HIPSC model reveals M1 macrophages cause atrial arrhythmia correlated to electrophysiological remodelling of atrial cardiomyocytes in 2D and 3D engineered heart tissue

Abstract Atrial fibrillation (AF) is the most common sustained arrhythmia with an estimated prevalence of 1.5–2%. Current treatments lack effectiveness and do not prevent recurrence. Inflammation is reported in AF patients, however, a causal connection remains elusive. In this study, we investigated the arrhythmic effects of pro-inflammatory macrophages (M1) on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes (aCM), to better understand their role in AF. Macrophages are known to play a role in cardiac electrophysiology, but their role in arrhythmia is unclear. Three healthy hiPSC lines were differentiated to aCM and M1. Multi-electrode array recordings of isogenic, 2D cocultures of M1 and aCM showed a significant increase in beat rate irregularity compared to control conditions (P<0.001). Furthermore, spike amplitude of aCM and M1 cocultures was significantly decreased (P<0.001). Arrhythmias occurred only after activation of macrophages in the coculture. Addition of anti-inflammatory glucocorticoids significantly reduced beat irregularity in aCM and M1 cocultures compared to vehicle (1.9-fold decrease for Hydrocortisone, P<0.005) further supporting macrophage mediated inflammation to be the cause of the arrhythmia. RNA sequencing of aCM and M1 cocultures revealed aberrant expression of arrhythmia associated cardiac sodium and atrial potassium ion channels (SCN5A, KCNA5). Normal expression was restored through hydrocortisone addition. In addition, inflammation-induced arrhythmia was observed in 3D engineered heart tissues containing hiPSC derived aCM, M1 and cardiac fibroblasts. Tissues showed a significant increase in beating irregularity (P<0.005) compared to controls and had a significant, median reduction (>30%) of contraction amplitude (P<0.05). Our findings suggest a causal relationship between M1 and the occurrence of atrial arrhythmia. The reduction of arrhythmia using glucocorticoids correlates to clinical observations, that show their use being linked to reduced post operative AF burden. These results strongly support the relevance of the proposed hiPSC coculture model and elucidate a new potential AF mechanism.