Project description:Intracranial aneurysms tend to form at bifurcation apices, where flow impingement causes high frictional force (or wall shear stress, WSS) and flow acceleration and deceleration that create positive and negative streamwise gradients in WSS (WSSG), respectively. In vivo, intracranial aneurysms initiate under high WSS and positive WSSG. Little is known about the responses of endothelial cells (ECs) to either positive or negative WSSG under high WSS conditions. We used cDNA microarrays to profile EC gene expression exposed to positive WSSG vs. negative WSSG for 24 hours in a flow chamber with converging and diverging channels, respectively. WSS varied between 3.5 and 28.4 Pa in each gradient channel. GO and biological pathway analysis indicated that positive WSSG favored proliferation, apoptosis, and extracellular matrix processing while decreasing expression of pro-inflammatory genes. A subset of characteristic genes was validated using qPCR: Genes for ADAMTS1, CKAP2 and NCEH1 had higher expression under positive WSSG compared to negative WSSG while TAGLN, THBS1, VCAM1, CCL2, and CSF2 had lower expression. To determine if these patterns of expression are also exhibited in vivo, we tested whether the extracellular matrix related protein ADAMTS1 and proliferation were modulated by positive WSSG during intracranial aneurysm initiation. An aneurysm was induced at the basiliar terminus in rabbits by bilateral carotid ligation. WSSG at the bifurcation was determined by computational fluid dynamic simulations from 3D angiography and mapped on immunofluorescence staining for ADAMTS1 and the proliferation marker, Ki-67. Endothelial ADAMTS1 protein and Ki-67 were significantly higher in regions with positive WSSG compared to adjacent sites where WSSG was negative. Our results indicate that WSSG can elicit distinct gene expression profiles in ECs. Increased matrix processing and high levels of proliferation under positive WSSG could contribute to intracranial aneurysm initiation by causing transient gaps in the endothelium or disrupting EC signals to smooth muscle cells. Time-matched bovine aortic endothelial cells were exposed to positive wall shear stress gradient, negative wall shear stress gradient, and two no gradient samples: uniform WSS of 3.5 Pa and high WSS of 28.4 Pa for 24 hrs in an in vitro flow loop system. RNA was extracted and hybridized on Affymetrix microarrays. There were 12 samples in total, four flow conditions with three replicates each.

Project description:Intracranial aneurysms tend to form at bifurcation apices, where flow impingement causes high frictional force (or wall shear stress, WSS) and flow acceleration and deceleration that create positive and negative streamwise gradients in WSS (WSSG), respectively. In vivo, intracranial aneurysms initiate under high WSS and positive WSSG. Little is known about the responses of endothelial cells (ECs) to either positive or negative WSSG under high WSS conditions. We used cDNA microarrays to profile EC gene expression exposed to positive WSSG vs. negative WSSG for 24 hours in a flow chamber with converging and diverging channels, respectively. WSS varied between 3.5 and 28.4 Pa in each gradient channel. GO and biological pathway analysis indicated that positive WSSG favored proliferation, apoptosis, and extracellular matrix processing while decreasing expression of pro-inflammatory genes. A subset of characteristic genes was validated using qPCR: Genes for ADAMTS1, CKAP2 and NCEH1 had higher expression under positive WSSG compared to negative WSSG while TAGLN, THBS1, VCAM1, CCL2, and CSF2 had lower expression. To determine if these patterns of expression are also exhibited in vivo, we tested whether the extracellular matrix related protein ADAMTS1 and proliferation were modulated by positive WSSG during intracranial aneurysm initiation. An aneurysm was induced at the basiliar terminus in rabbits by bilateral carotid ligation. WSSG at the bifurcation was determined by computational fluid dynamic simulations from 3D angiography and mapped on immunofluorescence staining for ADAMTS1 and the proliferation marker, Ki-67. Endothelial ADAMTS1 protein and Ki-67 were significantly higher in regions with positive WSSG compared to adjacent sites where WSSG was negative. Our results indicate that WSSG can elicit distinct gene expression profiles in ECs. Increased matrix processing and high levels of proliferation under positive WSSG could contribute to intracranial aneurysm initiation by causing transient gaps in the endothelium or disrupting EC signals to smooth muscle cells.

Project description:Objective: The vulnerability of atherosclerotic plaques is among the leading cause of ischemic stroke. High wall shear stress (WSS) promotes the instability of atherosclerotic plaques by directly imparting mechanical stimuli, but the specific mechanisms remain unclear. We speculate that modulation of mechanosensitive genes may play a vital role in accelerating the development of plaques. The purpose of this study was to find mechanosensitive genes in vascular endothelial cells (ECs) through combining microarray data with bioinformatics technology and further explore the underlying dynamics-related mechanisms that cause the progression and destabilization of atherosclerotic plaques. Methods: Microarray data sets for human vascular ECs under high and normal WSS were retrieved from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified through the R language. The performance of enrichment analysis and protein-protein interaction (PPI) network presented the biological function and signaling pathways of the DEGs. Hub genes were identified based on the PPI network and validated by GEO data sets. Predicted transcription factor (TF) genes and miRNAs interaction with potential mechanosensitive genes were identified by NetworkAnalyst. Results: A total of 260 DEGs, 121 upregulated and 139 downregulated genes, were screened between high and normal WSS from GSE23289. A total of 10 hub genes and four cluster modules were filtered out based on the PPI network. The enrichment analysis showed that the biological functions of the hub genes were mainly involved in responses to unfolded protein and topologically incorrect protein, and t to endoplasmic reticulum stress. The significant pathways associated with the hub genes were those of protein processing in the endoplasmic reticulum, antigen processing, and presentation. Three out of the 10 hub genes, namely, activated transcription factor 3 (ATF3), heat shock protein family A (Hsp70) member 6 (HSPA6), and dual specificity phosphatase 1 (DUSP1, also known as CL100, HVH1, MKP-1, PTPN10), were verified in GSE13712. The expression of DUSP1 was higher in the senescent cell under high WSS than that of the young cell. The TF-miRNA-mechanosensitive gene coregulatory network was constructed. Conclusion: In this work, we identified three hub genes, ATF3, HSPA6, and DUSP1, as the potential mechanosensitive genes in the human blood vessels. DUSP1 was confirmed to be associated with the senescence of vascular ECs. Therefore, these three mechanosensitive genes may have emerged as potential novel targets for the prediction and prevention of ischemic stroke. Furthermore, the TF-miRNA-mechanosensitive genes coregulatory network reveals an underlying regulatory mechanism and the pathways to control disease progression.

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Lymphatic endothelial cell calcium pulses are sensitive to spatial gradients in wall shear stress.

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Lymphatic endothelial cell calcium pulses are sensitive to spatial gradients in wall shear stress.

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