David A. Dichek
University of Washington
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Featured researches published by David A. Dichek.
Circulation Research | 2009
Mei Y. Speer; Hsueh Ying Yang; Thea Brabb; Elizabeth M. Leaf; Amy Look; Wei Ling Lin; Andrew D. Frutkin; David A. Dichek; Cecilia M. Giachelli
Vascular calcification is a major risk factor for cardiovascular morbidity and mortality. To develop appropriate prevention and/or therapeutic strategies for vascular calcification, it is important to understand the origins of the cells that participate in this process. In this report, we used the SM22-Cre recombinase and Rosa26-LacZ alleles to genetically trace cells derived from smooth muscle. We found that smooth muscle cells (SMCs) gave rise to osteochondrogenic precursor- and chondrocyte-like cells in calcified blood vessels of matrix Gla protein deficient (MGP−/−) mice. This lineage reprogramming of SMCs occurred before calcium deposition and was associated with an early onset of Runx2/Cbfa1 expression and the downregulation of myocardin and Msx2. There was no change in the constitutive expression of Sox9 or bone morphogenetic protein 2. Osterix, Wnt3a, and Wnt7a mRNAs were not detected in either calcified MGP−/− or noncalcified wild-type (MGP+/+) vessels. Finally, mechanistic studies in vitro suggest that Erk signaling might be required for SMC transdifferentiation under calcifying conditions. These results provide strong support for the hypothesis that adult SMCs can transdifferentiate and that SMC transdifferentiation is an important process driving vascular calcification and the appearance of skeletal elements in calcified vascular lesions.
Circulation Research | 2004
Hideaki Moriwaki; April Stempien-Otero; Michal Kremen; Aaron E. Cozen; David A. Dichek
Several studies implicate elevated matrix metalloproteinase activity as a cause of cardiac fibrosis. However, it is unknown whether other proteases can also initiate cardiac fibrosis. Because absence of urokinase plasminogen activator (uPA) prevents development of cardiac fibrosis after experimental myocardial infarction in mice, we hypothesized that elevated activity of uPA or deficiency of the uPA inhibitor plasminogen activator inhibitor-1 (PAI-1) might cause cardiac fibrosis. We used mice with scavenger-receptor (SR)-directed, macrophage-targeted uPA overexpression (SR-uPA+/0 mice) and PAI-1 null mice to test these hypotheses. Our studies revealed that SR-uPA+/0 mice developed cardiac fibrosis beginning between 5 and 10 weeks of age. Fibrosis was preceded by cardiac macrophage accumulation, implicating uPA-secreting macrophages as important contributors to development of fibrosis. A key role for uPA-secreting macrophages in development of cardiac fibrosis was supported by experiments in which recipients of bone marrow transplants from SR-uPA+/0 donors but not nontransgenic donors developed cardiac macrophage accumulation and fibrosis. SR-uPA+/0 mice and recipients of SR-uPA+/0 bone marrow had neither macrophage accumulation nor fibrosis in other major organs despite the presence of higher levels of uPA in these organs than in hearts. PAI-1 null mice but not congenic, age-matched controls also developed macrophage accumulation and fibrosis in hearts but not in other organs. We conclude: (1) either elevated macrophage uPA expression or PAI-1 deficiency is sufficient to cause cardiac macrophage accumulation and fibrosis; (2) macrophages are important contributors to the development of cardiac fibrosis; and (3) the heart is particularly sensitive to the effects of excess uPA activity.
Circulation | 2004
Aaron E. Cozen; Hideaki Moriwaki; Michal Kremen; Mary Beth DeYoung; Helén L. Dichek; Katherine I. Slezicki; Stephen Young; Murielle Véniant; David A. Dichek
Background—Human atherosclerotic lesions contain elevated levels of urokinase plasminogen activator (uPA), expressed predominantly by macrophages. Methods and Results—To test the hypothesis that macrophage-expressed uPA contributes to the progression and complications of atherosclerosis, we generated transgenic mice with macrophage-targeted overexpression of uPA. The uPA transgene was bred into the apolipoprotein E–null background, and transgenic mice and nontransgenic littermate controls were fed an atherogenic diet. uPA-transgenic mice had significantly elevated uPA activity in the atherosclerotic artery wall, of a magnitude similar to elevations reported in atherosclerotic human arteries. Compared with littermate controls, uPA-transgenic mice had accelerated atherosclerosis, dilated aortic roots, occlusive proximal coronary artery disease, myocardial infarcts, and early mortality. Conclusions—These data support the hypothesis that overexpression of uPA by artery wall macrophages is atherogenic and suggest that uPA inhibitors might be therapeutically useful.
