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Fluid forces control endothelial sprouting.

ABSTRACT: During angiogenesis, endothelial cells (ECs) from intact blood vessels quickly infiltrate avascular regions via vascular sprouting. This process is fundamental to many normal and pathological processes such as wound healing and tumor growth, but its initiation and control are poorly understood. Vascular endothelial cell growth factor (VEGF) can promote vessel dilation and angiogenic sprouting, but given the complex nature of vascular morphogenesis, additional signals are likely necessary to determine, for example, which vessel segments sprout, which dilate, and which remain quiescent. Fluid forces exerted by blood and plasma are prime candidates that might codirect these processes, but it is not known whether VEGF cooperates with mechanical fluid forces to mediate angiogenesis. Using a microfluidic tissue analog of angiogenic sprouting, we found that fluid shear stress, such as exerted by flowing blood, attenuates EC sprouting in a nitric oxide-dependent manner and that interstitial flow, such as produced by extravasating plasma, directs endothelial morphogenesis and sprout formation. Furthermore, positive VEGF gradients initiated sprouting but negative gradients inhibited sprouting, promoting instead sheet-like migration analogous to vessel dilation. These results suggest that ECs integrate signals from fluid forces and local VEGF gradients to achieve such varied goals as vessel dilation and sprouting.

SUBMITTER: Song JW

PROVIDER: S-EPMC3174629 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Fluid forces control endothelial sprouting.

Song Jonathan W JW Munn Lance L LL

Proceedings of the National Academy of Sciences of the United States of America 20110829 37

During angiogenesis, endothelial cells (ECs) from intact blood vessels quickly infiltrate avascular regions via vascular sprouting. This process is fundamental to many normal and pathological processes such as wound healing and tumor growth, but its initiation and control are poorly understood. Vascular endothelial cell growth factor (VEGF) can promote vessel dilation and angiogenic sprouting, but given the complex nature of vascular morphogenesis, additional signals are likely necessary to dete ...[more]

PMID: 21876168

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Project description:Branching from conduits is a defining feature of the gas delivery systems of invertebrates (tracheae built from epithelial cells) and vertebrates (vasculature lined by endothelial cells). Here, we show that the vertebrate transcriptional repressor Tel plays an evolutionarily conserved role in angiogenesis: it is indispensable for sprouting of primary human endothelial cells and for the normal development of the Danio rerio embryo blood circulatory system. Tel controls endothelial sprouting via binding to the generic co-repressor C-terminal binding protein (CtBP). In endothelial cells, the Tel:CtBP complex temporally restricts a VEGF-mediated pulse of dll4 expression and consequently integrates VEGFR intracellular signaling and intercellular Notch-Dll4 signaling. It further refines branching by regulating expression of other factors that constrain angiogenesis such as sprouty family members and ve-cadherin. Thus, the Tel:CtBP complex moderates the balance between positive and antagonistic angiogenesis cues and thereby conditions endothelial cells for angiogenesis. Since the activity of CtBP is attuned to intracellular NADH levels, our results raise the possibility that Tel-mediated sprouting could be sensitized to the metabolic status of the tissue. Tel control of branching appears to be evolutionarily conserved since Yan, the invertebrate orthologue of Tel, is similarly required for branching morphogenesis of the invertebrate tracheae. Collectively, our work suggests that Tel is a central regulator of angiogenesis and highlights Tel and its associated networks as potential targets for the development of therapeutic strategies to inhibit pathological angiogenesis. 2 independent screens were performed testing effects of knockdown of Tel or CtBP (screen 1) or effects of VEGF-A (screen 2) on Human Umbilical Vein Endothelial Cells (HUVECs). For screen 1 we tested 3 different conditions. We established stable HUVEC cell lines which were either infected with control lentivirus (Mock), or lentivirus expressing short hairpin RNA constructs for the specific knockdown of Tel(Teli) or CtBP2 (CtBP2i). Expression in the Teli and CtBP2i cell lines was compared to expression in the Mock cell line for screen 1. For screen 2 we tested 2 conditions. We exposed HUVECs to VEGF (50ng/mL) for 30 minutes (samplename: VEGF30) and compared the transcriptome of these cells to untreated HUVECs (VEGF0). For each condition 2 independent repeats were analyzed and expression of genes was averaged for each repeat. HUVECs were grown under standard conditions (37degrees Celsius, 5% CO2) in EGM2 medium (Lonza).

Dataset Information

Fluid forces control endothelial sprouting.

Publications

Fluid forces control endothelial sprouting.

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