blister and Cardiomegaly

Ex-vivo simple models are powered tools to study cardiac hypertrophy. It is possible to control the activation of critical genes and thus test the effects of drug therapies before the in vivo tests. A zebrafish cardiac hypertrophy developed by 500 μM phenylephrine (PE) treatment in ex vivo culture has been demonstrated to activate the essential expression of the embryonal genes. These genes are the same as those described in several previous pieces of research on hypertrophic pathology in humans. The efficacy of the chemical drug Blebbistatin (BL) on hypertrophy induced ex vivo cultured hearts is studied in this research. BL can inhibit the myosins and the calcium wave in counteracting the hypertrophy status caused by PE. Samples treated with PE, BL and PE simultaneously, or pre/post-treatment with BL, have been analysed for the embryonal gene activation concerning the hypertrophy status. The qRTPCR has shown an inhibitory effect of BL treatments on the microRNAs downregulation with the consequent low expression of essential embryonal genes. In particular, BL seems to be effective in blocking the hyperplasia of the epicardium but less effective in myocardium hypertrophy. The model can make it possible to obtain knowledge on the transduction pathways activated by BL and investigate the potential use of this drug in treating cardiac hypertrophy in humans.

Topics: Animals; Cardiomegaly; Heterocyclic Compounds, 4 or More Rings; Humans; Pericardium; Phenylephrine; Zebrafish

Left ventricular (LV) hypertrophy is often present in patients with diastolic heart failure. However, stiffness of hypertrophied cardiomyocytes in the transverse direction has not been fully elucidated. The aim of this study was to assess passive cardiomyocyte stiffness of hypertrophied hearts in the transverse direction and the influence of actin-myosin cross-bridge formation on the stiffness.. Wistar rats received a vehicle (control) or isoproterenol (ISO) subcutaneously. After 7 days, compared with the controls, ISO administration had significantly increased heart weight and LV wall thickness and had decreased peak early annular relaxation velocity (e') assessed by echocardiography. Elastic modulus of living cardiomyocytes in the transverse direction assessed by an atomic force microscope was significantly higher in the ISO group than in controls. We added butanedione monoxime (BDM), an inhibitor of actin-myosin interaction, and blebbistatin, a specific myosin II inhibitor, to the medium. BDM and blebbistatin significantly reduced the elastic modulus of cardiomyocytes in the ISO group. X-ray diffraction analysis showed that the reflection intensity ratio (I((1,0))/I((1,1))) at diastole was not different before and after treatment with BDM, which induces complete relaxation, in control hearts, but that I((1,0))/I((1,1)) was significantly increased after BDM treatment in the ISO group, indicating residual cross-bridge formation in hypertrophied hearts.. Passive cardiomyocyte stiffness in the transverse direction is increased in hearts with ISO-induced hypertrophy and this is caused by residual actin-myosin cross-bridge formation. 

Topics: Actins; Adrenergic beta-Agonists; Animals; Cardiomegaly; Cells, Cultured; Diacetyl; Disease Models, Animal; Elasticity; Enzyme Inhibitors; Heterocyclic Compounds, 4 or More Rings; Hypertrophy, Left Ventricular; Isoproterenol; Male; Microscopy, Atomic Force; Myocytes, Cardiac; Myosins; Organ Size; Papillary Muscles; Radiography; Rats; Rats, Wistar; Ultrasonography