Fluid shear stress-mediated regulation of endothelial adhesion molecule gene expression

Although originally designed as inhibitors of cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, are now known to also have non-lipid lowering benefits [1]. Statins have been reported to modulate gene expression in endothelial cells, however, the effect of statins on adhesion molecule expression is contradictory. Some studies report a decrease in adhesion molecule mRNA and/or protein after statin treatment [2], while others have shown that statins potentiate the effect of tumor necrosis factor alpha (TNFα) [3]. To the best of our knowledge, the effects of statins on gene expression in cultured endothelial cells has been done in static conditions only and no study has examined the effect of blood flow. This is particularly important since fluid shear stress is a strong regulator of endothelial cell function and phenotype [4]. The purpose of this study was to clarify the effects of statins on vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression in endothelial cells by evaluating their biological response under fluid flow.

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Epigenetic Changes During Mechanically Induced Osteogenic Lineage Commitment

Journal of Biomechanical Engineering ◽

10.1115/1.4029551 ◽

2015 ◽

Vol 137 (2) ◽

Cited By ~ 14

Author(s):

Julia C. Chen ◽

Mardonn Chua ◽

Raymond B. Bellon ◽

Christopher R. Jacobs

Keyword(s):

Gene Expression ◽

Dna Methylation ◽

Shear Stress ◽

Fluid Shear Stress ◽

Methylation Status ◽

Lineage Commitment ◽

Fluid Shear ◽

Osteogenic Lineage ◽

Osteogenic Markers ◽

Heterochromatin Structure

Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epigenetic regulation, is stable and heritable. Therefore, analyzing methylation status may be less temporally dependent and more informative for evaluating lineage commitment. Here we analyzed the effect of mechanical stimulation on osteogenic differentiation by applying fluid shear stress for 24 hr to osteocytes and then applying the osteocyte-conditioned medium (CM) to progenitor cells. We analyzed gene expression and changes in DNA methylation after 24 hr of exposure to the CM using quantitative real-time polymerase chain reaction and bisulfite sequencing. With fluid shear stress stimulation, methylation decreased for both adipogenic and osteogenic markers, which typically increases availability of genes for expression. After only 24 hr of exposure to CM, we also observed increases in expression of later osteogenic markers that are typically observed to increase after seven days or more with biochemical induction. However, we observed a decrease or no change in early osteogenic markers and decreases in adipogenic gene expression. Treatment of a demethylating agent produced an increase in all genes. The results indicate that fluid shear stress stimulation rapidly promotes the availability of genes for expression, but also specifically increases gene expression of later osteogenic markers.

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Cytoskeletal structure regulates endothelial cell immunogenicity independent of fluid shear stress

AJP Cell Physiology ◽

10.1152/ajpcell.00340.2009 ◽

2010 ◽

Vol 298 (2) ◽

pp. C333-C341 ◽

Cited By ~ 30

Author(s):

Keri B. Vartanian ◽

Michelle A. Berny ◽

Owen J. T. McCarty ◽

Stephen R. Hanson ◽

Monica T. Hinds

Keyword(s):

Gene Expression ◽

Cardiovascular Disease ◽

Shear Stress ◽

Fluid Shear Stress ◽

Positive Control ◽

U937 Cells ◽

Inflammation Markers ◽

Fluid Shear ◽

Cytoskeletal Structure ◽

Cytoskeletal Regulation

The cardiovascular disease atherosclerosis is directly linked to the functions of endothelial cells (ECs), which are affected by fluid shear stress (FSS). High, unidirectional FSS causes EC elongation with aligned cytoskeletal components and nonimmunogenic EC functions that protect against atherosclerosis. In contrast, low, oscillatory FSS is associated with cobblestone-shaped ECs with randomly oriented cytoskeletons and proinflammatory EC functions that promote atherosclerosis. Whether EC shape plays a role in EC immunogenic functions, independent of FSS, has not been previously determined. The goal of this study was to determine the effect of EC elongation and cytoskeletal alignment on the expression of inflammatory genes and functions. With the use of micropatterned lanes, EC elongation and cytoskeletal alignment were achieved in the absence of FSS. EC gene expression of key inflammation markers determined that the elongation and cytoskeletal alignment of micropattern-elongated ECs (MPECs) alone significantly downregulated VCAM-1 while having no effect on E-selectin and ICAM-1. The positive control of FSS-elongated ECs promoted E-selectin and VCAM-1 downregulation and upregulation of ICAM-1. Functionally, monocytic U937 cells formed weaker interactions on the surface of MPECs compared with cobblestone ECs. Interestingly, MPEC expression of the known FSS-dependent transcription factor krüppel-like factor 2 (KLF2), which promotes a nonimmunogenic EC phenotype, was significantly upregulated in MPECs compared with cobblestone ECs. Cytoskeletal regulation of KLF2 expression was shown to be dependent on microtubules. Therefore, the cellular elongation and cytoskeletal alignment of MPECs regulated immunogenic gene expression and functions and may act synergistically with FSS to create an EC surface with reduced inflammatory capability.

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