Collagen types in various layers of the human aorta and their changes with the atherosclerotic process

Acute decrease of cardio-ankle vascular index with the administration of beraprost sodium

AIM

A novel arterial stiffness index, the cardio-ankle vascular index (CAVI), has been proposed. To clarify the properties of CAVI, the effects of beraprost sodium (BPS), a prostaglandin (PG) I2 analogue, which has a potent vasodilating effect, on CAVI were studied and comparing with brachialankle pulse wave velocity (baPWV) in healthy volunteers.

METHODS

Male volunteers (n=18, 46.3±4.2 yr) were enrolled in this study and administered BPS (40 µg). CAVI and baPWV were measured every hour for 4 hours.

RESULTS

When BPS was administered to 18 healthy volunteers, systolic blood pressure and diastolic blood pressure fluctuated slightly, but the means did not change. CAVI significantly decreased in the 1st hour from 8.3±0.34 (mean±SE) to 7.9±0.34 (p<0.05) and this decrease persisted for 3 hours, whereas baPWV did not significantly change. ΔbaPWV each time was significantly correlated with both Δsystolic blood pressure and Δdiastolic blood pressure, but ΔCAVI did not correlate with either Δsystolic blood pressure (r=-0.12, p=0.38) or Δdiastolc blood pressure (r=-0.22, p=0.10).

CONCLUSIONS

Beraprost sodium did not decrease blood pressure, but decreased CAVI, whereas baPWV did not change. These results indicate that CAVI partly reflected the contraction of arterial smooth muscle cells.

Transient mesenteric ischemia leads to remodeling of rat mesenteric resistance arteries

Mesenteric ischemia/reperfusion (I/R) is associated with high rates of morbidity and mortality. We studied the effect of mesenteric I/R on structural and mechanical properties of rat mesenteric resistance artery (MRA) that, once disrupted, might impact the outcome of this devastating clinical condition. Superior mesenteric artery from Wistar–Kyoto rats was occluded (90 min) and reperfused (24 h). The effect of tezosentan, a dual endothelin (ET)-receptor antagonist, was studied in ischemic (IO) and sham-operated (SO) animals. MRA structure and mechanics were assessed by pressure myography. Nuclei distribution, elastin content and organization, collagen I/III and ET-1 expression, ET-1 plasma levels, superoxide anion (O2⋅−) production, and mRNA levels of NAD(P)H-oxidase subunits were measured. To assess ET-1 effects on O2⋅− production, MRA from non-operated rats were incubated in culture medium with ET-1. Mesenteric I/R increased MRA wall thickness (P < 0.05) and cross-sectional area (P < 0.05) but decreased wall stiffness (P < 0.05). Arterial remodeling was paralleled by enhancement of: (i) collagen I/III expression (P < 0.01), ET-1 expression (P < 0.05), and O2⋅− formation (P < 0.01) in the vessel wall; (ii) number of internal elastic lamina (IEL) fenestrae (P < 0.05); and (iii) plasma levels of ET-1 (P < 0.05). Moreover, ET-1 increased O2⋅− (P < 0.05) production in cultured MRA. Tezosentan prevented hypertrophic remodeling and collagen I/III deposition, and enhanced O2⋅− production, but it did not affect the decreased wall stiffness after mesenteric I/R. These results indicate that 90 min occlusion/24 h reperfusion induces hypertrophic remodeling of MRA linked to ET-1-mediated increase of collagen and O2⋅−. Decreased stiffness may be associated with increased number of IEL fenestrae. The resulting MRA remodeling, initially adaptive, might become maladaptive contributing to the pathology and poor outcome of mesenteric I/R, and might be a valuable treatment target for mesenteric I/R.

The interaction of plasma sialylated and desialylated lipoproteins with collagen from the intima and media of uninvolved and atherosclerotic human aorta

We have evaluated the binding of sialylated and desialylated lipoproteins to collagen isolated from the proteoglycan and musculoelastic layers of intima and media of uninvolved human aorta and atherosclerotic lesions. Comparing various collagen preparations from the uninvolved intima-media, the binding of sialylated apoB-containing lipoproteins was best to collagen from the intimal PG-rich layer. Binding of sialylated apoB-containing lipoproteins to collagen from this layer of fatty streak and fibroatheroma was 1.4- and 3.1-fold lower, respectively, in comparison with normal intima. Desialylated VLDL versus sialylated one exhibited a greater binding (1.4- to 3.0-fold) to all the collagen preparations examined. Desialylated IDL and LDL showed a higher binding than sialylated ones when collagen from the intimal layers of fibroatheroma was used. Binding of desialylated HDL to collagen from the intimal PG-rich layer of normal tissue, initial lesion, and fatty streak was 1.2- to 2.0-fold higher compared with sialylated HDL.

Middle cerebral artery alterations in a rat chronic hypoperfusion model

Chronic cerebral hypoperfusion (CHP) induces microvascular changes that could contribute to the progression of vascular cognitive impairment and dementia in the aging brain. This study aimed to analyze the effects of CHP on structural, mechanical, and myogenic properties of the middle cerebral artery (MCA) after bilateral common carotid artery occlusion (BCCAO) in adult male Wistar rats. Sham animals underwent a similar surgical procedure without carotid artery (CA) ligation. After 15 days of occlusion, MCA and CA were dissected and MCA structural, mechanical, and myogenic properties were assessed by pressure myography. Collagen I/III expression was determined by immunofluorescence in MCA and CA and by Western blot in CA. mRNA levels for 1A1, 1A2, and 3A1 collagen subunits were quantified by quantitative real-time PCR in CA. Matrix metalloproteinase (MMP-1, MMP-2, MMP-9, and MMP-13) and hypoxia-inducible factor-1α (HIF-1α) protein expression were determined in CA by Western blot. BCCAO diminished cross-sectional area, wall thickness, and wall-to-lumen ratio. Nevertheless, whereas wall stress was increased, stiffness was not modified and myogenic response was diminished. Hypoperfusion triggered HIF-1α expression. Collagen I/III protein expression diminished in MCA and CA after BCCAO, despite increased mRNA levels for 1A1 and 3A1 collagen subunits. Therefore, the reduced collagen expression might be due to proteolytic degradation, since the expression of MMP-1 and MMP-9 increased in the CA. These data suggest that BCCAO induces hypotrophic remodeling by a mechanism that involves a reduction of collagen I/III in association with increased MMP-1 and MMP-9 and that decreases myogenic tone in major arteries supplying the brain.