Arteriosclerosis, Thrombosis, and Vascular Biology | 2006
Goro Otsuka; Ramtin Agah; Andrew D. Frutkin; Thomas N. Wight; David A. Dichek
Objective—The mechanisms through which transforming growth factor (TGF)-&bgr;1 promotes intimal growth, and the pathways through which TGF-&bgr;1 expression is regulated in the artery wall, are incompletely understood. We used a mouse model to investigate mechanisms of TGF-&bgr;1–induced intimal growth. Methods and Results—Adenovirus-mediated overexpression of TGF-&bgr;1 in uninjured carotid arteries of wild-type mice induced formation of a cellular and matrix-rich intima. Intimal growth appeared primarily due to cell migration and matrix accumulation, with only a negligible contribution from cell proliferation. Overexpression of TGF-&bgr;1 also stimulated expression of plasminogen activator inhibitor type 1 (plasminogen activator inhibitor [PAI]-1) in the artery wall. To test the hypothesis that PAI-1 is a critical downstream mediator of TGF-&bgr;1–induced intimal growth, we transduced carotid arteries of PAI-1–deficient (Serpine1−/−) mice with the TGF-&bgr;1–expressing vector. Overexpression of TGF-&bgr;1 in Serpine1−/− arteries did not increase intimal growth, matrix accumulation, cell migration, or proliferation. Moreover, TGF-&bgr;1–transduced arteries of Serpine1−/− mice secreted 6- to 10-fold more TGF-&bgr;1 than did arteries of wild-type mice that were infused with the same concentration of the TGF-&bgr;1–expressing vector. Conclusions—PAI-1 is both a critical mediator of TGF-&bgr;1–induced intimal growth and a key negative regulator of TGF-&bgr;1 expression in the artery wall.
Proceedings of the National Academy of Sciences of the United States of America | 2002
Mårten Falkenberg; Clifford Tom; Mary Beth DeYoung; Shan Wen; Ruth Linnemann; David A. Dichek
Overexpression of urokinase plasminogen activator (uPA) in endothelial cells can decrease intravascular thrombosis. However, expression of uPA is increased in atherosclerotic human arteries, which suggests that uPA might accelerate atherogenesis. To investigate whether elevated uPA expression accelerates atherogenesis, we cloned a rabbit uPA cDNA and expressed it in carotid arteries of cholesterol-fed rabbits. uPA gene transfer increased artery-wall uPA activity for at least 1 week, with a return to baseline by 2 weeks. One week after gene transfer, uPA-transduced arteries were constricted, with significantly smaller lumens and thicker walls, but no difference in intimal or medial mass. Two weeks after gene transfer, uPA- and control-transduced arteries were morphologically indistinguishable. By 4 weeks, however, uPA-transduced arteries had 70% larger intimas than control-transduced arteries (P < 0.01) and smaller lumens (P < 0.05). Intimal lesions appeared to be of similar composition in uPA- and control-transduced arteries, except that degradation of elastic laminae was evident in uPA-transduced arteries. These data suggest that elevated uPA expression in atherosclerotic arteries contributes to intimal growth and constrictive remodeling leading to lumen loss. Antagonists of uPA activity might, therefore, be useful in limiting intimal growth and preventing constrictive remodeling. Overexpression of uPA in endothelial cells to prevent intravascular thrombosis must be reconsidered, because this intervention could worsen underlying vascular disease.
