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Circulation. 1996;94:3090-3097

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(Circulation. 1996;94:3090-3097.)
© 1996 American Heart Association, Inc.


Articles

Macrophages, Smooth Muscle Cells, and Tissue Factor in Unstable Angina

Implications for Cell-Mediated Thrombogenicity in Acute Coronary Syndromes

Pedro R. Moreno, MD; Victor H. Bernardi, MD; Julio Lopez-Cuellar, MD; Alvaro M. Murcia, MD; Igor F. Palacios, MD; Herman K. Gold, MD; Roxana Mehran, MD; Samin K. Sharma, MD; Yale Nemerson, MD; Valentin Fuster, MD, PhD; John T. Fallon, MD, PhD

the Cardiac Unit, Massachusetts General Hospital, Harvard Medical School, Boston, and the Cardiovascular Institute (R.M., S.K.S., Y.N., V.F., J.T.F.), Mount Sinai School of Medicine, New York, NY.

Correspondence to Pedro R. Moreno, MD, Department of Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115. E-mail prmoreno@bics.bwh.harvard.edu.


*    Abstract
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*Abstract
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Background Macrophage expression of tissue factor may be responsible for coronary thrombogenicity in patients with plaque rupture. In patients without plaque rupture, smooth muscle cells may be the thrombogenic substrate. This study was designed to identify the cellular correlations of tissue factor in patients with unstable angina.

Methods and Results Tissue from 50 coronary specimens (1560 pieces) from patients with unstable angina and 15 specimens from patients with stable angina were analyzed. Total and segmental areas (in square millimeters) were identified with trichrome staining. Macrophages, smooth muscle cells, and tissue factor were identified by immunostaining. Tissue factor content was larger in unstable angina (42±3%) than in stable angina (18±4%) (P=.0001). Macrophage content was also larger in unstable angina (16±2%) than in stable angina (5±2%) (P=.002). The percentage of tissue factor located in cellular areas was larger in coronary samples from patients with unstable angina (67±8%) than in samples from patients with stable angina (40±5%) (P=.00007). Multiple linear stepwise regression analysis showed that coronary tissue factor content correlated significantly (r=.83, P<.0001) with macrophage and smooth muscle cell areas only in tissue from patients with unstable angina, with a strong relationship between tissue factor content and macrophages in the atheromatous gruel (r=.98, P<.0001).

Conclusions Tissue factor content is increased in unstable angina and correlates with areas of macrophages and smooth muscle cells, suggesting a cell-mediated thrombogenicity in patients with acute coronary syndromes.


Key Words: atherosclerosis • coronary disease • thrombosis • leukocytes


*    Introduction
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up arrowAbstract
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Rupture of lipid-rich coronary plaques with subsequent thrombosis is probably the most important mechanism underlying the sudden onset of acute coronary syndromes.1 2 3 Macrophages may play a role in rupture of the fibrous cap, with subsequent exposure of the lipid-rich atheromatous gruel to circulating blood, resulting in coronary thrombosis.4 5 6 Tissue factor antigen is present in the atheromatous gruel,7 is upregulated in circulating and endothelium-adhered monocytes, and is also increased in coronary tissue from patients with unstable angina.8 9 10 Therefore, tissue factor is a candidate for the procoagulant activity of ruptured coronary plaques. Tissue factor requires insertion into membranes containing acidic phospholipids to function efficiently as a cofactor.11 Although atheromatous gruel contains many lipids and antigenically detected tissue factor, intact cells are detected only at the boundary of the necrotic core, so the mechanisms of increased thrombogenicity remain to be elucidated.

Smooth muscle cells (SMCs) have been implicated in the pathophysiology of acute ischemic syndromes,12 13 with an increased presence in thrombosed vessels from patients with unstable angina at rest.14 Furthermore, fatal coronary thrombosis may occur with only fissures or erosions of the fibrous cap without exposure of the atheromatous gruel.15 16 However, thrombogenicity of coronary SMCs is unclear and remains to be elucidated.

This study was designed to identify tissue factor location within the plaque and to determine cellular correlations with macrophages and SMCs by a systematic quantification approach in coronary plaque tissue from patients with stable and unstable angina.


