606
JACC Vol. 32, No. 3
September 1998:606 –12
Mast Cell Infiltration in Acute Coronary Syndromes: Implications for
Plaque Rupture
MAIJA KAARTINEN, MD,*† ALLARD C. VAN DER WAL, MD,‡ CHRIS M. VAN DER LOOS, PHD,‡
JAN J. PIEK, MD,§ KAREL T. KOCH, MD,§ ANTON E. BECKER, MD, FACC,‡
PETRI T. KOVANEN, MD*
Helsinki, Finland and Amsterdam, the Netherlands
Objectives. To define the role of mast cells in plaque destabilization.
Background. Inflammation is an essential feature of human
coronary plaques. Macrophages and T lymphocytes are considered to contribute to destabilization of the plaques. The role of
mast cells in this setting is less well studied. We therefore counted
the mast cells in coronary atherectomy specimens from patients
with chronic stable angina, unstable angina and severe unstable
angina.
Methods. Patients studied had chronic stable angina (group 1,
n 5 11), “stabilized” unstable angina (group 2; Braunwald’s class
I and II, n 5 11) and “refractory” unstable angina (group 3;
Braunwald’s class III, n 5 7). Samples of culprit lesions (n 5 29)
were obtained by directional atherectomy, snap-frozen and analyzed immunohistochemically. The numbers of mast cells and T
lymphocytes per square millimeter squared were counted and the
areas containing macrophages and smooth muscle cells were
measured by computed planimetry.
Results. We found that the numbers of mast cells and T
lymphocytes increased from group 1 through groups 2 to 3.
Specimens from group 3 also contained the largest numbers of
tumor necrosis factor alpha (TNF-a)-positive mast cells and of
matrix metalloproteinase (MMP)-9 (92 kD gelatinase)-positive
macrophages.
Conclusions. Unstable coronary syndromes are associated with
increased numbers of mast cells in culprit lesions. Activated mast
cells secrete neutral proteases capable of degrading the extracellular matrix and TNF-a, capable of stimulating macrophages to
synthesize MMP-9. Our observations suggest that mast cells, in
addition to macrophages, contribute to matrix degradation and,
hence, to progression of coronary syndromes.
(J Am Coll Cardiol 1998;32:606 –12)
©1998 by the American College of Cardiology
The most important mechanism underlying the sudden onset
of acute coronary syndromes, including unstable angina and
acute myocardial infarction, is erosion or rupture of a coronary
plaque (1,2). The risk of plaque erosion or rupture appears to
depend critically on the cellular and extracellular composition
of the plaque (2). This notion is supported by the observation
that macrophage-rich areas are more frequently found in
patients with unstable angina and non-Q-wave myocardial
infarction, and that inflammatory cells, including mast cells, T
lymphocytes and macrophages, accumulate at sites of plaque
rupture and erosion (3– 6).
Mast cells are filled with neutral proteases and in many
tissues are the major source of these enzymes (7). Upon mast
cell activation, the two neutral proteases of mast cells, tryptase
and chymase, are released (8) and are able to activate the
matrix metalloproteinases (MMPs) secreted by macrophages
and smooth muscle cells (9,10). This can lead to collagen
degradation, which may weaken the fibrous cap, with subsequent plaque rupture. It is of interest, therefore, that mast cells
have been identified not only at the sites of rupture and
erosion, but also in the vulnerable shoulder regions of stable
atherosclerotic plaques in patients without angina pectoris
(6,11). Thus, the question arose whether mast cells play an
active part in the process of plaque destabilization prior to
erosion or rupture. In an attempt to answer this question, we
studied atherectomy specimens from patients suffering from
different stages of angina pectoris. The sections were immunostained for mast cells. To obtain insight into the cellular
environment in which mast cells reside in the atherosclerotic
plaques associated with these different coronary syndromes, we
also stained sections for T lymphocytes, macrophages and
smooth muscle cells.
Mast cells in rupture-prone areas of human coronary
atheromas contain tumor necrosis factor alpha (TNF-a) (12),
a powerful proinflammatory cytokine that is able to stimulate
the production of MMP-9 (92-kD gelatinase) by macrophages
From *the Wihuri Research Institute and †the Division of Cardiology,
Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland; and the Departments of ‡Cardiovascular Pathology and §Cardiology,
Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands. Dr. Kaartinen is supported by the Finnish Foundation of Cardiovascular
Research, Helsinki, Finland.
