Project description:Physiological shear stress, produced by blood flow, homeostatically regulates the phenotype of pulmonary endothelial cells exerting anti-inflammatory and anti-thrombotic actions and maintaining normal barrier function. In the pulmonary circulation hypoxia, due to high altitude or diseases such as COPD, causes vasoconstriction, increased vascular resistance and pulmonary hypertension. Hypoxia-induced changes in endothelial function play a central role in the development of this pulmonary hypertension. However, the direct interactive effects of hypoxia and shear stress on the pulmonary endothelial phenotype have not been extensively studied. We cultured human pulmonary microvascular endothelial cells (HPMEC) in normoxia or hypoxia while subjected to physiological shear stress or in static conditions. Unbiased proteomics was used to identify hypoxia-induced changes in protein expression. Using publicly available single cell RNA-seq datasets, differences in gene expression between the alveolar endothelial cells from COPD and healthy lungs were identified. 60 proteins were identified in HPMEC lysates whose expression changed in response to hypoxia in sheared but not in static conditions. mRNA for five of these (ERG, MCRIP1, EIF4A2, HSP90AA1 and DNAJA1) showed similar changes in the endothelial cells of COPD compared to healthy lungs. These data show that the proteomic responses of the pulmonary microvascular endothelium to hypoxia are significantly altered by shear stress and suggest that these differences are important in the development of hypoxic pulmonary vascular disease.
Project description:Laminar shear stress due to constant blood flow is known to play a critical role in maintaining vascular health. In contrast, endothelial cell senescence appears to be closely associated with the incidence of vascular disorder. In an attempt to identify functional biomarkers for age-related vascular health/disease, the present study investigated differential gene expression of young and senescent human umbilical vein endothelial cells (HUVECs) under static and laminar shear stress. We used a cDNA microarray method to compare gene expression profiles of young and senescent HUVECs under static and laminar shear stress conditions. Keywords: stress response, age state analysis
Project description:Laminar shear stress due to constant blood flow is known to play a critical role in maintaining vascular health. In contrast, endothelial cell senescence appears to be closely associated with the incidence of vascular disorder. In an attempt to identify functional biomarkers for age-related vascular health/disease, the present study investigated differential gene expression of young and senescent human umbilical vein endothelial cells (HUVECs) under static and laminar shear stress. We used a cDNA microarray method to compare gene expression profiles of young and senescent HUVECs under static and laminar shear stress conditions. Experiment Overall Design: Senescent cells were prepared by continuous subculture in vitro, and a cone-and-plate device was used to impose laminar shear stress onto cells. Young and senescent cells were exposed to laminar shear stress or maintained under static conditions. Total mRNA was extracted and gene expression profiles were analyzed by cDNA microarray.
Project description:The mechanisms by which physical forces regulate cells to determine complexities of vascular structure and function are enigmatic. Here we show the role the ion channel subunit Piezo1 (FAM38A). Disruption of mouse Piezo1 gene disturbed vascular development and was embryonic lethal within days of the heart beating to cause blood flow. Importance of Piezo channels as sensors of blood flow was indicated by Piezo1 dependence of shear stress-evoked ionic current and calcium influx in endothelial cells and the ability of exogenous Piezo1 to confer shear stress sensitivity on cells that otherwise lacked. Downstream of this calcium influx was proteoase activity and spatial organization of endothelial cells to the polarity of the applied force. Without Piezo1, normal endothelial cell organization was lacking. The data suggest Piezo1 channels as pivotal integrators of vascular architacture with physiological mechanical force.
Project description:The objective of this study was to advance the understanding of how in vivo arterial shear forces affect vascular endothelial gene expression. Complicated blood flow patterns at arterial branches create small regions that experience fluctuations in shear stress at frequencies higher than the heart rate. To assess whether such temporal variations in shear stress can affect endothelial gene expression, a series of in vitro microarray experiments was performed. The effects of three sinusoidal waveforms (1, 2, and 3 Hz) and one physiological waveform were compared to the expression profiles under steady flow. At each frequency, three levels of mean shear stress (0, 7.5, and 15 dyn/cm2) were used. Porcine aortic endothelial cells were exposed for 24 hours to each combination, replicated four times. Following shear exposure, phase contrast images of the cells were acquired, and RNA was extracted for microarray analysis against about 10,000 porcine oligonucleotides. Cell alignment with the flow was positively correlated with mean shear (p < 0.001) and independent of frequency. A two-way ANOVA identified 232 genes that were differentially regulated by frequency. The frequency sensitive genes were clustered to identify groups of genes exhibiting similar frequency responses. The largest response was seen at 2 Hz. At this frequency, several inflammatory molecules were upregulated, including VCAM, CTGF, TGF-beta2, c-jun, and IL-8, indicating a potential endothelial atherosusceptibility at this frequency. Mean shear significantly affected the expression of ~3,000 genes. Purely oscillatory flow (zero mean shear) enhanced the expression of several growth factors and adhesion molecules (E-selectin, VCAM, MCP-1, IL-8, c-jun), relative to non-reversing flow (15 dyn/cm2 mean shear). The 2 Hz upregulation of certain atherogenic molecules such as VCAM, c-jun, and IL-8 was enhanced as the mean shear was reduced. Thus, the inflammatory response evoked at certain frequencies appears to be exacerbated by low, oscillatory shear. Keywords: Shear stress response
Project description:The role of shear stress, the frictional force of blood flow, on the endothelium has been well documented. Differences in shear stress can have profound effects on endothelial and blood vessel biology. Endothelial cells (ECs), termed endocardial ECs, line the heart chambers and are exposed to complex shear stress patterns. While it has been demonstrated that shear stress is important for heart development, little has been shown on the role of shear stress on adult ECs. 4D-MRI studies demonstrate regional differences in blood residence time. We sought to determine the effect of regional differences in endocardial shear stress on the endocardial transcriptome using RNA sequencing (RNA-seq) on 3 different regions (apex, mid-ventricle, outflow tract) from 8 adult pigs, for a total of 24 RNA-seq assays.
