Mutations in desmoplakin (DSP) are a major cause of left ventricular arrhythmogenic cardiomyopathy (ACM), and are linked to sudden cardiac death and premature systolic heart failure. Intensive aerobic exercise training and pregnancy are associated with worse clinical outcomes for DSP mutation carriers. Accordingly, we hypothesized that there is a synergistic effect between DSP deficiency and higher preload in disease progression. We sought to evaluate this hypothesis using mechanically loaded engineered heart tissues (EHTs). EHTs were generated from wild type (WT) and homozygous DSP S299R mutant-induced pluripotent stem cell derived cardiomyocytes as one-dimensional in vitro models of myocardium. The S299R DSP mutation destabilizes the protein and results in near total DSP knock-out. EHTs were loaded into a device that causes gradual, controlled stretch of the EHTs over time (140% of their original length over 5 days) to mimic an extreme change cardiac preload. Unstretched EHTs of both genotypes were cultured for the same amount of time to serve as controls. All EHTs were collected after culture and subjected to biomechanical characterization. Unstretched groups showed no difference in peak isometric contractile force between WT and mutant EHTs. In contrast, peak isometric twitch force in the stretched DSP S299R EHTs was significantly reduced relative to stretched WT EHTs, suggesting a synergistic effect between DSP deficiency and higher preload over time. Fluorescence microscopy of phalloidin-labeled EHTs reveals stretch- and genotype-specific alterations in the organization and distribution of sarcomeres, offering a possible explanation for differences in contractile force following chronic stretch. These results highlight a novel connection between DSP deficiency, preload, and contractile deficits that may shed light on the clinical pathologies associated with desmoplakin mutations.
Li et al. (Sun,) studied this question.