Tricuspid Aortic Valve Regurgitation Associates With Ascending Aortic Aneurysm Through Endothelial Activation and Lipoprotein Infiltration.

BACKGROUND

An abnormal accumulation of immune cells and inflammation has been described in ascending aortic aneurysm, but the factor driving disease initiation remains elusive. Interestingly, ascending aortic dilatation often occurs alongside aortic regurgitation but rarely with aortic stenosis. We sought to investigate ascending aortic aneurysm initiation by assessing the relation between aortic regurgitation and vascular activation and inflammation.

METHODS

In this prospective cohort study, patients with tricuspid aortic valves undergoing elective open-heart surgery were included. Aortic specimens from organ donors were obtained through the University of Miami Tissue Bank. Spatial transcriptomics measured gene expression in nondilated aortic endothelium, intima, and subintima. Immunohistochemistry determined protein expression. Aortic dimensions were recorded preoperatively and 10 years after surgery using echocardiography. Aortic gene expression affected by physiological blood flow was previously measured in Wistar rats.

RESULTS

We show a mesenchymal activation of endothelial cells, possibly mediated by bidirectional flow, in the nondilated ascending aorta of patients with aortic regurgitation, accompanied by intimal infiltration, retention, and oxidation of apoB-containing lipoproteins. We further observed intimal upregulation of genes coding for core proteins of lipoprotein-binding proteoglycans and the (oxidized low-density lipoprotein receptor 1), the latter by infiltrating macrophages and in association with progressive inflammation and dilatation. None of the above was observed in patients with aortic stenosis. Notably, surgical replacement of regurgitant valves, but not stenotic valves, mitigated 10-year aortic growth.

CONCLUSIONS

Our results highlight a distinct pathological role of aortic regurgitation in ascending aortic aneurysm formation by promoting mesenchymal activation of endothelial cells and lipoprotein-related immune cell infiltration and inflammation in patients with tricuspid aortic valves. We also provide novel insights into the long-term impact of surgical aortic valve replacement on ascending aortic growth and suggest a diagnostic or therapeutic target in oxidized low-density lipoprotein cholesterol.