The H19 lncRNA, a highly abundant and conserved imprinted gene, has been implicated in many essential biological processes and diseases. However, the function of H19 in the heart remains unknown. In this study, we investigated the function and underlying mechanism of H19 in regulating cardiomyocyte hypertrophy. We first detected the expression of H19 and its encoded miR-675 in both normal and diseased hearts and verified their up-regulations in pathological cardiac hypertrophy and heart failure. Adenovirus-mediated expression and a siRNA-mediated silence of H19 showed that H19 overexpression reduced cell size both at baseline and in response to phenylephrine, whereas knock-down of H19 induced cardiomyocyte hypertrophy. Overexpression or knock-down of miR-675 in cardiomyocytes demonstrated that miR-675 also inhibited cardiomyocyte hypertrophy. Moreover, inhibition of miR-675 reversed the reduction of cardiomyocyte size in H19-overexpressing cardiomyocytes, while infection with an adenovirus carrying H19 fragment without pre-miR-675 (H19-Tru) or with mutant sequences of pre-miR-675 (H19-Mut) failed to reduce cardiomyocyte size, indicating that miR-675 mediated the inhibitory effect of H19 on cardiomyocyte hypertrophy. We also identified that CaMKIIδ was a direct target of miR-675 and partially mediated the effect of H19 on cardiomyocyte hypertrophy. Furthermore, in vivo silencing of miR-675 using a specific antagomir in a pressure overload-induced mouse model of heart failure increased cardiac CaMKIIδ expression and exacerbated cardiac hypertrophy. These findings reveal a novel function of H19-miR-675 axis targeting CaMKIIδ as a negative regulator of cardiac hypertrophy, suggesting its potential therapeutic role in cardiac diseases.

Basal autophagy is tightly regulated by transcriptional and epigenetic factors to maintain cellular homeostasis. Dysregulation of cardiac autophagy is associated with heart diseases, including cardiac hypertrophy, but the mechanism governing cardiac autophagy is rarely identified. To analyze the in vivo function of miR-199a in cardiac autophagy and cardiac hypertrophy, we generated cardiac-specific miR-199a transgenic mice and showed that overexpression of miR-199a was sufficient to inhibit cardiomyocyte autophagy and induce cardiac hypertrophy in vivo. miR-199a impaired cardiomyocyte autophagy in a cell-autonomous manner by targeting glycogen synthase kinase 3β (GSK3β)/mammalian target of rapamycin (mTOR) complex signaling. Overexpression of autophagy related gene 5 (Atg5) attenuated the hypertrophic effects of miR-199a overexpression on cardiomyocytes, and activation of autophagy using rapamycin was sufficient to restore cardiac autophagy and decrease cardiac hypertrophy in miR-199a transgenic mice. These results reveal a novel role of miR-199a as a key regulator of cardiac autophagy, suggesting that targeting miRNAs controlling autophagy as a potential therapeutic strategy for cardiac disease.

Pathological cardiac hypertrophy is the response of heart to various biomechanical and physiopathological stimuli, such as aging, myocardial ischemia and hypertension. However, a long-term exposure to the stress makes heart progress to heart failure. Autophagy is a dynamic self-degradative process necessary for the maintenance of cellular homeostasis. Accumulating evidence has revealed a tight link between cardiomyocyte autophagy and cardiac hypertrophy. Sophisticatedly regulated autophagy protects heart from various physiological and pathological stimuli by degradating and recycling of protein aggregates, lipid drops, or organelles. Here we review the recent progresses concerning the functions of autophagy in cardiac hypertrophy induced by various hypertrophic stimuli. Moreover, the therapeutic strategies targeting autophagy for cardiac hypertrophy will also be discussed.

The rapid development of genome editing technology has brought major breakthroughs in the fields of life science and medicine. In recent years, the clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing toolbox has been greatly expanded, not only with emerging CRISPR-associated protein (Cas) nucleases, but also novel applications through combination with diverse effectors. Recently, transposon-associated programmable RNA-guided genome editing systems have been uncovered, adding myriads of potential new tools to the genome editing toolbox. CRISPR-based genome editing technology has also revolutionized cardiovascular research. Here we first summarize the advances involving newly identified Cas orthologs, engineered variants and novel genome editing systems, and then discuss the applications of the CRISPR-Cas systems in precise genome editing, such as base editing and prime editing. We also highlight recent progress in cardiovascular research using CRISPR-based genome editing technologies, including the generation of genetically modified in vitro and animal models of cardiovascular diseases (CVD) as well as the applications in treating different types of CVD. Finally, the current limitations and future prospects of genome editing technologies are discussed.

Overexpression of either member of the miR-199 family, miR-199a-5p, or miR-199b-5p (hereinafter referred to as miR-199a or miR-199b) promotes pathological cardiac hypertrophy, but little is known about the role of endogenous miR-199 in cardiac development and disease. Our study aimed to determine the physiological function of the endogenous miR-199 family in cardiac homeostasis maintenance. We generated a sponge transgenic mouse model with a specific disruption of miR-199 in the heart. To our surprise, we found that knockdown of endogenous miR-199 caused physiological cardiac hypertrophy characterized by an increased heart weight and cardiomyocyte size, but with normal cardiac morphology and function. Furthermore, we also identified PGC1α as the target gene of the miR-199 family, and PGC1α was also increased in sponge transgenic mice. Inhibition of endogenous miR-199 led to physiological cardiac hypertrophy probably due to the up-regulation of PGC1α, uncovering a surprising role for endogenous miR-199 in the maintenance of cardiac homeostasis.

Rationale: Protein O-GlcNAcylation is dynamically regulated by 2 key enzymes, OGT (O-GlcNAc transferase) and OGA (O-GlcNAcase). Excessive protein O-GlcNAcylation contributes to dilated cardiomyopathy (DCM), but its regulatory mechanisms are not fully understood. The PRMT5 (protein arginine methyltransferase 5) is the major type II arginine methyltransferase, which plays critical physiological roles by symmetrically dimethylating various downstream targets including proteins involved in RNA splicing. However, its function in regulating protein O-GlcNAcylation and DCM is unexplored. Objective: To elucidate the physiological function of PRMT5 and the mechanism underlying its role in regulating cardiac O-GlcNAcylation and homeostasis. Methods and Results: Conditional gene knockout was used to study the in vivo function of PRMT5 in regulating cardiac homeostasis. An integrated analysis of transcriptomic and metabolomic profiles was performed to investigate the molecular mechanism. Adeno-associated virus 9-mediated gene delivery in the mouse was used to study the protein O-GlcNAcylation in Prmt5 deficiency-induced DCM. PRMT5 mRNA was decreased in human DCM hearts, and cardiomyocyte-specific Prmt5 deletion in mice resulted in DCM and heart failure. Transcriptomic and metabolomic profiling identified increased O-GlcNAcylation in the hearts of Prmt5 -knockout mice. Mechanistically, Prmt5 deletion suppressed OGA expression by inhibiting the transcription of Oga and triggering its aberrant splicing. Consistently, a positive correlation of PRMT5 and OGA was identified in human DCM hearts. Notably, gene therapy with adeno-associated virus 9 encoding the correctly spliced Oga normalized the cardiac protein O-GlcNAcylation levels and partially rescued the dilation and dysfunction of the hearts in Prmt5 -knockout mice. Conclusions: Our data demonstrate a novel function of PRMT5 in regulating protein O-GlcNAcylation to maintain cardiac homeostasis, suggesting that targeting the PRMT5-OGA axis could be a potential strategy for treating DCM.