Manuscript received October 15, 1997; revised manuscript received April 30,
1998, accepted May 13, 1998.
Address for correspondence: Dr. Petri T. Kovanen, Wihuri Research
Institute, Kalliolinnantie 4, 00140 Helsinki, Finland.
©1998 by the American College of Cardiology
Published by Elsevier Science Inc.
0735-1097/98/$19.00
PII S0735-1097(98)00283-6
JACC Vol. 32, No. 3
September 1998:606 –12
607
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
Table 1. Monoclonal Antibodies Used in This Study
Abbreviations and Acronyms
DCA 5 directional coronary atherectomy
MMP 5 matrix metalloproteinase
TNF-a 5 tumor necrosis factor alpha
in vitro (13). Since macrophages in unstable coronary plaques
contain MMP-9 (14), we studied the atherectomy specimens
for the presence of TNF-a positive mast cells (tryptase-positive
cells) and MMP-9-positive macrophages (CD68-positive cells).
Working
Dilution
Supplier
Mast cells
T lymphocytes
Macrophages
1.5 mg/ml
0.3 mg/ml
4 mg/ml
Chemicon
Becton Dickinson
Dako
a-Smooth muscle actin
TNF-a
MMP-9
2 mg/ml
0.1 mg/ml
2 mg/ml
Dako
Otsuka
Chemicon
Antibody
Antitryptase
Leu 4 (CD3)
EBM-11*
(CD68)
1A4*
Anti-TNF-a
Anti-MMP-9
Cell Specificity
* 5 double staining. Dako (Glostrup, Denmark); Becton Dickinson (San
Jose, CA); Chemicon (Temecula, CA); Otsuka Pharmaceutical Co., Ltd (Tokushima, Japan).
Methods
Coronary Atherectomy
Atherectomy specimens were obtained from patients who
underwent directional coronary atherectomy (DCA) for a
single de novo (primary) stenosis as the only intervention (at
the Department of Cardiology, Academic Medical Center,
University of Amsterdam, the Netherlands). The selection of
patients for DCA was based on angiographic criteria, which
included proximally located eccentric lesions and a vessel
diameter of 3 mm or more. Culprit lesions were identified on
the basis of their clinical and electrocardiographic manifestations. Twenty-nine consecutive patients (comprising 8% of the
total angioplasty population, including percutaneous transluminal coronary angioplasty) met the following inclusion criteria for this study: (group 1) chronic stable angina, Canadian
Society classification, classes I–III (n 5 11); (group 2) “stabilized” unstable angina, Braunwald’s classification classes I and
II (new onset, accelerating or angina pectoris at rest, but not
within the preceding 48 hours) (n 5 11); and (group 3)
“refractory” unstable angina, Braunwald’s classification class
III (angina pectoris at rest, acute within 48 hours; in our series
these patients were dependent on intravenous treatment with
nitrates and heparin) (n 5 7). One patient in group 2 and three
patients in group 3 had postinfarction angina. No patients with
lesions in vein grafts or restenosis lesions were included.
Immunocytochemistry
After the DCA procedure, atherectomy tissues were carefully oriented in a drop of Tissue Tek embedding fluid in such
a way that the largest tissue area was available for cutting
sections, and immediately frozen in liquid nitrogen and stored
at 280°C. For immunocytochemistry, frozen sections were cut
serially at 5 mm, fixed in acetone and air-dried. Details of the
monoclonal antibodies used in this study are summarized in
Table 1. Mast cells were stained by a single indirect immunoperoxidase method, as previously described (11,15). For detection of T lymphocytes and anti-MMP-9 reactivity, a routine
three-step indirect immunoperoxidase assay was used. In both
methods, horseradish peroxidase activity was visualized with
3-amino-9-ethyl carbazole, and the sections were counterstained with hematoxylin for histomorphologic evaluation of
the atherosclerotic plaque. After treatment with hematoxylineosin and elastic van Gieson stains, all specimens were
screened for the presence of thrombus, atheroma (extracellular lipid core), fibrous tissue (of fibrocellular of fibrosclerotic
type) and media. Anti-TNF-a reactivity in mast cells was
established with an anti-TNF-a/antitryptase immunodouble
staining method based on antibodies from different species
(TNF-a: rabbit; tryptase: mouse). Smooth muscle cells and
macrophages were detected simultaneously in the same sections, using an immunodouble staining method based on the
application of two antibodies of different IgG subclasses.
