Substrate Stiffness Affects Endothelial Cell Junctions and MAPK Signaling Pathway

Vascular homeostasis is critical for maintaining normal vascular structure and function. Aging is an irreversible trigger of vascular sclerosis, which causes structural and functional damage to blood vessels, leading to severe atherosclerosis. Endothelial cells (ECs) can respond to mechanical stimuli from the extracellular matrix, causing disruption of endothelial barrier function and activating signaling pathways to regulate cellular behavior under pathological conditions. In this paper, we investigated the effect of substrate stiffness on endothelial cell junctions, and the activation of mitogen-activated protein kinase (MAPK) signaling pathways. An in vitro stiffness model was established using polyacrylamide hydrogels of 1 kPa, 20 kPa and 100 kPa. By transcriptome analysis, we found that the cell-cell junction, cadherin binding, cytoskeleton and classical signaling pathways such as MAPK and Rho GTPase of endothelial cells were regulated by substrate stiffness. The expression of cell junction-related molecules TJP1, TJP2, JAM3 and JCAD was also found to be reduced at higher stiffness. The MAPK signaling pathway-related molecules MAP2K3, MAP2K7, MAP3K3, MAP3K6, MAPK3, MAPK7 were upregulated with increased stiffness. qRT-PCR analysis showed that the gene expression of JCAD was reduced with increased stiffness. Immunofluorescence staining of VE-cadherin indicated that the total fluorescence level of VE-cadherin decreased significantly with increased stiffness, and stiffness impaired the cell-cell junction with increased punctuation and discontinuity. Western blotting analysis confirmed that the protein expression ratio of pp38MAPK/p38MAPK increased with stiffness. Our research suggested that substrate stiffness played an important role in regulating endothelial cell integrity and MAPK signaling pathway.