- Email: [email protected]
The flip side-vascular applications for angiogenesis inhibitors
JOURNAL OF VASCULARSURGERY
1258 Lifeline Research Meeting Abstracts
9. Barleon B, Sozzani S, Zhou D, Weich HA, Mantovani A, Marme D. Migration of human monocytes in response to vascular endothelial growth factor (VEGF) is mediated via the VEGF receptor fit-1. Blood 1996;87:3336-43. 10. Agerberth B, Lee JY, Bergman T, Carlqulst M, Boman HG, Mutt V, et al. Amino acid sequence of PR-39: isolation from pig intestine of a new member of the family of proline-arginine-rich antibacterial peptides. Eur J Biochem 1991;202: 849-54. 11. Gallo RL, Ono M, Povsic T, Page C, Eriksson E, Klagsburn M, et al. Syndecans, cell surface heparan sulfate proteoglycans, are induced by a proline-rich antimicrobial peptide from wounds. Proc Nail Acd Sci U S A 1994;91:11035-369. 12. Shi J, Ross CR, Leto TL, Blecha IF. PR-39, a proline-rich antibacterial peptide that inhibits phagocyte NADPH oxidase activity by binding to Src homology 3 domains of p47 phox. Proc Natl Acad Sci U S A 1996;93:6014-8. 13. Chan YR, Gallo RL. PR-39, a Syndecan-inducing antimicrobial peptide, binds and affects p130(Cas). J Biol Chem 1998;273:28978-85. 14. Li J, Post M, Volk R, Gao Y, Li M, Metais C, et al. Novel peptide regulator of angiogenesis. Nat Med. In press.
T H E FLIP SIDE--VASCULAR APPLICATIONS FOR ANGIOGENESIS INHIBITORS
Karen Moulton, MD Brigham & Women'sHospital Boston, Mass
There are a number of emerging applications for modulators of angiogenesis that impact cardiovascular medicine. Concepts learned from our understanding of angiogenesis, vasculogenesis, and the assembly of larger arteries may provide new insights about cardiovascular disease states that manifest vascular or myocardial remodeling, intimal hyperplasia, vascular malformations and vasculitis. Future therapeutic developments in medicine will include methods to manipulate angiogenesis in both positive and negative ways. The title of an editorial, "Two sides of the coin: stimulators for heart disease and inhibitors for cancer," can be modified to propose there may be two sides of the coin for the treatment ofatherosclerosis: (1) Induction of collateral vessels (arteriogenesis) to treat flow-limiting stenosis in cardiac and peripheral vessels and (2) Inhibition of plaque neovascularization associated with the chronic inflammatory process ofatherosclerosis to delay its progression or stabilize lesions. This presentation will review studies that describe neovascularization in human atherosclerotic lesions, present data that demonstrate the contribution of plaque neovascularization to lesion development, characterize biologic activities that promote plaque angiogenesis, and describe potential strategies for the applications of angiogenesis inhibitors in the treatment of vascular diseases.
June2000
Pathologic description In normal vessels, the microvascular network of vasa vasorum is confined to the adventitital and outer media. In vessels with atherosclerotic involvemcnt, these networks become more abundant and extend into the intima of lesions. Serial images taken during the per fusion of a silicone polymer through a human coronary artery show a narrowed lumen at the site of a plaque and later filling of multiple vessels that arise from vaso vasorum. Putative functions of plaque neovascularization l. The proliferation rates of endothelial cells in plaque vessels vary from 0% to 43%, which indicates these vessels are found in different stages of development. The presence of intimal neovascularization in lesions correlates with an increased proliferation index of all cell types, and suggests that they are markers of growing lesions.1 2. Intimal vessels are found in areas rich in macrophages, T cells, and mast cells-cell types that can activate angiogenesis. Their proximity to inflammatory infiltrates and the expression of adhesion molecules on the endothelium of plaque vessels both suggest that these vessels may recruit inflammatory cells into lesions and initiate a positive feedback mechanism that promotes inflammation in the vessel wall. 2 3. Supply of oxygen and nutrients provided through plaque vessels and vaso vasorum may be necessary precondition for growth beyond a certain stage, after which diffusion from the artery lumen is insufficient to meet the metabolic demands of plaque tissue. 4. Plaque vessels may be a source of intraplaque hemorrhage. Plaque neovascularization is more prevalent in culprit lesions responsible for unstable angina, stroke or myocardial infarction. Factors that stimulate plaque angiogenesis may influence plaque stability. Hypothesis Angiogenesis associated with atherosclerotic lesions is a positive regulator of plaque growth and inflammation. We administered potent angiogenesis inhibitors to apolipoprotein E-deficient mice to determine if such treatments reduce plaque growth. 3 Methods and results Intimal capillaries were first demonstrated by immunohistochemistry staining for the endothelial cell markers CD31 and von Willebrand Factor (vWF) in advanced lesions of apoE-/- mice.
