ABSTRACT
Atherosclerotic plaque localization correlates with regions of disturbed flow in which endothelial cells (ECs) align poorly, whereas sustained laminar flow correlates with cell alignment in the direction of flow and resistance to atherosclerosis. We now report that in hypercholesterolemic mice, deletion of syndecan 4 (S4(-/-)) drastically increased atherosclerotic plaque burden with the appearance of plaque in normally resistant locations. Strikingly, ECs from the thoracic aortas of S4(-/-) mice were poorly aligned in the direction of the flow. Depletion of S4 in human umbilical vein endothelial cells (HUVECs) using shRNA also inhibited flow-induced alignment in vitro, which was rescued by re-expression of S4. This effect was highly specific, as flow activation of VEGF receptor 2 and NF-κB was normal. S4-depleted ECs aligned in cyclic stretch and even elongated under flow, although nondirectionally. EC alignment was previously found to have a causal role in modulating activation of inflammatory versus antiinflammatory pathways by flow. Consistent with these results, S4-depleted HUVECs in long-term laminar flow showed increased activation of proinflammatory NF-κB and decreased induction of antiinflammatory kruppel-like factor (KLF) 2 and KLF4. Thus, S4 plays a critical role in sensing flow direction to promote cell alignment and inhibit atherosclerosis.
Subject(s)
Atherosclerosis/metabolism , Endothelial Cells/metabolism , Signal Transduction , Syndecan-4/metabolism , Animals , Atherosclerosis/genetics , Blotting, Western , Cells, Cultured , Endothelial Cells/cytology , Female , Human Umbilical Vein Endothelial Cells/cytology , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Kruppel-Like Factor 4 , Kruppel-Like Transcription Factors/genetics , Kruppel-Like Transcription Factors/metabolism , Male , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Confocal , NF-kappa B/metabolism , RNA Interference , Reverse Transcriptase Polymerase Chain Reaction , Stress, Mechanical , Syndecan-4/genetics , Vascular Endothelial Growth Factor Receptor-2/metabolismABSTRACT
OBJECTIVE: Vasa vasorum are angiogenic in advanced stages of human atherosclerosis and hypercholesterolemic mouse models. Fibroblast growth factor-2 (FGF-2) is the predominant angiogenic growth factor in the adventitia and plaque of hypercholesterolemic low-density lipoprotein receptor-deficient/apolipoprotein B(100/100) mice (DKO). FGF-2 seems to play a role in the formation of a distinct vasa vasorum network. This study examined the vasa vasorum structure and its relationship to FGF-2. METHODS AND RESULTS: DKO mice treated with saline, antiangiogenic recombinant plasminogen activator inhibitor-1(23) (rPAI-1(23)), or soluble FGF receptor 1 were perfused with fluorescein-labeled Lycopersicon esculentum lectin. Confocal images of FGF-2-probed descending aorta adventitia show that angiogenic vasa vasorum form a plexus-like network in saline-treated DKO similar to the FGF-2 pattern of distribution. Mice treated with rPAI-1(23) and soluble FGF receptor 1 lack a plexus; FGF-2 and vasa vasorum density and area are significantly reduced. A perlecan/FGF-2 complex is critical for plexus stability. Excess plasmin produced in rPAI-1(23)-treated DKO mice degrades perlecan and destabilizes the plexus. Plasmin activity and plaque size measured in DKO and DKO/plasminogen activator inhibitor-1(-)(/-) mice demonstrate that elevated plasmin activity contributes to reduced plaque size. CONCLUSIONS: An FGF-2/perlecan complex is required for vasa vasorum plexus stability. Elevated plasmin activity plays a significant inhibitory role in vasa vasorum plexus and plaque development.
Subject(s)
Aorta/metabolism , Aortic Diseases/metabolism , Atherosclerosis/metabolism , Fibroblast Growth Factor 2/metabolism , Hypercholesterolemia/metabolism , Neovascularization, Pathologic , Vasa Vasorum/metabolism , Angiogenesis Inhibitors/pharmacology , Animals , Aorta/drug effects , Aorta/pathology , Aortic Diseases/drug therapy , Aortic Diseases/genetics , Aortic Diseases/pathology , Apolipoprotein B-100 , Apolipoproteins B/deficiency , Apolipoproteins B/genetics , Atherosclerosis/drug therapy , Atherosclerosis/genetics , Atherosclerosis/pathology , Cholesterol, Dietary , Disease Models, Animal , Fibrinolysin/metabolism , Gene Transfer Techniques , Heparan Sulfate Proteoglycans/metabolism , Hypercholesterolemia/complications , Hypercholesterolemia/genetics , Hypercholesterolemia/pathology , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Confocal , Plaque, Atherosclerotic , Receptor, Fibroblast Growth Factor, Type 1/genetics , Receptor, Fibroblast Growth Factor, Type 1/metabolism , Receptors, LDL/deficiency , Receptors, LDL/genetics , Rupture, Spontaneous , Vasa Vasorum/drug effects , Vasa Vasorum/pathologyABSTRACT
A laser light-scattering instrument has been designed to facilitate the real-time detection of potentially hazardous respirable fibers, such as asbestos, within an ambient environment. The instrument captures data relating to the spatial distribution of light scattered by individual particles in flow by use of a dedicated multielement photodiode detector array. These data are subsequently processed with an artificial neural network that has previously been trained to recognize those features or patterns within the light-scattering distribution that may be characteristic of the specific particle types being sought, such as, for example, crocidolite or chrysotile asbestos fibers. Each particle is thus classified into one of a limited set of classes based on its light-scattering properties, and from the accumulated data a particle concentration figure for each class may be produced and updated at regular intervals. Particle analysis rates in excess of 103 /s within a sample volume flow rate of 1 l /min are achievable, offering the possibility of detecting fiber concentrations at the recommended maximum exposure limit of 0.1 fibers /ml within a sampling period of a few seconds.
