Transcriptome and Proteome Mapping in the Sheep Atria Reveal Molecular Features of Atrial Fibrillation Progression

Atrial fibrillation (AF) is often 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. We aimed to create a molecular map of AF and find the distinct genetic programs underlying cell type-specific atrial remodeling and AF progression. 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 remodeling, inflammation, ion channel, myofibril structure, mitochondrial complexes and chromatin remodeling 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 correspond closely with the electrical and structural remodeling demonstrated previously in the sheep and in humans. The results provide novel insight into the dynamics of gene and protein expression changes that underlie AF-induced atrial remodeling and that make the arrhythmia become more stable and long lasting. Overall design: Left and right atrial appendages and posterior left appendage, whole-tissue and isolated cardiomyocytes, mRNA profiles of sham, transition and chronic sheeps were generated by deep sequencing, in triplicate, using Illumina Hiseq 2500.