Briefly, a cocktail of antismooth muscle a-actin, 1A4 (IgG2a),
and anti-CD68, EBM-11 (IgG1), was applied, followed by a
second cocktail of secondary antibodies consisting of goat
antimouse IgG2a/biotin and goat antimouse IgG1/alkaline
phosphatase (both Southern Biotechnology Associations, Birmingham, AL) and a final step with strep/b-galactosidase
(Boehringer, Mannheim, Germany). b-Galactosidase activity
was developed as turquoise (in smooth muscle cells), using
X-gal (Boehringer) as substrate and ferri-ferro cyanide as
chromogen and then, by washing with alkaline phosphatase,
fuchsin was developed as red (in macrophages), using a NEW
fuchsin detection kit (Dako, Glostrup, Denmark).
Morphometry
The total area of each tryptase- and CD3-stained section
was assessed planomorphometrically. The numbers of immunopositive mast cells and T lymphocytes were counted at 3 100
magnification throughout the entire section and expressed as
numbers of cells per square millimeter. Because of the large
numbers and close apposition of the macrophages and of the
smooth muscle cells in the immunostained sections, it was not
possible to count these individual cells separately. Therefore,
in the atherectomy sections that were immunodouble-stained
with antiCD68 and with anti-a-actin, the tissue areas occupied
by immunostained cytoplasm of either macrophages or smooth
muscle cells were quantified planimetrically. The total area of
each double-stained section was outlined on a video screen
connected to a personal computer provided with image analysis software. The surface area occupied by immunostained
608
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
JACC Vol. 32, No. 3
September 1998:606 –12
Table 2. Plaque Histology in Atherectomy Specimens
Patient
Group
Total Area
(mm2)
Thrombus
Atheroma
Fibrous Tissue
Media
Group 1
Group 2
Group 3
6.10 6 2.67
6.67 6 4.01
5.73 6 2.58
3/11 (27%)
8/11 (72%)
6/7 (86%)
4/11 (36%)
8/11 (72%)
6/7 (86%)
11/11 (100%)
11/11 (100%)
7/7 (100%)
4/11 (38%)
4/11 (38%)
2/7 (29%)
Group 1: chronic stable angina; group 2: unstable angina, Braunwald’s classes I and II; group 3: unstable angina
pectoris in patients requiring intravenous treatment with nitrates and heparin, Braunwald’s class III. Hematoxylin-eosin
and elastic van Gieson staining were used.
(red) macrophages was measured automatically using a blue
filter on the microscope which faded out the blue-stained
smooth muscle cells completely, and, similarly, the surface area
occupied by immunostained (blue) smooth muscle cells was
measured using a red filter which faded out the red-stained
macrophages. Thereafter smooth muscle cell areas and macrophage areas were calculated as percentages of the total tissue
area.
Statistical Analysis
The grouping based on the severity of symptoms was used
as an explanatory variable. Poisson regression analysis was
used to model number of cells (mast cells, TNF-a-positive
mast cells, T lymphocytes and those macrophages that were
MMP-9-positive) per tissue area (per square millimeter) as
response variable. The usage of this model was based on the
assumption that the numbers of cells per tissue area were
distributed according to a Poisson distribution. The areas of
samples were used as weight in Poisson regression model.
Logistic regression analysis was applied when the proportion of
macrophage or smooth muscle cell areas of total area were
as-used responses. Because the proportion of area is always
between zero and one, the choice of logistic regression analysis
is plausible (16). Differences were considered statistically
significant when p , 0.05.
Results
Plaque Histology
Table 2 shows the histologic findings for each of the three
groups. A thrombus was present in 27%, 72% and 86% of the
atherectomy samples, respectively. Interestingly, these frequencies coincided with the presence of an extracellular lipid
core (atheroma). All atherectomy samples contained fibrous
tissue and, on average, one third of the samples in each group
also contained some medial tissue.
Qualitative Immunocytochemistry
Figure 1 illustrates an atherectomy section stained immunohistochemically for macrophages, smooth muscle cells, mast
cells and T lymphocytes. Inflammatory cells were identified in
all three groups (group 1: chronic stable angina; group 2:
unstable angina, Braunwald’s class I and II: and group 3:
unstable angina pectoris in patients requiring intravenous
treatment with nitrates and heparin, Braunwald’s class III).