Inflammation, neovascularization and intra-plaque hemorrhage are associated with increased reparative collagen content: implication for plaque progression in diabetic atherosclerosis

Sustained inflammation may stimulate a reparative process increasing early reparative type III collagen synthesis, promoting atherosclerotic plaque progression. We evaluated inflammation, neovascularization, intra-plaque hemorrhage (IPH), and collagen deposition in human aortic atherosclerotic plaques from patients with and without diabetes mellitus (DM). Plaques were procured at autopsy from lower thoracic and abdominal aorta from DM (n = 20) and non-DM (n = 22) patients. Inflammation and neovascularization were quantified by double-label immunochemistry and the IPH grade was scored using H&E-stained sections. Type I and type III collagens were quantified using Picro-Sirius red stain with polarization microscopy and computerized planimetry. In non-DM plaques, 27%, 40%, and 33% had mild, moderate and severe inflammation in the fibrous cap and shoulder compared with 2%, 30% and 68% in DM plaques (p < 0.001). The geometric mean neovessel count was increased in DM versus non-DM plaques (140 [95% CI: 119-165] versus 59 [95% CI: 51-70]; p < 0.001). The IPH grade was increased in DM verses non-DM plaques (0.82 ± 0.11 versus 0.29 ± 0.11; p < 0.001) (percentage grade). The density of type III was increased in DM plaques (0.16 ± 0.01 versus 0.06 ± 0.01; p < 0.001) with a non-significant reduction in type I density in DM when compared with non-DM (0.28 ± 0.03 versus 0.33 ± 0.03; p = 0.303) (content per mm²). The increase in type III collagen content correlated with total neovessel content (r = 0.58; p < 0.001) in DM plaques. In conclusion, our study suggests that enhanced type III collagen deposition was associated with inflammation, neovascularization and IPH, and may be a contributing factor in DM plaque progression.

Functional Effect of Platelet Membrane Glycoprotein Ia Gene Polymorphism in the Pathogenesis of Unstable Angina Pectoris

The functional effect of platelet membrane glycoprotein Ia ( GPIa) gene 807C/T polymorphism in unstable angina pectoris (UAP) pathogenesis was investigated in Chinese Han individuals. Collagen type I-induced platelet aggregation was measured in 33 healthy subjects. Plasma levels of α-granule membrane protein (GMP-140) were measured in 33 healthy subjects and in 35 patients with recentonset angina at rest within 24 h of hospitalization. Platelet membrane GPIa gene 807C/T polymorphism was determined in all subjects. Lag-time before 30% platelet aggregation was significantly longer in CC genotype than in TC genotype healthy subjects, although there was no significant difference in maximal platelet aggregation between healthy subjects with either genotype. Plasma GMP-140 levels were significantly higher in TC genotype patients compared with CC genotype patients or healthy subjects; a significant difference was also observed between the latter two groups. It was concluded that rapid initiation of collagen-induced platelet aggregation may be associated with the platelet membrane GPIa T807 allele, which may be important in UAP pathogenesis.

Contradictory effects of β1- and α1- aderenergic receptor blockers on cardio-ankle vascular stiffness index (CAVI)--CAVI independent of blood pressure

AIM

The cardio-ankle vascular stiffness index (CAVI) is a new parameter that reflects the stiffness of the aorta, femoral artery and tibial artery as a whole. One of its conspicuous features is that CAVI is independent of blood pressure at measuring time, theoretically. But, it has not been experimentally proved yet. For confirmation, pharmacological studies were performed comparing with brachial-ankle pulse wave velocity (baPWV).

METHODS

Used drugs were a β1-adrenoceptor blocker, metoprorol and an α1- adrenoceptor blocker doxazosin. Both were administered to 12 healthy volunteer men. CAVI and baPWV were measured every one hour for 6 hours using VaSera.

RESULTS

When metoprolol (80 mg) was administered to 12 healthy volunteer men, systolic blood pressure decreased from 131.4 ± 4.5 to 118.3 ± 4.1 mmHg (mean ± SE) (p < 0.05) at the 3rd hour, and diastolic blood pressure decreased from 85.3 ± 4.0 to 75.3 ± 3.0 mm Hg (p < 0.05). baP-WV decreased from 13.93 ± 0.46 to 12.46 ± 0.49 m/sec (p < 0.05), significantly, but CAVI did not change (8.16 ± 0.29 to 8.24 ± 0.27) (p = 0.449). ΔbaPWV at each time was significantly correlated with both Δsystolic and Δdiastolic blood pressures, but ΔCAVI was not correlated with either Δblood pressure. When doxazosin (4 mg) was administered to the same men, systolic blood pressure decreased from 130.2 ± 4.6 to 117.2 ± 4.8 mmHg (p < 0.05) at the 3rd hour. Diastolic blood pressure also decreased from 85.1 ± 4.1 to 74.2 ± 3.9 mmHg (p < 0.05). baPWV decreased from 13.98 ± 0.68 to 12.25 ± 0.53 m/sec (p < 0.05), significantly. CAVI also decreased from 8.15 ± 0.28 to 7.18 ± 0.37 (p < 0.05), significantly.

CONCLUSION

These results suggested that CAVI was not affected by blood pressure at the measuring time directly, but affected by the changes of contractility of smooth muscle cells.

Cystathionine-β-synthase gene transfer and 3-deazaadenosine ameliorate inflammatory response in endothelial cells

Although elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with increased inflammation and vascular remodeling, the mechanism of Hcy-mediated inflammation and vascular remodeling is unclear. The matrix metalloproteinases (MMPs) and adhesion molecules play an important role in vascular remodeling. We hypothesized that HHcy induces inflammation by increasing adhesion molecules and matrix protein expression. Endothelial cells were supplemented with high methionine, and Hcy accumulation was measured by HPLC. Nitric oxide (NO) bioavailability was detected by a NO probe. The protein expression was measured by Western blot analysis. MMP-9 activity was detected by gelatin-gel zymography. We demonstrated that methionine supplement promoted upregulation of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) through increased Hcy accumulation. In addition, increased synthesis of collagen type-1 was also observed. MMP-9 gene expression and protein activity were increased in methionine supplement groups. 3-Deazaadenosine (DZA), an adenosine analogue, prevented high methionine-induced ICAM-1 and VCAM-1 expression and collagen type-1 synthesis. Transfection of endothelial cells with cystathionine-β-synthase (CBS) gene construct, which converts Hcy to cystathionine, reduced Hcy accumulation in high methionine-fed cells. CBS gene transfection reduced the inflammatory response, as evident by attenuated ICAM-1 and VCAM-1 expression. Furthermore, collagen type-1 expression and MMP-9 activity were dramatically attenuated with CBS gene transfection. These results suggested that methionine supplement increased Hcy accumulation, which was associated with inflammatory response and matrix remodeling such as collagen type-1 synthesis and MMP-9 activity. However, in vitro DZA and CBS gene therapy successfully treated the HHcy-induced inflammatory reaction in the methionine metabolism pathway.

