Shear Stress Modulation of Smooth Muscle Cell Marker Genes in 2-D and 3-D Depends on Mechanotransduction by Heparan Sulfate Proteoglycans and ERK1/2

Zhong-Dong Shi,John M Tarbell,Giya Abraham,Sudha Agarwal

doi:10.1371/journal.pone.0012196

Zhong-Dong Shi, John M Tarbell + Show 2 more

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https://doi.org/10.1371/journal.pone.0012196

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Journal: PloS one	Publication Date: Aug 16, 2010
Citations: 88	License type: CC BY 4.0

Affiliation: City College of New York

Abstract

BackgroundDuring vascular injury, vascular smooth muscle cells (SMCs) and fibroblasts/myofibroblasts (FBs/MFBs) are exposed to altered luminal blood flow or transmural interstitial flow. We investigate the effects of these two types of fluid flows on the phenotypes of SMCs and MFBs and the underlying mechanotransduction mechanisms.Methodology/Principal FindingsExposure to 8 dyn/cm2 laminar flow shear stress (2-dimensional, 2-D) for 15 h significantly reduced expression of α-smooth muscle actin (α-SMA), smooth muscle protein 22 (SM22), SM myosin heavy chain (SM-MHC), smoothelin, and calponin. Cells suspended in collagen gels were exposed to interstitial flow (1 cmH2O, ∼0.05 dyn/cm2, 3-D), and after 6 h of exposure, expression of SM-MHC, smoothelin, and calponin were significantly reduced, while expression of α-SMA and SM22 were markedly enhanced. PD98059 (an ERK1/2 inhibitor) and heparinase III (an enzyme to cleave heparan sulfate) significantly blocked the effects of laminar flow on gene expression, and also reversed the effects of interstitial flow on SM-MHC, smoothelin, and calponin, but enhanced interstitial flow-induced expression of α-SMA and SM22. SMCs and MFBs have similar responses to fluid flow. Silencing ERK1/2 completely blocked the effects of both laminar flow and interstitial flow on SMC marker gene expression. Western blotting showed that both types of flows induced ERK1/2 activation that was inhibited by disruption of heparan sulfate proteoglycans (HSPGs).Conclusions/SignificanceThe results suggest that HSPG-mediated ERK1/2 activation is an important mechanotransduction pathway modulating SMC marker gene expression when SMCs and MFBs are exposed to flow. Fluid flow may be involved in vascular remodeling and lesion formation by affecting phenotypes of vascular wall cells. This study has implications in understanding the flow-related mechanobiology in vascular lesion formation, tumor cell invasion, and stem cell differentiation.

Highlights

The major functions of vascular smooth muscle cells (SMCs) are to maintain and regulate blood vessel tone, blood pressure, and blood flow distribution
Exposure to 8 dyn/cm2 of laminar shear stress significantly reduced a-smooth muscle actin (a-SMA), smooth muscle protein 22 (SM22 called as transgelin), smooth muscle myosin heavy chain (SM-MHC), smoothelin (SMTN), and calponin gene expression in both SMCs (Figure 1A) and MFBs (Figure 1B)
It has been widely recognized that laminar flow shear stress has a great impact on endothelial cells (ECs) biology [25]

Summary

Introduction

The major functions of vascular smooth muscle cells (SMCs) are to maintain and regulate blood vessel tone, blood pressure, and blood flow distribution. Modeling studies have shown that transmural interstitial flow passes through the oriented SMC layers to the adventitia and imposes shear stresses on SMCs and FBs that are of the order of 0.1 dyn/cm, and could be lower or higher depending on the location of the cells in the vessel wall [5,10,11]. In the early stages of injury, shear stresses (luminal blood flow and transmural interstitial flow) on SMCs are elevated, and have been hypothesized to contribute to neointima formation [5,12,13,14]. We investigated how laminar flow and interstitial flow affect the expression of SMC marker genes and the potential role of ERK1/ 2. We examined the role of HSPGs in mechanotransduction in both 2-D and 3-D

Results

Discussion

Materials and Methods