Analysis of the cellular composition and distribution in the
atherectomy samples, using immunodouble staining, revealed
striking zonal distributions of macrophages and smooth muscle
cells: most areas containing large quantities of macrophages
were almost devoid of smooth muscle cells, whereas areas rich
in smooth muscle cells contained few macrophages, T lymphocytes or mast cells. Comparison of serial sections of each
atherectomy specimen revealed that macrophages, T lymphocytes and mast cells were almost always colocalized in the same
tissue areas. Furthermore, mast cells and T lymphocytes were
often found in clusters, with a predilection for the border zone
between macrophage-rich areas and smooth muscle cell-rich
areas. In a few instances, however, we found tightly packed
macrophages infiltrating large areas from which T lymphocytes
and mast cells were completely absent.
Analyses of the cellular composition of each of the
histologically defined components of the plaque led to the
following observations. Most inflammatory cells, including
macrophages, T lymphocytes and mast cells, were present in
the fibrocellular tissue component of the specimens. In
contrast, sections containing fibrosclerotic intimal tissue and
media were virtually always devoid of inflammatory cells.
Macrophages, particularly those of foam cell type, were also
present in atheromas. In these areas, mast cells and T
lymphocytes were seldom seen. Fragments of thrombus
contained variable quantities of macrophages and some T
lymphocytes and mast cells.
Quantitative Immunocytochemistry
For each patient in each group, the numbers of mast cells
and T lymphocytes per square millimeter (upper panel) and
the percentages of immunostained macrophages and smooth
muscle cell areas (lower panel) are given in Figure 2. The
number of mast cells per square millimeter clearly tended to
increase from group 1 through groups 2 and 3. The mast cell
densities ranged from 0 to 10 cells/mm2. The values represent
means obtained by counting all the mast cells in the total area
from samples ranging in size from 2 to 16.5 mm2. As stated
above, the distribution of mast cells in these samples was highly
uneven. In the clusters, the densities of mast cells typically
varied between 30 and 50 cells/mm2, the highest density
observed being 96 mast cells/mm2. Likewise, the number of T
JACC Vol. 32, No. 3
September 1998:606 –12
lymphocytes per millimeter squared gradually increased from
group 1 through group 2 and group 3. The areas occupied by
macrophages and smooth muscle cells in groups 1, 2 and 3
did not differ significantly. Finally, we examined the relationships between the number of mast cells and the numbers
or areas of other types of intimal cells in the atherectomy
samples. As expected, there was a positive correlation
between the numbers of T lymphocytes and mast cells, and
a negative correlation between the areas occupied by
smooth muscle cells and the numbers of mast cells (not
shown). However, there were no significant correlations
between the areas occupied by macrophages and the numbers of mast cells.
Anti-TNF-a/antitryptase doublestaining showed that, in all
three groups, most of the mast cells contained TNF-a and a
fraction of the macrophages contained MMP-9. The quantities
of both TNF-a-positive mast cells and the MMP-9-positive
macrophages were highest in group 3 (Fig. 3). Thus, the
number of TNF-a-positive mast cells per square millimeter
was 0.49 6 0.55 (mean 6 SD) in group 1, 1.10 6 1.56 in groups
2, and 2.56 6 2.79 in group 3. The corresponding numbers for
MMP-9-positive macrophages were 1.84 6 2.08, 2.18 6 1.61
and 9.64 6 4.07.
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
609
Figure 1. a, Frozen section of part of an atherectomy specimen
obtained from a patient with unstable angina (group 2). The section is
immunodouble-stained for macrophages (anti-CD68) in red and for
smooth muscle cells (anti-alpha actin) in blue. The boxed area is
enlarged in b through d. Original magnification 330. b, Inflammatory
area containing closely packed macrophages (red) and sparse smooth
muscle cells (blue). c, Adjacent section stained for mast cells (antitryptase). d, Adjacent serial section stained for T lymphocytes (antiCD3). Original magnification b through d, 390.