Dielectric relaxation of a protein–water system in atherosclerotic artery wall

Measurements of the dielectric properties of healthy and atherosclerotic human artery tissues were made in the frequency range of 100 Hz-100 kHz and temperatures from 22 to 260 degrees C. The temperature dependencies of the dielectric parameters for healthy tissues reveal distinctively the temperature ranges corresponding to the release of water up to 200 degrees C and the decomposition processes of elastin and collagen, above this temperature. The influence of atherosclerosis on the dielectric properties of artery tissues is significant in the whole temperature range. The relative permittivity for atherosclerotic tissues at the same temperature is much lower than for the healthy tissues. This suggests, that the polarization in atherosclerotic tissues due to protons hopping between a smaller number of sites than in healthy tissues, as a results of the thermal degradation of collagen-water. The data obtained above 200 degrees C indicate that the atherosclerosis induces the higher physico-chemical changes in the collagen when compared to elastin.

Matrix metalloproteinases and atherogenesis in dependence of age

BACKGROUND

Changes in the proteoglycan metabolism of the intima of arteries belong to the initial lesions of atherosclerosis (AS). The accumulation of proteoglycans, alterations of pericellular glycoproteins and modulations of collagen turnover also play a fundamental role in the progression of AS. They influence lipid retention, cell behavior and calcinosis. The decisive role played by the matrix metalloproteinases (MMPs) and their inhibiting factors (tissue inhibitors of metalloproteinases [TIMPs]) in these processes is not yet fully understood and therefore the subject of this overview. The causes of the abrupt change of a long-term existing stabile AS to a vulnerable plaque as well as the participation of age-related vascular wall remodeling in the progression of AS also remain open questions.

DISCUSSION

Apart from the well-known risk factors for AS, less well-known influences like the disturbances of gene expression in vascular smooth muscle cells affect an MMP/TIMP imbalance. The various consequences of this imbalance range from intima cell proliferation as an early change in AS as well as accelerated progression to the destabilization of fibrous plaques by increased collagenolysis as well as the formation of aneurysms. Infectious or toxic influences may trigger these mechanisms; an involvement of age-related vessel wall changes should also be considered. The prognostic significance of circulating MMP concentrations for the existence of instabile plaques are of great interest, as is the plaque stabilizing effect of statins by suppression of MMPs.

CONCLUSIONS

MMPs navigate the behavior of vascular wall cells in different AS stages, in adaptive remodeling, in normal aging and in non-atherosclerotic vessel disease. The clinical relevance of a disturbance in the MMP/TIMP balance is demonstrated firstly by the initiation of AS due to migration and proliferation of intima cells and secondly in the collagenolysis, necrotic transformation and apoptosis of existing fibrous lesions resulting in instabile rupture proned plaques. Investigations into the genetic typing of MMPs and the results of experimental gene deficiency models have significantly contributed to the clarification of these facts.

A novel blood pressure-independent arterial wall stiffness parameter; cardio-ankle vascular index (CAVI)

To measure the stiffness of the aorta, femoral artery and tibial artery noninvasively, cardio-ankle vascular index (CAVI) which is independent of blood pressure was developed. The formula for measuring this index is; CAVI=a{(2rho/DeltaP) x ln(Ps/Pd)PWV(2)} + b where, Ps and Pd are systolic and diastolic blood pressures respectively, PWV is pulse wave velocity between the heart and ankle, DeltaP is Ps - Pd, rho is blood density, and a and b are constants. This equation was derived from Bramwell-Hill's equation(1)), and stiffness parameter(2)). To elucidate the clinical utility of CAVI, the reproducibility and dependence on blood pressure were studied using VaSera (Fukuda Denshi Co., Ltd.). Furthermore, CAVI in hemodialysis patients with or without atherosclerotic diseases was measured. The average coefficient of variation for five measurements among 22 persons was 3.8%. In hemodialysis patients (n = 482), CAVI was correlated weakly with systolic and diastolic blood pressures (R = 0.175, 0.006), while brachial-ankle PWV was correlated strongly with systolic and diastolic blood pressures (R = 0.463, 0.335). CAVI in hemodialysis patients without signs of atherosclerotic diseases (NA) was 8.1 +/- 0.3 (mean +/- SD). That in patients receiving percutaneous transluminal coronary angioplasty was 8.8 +/- 0.3 (p < 0.05 vs. NA). CAVI in patients with ischemic change in their electrocardiogram (ECG) was 8.5 +/- 0.3 (p < 0.05 vs. NA). That in patients with diabetes mellitus was 8.5 +/- 0.3 (p < 0.002 vs. NA). CAVI in the patients with all three complications was 8.9 +/- 0.35 (p < 0.001 vs. NA). These results suggested that CAVI could reflect arteriosclerosis of the aorta, femoral artery and tibial artery quantitatively.

Alterations in structure and mechanics of resistance arteries from ouabain-induced hypertensive rats

We have previously described that chronic administration of ouabain induces hypertension and functional alterations in mesenteric resistance arteries. The aim of this study was to analyze whether ouabain treatment also alters the structural and mechanical properties of mesenteric resistance arteries. Wistar rats were treated for 5 wk with ouabain (8.0 microg/day sc). The vascular structure and mechanics of the third-order branches of the mesenteric artery were assessed with pressure myography and confocal microscopy. Total collagen content was determined by picrosirius red staining, collagen I/III was analyzed by Western blot, and elastin was studied by confocal microscopy. Vascular reactivity was analyzed by wire myography. Internal and external diameters and cross-sectional area were diminished, whereas the wall-to-lumen ratio was increased in arteries from ouabain-treated rats compared with controls. In addition, arteries from ouabain-treated rats were stiffer. Ouabain treatment decreased smooth muscle cell number and increased total and I/III collagens in the vascular wall. However, this treatment did not modify adventitia and media thickness, nuclei morphology, elastin structure, and vascular reactivity to norepinephrine and acetylcholine. The present work shows hypotrophic inward remodeling of mesenteric resistance arteries from ouabain-treated rats that seems to be the consequence of a combination of decreased cell number and impaired distension of the artery, possibly due to a higher stiffness associated with collagen deposition. The narrowing of resistance arteries could play a role in the pathogenesis of hypertension in this model.

