Published online before print August 16, 2004, doi: 10.1161/01.CIR.0000140720.79015.3C
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(Circulation. 2004;110:1330-1336.)
© 2004 American Heart Association, Inc.
Original Articles |
Loss of Collagen XVIII Enhances Neovascularization and Vascular Permeability in Atherosclerosis
From the Vascular Biology Research Program, Department of Surgery (K.S.M., S.S., X.Z.), and Departments of Orthopaedic Surgery and Biostatistics (D.Z.), Children’s Hospital Medical Center; the Cardiovascular Division, Brigham and Women’s Hospital (K.S.M.); and the Department of Cell Biology, Harvard Medical School (B.R.O., N.F.), Boston, Mass.
Correspondence to Karen S. Moulton, Vascular Biology Research Program, Department of Surgery, Children’s Hospital Medical Center, 300 Longwood Ave, Boston, MA 02115. E-mail karen.moulton{at}childrens.harvard.edu
Received March 25, 2004; revision received May 24, 2004; accepted May 25, 2004.
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Abstract |
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Background— Plaque neovascularization is thought to promote atherosclerosis; however, the mechanisms of its regulation are not understood. Collagen XVIII and its proteolytically released endostatin fragment are abundant proteoglycans in vascular basement membranes and the walls of major blood vessels. We hypothesized that collagen XVIII in the aortic wall inhibits the proliferation and intimal extension of vasa vasorum.
Methods and Results— To test our hypothesis, we bred collagen XVIII-knockout (Col18a1–/–) mice into the atherosclerosis-prone apolipoprotein E-deficient (ApoE–/–) strain. After 6 months on a cholesterol diet, aortas from ApoE–/–;Col18a1–/– and ApoE–/–;Col18a1+/– heterozygote mice showed increased atheroma coverage and enhanced lipid accumulation compared with wild-type littermates. We observed more extensive vasa vasorum and intimal neovascularization in knockout but not heterozygote aortas. Endothelial cells sprouting from Col18a1–/– aortas were increased compared with heterozygote and wild-type aortas. In contrast, vascular permeability of large and small blood vessels was enhanced with even heterozygous loss of collagen XVIII but was not suppressed by increasing serum endostatin to wild-type levels.
Conclusions— Our results identify a previously unrecognized function for collagen XVIII that maintains vascular permeability. Loss of this basement membrane proteoglycan enhances angiogenesis and vascular permeability during atherosclerosis by distinct gene-dose-dependent mechanisms.
Key Words: angiogenesis • atherosclerosis • extracellular matrix • permeability • vasa vasorum
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Introduction |
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Neovascularization in the wall of large blood vessels may promote the entry of inflammatory cells and growth of atheromas.1,2 Atherosclerotic but not normal aortas stimulate angiogenesis in the chick chorioallantoic membrane and corneal micropocket assays of angiogenesis.3 Several angiogenic growth factors are highly expressed in atherosclerotic lesions.4,5 However, not all atheromas develop neovascularization, and the distribution of growth factors does not spatially correlate with regions of neovascularization.6 Thus, the complex regulation of plaque angiogenesis must extend beyond an analysis of positive regulators. Factors that antagonize angiogenesis may also be present in atheromas, and loss of endogenous inhibitors may be a potential mechanism for the initiation of plaque angiogenesis.7
Collagen XVIII is an abundant heparan sulfate proteoglycan in vascular and epithelial basement membranes.8 Three different N-terminal ends distinguish short and long isoforms (migration weights range, 220 to 350 kDa) that have different tissue distributions.9 Collagen XVIII molecules contain 10 triple-helical collagen domains that are flanked by 11 non-triple-helical (NC) domains (Figure 1).10 Endostatin (ES), a 20-kDa proteolytic fragment from the C-terminal NC1 domain of collagen XVIII, has been shown to inhibit angiogenesis and atherosclerosis.2,11 The aorta is among the most abundant tissue sources of collagen XVIII and proteolytically released ES.12 We hypothesized that collagen XVIII is degraded during atherosclerosis and that loss of this vessel wall proteoglycan will promote the proliferation of vasa vasorum (VV) into the intima of atheromas.
