Mechanical effects on endothelial cell morphology: In vitro assessment

Abstract-Monolayers of human umbilical vein endothelial cells were activated with 50 U/mL interleukin-1␣ (IL-1␣) for 3 hours and simultaneously conditioned with shear stresses of 0, 0.68, or 13.2 dyne/cm 2 in a parallel-plate flow chamber. In the presence of an inflow buffer containing 100 nmol/L factor X and 10 nmol/L factor VII, production of factor Xa, a measure of functional tissue factor (TF), was determined as the product of outflow concentration of factor Xa (chromogenic assay performed under quasi-static flow conditions after the shear period) and flow rate. Similarly, production of TF pathway inhibitor (TFPI) was estimated as the product of antigenic TFPI (by enzyme-linked immunosorbent assay) in the supernatant and flow rate. In parallel experiments, total RNA was isolated for determination of amplification products of TF mRNA by reverse transcription-polymerase chain reaction. We found that shear stress reduced factor Xa production (meanϮSE; nϭnumber of experiments) from 13.33Ϯ1.14 (nϭ16) fmol/minϫcm 2 at 0 shear stress to 5.70Ϯ2.51 (nϭ5) and 0.54Ϯ0.54 (nϭ4) fmol/minϫcm 2 at shear stresses of 0.68 and 13.2 dyne/cm 2 , respectively. At the same time, immunogold labeling showed that TF antigen on the endothelial surface increased Ͼ5-fold with shear stress, whereas TFPI antigen on the surface increased 2-fold. The secretion of TFPI (appearance of new supernatant TFPI) rose from 7.4Ϯ2.4 (nϭ12) ϫ10 Ϫ3 fmol/minϫcm 2 at 0 shear stress to 23.7Ϯ7.3 (nϭ9) and 50.2Ϯ14.3 (nϭ4) ϫ10 Ϫ3 fmol/minϫcm 2 at 0.68 and 13.2 dyne/cm 2 , respectively. TF mRNA amplification products were not markedly changed by shear stress. We conclude that acute application of shear stress reduces functional, but not antigenic, expression of TF by intact, activated endothelial cell monolayers in a manner associated with shear stress-augmented endothelial cell secretion of TFPI. Key Words: tissue factor Ⅲ endothelial cells Ⅲ shear stress Ⅲ tissue factor pathway inhibitor T issue factor (TF) is the membrane-bound glycoprotein that serves as the nonenzymatic cofactor for factor VII/VIIa in the initiation of blood coagulation, whereas TF pathway inhibitor (TFPI), its principal inhibitor, binds to both activated factor X and the ternary complex formed by TF, factor VIIa, and factor Xa. Both TF and TFPI are synthesized by endothelial cells (ECs), the former usually only after cell activation. 1 With regard to increasing shear stress, functional TF has been shown to increase over a wide range of shear stress for a noncellular system of lipid bilayers, to which has been added exogenous TF that has been immobilized on the inner surface of a glass tube. 2 A similar increase has been demonstrated for monolayers of human fibroblasts, 3 which express TF in the absence of cytokine activation. With respect to monolayers of activated human ECs, however, the dependence on shear stress is more complex, passing through a maximum with respect to shear stress under 1 set of conditions 3 or decreasing monotonically with shear stress under another. 4 Prior work h...

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“…ECs also did not undergo elongation and alignment with flow direction, a phenomenon observed by others 16 after longer periods of shear stress.…”

Section: Endothelial Monolayer Morphologysupporting

confidence: 53%

Shear Stress Decreases Endothelial Cell Tissue Factor Activity by Augmenting Secretion of Tissue Factor Pathway Inhibitor

Grabowski

Reininger

Petteruti

et al. 2001

ATVB

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“…Fluid shear stress induces EC alignment and the increase of stress fibers in EC monolayers [Dewey, 1984;Franke et al, 1984;Levesque and Nerem, 1985;Ives et al, 1986;Galbraith et al, 1998]. Cell alignment and actin stress fibers require signal transduction through intracellular calcium release, tyrosine kinases, microtubule integrity, Rho/p160ROCK, Rac, Cdc42, p38 mitogenactivated protein kinase (p38MAPK), and p65PAK [Girard and Nerem, 1993;Malek and Izumo, 1996;Li et al, 1999;Azuma et al, 2001;Tzima et al, 2001;Birukov et al, 2002;WojciakStothard and Ridley, 2003], suggesting that shear stress activates multiple signaling pathways to regulate actin re-organization and changes in cell morphology.…”

