Modulation of arterial intima stiffness by disturbed blood flow

The intima, comprising the endothelium and the subendothelial matrix, plays a crucial role in atherosclerosis pathogenesis. The mechanical stress arising from disturbed blood flow (d-flow) and the stiffening of the arterial wall contributes to endothelial dysfunction. However, the specific impacts of these physical forces on the mechanical environment of the intima remain undetermined. Here, we investigated whether inhibiting collagen crosslinking could ameliorate the detrimental effects of persistent d-flow on the mechanical properties of the intima. Partial ligation of the left carotid artery (LCA) was performed in C57BL/6J mice, inducing d-flow. The right carotid artery (RCA) served as an internal control. Carotids were collected 2 days and 2 weeks after surgery to study acute and chronic effects of d-flow on the mechanical phenotype of the intima. The chronic effects of d-flow were decoupled from the ensuing arterial wall stiffening by administration of β-aminopropionitrile (BAPN), an inhibitor of collagen crosslinking by lysyl oxidase (LOX) enzymes. Atomic force microscopy (AFM) was used to determine stiffness of the endothelium and the denuded subendothelial matrix in en face carotid preparations. The stiffness of human aortic endothelial cells (HAEC) cultured on soft and stiff hydrogels was also determined. Acute exposure to d-flow caused a slight decrease in endothelial stiffness in male mice but had no effect on the stiffness of the subendothelial matrix in either sex. Regardless of sex, the intact endothelium was softer than the subendothelial matrix. In contrast, exposure to chronic d-flow led to a substantial increase in the endothelial and subendothelial stiffness in both sexes. The effects of chronic d-flow were largely prevented by concurrent BAPN administration. In addition, HAEC displayed reduced stiffness when cultured on soft vs. stiff hydrogels. We conclude that chronic d-flow results in marked stiffening of the arterial intima, which can be effectively prevented by inhibition of collagen crosslinking.