© 1999 American Heart Association, Inc.
Atherosclerosis and Lipoproteins |
Complete Processing of Type III Collagen in Atherosclerotic Plaques
From the Departments of Clinical Chemistry (M.K.B., L.R., J.R.) and Surgery (M.M., J.S., T.J), University of Oulu, Oulu, Finland.
Correspondence to Professor Juha Risteli, Department of Clinical Chemistry, University of Oulu, FIN-90220 Oulu, Finland. E-mail juha.risteli{at}oulu.fi
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Abstract—The extent of processing of type III collagen is assessed, and the proportions of type I and III collagens are estimated in atherosclerotic plaques obtained from the carotid artery, common femoral artery, and aorta. The fraction of type III collagen that had retained its amino-terminal propeptide (pN-collagen) was 42% in the soluble extract but only 0.0081% in the insoluble residue. Taken together, only 0.011% of the type III collagen in whole plaques was in the form of type III pN-collagen. Together with the small amounts of the free propeptides of type I procollagen, this finding indicates a low rate of collagen turnover. The amounts of solubilized telopeptides of type I and III collagens were measured, after heat denaturation and trypsin digestion of the collagenous helix, by specific immunoassays for the corresponding trypsin-generated antigens. The mean proportion of type III collagen was 61% (95% confidence interval, 58% to 65%) in the carotid and femoral artery plaques and 56% (95% confidence interval, 44% to 68%) in the aortic specimens. The completely processed and cross-linked type III collagen seems to be the major collagen type in atherosclerotic plaques.
Key Words: atherosclerosis • plaque • collagen • extracellular matrix
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
According to the response-to-injury hypothesis, atherosclerosis is an excessive inflammatory-fibroproliferative response to various forms of insult to the artery wall. It results from focal intimal thickening subsequent to endothelial cell injury and uncontrolled proliferation of smooth muscle cells (SMCs), accompanied by the participation of inflammatory cells and the accumulation of extracellular components (for reviews, see References 1 and 21 2 ). The extracellular matrix participates in virtually all aspects of the atherogenic process. The organic matrix of a plaque consists mainly of collagen types I and III, but controversy exists over their contents and changes in their proportions between the healthy and atherosclerotic aorta.3 4 5 6 7 8 9 10
A currently unknown proportion of type III collagen still carries the amino-terminal propeptide domain of its precursor, type III procollagen.11 Regarding atherosclerotic manifestations, we have previously demonstrated increased serum levels of this propeptide, PIIINP, after both streptokinase and tissue plasminogen activator treatments after acute myocardial infarction12 13 and detected increased serum levels of PIIINP in patients with expanding abdominal aortic aneurysms. Interestingly, the gradient in the PIIINP concentration over the aneurysm sac was significant.14 These results suggest active collagen metabolism in the vessel walls in these clinical situations.
The aim here was to assess the proportions and processing of the type I and III collagens present in advanced human atherosclerotic plaques. We used a combination of immunoassays specific for the various domains of type I and III collagens and procollagens and developed a novel method for examining insoluble collagens. Particular attention was paid to the apparent rate of collagen synthesis and to the proportion of partially processed procollagen molecules with the PIIINP part still attached (type III pN-collagen) that can be found on the surface of type III collagen fibers.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Tissue Samples
Endarterectomy plaques from the carotid artery (n=15) and the common femoral artery (n=2) and atherosclerotic plaques from the abdominal aorta (n=8) were obtained from patients undergoing vascular procedures at the Department of Surgery, Oulu University Hospital. The carotid and femoral specimens were from 12 men and 5 women (mean age, 66.4 years) and the aortic ones from 5 men and 3 women (mean age, 72.9 years). To validate the methods applied, we obtained a piece of healthy aorta from a 29-year-old male cadaver under examination at the Department of Pathology, University of Oulu. The uterine leiomyoma and human placenta were obtained from the Department of Obstetrics and Gynecology, Oulu University Hospital. All of the samples were frozen and stored at -20°C until processed. The collection of human tissue samples was approved by the ethics committee of the Faculty of Medicine, University of Oulu.
