Multilayer control of cardiac electrophysiology by microRNAs

Exosomal Preconditioning of Human iPSC-Derived Cardiomyocytes Beneficially Alters Cardiac Electrophysiology and Micro RNA Expression

Experimental evidence, both in vitro and in vivo, has indicated cardioprotective effects of extracellular vesicles (EVs) derived from various cell types, including induced pluripotent stem cell-derived cardiomyocytes. The biological effects of EV secretion, particularly in the context of ischemia and cardiac electrophysiology, remain to be fully explored. Therefore, the goal of this study was to unveil the effects of exosome (EXO)-mediated cell-cell signaling during hypoxia by employing a simulated preconditioning approach on human-induced pluripotent stem cell-derived cardiomyocytes (hIPSC-CMs). Electrophysiological activity of hIPSC-CMs was measured using a multielectrode array (MEA) system. A total of 16 h of hypoxic stress drastically increased the beat period. Moreover, hIPSC-CMs preconditioned with EXOs displayed significantly longer beat periods compared with non-treated cells after 16 h of hypoxia (+15.7%, p < 0.05). Furthermore, preconditioning with hypoxic EXOs resulted in faster excitation-contraction (EC) coupling compared with non-treated hIPSC-CMs after 16 h of hypoxia (-25.3%, p < 0.05). Additionally, microRNA (miR) sequencing and gene target prediction analysis of the non-treated and pre-conditioned hIPSC-CMs identified 10 differentially regulated miRs and 44 gene targets. These results shed light on the intricate involvement of miRs, emphasizing gene targets associated with cell survival, contraction, apoptosis, reactive oxygen species (ROS) regulation, and ion channel modulation. Overall, this study demonstrates that EXOs secreted by hIPSC-CM during hypoxia beneficially alter electrophysiological properties in recipient cells exposed to hypoxic stress, which could play a crucial role in the development of targeted interventions to improve outcomes in ischemic heart conditions.

Up-regulated novel-miR-17 promotes hypothermic reperfusion arrhythmias by negatively targeting Gja1 and mediating activation of the PKC/c-Jun signaling pathway

BACKGROUND

Hypothermic ischemia-reperfusion arrhythmia is a common complication of cardiothoracic surgery under cardiopulmonary bypass, but few studies have focused on this type of arrhythmia. Our prior study discovered reduced myocardial Cx43 protein levels may be linked to hypothermic reperfusion arrhythmias. However, more detailed molecular mechanism research is required.

METHOD

The microRNA and mRNA expression levels in myocardial tissues were detected by real-time quantitative PCR (RT-qPCR). Besides, the occurrence of hypothermic reperfusion arrhythmias and changes in myocardial electrical conduction were assessed by electrocardiography and ventricular epicardial activation mapping. Furthermore, bioinformatics analysis, applying antagonists of miRNA, western blotting, immunohistochemistry, a dual luciferase assay, and pearson correlation analysis were performed to investigate the underlying molecular mechanisms.

RESULTS

The expression level of novel-miR-17 was up-regulated in hypothermic ischemia-reperfusion myocardial tissues. Inhibition of novel-miR-17 upregulation ameliorated cardiomyocyte edema, reduced apoptosis, increased myocardial electrical conduction velocity, and shortened the duration of reperfusion arrhythmias. Mechanistic studies showed that novel-miR-17 reduced the expression of Cx43 by directly targeting Gja1 while mediating the activation of the PKC/c-Jun signaling pathway.

CONCLUSION

Up-regulated novel-miR-17 is a newly discovered pro-arrhythmic microRNA that may serve as a potential therapeutic target and biomarker for hypothermic reperfusion arrhythmias.

MicroRNA-1 Deficiency Is a Primary Etiological Factor Disrupting Cardiac Contractility and Electrophysiological Homeostasis

BACKGROUND

MicroRNA-1 (miR1), encoded by the genes miR1-1 and miR1-2, is the most abundant microRNA in the heart and plays a critical role in heart development and physiology. Dysregulation of miR1 has been associated with various heart diseases, where a significant reduction (>75%) in miR1 expression has been observed in patient hearts with atrial fibrillation or acute myocardial infarction. However, it remains uncertain whether miR1-deficiency acts as a primary etiological factor of cardiac remodeling.

METHODS

miR1-1 or miR1-2 knockout mice were crossbred to produce 75%-miR1-knockdown (75%KD; miR1-1+/-:miR1-2-/- or miR1-1-/-:miR1-2+/-) mice. Cardiac pathology of 75%KD cardiomyocytes/hearts was investigated by ECG, patch clamping, optical mapping, transcriptomic, and proteomic assays.

