Abstract
Endothelial cells respond to changes in subendothelial stiffness by altering their migration and mechanics, but whether those responses are due to transcriptional reprogramming remains largely unknown. We measured traction force generation and also performed gene expression profiling for two endothelial cell types grown in monolayers on soft or stiff matrices: primary human umbilical vein endothelial cells (HUVEC) and immortalized human microvascular endothelial cells (HMEC-1). Both cell types respond to changes in subendothelial stiffness by increasing the traction stresses they exert on stiffer as compared to softer matrices, and exhibit a range of altered protein phosphorylation or protein conformational changes previously implicated in mechanotransduction. However, the transcriptome has only a minimal role in this conserved biomechanical response. Only few genes were differentially expressed in each cell type in a stiffness-dependent manner, and none were shared between them. In contrast, thousands of genes were differentially regulated in HUVEC as compared to HMEC-1. HUVEC (but not HMEC-1) upregulate expression of TGF-β2 on stiffer matrices, and also respond to application of exogenous TGF-β2 by enhancing their endogenous TGF-β2 expression and their cell-matrix traction stresses. Altogether, these findings provide insights into the relationship between subendothelial stiffness, endothelial mechanics and variation of the endothelial cell transcriptome, and reveal that subendothelial stiffness, while critically altering endothelial cells’ mechanical behavior, minimally affects their transcriptome.
Highlights
Endothelial cells respond to changes in subendothelial stiffness by altering their migration and mechanics, but whether those responses are due to transcriptional reprogramming remains largely unknown
Using the fluorescence images of the beads we infer the deformations the cells impart and the stresses they exert on their matrix through traction force microscopy (TFM)25. 3 kPa is the lowest stiffness we examined since as previously reported, we find that Endothelial cells (ECs) seeded on
In this study we showed for the first time that subendothelial stiffness has a minimal effect on the transcriptome of human umbilical vein endothelial cells (HUVEC) and HMEC-1 cells when those are seeded in confluence for 24 h on collagen I-coated hydrogels
Summary
Endothelial cells respond to changes in subendothelial stiffness by altering their migration and mechanics, but whether those responses are due to transcriptional reprogramming remains largely unknown. We compared the responses of two different types of ECs to growth on stiff versus soft hydrogel substrates, primary human umbilical vein endothelial cells (HUVEC) cultured from normal human tissue and immortalized human microvascular endothelial cells (HMEC-1) that were transformed using SV40 large T antigen[21] Both cell types in confluent monolayers changed their mechanical behavior in response to increasing subendothelial stiffness by elevating their cell-matrix traction stresses on stiffer as compared to softer matrices, and altering protein phosphorylation profiles associated with mechanotransduction. Only very modest stiffness-dependent alterations in gene expression were observed using RNA sequencing
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