Shear Stress Initiates Endothelial-to-Mesenchymal Transition in Endocardial Endothelial Cells

Area of Science:

• Cardiovascular Biology
• Biomedical Engineering
• Cellular Mechanobiology

Background:

• Discrete subaortic stenosis (DSS) is a congenital heart defect characterized by fibrotic membrane formation below the aortic valve.
• The cellular mechanisms driving DSS pathogenesis remain largely unknown.
• Elevated pressure gradients in the left ventricular outflow tract (LVOT) are a hallmark of DSS.

Purpose of the Study:

• To investigate the hypothesis that elevated wall shear stress (WSS) on LVOT endocardial endothelial cells (EECs) induces fibrosis in DSS.
• To correlate WSS with fibrotic phenotypes in EECs.

Main Methods:

• Applied controlled fluid shear stress to EECs using a cone-and-plate device to mimic physiological and pathological WSS conditions.
• Analyzed EEC alignment, endothelial-to-mesenchymal transformation (EndMT) signaling pathways, and SNAI1 gene expression.
• Treated EECs with a Snail1 inhibitor (CYD19) and assessed its effect on EndMT signaling under pathological shear stress.

Main Results:

• Elevated shear stress induced EEC alignment and triggered EndMT signaling pathways, evidenced by SNAI1 gene upregulation.
• Snail1 inhibition partially and transiently downregulated selected EndMT markers.
• The mechanical effect of shear stress on EEC gene and protein expression was more pronounced than Snail1 inhibition.

Conclusions:

• Mechanical forces, specifically elevated shear stress, significantly influence EEC phenotype and may play a crucial role in DSS membrane formation.
• Further research is needed to elucidate the precise mechanisms by which mechanical stimulation drives fibrosis and DSS pathogenesis.