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To test this hypothesis, we bred collagen XVIII-deficient mice (Col18a1–/–) into the atherosclerosis-susceptible apolipoprotein E-deficient (ApoE–/–) strain. Col18a1–/– mice backcrossed several generations into the C57BL6 strain are viable and fertile but show defective hyaloid vessel regression in the eye, resulting in abnormal retinal vessel development.13 We provide evidence for distinct functions of collagen XVIII in the vascular basement membrane that regulate vascular permeability and angiogenesis during atherosclerosis.
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Methods |
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Materials
Rabbit polyclonal antibodies for collagen XVIII were prepared against the C-terminus ES fragment (amino acids 132 to 315, counted from the first residue of NC1) or the most proximal NC11 domain (amino acids 487 to 785, counted from the methionine start codon of mouse collagen XVIII CR isoform).14 NC11-IgG and ES-IgG cross-react with human collagen XVIII but show no reactivity to tissues from Col18al–/– mice. Recombinant murine ES was expressed in Pichia pastoria and supplied by EntreMed, Inc.
Immunohistochemistry
We stained frozen coronal aortic arch sections with Mac3, 
-smooth muscle actin, and CD31 to quantify cells and neovascularization in atheromas.3 Lipid content was determined after oil red O staining. We analyzed percent area of lipid staining on 5 atheroma sections from >15 mice per genotype. Collagen XVIII in atheromas was detected in paraffin sections stained with NC11-IgG or ES-IgG (1:500 dilution), followed by biotinylated goat anti-rabbit IgG (1:500), avidin-peroxidase (Vector Laboratories), and the red substrate 3-amino-9-ethylcarbazole.
In Vivo Studies on Atherosclerosis
The generation of Col18al–/– mice has been described.13 We bred Col18al–/– mice (C57BL6/J background, n=15) into the ApoE–/– strain (C57BL6/J, n=10, Jackson Laboratory, Bar Harbor, Me). ApoE–/–;Col18a1+/– matings generated littermates with wild-type (WT), heterozygote (Het), and null collagen XVIII deficiencies. Mice were fed a 0.15% cholesterol diet (Harlan-Teklad) from age 8 to 32 weeks to develop advanced lesions. We measured the percent area of Sudan IV+ atheromas in the descending aorta and the mean wall thickness of atheromas along the inner curve of the aortic arch.3 Serum cholesterol levels were measured in an automated colorimetric assay (Children’s Hospital, Boston). We screened blood for genotype-related differences in blood cell counts and liver, renal, and thyroid function tests (Anilytics, Inc). Mouse pathology was evaluated at the Harvard Mouse Histopathology Core. Animal studies were performed in compliance with the Animal Care and Use Committee guidelines.
VV and Intimal Neovascularization
We counted the number of CD31+ VV networks per descending aorta and measured the vascular density of each VV (percent area of CD31+ capillaries per 200x field) detected in flat mounted aortas from each genotype (n=15).3 We compared aortic arches across all genotypes to determine the incidence of intimal neovascularization in the same region of high disease susceptibility, which we reported as the percentage of aortic arches that contained intimal capillaries.
Aorta Explant Sprouting Assay
We adapted the rat aortic ring assay for mouse aortas to test the effects of targeted mutations on endothelial sprouting.3,15 Aorta rings from age-matched WT, Het, and knockout (KO) mice were embedded in rat collagen I (2 mg/mL) and cultured with serum-free media (Invitrogen, No. 17601) and vascular endothelial cell growth factor (VEGF) (0, 2, 4, or 8 ng/mL, n=4 rings per dose).3,15 We measured sprout area in images captured through a Nikon SMZ microscope (50x magnification). Maximum sprout area was normalized to a value=1. Sprouting for each genotype was compared at all VEGF doses by ANOVA based on pooled data from 3 independent experiments.
Permeability of Aortas and Skin Vessels
We measured the permeability of aortas and skin vessels to albumin-bound Evans blue dye (EBD).16 We sedated WT and KO mice (8 to 10 weeks old) in the C57BL6, ApoE–/–, and LDL receptor-deficient (LDLR–/–) strains with avertin and intravenously injected 0.1 mL of 1% EBD per 20 g body weight. After 10 minutes, we made 2 intradermal injections (50 µL) each of PBS+0.05% BSA containing 0 or 10 ng VEGF in dorsal skin. After another 20 minutes, aortas were removed, briefly rinsed clear of blood, and eluted in 100 µL of formamide. Punch biopsies (1 cm) around dorsal skin injection sites were eluted in 0.5 mL formamide. EBD concentration was determined by absorption at 605 nm. We reported EBD content of KO tissues as the fold difference relative to WT.
