The roles and mechanisms of epigenetic regulation in pathological myocardial remodeling

Developmental Regulation of circRNAs in Normal and Diseased Mammary Gland: A Focus on circRNA-miRNA Networks

Circular RNAs (circRNAs) have emerged as critical regulators in various biological processes including diseases. In the mammary gland (MG), which undergoes most of its development postnatally, circRNAs play pivotal roles in both physiological and pathological contexts. This review highlights the involvement of circRNAs during key developmental stages of the MG, with particular emphasis on lactation, where circRNA-miRNA networks significantly influence milk secretion and composition. CircRNAs exhibit stage-, breed- and species-specific expression patterns during lactation, which underscores their complexity. This intricate regulation also plays a significant role in pathological conditions of the MG, where dysregulated circRNA expression contributes to disease progression such as mastitis, early breast cancer (BC) stages, and epithelial-to-mesenchymal transition in BC (EMT). In mastitis, altered circRNA expression disrupts immune responses and compromises epithelial integrity. During early BC progression, circRNAs drive cell proliferation, while in EMT, they facilitate metastatic processes. By focusing on the circRNA-miRNA interactions underlying these processes, this review highlights their potential use as biomarkers for MG development, disease progression, and as therapeutic targets.

Emerging roles of noncoding RNAs in cardiovascular pathophysiology

This review comprehensively examines the diverse roles of noncoding RNAs (ncRNAs) in the pathogenesis and treatment of cardiovascular disease (CVD), focusing on microRNA (miRNA), long noncoding RNA (lncRNA), piwi-interacting RNA (piRNA), small-interfering RNA (siRNA), circular RNA (circRNA), and vesicle-associated RNAs. These ncRNAs are integral regulators of key cellular processes, including gene expression, inflammation, and fibrosis, and they hold great potential as both diagnostic biomarkers and therapeutic targets. The review highlights novel insights into how these RNA species, particularly miRNAs, lncRNAs, and piRNAs, contribute to various CVDs such as hypertension, atherosclerosis, and myocardial infarction. In addition, it explores the emerging role of extracellular vesicles (EVs) in intercellular communication and their therapeutic potential in cardiovascular health. The review underscores the need for continued research into ncRNAs and RNA-based therapies, with a focus on advancing delivery systems and expanding personalized medicine approaches to improve cardiovascular outcomes.

Epigenetic regulation of sex dimorphism in cardiovascular health

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality, affecting people of all races, ages, and sexes. Substantial sex dimorphism exists in the prevalence, manifestation, and outcomes of CVDs. Understanding the role of sex hormones as well as sex-hormone-independent epigenetic mechanisms could play a crucial role in developing effective and sex-specific cardiovascular therapeutics. Existing research highlights significant disparities in sex hormones, epigenetic regulators, and gene expression related to cardiac health, emphasizing the need for a nuanced understanding of these variations between men and women. Despite these differences, current treatment approaches for CVDs often lack sex-specific considerations. A pivotal shift toward personalized medicine, informed by comprehensive insights into sex-specific DNA methylation, histone modifications, and non-coding RNA dynamics, holds the potential to revolutionize CVD management. By understanding sex-specific epigenetic complexities, independent of sex hormone influence, future cardiovascular research can be tailored to achieve effective diagnostic and therapeutic interventions for both men and women. This review summarizes the current knowledge and gaps in epigenetic mechanisms and sex dimorphism implicated in CVDs.

Role of EZH2-mediated abnormal histone H3K27me3 methylation in pressure overload-induced cardiac remodeling in mice

OBJECTIVES

Cardiac remodeling is a critical pathological process leading to heart failure. Currently, there is a lack of specific and effective therapies targeting pathological cardiac remodeling. Epigenetics has been shown to play a regulatory role in pathological remodeling. This study aims to explore the impact of inhibiting histone methyltransferase enhancer of zeste homolog 2 (EZH2)-mediated abnormal histone 3 lysine 27 trimethylation (H3K27me3) methylation modification on the progression of pressure overload-induced cardiac remodeling in mice.