Immunophenotypical characterization of contractile cells in caput epididymidis of men affected by congenital or post-inflammatory obstructive azoospermia

Myoid cells of the human caput epididymidis are replaced by large cells with ultrastructural features of smooth muscle cells (SMC) in chronic obstruction of the male genital tract. To evaluate whether these cellular changes are associated with different functional phenotypes we analysed the immunohistochemical expression of myosin heavy chain isoforms and of extracellular matrix (EM) components in the human caput epididymidis contractile cells in normal and in obstructed epididymides. Normal caput epididymidis myoid cells expressed a scattered immunostaining for SM2, marker of differentiated contractile SMC, while no staining was detected for SMemb (the non-muscle-type myosin heavy chain isoform) and for its transcription factor BTEB2, markers of undifferentiated proliferating SMC. A faint immunoreaction (IR) for EM was observed in the peritubular wall of the normal caput. In the contractile wall of the obstructed caput epididymidis a strong IR was detected for all myosin heavy chain isoforms as well as for collagen type IV and for fibronectin, markers for a secretory function of SMC. These findings, unknown in other models of SMC pathophysiology, suggest that myoid cells resume the molecular machinery of both mature SMC and of differentiating/secretory cells in the chronic obstruction of the human caput. Contractile cells of the epididymal duct represent a unique model to study the plasticity of SMC.

B-Myb represses vascular smooth muscle cell collagen gene expression and inhibits neointima formation after arterial injury

OBJECTIVE

The function of B-Myb, a negative regulator of vascular smooth muscle cell (SMC) matrix gene transcription, was analyzed in the vasculature.

METHODS AND RESULTS

Mice were generated in which the human B-myb gene was driven by the basal cytomegalovirus promoter, and 3 founders were identified. Mice appeared to develop normally, and human B-myb was expressed in the aortas. Total B-Myb levels were elevated in aortas of adult transgenic versus wild-type (WT) animals and varied inversely with alpha1(I) collagen mRNA expression. However, neonatal WT and transgenic aortas displayed comparable levels of alpha1(I) collagen mRNA, likely resulting from elevated levels of cyclin A, which ablated repression by B-Myb. Aortic SMCs from adult transgenic animals displayed decreased alpha1(I) collagen mRNA levels. To examine the role of B-Myb after vascular injury, animals were subjected to femoral artery denudation, which induces SMC-rich lesion formation. A dramatic reduction in neointima formation and lumenal narrowing was observed in arteries of B-myb transgenic versus WT mice 4 weeks after injury.

CONCLUSIONS

Data indicate that B-Myb, which inhibits matrix gene expression in the adult vessel wall, reduces neointima formation after vascular injury. To analyze B-Myb function in the vasculature, mice overexpressing B-myb were generated. Neonates displayed normal alpha1(I) collagen mRNA levels, whereas adults expressed decreased collagen mRNA in aortas and isolated vascular SMCs. On femoral artery denudation, neointima formation was dramatically reduced in B-myb transgenic mice.

Von Willebrand factor present in fibrillar collagen enhances platelet adhesion to collagen and collagen-induced platelet aggregation

We examined the basis of the differences observed between different collagen preparations in their ability to aggregate platelets and support their adhesion under flow. As in previous studies, we found fibrillar collagen to be 10-fold more potent than acid-soluble collagen in inducing platelet aggregation and found that acid-soluble collagen did not support the adhesion of washed platelets under flow. Further, platelets in whole blood adhered to surfaces coated with either fibrillar or acid-soluble collagen, but thrombi formed faster and grew larger on fibrillar collagen. As a possible basis for this difference, we found that fibrillar collagen, but not acid-soluble collagen, contains a substantial quantity of von Willebrand factor (VWF), as demonstrated by enzyme-linked immunosorbent assay and by the ability of fibrillar collagen to support the adhesion of VWF antibody-coated beads and to agglutinate GPIb-IX-V complex-expressing Chinese hamster ovary cells. Supporting a role for VWF in collagen-induced platelet aggregation, aggregation induced by acid-soluble collagen was greatly enhanced by added VWF. Further, platelet aggregation by fibrillar collagen was partially blocked by a GPIbalpha antibody that inhibits the GPIb-VWF interaction. Taken together, these results suggest that much of the difference in prothrombotic potency of different collagens is directly related to their differences in VWF content. This probably accounts for the different conclusions made regarding the relative importance of different direct and indirect collagen receptors in collagen-dependent platelet functions and further emphasizes the close synergistic roles of the GPIb-IX-V complex and the collagen receptors GPVI and alpha2beta1 in supporting platelet adhesion.

Shear stress-induced collagen XII expression is associated with atherogenesis

Fluid shear stress has been shown to modulate various endothelial functions. We selected a shear stress-specific clone, identified as collagen XII, from a bovine aortic endothelial cell (BAEC) cDNA library. We confirmed that shear stress induces collagen XII expression at both the mRNA and protein levels in cultured BAECs and human umbilical vein ECs (HUVECs) by stimulating transcription. When HUVECs were exposed to shear stress, they secreted collagen XII protein and it was deposited underneath them. Strong expression of collagen XII was found in the intima of human aortic wall lacking atherosclerotic lesions, whereas weak expression was seen in the intima of atherosclerotic plagues. Furthermore, the downstream portion of atherosclerotic plaques showed apparently weak collagen XII expression compared with the upstream portion. These results suggest that collagen XII expression induced by fluid shear stress may play a role in stabilizing the vascular structure and preventing the formation of atherosclerotic lesions.

Collagen-binding domain of a Clostridium histolyticum collagenase exhibits a broad substrate spectrum both in vitro and in vivo

The substrate spectrum of the tandem collagen-binding domain (CBD) of Clostridium histolyticumclass I collagenase (ColG) was examined both in vitro and in vivo. CBD bound to insoluble type I, II, III and IV collagens in vitro, and to skin, aorta, tendon, kidney, trachea and corneal tissues containing various types of collagen fibrils or sheets. CBD bound to all kinds of collagen fibrils regardless of their diameters and also bound to sheet-forming collagen in the glomerular basal lamina or Descemet's membrane of the cornea. This wide substrate spectrum expands possible applications of the drug delivery system we proposed previously (PNAS 95:7018-7023, 1998). Therapeutic agents fused with CBD will bind not only to subcutaneous tissues, but also to other tissues containing non-type I collagen.

Collagen characteristics and organization during the progression of cholesterol-induced atherosclerosis in Japanese quail

This study reports the concentration of collagen and its hydroxypyridinoline crosslinks, collagen fibril organization in the dorsal aortas, and systolic blood pressure during the progression of atherosclerosis in Japanese quail selected for cholesterol-induced atherosclerosis. The quail were placed on either a control or 0.5% cholesterol-added diet at approximately 16 weeks of age. The concentration of total collagen did not change in the control arteries during the course of the study, whereas at 5 and 10 weeks of cholesterol feeding, collagen levels decreased in the cholesterol-fed birds. Hydroxypyridinoline concentration increased during the duration of the study in the cholesterol-fed birds and by 15 and 20 weeks of cholesterol feeding, levels were significantly increased over those observed in the control arteries. Transmission electron microscopy showed changes in the organization of collagen fibrils. Increased systolic blood pressure was noted beginning at 10 weeks of cholesterol feeding, which is suggestive of other systemic changes induced by hypercholesterolemia. These results demonstrated remodeling of the collagen component of the dorsal aorta extracellular matrix during the progression of atherosclerosis and are suggestive of other systemic cardiovascular system changes.