JOURNAL OF VASCULAR SURGERY Volume31, Number 6
Transmission electron microscopy showed increased capillaries and endothelial ceils with signs of early lumen formation in the adventitia adjacent to lesions. The majority of plaques that contained intireal capillaries (13 of 15, 87%) were more than 250 (btm thick. The incidence of intimal vessels in this group was increased nincfold compared with 100 to 250-m thick lesions (P < .0005). Animals were fed 0.15% cholesterol Western type diet to induce significant lesions. The extent of disease at the initiation of treatment was documented in a baseline cohort at age 20 weeks. Remaining littermates were divided into three groups and treated for 16 weeks as follows: group 1, recombinant mouse endostatin 20 m g / k b / d ; group 2, fumagillin analogue TNP-470, 30 m g / k g every other day; and group 3, reference animals received a similar volume of buffer. At the end of treatment, aortic tissues were harvested to measure the extent of atherosclcrotic lesion involvement and to identify intimal capillaries. Average cholesterol levels were similar in all groups. The median plaque area in the aortic sinus before treatment was 0.250 mm 2 (range, 0.1700.348; n = 10). Median plaque areas were 0.321 (0.238-0.412; n = 10), 0.402 (0.248-0.533; n = 15) and 0.751 mm 2 (0.503-0.838; n = 12) for the endostatin, TNP-470, and control groups, respectively (P < .0001). Therefore, endostatin and TNP-470 inhibited plaque growth during the treatment period by 85% and 70%. The percentage of plaques that contained any intimal vessels was significantly smaller in treated mice (5% for endostatin, P = .032; 0% for TNP-470, P = .003) than in controls (29%). The smooth muscle cell contents of lesions from control and treated mice were similar. Intimal vessels were rarely observed in early lesions. Therefore, we compared the effects ofendostatin or TNP-470 treatments in animals with predominantly early versus late-stage lesions. After treatment with endostatin or TNP-470 from age 6 to 22 weeks, lesions in the entire aorta were not very extensive, and no significant differenccs in the percent area of lesion involvement in the aorta or median plaque area at the aortic origin were seen between treatment and control groups. In contrast, similar treatments with either inhibitor at a later interval, from age 32 to 48 weeks, resulted in a significantly reduced plaque size (P = .002). Median plaque areas for the endostatin, TNP-470, and control groups were 0.422 (0.283-0.637; n = 12), 0.448 (0.2600.566; n = 14), and 0.584 mm 2 (0.426-0.911; n = 13), respectively. The inhibition of plaque growth at the later interval appeared smaller than the effect of
Lifeline Research Meeting Abstracts 1259
treatments from age 20 to 36 weeks, partly because of the reduced median size of plaques in the control group. It is also conceivable that the effects of endothelial cell inhibitors on plaques with established intimal capillaries might be different than those on plaques that develop intimal neovascularization during the treatment period.
Conclusions These findings demonstrate (1) Intimal vessels are observed in advanced lesions of apoE-/- mice; (2) Endostatin and TNP-470, two distinct inhibitors of angiogenesis, reduce plaque growth independent of changes in serum cholesterol; (3)The inhibitions of plaque growth by these separate agents correlate with reduced intimal capillaries in lesions; and (4) The treatment effect is observed in lesions at advanced stages when intimal neovascularization is more frequent. Although these studies do not address the specific mechanisms that account for inhibition of plaque growth, they suggest that intimal neovascularization promotes plaque progression and could be potential targets for new treatments to delay disease progression.