Section: Cytoskeleton As Mechano-effectormentioning

confidence: 99%

Mechanotransduction in endothelial cell migration

Li¹,

Huang²,

Hsu³

2005

J of Cellular Biochemistry

239

180

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The migration of endothelial cells (ECs) plays an important role in vascular remodeling and regeneration. EC migration can be regulated by different mechanisms such as chemotaxis, haptotaxis, and mechanotaxis. This review will focus on fluid shear stress-induced mechanotransduction during EC migration. EC migration and mechanotransduction can be modulated by cytoskeleton, cell surface receptors such as integrins and proteoglycans, the chemical and physical properties of extracellular matrix (ECM) and cell-cell adhesions. The shear stress applied on the luminal surface of ECs can be sensed by cell membrane and associated receptor and transmitted throughout the cell to cell-ECM adhesions and cell-cell adhesions. As a result, shear stress induces directional migration of ECs by promoting lamellipodial protrusion and the formation of focal adhesions (FAs) at the front in the flow direction and the disassembly of FAs at the rear. Persistent EC migration in the flow direction can be driven by polarized activation of signaling molecules and the positive feedback loops constituted by Rho GTPases, cytoskeleton, and FAs at the leading edge. Furthermore, shear stressinduced EC migration can overcome the haptotaxis of ECs. Given the hemodynamic environment of the vascular system, mechanotransduction during EC migration has a significant impact on vascular development, angiogenesis, and vascular wound healing.

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“…The effect of stretch may also modulate vascular structure. 49 - 50 The signal transduction mechanisms mediating the effect of stretch on vascular function are currently under study. One possible mechanism is suggested by the recent discovery by Lansman et al 51 of a stretch-responsive nonspecific ion channel in bovine aortic endothelium.…”

Section: -33mentioning

confidence: 99%

New perspectives in hypertension research. Potentials of vascular biology.

et al. 1994

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The vessel wall was once considered to be a passive conduit responding to the circulating endocrine system. However, the emergence of molecular and vascular biology in hypertension research has redefined our understanding of the role of the vasculature as a vital organ in the pathogenesis of hypertension. It is now recognized that the vasculature can regulate its own tone by a variety of previously unknown autocrine and/or paracrine vasoactive systems. Recent evidence indicates that the process of vascular remodeling in hypertension appears to be mediated by locally generated factors within the vessel wall. This review examines the implications of this new paradigm in hypertension, focusing on O ver the past half century, the direction of hypertension research has been shaped by a scientific paradigm that has focused on the regulation of systemic neuroendocrine vasoactive systems that control vascular tone and renal fluid-electrolyte homeostasis. This paradigm postulates that hypertension is caused by a disturbance in the physiological homeostatic mechanisms regulating the levels of and/or responses to circulating hormones and sympathetic nervous system activity. In this schema the vasculature is conceptualized as a simple effector system that passively responds to the actions of systemic neuroendocrine factors. However, advances in molecular vascular biology have begun to promote a paradigm shift that has dramatically altered our conception of the role of the vasculature in hypertension. Based on recent studies it has become increasingly clear that the vasculature is itself a complex, integrated organ capable of autonomous generation of locally active factors that mediate changes in tone and structure. This review will examine the implications of this new molecular vascular biology paradigm in hypertension research, focusing on five areas in which vascular biology has had or will have major effects on hypertension research: (1) the discovery of novel endogenous biologically active molecules synthesized by the vessel wall, (2) the elucidation of molecular mechanisms and consequences of vascular remodeling in hypertension, (3) an understanding of the developmental biology of the blood vessel and the relation to pathobiology, (4) the in vivo testing of in vitro hypotheses using in vivo gene transfer, and (5) the development of novel treatment strategies based on vascular molecular biology, such as gene therapy.

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Mechanical effects on endothelial cell morphology: In vitro assessment

Cited by 231 publications

References 20 publications

Shear Stress Decreases Endothelial Cell Tissue Factor Activity by Augmenting Secretion of Tissue Factor Pathway Inhibitor

Shear Stress Decreases Endothelial Cell Tissue Factor Activity by Augmenting Secretion of Tissue Factor Pathway Inhibitor

Mechanotransduction in endothelial cell migration

New perspectives in hypertension research. Potentials of vascular biology.

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