Immunoassays for Type III Collagen
The amino-terminal propeptide of human type III collagen,
PIIINP, was measured in soluble extracts and trypsin digests of
insoluble tissue residue by radioimmunoassay (Orion
Diagnostica), as described previously,15 using
sequential saturation. The samples were diluted 1:1 to 1:20 before
analysis.
The cross-linked amino-terminal telopeptide of type III collagen,
IIINTP, was analyzed by a novel in-house
radioimmunoassay.16 The IIINTP antigen was purified from
trypsin-digested human uterine leiomyoma by gel exclusion
chromatography and reverse-phase
chromatography on a high-performance liquid
chromatography system. The final product was
sequenced and its size and purity determined by
SDS–polyacrylamide gel electrophoresis (PAGE). The purified
antigen was used to raise polyclonal antibodies in rabbits. The
dilution of the antiserum used in the assay was 1:400, and the binding
of the radiolabeled (125I) antigen was 53%.
Aliquots (100 µL) of a properly diluted sample were incubated with
200 µL of the antiserum dilution and 200 µL of
125I-IIINTP solution for 2 hours at 37°C. Then
0.5 mL of the second antibody in 10% PEG (molecular weight, 6000) was
added, and the tubes were incubated at 4°C for 30 minutes. The
samples were centrifuged at 2000g for 30 minutes at
4°C, and the radioactivity in the precipitates was counted. Before
analysis, the samples were diluted from 1:5 to 1:1000. In
addition, an immunoassay for the synthetic peptide SP6, having the
sequence DVKSGVAVGGLAG (from Neosystem Laboratories, Strasbourg,
France) from the amino-terminal telopeptide of the 
1-chain of type
III collagen, was used to show that practically no immaturely
cross-linked telopeptides were present in the tissue digests (see
below).
Immunoassays for Type I Collagen
The metabolites of type I collagen were measured using
commercially available immunoassays for the PINP, PICP, and ICTP
antigens (Orion Diagnostica) as described
previously.17 18 19 PINP, the amino-terminal propeptide of
type I collagen, was measured in undiluted samples of the soluble
extracts, and PICP, the carboxy-terminal propeptide of type I collagen,
was measured by using dilutions of 1:5 to 1:10. The concentrations of
ICTP, the carboxy-terminal telopeptide of type I collagen, were
analyzed in trypsin digests by using dilutions varying from
1:100 to 1:4000. In addition, an immunoassay for the synthetic peptide
SP4, having the sequence SAGFDFSFLPQPPQEKY (Neosystem) derived from the
carboxy-terminal telopeptide of the 1-chain of type I collagen, was
analyzed to show that very few immaturely cross-linked
telopeptides were present in the tissue digests (see below).
Tissue Preparation
The atherosclerotic plaques (weight, 0.39 to 3.5 g) and
sclerotic aortic specimens (0.004 to 34.1 g) were cut into small
pieces, and PBS–Tween 20 was added (1 mL/100 mg of wet tissue weight).
A piece of healthy human aorta (weight, 21 g) was treated
similarly. The samples were homogenized with an
Ultra-Turrax homogenizer and centrifuged at
10 000g for 30 minutes. The supernatants were collected for
gel filtration and for the PINP, PICP, and PIIINP analyses.
Trypsin Treatment
The insoluble pellets were treated with
NaBH4 (50 mg/g tissue weight) to stabilize the
possibly reducible cross-links. Fats were removed by brief washes with
acetone/methanol (1:2, vol/vol) and finally with ethanol, followed by
centrifugation and collection of the pellet. The
insoluble pellets were freeze-dried, weighed, suspended in 0.2 mol/L
NH4HCO3 (1 mL/10 mg dry
weight), denatured at 70°C for 1 hour, and treated with 1 mg of
trypsin per 100 mg of sample. The digestions were performed for 4 hours
at 37°C, after which the samples were re-denatured,
homogenized, and re-treated overnight with the same amount
of trypsin. The residual trypsin activity was destroyed at 70°C, and
the samples were centrifuged at 10 000g for 30
minutes. The supernatants were used for the ICTP, IIINTP, and PIIINP
analyses.