Distribution and expression of type VI collagen in photoaged skin

BACKGROUND

Several of the characteristic clinical features of photoaged skin, including wrinkling, are thought to be dependent on changes in the dermal matrix brought about by chronic sun exposure. Such changes include reductions in collagens I, III and VII, an increase in elastotic material in the reticular dermis and a marked reduction in the microfibrillar glycoprotein fibrillin.

OBJECTIVES

To examine whether type VI collagen, a microfibrillar collagen necessary for cell-cell and cell-matrix communication, is affected by the photoageing process.

METHODS

Six healthy volunteers with moderate to severe photoageing were enrolled into the study. Immunohistochemistry and in situ hybridization histochemistry were used to examine the levels of type VI collagen in photoprotected and photoaged sites.

RESULTS

In photoprotected skin, type VI collagen was concentrated in the papillary dermis immediately below the dermal-epidermal junction, around blood vessels, hair follicles and glandular structures. The distribution of type VI collagen was unchanged in photoaged skin, although we observed an increase in the abundance of the alpha3 chain of collagen VI in the upper papillary dermis, at its junction with the dermal-epidermal junction (P < 0.05). No alterations were observed for any alpha chain at the mRNA level.

CONCLUSIONS

These studies suggest that chronic sun exposure (photoageing) has little or no effect on either the distribution, abundance or levels of expression of type VI collagen in human skin. Thus, type VI collagen, unlike other matrix components so far studied, appears to be relatively unaffected by the photoageing process.

Mechanisms by which bradykinin promotes fibrosis in vascular smooth muscle cells: role of TGF-beta and MAPK

Accumulation of extracellular matrix (ECM) is a hallmark feature of vascular disease. We have previously shown that hyperglycemia induces the expression of B(2)-kinin receptors in vascular smooth muscle cells (VSMC) and that bradykinin (BK) and hyperglycemia synergize to stimulate ECM production. The present study examined the cellular mechanisms through which BK contributes to VSMC fibrosis. VSMC treated with BK (10(-8) M) for 24 h significantly increased alpha(2)(I) collagen mRNA levels. In addition, BK produced a two- to threefold increase in alpha(2)(I) collagen promoter activity in VSMC transfected with a plasmid containing the alpha(2)(I) collagen promoter. Furthermore, treatment of VSMC with BK for 24 h produced a two- to threefold increase in the secretion rate of tissue inhibitor of metalloproteinase 1 (TIMP-1). The increase in alpha(2)(I) collagen mRNA levels and alpha(2)(I) collagen promoter activity, as well as TIMP-1 secretion, in response to BK were blocked by anti-transforming growth factor-beta (anti-TGF-beta) neutralizing antibodies. BK (10(-8) M) increased the endogenous production of TGF-beta1 mRNA and protein levels. Inhibition of the mitogen-activated protein kinase (MAPK) pathway by PD-98059 inhibited the increase of alpha(2)(I) collagen promoter activity, TIMP-1 production, and TGF-beta1 protein levels observed in response to BK. These findings provide the first evidence that BK induces collagen type I and TIMP-1 production via autocrine activation of TGF-beta1 and implicate MAPK pathway as a key player in VSMC fibrosis in response of BK.

Type V collagen regulates the assembly of collagen fibrils in cultures of bovine vascular smooth muscle cells

Vascular smooth muscle cells (SMCs), the major cellular constituent of the medial layer of an artery, synthesize the majority of connective tissue proteins, including fibrillar collagen types I, III, and V/XI. Proper collagen synthesis and deposition, which are important for the integrity of the arterial wall, require the antioxidant vitamin C. Vitamin C serves as cofactor for the enzymes prolyl and lysyl hydroxylase, which are responsible for the proper hydroxylation of collagen. Here, the role of type V collagen in the assembly of collagen fibrils in the extracellular matrix (ECM) of cultured vascular SMCs was investigated. Treatment of SMCs with vitamin C resulted in a dramatic induction in the levels of the cell-layer associated pepsin-resistant type V collagen, whereas only a minor induction in the levels of types I and III collagen was detected. Of note, the deposition of type V collagen was accompanied by the formation of striated collagen fibrils in the ECM. Immunohistochemistry demonstrated that type V collagen, but not type I collagen, became masked as collagen fibrils matured. Furthermore, the relative ratio of type V to type I collagen decreased as the ECM matured as a function of days in culture, and this decrease was accompanied by an increase in the diameter of collagen fibrils. Together these results suggest that the masking of type V collagen is caused by its internalization on continuous deposition of type I collagen on the exterior of the fibril. Furthermore, they suggest that type V collagen acts as framework for the initial assembly of collagen molecules into heterotypic fibrils, regulating the diameter and architecture of these fibrils.

Quantitative changes in collagen levels following 830-nm diode laser welding

BACKGROUND AND OBJECTIVE

The actual mechanism by which laser irradiation welds tissue is presently unknown; however, collagen is a major constituent of tissue welded by laser irradiation.

STUDY DESIGN/MATERIALS AND METHODS

Collagen was extracted from the abdominal aorta of Wistar rats by acetic acid extraction and repeated pepsin digestion after tissue welding (254 W/cm2) by using an 830-nm diode laser. The collagen levels were determined by using the Sircol Collagen Assay (Biocolor, Northern Ireland).

RESULTS

Compared with untreated aorta, the collagen content of the treated vessel was obvious decreased (P < 0.001) immediately after laser irradiation. Levels then increased by day 3, with a peak at day 10 (P < 0.002). The collagen content returned to normal levels on day 30 and remained at this level throughout the rest of the experimental period.

CONCLUSION

These results suggest that a proportion of the collagen molecules in the vessel are denatured by the heat of the laser. Collagen synthesis is stimulated during the healing process after laser welding with the parameters used in the present study.