Discussion
In previous studies we have shown that mast cells occur in
the shoulder region of stable atherosclerotic plaques as well as
at sites of plaque rupture (6,11). The present study demonstrates that the number of mast cells tends to increase with the
clinical severity of the coronary syndromes. The lesions obtained from patients with unstable angina of Braunwald’s class
III contained significantly more mast cells than those obtained
from patients with chronic stable angina. These findings thus
strongly suggest that mast cells contribute to the process of
plaque destabilization. Then, the important question arises
whether mast cells (and T lymphocytes and macrophages)
enter the lesion before or after the plaque rupture. Mast cells
infiltrate not only the sites of coronary arteries at which
610
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
JACC Vol. 32, No. 3
September 1998:606 –12
Figure 3. Graph showing the numbers per square millimeter of
TNF-a-positive mast cells and of MMP-9-positive macrophages in
atherectomy specimens for each patient group (see Fig. 2). Individual
data points, means and p values are shown.
Figure 2. Graphs showing the numbers per square millimeter of mast
cells and T lymphocytes (upper panel) and the percentages of immunostained macrophage and smooth muscle cell areas (lower panel) in
the atherectomy specimens of each group (group 1: chronic stable
angina; group 2: unstable angina, Braunwald’s classes I and II; and
group 3: unstable angina pectoris in patients requiring intravenous
treatment with nitrates and heparin, Braunwald’s class III). Individual
data points, means and p values are shown.
erosion or rupture has occurred, but also sites of coronary
plaques susceptible to erosion or rupture (11), that is, they
invade before an actual intimal event. The same applies also
for macrophages and T lymphocytes (11). Hence, there is
much evidence to suggest that the infiltrates of inflammatory
cells are present in the lesions prior to erosion or rupture,
rather than part of an inflammatory response to rupture
initiated by some other process.
Mast cell degranulation. To initiate matrix degradation,
mast cells have to be stimulated to secrete their neutral
proteases. The best understood immunologic stimulus leading
to degranulation of human mast cells is their activation when
the IgE molecules on their surfaces bind a relevant antigen
(17). The development of cardiovascular disease is associated
with elevated levels of IgE, suggesting that IgE-mediated
events play a role in the pathogenesis of these diseases (18,19).
A second pathway leading to degranulation of mast cells in the
arterial intima—which appears more likely in the setting of
atherosclerosis—is their stimulation by other immunologically
activated cells, such as T lymphocytes (20) or macrophages
(21). Indeed, mast cells were found to be accompanied by T
lymphocytes and by macrophages at the sites of coronary
arteries where erosion or rupture had occurred (6). Probably
even more important, the degree of mast cell stimulation
(degranulation) was shown to be highest at those sites where
the numbers of other inflammatory cells were highest (6). In
the present study we did not determine the degree of mast cell
degranulation, as degranulation may have been caused artificially by mechanical trauma associated with the atherectomy
procedure. However, the present study did show that, in
unstable angina, mast cells were accompanied by T lymphocytes and macrophages, and that the more severe the symptoms of angina pectoris, the greater were the number of the T
lymphocytes surrounding the mast cells. Recently, in a similar
retrospective study of DCA specimens of patients with various
ischemic coronary syndromes, we showed that the increase in
the numbers of macrophages and T lymphocytes with the
severity of the angina is accompanied by an increase in human
leukocyte antigen-DR expression on the cells (5). This indicates that active inflammation plays a role in the progression of
angina pectoris. A major conclusion derived from the present
study is that mast cells play an integral part in this active
inflammatory process. Moreover, the study implies that local
conditions include the active inflammation (secretion of cytokines) necessary for mast cell stimulation.
Extracellular matrix degradation. Together with previous
data, the present observations support the concept that mast
cells play a role in increasing the activity of the enzymes
required for extracellular matrix digestion (the MMPs). Recent immunocytochemical and in situ hybridization studies of
human atherosclerotic plaques have revealed that the macrophages and smooth muscle cells of the plaques synthesize
JACC Vol. 32, No. 3
September 1998:606 –12
MMP-1, MMP-3 and MMP-9 (92-kD gelatinase) (14,22,23).
Synthesis of the MMPs is regulated by cytokines secreted by
the various cell types present in the plaques (24). We recently
showed that TNF-a, a strong proinflammatory cytokine
present in the mast cells of coronary plaques (12), stimulates
the synthesis of MMP-9 by macrophages in vitro (13). The
present findings that the number of TNF-a-containing mast
cells and MMP-9-containing macrophages both increase as the
lesions become more severe strongly suggest that one mechanism by which mast cells render the plaque unstable is by
stimulating local synthesis of MMP-9. As we have found
previously in stable coronary plaques (12), we now found in
unstable plaques that the macrophages also contain TNF-a
(not shown), suggesting the presence of autocrine and paracrine loops in macrophages for the synthesis of MMP-9.
