Mechanistic Insights into Desmoplakin Cardiomyopathy: Exercise, Biomechanics, and Gene Therapy - Desmoplakin cardiomyopathy (DSP-CM), an arrhythmogenic cardiomyopathy often affecting young adults, results from pathogenic loss-of-function variants in DSP, leading to impaired cardiac function, myocardial fibrosis, and sudden cardiac death. Fibrosis in DSP-CM localizes to the subepicardium, a region of high tensile stress. My preliminary data using both human heart tissue and human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) demonstrates that DSP haploinsufficiency, which leads to cell adhesion failure, is the primary pathogenic mechanism. However, the precise consequences of the interaction between DSP level and mechanical load, including with the hemodynamic stress imposed by exercise, remain poorly understood at the tissue level. This proposal aims to define the tissue-level pathology driven by mechanical stress in DSP haploinsufficiency and to test whether therapeutic restoration of DSP levels can prevent this pathology. The central hypothesis is that DSP haploinsufficiency causes cardiac tissue to be sensitized to injury, fibrosis, and arrhythmias specifically with mechanical stress, including high intensity exercise, and that restoring DSP levels can mitigate these effects in vivo. To investigate tissue-level pathology and treatment effects, this project will utilize fiber-aligned engineered heart tissues (fEHTs) and a novel Dsp mouse model that I developed to recapitulate patient-level haploinsufficiency and left ventricular fibrosis. Specific Aim 1 will determine the impact of mechanical load, including exercise, on fibrosis and arrhythmias in DSP haploinsufficient models, utilizing exercise protocols, functional assessments, and spatial transcriptomics in the Dsp mouse model, complemented by mechanistic studies in fEHTs. Specific Aim 2 will evaluate whether AAV-mediated gene therapy strategies can rescue DSP haploinsufficiency and prevent fibrosis in vivo. This will involve testing both CRISPR-based transcriptional activation (CRISPRa) to upregulate endogenous Dsp, building on my in vitro rescue data, and a split-intein approach to deliver the functionally sufficient DspII isoform. Both strategies will be assessed in our Dsp-CM mouse model for Dsp protein restoration, cardiac function, and fibrosis. This project will elucidate how mechanical stress impacts DSP-CM progression and provide crucial in vivo proof-of-concept for novel therapeutic strategies, addressing a critical unmet need. By addressing both disease mechanism and therapy, and providing training in advanced cardiac models, gene therapy, exercise modeling, and in vivo physiology, this K08 award will equip me to launch an independent research career focused on understanding and treating inherited cardiac diseases, potentially improving patient lives by informing exercise recommendations and paving the way for new therapeutics.