*    Methods
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*Methods
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Patient Population
From October 1991 to November 1994, 724 consecutive directional coronary atherectomy procedures were performed in the Cardiac Catheterization Laboratory of the Massachusetts General Hospital. Patients were required to meet the Braunwald definition of unstable angina.17 This study was performed simultaneously with a study that evaluated the role of macrophages in restenosis after coronary intervention in patients with unstable angina,18 so all patients required a follow-up angiography within 1 to 12 months after directional coronary atherectomy. Initially, we identified 106 patients who met both clinical and angiographic criteria. Fifty-six patients were excluded because of a previous procedure at the site of the culprit lesion (44 patients), follow-up angiography >12 months (4 patients), and atherectomy sample area <1.5 mm2 (8 patients). Fifty lesions from patients with unstable angina (38 men and 12 women; mean age, 62±12 years; range, 41 to 80 years) compose the study population. Fifteen lesions from patients with chronic stable angina (12 men and 3 women; mean age, 63±7 years; range, 49 to 71 years) constitute the control group. Patients were required to meet the Canadian Cardiovascular Society classification for stable angina.19

Atherectomy Specimens
Multiple pieces of tissue were obtained from each lesion and were immediately immersed in 10% formalin. Tissue was then routinely processed for paraffin embedding according to conventional techniques. Sections were serially cut at 5 µm, mounted on lysine-coated slides, and stained with hematoxylin-eosin and by the modified elastic tissue–Masson's trichrome method.

Human Tissue Factor Antibody
Polyclonal anti–human tissue factor (TF) antibody was raised in rabbits to the extracellular domain of rTF (sTF), residues 1 to 218. An IgG fraction was prepared from the crude antiserum by adsorption to and elution from a protein-A Sepharose column (Pharmacia). Immunopurification was achieved by binding of sTF to an Affigel-10 column (BioRad) and then adsorption of the IgG fraction to the column. After exhaustive washing with buffer, specific anti-sTF antibody was eluted with 4 mol/L guanidinium hydrochloride. The antibody was dialyzed into Tris buffer before use. Specificity of the sTF antibody was shown by absorption with a 10-fold excess of TF antigen and staining.

Immunocytochemistry
Human macrophage antibody staining was done with 5-µm-thick sections deparaffinized and rehydrated with distilled water. Slides were placed in PBS, blocked with normal goat serum and 3% H2O2 in water, washed in PBS, and incubated with appropriate primary antibody from 0.5 to 2 hours at 37°C. Sections were stained with an anti–human panmacrophage antibody, 7.6 µg/mL anti–CD-68; KP-1 (M814 Dako); 0.1 µg/mL anti–smooth muscle {alpha}-actin antibody (Dako); and 0.5 µg/mL of the sTF antibody. Sections were washed in PBS, and primary antibodies were detected with a biotin-streptavidin amplified detection system (SuperSensitive Kit, Biogenex) for 20 minutes at room temperature. Slides were again washed in PBS and reacted with horseradish peroxidase–conjugated streptavidin for 20 minutes at room temperature and developed with diaminobenzidine. Sections were then rehydrated, coverslipped with Permount (Fisher Scientific), and examined. Positive control slides (placenta for sTF, spleen for KP-1, and intact arteries for {alpha}-actin), nonimmune negative controls, and processing controls were performed for each antigen stain.

Morphometry
Total specimen area and segmental area for each of the plaque components were quantified by planimetry for each specimen. Each sample was outlined manually from each stained section, and the area occupied by stained macrophages, SMCs, and tissue factor within each histologically defined component was measured. Total area in square millimeters and the percentage of the total area are reported. Specimens with total area <1.5 mm2 were excluded. The trichrome connective tissue stain was used to identify and quantify the following five components: (1) sclerotic tissue, composed of tissue with sparse cells and densely stained collagen (Fig 1A and 1BDownDown); (2) fibrocellular tissue, composed of tissue with abundant SMCs and densely stained collagen (Fig 1CDown); (3) hypercellular tissue, composed of a loose connective tissue matrix containing numerous stellate cells (Fig 1DDown); (4) atheromatous gruel, composed of necrotic cellular debris and cholesterol clefts without evidence of connective tissue matrix (Fig 1EDown); and (5) thrombus, which stained red (Fig 1FDown). Media was recognized by the presence of internal elastic lamina and more orderly SMCs and connective tissue matrix. To establish tissue factor location, colocalization planimetric analysis was performed with areas of macrophages and SMCs (intracellular) as well as with acellular areas (extracellular). Hypercellular and fibrocellular tissues were clearly defined as cellular areas. Cellularity of lipid-rich gruel and thrombus was evaluated by colocalization planimetric analysis as well as linear regression analysis between these areas and immunostained cells. Finally, sclerotic tissue with cells was defined as cellular, and sclerotic tissue deprived of cell nuclei was defined as acellular.








