A new approach methodology for studying intrinsic ventricular arrhythmias in Fabry disease

Sudden cardiac death is a common but poorly understood cause of mortality in Fabry disease (FD). We investigated the arrhythmogenic mechanisms using a new approach methodology model of FD. This model employed optical mapping of membrane potentials and calcium transient (CaT) with adenovirus-mediated replacement of GLA (advGLA) in stem cell-derived ventricular cardiomyocytes (VCMs) of WT and FD origin.

α-Galactosidase A (GLA) null and wild-type (WT; iPS-DF19-9-11T) stem cells were differentiated into VCMs using a GiWi protocol, selected using MACS, and matured on MatrixPlus-coated 96- or 6-well plates for 7 days. GLA-null, wild-type, and adenoviral-transfected GLA ventricular cardiomyocytes were then subjected to optical mapping to measure membrane potentials using Fluovolt and calcium transients using Calbryte 520AM. In addition, cells underwent poly(A)-enriched RNA sequencing.

Fabry disease-derived matured cardiomyocyte syncytia presented a wide array of arrhythmias, including tachyarrhythmias, early after depolarizations, quiescence, and beat irregularity, compared with wild-type cardiomyocytes. Furthermore, optical mapping of intracellular calcium transients indicated that GLA-null ventricular cardiomyocytes presented an altered frequency of intracellular calcium release, prolonged calcium transient duration at 80% return to baseline, increased calcium transient triangulation, decreased calcium fluorescence upstroke, and higher baseline calcium fluorescence and amplitude relative to wild-type cardiomyocytes. Furthermore, in response to isoproterenol, the relative change in contraction frequency was higher in GLA-null cardiomyocytes compared with wild-type ventricular cardiomyocytes, whereas the change in baseline fluorescence was lower. Transcriptomic analysis indicated that several genes encoding sodium channels subunits (five genes), potassium channel subunits (29 genes), and calcium channels (nine genes) were differentially expressed between GLA-null and wild-type ventricular cardiomyocytes. Adenovirus-mediated rescue of GLA expression (advGLA) did not reduce the frequency of arrhythmias. In addition, treatment of GLA-null cardiomyocytes with advGLA equalized the expression of sodium channel genes (eight genes), potassium channel genes (32 genes), and calcium channel genes (12 genes) relative to wild-type cardiomyocytes.

We developed a new approach methodology for Fabry disease-associated arrhythmias using hiPSC-VCMs, which are characterized by a high frequency of arrhythmias associated with widespread dysregulation of ion channel expression. GLA overexpression was unable to restore appropriate ion channel expression and eliminate arrhythmias.