Modulation of collagen synthesis by tumor necrosis factor alpha in cultured vascular smooth muscle cells

Collagen synthesis in vascular smooth muscle cells (SMCs) after exposure to tumor necrosis factor alpha (TNF-alpha) was investigated using a culture system. The synthesis of collagenase-digestible proteins (CDP) and noncollagenous proteins (NCP) was evaluated by the [3H]proline incorporation. It was shown that TNF-alpha markedly suppresses the incorporation of [3H]proline into both CDP and NCP in confluent cultures of SMCs but not in sparse cultures of the cells. Such a marked suppression by TNF-alpha was not observed in confluent bovine aortic endothelial cells and human fibroblastic IMR-90 cells. In confluent SMCs, the synthesis of CDP was more strongly inhibited by TNF-alpha than that of NCP. When the CDP synthesis was stimulated by transforming growth factor beta, TNF-alpha suppressed the stimulation in both confluent and sparse SMCs. Human SMCs synthesized types I, III, IV and V collagens; TNF-alpha markedly decreased the relative proportion of types IV and V. It was therefore suggested that TNF-alpha modulates the collagen synthesis by SMCs depending on their cell density and modifies the formation of atherosclerotic lesions.

Expression and localization of the proteoglycan decorin during the progression of cholesterol induced atherosclerosis in Japanese quail: implications for interaction with collagen type I and lipoproteins

The temporal and spatial distribution, and relative levels of the proteoglycan decorin and collagen type I were examined during the progression of atherosclerosis in the dorsal aortas of Japanese quail selected for cholesterol induced atherosclerosis. The quail were placed on either a control or 0.5% added cholesterol diet at approximately 16 weeks of age. Dorsal aortas were collected at 1- or 2-week intervals over a 15-week period after initiating cholesterol feeding. Biochemical analysis for decorin and collagen type I showed that both increased in the cholesterol-fed birds compared to control-fed birds beginning at 9 weeks and continued through the duration of the study. Through immunohistochemical staining for decorin and collagen type I, the spatial localization of decorin and collagen type I in control and less severe plaques in cholesterol-fed birds was most prominent in the arterial adventitia. However, in severe atherosclerotic plaques, decorin was localized in foam cell regions and collagen type I was found surrounding the foam cell regions where decorin accumulated. These results demonstrated a localization of decorin in the core of the atherosclerotic plaque foam cell region with collagen type I being located on the plaque surface.

Distribution and localization of cells and collagens in the proliferated intima of arterially implanted autovein grafts

We examined the microscopic features and distribution of collagens in the hyperplastic intima of arterially implanted autovein bypass grafts under conditions of a reduced blood flow with a poor distal outflow. Vascular anastomosis was made using 7-0 nonabsorbable polypropylene sutures (PP group), or absorbable polydioxanone sutures (PDS group). On the contralateral limb, an autovein bypass graft was performed under normal flow conditions (NF group). The thickness of the intima in the NF group was approximately 50 microm throughout the duration of the study, while in the PP and PDS groups, intimal hyperplasia progressed to 290+/-112 microm and 267+/-123 microm, respectively, at 13 months after grafting. Collagen accumulated significantly in both the PP and PDS groups; types IV and V collagen in particular increased considerably in the deep layer. Regardless of the suture materials, the progression of intimal hyperplasia was considered to be closely related to the poor distal outflow to be and caused by the proliferation of myofibroblasts and active production of collagen. The increase in types IV and V collagen, particularly in the deep layer of the hyperplastic intima, was due to development of numerous vasa vasora in this region.

Oxidized LDL-containing immune complexes induce Fc gamma receptor I-mediated mitogen-activated protein kinase activation in THP-1 macrophages

Our previous studies have shown that Fc gamma receptor (FcgammaR)-mediated uptake of LDL-containing immune complexes (oxLDL-ICs) by human monocyte-derived macrophages leads to not only transformation of macrophages into foam cells but also macrophage activation and release of cytokines. It has been shown that cross-linking of FcgammaR triggers activation of signal transduction pathways that alter gene expression in macrophages. In this study, we determined whether engagement of FcgammaR by oxLDL-ICs leads to activation of mitogen-activated protein (MAP) kinase pathway, a signaling cascade serving many important functions, including the regulation of gene expression, in THP-1 macrophage-like cells. Our results from immunoblotting, using specific anti-phosphorylated MAP kinase antibodies, showed that oxLDL-ICs induced extracellular signal regulated kinase 2 (ERK2) MAP kinase phosphorylation in THP-1 macrophage-like cells in time- and dose-dependent manners. Cholesterol loading before stimulation led to a longer phosphorylation of ERK2. Nuclear translocation of phosphorylated ERK was markedly increased after the stimulation. Moreover, our data showed that oxLDL-IC induction of MAP kinase was prevented by human monomeric IgG1, suggesting that the specific engagement of type I FcgammaR by oxLDL-IC is responsible for the MAP kinase activation. Finally, we showed that human anti-oxLDL autoantibody-containing immune complexes immobilized on type I collagen induced MAP kinase activation in THP-1 cells. These results strongly suggest that oxLDL-IC, which has been detected in atherosclerotic plaques, may play an important role in macrophage activation and atherogenesis.

Complete processing of type III collagen in atherosclerotic plaques

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.

An immunohistochemical study of collagens in trachoma and vernal keratoconjunctivitis

PURPOSE

To analyse the distribution and types of collagen in the conjunctiva of patients with trachoma and vernal keratoconjunctivitis (VKC).

METHODS

Conjunctival biopsy specimens were collected from 9 patients with active trachoma, 9 patients with scarred trachoma, 6 patients with active VKC and 9 control subjects. The presence and distribution of collagen was assessed microscopically with immunohistochemical techniques and a panel of monoclonal and polyclonal antibodies directed against types I, III, IV and V collagen.

RESULTS

In normal conjunctiva, the staining for types I and III collagen was localised to the substantia propria. Type IV collagen was located in the epithelial, vascular endothelial and accessory lacrimal gland basement membranes. Staining for type V collagen was absent. New type V collagen deposition close to basement membranes was noted in active trachoma, scarred trachoma and VKC. The extent of deposition of type V collagen was markedly increased in scarred trachoma when compared with active trachoma. Staining for type IV collagen showed irregularly thickened epithelial basement membrane in active trachoma, and a marked increase in basement membrane type IV collagen was noted in scarred trachoma. Immunoreactivity of types I and III collagen increased in active trachoma and decreased in scarred trachoma. VKC conjunctiva contained increased amounts of types I, III and IV collagen due to marked increase in the thickness of vascular endothelial basement membrane and very prominent deposition of types I and III collagen around stromal vessels.

CONCLUSIONS

Our data indicate new type V collagen formation in the conjunctiva from patients with active trachoma, scarred trachoma and VKC. Increased deposition of types I, III and IV collagen is noted in VKC and active trachoma. Our findings suggest that increased deposition of type IV collagen and new type V collagen formation contributes to the development of conjunctival fibrosis in scarred trachoma.

Collagen content and types in trachomatous conjunctivitis

PURPOSE

To study alterations in conjunctival collagen in the conjunctiva of patients with active trachoma.