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Figure 1. Trichrome connective tissue stain used to identify and quantify the following five components: sclerotic tissue, composed of tissue with few cells and densely stained collagen (A and B); fibrocellular tissue, composed of tissue with abundant smooth muscle cells and densely stained collagen (C); hypercellular tissue, composed of a loose connective tissue matrix containing numerous stellate cells (D); atheromatous gruel, composed of acellular debris with cholesterol clefts and without preserved connective tissue matrix (E); and thrombus, which stained red (F).

Statistical Analysis
Results are expressed as mean±SEM of the individual specimen measurements. Values of P<.05 were considered statistically significant. For comparison of discrete variables (clinical and demographic data), Fisher's test was used. For comparison of two gaussian samples, a two-tailed Student's t test was used. For comparison of data not compatible with a normal frequency distribution (morphometric data), the two-tailed Student's t test was performed with logarithmic transformation of individual values. For multiple comparisons, a correction for the level of significance was performed according to the Bonferroni formula. Multiple stepwise linear regression analysis was performed with the five segmental areas described in the morphometry section and the areas of macrophages (KP-1) and SMCs ({alpha}-actin) included as independent variables. Tissue factor area was included as the outcome variable. Independent variables with significant association in the multiple analysis were examined by linear regression analysis for prediction, correlation, and summarization. Sample size, equation of the fitted line, fraction of variation, SD of regression, and residual variances are also reported.


*    Results
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*Results
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The demographic characteristics are shown in Table 1Down. There were no differences in age, sex, coronary risk factors, or distribution of the vessel containing the culprit lesion between tissue from patients with unstable and stable angina.


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Table 1. Clinical, Demographic, and Angiographic Characteristics of Patients With Stable and Unstable Angina

Morphometry
A total of 1560 pieces of tissue, 24±2 from each specimen (sum of four stainings), were quantified. Total, segmental, and percent area measurements are given in Table 2Down. The percentage of total area occupied by sclerotic tissue was lower in coronary samples from patients with unstable angina (34±4%) than in samples from patients with stable angina (64±5%) (P=.0001). The percentage of total area occupied by hypercellular tissue was larger in coronary samples from patients with unstable angina (23±3%) than in samples from patients with stable angina (3±3%) (P=.0001). There was a tendency toward a larger percentage of atheromatous gruel in samples from patients with unstable angina (7±3%) than in samples from patients with stable angina (4±2%) (P=.06). Thrombus was present in 24 of 50 samples from patients with unstable angina and in 2 of 15 samples from patients with stable angina (P=.018). The percentage of total area occupied by tissue factor was larger in coronary samples from patients with unstable angina (42±3%) than in samples from patients with stable angina (18±4%) (P=.0001). The percentage of total area occupied by macrophages was larger in coronary samples from patients with unstable angina (16±2%) than in samples from patients with stable angina (5±2%) (P=.002). Finally, the percentage of total area occupied by {alpha}-actin–positive SMCs was not significantly different in coronary tissue from patients with unstable angina than in specimens from patients with stable angina (P=NS).


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Table 2. Total, Segmental, and Percent Areas for Cellular and Acellular Tissue Components of Directional Coronary Atherectomy Specimens From Patients With Stable and Unstable Angina

Tissue Factor Location (Intracellular Versus Extracellular)
Colocalization planimetric analyses of tissue factor content with cellular and acellular areas in both groups are shown in Table 3Down. The percentage of tissue factor located in cellular areas was larger in coronary samples from patients with unstable angina (67±8%) than in samples from patients with stable angina (40±5%) (P=.00007). The percentage of tissue factor located in acellular areas was lower in coronary samples from patients with unstable angina (33±4%) than in samples from patients with stable angina (60±3%) (P=.0001). In cellular areas, tissue factor was present in macrophages, followed by SMCs and KP-1–negative/{alpha}-actin–negative cells. This latter group of cells was located in hypercellular and fibrocellular tissue only. Morphology suggested that these cells were mostly SMCs, but T cells and mast cells could not be excluded. In acellular areas, tissue factor antigen was present in sclerotic tissue as well as in the atheromatous gruel.


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Table 3. Segmental and Percent Area Distribution for Tissue Factor Location in Directional Coronary Atherectomy Specimens From Patients With Stable and Unstable Angina

Correlation of Tissue Factor With Cellular and Acellular Areas
In tissue from patients with stable angina, multiple linear regression analysis showed no correlation between tissue factor and macrophages (r=.014, P=.67) (Fig 2ADown) or between tissue factor and SMCs (r=.001, P=.8) (Fig 3ADown).




