Unraveling the molecular complexity of bicuspid aortopathy: Lessons from comparative proteomics

Molecular markers and pathways involved in the etiology and pathophysiology of bicuspid aortopathy are poorly understood. The aim here is to delve into the molecular and cellular mechanisms of the disease and identify potential predictive molecular markers using a well-established isogenic hamster model (T-strain) of bicuspid aortic valve (BAV) and thoracic aortic dilatation (TAD). We carried out comparative quantitative proteomics combined with western blot and morpho-molecular analyses in the ascending aorta of tricuspid aortic valve (TAV) and BAV animals from the T-strain, and TAV animals from a control strain. This strategy allows discriminating between genetic and hemodynamic factors in genetically homogeneous populations. The major molecular alteration in the aorta of genetically homogeneous BAV individuals is PI3K/AKT overactivation caused by changes in the EGF, ANGII and TGF-β pathways. PI3K/AKT affects downstream eNOS, MAP2K1/2, NF-κB, mTOR and WNT pathways. Most of these alterations are seen in independent patient studies with different clinical presentations, but not in TAV hamsters from T-strain that mainly exhibit WNT pathway downregulation. Therefore, we identify a combination of defective interconnected molecular pathways, directly linked to the central PI3K/AKT pathway, common to both BAV-associated TAD patients and hamsters. The defects indicate smooth muscle cell shift towards the synthetic phenotype induced by endothelial-to-mesenchymal transition, oxidative stress and inflammation. WNT signaling represent one genetic factor that may cause structural aortic abnormalities and aneurysm predisposition, whereas hemodynamics is the main trigger of molecular alterations, probably determining aortopathy progression. We identify twenty-seven novel potential biomarkers with a high predictive value.