Plaque neovascularization--tmanswered questions 1. H o w do inhibitors of angiogenesis delay plaque progression? (Regulation of plaque blood flow versus regulation of inflammatory cell recruitment.) 2. What endogenous factors regulate the formation and regression of plaque vessels? 3. What is the contribution of adventitial neovascularization? 4. Will systemic or local delivery of angiogenesis inhibitors regress lesions or reduce plaque rupture?
Potential vascular applications for angiogenesis hlhibitors 1. Primary or secondary prevention. The above data in apoE-/- mice showed delayed growth of intermediate and advanced staged lesions. Intimal capillaries are detected in Stary types II through V human lesions. Thus, the potential time period for intervention to delay plaque growth could be years. The validation and development of therapeutic strategies will depend on drug availability, delivery, and defined treatment end points. Patient selection will require methods to identify patients at increased risk or modalities that could detect plaque neovascularization. 2. Inhibition o f plaque angiogenesis to stabilize lesions. Intimal neovascularization may directly destabilize lesions by causing intraplaque hemorrhage. The saccular structure or the occasional
1260 Lifeline Research Meeting Abstracts
3.
4.
5. 6.
connection with the artery lumen o f some intimal capillaries may render these vessels mechanically weak and more likely to bleed. Intramural hemorrhage may p r o m o t e further angiogenesis. Angiogenesis in the plaque may indirectly promote plaque rupture through the activation of endothelial cell proteases and matrix metalloproteases.4 Infimal vessels may regulate inflammatory cell recruitment in lesions. The areas o f macrophage infiltration in the fibrous cap over the lipid core of vulnerable lesions correspond to regions at risk for rupture. Restenosis after angioplasty or stent placement. Intimal neovascularization is more prevalent in restenotic lesions3 Increased adventitial anglogenesis is observed in arterial balloon-injury models, but the effects o f angiogenesis inhibitors are not fully known.5 Treatments with endothelial cell inhibitors after injury may impede the repair of the arterial endothelium, which may attenuate the denudation-injury. 6 Treatments with endothelial cell growth factors may augment injury. 7 Regression, I n animal models o f diet-induced atherosclerosis, cholesterol reduction is associated with regression o f plaque neovascularization and a minimal regression o f plaque size. s Transplant-associated atherosclerosis. 9 Vasctflitis. 1°
Sttmmary Therapeutic applications o f angiogenesis inhibitors and stimulators for atherosclerosis may be stageappropriate and not paradoxic. REFERENCES
1. O'Brien ER, Garvin MR, Dev R, Stewart DK, Hinohara, T, Simpson JB, et al. Angiogenesis in human coronary atherosclerotic plaques. Am J Pathol 1994;145:883-94. 2. O'Brien KD, McDonald TO, Chait A, Allen MD, Alpers CE. Neovascular expression of E-selectin, intercellular adhesion molecule-I, and vascular cell adhesion molecule-1 in human atherosclerosis and their relation to initmal leukocyte content. Circulation 1996;93:672-82. 3. Moulton KS, Heller E, Konerding MA, Flynn E, PalinskiW, Folkman J. Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice [see comments]. Circulation 1999;99:1726-32. 4. Aikawa M, Rabkin E, Okada Y, Voglic S, Clinton S, Brinckerhoff C, et al. Lipid lowering by diet reduces matrix metalloproteinase activity and increases collagen content of rabbit atheroma: a potential mechanism of lesion stabilization. Circulation 1998;97:2433-44. 5. Kwon HM, Sangiorgi G, Ritman EL, Lerman A, McKenna C, Virmani R, et al. Adventitial vasa vasorum in ballooninjured coronary arteries: visualization and quantitation by a microscopic three-dimensional computed tomography technique [see comments]. J Am Coil Cardiol 1998;32:2072-9.