Circulation | 2004
Shan Wen; Shannon Graf; Philip G. Massey; David A. Dichek
Background—Adenoviral vectors are the most widely used agents for vascular gene transfer. However, the utility of adenoviral vectors for vascular gene transfer is limited by brevity of expression and by the induction of a significant host inflammatory response. Third-generation or “helper-dependent” adenoviral vectors have achieved prolonged recombinant gene expression in liver and muscle with minimal associated inflammation; however, they have never been tested for vascular gene transfer. Methods and Results—We constructed a helper-dependent adenoviral vector expressing rabbit urokinase plasminogen activator (HD-AduPA). HD-AduPA was compared, in a rabbit model of carotid gene transfer, with a first-generation adenovirus, also expressing rabbit uPA (FG-AduPA). uPA expression and vector DNA were measured in arteries harvested from 3 to 56 days after gene transfer. Vector-specific mRNA, vascular inflammation, and neointimal formation were assessed 14 days after gene transfer. uPA expression was lost, and vector DNA declined rapidly in arteries infused with FG-AduPA. In contrast, uPA expression and vector DNA persisted in HD-AduPA arteries for ≥56 days, with stable expression from 14 to 56 days. Increased uPA expression in HD-AduPA arteries was accompanied by high levels of vector-specific uPA mRNA. Moreover, HD-AduPA arteries had significantly less inflammation and neointimal formation than FG-AduPA arteries. Conclusions—Helper-dependent adenoviral vectors can stably express a therapeutic gene in the vascular wall for ≥8 weeks, with minimal associated inflammation. Helper-dependent adenoviral vectors will be useful agents for vascular gene transfer and gene therapy.
Journal of Biological Chemistry | 2006
April Stempien-Otero; A. R. Plawman; J. A. Meznarich; Teja Dyamenahalli; Goro Otsuka; David A. Dichek
Human hearts with end-stage failure and fibrosis have macrophage accumulation and elevated plasminogen activator activity. However, the mechanisms that link macrophage accumulation and plasminogen activator activity with cardiac fibrosis are unclear. We previously reported that mice with macrophage-targeted overexpression of urokinase plasminogen activator (SR-uPA+/o mice) develop cardiac macrophage accumulation by 5 weeks of age and cardiac fibrosis by 15 weeks. We used SR-uPA+/o mice to investigate mechanisms through which macrophage-expressed uPA causes cardiac macrophage accumulation and fibrosis. We hypothesized that: 1) macrophage accumulation and cardiac fibrosis in SR-uPA+/o mice are dependent on localization of uPA by the uPA receptor (uPAR); 2) activation of plasminogen by uPA and subsequent activation of transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase (MMP)-2 and -9 by plasmin are critical pathways through which uPA-expressing macrophages accumulate in the heart and cause fibrosis; and 3) uPA-induced cardiac fibrosis can be attenuated by treatment with verapamil. To test these hypotheses, we bred the SR-uPA+/o transgene into mice deficient in either uPAR or plasminogen and measured cardiac macrophage accumulation and fibrosis. We also measured cardiac TGF-β1 protein (total and active), Smad2 phosphorylation, and MMP activity after the onset of macrophage accumulation but before the onset of cardiac fibrosis. Finally, we treated mice with verapamil. Our studies revealed that plasminogen is necessary for uPA-induced cardiac fibrosis and macrophage accumulation but uPAR is not. We did not detect plasmin-mediated activation of TGF-β1, MMP-2, or MMP-9 in hearts of SR-uPA+/o mice. However, verapamil treatment significantly attenuated both cardiac fibrosis and macrophage accumulation.
Journal of Biological Chemistry | 2011
Stephen D. Farris; Jie Hong Hu; Ranjini M. Krishnan; Isaac Emery; Talyn Chu; Liang Du; Michal Kremen; Helén L. Dichek; Elizabeth S. Gold; Stephen A. Ramsey; David A. Dichek
Data from clinical studies, cell culture, and animal models implicate the urokinase plasminogen activator (uPA)/uPA receptor (uPAR)/plasminogen system in the development of atherosclerosis and aneurysms. However, the mechanisms through which uPA/uPAR/plasminogen stimulate these diseases are not yet defined. We used genetically modified, atherosclerosis-prone mice, including mice with macrophage-specific uPA overexpression and mice genetically deficient in uPAR to elucidate mechanisms of uPA/uPAR/plasminogen-accelerated atherosclerosis and aneurysm formation. We found that macrophage-specific uPA overexpression accelerates atherosclerosis and causes aortic root dilation in fat-fed Ldlr−/− mice (as we previously reported in Apoe−/− mice). Macrophage-expressed uPA accelerates atherosclerosis by stimulation of lesion progression rather than initiation and causes disproportionate lipid accumulation in early lesions. uPA-accelerated atherosclerosis and aortic dilation are largely, if not completely, independent of uPAR. In the absence of uPA overexpression, however, uPAR contributes modestly to both atherosclerosis and aortic dilation. Microarray studies identified S100A8 and S100A9 mRNA as the most highly up-regulated transcripts in uPA-overexpressing macrophages; up-regulation of S100A9 protein in uPA-overexpressing macrophages was confirmed by Western blotting. S100A8/A9, which are atherogenic in mice and are expressed in human atherosclerotic plaques, are also up-regulated in the aortae of mice with uPA-overexpressing macrophages, and macrophage S100A9 mRNA is up-regulated by exposure of wild-type macrophages to medium from uPA-overexpressing macrophages. Macrophage microarray data suggest significant effects of uPA overexpression on cell migration and cell-matrix interactions. Our results confirm in a second animal model that macrophage-expressed uPA stimulates atherosclerosis and aortic dilation. They also reveal uPAR independence of these actions and implicate specific pathways in uPA/Plg-accelerated atherosclerosis and aneurysmal disease.
