Angiogenesis, the formation of new blood vessels by endothelial cells, plays a critical role in wound healing, the revascularization of ischemic organs, and the progression of atherosclerosis and cancer. The basic theme of this grant is that periendothelial mural cells regulate angiogenesis by paracrine mechanisms. Our previous work focused on the role of the mural cell-derived product angiopoietin-1 (Ang-1) and its receptor Tie2 in the aortic ring model of injury-induced angiogenesis. The following novel findings emerged from these studies. 1. Ang-1 induces expression of tumor necrosis factor-alpha (TNF) and other immune-related cytokines/chemokines, which stimulate macrophage recruitment and angiogenesis. 2. TNF is required for the angiogenic activity of Ang-1-induced cytokines. 3. Ang-1-mediated mural cell recruitment can be inhibited by blocking the p38 MARK pathway, which regulates production of monocyte chemotactic protein-1 (MCP-1), a mural cell stimulatory chemokine induced by Ang-1. 4. Ang-1 promotes expression of Toll-like receptor-2 (TLR2) and the TLR4 adapter molecule CD14, which regulate cytokine production in the innate immune system. 5. Stimulation of TLR2 with specific ligands dose-dependently promotes angiogenesis. 6. The angiogenic response of the aortic wall is impaired in mice with disrupted MyD88, a key TLR signaling molecule. On this basis we formulated the hypothesis that Ang-1 regulates angiogenesis in response to injury by cooperating with the innate immune system.
Specific aims : (1) To establish the role of vascular macrophages and their cytokine product TNF in Ang-1-mediated angiogenesis. (2) To define the role of MCP-1 in Ang-1/p38 MAPK-mediated mural cell recruitment during angiogenesis. (3) To determine the function of TLRs in the angiogenic response of the vessel wall. For these studies we will use rat and mouse in vitro and in vivo models of angiogenesis. Functional studies will be performed with neutralizing antibodies and genetically modified mice with defective TNF and TLR systems. Macrophages will be selectively ablated using biochemical and transgenic methods. Molecular studies will include real-time RT-PCR, ELISA, laser capture microscopy, and confocal microscopy. Proposed experiments will define new molecular mechanisms of angiogenesis and vessel wall assembly. This knowledge may provide novel insights for the development of therapeutic approaches aimed at treating angiogenesis-dependent disorders and ischemic conditions.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Atherosclerosis and Inflammation of the Cardiovascular System Study Section (AICS)
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Gao, Yunling
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University of Washington
Schools of Medicine
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Aplin, Alfred C; Ligresti, Giovanni; Fogel, Eric et al. (2014) Regulation of angiogenesis, mural cell recruitment and adventitial macrophage behavior by Toll-like receptors. Angiogenesis 17:147-61
Fang, Changge; Avis, Ingalill; Bianco, Caterina et al. (2013) SCNH2 is a novel apelinergic family member acting as a potent mitogenic and chemotactic factor for both endothelial and epithelial cells. Open J Clin Diagn 3:37-51
Ligresti, Giovanni; Aplin, Alfred C; Dunn, Bruce E et al. (2012) The acute phase reactant orosomucoid-1 is a bimodal regulator of angiogenesis with time- and context-dependent inhibitory and stimulatory properties. PLoS One 7:e41387
Ligresti, Giovanni; Aplin, Alfred C; Zorzi, Penelope et al. (2011) Macrophage-derived tumor necrosis factor-alpha is an early component of the molecular cascade leading to angiogenesis in response to aortic injury. Arterioscler Thromb Vasc Biol 31:1151-9
Nicosia, Roberto F; Zorzi, Penelope; Ligresti, Giovanni et al. (2011) Paracrine regulation of angiogenesis by different cell types in the aorta ring model. Int J Dev Biol 55:447-53
Zorzi, Penelope; Aplin, Alfred C; Smith, Kelly D et al. (2010) Technical Advance: The rat aorta contains resident mononuclear phagocytes with proliferative capacity and proangiogenic properties. J Leukoc Biol 88:1051-9
Aplin, Alfred C; Fogel, Eric; Nicosia, Roberto F (2010) MCP-1 promotes mural cell recruitment during angiogenesis in the aortic ring model. Angiogenesis 13:219-26
Nicosia, R F (2009) The aortic ring model of angiogenesis: a quarter century of search and discovery. J Cell Mol Med 13:4113-36
Aplin, A C; Zhu, W H; Fogel, E et al. (2009) Vascular regression and survival are differentially regulated by MT1-MMP and TIMPs in the aortic ring model of angiogenesis. Am J Physiol Cell Physiol 297:C471-80
David Dong, Zhao Ming; Aplin, Alfred C; Nicosia, Roberto F (2009) Regulation of angiogenesis by macrophages, dendritic cells, and circulating myelomonocytic cells. Curr Pharm Des 15:365-79

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