METHODS

We studied conjunctival biopsy specimens obtained from nine subjects with active trachoma and from four control subjects. We used immunohistochemical techniques and a panel of monoclonal and polyclonal antibodies directed against types I, III, IV and V collagen.

RESULTS

In normal conjunctiva, the staining for types I and III collagen was localised to the substantia propria. Type IV collagen was located in the epithelial and capillary endothelial basement membranes. The staining for type V collagen was absent. In trachoma biopsy specimens, staining for types I and III collagen showed collagen fibrils among epithelial cells, patchy increase in staining intensity in the upper stroma, and thicker and irregularly arranged collagen fibrils in the substantia propria. Staining for type IV collagen showed irregularly thickened epithelial basement membrane. Staining for type V collagen showed patchy staining in the upper substantia propria; it was also noted in the cytoplasm of fibroblasts, in the walls of blood vessels in the substantia propria, and in the walls of accessory lacrimal glands.

CONCLUSIONS

Our data indicate new type V collagen formation, and increased types I, III and IV collagen content, in the conjunctiva from patients with active trachoma.

Extracellular matrix components in uterine leiomyoma and their alteration during the tumour growth

It was found that both normal human myometrium and uterine leiomyoma contain several glycosaminoglycans. In contrast to many normal and tumour tissues the amount of hyaluronic acid is very low and the proportional amount of sulphated glycosaminoglycans is distinctly higher. It is of interest that heparan sulphate is the major glycosaminoglycan component both in normal myometrium, and in leiomyoma. The amount of hyaluronic acid in myometrium and in the leiomyoma is very low. No significant change in hyaluronate content was observed during the tumour growth. In contrast to that the amount of some sulphated glycosaminoglycans (heparan sulphate, keratan sulphate, chondroitin sulphates and heparin) distinctly increased. It is suggested that some of the GAGs participate in the creation of a storage depot for biologically active molecules (growth factors, enzymes) which are thereby stabilized and protected. Hydrolytic degradation of some GAGs may result in the release of some cytokines which may promote the tumour growth and stimulate collagen biosynthesis by tumour cells.

Detection of type III collagen fragments in specimens of abdominal aortic aneurysms

The purpose of this study was to analyze the collagens in aortic aneurysm walls and to investigate the mechanism of the formation of calcified abdominal aortic aneurysms (AAAs). Collagens were extracted from human aneurysmal aortic walls obtained during surgery, and from human nonaneurysmal aortic walls obtained at autopsy, using pepsin-acetic acid digestion. Electrophoresis and immunoblotting were performed. Type III collagen was found to be reduced in the arteriosclerotic aneurysmal aortic walls. The alpha1 chain of type II collagen/alpha1 chain of type I collagen ratio was 0.35+/-0.11 in the aortic aneurysms and 0.68+/-0.11 in the nonaneurysmal aortic walls (P=0.0111). All the calcified aneurysms were associated with type III collagen fragments having molecular mass of approximately 70 kDa and 30 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Thus, we concluded that AAAs with calcification may be caused by an abnormal degradation of type III collagen.

Basic fibroblast growth factor decreases type V/XI collagen expression in cultured bovine aortic smooth muscle cells

Vascular smooth muscle cells (SMCs), the major cellular constituent of an artery, synthesize the bulk of fibrillar collagens, including type V/XI, which regulates heterotypic collagen fibril assembly. Basic fibroblast growth factor (bFGF) is a heparin-binding polypeptide growth factor that has been implicated in important events during the development of atherosclerosis, such as early intimal SMC proliferation. Here we have investigated the effects of bFGF on aortic SMC expression of type V/XI collagen. Treatment of exponentially growing or serum-deprived subconfluent cultures of bovine aortic SMCs with bFGF decreased the steady-state levels of the mRNAs for collagen type V/XI, including alpha 1(V), alpha 2(V), and alpha 1(XI). The effect of bFGF was time dependent with a two- and a fourfold decrease in alpha 2(V) mRNA observed after treatment for 24 and 48 h, respectively. This decrease resulted from a drop in the rate of alpha 2(V) gene transcription; no change was observed in the stability of the alpha 2(V) mRNA. Furthermore, accumulation of collagen protein decreased upon bFGF treatment. As expected, treatment with bFGF increased the rate of proliferation of serum-deprived SMCs, as judged by DNA content in the cultures, thymidine incorporation, and steady-state mRNA levels of the S-phase-expressed histone H3.2. These results suggest that bFGF plays an important role in the regulation of collagen fibril structure, with potential implications for the development and organization of an atherosclerotic lesion.

In vitro interactions of oxidatively modified LDL with type I, II, III, IV, and V collagen, laminin, fibronectin, and poly-D-lysine

The accumulation of LDL in the arterial intima is considered a key event in atherogenesis. We investigated the binding of oxidized LDL (ox-LDL) to microtiter plates coated with type I or II collagen, laminin, fibronectin, or poly-D-lysine. Oxidation of LDL, 125I-LDL, or Eu(3+)-LDL was performed with CuCl2, varying the time of oxidation. Bound lipoprotein was assessed by counting radioactivity or fluorescence in the wells. Binding of highly ox-LDL in PBS followed the order: type I collagen > poly-D-lysine > type II collagen > laminin > fibronectin. Comparing various collagen types, the binding of ox-LDL followed the order: type I > type V and, type III > type IV > type II collagen. Binding of ox-LDL in PBS was dependent on an increase in negative charge of ox-LDL. Testing certain amino acids as competitors for binding of highly ox-LDL to type I collagen put lysine first, followed by arginine and histidine. On laminin, histidine competed most, followed by lysine and arginine. When studying the influence of Na+, K+, Ca2+, Mg2+ (equivalent to their concentrations in the interstitial fluid), native LDL, moderately ox-LDL, and highly ox-LDL showed the same affinity to type I collagen. However, a fivefold dilution of the buffer increased the affinity of moderately and highly ox-LDL 3.9- and 10-fold compared with native LDL. Application of the F(ab')2 from a monoclonal antibody to ox-LDL revealed a strong competition of the binding of highly ox-LDL to type II collagen (60%), laminin (35%), type I collagen (20%), and poly-D-lysine (15%), whereas the binding to fibronectin was not affected.