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Figure 2. A, Association of macrophage area (mm2) identified by KP-1 immunostaining and tissue factor area (mm2) identified by a polyclonal antibody in coronary atherectomy specimens from 15 patients with stable angina, which can be described by the equation y=0.217337x+0.964934 (r=.014, P=.67, SD of regression=0.680439, variance of residual=0.462997). B, Association of macrophage area (mm2) identified by KP-1 immunostaining and tissue factor area (mm2) identified by a polyclonal antibody in coronary atherectomy specimens from 50 patients with unstable angina, which can be described by the equation y=0.932441x+0.481235 (r=.67, P<.0001, SD of regression=0.437324, variance of residual=0.187350).




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Figure 3. A, Association of smooth muscle cell area (mm2) identified by {alpha}-actin immunostaining and tissue factor area (mm2) identified by a polyclonal antibody in coronary atherectomy specimens from 15 patients with stable angina, which can be described by the equation y=-0.028791x+1.085768 (r=.001, P<.8, SD of regression=0.683734, variance of residual=0.116307). B, Association of smooth muscle cell area (mm2) identified by {alpha}-actin immunostaining and tissue factor area (mm2) identified by a polyclonal antibody in coronary atherectomy specimens from 50 patients with unstable angina, which can be described by the equation y=0.775013x+0.382579 (r=.68, P<.0001, SD of regression=0.431234, variance of residual=0.182168).

In tissue from patients with unstable angina, univariate analysis correlated tissue factor with hypercellular tissue (P=.001), atheromatous gruel (P=.004), fibrocellular tissue (P=.003), SMCs (P<.0001), and macrophages (P<.0001). Multiple linear stepwise regression analysis identified macrophages (r=.67, P<.0001) (Figs 2B and 4UpDown) and SMCs (r=.68, P<.0001) (Figs 3B and 4UpDown) as independent predictors for tissue factor content on the basis of the following equation: y=0.588565xSMC area+0.696687xmacrophages+0.142781 (r=.83, P<.0001).








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Figure 4. Sequential segments of an atherectomy tissue fragment containing fibrocellular plaque and media separated by internal elastic lamina, seen in Fig 3AUp as an irregular black line. A, Trichrome connective tissue stain; B, anti–smooth muscle cell {alpha}-actin antibody; C, polyclonal anti–human tissue factor antibody (sTF); D, atheromatous gruel identified with the trichrome connective tissue stain; E, macrophages identified with anti–human panmacrophage monoclonal antibody (immunoperoxidase); and F, polyclonal anti–human tissue factor antibody (sTF) in the atheromatous gruel.

Correlations of Tissue Factor Within Lipid-Rich Areas (Unstable Angina)
Lipid-rich atheromatous gruel was identified in 13 of 50 samples (26%). SMCs were identified in the lipid core of only one specimen. Macrophages were identified in all lipid-rich areas (100%). KP-1 identified intact macrophages (predominantly at the periphery) as well as antigen in acellular regions, most notably in the core. Tissue factor was identified in all lipid-rich areas (0.32±0.11 mm2). Colocalization planimetric analysis showed that tissue factor was located in intact macrophages (0.07±0.02 mm2) as well as in KP-1–positive acellular core (0.25±0.09 mm2). Linear regression analysis displayed a high correlation between KP-1–positive areas and tissue factor in the atheromatous gruel (r=.98, P<.0001) (Fig 5Down).



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Figure 5. Association of lipid-rich macrophage area (mm2) identified by trichrome staining and lipid-rich tissue factor area (mm2) identified by a polyclonal antibody in coronary atherectomy specimens from 50 patients with unstable angina, which can be described by the equation y=1.064511x+0.01056 (r=.98, P<.00001, SD of regression=0.0637, variance of residual=0.16983).

Correlations of Tissue Factor Within Thrombotic Areas (Unstable Angina)
Thrombus was identified in 24 of 50 samples (49%). Macrophages were found in 19 of 24 samples (79%). Linear regression analysis displayed a high correlation between macrophages in thrombus and the total thrombotic area (r=.85, P<.0001) (Fig 6Down). Tissue factor was identified in all thrombus areas (0.11±0.03 mm2). Linear regression analysis displayed a high correlation between macrophages and tissue factor in thrombus (r=.64, P<.0001).



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Figure 6. Association of macrophages in thrombus area (mm2) identified by KP-1 immunostaining and thrombus area (mm2) identified by the trichrome stain in 50 coronary atherectomy specimens from patients with unstable angina, which can be described by the equation y=0.692776x-0.025722 (r=.85, P<.0001, SD of regression=0.1207, variance of residual=0.69926).