Permeability to LDL was performed in WT and KO mice in the LDLR–/– background. Human LDL (Biomedical Technologies, Inc) was labeled with 125I.17 We intravenously injected 100 µL buffer containing 5x107 cpm 125I-LDL and 1% EBD. Aorta and blood were collected 30 minutes later.18 The level of I125-LDL in each rinsed aorta was normalized for the peak blood radioactivity. To test whether systemic ES modifies the permeability of KO mice, we delivered 25 or 100 µg/d of murine ES by subcutaneous osmotic pumps (Durect Corp). We measured serum ES levels 4 days after pump implantation and measured LDL permeability on day 5.
Statistical Analysis
Data for lesion content and areas, plaque thickness, body weight, and serum cholesterol fit a normal distribution. Overall probability values for genotype differences were based on the ANOVA. A significant F test indicating overall group differences was followed with post hoc Bonferroni comparisons between groups. Data for VV were compared by Kruskal-Wallis followed by Mann-Whitney U tests for pairwise comparisons.
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Results |
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Collagen XVIII Proteolysis in Atherosclerosis
Atherosclerosis remodels the artery wall through the action of several proteases that could modify collagen XVIII. We detected collagen XVIII in normal and atherosclerotic aortas with either ES-IgG or NC11-IgG, which respectively recognize ES (NC1) or NC11 residues from the most C- and N-terminal domains common to all collagen XVIII isoforms (Figure 1).10 Aorta without atheromas from C57BL6/J and ApoE–/– mice showed similar staining patterns, with either antibody recognizing collagen XVIII proteins in the media and endothelium. In atheromas, the staining patterns for ES and NC11 antibodies diverged. NC11-IgG reactivity was greatly reduced in the artery wall beneath the expanded intima of atheromas, whereas ES-IgG reactivity was preserved except where the media was severely attenuated. These findings suggest that collagen XVIII proteins are differentially reduced during atherosclerosis. The more rapid loss of NC11-containing collagen XVIII proteins is consistent with the presence of a protease-sensitive hinge region upstream of ES and the known susceptibility of this region to proteolytic cleavage by cathepsins, metalloproteases, and elastases, which are abundantly expressed by macrophages and other cells in atheromas.19,20
Collagen XVIII Deficiency Enhances Atherosclerosis
We crossed Col18al–/– mice into the ApoE–/– strain. Congenic analysis confirmed that >99% of chromosomal markers matched C57BL6/J markers. ApoE–/–;Col18a1+/– matings produced littermates with different Col18a1 genotypes, which we designated as aWT, aHet, and aKO to indicate their ApoE–/– genotype and distinguish them from WT, Het, and KO mice in the C57BL6/J strain. After cholesterol feeding for 24 weeks, we observed that the mean percent aortic area with Sudan IV+ lesions was statistically increased from 24.4% in aWT to 37.7% in aHet and 40.7% in aKO (Figure 2). Similarly, the inner wall thickness of aHet and aKO aortic arches was increased (Table). Atheroma areas in aKO were higher than in aHet, but this difference was not statistically significant. Serum cholesterol levels were similar across all genotype groups (Table). These findings show that loss of even one Col18a1 allele increased atherosclerosis.
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Absence of Collagen XVIII Increases Plaque Angiogenesis
We next evaluated the effect of collagen XVIII deficiency on the extent of VV and intimal neovascularization. We identified CD31+-VV networks in the entire descending aorta by in situ staining.3 The median number of VV was 2-fold higher in aKO than in aHet and aWT aortas (Table). In addition, the mean capillary density of VV in aKO aortas was 2-fold increased (Figure 3, A and B).
