injury. Hearts of mice can regenerate if injured in a few days after birth, which coincides with the transient capacity for cardiomyocyte proliferation. This review tends to elaborate the roles and mechanisms of Wnt/β-catenin signaling in heart development and regeneration in mammals and non-mammalian vertebrates.

RECENT FINDINGS

Studies in zebrafish, mice, and human embryonic stem cells demonstrate the binary effect for Wnt/β-catenin signaling during heart development. Both Wnts and Wnt antagonists are induced in multiple cell types during cardiac development and injury repair. In this review, we summarize composites of the Wnt signaling pathway and their different action routes, followed by the discussion of their involvements in cardiac specification, proliferation, and patterning. We provide overviews about canonical and non-canonical Wnt activity during heart homeostasis, remodeling, and regeneration. Wnt/β-catenin signaling exhibits biphasic and antagonistic effects on cardiac specification and differentiation depending on the stage of embryogenesis. Inhibition of Wnt signaling is beneficial for cardiac wound healing and functional recovery after injury. Understanding of the roles and mechanisms of Wnt signaling pathway in injured animal hearts will contribute to the development of potential therapeutics for human diseased hearts.

Advances in Cardiac Development and Regeneration Using Zebrafish as a Model System for High-Throughput Research

Heart disease is the leading cause of death in the United States and worldwide. Understanding the molecular mechanisms of cardiac development and regeneration will improve diagnostic and therapeutic interventions against heart disease. In this direction, zebrafish is an excellent model because several processes of zebrafish heart development are largely conserved in humans, and zebrafish has several advantages as a model organism. Zebrafish transcriptomic profiles undergo alterations during different stages of cardiac development and regeneration which are revealed by RNA-sequencing. ChIP-sequencing has detected genome-wide occupancy of histone post-translational modifications that epigenetically regulate gene expression and identified a locus with enhancer-like characteristics. ATAC-sequencing has identified active enhancers in cardiac progenitor cells during early developmental stages which overlap with occupancy of histone modifications of active transcription as determined by ChIP-sequencing. CRISPR-mediated editing of the zebrafish genome shows how chromatin modifiers and DNA-binding proteins regulate heart development, in association with crucial signaling pathways. Hence, more studies in this direction are essential to improve human health because they answer fundamental questions on cardiac development and regeneration, their differences, and why zebrafish hearts regenerate upon injury, unlike humans. This review focuses on some of the latest studies using state-of-the-art technology enabled by the elegant yet simple zebrafish.

The Cell Surface Receptors Ror1/2 Control Cardiac Myofibroblast Differentiation

Background A hallmark of heart failure is cardiac fibrosis, which results from the injury-induced differentiation response of resident fibroblasts to myofibroblasts that deposit extracellular matrix. During myofibroblast differentiation, fibroblasts progress through polarization stages of early proinflammation, intermediate proliferation, and late maturation, but the regulators of this progression are poorly understood. Planar cell polarity receptors, receptor tyrosine kinase-like orphan receptor 1 and 2 (Ror1/2), can function to promote cell differentiation and transformation. In this study, we investigated the role of the Ror1/2 in a model of heart failure with emphasis on myofibroblast differentiation. Methods and Results The role of Ror1/2 during cardiac myofibroblast differentiation was studied in cell culture models of primary murine cardiac fibroblast activation and in knockout mouse models that underwent transverse aortic constriction surgery to induce cardiac injury by pressure overload. Expression of Ror1 and Ror2 were robustly and exclusively induced in fibroblasts in hearts after transverse aortic constriction surgery, and both were rapidly upregulated after early activation of primary murine cardiac fibroblasts in culture. Cultured fibroblasts isolated from Ror1/2 knockout mice displayed a proinflammatory phenotype indicative of impaired myofibroblast differentiation. Although the combined ablation of Ror1/2 in mice did not result in a detectable baseline phenotype, transverse aortic constriction surgery led to the death of all mice by day 6 that was associated with myocardial hyperinflammation and vascular leakage. Conclusions Together, these results show that Ror1/2 are essential for the progression of myofibroblast differentiation and for the adaptive remodeling of the heart in response to pressure overload.