Angiogenesis plays a critical role in the revascularization of ischemic organs and in the progression of cancer, atherosclerosis, rheumatoid arthritis, and diabetic retinopathy. The outcome of angiogenesis depends on neovessel survival. Developing vessels uses the angiopoietin/Tie2 system to acquire a stabilizing layer of mural cells (smooth muscle cells/pericytes). The mechanisms regulating this process are, however, poorly understood because the Tie2 receptor is reportedly expressed in endothelial cells but not in mural cells. Using the rat aorta model of angiogenesis we found that Tie2 is transiently expressed in intimal- derived mesenchymal cells that have the capacity to differently into mural cells. Tie2+ mural precursor cells migrate and secrete matrix metalloproteinases in response to Ang-1 which they produce, and Ang-2, which is produced by endothelial cells. Based on the additional observation that the intimal/subintimal layers of the rat aorta contain Flk- 1+ and Tie2+ non-endothelial mesenchymal cells and have angioinformative properties we postulate that Tie2+ mural-precursor cells arise from vascular progenitor cells capable of both endothelial and mural cell differentiation. We linked mural cell recruitment to the p38 MAPK signaling pathway by demonstrating that pharmacologic inhibition of p28, which is activated upon Tie2 stimulation, abrogates mural cell development resulting in naked neovessels. Based on these observations the specific aims of this grant focus on the following hypotheses. 1) The aortic wall. contains vascular progenitor cells capable of both endothelial and mural cell differentiation. 2. The muscular wall of blood vessels originates from Tie2+ mural precursor cells. 3. Mural cell recruitment during angiogenesis is selectively mediated by the p38 MAPK pathway. Vascular progenitor cells of neonatal, young and old rat aortas will be identified by immunohistochemistry and confocal microscopy and isolated by surface marker-based magnetic beads technology. Their angioformative and mural cell differentiation properties will be studied in models of vascular organ culture, microvessel assembly and chemotaxis. The role of Tie2 and p38 MAPK pathway in mural cell recruitment will be studied by gene transfer technology using adeno-associated viral vectors carrying wild type or dominant-negative genes Mural cell recruitment will be analyzed by Immunohistochemistry, confocal microscopy and image analysis. Gene/protein expression and function will be evaluated by Northern and Western analysis, RT-PCR, kinase assays, gel zymography, in situ hybridization, and immunohistochemistry,. These studies will define key cellular and molecular mechanisms of vessel wall development. This knowledge may lead to novel approaches for the stabilization of neovessels in ischemic conditions, the induction of vascular regression in angiogenesis-dependent disorders, and the bioengineering of blood vessels for therapeutic applications.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL052585-09
Application #
6717723
Study Section
Pathology A Study Section (PTHA)
Program Officer
Goldman, Stephen
Project Start
1995-04-01
Project End
2006-03-31
Budget Start
2004-04-01
Budget End
2005-03-31
Support Year
9
Fiscal Year
2004
Total Cost
$252,000
Indirect Cost
Name
University of Washington
Department
Pathology
Type
Schools of Medicine
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
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
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
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
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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