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Serial sections demonstrate the continuity between erythrocyte-filled intima capillaries and media capillaries (Figure 1C). In advanced atherosclerosis, aortic arches uniformly contain atheromas along the lesser curve and in all major artery branches. We compared the incidence of CD31+ intimal neovascularization in aortic arches with different Col18a1 genotypes. Intimal neovascularization was detected in 53% of aKO arches compared with 20% of aHet and 13% of aWT (Table), which represents a 4-fold higher incidence than previous studies.2 Intimal capillaries were most often seen in extensive atheromas of the right brachiocephalic artery (Figure 3, C and D).
Collagen XVIII Deficiency Increases Atheroma Lipids
Sudan IV stains of aHet and aKO aortas were more intense and readily distinguished from aWT (Figure 2a). We determined the relative area of oil red O lipids in atheromas from each genotype. Lipids were 2.6-fold increased in aKO and aHet atheromas compared with aWT (Figure 4, Table). The area of Mac3+ macrophages was significantly increased in aKO compared with aWT lesions (9.8% versus 6.8%, Table) but reached only borderline statistical significance for aHet atheromas (9.3%, P=0.07). The increased lipid and macrophage contents were accompanied by significantly fewer SMCs in aKO and aHet atheromas (Table). Thus, collagen XVIII deficiency altered the lipid and cellular composition of atheromas.
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Angiogenic Sprouting From Col18al–/– Aorta Is Enhanced
Because the aorta contains abundant collagen XVIII, we predicted that endothelial cell sprouting from WT aortas would be reduced compared with KO explants. WT aorta explants develop few sprouts when cultured in basal serum-free media but show a dose-dependent increase in sprouting that is maximal at VEGF=10 ng/mL.3 We compared the sprouting response of aorta explants from age-matched KO, Het, and WT mice over a range of VEGF doses (0, 2, 4, and 8 ng/mL). Sprout areas from KO aorta explants were significantly higher than Het or WT aortas (Figure 5, P<0.05 for all VEGF doses). In contrast, the sprouting responses of Het and WT aortas were similar. Therefore, sprout formation in vitro and plaque-associated angiogenesis in vivo were enhanced in aortas with complete but not heterozygous loss of collagen XVIII.
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Collagen XVIII Deficiency Increases the Permeability of Large and Small Blood Vessels
The visibly pronounced lipids in aHet and aKO aortas were also seen in skin and neural tissues. Lipid and cholesterol accumulation in the middle ear and adjacent 7th and 8th cranial nerves produced late-onset gait and balance disturbances in >25% of cholesterol-fed aHet and aKO but not aWT mice. To determine whether Col18a1 genotype alters vascular permeability, we measured permeability to albumin-bound EBD in large and small blood vessels for each genotype. EBD contents of aHet and aKO aortas harvested 30 minutes after EBD injection were increased 2.3- and 2.2-fold, respectively, compared with aWT (Figure 6A, P<0.01). We also compared EBD permeability of KO and WT aortas in the absence of hypercholesterolemia.21 Aortas from chow-fed KO mice in C57BL6/J and LDLR–/– strains both showed 1.9-fold increases in EBD contents compared with WT aortas (each strain, P<0.02). Het aortas from C57 and LDLR–/– strains had enhanced EBD permeability similar to the ApoE–/– strain (data not shown).
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We performed the Miles assay in the same mice to compare small blood vessel permeability in the skin. A submaximal VEGF dose (10 ng) was used to detect a potential increase in permeability. Interestingly, EBD skin contents after buffer injections were 2.1-, 2.3-, and 1.9-fold higher in KO compared with WT mice in the C57BL6/J (P<0.01), LDLR–/– (P=0.02), and ApoE–/– (P<0.01) strains, respectively. KO from each strain showed a further VEGF-stimulated increase in EBD, but the levels of enhancement above baseline were proportional for KO and WT (Figure 6B). In separate studies, we observed increased EBD contents of lung, liver, and brain from Het and KO mice (not shown). Thus, baseline vascular permeability to albumin-bound EBD is increased in large and small vessels of mice with loss of one or both Col18al alleles.
Because aHet and aKO aortas accumulated more lipids during atherosclerosis, we measured the permeability of the aorta to LDL.18 EBD permeability in KO mice was similar for all strains, so we used chow-fed LDLR–/– mice to control for confounding variables affecting 125I-LDL deposition, such as competition by high endogenous LDL and LDLR-mediated cell uptake. Mice were coinjected with 5x107 cpm of 125I-human LDL and EBD.18 After 30 minutes, LDL radioactivity deposited in aortas was 3.2-fold higher in KO relative to WT controls (Figure 6C, P<0.01). These same KO aortas had a 2-fold increase in EBD content, as seen previously.