Preparation of the Calcified Matrix
After the first 2 enzyme digestions, the insoluble pellets were
briefly washed with 8 mol/L urea to remove small, colored residues of
trypsin-resistant materials, and demineralization was carried
out by extraction with 0.5 mol/L EDTA, pH 7.6, twice for 2 days at
4°C. The residue was then washed twice with water and once with 0.2
mol/L NH4HCO3 before
freeze-drying. The pellet was weighed, and trypsin digestion was
performed as described above. The digests were then centrifuged
at 10 000g for 30 minutes, and the supernatants were
collected and used for ICTP, IIINTP, and PIIINP analyses.
Gel Exclusion Chromatography
Several plaque samples were analyzed further by gel
exclusion chromatography to determine the size and
cross-link maturity of the type I and III collagen propeptides and
telopeptides.
The supernatants of the homogenates were analyzed on a Sephacryl S-300 column equilibrated in PBS–Tween 20 at a flow rate of 6 mL/h and collecting 2.0-mL fractions. The concentrations of PINP and PICP were analyzed in undiluted fractions and that of the PIIINP, in 1:10 dilution. Absorbances were measured at 280 nm.
Trypsin-digested samples (both noncalcified and calcified) were analyzed on a Sephacryl S-100 column equilibrated in 0.2 mol/L NH4HCO3, and the concentrations of IIINTP, ICTP, and PIIINP were measured. The dilutions used varied from 1:1 to 1:20 for IIINTP and from 1:5 to 1:100 for ICTP, the analysis for PIIINP being carried out in undiluted fractions.
SDS–Polyacrylamide Gel Electrophoresis
The effect of trypsin digestion on the size of the PIIINP
antigen was analyzed by SDS-PAGE in 18% gels under reduced
conditions. SDS-PAGE was also used for comparing the sizes of the ICTP
and IIINTP antigens purified from the plaques with the corresponding
trypsin-derived antigens from human leiomyoma and bone.
Statistical Analyses
The values are expressed as means (with 95% CIs). The
statistical analyses were carried out using the SPSS
statistical tool and CI analysis. Spearman's rank correlation
was used for correlation analysis.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Validation of the Tissue Solubilization Procedure
Before analysis of the clinical samples, the effectiveness of heat denaturation and trypsin digestion for solubilizing the IIINTP and ICTP antigens from the atherosclerotic plaque was tested (Figure 1
). Trypsin digestion effectively
released the antigens from the insoluble matrix within 1 hour, and
further digestion did not affect the yield.
|
-
Purification of IIINTP and ICTP Antigens From the Plaque
Cross-linked IIINTP was partially purified from 120 mg of
trypsin-digested, insoluble plaque matrix in the same way as for the
standard IIINTP antigen from uterine leiomyoma (see above). The size of
the isolated plaque telopeptide was compared with that of the leiomyoma
IIINTP on SDS-PAGE (Figure 2A).
Cross-linked ICTP was also partially purified from the insoluble plaque
matrix as described previously,19 and its size was
compared with that of bone ICTP on SDS-PAGE (Figure 2B). Both of
these cross-linked telopeptides were found to be similar to those of
the standard antigens isolated from the reference tissues (Figure 2). Also, their elution positions in gel filtration
chromatography corresponded to those of the standards
(see Figure 5). The inhibition curves obtained in the
immunoassays were also parallel, indicating complete cross reaction
(not shown).
|
|
Effect of Trypsin Digestion on the Antigenicity of Purified
PIIINP
PIIINP was purified from human ascitic fluid as described
earlier.15 Enzyme digestion was performed in the same way
as for the atherosclerotic samples (propeptide: enzyme=1:50 wt/wt), and
its effects on the apparent size of the antigen on SDS-PAGE and on the
antigenicity in the immunoassay were studied. There was partial
cleavage of the propeptide (Figure 3),
which led to a 50% decrease in its immunoreactivity (Figure 4). Consequently, the PIIINP
concentration observed in the trypsin digests was multiplied by 2 when
calculating the amount of type III pN-collagen in the tissue
samples.
|
2:1). Standards are as in Figure 2
|
Insoluble Collagens in Atherosclerotic Specimens
The soluble extracts of the atherosclerotic tissues contained
<0.1% of the total amounts of the cross-linked telopeptides of type I
and III collagens, ICTP and IIINTP, respectively. Thus, up to 99.9% of
the type I and III collagens in these tissues is rendered insoluble via
cross-linking.