JOURNALOF VASCULARSURGERY Jtme2000
6. Asahara T, Banters C, Pastore C, Kearney M, Rossow S, Bunting S, et al. Local deliveryof vascular endothelial growth factor accelerates reendothelialization and attenuates intimal hyperplasia in balloon-injured rat carotid artery [see comments].Circulation 1995;91;2793-801. 7. Lazarous DF, Shou M, Scheinowitz M, Hodge E, Thirumurti V, Kitsiou AN, et al. Comparativeeffects of basic fibroblast growth factor and vascular endothelial growth factor on coronary collateral development and the arterial response to injury. Circulation 1996;94:1074-82, 8. Williams JK, Armstrong ML, Heistad DD. Vasa vasorum in atherosclerotic coronary arteries: responses to vasoacfivestimuli and regressionofatheroslcerosis.Circ Res 1988;62:515-23. 9. Moulton KS, Melder Rf, Dharnidharka VR, Hardin-Young J, Jain RK, Briscoe DM. Angiogenesis in the huPBL-SCID model of human transplant rejection. Transplantation 1999;67:1626-31. 10. KaiserM, Younge B, Bjornsson J, Goronzy JJ, Weyand CM. Formation of new vasa vasorum in vasculitis: production of angiogenesis cytokines by multhmcleated giant cells. Am I Pathol i999;155:765-74. RESULTS TO DATE: CLINICAL STUDIES--THERAPEUTIC A N G I O G E N E S I S I N THE PERIPHERAL A N D CORONARY BEDS
Stephen Epstein, MD Washington Hospital Center Washington, DC As many as 50% o f patients with atherosclerosis lack currently identified risk factors (such as hypertension, smoking, hypercholesterolemia, and diabetes), an observation indicating that additional factors predisposing to atherosclerosis are as yet undetected. Injury to the vessel wall and the associated inflammatory response to injury are now generally recognized as the essential components o f atherogenesis. However, the triggers that initiate and sustain the inflammatory process have not been definitively identified. One candidate trigger o f both inflammatory and autoimmune responses--the subject o f this talk--is infection. I n f e c t i o n as a c o n t r i b u t o r to atherosclerosis Evidence began accumulating over 25 years ago suggesting that herpes viruses may possibly play a role in the development o f atherosclerosis. It was found that Marek's disease virus, an avian herpes virus, caused typical atherosclerotic lesions in chickens, and when smooth muscle ceils (SMCs) were infected with the virus in vitro, cholesterol accumulated. Presence o f p a t h o g e n s in t h e vessel wall a n d seroe p i d e m i o l o g i c studies Evidence in humans suggesting infection predisposes to atherosclerosis derived from studies demonstrating that infectious agents reside in the wall of
1258 Lifeline Research Meeting Abstracts
9. Barleon B, Sozzani S, Zhou D, Weich HA, Mantovani A, Marme D. Migration of human monocytes in response to vascular endothelial growth factor (VEGF) is mediated via the VEGF receptor fit-1. Blood 1996;87:3336-43. 10. Agerberth B, Lee JY, Bergman T, Carlqulst M, Boman HG, Mutt V, et al. Amino acid sequence of PR-39: isolation from pig intestine of a new member of the family of proline-arginine-rich antibacterial peptides. Eur J Biochem 1991;202: 849-54. 11. Gallo RL, Ono M, Povsic T, Page C, Eriksson E, Klagsburn M, et al. Syndecans, cell surface heparan sulfate proteoglycans, are induced by a proline-rich antimicrobial peptide from wounds. Proc Nail Acd Sci U S A 1994;91:11035-369. 12. Shi J, Ross CR, Leto TL, Blecha IF. PR-39, a proline-rich antibacterial peptide that inhibits phagocyte NADPH oxidase activity by binding to Src homology 3 domains of p47 phox. Proc Natl Acad Sci U S A 1996;93:6014-8. 13. Chan YR, Gallo RL. PR-39, a Syndecan-inducing antimicrobial peptide, binds and affects p130(Cas). J Biol Chem 1998;273:28978-85. 14. Li J, Post M, Volk R, Gao Y, Li M, Metais C, et al. Novel peptide regulator of angiogenesis. Nat Med. In press.