Increased vascular permeability in KO mice could be because of loss of collagen XVIII proteins in the basement membrane and/or loss of ES in the blood. To determine whether circulating ES modifies the permeability of KO aortas, we administered ES protein to KO mice by continuous delivery from a subcutaneous osmotic pump.22 After 4 days, KO mice that received 25 or 100 µg/d of ES achieved serum levels of 60±12 or 353±80 ng/mL, respectively. Despite correction of serum ES to similar or 5-fold higher levels than WT mice, aorta permeability to EBD and LDL was not altered (Figure 6C).
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Discussion |
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These studies provide genetic evidence that loss of collagen XVIII promotes atherosclerosis. Loss of collagen XVIII increases plaque angiogenesis and vascular permeability to lipids by distinct mechanisms that develop at different gene doses. Atherosclerotic involvement in arteries results in differential loss of collagen XVIII proteins. Binding of ES with laminin, nidogen, and perlecan could account for the relative preservation of ES-containing collagen XVIII proteins in blood vessels or could modify its exposure to matrix metalloproteinases, elastase, and cathepsin L.12,19,20 These proteases are active in atheromas, in which they may have redundant activities for processing collagen XVIII.23,24
Complete or heterozygous loss of collagen XVIII increased lipid deposition and vascular permeability, which was not related to genotype differences in serum cholesterol. Increased lipid deposits in the vessel wall enhanced foam cells and atherosclerosis. Increased permeability of small vessels resulted in lipid accumulation in skin and other tissues of mice fed an atherogenic diet. The permeability defect was observed even in the absence of atherosclerosis and hypercholesterolemia, which indicates that it correlated with the Col18a1 genotype. Our results demonstrate a previously unrecognized function for collagen XVIII in basement membranes that is required for the maintenance of vascular permeability.
Increased retention or reduced clearance rates of lipoproteins are other potential mechanisms for accumulating lipids in tissues. Lipid retention in the subendothelium is an early event in atherosclerosis. Areas of EBD accumulation in the aorta contain proteoglycans that also retain lipids.25 Loss of the heparan sulfate proteoglycan collagen XVIII could indirectly alter lipid retention by other proteoglycans, such as biglycan.26 However, labeled LDL levels retained in KO aortas after 72 hours were not higher than levels consistent with a 2-fold rise in permeability (data not shown).18 In a quantitative macrophage recruitment assay, we found that KO and WT mice recruited similar numbers of macrophages, which degraded oxidized LDL at equal rates.17,27 ES exerted no effect on macrophage functions important for foam cell generation or degradation of modified LDL (data not shown). Together, these findings suggest that the mechanism of increased lipid in atheromas is in part because of increased vascular permeability and lipid deposition.
Short-term restoration of serum ES to physiological or 5-fold higher levels did not compensate for the permeability defect associated with loss of the entire gene. It is possible that other domains of collagen XVIII are also necessary for normal permeability function or that longer periods of ES delivery are needed to reverse the defect. Because Het mice were affected, we speculate that the permeability functions of collagen XVIII are sensitive to intermediate reductions of native protein in the vascular basement membrane. Although we show that collagen XVIII deficiency affects the permeability of large and small vessels, ultrastructural studies in KO mice fail to show an anatomic defect.13 There is little functional compensation for loss of collagen XVIII by highly homologous collagen XV or other major matrix components.14,28
Loss of collagen XVIII resulted in more extensive VV and a higher incidence of intimal neovascularization in aKO but not aHet atheromas. These in vivo findings are consistent with the enhanced in vitro sprouting response of KO but not Het and WT aortas and suggest that more severe collagen XVIII deficiency is needed to enhance plaque angiogenesis. The increased angiogenesis in aKO was accompanied by a modest but not statistically significant increase in plaque size compared with aHet. Intimal neovascularization is more frequent in lesions of >250-µm thickness, but neovascular density and intima thickness are poorly correlated.2 During regression of atherosclerosis, neovascularization can increase significantly with only a small decrease in plaque size.29 Plaque neovascularization strongly correlates with the regional content of inflammatory cells.3 Consistent with this, we observed increased lesion macrophages in aKO.