The mean proportion of type III collagen (calculated as a percentage of
the sum of types I and III) was 61% in the
endarterectomy plaques and 56% in the
atherosclerotic aortic specimens (Table 1). The 1 healthy young aorta contained
only slightly more type III collagen (72%) than did the rest of the
samples. There was a significant correlation between the total amounts
of solubilized ICTP and IIINTP antigens (r=0.92;
P<0.01; 95% CI, 0.82 to 0.96). For comparison, in human
leiomyoma and placenta, the proportion of type III collagen was 35%
and 33%, respectively.
|
As expected, the proportion of the calcified extracellular matrix varied greatly between the samples (eg, 1% to 60% of IIINTP was found to be calcified). Bearing this large variation in mind, the mean value of IIINTP and ICTP found in the calcified matrix was 18% of the total amount of those cross-linked antigens. Surprisingly, the proportion of type III collagen was practically the same in both the calcified and the noncalcified matrix, being 54% in the calcified fraction. The large variation between the samples is most probably due to different extents of calcification, which affects the weights of the samples but not the proportions of the 2 collagen types. As expected, the healthy aorta did not show any visible calcification.
Sizes of the Cross-Linked Telopeptide Antigens
The IIINTP and ICTP antigens in the atherosclerotic plaques
corresponded in size to the trivalent, fully cross-linked peptide
standards (Figure 5
). The ICTP antigen
eluted in 1 peak (fractions 47 to 55), and there were no smaller
antigenic forms. This was true both for the calcified and noncalcified
phases of the samples. The IIINTP antigen was also eluted in 1 major
peak, corresponding to a trivalent, fully cross-linked peptide standard
(fractions 37 to 47), but there were also minor amounts of possible
divalently cross-linked and non–cross-linked forms (fractions 48 to
69).
Amounts and Sizes of Procollagen Propeptides in the
Atherosclerotic Specimens
The propeptides of type I procollagen, PINP and PICP, and that of
type III procollagen, PIIINP, were measured in extracts that contained
soluble, mostly non–cross-linked collagens. In addition, PIIINP was
measured in the trypsin digests of both the insoluble matrixes.
The concentrations of PINP and PICP in the soluble extract were very
low (PINP, 0.13 µg/g wet weight; SD, 0.06 µg/g; PICP, 1.18 µg/g;
SD, 0.46 µg/g), indicating a very low rate of type I procollagen
synthesis in the plaques. Although the concentration of PINP
antigenicity in the fractions was almost too low to be analyzed
by gel filtration, only authentically cleaved PINP antigen was found to
be present (Figure 6A). In the case
of PICP, almost equal amounts of the intact carboxy-terminal propeptide
and the type I pC-collagen were seen (Figure 6B).
|
Approximately 35% of the PIIINP antigen was found in the soluble
extract and 65% in the insoluble matrix. Gel filtration
analysis indicated that the PIIINP antigen in the soluble
fraction was almost always in the form of type III pN-collagen (Figure 6C), so that the pN-collagen accounted for 42% of the total
type III collagen in the extract (Table 2). In the insoluble matrix, however,
only 0.0081% of the type III collagen was in the form of pN-collagen.