Project description:Laminar shear stress regulates blood vessel morphogenesis and subsequent quiescence, but how endothelial cells (EC) enact and maintain the vascular homeostasis required in most vessels for proper vessel function is poorly understood. SMAD6, a scaffold for several signaling pathways, is expressed in developing arteries and its expression is flow-regulated. We found that SMAD6 is essential for endothelial cell flow-mediated responses, and that it functions downstream of the mechanosensor Notch1. Endothelial cells with reduced SMAD6 levels failed to align under stable laminar shear flow that promotes vascular homeostasis, while forced SMAD6 expression rescued misalignment induced by reduced Notch1 signaling. SMAD6-dependent homeostatic laminar flow required the Notch ligand Dll4 and Notch transcriptional activity. Mechanistically, neither the N-terminal nor the C-terminal domain of SMAD6 alone rescued flow alignment upon loss of Notch signaling. Endothelial cells with reduced Smad6 levels has compromised barrier function, and RNA profiling revealed upregulation of proliferation-associated genes and down regulation of junction-associated genes. Among junction-related genes affected by SMAD6 levels, the proto-cadherin PCDH12 was upregulated by homeostatic flow and required for proper flow-mediated endothelial cell alignment. Thus, SMAD6 is a critical integrator of flow-mediated signaling inputs downstream of Notch1, as vessels transition from an angiogenic to a homeostatic phenotype.
Project description:The study shows transcriptional and chromatin changes in human umbilical cord endothelial cells (HUVEC) exposed to shear stress. In addition transcriptional changes in zebrafish endothelial cells in response to blood flow block are shown
Project description:The lymphatic system removes fluid from the interstitial space and returns it to the blood with a tremendous capacity: during inflammation, lymph flow rates can increase dramatically; however, during chronic lymphedema, there is little or no flow. The ability of lymphatic endothelium to sense and actively regulate this function is unknown, and shear stress is likely a key indicator of lymph flow. We profiled gene expression in human dermal microvascular lymphatic endothelial cells exposed to 0, 2 and 20 dyn/cm2 shear stress as representative of chronic lymphedema, normal, and acute inflammatory conditions, respectively. We found important adaptive responses correlated to multiple aspects of lymphatic function. Importantly, shear stress upregulated intracellular water and solute transporters while decreasing cell-cell adhesion and basement membrane components and increasing cell-matrix interactions. This data indicate that during high loading conditions, both passive and active drainage function increases, while conversely when fluid drainage is blocked, transport function is diminished in the lymphatic endothelium. These data demonstrate the first functional-adaptive response of lymphatic endothelium to flow conditions, thus indicating that the lymphatic endothelium plays an active role in regulating their function. Keywords: Shear stress, dose response, cell type comparison Lymphatic endothelial cells were subjected to 0, 2, or 20 dyn/cm2 shear stress; blood endothelial cells were subjected to 0 or 20 dyn/cm2 shear stress. Four samples were used for each cell type/shear level group for a total of 20 samples. Each sample was independently compared to human universal reference RNA via two-color microarray analysis for a total of 20 arrays. In all cases, the experimental samples were labeled with Cy5 dye while the reference RNA was labeled with Cy3.
Project description:The arterial endothelium’s response to its flow environment is critical to vascular homeostasis. The endothelial glycocalyx has been shown to play a major role in mechanotransduction, but the extent to which the components of the glycocalyx affect the overall function of the endothelium remains unclear. The objective of this study was to further elucidate the role of heparan sulfate as a mechanosensor on the surface of the arterial endothelium, by (1) expanding the variety of shear waveforms investigated, (2) continuously suppressing heparan sulfate expression rather than using a pre-flow batch treatment, and (3) performing microarray analysis on post-flow samples. Porcine aortic endothelial cells were exposed to non-reversing, reversing, and oscillatory shear waveforms for 24 hours with or without continuous heparan sulfate suppression with heparinase. All shear waveforms significantly increased the amount of heparan sulfate on the surface of the endothelium. Suppression of heparan sulfate to less than 25% of control levels did not inhibit shear-induced cell alignment or nitric oxide production, or alter gene expression, for any of the shear waveforms investigated. We infer that heparan sulfate on the surface of porcine aortic endothelial cells is not the primary mechanosensor for many shear-responsive endothelial cell functions in this species. Porcine aortic endothelial cells were exposed to 3 different shear waveforms for 24 hours with or without the addition of 300 mU/ml heparinase III to the flow media. The shear waveforms inculded Non-reversing (15 ± 15 dyne/cm2, 1 Hz), Steady (15 dyne/cm2), or Oscillatory (0 ± 15 dyne/cm2, 1 Hz) shear. Four replicates of each condition were performed for a total of 24 experiments. Each experimental sample was hybridized to an oligonucleotide array along with a standard reference sample (static cells).