A Micro-Engineered Heart Tissue Model of Desmin-related Cardiomyopathy Caused by Mutant αB Crystalin

Protein quality control (PQC) is essential for maintaining sarcomere integrity in cardiomyocytes. The R120G mutation in α Crystallin B chain (CRYAB) disrupts CRYAB's chaperone activity, leading to aggregation of CRYAB and its client proteins (including Desmin).This causes Desmin-related cardiomyopathy (DRM). Prior experimental systems for modeling DRM linked to CRYAB require massive overexpression of mutant CRYAB isoforms, raising questions about translational relevance. Here, we establish the first micro-engineered tissue model of CRYAB-linked DRM that uses genome-edited hiPSC together with isogenic controls, allowing us to study the impact of mutant CRYAB expressed at near endogenous levels. Within micro-engineered heart tissues (μHT), CRYAB R120G mutant hiPSC derived cardiomyocytes recapitulated key DRM hallmarks, including Desmin and CRYAB aggregation, contractile dysfunction, and increased vulnerability to PQC pathway inhibition. CRYAB-R120G mutant μHT also exhibited dysfunctional calcium-contraction coupling, which exacerbated contractile deficits at higher pacing frequencies. JAK1 inhibition with Itacitinib partially restored contractile function at higher pacing frequencies, suggesting JAK1 inhibition as a potential therapeutic strategy. By preserving human-specific structural and functional features, our μHT platform enables mechanistic characterization of proteotoxic cardiomyopathies and offers a scalable system for targeted drug screening.