Thus, the overall proportion of type III pN-collagen in the plaques was
only 0.011% (Table 2). For comparison, in the insoluble matrix
of human leiomyoma and placenta, the proportion of type III pN-collagen
was 1.4% and 8.5%, respectively.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Collagens are important for atherogenesis because they represent the major extracellular component in the plaque and thereby contribute to the occlusive nature of the disease. They also play a significant role in hemostasis and thrombosis by inducing the aggregation of blood platelets.20 Furthermore, collagens can influence the proliferation and state of differentiation of SMCs in vitro.21 Several collagen types are known to bind oxidized lipoproteins, and thus accumulation of collagen in the intima may promote lipoprotein accumulation.22 At least 6 collagen types (I, III, IV, V, VI, and VIII) are present in blood vessels,23 and a predominance of interstitial collagen types I and III has been documented in atherosclerotic lesions, where they appear to be codistributed in different amounts within all 3 layers of the artery wall.10 24
Notwithstanding the considerable advances made in the area relating to arterial collagens of normal and atherosclerotic tissues, the available information remains incomplete and, above all, inconsistent and controversial.20 25 26 The initial work on the status of interstitial collagens3 suggested that there is a shift in favor of type I collagen in fibrous atherosclerotic lesions compared with the normal arterial wall, where type III collagen predominates. Later results have suggested, however, that type I, not type III, collagen is always the major species, accounting for 55% to 88% of the total content of the 2.4 5 6 7 8 9 10 One reason for the discrepancies could be analytical problems related to the highly cross-linked state of the vessel wall collagens, which hampers methods in which solubilized materials are quantified. The initial result, a large amount of type III collagen in the healthy aorta,3 was later criticized in light of the assumption that pepsin solubilizes type III collagen from the vessel wall more easily than it does type I.27 CNBr digestion of the insoluble matrix suggested that larger amounts of type I collagen than of type III were found, but the CNBr method is also subject to similar errors, since the cleavage of collagen chains can be prevented by methionine oxidation. In addition, the CNBr method is based on simple staining of the cleaved peptides, a procedure that is known to be not optimal for the collagenous sequences.
We used a novel method of type I and III collagen analysis that
partially overcomes the problem of insolubility due to cross-linking.
It has previously been shown that 99% of type I collagen can be
solubilized when the highly insoluble collagenous matrix of dentin is
repeatedly heat denatured and digested with trypsin.28
This solubilization method also works with soft tissues (Figure 1), because trypsin effectively cleaves all denatured collagens
specifically, after the basic amino acids lysine and arginine. The
telopeptide domains containing the cross-links are liberated in a
cross-linked state, and their concentrations can be determined by
specific immunoassays developed for the trypsin-generated antigens. In
addition to trypsin, several other enzymes such as bacterial
collagenase, chymotrypsin, and pepsin cleave denatured
collagens. Pepsin and chymotrypsin,29 however, destroy the
immunoreaction in the ICTP assay, and they also affect IIINTP
antigenicity. Compared with bacterial collagenase, trypsin
is more specific, more potent, and more cost-effective. The validity of
the telopeptide approach, however, should also be tested for each
tissue studied, because the ICTP assay especially19
measures only trivalently cross-linked forms of type I collagen. Thus,
the content of type I collagen in human skin, which contains mainly
histidine-derived cross-links,30 cannot be reliably
estimated with this method.
The type I collagen in atherosclerotic plaques was found to be fully
cross-linked, since a synthetic peptide (SP4) assay detecting all of
the various cross-linked and non–cross-linked forms gave a similar
elution profile in gel filtration as did the ICTP assay (Figures 2B and 5). Likewise, there was no evidence in the case of
type III collagen to indicate that the size, chain composition, or
cross-linking was in any way different from that in the trivalently
cross-linked IIINTP used as the standard (Figures 2A and 5). Thus, the present results support those obtained
earlier, indicating that type III collagen is at least as abundant as
type I collagen in aortic walls. This is not surprising, because
genetic defects in type III collagen are often expressed in the vessel
walls,31 where the tissue is exposed to large changes in
intraluminal pressure.
In this study, we divided the tissue into 3 fractions: a soluble tissue extract and noncalcified and calcified insoluble matrixes. The noncalcified and calcified fractions were studied separately to obtain information on the possible effect of the calcification process on collagen. Interestingly, there were no differences between these fractions with respect to the proportions of type I and type III collagens. Calcification in the vessel wall is inhibited by the matrix Gla protein,32 and this seems to be a totally different process from the mineralization of the organic matrix of bones, where practically only type I collagen is normally present. The fully matured state of the cross-links in type I collagen of the vessel wall also differs from the situation in mineralized bone collagen.30
Partially processed type III procollagen molecules with a retained
amino-terminal propeptide (ie, type III pN-collagen) are found in most
tissues on the surface of type III collagen fibers by
immunohistochemical analyses. Here, 1/3 of such type III
pN-collagen molecules could be easily extracted from the
atherosclerotic plaques, indicating that these molecules did not yet
participate in intermolecular cross-linking, which is essential for the
tensile strength of the tissue. The rest of the type III pN-collagen
was found in the insoluble matrix, but the total amount of type III
pN-collagen in type III collagen was still negligible (Table 2).
