Abstract Body (Do not enter title and authors here): Background
Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a-galactosidase deficiency, resulting in multi-organ accumulation of sphingolipid, namely globotriaosylceramide (Gb3). Gb3 accumulation triggers left ventricular hypertrophy, fibrosis, and inflammation, forming an environment for arrhythmia and sudden death, a common cause of FD mortality. Atrial fibrillation is common in FD and contributes to the high burden of stroke, yet the cellular mechanisms accounting for this are unknown. To address this, we conducted signal-averaged electrocardiography (ECG) analysis from a large cohort of adults with FD at varying stages of cardiomyopathy. Findings were compared with a novel human atrial model of FD, developed using gene-edited stem-cell derived atrial cardiomyocytes, exploring their molecular and functional properties.
Methods
In 115 adults with FD, staged according to degree of cardiomyopathy, ECG P-wave characteristics were compared with non-FD age/sex-matched controls. Induced pluripotent stem cells were then genome-edited using CRISPR-Cas9 to carry the GLA p. N215S variant, the most common cardiac variant of FD in the UK, and differentiated into atrial cardiomyocytes (iPSC-CMs). Contraction, calcium handling and single-cell electrophysiology experiments were conducted to explore proarrhythmic mechanisms.
Results
ECG analysis demonstrated P-wave duration and PQ interval shortening in FD adults with no cardiomyopathy compared with non-FD controls, which prolonged with cardiomyopathy stage. FD patients exhibited atrial dilation, high incidence of premature atrial contractions and increased risk of AF. In our cellular model, GLA p. N215S iPSC-CMs were deficient in a-Gal A and exhibited Gb3 accumulation. GLA p. N215S iPSC-CMs demonstrated a more positive diastolic membrane potential, a faster action potential upstroke velocity, a greater burden of delayed afterdepolarizations, greater contraction force, slower beat rate and significant dysfunction in calcium handling compared to WT iPSC-CMs. The identified ECG changes may be partly explained by our observed cellular changes.
Conclusions
These findings enhance our understanding of atrial myopathy in FD by providing novel insights into underpinning mechanisms for atrial arrhythmia as well as rationale for early identified P-wave changes in FD. Mechanisms identified in this study may be targeted in future research to develop therapeutic strategies to reduce the atrial arrhythmic burden in FD.