This study reports the effects of deletion of the entire Col18al gene, not just the ES domain, which constitutes only a small 20-kD fragment of this >220-kDa trimeric molecule. Exogenous ES treatments inhibited plaque angiogenesis in ApoE–/– mice, and ES doses similar to serum levels inhibit sprouting from KO, Het, and WT aortas (not shown). However, full-length collagen XVIII or other domains could contribute to the angiogenesis and permeability phenotypes. Putative receptors or cofactors for ES, including glypican, 5ß1 integrin and E-selectin, and the ß-catenin signaling pathway, have been implicated in ES effects on angiogenesis, but their role in the phenotype of KO mice has not yet been determined.30,31,35 We can address the specific contribution of ES by raising variant Col18a1 mutant mice that endogenously express a truncated collagen XVIII lacking ES. Interestingly, some Knobloch syndrome patients have Col18a1 mutations predicted to encode similar truncated proteins.13,32 The young ages of these rare patients impede detection of increased atherosclerosis risk. Our data predict that carriers of Knobloch syndrome Col18a1 mutations could have increased susceptibility for atherosclerosis. Although increased angiogenesis, macrophages, and lipids are characteristics of vulnerable atheromas at risk for rupture, we did not detect myocardial fibrosis from previous infarctions or extravasated erythrocytes directly adjacent to plaque capillaries, which is a more restrictive criterion for plaque hemorrhage.33,34
Our results have important implications for future investigations. First, the inhibition of atherosclerosis by a component of normal blood vessels raises questions as to whether replacement or preservation of collagen XVIII in the vessel wall is a desirable therapeutic outcome. Second, the acquired loss of an artery component that increases lipid deposition and then angiogenesis at late stages suggests a potential model for atherosclerosis progression. Finally, the recognition of collagen XVIII as a molecular determinant of vascular permeability may provide insights to determine how a basement membrane proteoglycan regulates the permeability property of endothelium.
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Acknowledgments |
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These studies were supported by NIH grant HL-67255 to Dr Moulton. Dr Olsen acknowledges support from NIH grant AR-36820 and a grant from the Steinbach Foundation. We thank Wulf Palinski and Joe Witztum for helpful discussions and Rod Bronson for mouse pathology analysis.
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References |
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1. Barger AC, Beeuwkes R III, Lainey LL, et al. Hypothesis: vasa vasorum and neovascularization of human coronary arteries: a possible role in the pathophysiology of atherosclerosis. N Engl J Med. 1984; 310: 175–177.[Medline] [Order article via Infotrieve]
2. Moulton KS, Heller E, Konerding MA, et al. Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice. Circulation. 1999; 99: 1726–1732.
3. Moulton KS, Vakili K, Zurakowski D, et al. Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis. roc Natl Acad Sci U S A. 2003; 100: 4736–4741.
4. Couffinhal T, Kearney M, Witzenbichler B, et al. Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) in normal and atherosclerotic human arteries. Am J Pathol. 1997; 150: 1673–1685.[Abstract]
5. Brogi E, Winkles JA, Underwood R, et al. Distinct patterns of expression of fibroblast growth factors and their receptors in human atheroma and nonatherosclerotic arteries. J Clin Invest. 1993; 92: 2408–2418.[Medline] [Order article via Infotrieve]
6. O’Brien ER, Garvin MR, Dev R, et al. Angiogenesis in human coronary atherosclerotic plaques. Am J Pathol. 1994; 145: 883–894.[Abstract]
7. Hanahan D, Folkman J. Patterns and emerging mechanisms of the angiogenic switch during tumorigenesis. Cell. 1996; 86: 353–364.[CrossRef][Medline] [Order article via Infotrieve]
8. Muragaki Y, Timmons S, Griffith CM, et al. Mouse Col18a1 is expressed in a tissue-specific manner as three alternative variants and is localized in basement membrane zones. Proc Natl Acad Sci U S A. 1995; 92: 8763–8767.
9. Saarela J, Rehn M, Oikarinen A, et al. The short and long forms of type XVIII collagen show clear tissue specificities in their expression and location in basement membrane zones in humans. Am J Pathol. 1998; 153: 611–626.