*    Discussion
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up arrowAbstract
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up arrowMethods
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*Discussion
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Tissue factor, presumably the primary initiator of thrombogenesis and thrombin generation in vivo, is a specific transmembrane glycoprotein expressed by circulating monocytes, monocyte-derived macrophages, endothelial cells, and SMCs.8 9 20 21 Coronary thrombosis plays a major role in the pathophysiology of acute ischemic syndromes, and tissue factor may be responsible for this increased coronary thrombogenicity.1 2 3 7 10 This study was designed to identify tissue factor location and cellular correlations of tissue factor content by a systematic quantification approach for specific cellular components in human coronary plaque tissue from patients with stable and unstable angina.

The results reveal that coronary tissue factor content was larger in tissue from patients with unstable angina than in tissue from patients with stable angina (P=.0001). In addition, total macrophage content was also significantly larger in tissue from patients with unstable angina (P=.002), as previously demonstrated by our group.4 Tissue factor location within the plaque varied according to the clinical syndrome. In patients with stable angina, planimetric colocalization analysis showed that tissue factor was located predominantly in the acellular component of the plaque. However, multiple regression analysis did not identify any histological predictors for tissue factor content in tissue from patients with stable angina. In patients with unstable angina, planimetric colocalization analysis showed that tissue factor was located predominantly in the cellular component of the plaque. Multiple regression analysis revealed that coronary tissue factor content correlated significantly with macrophage and SMC areas (r=.83, P<.0001) only in tissue from patients with unstable angina. In this group of patients, tissue factor colocalized with intact macrophages (27±4%) and with macrophage-derived acellular debris (11±2%). Furthermore, macrophages correlated with tissue factor in both lipid-rich (r=.98, P<.0001) and thrombus areas (r=.64, P<.0001).

Disruption of coronary atherosclerotic plaques with exposure of the lipid-rich gruel to flowing blood is an important mechanism in the pathophysiology of acute coronary syndromes.1 2 3 Macrophages may be involved in the process of plaque rupture.22 23 Consequently, coronary plaques with a high content of macrophages may have both a higher risk for plaque rupture and a higher propensity for thrombosis related to an increased macrophage expression of tissue factor. Macrophage content of atherosclerotic plaques may be a link between the two phenomena, ie, plaque rupture and thrombosis.

The relative thrombogenicity of atherosclerotic plaque components was elegantly studied by Fernandez-Ortiz et al,6 who found that the lipid core was the most potent substrate for platelet-rich thrombus formation in vitro. Recently, Toschi et al24 evaluated tissue factor thrombogenicity in the atheromatous gruel from human arterial segments exposed to flowing blood. 111In-platelet deposition (platelets/cm2x106) was highest in the gruel (712±213), followed by normal adventitia (203±58) and normal tunica media (134±41).

Human plaques from carotid endarterectomy specimens express tissue factor mRNA and protein in the peripheral macrophage-like cells adjacent to cholesterol clefts as well as in intimal SMCs.7 However, the correlation between tissue factor and cellular areas of macrophages and SMCs by quantified planimetry in patients with stable and unstable coronary syndromes has not been analyzed. We systematically studied and quantified the cellular correlations of tissue factor in coronary specimens of patients with stable and unstable angina. The high correlation of tissue factor with macrophage areas within the atheromatous core in patients with unstable angina suggests that lipid gruel thrombogenicity is related to macrophage expression of tissue factor. Tissue factor in the gruel was found in intact macrophages (20±1%) as well as in macrophage-derived acellular debris (80±1%), suggesting that macrophages contribute not only to the bulk of the atheromatous core25 but also to its thrombogenicity. Tissue factor was also identified in all thrombus areas in tissue from patients with unstable angina. Colocalization planimetric analysis displayed a high incidence of macrophages in thrombus (79%). Linear regression analysis demonstrated a high correlation between macrophages and tissue factor in thrombus (r=.64, P<.0001). Fresh mural thrombus is highly thrombogenic26 and may be responsible for coronary reocclusion after thrombolysis. Tissue factor inhibition prevents reocclusion after thrombolysis in a rabbit model of carotid artery thrombosis and might be suitable as adjunctive antithrombotic therapy in the treatment of acute coronary syndromes.27

In fact, platelet deposition is increased two to four times on residual thrombus compared with deeply injured arterial wall. Although thrombus formation triggered by residual thrombosis is inhibited by specific antithrombin treatment,26 the roles of tissue factor, macrophages, and SMCs in this phenomenon are unclear and remain to be elucidated.

