Myocarditis is clinically characterized by chest pain, arrhythmias, and heart failure, and treatment is often supportive. Mutations in DSP, a gene encoding the desmosomal protein
desmoplakin, have been increasingly implicated in myocarditis. To model DSP-associated myocarditis and assess the role of innate immunity, we generated engineered heart tissues
(EHTs) using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from patients with heterozygous DSP truncations (DSPtv) and a gene-edited homozygous deletion
cell line (DSP-/-). At baseline, DSP-/- EHTs displayed a transcriptomic signature of innate immune activation which was mirrored by cytokine release. Importantly, DSP-/- EHTs were
hypersensitive to Toll-like receptor (TLR) stimulation demonstrating more contractile dysfunction compared to isogenic controls. Relative to DSP-/- EHTs, heterozygous DSPtv EHTs had less functional impairment. DSPtv EHTs displayed heightened sensitivity to TLR stimulation, and when subjected to strain, DSPtv EHTs developed functional deficits indicating reduced
contractile reserve compared to healthy control. Colchicine or NFκB inhibitors improved strain-induced force deficits in DSPtv EHTs. Genomic correction of DSP p.R1951X using adenine
base editing reduced inflammatory biomarker release from EHTs. Thus, EHTs replicate electrical and contractile phenotypes seen in human myocarditis implicating cytokine release as
a key part of the myogenic susceptibility to inflammation. This heightened innate immune activation and sensitivity is a target for clinical intervention.