Cell models of arrhythmogenic cardiomyopathy: advances and opportunities

Abstract

Arrhythmogenic cardiomyopathy is a rare genetic disease that is mostly inherited as an autosomal dominant trait. It is associated predominantly with mutations in desmosomal genes and is characterized by the replacement of the ventricular myocardium with fibrous fatty deposits, arrhythmias and a high risk of sudden death. In vitro studies have contributed to our understanding of the pathogenic mechanisms underlying this disease, including its genetic determinants, as well as its cellular, signaling and molecular defects. Here, we review what is currently known about the pathogenesis of arrhythmogenic cardiomyopathy and focus on the in vitro models that have advanced our understanding of the disease. Finally, we assess the potential of established and innovative cell platforms for elucidating unknown aspects of this disease, and for screening new potential therapeutic agents. This appraisal of in vitro models of arrhythmogenic cardiomyopathy highlights the discoveries made about this disease and the uses of these models for future basic and therapeutic research.

Keywords: ACM; ARVC; Arrhythmogenic cardiomyopathy; Cell models; In vitro; Molecular mechanisms.

Fig. 1.

Pathogenic cardiac changes in ACM. (A,B) Representative images of key phenotypic features in human ACM. (A) Hematoxylin–eosin staining of the right ventricle (RV) in an ACM patient's heart shows fat deposits (white areas) and disarrayed cardiomyocyte architecture with fibro-fatty infiltrations (asterisk). (B) An electrocardiogram trace (12 leads, listed on the left-hand side, representing the electrical activity from electrodes on the body surface) of a typical RV arrhythmia, which commonly occurs in ACM patients. (C-E) Representative light microscopy images of ACM in vitro models and studies of fat accumulation and arrhythmias. (C) Oil Red O staining of isolated cardiac mesenchymal stromal cells (C-MSCs) from an ACM patient and control highlights the typical lipid accumulation seen in ACM. Lipid accumulation is measured by evaluation of red areas into the cell lipid droplets. (D) Depiction of murine HL-1 cells, which can be used to generate in vitro models for electrophysiological studies of the sodium channel Nav1.5 in ACM. (E) The main graph depicts, on the y-axis, the average peak of sodium current (I_Na) density [measured in picoamperes/picofarad (pA/pF)] and, on the x-axis, voltage max [V_m; measured in millivolt (mV)] in wild-type (WT) HL-1 cells (black trace), HL1 cells treated with PKP2-silencing construct (PKP2-KD; red trace) and HL-1 cells treated with a non-silencing construct (PKP2-φKD; blue trace). The corresponding dot plot, in the inset, shows that silencing PKP2 in HL-1 cells (PKP2-KD) leads to a statistically significant (**P<0.005) decrease in sodium current density (I_Na) (see main text for a discussion of the effect of PKP2 loss on sodium current). Adapted with permission from Cerrone et al., 2014. This image (E) is not published under the terms of the CC-BY licence of this article. Promotional and commercial use of the material in print, digital or mobile device format is prohibited without permission from the publisher Wolters Kluwer. Please contact healthpermissions@wolterskluwer.com for further information. Scale bars: 100 μm.

Fig. 2.

Cellular models used for in vitro studies of ACM. A schematic illustration of the cardiac and non-cardiac cell models used to study ACM. The figure shows information concerning: the species of origin (animal or human), the stage of cell maturity (adult or embryonic/stem cells), the type of studies performed to date (immunoassays for protein localization, pathway investigation and cellular electrophysiology) and the specific lipid accumulation processes involved (adipo- or lipogenesis). BMCs, buccal mucosa cells; COS, CV-1 in origin carrying the SV40 genetic material, derived from monkey kidney tissue; FAPs, fibro-adipocytes progenitors; HEK, human embryonic kidney 293 cells; hiPSC-d, human induced pluripotent stem cell-derived cardiomyocytes; HL-1, murine immortalized AT-1 atrial cardiomyocytes; MSCs, mesenchymal stromal cells; ?, not clear from the performed investigations.