Coronary tissue classification by the modified trichrome staining showed an increased content of hypercellular tissue in coronary samples from patients with unstable angina above that of plaque tissue from patients with stable angina (P=.0001). Planimetric analysis in tissue from patients with unstable angina showed that tissue factor colocalized with {alpha}-actin–positive SMCs (28±4%) followed by KP-1–negative/{alpha}-actin–negative cells. Multiple regression analysis identified SMCs as an independent predictor for tissue factor content in patients with unstable angina (r=.68, P<.0001), suggesting that these cells may also play a role as a thrombogenic substrate in patients with acute coronary syndromes.

Recently, SMCs have been implicated in the pathophysiology of unstable angina. Flugelman et al12 found abundant SMCs in coronary specimens from patients with unstable angina, suggestive of the importance of these cells in the mechanisms of transformation from stable to unstable coronary syndromes. Likewise, directional atherectomy studies have shown that SMCs are increasingly present in complex coronary lesions, reaching 100% in thrombosed plaques from patients with unstable angina at rest.13 14 Furthermore, autopsy studies have shown that 40% to 45% of fatal coronary thrombosis can occur with denuded or superficially eroded plaques with SMC-rich fibrous caps.15 16 In these circumstances, SMCs may be the active clotting substrate, but thrombogenicity of SMCs is not completely understood and remains to be elucidated. The expression of tissue factor by vascular SMCs is rapidly induced by growth factors and thrombin in vitro and by vascular injury in vivo.19 20 Moreover, the reproduced finding of SMCs in coronary tissue from patients with unstable angina12 13 14 and the positive correlation between tissue factor and SMCs in the same group of patients reported in this study suggest that the biological injury responsible for unstable syndromes may be associated with activation and proliferation of SMCs, but further studies are needed to completely resolve this issue.

Study Limitations
Several limitations have to be addressed. First, the activity of tissue factor was not evaluated in this study. At the time this study was designed, the assay to evaluate tissue factor activity was in process, and we decided to quantify tissue factor content only. More recently, Marmur et al28 examined functional tissue factor activity in human coronary atherectomy specimens using a factor Xa generation assay. They found a high correlation between tissue factor activity and the tissue factor antibody staining. Second, T cell and mast cell antibodies were not used and precluded specific identification of these cells. Previous work has shown that activated T cells and mast cells may be involved in the process of plaque rupture.5 29 Tissue factor colocalized with KP-1–negative/{alpha}-actin–negative cells (14±3%). Loss of expression of {alpha}-actin by SMCs is associated with a phenotype change observed as a response to vascular injury.30 These cells were found in fibrocellular and hypercellular areas, and trichrome morphology suggests that they were mostly SMCs. However, other cell types cannot be excluded.

Conclusions
The results of this study support the hypothesis that macrophages and SMCs are responsible for coronary plaque tissue factor content in patients with unstable angina. Within the lipid gruel, tissue factor is associated with macrophages and macrophage-derived membranous debris.24 In other areas of the plaque, SMCs correlated with tissue factor content, suggesting a cell-mediated expression of thrombogenicity in patients with unstable angina. Despite potential sampling limitations,31 these results suggest that macrophages and SMCs play a crucial role in the thrombogenic response of atherosclerotic plaque tissue from patients with acute coronary syndromes.


*    Acknowledgments
 
Dr Bernardi was supported in part by the Anchorena Hospital in Buenos Aires, Argentina. We thank Veronica Gulle for her help in preparing tissue sections, John B. Newell for statistical analysis, Drs Vivian M. Abascal, Erling Falk, and Henry H. Ting for thoughtful comments, Dr Mark J. Semigran for technical support, and Robert E. Holt for editorial assistance.


*    Footnotes
 
Presented in part at the 45th Annual Scientific Sessions of the American College of Cardiology, Orlando, Fla, March 24-27, 1996, and published in abstract form (J Am Coll Cardiol. 1996;27:306A).

Received January 25, 1996; revision received July 24, 1996; accepted July 30, 1996.


*    References
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up arrowAbstract
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up arrowResults
up arrowDiscussion
*References
 
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13. Wilson JM, Capek P, McAllister HA, Vaughn WK, Ferguson JJ, Club FJ, Buja LM, Willerson JT. Coronary lesion histology in stable, unstable and evolving angina pectoris. J Am Coll Cardiol. 1995;(special issue):279A. Abstract.

14. Mann JM, Kaski JC, Arie S, Pereira WI, Pileggi F, Davies MJ. Plaque constituents in patients with stable and unstable angina: an atherectomy study. J Am Coll Cardiol. 1995;(special issue):34A. Abstract.