However, the MMPs are synthesized and secreted as inactive
proforms (proMMPs) that can then be converted into active
forms by cleavage at special sites. In vitro studies have shown
that the tryptase and chymase derived from mast cells can
effectively activate proMMPs: tryptase can activate prostromelysin (proMMP-3) (25), and chymase can activate the interstitial procollagenase (proMMP-1) (26). Because MMP-3 can
activate several other types of proMMPs, the mast cell tryptase
secreted by stimulated mast cells could well be among the
agents that trigger the extracellular activation of several
proMMPs in human atherosclerotic plaques. MMP activity has
been measured in coronary atherectomy samples by using
zymography (27). Interestingly, the greatest activity resided in
the 92-kD band, revealing the presence of active MMP-9 in the
samples.
Unique proinflammatory properties of mast cells. The
number of macrophages did exceed by far the number of mast
cells in the plaques. However, the mast cells are a completely
different type of inflammatory cells and they possess unique
proinflammatory properties (28). Regarding matrix degradation in the plaque, the best example is probably the activation
of the MMPs by mast cell-derived tryptase or chymase which is
plasmin-independent. In other situations the presence of plasmin or expression of the membrane-type MMPs appears to be
obligatory for MMP activation (29). The unique molecular
aspect of mast cell-dependent MMP activation is that the two
MMP-activating mast cell neutral proteases, tryptase and
chymase, are fully active upon secretion from their parent mast
cells. Moreover, they both have activity against the various
components of the extracellular matrix and can initiate matrix
degradation directly. Thus, both tryptase and chymase have
been shown to degrade pericellular matrices (fibronectin)
(30,31).
Coronary atherectomy specimens provide a unique source
of plaque tissues because they make it possible to correlate
features of plaque biology with the clinical status of the patient.
However, only part of the entire plaque is excised and, thus, in
studies based on examination of these specimens, sampling
bias has to be considered. Despite these limitations, we
propose that mast cells may initiate matrix degradation by
multiple mechanisms and therefore, actively participate in local
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
611
weakening of unstable coronary lesions. Thus, a new possibility
emerges for prevention of the progression of coronary plaques
to unstable lesions: inhibition of mast cell degranulation.
References
1. Fuster V, Badimon L, Badimon JJ, Chesebro JH. The pathogenesis of
coronary artery disease and the acute coronary syndromes. N Engl J Med
1992;326:242–50.
2. Falk E. Why do plaques rupture? Circulation 1992;86 Suppl III:30 – 42.
3. Moreno PR, Falk E, Palacios JF, Newell JB, Fuster V, Fallon JT. Macrophage infiltration in acute coronary syndromes. Implications for plaque
rupture. Circulation 1994;90:775– 8.
4. 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.
5. van der Wal AC, Becker AE, Koch KT, et al. Clinically stable angina pectoris
is not necessarily associated with histologically stable atherosclerotic
plaques. Heart 1996;76:312– 6.
6. Kovanen PT, Kaartinen M, Paavonen T. Infiltrates of activated mast cells at
the site of coronary atheromatous erosion or rupture in myocardial infarction. Circulation 1995;92:1084 – 8.
7. Austen KF. The heterogeneity of mast cell populations and products. Hosp
Pract 1984;19:135– 46.
8. Irani AA, Schechter NM, Craig SS, DeBlois G, Schwartz LB. Two types of
human mast cells that have distinct neutral protease compositions. Proc Natl
Acad Sci USA 1986;83:4464 – 8.
9. Hibbs MS, Hoidal JR, Kang AH. Expression of a metalloproteinase that
degrades native type V collagen and denatured collagens by cultured human
alveolar macrophages. J Clin Invest 1987;80:1644 –50.
10. Wilhelm SM, Collier IE, Marmer BL, Eisen AZ, Grant GA, Goldberg GI.
SV-40-transformed human lung fibroblasts secrete a 92kDa type IV collagenase which is identical to that secreted by normal human macrophages.
J Biol Chem 1989;264:17213–21.
