B10N

Heart failure and atrial fibrillation (AF) are growing cardiovascular disease epidemics worldwide. A previous lifetime AF risk estimate of 1 in 4 individuals was recently revised to 1 in 3 individuals of European ancestry at index age of 55 years. It is well accepted that AF can induce left ventricular (LV) systolic dysfunction which is called arrhythmia-induced cardiomyopathy. Rhythm restoration is associated with reversibility of LV systolic dysfunction. AF can be found in up to ~60% of patients with pulmonary hypertension (PH), depending on the underlying aetiology. These very frequently coexisting comorbidities can exacerbate each other and worsen the prognosis. However, nearly nothing is known about the consequences, the interaction with the right ventricle (RV), and the general role of AF in patients with PH. Likewise, despite of the high co-association of AF and PH, evidence-based treatment strategies remain largely unknown. Therefore, the aim of this project is to provide the first evidence on the effects of AF on the RV in the context of PH to better understand the pathophysiology and to develop disease-modifying agents capable of reversing the natural pathological progression. We previously demonstrated that AF causes distinct remodeling of the human LV and studied common mechanisms, including Ca^2+/calmodulin-dependent protein kinase II (CaMKII), KLF15 and the Wnt pathway along with their transcriptional networks. We also defined targets and therapeutic approaches for preclinical proof of concepts (PoC) to prevent heart failure. In this project, we aim to apply our knowledge and tools to study the biology of RV remodeling in the context of AF and PH. Specifically, we will test the hypothesis that 1) PH-associated AF results in detrimental functional and structural RV-remodeling aggravating right heart failure; 2) signaling crosstalk rather than single candidates (e.g., Wnt signaling and CaMKII, which are known to cooperate in other contexts) are involved in a disease network activation that synergistically drive disease transition and that 3) identification of these novel networks will allow the development of targeting approaches to prevent death and RV decompensation induced by pH-associated AF. In order to test these hypotheses, we will i) first study the functional and molecular characteristics of RV´s samples from explanted human hearts with AF compared to sinus rhythm in the groups with and without PH. The analysis will include functional investigations and cellular electrophysiology (contractility, cellular Ca²⁺ imaging, patch-clamp) of isolated human RV cardiomyocytes and long-term beating cardiac slices, in vitro AF simulation, reactive oxygen species, single cell transcriptome and chromatin status, proteomics (heart/plasma and extracellular vesicles) and spatial transcriptomic (collaboration A01, A07, A10N, B03). Clinic data and biomarkers will be integrated for the analysis (collaboration B07). ii) Next, hypothesis-driven mechanisms will be studied, specifically, CaMKII, Wnt and KLF15 as well as a systematic analysis focusing on cell specific transcriptional profiles, cell-cell-interaction and the role of inflammatory cells in cardiomyocytes and vascular cell remodeling will be performed. iii) Identified mechanisms will be validated in human isolated cardiomyocytes, slices and trabeculae, and human induced-pluripotent stem cells (hIPSC)-derived cardiomyocytes (collaboration B07) or vascular cells. The systemic effect of activated mechanisms on distant organs will be studied in transgenic mouse models. iv) Selection of targets for a PoC study to reverse disease progression will be done and their modulation will be achieved via CRIPSR-mediated transcriptional modulation and AF simulation approaches. Finally, we will perform a first clinical trial in patients with persistent AF scheduled for AF ablation. Together with project B08 we will measure invasive hemodynamics including pressure volume loops and sophisticated hemodynamic phenotyping in PH- patients during AF ablation in AF and following rhythm restoration in sinus rhythm to understand the hemodynamic consequences of AF in these patients for the first time. Our findings will help to understand the role of AF in detrimental PH-dependent RV remodeling and identify human relevant mechanisms driving disease progression as well as their suitability for therapeutic approaches.