T H E FLIP SIDE--VASCULAR APPLICATIONS FOR ANGIOGENESIS INHIBITORS
Karen Moulton, MD Brigham & Women'sHospital Boston, Mass
There are a number of emerging applications for modulators of angiogenesis that impact cardiovascular medicine. Concepts learned from our understanding of angiogenesis, vasculogenesis, and the assembly of larger arteries may provide new insights about cardiovascular disease states that manifest vascular or myocardial remodeling, intimal hyperplasia, vascular malformations and vasculitis. Future therapeutic developments in medicine will include methods to manipulate angiogenesis in both positive and negative ways. The title of an editorial, "Two sides of the coin: stimulators for heart disease and inhibitors for cancer," can be modified to propose there may be two sides of the coin for the treatment ofatherosclerosis: (1) Induction of collateral vessels (arteriogenesis) to treat flow-limiting stenosis in cardiac and peripheral vessels and (2) Inhibition of plaque neovascularization associated with the chronic inflammatory process ofatherosclerosis to delay its progression or stabilize lesions. This presentation will review studies that describe neovascularization in human atherosclerotic lesions, present data that demonstrate the contribution of plaque neovascularization to lesion development, characterize biologic activities that promote plaque angiogenesis, and describe potential strategies for the applications of angiogenesis inhibitors in the treatment of vascular diseases.
June2000
Pathologic description In normal vessels, the microvascular network of vasa vasorum is confined to the adventitital and outer media. In vessels with atherosclerotic involvemcnt, these networks become more abundant and extend into the intima of lesions. Serial images taken during the per fusion of a silicone polymer through a human coronary artery show a narrowed lumen at the site of a plaque and later filling of multiple vessels that arise from vaso vasorum. Putative functions of plaque neovascularization l. The proliferation rates of endothelial cells in plaque vessels vary from 0% to 43%, which indicates these vessels are found in different stages of development. The presence of intimal neovascularization in lesions correlates with an increased proliferation index of all cell types, and suggests that they are markers of growing lesions.1 2. Intimal vessels are found in areas rich in macrophages, T cells, and mast cells-cell types that can activate angiogenesis. Their proximity to inflammatory infiltrates and the expression of adhesion molecules on the endothelium of plaque vessels both suggest that these vessels may recruit inflammatory cells into lesions and initiate a positive feedback mechanism that promotes inflammation in the vessel wall. 2 3. Supply of oxygen and nutrients provided through plaque vessels and vaso vasorum may be necessary precondition for growth beyond a certain stage, after which diffusion from the artery lumen is insufficient to meet the metabolic demands of plaque tissue. 4. Plaque vessels may be a source of intraplaque hemorrhage. Plaque neovascularization is more prevalent in culprit lesions responsible for unstable angina, stroke or myocardial infarction. Factors that stimulate plaque angiogenesis may influence plaque stability. Hypothesis Angiogenesis associated with atherosclerotic lesions is a positive regulator of plaque growth and inflammation. We administered potent angiogenesis inhibitors to apolipoprotein E-deficient mice to determine if such treatments reduce plaque growth. 3 Methods and results Intimal capillaries were first demonstrated by immunohistochemistry staining for the endothelial cell markers CD31 and von Willebrand Factor (vWF) in advanced lesions of apoE-/- mice.
JOURNAL OF VASCULAR SURGERY Volume31, Number 6