10. Oh SP, Kamagata Y, Muragaki Y, et al. Isolation and sequencing of cDNAs for proteins with multiple domains of Gly-Xaa-Yaa repeats identify a distinct family of collagenous proteins. Proc Natl Acad Sci U S A. 1994; 91: 4229–4233.
11. O’Reilly MS, Boehm T, Shing Y, et al. Endostatin: an endogenous inhibitor of angiogenesis and tumor growth. Cell. 1997; 88: 277–285.[CrossRef][Medline] [Order article via Infotrieve]
12. Miosge N, Sasaki T, Timpl R. Angiogenesis inhibitor endostatin is a distinct component of elastic fibers in vessel walls. FASEB J. 1999; 13: 1743–1750.
13. Fukai N, Eklund L, Marneros AG, et al. Loss of collagen XVIII/endostatin results in eye abnormalities. EMBO J. 2002; 21: 1535–1544.[CrossRef][Medline] [Order article via Infotrieve]
14. Marneros AG, Keene DR, Hansen U, et al. Collagen XVIII/endostatin is essential for vision and retinal pigment epithelial function. EMBO J. 2004; 23: 89–99.[CrossRef][Medline] [Order article via Infotrieve]
15. Zhu WH, MacIntyre A, Nicosia RF. Regulation of angiogenesis by vascular endothelial growth factor and angiopoietin-1 in the rat aorta model. Am J Pathol. 2002; 161: 823–830.
16. Streit M, Velasco P, Riccardi L, et al. Thrombospondin-1 suppresses wound healing and granulation tissue formation in the skin of transgenic mice. EMBO J. 2000; 19: 3272–3282.[CrossRef][Medline] [Order article via Infotrieve]
17. Goldstein JL, Basu SK, Brown MS. Receptor-mediated endocytosis of low density lipoprotein in cultured cells. Methods Enzymol. 1983; 98: 241–260.[Medline] [Order article via Infotrieve]
18. Skalen K, Gustafsson M, Rydberg EK, et al. Subendothelial retention of atherogenic lipoproteins in early atherosclerosis. Nature. 2002; 417: 750–754.[CrossRef][Medline] [Order article via Infotrieve]
19. Wen W, Moses MA, Wiederschain D, et. al. The generation of endostatin is mediated by elastase. Cancer Res. 1999; 59: 6052–6056.
20. Felbor U, Dreier L, Bryant RA, et al. Secreted cathepsin L generates endostatin from collagen XVIII. EMBO J. 2000; 19: 1187–1194.[CrossRef][Medline] [Order article via Infotrieve]
21. Nakashima Y, Plump AS, Raines EW, et al. ApoE-deficient mice develop lesions of all phases of atherosclerosis throughout the arterial tree. Arterioscler Thromb. 1994; 14: 133–140.
22. Kisker O, Becker CM, Prox D, et al. Continuous administration of endostatin by intraperitoneally implanted osmotic pump improves the efficacy and potency of therapy in a mouse xenograft tumor model. Cancer Res. 2001; 61: 7669–7674.
23. Galis ZS, Sukhova GK, Lark MW, et al. Increased expression of matrix metalloproteinases and matrix degrading activity in vulnerable regions of human atherosclerotic plaques. J Clin Invest. 1994; 94: 2493–2503.[Medline] [Order article via Infotrieve]
24. Chen J, Tung CH, Mahmood U, et al. In vivo imaging of proteolytic activity in atherosclerosis. Circulation. 2002; 105: 2766–2771.
25. Richardson M, Gerrity RG, Alavi MZ, et al. Proteoglycan distribution in areas of differing permeability to Evans blue dye in the aortas of young pigs: an ultrastructural study. Arteriosclerosis. 1982; 2: 369–379.
26. Halfter W, Dong S, Schurer B, et al. Collagen XVIII is a basement membrane heparan sulfate proteoglycan. J Biol Chem. 1998; 273: 25404–25412.