The estimation of the amount of PIIINP in the insoluble matrix was
based on the surprising finding that a definite part of its
immunoreactivity is retained after heat denaturation and trypsin
digestion (Figure 4). The PIIINP propeptide is stabilized by 3
interchain and 5 intrachain disulfide bridges. Consequently, the
melting temperature of the collagenous domain is as high as 53°C, and
refolding of the helix from the denatured peptide takes place extremely
fast, as the chains are held together by the disulfide
bonds.33 Our results suggest that only 1 of the 3 chains
of the PIIINP molecule is susceptible to trypsin (Figure 3),
although all 3 chains have 3 arginine and 2 lysine residues, which are
potential trypsin digestion sites. The reason for this trypsin
resistance is unknown, but there are several possibilities. The rapid
refolding of the helix may protect the sites within the collagenous
domain, because trypsin does not cleave triple-helical collagen;
alternatively, lysines in the collagenous domain can be hydroxylated to
hydroxylysine residues. One arginine is very close to a tyrosine
residue in the amino-terminal part of the propeptide that can be
sulfated to tyrosine-O-sulfate.34 This
highly negative charge may alter the molecule's susceptibility to
trypsin. In any case, there was very much less type III pN-collagen in
the plaques than could be expected. The proportion of type III
pN-collagen was as much as 1000-fold higher in human placenta,
representing fetal tissue. Also, in rapidly growing human
uterine leiomyoma, this proportion was 1.4%.
Previous studies have suggested that fibrinolytic enzymes play a
significant role in the processing and turnover of collagen in the
vessel walls.12 13 On the other hand, thrombin, for
example, stimulates SMC procollagen synthesis,35 which
could indicate that the development of pathological conditions
involving the blood coagulation system would rather lead to increased
connective tissue deposition than to its slower-than-normal
degradation. We could find only relatively small concentrations of free
procollagen propeptides (Figure 6), which are directly related
to ongoing collagen synthesis, and our data thus support the idea of
metabolic inertia.36 These propeptide domains
of interstitial procollagens are removed by specific
endoproteinases (C- and N-proteinases) in the
extracellular space. Above all, the complete processing of type III
collagen in the atherosclerotic plaques is surprising and raises
interesting questions. The thrombogenicity of type III collagen in the
vessel wall must thus be based on fully processed and cross-linked
collagen, and clinical events such as rupture of the plaque must
involve the degradation of such collagen molecules. The turnover and
processing of type III collagen may well be different in several other
pathological situations and also related to their pathogenesis.
|
Acknowledgments |
|---|
The authors gratefully acknowledge the expert technical assistance of Päivi Annala, Ulla Pohjoisaho, and Aimo Heinämäki, PhD.
Received June 9, 1998; accepted November 17, 1998.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Ross R. The pathogenesis of atherosclerosis: a perspective for the 1990s. Nature. 1993;362:801–809.[Medline] [Order article via Infotrieve]
2.
Schwartz SM, deBlois D, O'Brien ERM. The intima: soil
for atherosclerosis and restenosis. Circ
Res. 1995;77:445–465.
3. McCullagh K. Collagen characterisation and cell transformation in human atherosclerosis. Nature. 1975;258:73–75.[Medline] [Order article via Infotrieve]
4. Morton LF, Barnes MJ. Collagen polymorphism in the normal and diseased blood vessel wall: investigation of collagens type I, III and V. Atherosclerosis. 1982;42:41–51.[Medline] [Order article via Infotrieve]
5. Leushner RA, Haust DA. Interstitial collagens in fibrous atherosclerotic lesions of human aorta. Pathol Biol. 1986;34:14–18.[Medline] [Order article via Infotrieve]
6. Hanson AN, Bentley JP. Quantitation of type I to type III collagen ratios in small samples of human tendon, vessels and atherosclerotic plaques. Anal Biochem. 1983;130:32–40.[Medline] [Order article via Infotrieve]
7. Murata K, Motayama T, Kotake C. Collagen types in various layers of human aorta and their changes with atherosclerotic process. Atherosclerosis. 1986;60:251–262.[Medline] [Order article via Infotrieve]
8.