Transmission electron microscopy showed increased capillaries and endothelial ceils with signs of early lumen formation in the adventitia adjacent to lesions. The majority of plaques that contained intireal capillaries (13 of 15, 87%) were more than 250 (btm thick. The incidence of intimal vessels in this group was increased nincfold compared with 100 to 250-m thick lesions (P < .0005). Animals were fed 0.15% cholesterol Western type diet to induce significant lesions. The extent of disease at the initiation of treatment was documented in a baseline cohort at age 20 weeks. Remaining littermates were divided into three groups and treated for 16 weeks as follows: group 1, recombinant mouse endostatin 20 m g / k b / d ; group 2, fumagillin analogue TNP-470, 30 m g / k g every other day; and group 3, reference animals received a similar volume of buffer. At the end of treatment, aortic tissues were harvested to measure the extent of atherosclcrotic lesion involvement and to identify intimal capillaries. Average cholesterol levels were similar in all groups. The median plaque area in the aortic sinus before treatment was 0.250 mm 2 (range, 0.1700.348; n = 10). Median plaque areas were 0.321 (0.238-0.412; n = 10), 0.402 (0.248-0.533; n = 15) and 0.751 mm 2 (0.503-0.838; n = 12) for the endostatin, TNP-470, and control groups, respectively (P < .0001). Therefore, endostatin and TNP-470 inhibited plaque growth during the treatment period by 85% and 70%. The percentage of plaques that contained any intimal vessels was significantly smaller in treated mice (5% for endostatin, P = .032; 0% for TNP-470, P = .003) than in controls (29%). The smooth muscle cell contents of lesions from control and treated mice were similar. Intimal vessels were rarely observed in early lesions. Therefore, we compared the effects ofendostatin or TNP-470 treatments in animals with predominantly early versus late-stage lesions. After treatment with endostatin or TNP-470 from age 6 to 22 weeks, lesions in the entire aorta were not very extensive, and no significant differenccs in the percent area of lesion involvement in the aorta or median plaque area at the aortic origin were seen between treatment and control groups. In contrast, similar treatments with either inhibitor at a later interval, from age 32 to 48 weeks, resulted in a significantly reduced plaque size (P = .002). Median plaque areas for the endostatin, TNP-470, and control groups were 0.422 (0.283-0.637; n = 12), 0.448 (0.2600.566; n = 14), and 0.584 mm 2 (0.426-0.911; n = 13), respectively. The inhibition of plaque growth at the later interval appeared smaller than the effect of
Lifeline Research Meeting Abstracts 1259
treatments from age 20 to 36 weeks, partly because of the reduced median size of plaques in the control group. It is also conceivable that the effects of endothelial cell inhibitors on plaques with established intimal capillaries might be different than those on plaques that develop intimal neovascularization during the treatment period.
Conclusions These findings demonstrate (1) Intimal vessels are observed in advanced lesions of apoE-/- mice; (2) Endostatin and TNP-470, two distinct inhibitors of angiogenesis, reduce plaque growth independent of changes in serum cholesterol; (3)The inhibitions of plaque growth by these separate agents correlate with reduced intimal capillaries in lesions; and (4) The treatment effect is observed in lesions at advanced stages when intimal neovascularization is more frequent. Although these studies do not address the specific mechanisms that account for inhibition of plaque growth, they suggest that intimal neovascularization promotes plaque progression and could be potential targets for new treatments to delay disease progression.
Plaque neovascularization--tmanswered questions 1. H o w do inhibitors of angiogenesis delay plaque progression? (Regulation of plaque blood flow versus regulation of inflammatory cell recruitment.) 2. What endogenous factors regulate the formation and regression of plaque vessels? 3. What is the contribution of adventitial neovascularization? 4. Will systemic or local delivery of angiogenesis inhibitors regress lesions or reduce plaque rupture?
Potential vascular applications for angiogenesis hlhibitors 1. Primary or secondary prevention. The above data in apoE-/- mice showed delayed growth of intermediate and advanced staged lesions. Intimal capillaries are detected in Stary types II through V human lesions. Thus, the potential time period for intervention to delay plaque growth could be years. The validation and development of therapeutic strategies will depend on drug availability, delivery, and defined treatment end points. Patient selection will require methods to identify patients at increased risk or modalities that could detect plaque neovascularization. 2. Inhibition o f plaque angiogenesis to stabilize lesions. Intimal neovascularization may directly destabilize lesions by causing intraplaque hemorrhage. The saccular structure or the occasional
1260 Lifeline Research Meeting Abstracts
3.
4.
5. 6.