METHODS

Male Kunming mice (specific pathogen-free grade) were randomly divided into groups for 2 experimental parts. Thoracic aortic constriction (TAC) surgery was performed to establish a mouse model of pressure overload-induced cardiac remodeling. In part 1, mice were divided into Normal, Sham, TAC-4W (TAC 4 weeks post-surgery), and TAC-8W (TAC 8 weeks post-surgery) groups. In part 2, mice were divided into Normal, Sham, TAC-8W, TAC+Vehicle (Veh) (TAC with distilled water gavage), and TAC+tanshinone I (Tan I) (TAC with Tan I gavage) groups. Cardiac structure and function were assessed using echocardiography. Histological analysis, Western blotting, and wheat germ agglutinin (WGA) staining was used to evaluate myocardial tissue and cellular changes.

RESULTS

Gross examination revealed that the hearts of mice in the TAC-8W group were larger than those in the Sham group, and the hearts in the TAC+Tan I group were further enlarged compared to the TAC-8W group. Echocardiographic analysis showed that, compared to the Sham group, mice in the TAC-4W group exhibited significantly increased left ventricular anterior wall thickness (LVAWT), left ventricular posterior wall thickness (LVPWT), and left ventricular ejection fraction (LVEF), while left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD) were significantly decreased (all P<0.05). Compared to the TAC-4W group, the TAC-8W displayed LVAWT, LVPWT, and LVEF, along with increased LVEDD, LVESD, and left ventricular volume (LVV) (all P<0.05). Furthermore, compared to the TAC-8W group, the TAC+Tan I group demonstrated further reductions in decreased EZH2 and H3K27me3 expression and increased LVAWT, LVPWT, and LVEF, while LVEDD, LVESD, and LVV increased significantly (all P<0.05). Western blotting analysis showed that, compared to the Sham group, the expression levels of EZH2 and H3K27me3 in myocardial tissue were significantly reduced in the TAC-4W and TAC-8W groups, whereas β-MHC expression was significantly increased (all P<0.05). Compared to the TAC-8W group, the TAC+Tan I group exhibited further reductions in EZH2 and H3K27me3 expression levels, along with a significant increase in β-MHC expression (all P<0.05). WGA staining results showed that cardiomyocyte area in the TAC-8W group was significantly larger than that in the Sham group (P<0.05). Compared to the TAC-8W group, the TAC+Tan I group displayed an even greater increase in cardiomyocyte area (P<0.05). Additionally, the number of cardiomyocytes per unit area was significantly lower in the TAC-8W group compared to the Sham group (P<0.05), and this reduction was further exacerbated in the TAC+Tan I group compared to the TAC-8W group (P<0.05).

CONCLUSIONS

EZH2 inhibition-mediated reduction in H3K27me3 methylation promotes pressure overload-induced cardiac remodeling in mice. EZH2 may serve as a novel therapeutic target for the prevention and treatment of pathological cardiac remodeling.

Epigenetic Regulation of Fibroblasts and Crosstalk between Cardiomyocytes and Non-Myocyte Cells in Cardiac Fibrosis

Epigenetic mechanisms and cell crosstalk have been shown to play important roles in the initiation and progression of cardiac fibrosis. This review article aims to provide a thorough overview of the epigenetic mechanisms involved in fibroblast regulation. During fibrosis, fibroblast epigenetic regulation encompasses a multitude of mechanisms, including DNA methylation, histone acetylation and methylation, and chromatin remodeling. These mechanisms regulate the phenotype of fibroblasts and the extracellular matrix composition by modulating gene expression, thereby orchestrating the progression of cardiac fibrosis. Moreover, cardiac fibrosis disrupts normal cardiac function by imposing myocardial mechanical stress and compromising cardiac electrical conduction. This review article also delves into the intricate crosstalk between cardiomyocytes and non-cardiomyocytes in the heart. A comprehensive understanding of the mechanisms governing epigenetic regulation and cell crosstalk in cardiac fibrosis is critical for the development of effective therapeutic strategies. Further research is warranted to unravel the precise molecular mechanisms underpinning these processes and to identify potential therapeutic targets.