Ooshima A. Collagen B chain: increased
proportion in human atherosclerosis.
Science. 1981;213:666–668.
9. McCullagh KG, Duance VC, Bishop KA. The distribution of collagen types I, III and V (AB) in normal and atherosclerotic human aorta. J Pathol. 1980;130:45–54.[Medline] [Order article via Infotrieve]
10.
Katsuda S, Okada Y, Minamoto T, Oda Y, Matsui Y,
Nakanishi I. Collagens in human atherosclerosis:
immunohistochemical analysis using collagen type-specific
antibodies. Arterioscler Thromb. 1992;12:494–502.
11. Fleischmajer R, Perlish JS, Timpl R. Collagen fibrillogenesis in human skin. Ann N Y Acad Sci. 1985;460:246–257.[Medline] [Order article via Infotrieve]
12.
Peuhkurinen KJ, Risteli L, Melkko J, Linnaluoto M,
Jounela A, Risteli J. Thrombolytic therapy with
streptokinase stimulates collagen breakdown. Circulation. 1991;83:1969–1975.
13. Peuhkurinen K, Risteli L, Jounela A, Risteli J. Changes in interstitial collagen metabolism during acute myocardial infarction treated with streptokinase or tissue plasminogen activator. Am Heart J. 1996;131:7–13.[Medline] [Order article via Infotrieve]
14. Satta J, Juvonen T, Haukipuro K, Juvonen M, Kairaluoma MI. Increased turnover of collagen in aortic aneurysms, demonstrated by measuring the concentrations of type III procollagen in peripheral and aortal blood samples. J Vasc Surg. 1995;22:155–160.[Medline] [Order article via Infotrieve]
15.
Risteli J, Niemi S, Trivedi P, Mäentausta O,
Mowat AP, Risteli L. Rapid equilibrium radioimmunoassay for the
amino-terminal propeptide of human type III procollagen. Clin
Chem. 1988;34:715–718.
16. Kauppila S, Bode MK, Stenbäck F, Risteli L, Risteli J. Cross-linked telopeptides of type I and III collagens in malignant ovarian tumours in vivo. Br J Cancer. In press.
17.
Melkko J, Kauppila S, Risteli L, Niemi S, Haukipuro K,
Jukkola A, Risteli J. Immunoassay for intact amino-terminal
propeptide of human type I procollagen. Clin Chem. 1996;42:947–954.
18.
Melkko J, Niemi S, Risteli L, Risteli J.
Radioimmunoassay of the carboxy-terminal propeptide of human type I
procollagen. Clin Chem. 1990;36:1328–1332.
19.
Risteli J, Elomaa I, Niemi S, Novamo A, Risteli L.
Radioimmunoassay for the pyridinoline cross-linked carboxy-terminal
telopeptide of type I collagen: a new serum marker of bone collagen
degradation. Clin Chem. 1993;39:635–640.
20. Barnes MJ. Collagens in atherosclerosis. Collagen Related Res. 1985;5:65–97.[Medline] [Order article via Infotrieve]
21. Sakata N, Kawamura K, Takebayashi S. Effects of collagen matrix on proliferation and differentiation of vascular smooth muscle cells in vitro. Exp Mol Pathol. 1990;52:179–191.[Medline] [Order article via Infotrieve]
22.
Greilberger J, Schmut O, Jurgens G. In vitro
interactions of oxidatively modified LDL with type I, II, III, IV and V
collagen, laminin, fibronectin, and poly-D-lysine.
Arterioscler Thromb Vasc Biol. 1997;17:2721–2728.
23. Mayne R. Collagenous proteins of blood vessels. Arteriosclerosis. 1986;6:585–593.[Medline] [Order article via Infotrieve]
24. Shekhonin BV, Domogatsky SP, Muzykantov VR, Idelson GL, Rukosuev VS. Distribution of type I, III, IV and V collagen in normal and atherosclerotic human arterial wall: immunomorphological characteristics. Collagen Related Res. 1985;5:335–368.