27. Lagasse E, Weissman IL. Flow cytometric identification of murine neutrophils and monocytes. J Immunol Methods. 1996; 197: 139–150.[CrossRef][Medline] [Order article via Infotrieve]
28. Ylikarppa R, Eklund L, Sormunen R, et al. Double knockout mice reveal a lack of major functional compensation between collagens XV and XVIII. Matrix Biol. 2003; 22: 443–448.[CrossRef][Medline] [Order article via Infotrieve]
29. Williams JK, Armstrong ML, Heistad DD. Vasa vasorum in atherosclerotic coronary arteries: responses to vasoactive stimuli and regression of atherosclerosis. Circ Res. 1988; 62: 515–523.
30. Sudhakar A, Sugimoto H, Yang C, et al. Human tumstatin and human endostatin exhibit distinct antiangiogenic activities mediated by alpha v beta 3 and alpha 5 beta 1 integrins. Proc Natl Acad Sci U S A. 2003; 100: 4766–4771.
31. Hanai J, Gloy J, Karumanchi SA, et al. Endostatin is a potential inhibitor of Wnt signaling. J Cell Biol. 2002; 158: 529–539.
32. Suzuki OT, Sertie AL, Der Kaloustian VM, et al. Molecular analysis of collagen XVIII reveals novel mutations, presence of a third isoform, and possible genetic heterogeneity in Knobloch syndrome. Am J Hum Genet. 2002; 71: 1320–1329.[CrossRef][Medline] [Order article via Infotrieve]
33. Braun A, Trigatti BL, Post MJ, et al. Loss of SR-BI expression leads to the early onset of occlusive atherosclerotic coronary artery disease, spontaneous myocardial infarctions, severe cardiac dysfunction, and premature death in apolipoprotein E-deficient mice. Circ Res. 2002; 90: 270–276.
34. Rosenfeld ME, Polinsky P, Virmani R, et al. Advanced atherosclerotic lesions in the innominate artery of the apoE knockout mouse. Arterioscler Thromb Vasc Biol. 2000; 20: 2587–2592.
35. Yu Y, Moulton KS, Khan MK, et al. E-selectin is required for the antiangiogenic activity of endostatin. Proc Natl Acad Sci U S A. 2004; 101: 8005–8010.
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 M. M. Fuster, L. Wang, J. Castagnola, L. Sikora, K. Reddi, P. H.A. Lee, K. A. Radek, M. Schuksz, J. R. Bishop, R. L. Gallo, et al. Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis J. Cell Biol., May 7, 2007; 177(3): 539 - 549. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Zhao, J. A. Hall, N. Levenkova, E. Lee, M. K. Middleton, A. M. Zukas, D. J. Rader, J. J. Rux, and E. Pure CD44 Regulates Vascular Gene Expression in a Proatherogenic Environment Arterioscler Thromb Vasc Biol, April 1, 2007; 27(4): 886 - 892. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-S. Shao, J. Cai, and D. A. Towler Molecular Mechanisms of Vascular Calcification: Lessons Learned From The Aorta Arterioscler Thromb Vasc Biol, July 1, 2006; 26(7): 1423 - 1430. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Iribarren, L. J Herrinton, J. A Darbinian, L. Tamarkin, D. Malinowski, J. H Vogelman, N. Orentreich, and D. Baer Does the association between serum endostatin, an endogenous anti-angiogenic protein, and acute myocardial infarction differ by race? Vascular Medicine, February 1, 2006; 11(1): 13 - 20. [Abstract] [PDF]
|
|
|
|
 |
|
 M. Boodhwani, Y. Nakai, S. Mieno, P. Voisine, C. Bianchi, E. G. Araujo, J. Feng, K. Michael, J. Li, and F. W. Sellke Hypercholesterolemia Impairs the Myocardial Angiogenic Response in a Swine Model of Chronic Ischemia: Role of Endostatin and Oxidative Stress Ann. Thorac. Surg., February 1, 2006; 81(2): 634 - 641. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Zeng, J. Chen, Y. I. Miller, K. Javaherian, and K. S. Moulton Endostatin binds biglycan and LDL and interferes with LDL retention to the subendothelial matrix during atherosclerosis J. Lipid Res., September 1, 2005; 46(9): 1849 - 1859. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Marneros and B. R. Olsen Physiological role of collagen XVIII and endostatin FASEB J, May 1, 2005; 19(7): 716 - 728. [Abstract] [Full Text] [PDF]
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