The Effect of Substrate Stiffness on VCAM-1 Expression and Monocyte Adhesion in Rat Lung Microvascular Endothelial Cells

Abstract

The overall goal of this research is to elucidate the effects of stiffness on the activation of pulmonary endothelial cells by inflammatory cytokines. The hypothesis tested is that increasing matrix stiffness in the (patho) physiological range will exacerbate the response of cultured endothelial cells to inflammatory stimuli. To test this hypothesis, we are culturing control and TNF-a stimulated rat lung microvascular endothelial cells (RLMVECs) on hydrogels with tunable stiffnesses of 5, 20, and 45 kPa (measured using compression testing), modeling the stiffness of healthy, intermediate and fibrotic lung tissue respectively. The cellular readout was assessed through RT-qPCR, microscopy, and monocyte adhesion for basal expression and upregulation of vascular cell adhesion molecule-1 (VCAM-1) in quiescent and TNF-a stimulated cultured endothelial cell. This model of microvascular pulmonary inflammation, mimicking a normal, intermediate, and fibrotic lung, is aimed at establishing a correlation between substrate stiffness and inflammation. This research demonstrates the significant increase of basal VCAM-1 gene expression as well as monocyte adhesion as substrate stiffness increases. When using inhibition, it was also found that VCAM-1 is partially activated through the Rho/ROCK, YAP/TAZ, and NF-kB pathway. Our results contribute to a mechanistic understanding of disease pathologies such as idiopathic pulmonary fibrosis, in which treatment is just about limited to a full lung transplant and facilitate testing of new drug therapies.