25. Wagner WD. Modification of collagen and elastin in the human atherosclerotic plaque. In: Glagov S, Neumann WP, Schaffer SA, eds. Pathobiology of the Human Atherosclerotic Plaque. New York, NY: Springer-Verlag; 1990:167–188.
26. Rauterberg J, Jaeger E, Althaus M. Collagens in atherosclerotic vessel wall lesions. In: Vollmer E, Roessner A, eds. Current Topics in Pathology. Berlin, Germany: Springer-Verlag; 1993:163–192.
27. Szymanovicz AG, Bellon G, Laurain-Guillaume G, Delvincourt, T, Randoux A, Caulet T, Borel JP. An evaluation by sequential extraction of the proportions of collagen types from medium sized arteries. Artery. 1982;10:250–265.[Medline] [Order article via Infotrieve]
28. Kuboki Y, Tsuzaki M, Sasaki S, Liu CF, Mechanic GL. Location of the intermolecular cross-links in bovine dentin collagen, solubilization with trypsin and isolation of cross-link peptides containing dihydroxylysinorleucine and pyridinoline. Biochem Biophys Res Commun. 1981;102:119–126.[Medline] [Order article via Infotrieve]
29. Risteli J, Sassi ML, Eriksen H, Niemi S, Mansell JP, Risteli L. The assay for the carboxy-terminal telopeptide of human type I collagen (ICTP). [Abstract] J Bone Miner Res. 1997;12(suppl 1):498.
30. Eyre DR, Paz MA, Gallop PM. Cross-linking in collagen and elastin. Annu Rev Biochem. 1984;53:717–748.[Medline] [Order article via Infotrieve]
31.
Liu X, Wu H, Byrne M, Krane S, Jaenisch R. Type III
collagen is crucial for collagen I fibrillogenesis and for normal
cardiovascular development. Proc Natl Acad Sci
U S A. 1997;94:1852–1856.
32. Luo G, Ducy P, McKee MD, Pinero GJ, Loyer E, Behringer RR, Karsenty G. Spontaneous calcification of arteries and cartilage in mice lacking matrix Gla protein. Nature. 1997;386:78–81.[Medline] [Order article via Infotrieve]
33. Bruckner P, Bächinger HP, Timpl R, Engel J. Three conformationally distinct domains in the amino-terminal segment of type III procollagen and its rapid triple helix coil transition. Eur J Biochem. 1978;90:595–603.[Medline] [Order article via Infotrieve]
34. Jukkola A, Risteli J, Niemelä O, Risteli L. Incorporation of sulphate into type III procollagen by cultured human fibroblasts: identification of tyrosine O-sulphate. Eur J Biochem. 1986;154:219–224.[Medline] [Order article via Infotrieve]
35. Dabbagh K, Laurent GJ, McAnulty RJ, Chambers RC. Thrombin stimulates smooth muscle cell procollagen synthesis and mRNA levels via a PAR-1 mediated mechanism. Thromb Haemost. 1998;79:405–409.[Medline] [Order article via Infotrieve]
36.
Kockx MM, De Meyer GR, Buyssens N, Knaapen MW, Bult H,
Herman AG. Cell composition, replication, and apoptosis in
atherosclerotic plaques after 6 months of cholesterol
withdrawal. Circ Res. 1998;83:378–387.
This article has been cited by other articles:
 |
|
 |
|
  S. Nurmenniemi, T. Sinikumpu, I. Alahuhta, S. Salo, M. Sutinen, M. Santala, J. Risteli, P. Nyberg, and T. Salo A Novel Organotypic Model Mimics the Tumor Microenvironment Am. J. Pathol., September 1, 2009; 175(3): 1281 - 1291. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Rodriguez, J. Martinez-Gonzalez, B. Raposo, J. F. Alcudia, A. Guadall, and L. Badimon Regulation of lysyl oxidase in vascular cells: lysyl oxidase as a new player in cardiovascular diseases Cardiovasc Res, July 1, 2008; 79(1): 7 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Goncalves, J. Moses, N. Dias, L. M. Pedro, J. Fernandes e Fernandes, J. Nilsson, and M. P.S. Ares Changes Related to Age and Cerebrovascular Symptoms in the Extracellular Matrix of Human Carotid Plaques Stroke, March 1, 2003; 34(3): 616 - 622. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||