Transcriptome and proteome mapping in the sheep atria reveal molecular features of atrial fibrillation progression

Aims Atrial fibrillation (AF) is a progressive cardiac arrhythmia that increases the risk of hospitalization and adverse cardiovascular events. There is a clear demand for more inclusive and large-scale approaches to understand the molecular drivers responsible for AF, as well as the fundamental mechanisms governing the transition from paroxysmal to persistent and permanent forms. In this study, we aimed to create a molecular map of AF and find the distinct molecular programs underlying cell type-specific atrial remodelling and AF progression. Methods and Results We used a sheep model of long-standing, tachypacing-induced AF, sampled right and left atrial tissue and isolated cardiomyocytes from control, intermediate (transition) and late time points during AF progression, and performed transcriptomic and proteome profiling. We have merged all these layers of information into a meaningful 3-component space in which we explored the genes and proteins detected and their common patterns of expression. Our data-driven analysis points at extracellular matrix remodelling, inflammation, ion channel, myofibril structure, mitochondrial complexes, chromatin remodelling, and genes related to neural function, as well as critical regulators of cell proliferation as hallmarks of AF progression. Most important, we prove that these changes occur at early transitional stages of the disease, but not at later stages, and that the left atrium undergoes significantly more profound changes than the right atrium in its expression program. The pattern of dynamic changes in gene and protein expression replicate the electrical and structural remodelling demonstrated previously in the sheep and in humans, and uncover novel mechanisms potentially relevant for disease treatment. Conclusions Transcriptomic and proteomic analysis of AF progression in a large animal model shows that significant changes occur at early stages, and that among others involve previously undescribed increase in mitochondria, changes to the chromatin of atrial cardiomyocytes, and genes related to neural function and cell proliferation. Translational Perspective We have generated a detailed molecular map of AF progression in a clinically relevant large-animal model. Such data would be very difficult if not impossible to obtain from patients. Our results provide a framework for a comprehensive molecular analysis of the disease, pointing to novel avenues of research toward identifying early events that can lead to therapeutically targets to prevent AF-induced atrial remodelling.