15. van der Wal AC, Becker AE, van der Loos CM, Das PK. Site of intimal rupture or erosion of thrombosed coronary atherosclerotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology. Circulation. 1994;89:36-44.[Abstract/Free Full Text]

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M. Aikawa, S. J. Voglic, S. Sugiyama, E. Rabkin, M. B. Taubman, J. T. Fallon, and P. Libby
Dietary Lipid Lowering Reduces Tissue Factor Expression in Rabbit Atheroma
Circulation, September 14, 1999; 100(11): 1215 - 1222.
[Abstract] [Full Text] [PDF]


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Eur Heart JHome page
P. W. H. M. Verheggen, M. P. M. de Maat, V. M. Cats, F. Haverkate, A. H. Zwinderman, C. Kluft, and A. V. G. Bruschke
Inflammatory status as a main determinant of outcome in patients with unstable angina, independent of coagulation activation and endothelial cell function
Eur. Heart J., April 2, 1999; 20(8): 567 - 574.
[Abstract] [PDF]


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Arterioscler. Thromb. Vasc. Bio.Home page
M. M. E. D. van den Eijnden, J. T. van Noort, L. Hollaar, A. van der Laarse, and R. M. Bertina
Cholesterol or Triglyceride Loading of Human Monocyte-Derived Macrophages by Incubation With Modified Lipoproteins Does Not Induce Tissue Factor Expression
Arterioscler Thromb Vasc Biol, February 1, 1999; 19(2): 384 - 392.
[Abstract] [Full Text] [PDF]


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Cardiovasc ResHome page
D. E. Gutstein and V. Fuster
Pathophysiology and clinical significance of atherosclerotic plaque rupture
Cardiovasc Res, February 1, 1999; 41(2): 323 - 333.
[Abstract] [Full Text] [PDF]


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Cardiovasc ResHome page
A. C. van der Wal and A. E. Becker
Atherosclerotic plaque rupture - pathologic basis of plaque stability and instability
Cardiovasc Res, February 1, 1999; 41(2): 334 - 344.
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Cardiovasc ResHome page
C. Depre, X. Havaux, J. Renkin, J. L. J. Vanoverschelde, and W. Wijns
Expression of inducible nitric oxide synthase in human coronary atherosclerotic plaque
Cardiovasc Res, February 1, 1999; 41(2): 465 - 472.
[Abstract] [Full Text] [PDF]


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CirculationHome page
Z. Mallat, B. Hugel, J. Ohan, G. Leseche, J.-M. Freyssinet, and A. Tedgui
Shed Membrane Microparticles With Procoagulant Potential in Human Atherosclerotic Plaques : A Role for Apoptosis in Plaque Thrombogenicity
Circulation, January 26, 1999; 99(3): 348 - 353.
[Abstract] [Full Text] [PDF]


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Arterioscler. Thromb. Vasc. Bio.Home page
B. Engelmann, S. Zieseniss, K. Brand, S. Page, A. Lentschat, A. J. Ulmer, and E. Gerlach
Tissue Factor Expression of Human Monocytes Is Suppressed by Lysophosphatidylcholine
Arterioscler Thromb Vasc Biol, January 1, 1999; 19(1): 47 - 53.
[Abstract] [Full Text] [PDF]


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J Am Coll CardiolHome page
G. Dangas, R. Mehran, P. C. Harpel, S. K. Sharma, S. M. Marcovina, G. Dube, J. A. Ambrose, and J. T. Fallon
Lipoprotein(a) and inflammation in human coronary atheroma: association with the severity of clinical presentation
J. Am. Coll. Cardiol., December 1, 1998; 32(7): 2035 - 2042.
[Abstract] [Full Text] [PDF]


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CirculationHome page
N. Marx, F.-J. Neumann, D. Zohlnhofer, T. Dickfeld, A. Fischer, S. Heimerl, and A. Schomig
Enhancement of Monocyte Procoagulant Activity by Adhesion on Vascular Smooth Muscle Cells and Intercellular Adhesion Molecule-1–Transfected Chinese Hamster Ovary Cells
Circulation, September 1, 1998; 98(9): 906 - 911.
[Abstract] [Full Text] [PDF]


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CirculationHome page
S. D. Gertz, J. T. Fallon, R. Gallo, M. B. Taubman, S. Banai, W. L. Barry, L. W. Gimple, Y. Nemerson, S. Thiruvikraman, S. S. Naidu, et al.
Hirudin Reduces Tissue Factor Expression in Neointima After Balloon Injury in Rabbit Femoral and Porcine Coronary Arteries
Circulation, August 11, 1998; 98(6): 580 - 587.
[Abstract] [Full Text] [PDF]