RESULTS

In adult 75%KD hearts, the overall miR1 expression was reduced to ≈25% of the normal wild-type level. These adult 75%KD hearts displayed decreased ejection fraction and fractional shortening, prolonged QRS and QT intervals, and high susceptibility to arrhythmias. Adult 75%KD cardiomyocytes exhibited prolonged action potentials with impaired repolarization and excitation-contraction coupling. Comparatively, 75%KD cardiomyocytes showcased reduced Na+ current and transient outward potassium current, coupled with elevated L-type Ca2+ current, as opposed to wild-type cells. RNA sequencing and proteomics assays indicated negative regulation of cardiac muscle contraction and ion channel activities, along with a positive enrichment of smooth muscle contraction genes in 75%KD cardiomyocytes/hearts. miR1 deficiency led to dysregulation of a wide gene network, with miR1's RNA interference-direct targets influencing many indirectly regulated genes. Furthermore, after 6 weeks of bi-weekly intravenous tail-vein injection of miR1 mimics, the ejection fraction and fractional shortening of 75%KD hearts showed significant improvement but remained susceptible to arrhythmias.

CONCLUSIONS

miR1 deficiency acts as a primary etiological factor in inducing cardiac remodeling via disrupting heart regulatory homeostasis. Achieving stable and appropriate microRNA expression levels in the heart is critical for effective microRNA-based therapy in cardiovascular diseases.

Diversity of cells and signals in the cardiovascular system

This white paper is the outcome of the seventh UC Davis Cardiovascular Research Symposium on Systems Approach to Understanding Cardiovascular Disease and Arrhythmia. This biannual meeting aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2022 Symposium was 'Cell Diversity in the Cardiovascular System, cell-autonomous and cell-cell signalling'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies, and challenges in examining cell and signal diversity, co-ordination and interrelationships involved in cardiovascular function. This paper originates from the topics of formal presentations and informal discussions from the Symposium, which aimed to develop a holistic view of how the multiple cell types in the cardiovascular system integrate to influence cardiovascular function, disease progression and therapeutic strategies. The first section describes the major cell types (e.g. cardiomyocytes, vascular smooth muscle and endothelial cells, fibroblasts, neurons, immune cells, etc.) and the signals involved in cardiovascular function. The second section emphasizes the complexity at the subcellular, cellular and system levels in the context of cardiovascular development, ageing and disease. Finally, the third section surveys the technological innovations that allow the interrogation of this diversity and advancing our understanding of the integrated cardiovascular function and dysfunction.

miR-30a inhibits the osteogenic differentiation of the tibia-derived MSCs in congenital pseudarthrosis via targeting HOXD8

Background

Congenital pseudarthrosis of the tibia (CPT) is an uncommon congenital deformity and a special subtype of bone nonunion. The lower ability of osteogenic differentiation in CPT-derived mesenchymal stem cells (MSCs) could result in progression of CPT, and miR-30a could inhibit osteogenic differentiation. However, the role of miR-30a in CPT-derived MSCs remains unclear.

Methods

The osteogenic differentiation of CPT-derived MSCs treated with the miR-30a inhibitor was tested by Alizarin Red S staining and alkaline phosphatase (ALP) activity. The expression levels of protein and mRNA were assessed by Western blot or quantitative reverse transcription-polymerase chain reaction (RT-qPCR), respectively. The interplay between miR-30a and HOXD8 was investigated by a dual-luciferase reporter assay. Chromatin immunoprecipitation (ChIP) was conducted to assess the binding relationship between HOXD8 and RUNX2 promoter.

Results

CPT-derived MSCs showed a lower ability of osteogenic differentiation than normal MSCs. miR-30a increased in CPT-derived MSCs, and miR-30a downregulation promoted the osteogenic differentiation of CPT-derived MSCs. Meanwhile, HOXD8 is a direct target for miR-30a, and HOXD8 could transcriptionally activate RUNX2. In addition, miR-30a could inhibit the osteogenic differentiation of CPT-derived MSCs by negatively regulating HOXD8.

Conclusion

miR-30a inhibits the osteogenic differentiation of CPT-derived MSCs by targeting HOXD8. Thus, this study might supply a novel strategy against CPT.

MicroRNA expression profiling of endocrine sensitive and resistant breast cancer cell lines

Background

Methods

Results

Conclusions

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Around 50–60% of microRNAs were significantly differentially expressed between ER- and ER + breast cancer cell lines.

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Transfection of miR-200c-3p mimic into ER -ve cells induced MET and reduced cell motility.

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Transfecting of miR-449a inhibitor into ER -ve cells reduced cell invasion but did not induce EMT.