Cardiac Characterization of sgca-Null Mice Using High Resolution Echocardiography

Identification of Genetic Variants Associated with Severe Myocardial Bridging through Whole-Exome Sequencing

Myocardial bridging (MB) is a congenital coronary artery anomaly and an important cause of angina. The genetic basis of MB is currently unknown. This study used a whole-exome sequencing technique and analyzed genotypic differences. Eight coronary angiography-confirmed cases of severe MB and eight age- and sex-matched control patients were investigated. In total, 139 rare variants that are potentially pathogenic for severe MB were identified in 132 genes. Genes with multiple rare variants or co-predicted by ClinVar and CADD/REVEL for severe MB were collected, from which heart-specific genes were selected under the guidance of tissue expression levels. Functional annotation indicated significant genetic associations with abnormal skeletal muscle mass, cardiomyopathies, and transmembrane ion channels. Candidate genes were reviewed regarding the functions and locations of each individual gene product. Among the gene candidates for severe MB, rare variants in DMD, SGCA, and TTN were determined to be the most crucial. The results suggest that altered anchoring proteins on the cell membrane and intracellular sarcomere unit of cardiomyocytes play a role in the development of the missed trajectory of coronary vessels. Additional studies are required to support the diagnostic application of cardiac sarcoglycan and dystroglycan complexes in patients with severe MB.

miR-155 regulates high glucose-induced cardiac fibrosis via the TGF-β signaling pathway

Cardiac fibrosis, as a pathological process, plays an important role in various cardiac diseases. microRNA-155 (miR-155) is one of the most important miRNAs, and previous studies have shown that it is a regulatory factor in various fibrotic diseases. However, the mechanism by which miR-155 affects myocardial fibrosis remains unclear. In this study, we aim to establish the biological function of miR-155 in myocardial fibrosis induced by diabetes in mice. We used normal C57BL/6 wild type (WT) and miR-155 knockout (KO) mice to establish the diabetic model by intraperitoneal injection of streptozotocin, and we utilized echocardiography to evaluate the cardiac function at 30 and 60 days post-modeling. Hematoxylin-eosin (HE) and sirius-red (SR) staining were used to evaluate the degree of myocardial lesions. Furthermore, we extracted cardiac fibroblasts (CFs) from the WT mice and transfected them with miR-155 inhibitors, mimics and negative control siRNAs to analyze the specific mechanism involved in the development of myocardial fibrosis. The results showed that miR-155 deficiency could prevent cardiac fibrosis induced by diabetes in mice and also that attenuated collagen synthesis is induced by high glucose (HG) in CFs. We found that miR-155 regulated cardiac fibrosis via the TGF-β1-Smad 2 signaling pathway. These findings suggest that miR-155 may be a therapeutic target for preventing cardiac fibrosis induced by diabetes.

A comparative study of the characterization of miR-155 in knockout mice

miR-155 is one of the most important miRNAs and plays a very important role in numerous biological processes. However, few studies have characterized this miRNA in mice under normal physiological conditions. We aimed to characterize miR-155 in vivo by using a comparative analysis. In our study, we compared miR-155 knockout (KO) mice with C57BL/6 wild type (WT) mice in order to characterize miR-155 in mice under normal physiological conditions using many evaluation methods, including a reproductive performance analysis, growth curve, ultrasonic estimation, haematological examination, and histopathological analysis. These analyses showed no significant differences between groups in the main evaluation indices. The growth and development were nearly normal for all mice and did not differ between the control and model groups. Using a comparative analysis and a summary of related studies published in recent years, we found that miR-155 was not essential for normal physiological processes in 8-week-old mice. miR-155 deficiency did not affect the development and growth of naturally ageing mice during the 42 days after birth. Thus, studying the complex biological functions of miR-155 requires the further use of KO mouse models.