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

Abstract

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.

Transcriptomic profiling of canine atrial fibrillation models after one week of sustained arrhythmia

“…We confirmed the occurrence of known AF factors like the reactivation of developmental pathways, but also found a strong and novel association with microRNAs and lncRNA from the DLK1-DIO3 locus, including the MEG3 canine orthologue. This finding is concordant with the many chromatin remodeling genes dysregulated in our models, which is an emerging phenotype of AF both in human and sheep models 35 .…”

“…This is not observed in the AF group (lacking AVB), which may indicate that this adaptation has already occurred. This idea would be consistent with the down-regulation of chromatin-related genes recently noted in the atria of sheep AF models 35 , and may be a result of earlier establishment of profibrotic transdifferentiation in AF compared to AF+AVB canine models.…”

Systematic in vivo interrogation identifies novel enhancers and silencers associated to Atrial Fibrillation

“…AF-SNPs in this locus lie within a gene desert where we and others found distal enhancer elements that interact with the promoters of PITX2 and ENPEP (34, 95, 96). On the one hand, PITX2 encodes a developmental TF expressed in the atria (97) found to be decreased in AF patients (98, 99) and in a sheep model of induced AF (100). On the other hand, ENPEP encodes aminopeptidase A, a member of the reninangiotensin system that cleaves angiotensin II to produce angiotensin III and is involved in hypertension (101).…”

Functional genomics and epigenomics of atrial fibrillation

“…Of those patients, most suffered from cardiovascular artery disease, valvular disease or heart failure, and in some cases, were under treatment for the previously mentioned or related comorbidities. In addition, although left atrial tissue has been demonstrated to undergo more profound remodeling [12] , the difficulty in J o u r n a l P r e -p r o o f obtaining left atria samples has led to an overrepresentation of right atrial tissue in published transcriptomic studies. Moreover, the collection of samples at different time points of disease progression is impossible for obvious reasons.…”

“…Several studies in goats, sheep and pigs show that artificially maintained AF leads to increasingly longer episodes of sustained arrhythmia [9,[179][180][181]. As an example of the potential of these induced AF animal models, we have recently described transcriptomic and proteomic changes during different stages of the disease in sheep and shown that most significant changes occurred at early stages of disease progression [12]. Moreover, goats are a well-established model of AF that has been used to test major pathophysiological signatures of the disease and the efficacy of antiarrhythmic drugs [182,183].…”