This new application addresses an important question in vascular biology which concerns how newly formed endothelial cell (EC)-lined tubes are stabilized. We have developed excellent models of this process in vitro and have identified key mechanisms and molecules, which are required for these events. EC-derived proteinases such as MMP-1 are capable of degrading 3D collagen matrices during tubular morphogenesis, which destabilizes tubes and induces regression. We hypothesize that EC supporting cells such as pericytes present proteinase inhibitors such as TIMP-3 and RECK which blocks the natural tendency of ECs during angiogenesis to degrade the extracellular matrix environment in which they are suspended. These pericyte-derived inhibitors likely represent new molecules that are critical to the stabilization of newly formed tubes. Preliminary data shows that TIMP-3 is unique in that it can completely inhibit EC tubular morphogenesis as well as stabilize EC-lined tubes. Furthermore, TIMP-3 is heavily expressed by primary cultures of pericytes and is not expressed by ECs. Inclusion of vascular smooth muscle cells (also express TIMP-3) with ECs in 3D models of MMP-1-dependent tube regression completely blocks the process by interfering with MMP-1 proenzyme activation. We will utilize a balanced experimental approach to determine the role of pericyte-derived proteinase inhibitors in EC tube stabilization in vitro and in vivo (using recombinant adenoviral gene delivery and TIMP-3 knockout mice). The mechanisms involved in how pericytes stabilize EC tubes during angiogenesis and vascular development remain unknown and this proposal will directly test the novel hypothesis that proteinase inhibitors are key molecules regulating these events.
The specific aims of this application are;
Aim #1. To investigate the primary mechanisms and molecules (i.e. proteinase inhibitors and growth factors) which regulate the ability of pericytes/vascular smooth muscle cells to induce capillary tube stabilization in vitro and in vivo.
Aim #2. To investigate the molecular mechanism by which TIMP-3 regulates capillary tube stabilization in vitro and in vivo through complete inhibition of EC invasion and lumen development during tubular morphogenesis in three-dimensional matrices.
Aim #3. To investigate the ability of human matrix metalloproteinase-1 (MMP-1) as well as mouse interstitial collagenases (e.g. MMP-13) to directly control capillary tube regression events in vitro and in vivo.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Vascular Cell and Molecular Biology Study Section (VCMB)
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Goldman, Stephen
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University of Missouri-Columbia
Schools of Medicine
United States
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Davis, George E; Kim, Dae Joong; Meng, Chun-Xia et al. (2013) Control of vascular tube morphogenesis and maturation in 3D extracellular matrices by endothelial cells and pericytes. Methods Mol Biol 1066:17-28
Stratman, Amber N; Davis, George E (2012) Endothelial cell-pericyte interactions stimulate basement membrane matrix assembly: influence on vascular tube remodeling, maturation, and stabilization. Microsc Microanal 18:68-80
Sacharidou, Anastasia; Stratman, Amber N; Davis, George E (2012) Molecular mechanisms controlling vascular lumen formation in three-dimensional extracellular matrices. Cells Tissues Organs 195:122-43
Davis, George E (2011) Angiogenesis and Proteinases: Influence on Vascular Morphogenesis, Stabilization and Regression. Drug Discov Today Dis Models 8:13-20
Senger, Donald R; Davis, George E (2011) Angiogenesis. Cold Spring Harb Perspect Biol 3:a005090
Davis, George E; Stratman, Amber N; Sacharidou, Anastasia et al. (2011) Molecular basis for endothelial lumen formation and tubulogenesis during vasculogenesis and angiogenic sprouting. Int Rev Cell Mol Biol 288:101-65
Stratman, Amber N; Davis, Michael J; Davis, George E (2011) VEGF and FGF prime vascular tube morphogenesis and sprouting directed by hematopoietic stem cell cytokines. Blood 117:3709-19
Stratman, Amber N; Schwindt, Amy E; Malotte, Kristine M et al. (2010) Endothelial-derived PDGF-BB and HB-EGF coordinately regulate pericyte recruitment during vasculogenic tube assembly and stabilization. Blood 116:4720-30
Davis, George E (2010) Matricryptic sites control tissue injury responses in the cardiovascular system: relationships to pattern recognition receptor regulated events. J Mol Cell Cardiol 48:454-60
Sacharidou, Anastasia; Koh, Wonshill; Stratman, Amber N et al. (2010) Endothelial lumen signaling complexes control 3D matrix-specific tubulogenesis through interdependent Cdc42- and MT1-MMP-mediated events. Blood 115:5259-69

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