connection with the artery lumen o f some intimal capillaries may render these vessels mechanically weak and more likely to bleed. Intramural hemorrhage may p r o m o t e further angiogenesis. Angiogenesis in the plaque may indirectly promote plaque rupture through the activation of endothelial cell proteases and matrix metalloproteases.4 Infimal vessels may regulate inflammatory cell recruitment in lesions. The areas o f macrophage infiltration in the fibrous cap over the lipid core of vulnerable lesions correspond to regions at risk for rupture. Restenosis after angioplasty or stent placement. Intimal neovascularization is more prevalent in restenotic lesions3 Increased adventitial anglogenesis is observed in arterial balloon-injury models, but the effects o f angiogenesis inhibitors are not fully known.5 Treatments with endothelial cell inhibitors after injury may impede the repair of the arterial endothelium, which may attenuate the denudation-injury. 6 Treatments with endothelial cell growth factors may augment injury. 7 Regression, I n animal models o f diet-induced atherosclerosis, cholesterol reduction is associated with regression o f plaque neovascularization and a minimal regression o f plaque size. s Transplant-associated atherosclerosis. 9 Vasctflitis. 1°
Sttmmary Therapeutic applications o f angiogenesis inhibitors and stimulators for atherosclerosis may be stageappropriate and not paradoxic. REFERENCES
1. O'Brien ER, Garvin MR, Dev R, Stewart DK, Hinohara, T, Simpson JB, et al. Angiogenesis in human coronary atherosclerotic plaques. Am J Pathol 1994;145:883-94. 2. O'Brien KD, McDonald TO, Chait A, Allen MD, Alpers CE. Neovascular expression of E-selectin, intercellular adhesion molecule-I, and vascular cell adhesion molecule-1 in human atherosclerosis and their relation to initmal leukocyte content. Circulation 1996;93:672-82. 3. Moulton KS, Heller E, Konerding MA, Flynn E, PalinskiW, Folkman J. Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice [see comments]. Circulation 1999;99:1726-32. 4. Aikawa M, Rabkin E, Okada Y, Voglic S, Clinton S, Brinckerhoff C, et al. Lipid lowering by diet reduces matrix metalloproteinase activity and increases collagen content of rabbit atheroma: a potential mechanism of lesion stabilization. Circulation 1998;97:2433-44. 5. Kwon HM, Sangiorgi G, Ritman EL, Lerman A, McKenna C, Virmani R, et al. Adventitial vasa vasorum in ballooninjured coronary arteries: visualization and quantitation by a microscopic three-dimensional computed tomography technique [see comments]. J Am Coil Cardiol 1998;32:2072-9.
JOURNALOF VASCULARSURGERY Jtme2000
6. Asahara T, Banters C, Pastore C, Kearney M, Rossow S, Bunting S, et al. Local deliveryof vascular endothelial growth factor accelerates reendothelialization and attenuates intimal hyperplasia in balloon-injured rat carotid artery [see comments].Circulation 1995;91;2793-801. 7. Lazarous DF, Shou M, Scheinowitz M, Hodge E, Thirumurti V, Kitsiou AN, et al. Comparativeeffects of basic fibroblast growth factor and vascular endothelial growth factor on coronary collateral development and the arterial response to injury. Circulation 1996;94:1074-82, 8. Williams JK, Armstrong ML, Heistad DD. Vasa vasorum in atherosclerotic coronary arteries: responses to vasoacfivestimuli and regressionofatheroslcerosis.Circ Res 1988;62:515-23. 9. Moulton KS, Melder Rf, Dharnidharka VR, Hardin-Young J, Jain RK, Briscoe DM. Angiogenesis in the huPBL-SCID model of human transplant rejection. Transplantation 1999;67:1626-31. 10. KaiserM, Younge B, Bjornsson J, Goronzy JJ, Weyand CM. Formation of new vasa vasorum in vasculitis: production of angiogenesis cytokines by multhmcleated giant cells. Am I Pathol i999;155:765-74. RESULTS TO DATE: CLINICAL STUDIES--THERAPEUTIC A N G I O G E N E S I S I N THE PERIPHERAL A N D CORONARY BEDS
Stephen Epstein, MD Washington Hospital Center Washington, DC As many as 50% o f patients with atherosclerosis lack currently identified risk factors (such as hypertension, smoking, hypercholesterolemia, and diabetes), an observation indicating that additional factors predisposing to atherosclerosis are as yet undetected. Injury to the vessel wall and the associated inflammatory response to injury are now generally recognized as the essential components o f atherogenesis. However, the triggers that initiate and sustain the inflammatory process have not been definitively identified. One candidate trigger o f both inflammatory and autoimmune responses--the subject o f this talk--is infection. I n f e c t i o n as a c o n t r i b u t o r to atherosclerosis Evidence began accumulating over 25 years ago suggesting that herpes viruses may possibly play a role in the development o f atherosclerosis. It was found that Marek's disease virus, an avian herpes virus, caused typical atherosclerotic lesions in chickens, and when smooth muscle ceils (SMCs) were infected with the virus in vitro, cholesterol accumulated. Presence o f p a t h o g e n s in t h e vessel wall a n d seroe p i d e m i o l o g i c studies Evidence in humans suggesting infection predisposes to atherosclerosis derived from studies demonstrating that infectious agents reside in the wall of