Heparan Sulfate Proteoglycans Mediate Interstitial Flow Mechanotransduction Regulating MMP-13 Expression and Cell Motility via FAK-ERK in 3D Collagen

Interstitial flow directly affects cells that reside in tissues and regulates tissue physiology and pathology by modulating important cellular processes including proliferation, differentiation, and migration. However, the structures that cells utilize to sense interstitial flow in a 3-dimensional (3D) environment have not yet been elucidated. Previously, we have shown that interstitial flow upregulates matrix metalloproteinase (MMP) expression in rat vascular smooth muscle cells (SMCs) and fibroblasts/myofibroblasts via activation of an ERK1/2-c-Jun pathway, which in turn promotes cell migration in collagen. Herein, we focused on uncovering the flow-induced mechanotransduction mechanism in 3D.Cleavage of rat vascular SMC surface glycocalyx heparan sulfate (HS) chains from proteoglycan (PG) core proteins by heparinase or disruption of HS biosynthesis by silencing N-deacetylase/N-sulfotransferase 1 (NDST1) suppressed interstitial flow-induced ERK1/2 activation, interstitial collagenase (MMP-13) expression, and SMC motility in 3D collagen. Inhibition or knockdown of focal adhesion kinase (FAK) also attenuated or blocked flow-induced ERK1/2 activation, MMP-13 expression, and cell motility. Interstitial flow induced FAK phosphorylation at Tyr925, and this activation was blocked when heparan sulfate proteoglycans (HSPGs) were disrupted. These data suggest that HSPGs mediate interstitial flow-induced mechanotransduction through FAK-ERK. In addition, we show that integrins are crucial for mechanotransduction through HSPGs as they mediate cell spreading and maintain cytoskeletal rigidity.We propose a conceptual mechanotransduction model wherein cell surface glycocalyx HSPGs, in the presence of integrin-mediated cell-matrix adhesions and cytoskeleton organization, sense interstitial flow and activate the FAK-ERK signaling axis, leading to upregulation of MMP expression and cell motility in 3D. This is the first study to describe a flow-induced mechanotransduction mechanism via HSPG-mediated FAK activation in 3D. This study will be of interest in understanding the flow-related mechanobiology in vascular lesion formation, tissue morphogenesis, cancer cell metastasis, and stem cell differentiation in 3D, and also has implications in tissue engineering

Silicon- versus carbon-containing ions: 1,3-CH3+ transfers

International audienceIn the second field-free region of a double focusing mass spectrometer, the spontaneous fragmentation of the (CH3)(3)C-O-C+ (CD3)(2) ion is not preceded by direct methyl cation migrations. In contrast, a complete exchange of the methyl groups occurs prior to dissociation of the (CH3)(3)Si-O-Si+(CD3)(2) ion. This is in agreement with the calculated energy diagram which shows that two factors explain this behavior. (i) The simple cleavage of (CH3)(3)C-O-C+(CD3)(2) giving (CH3)(3)(C+) only requires 25.8 kcal mol(-1) while the corresponding fragmentation in (CH3)(3)Si-O-Si+(CD3)(2) necessitates 74.2 kcal mol(-1). (ii) The transition state for the 1,3-CH3+ transfer from carbon to carbon lies in energy 59.1 kcal mol(-1) above the covalent structure (CH3)(3)C-O-C+(CD3)(2) and only 12.4 kcal mol(-1) for the 1,3-CH3+ transfer from silicon to silicon. Calculations and experiments show that the situation is intermediate for the 1,3-CH3+ from silicon to carbon. (Cop) 2002 Published by Elsevier Science B.V

Gas phase basicity of silanaldehydes and silanones

International audienceGas basicities (GBs) and proton affinities (PAs) of CH3SiH=O, CH3CH2SiH=O, (CH3)2Si=O (CH3CH2)2Si=O, were determined by using the kinetic method as well as calculations. From experiment, GB of these molecules were respectively measured to be 203.3, 206.3, 213.4 and 218.0kcalmol-1. The precision is estimated to be 0.5kcalmol-1. Calculations are in excellent agreement with experiment. GB and PA of the R1R2Si=O compounds are far above those of their counterparts R1R2C=O, containing exclusively carbon. The difference lies between 25 and 30kcalmol-1 and slightly decreases as the substitution degree of silicon increases. This behavior strongly contrasts with that of silanols or silanamines whose GB and PA are close to those of the corresponding alcohols or amines. This can be explained by the high ΔHf of neutral low coordinate molecules containing silicon. © 2003 Elsevier Science B.V. All rights reserved

Heritage as sector, factor and vector: conceptualizing the shifting relationship between heritage management and spatial planning

Heritage is a highly malleable concept that is constantly in flux and whose substance and meaning are continuously being redefined by society. From such a dynamic perspective, it is inevitable that new approaches and practices have developed for dealing with heritage in the context of planned development. While most scholars acknowledge the existence of various heritage approaches, one of the major defining features is often neglected: their distinctive outlook on spatial dynamics. In this article, the shifting role and purpose of heritage conservation in Dutch spatial planning is analysed. A conceptual framework is introduced that frames three approaches to the planning treatment of heritage; the sector, factor and vector approach, respectively. Although these approaches have developed in a historical sequence, the new did not replace the old but rather gained ground amongst different actors. Thus, three quite different ways of treating the past in the present now coexist in Dutch planning practice. Although this coexistence can raise conflict, we argue that contemporary heritage planning does not call for a one-size-fits-all approach, but rather for a mixed-mode model.Landscape Architectur

Townscape Heritage Initiatives evaluation: Methodology for assessing the effectiveness of Heritage Lottery Fund projects in the United Kingdom

As a result of various social and economic factors, many historic townscapes in the United Kingdom and elsewhere have declined over the last half century. There have been many attempts throughout the world to revitalise such urban heritage areas, but the actual effectiveness of few of these schemes has been systematically evaluated. Good public policy choices would greatly benefit from such evaluation. The UK's Heritage Lottery Fund (HLF) decided in 1999 that their Townscape Heritage Initiatives would be an exception. A research team from Oxford Brookes University was engaged to undertake a ten-year study of the £52 million being spent in about sixty British towns and cities. A sample of about one third of projects receiving HLF support are being scrutinised. The evaluation methodology is outlined, along with explanations of some challenges faced in such a large programme. The four mechanisms for gathering research data are explained, the origin and rationale for the sixteen indicators being employed are described, and the approach to overall evaluation outlined. Finally there is an overview of the baseline stage of the work, highlighting key issues from a research perspective, and briefly reflecting on findings to date. © 2004 a Pion publication printed in Great Britain