11. Kaartinen M, Penttilä A, Kovanen PT. Accumulation of activated mast cells
in the shoulder region of human coronary atheroma, the predilection site of
atheromatous rupture. Circulation 1994;90:1669 –78.
12. Kaartinen M, Penttilä A, Kovanen PT. Mast cells in rupture-prone areas of
human coronary atheromas produce and store TNF-a. Circulation 1996;94:
2787–92.
13. Saren P, Welgus HG, Kovanen PT. TNF-a and IL-1b selectively induce
expression of 92-kDa gelatinase by human macrophages. J Immunol 1996;
157:4159 – 65.
14. Brown DL, Hibbs MS, Kearney M, Loushin C, Isner JM. Identification of
92-kD gelatinase in human coronary atherosclerotic lesions: association of
active enzyme synthesis with unstable angina. Circulation 1995;91:2125–31.
15. Irani A-M, Bradford TR, Kepley CL, Schechter NM, Schwartz LB. Detection of MCT and MCTC types of human mast cells by immunohistochemistry
using new monoclonal anti-tryptase and anti-chymase antibodies. J Histochem Cytochem 1989;37:1509 –15.
16. McCullagh P, Nelder JA. Generalized Linear Models. 2nd ed. London:
Chapman & Hall, 1989:98.
17. Ishizaka T, Ishizaka K. Activation of mast cells for mediator release through
IgE receptors. Prog Allergy 1984;34:188 –235.
18. Criqui MH, Lee ER, Hamburger RN, Klauber MR, Coughlin SS. IgE and
cardiovascular disease: results from a population-based study. Am J Med
1987;82:964 – 8.
19. Langer RD, Criqui MH, Feigelson HS, McCann TJ, Hamburger RN. IgE
predicts future nonfatal myocardial infarction in men. J Clin Epidemiol
1996;49:203–9.
20. Sedgwick JD, Holt PG, Turner KJ. Production of a histamine-releasing
lymphokine by antigen- or mitogen-stimulated human peripheral T cells.
Clin Exp Immunol 1981;45:409 –18.
21. Liu MC, Proud D, Lichtenstein LM, et al. Human lung macrophage-derived
histamine-releasing activity is due to IgE-dependent factors. J Immunol
1986;136:2588 –95.
22. Henney AM, Wakeley PR, Davies MJ, et al. Localization of stromelysin gene
expression in atherosclerotic plaques by in situ hybridization. Proc Natl Acad
Sci USA 1991;88:8154 – 8.
612
KAARTINEN ET AL.
MAST CELLS IN ACUTE CORONARY SYNDROMES
23. Galis ZS, Sukhova GK, Lark MW, Libby P. Increased expression of matrix
metalloproteinases and matrix degrading activity in vulnerable regions of
human atherosclerotic plaques. J Clin Invest 1994;94:2493–503.
24. Libby P. Molecular bases of the acute coronary syndromes. Circulation
1995;91:2844 –50.
25. Gruber BL, Marchese MJ, Suzuki K, et al. Synovial procollagenase activation by human mast cell tryptase. Dependence upon matrix metalloproteinase 3 activation. J Clin Invest 1989;84:1657– 62.
26. Saarinen J, Kalkkinen N, Welgus HG, Kovanen PT. Activation of human
interstitial procollagenase through direct cleavage of the Leu83-Thr84 bond
by mast cell chymase. J Biol Chem 1994;269:18134 – 40.
27. Tyagi SC, Meyer L, Schmaltz RA, Reddy HK, Voelker DJ. Proteinases and
JACC Vol. 32, No. 3
September 1998:606 –12
28.
29.
30.
31.
restenosis in the human coronary artery: extracellular matrix production
exceeds the expression of proteolytic activity. Atherosclerosis 1995;116:43–
57.
Galli SJ. New concepts about the mast cell. N Engl J Med 1993;328:257– 65.
Dollery CM, McEwan JR, Henney AM. Matrix metalloproteinases and
cardiovascular disease. Circulation 1995;77:863– 8.
Lohi J, Harvima I, Keski-Oja J. Pericellular substrates of human mast cell
tryptase: 72000 dalton gelatinase and fibronectin. J Cell Biochem 1992;50:
337– 49.
Vartio T, Seppä H, Vaheri A. Susceptibility of soluble and matrix fibronectins to degradation by tissue proteinases, mast cell chymase and cathepsin G.
J Biol Chem 1981;256:471–7.