Circulation | 2010
Jie Hong Hu; Liang Du; Talyn Chu; Goro Otsuka; Nagadhara Dronadula; Mia Jaffe; Sean E. Gill; William C. Parks; David A. Dichek
Background— The mechanisms of atherosclerotic plaque rupture are poorly understood. Urokinase-type plasminogen activator (uPA) is expressed at elevated levels by macrophages in advanced human plaques. Patients with evidence of increased plasminogen activation have an elevated risk of major cardiovascular events. We used atherosclerotic mice to test the hypothesis that increased macrophage uPA expression in advanced plaques would cause histological features similar to those in ruptured human plaques. Methods and Results— Bone marrow from transgenic mice with increased macrophage uPA expression or nontransgenic controls (all apolipoprotein E-null [Apoe−/−]) was transplanted into 35-week-old Apoe−/− recipients, and innominate lesions and aortas were examined 8 to 13 weeks later. Donor macrophages accumulated in innominate lesions adjacent to plaque caps and in aortas, increasing uPA expression at both sites. Recipients of uPA-overexpressing macrophages had an increased prevalence of intraplaque hemorrhage (61% versus 13%; P=0.002) as well as increased lesion fibrin staining and fibrous cap disruption (P=0.06 for both). Transplantation of uPA-overexpressing macrophages increased aortic matrix metalloproteinase activity (40%; P=0.02). This increase was independent of matrix metalloproteinase-9. Conclusions— In advanced plaques of Apoe−/− mice, macrophage uPA overexpression causes intraplaque hemorrhage and fibrous cap disruption, features associated with human plaque rupture. uPA overexpression also increases vascular matrix metalloproteinase activity. These data provide a mechanism that connects macrophage uPA expression, matrix metalloproteinase activity, and plaque rupture features in mice. The data also suggest that elevated plaque plasminogen activator expression and plasminogen activation in humans may be causally linked to plaque rupture and cardiovascular events.
Proceedings of the National Academy of Sciences of the United States of America | 2008
Michal Kremen; Ranjini M. Krishnan; Isaac Emery; Jie Hong Hu; Katherine I. Slezicki; Alyssa Wu; Kun Qian; Liang Du; A. R. Plawman; April Stempien-Otero; David A. Dichek
Urokinase-type plasminogen activator (uPA) is expressed at elevated levels in atherosclerotic human arteries, primarily in macrophages. Plasminogen (Plg), the primary physiologic substrate of uPA, is present at significant levels in blood and interstitial fluid. Both uPA and Plg have activities that could affect atherosclerosis progression. Moreover, correlations between increased Plg activation and accelerated atherosclerosis are reported in several human studies. However, a coherent picture of the role of the uPA/Plg system in atherogenesis has not yet emerged, with at least one animal study suggesting that Plg is atheroprotective. We used a transgenic mouse model of macrophage-targeted uPA overexpression in apolipoprotein E-deficient mice to investigate the roles of uPA and Plg in atherosclerosis. We found that macrophage-expressed uPA accelerated atherosclerotic plaque growth and promoted aortic root dilation through Plg-dependent pathways. These pathways appeared to affect lesion progression rather than initiation and to include actions that disproportionately increase lipid accumulation in the artery wall. In addition, loss of Plg was protective against atherosclerosis both in the presence and absence of uPA overexpression. Transgenic mice with macrophage-targeted uPA overexpression reveal atherogenic roles for both uPA and Plg and are a useful experimental setting for investigating the molecular mechanisms that underlie clinically established relationships between uPA expression, Plg activation, and atherosclerosis progression.