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Vasc MedHome page
P. V Tisi and C. P Shearman
Biochemical and inflammatory changes in the exercising claudicant
Vascular Medicine, August 1, 1998; 3(3): 189 - 198.
[Abstract] [PDF]


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Vasc MedHome page
P. K Shah
Role of inflammation and metalloproteinases in plaque disruption and thrombosis
Vascular Medicine, August 1, 1998; 3(3): 199 - 206.
[Abstract] [PDF]


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Vasc MedHome page
P. Libby
The interface of atherosclerosis and thrombosis: basic mechanisms
Vascular Medicine, August 1, 1998; 3(3): 225 - 229.
[Abstract] [PDF]


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Vasc MedHome page
V. Fuster, J. J. Badimon, and J. H Chesebro
Atherothrombosis: mechanisms and clinical therapeutic approaches
Vascular Medicine, August 1, 1998; 3(3): 231 - 239.
[Abstract] [PDF]


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StrokeHome page
S. Jander, M. Sitzer, R. Schumann, M. Schroeter, M. Siebler, H. Steinmetz, and G. Stoll
Inflammation in High-Grade Carotid Stenosis : A Possible Role for Macrophages and T Cells in Plaque Destabilization
Stroke, August 1, 1998; 29(8): 1625 - 1630.
[Abstract] [Full Text] [PDF]


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CirculationHome page
P. Theroux and V. Fuster
Acute Coronary Syndromes : Unstable Angina and Non–Q-Wave Myocardial Infarction
Circulation, March 31, 1998; 97(12): 1195 - 1206.
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CirculationHome page
S. S. Patel, R. Thiagarajan, J. T. Willerson, and E. T. H. Yeh
Inhibition of {alpha}4 Integrin and ICAM-1 Markedly Attenuate Macrophage Homing to Atherosclerotic Plaques in ApoE-Deficient Mice
Circulation, January 13, 1998; 97(1): 75 - 81.
[Abstract] [Full Text] [PDF]


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J. Biol. Chem.Home page
A. D. Schecter, B. J. Rollins, Y. J. Zhang, I. F. Charo, J. T. Fallon, M. Rossikhina, P. L. A. Giesen, Y. Nemerson, and M. B. Taubman
Tissue Factor Is Induced by Monocyte Chemoattractant Protein-1 in Human Aortic Smooth Muscle and THP-1 Cells
J. Biol. Chem., November 7, 1997; 272(45): 28568 - 28573.
[Abstract] [Full Text] [PDF]


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CirculationHome page
F. Mach, U. Schonbeck, J.-Y. Bonnefoy, J. S. Pober, and P. Libby
Activation of Monocyte/Macrophage Functions Related to Acute Atheroma Complication by Ligation of CD40 : Induction of Collagenase, Stromelysin, and Tissue Factor
Circulation, July 15, 1997; 96(2): 396 - 399.
[Abstract] [Full Text]


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CirculationHome page
P. R. Moreno, V. H. Bernardi, J. Lopez-Cuellar, J. B. Newell, C. McMellon, H. K. Gold, I. F. Palacios, V. Fuster, and J. T. Fallon
Macrophage Infiltration Predicts Restenosis After Coronary Intervention in Patients With Unstable Angina
Circulation, December 15, 1996; 94(12): 3098 - 3102.
[Abstract] [Full Text]


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J. Biol. Chem.Home page
A. a. Belaaouaj, A. Li, T.-C. Wun, H. G. Welgus, and S. D. Shapiro
Matrix Metalloproteinases Cleave Tissue Factor Pathway Inhibitor. EFFECTS ON COAGULATION
J. Biol. Chem., August 25, 2000; 275(35): 27123 - 27128.
[Abstract] [Full Text] [PDF]


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CirculationHome page
P. R. Moreno, R. A. Lodder, K. R. Purushothaman, W. E. Charash, W. N. O'Connor, and J. E. Muller
Detection of Lipid Pool, Thin Fibrous Cap, and Inflammatory Cells in Human Aortic Atherosclerotic Plaques by Near-Infrared Spectroscopy
Circulation, February 26, 2002; 105(8): 923 - 927.
[Abstract] [Full Text] [PDF]


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Arterioscler. Thromb. Vasc. Bio.Home page
R. Baetta, M. Camera, C. Comparato, C. Altana, M. D. Ezekowitz, and E. Tremoli
Fluvastatin Reduces Tissue Factor Expression and Macrophage Accumulation in Carotid Lesions of Cholesterol-Fed Rabbits in the Absence of Lipid Lowering
Arterioscler Thromb Vasc Biol, April 1, 2002; 22(4): 692 - 698.
[Abstract] [Full Text] [PDF]


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