Injury-induced enzymatic methylation of aging collagen in the extracellular matrix of blood vessels

As a result of blood vessel injury, protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT), a normally intracellular enzyme, becomes trapped within the meshwork of the vascular extracellular matrix where it can methylate substrate proteins. In this investigation we examined the distribution of such altered aspartyl-containing substrate proteins in the vascular wall. Nearly 90% of all the altered aspartyl residues were inaccessible to intracellular PIMT. Proteins of the extracellular matrix were found to be the major repository of altered aspartyl-containing polypeptides in the blood vessel wall, accounting for approximately 70% of the total amount. Proteolytic cleavage of extracellular matrix proteins with cyanogen bromide (CNBr) revealed that collagens account for most of the altered aspartyl-containing proteins of the ECM. As a consequence of blood vessel injury, both type I and type III collagen along with other proteins were found to become methylated by injury-released PIMT. It is estimated that 1 cm of vein contains on the order of 5 x 10(14) altered aspartyl residues involving between 1% and 5% of the total extracellular protein.

The proteoglycan decorin links low density lipoproteins with collagen type I

Decorin is a small dermatan sulfate-rich proteoglycan which binds to collagen type I in vitro and in vivo. In atherosclerotic lesions the contents of low density lipoprotein (LDL), decorin, and collagen type I are increased, and ultrastructural studies have suggested an association between LDL and collagen in the lesions. To study interactions between LDL, decorin, and collagen type I, we used solid phase systems in which LDL was coupled to a Sepharose column, or in which LDL, decorin, or collagen type I was attached to microtiter wells. The interaction between LDL and decorin in the fluid phase was evaluated using a gel mobility shift assay. We found that LDL binds to decorin by ionic interactions. After treatment with chondroitinase ABC, decorin did not bind to LDL, showing that the glycosaminoglycan side chain of decorin is essential for LDL binding. Acetylated and cyclohexanedione-treated LDL did not bind to decorin, demonstrating that both lysine and arginine residues of apoB-100 are necessary for the interaction. When collagen type I was attached to the microtiter plates, only insignificant amounts of LDL bound to the collagen. However, if decorin was first allowed to bind to the collagen, binding of LDL to the decorin-collagen complexes was over 10-fold higher than to collagen alone. Thus, decorin can link LDL with collagen type I in vitro, which suggests a novel mechanism for retention of LDL in collagen-rich areas of atherosclerotic lesions.

Coordinated effects of fibroblast growth factor-2 on expression of fibrillar collagens, matrix metalloproteinases, and tissue inhibitors of matrix metalloproteinases by human vascular smooth muscle cells. Evidence for repressed collagen production and activated degradative capacity

Fibroblast growth factor-2 (FGF-2) is an established mediator of smooth muscle cell (SMC) proliferation after vascular injury. However, the influence of FGF-2 on collagen fiber remodeling, which may be a prerequisite for vascular SMC accumulation, is not well understood. We determined that FGF-2 almost completely abrogated the formation of immunodetectable type I collagen fibers in the extracellular matrix of cultured human vascular SMCs. This was associated with reduced expression of pro alpha-chains for types I and III collagen, as assessed by Western blot analysis, and a corresponding reduction in collagen synthesis. Densitometry of Northern blots indicated a potent reduction of mRNA encoding pro alpha-chains for types I and III collagen and a minor reduction in mRNA for pro alpha-chains for type V collagen. Interstitial collagenase (MMP-1), which is required for degradation of collagen types I and III, was not expressed by SMCs under basal culture conditions, but expression was induced by FGF-2, with a potent, dose-dependent increase in MMP-1 protein in conditioned medium. Metalloproteinase inhibitors TIMP-1, TIMP-2, and TIMP-3 were expressed by unstimulated SMCs and were differentially regulated by FGF-2. TIMP-1 expression increased modestly, TIMP-2 expression was repressed, and TIMP-3 was relatively unaffected. The net effect on substrate degradation, as assessed by zymography of conditioned media, was induction of MMP-1 lytic activity by FGF-2, with no effect on the activity of MMP-2, MMP-3, or MMP-9. These data indicate that stimulation of human SMCs with FGF-2 establishes a phenotype in which collagen fiber production is repressed and the capacity for fiber degradation activated. This coordinated response may be critical for SMC accumulation during vascular remodeling as well as atherosclerotic plaque destabilization.

Collagen subtypes III and IV expression in human vein graft atherosclerosis

This study examined the expression of collagen subtypes III and IV in a series of freshly excised human venous coronary artery bypass grafts. The results of this study demonstrate that these collagen subtypes are differentially expressed in vein graft atherosclerosis.

Effect of glycated collagen on proliferation of human smooth muscle cells in vitro

While non-enzymatic glycation of long-lived tissue proteins such as collagen has been implicated in chronic complications of diabetes mellitus, its role in the aetiology of diabetic macroangiopathy has not been elucidated. To test the hypothesis that glycation of collagen abolishes the inhibitory effect of native collagen on the proliferation of human smooth muscle cells, we obtained smooth muscle cells from human gastric arteries and cultured them on dishes coated with glycated or non-glycated collagen. The proliferation of human smooth muscle cells in the presence of 10% fetal calf serum or platelet derived growth factor-BB (10 ng/ml) was inhibited by type 1 collagen coated on the dishes. Glycation of collagen with glucose 6-phosphate for 7 days abolished the growth-inhibitory effect of native collagen. Succinylation of collagen, which like glycation blocked the lysyl residues in collagen, also abolished the growth-inhibitory effect. Adhesion of human smooth muscle cells to collagen-coated dishes was not affected by glycation of collagen. Addition of glycated albumin to the medium did not affect the growth of human smooth muscle cells on plastic dishes. The inhibition of human smooth muscle cell proliferation by collagen was not reversed by the glycation of collagen in the presence of aminoguanidine. Results suggest that early glycation abolishes the inhibitory effect of collagen on human smooth muscle cell proliferation and may thus participate in the progression of macro-angiopathy in diabetes.

Collagen and glycosaminoglycans of Wharton's jelly and their alterations in EPH-gestosis

Some prenatal pathological processes may be caused by biochemical and morphological alterations in the umbilical cord (UC). EPH-gestosis is the most common pregnancy-associated pathological process. For these reasons the role of collagen and glycos-aminoglycans (GAGs) of UC in pathobiochemistry of this syndrome seems to be important. We studied histology of extracellular matrix components, quantity, solubility and molecular polymorphism of collagen, proportional relationships between various types of collagen, the amounts of GAGs and proportional relationships between them in Wharton's jelly of control newborns delivered by healthy mothers and those delivered by mothers with EPH-gestosis. We found that Wharton's jelly is abundant in collagen and GAGs. This collagen is very insoluble and resistant to the action of depolymerizing agents (4% EDTA-Na2, pepsin). Types I, III and V collagens were isolated and quantified. Hyaluronic acid constitutes about 70%, whereas sulphated GAGs constitute about 30% of total GAGs. EPH-gestosis is accompanied by significant increase in sulphated GAGs: hyaluronic acid ratio. The EPH-gestosis-associated alterations in Wharton's jelly correspond to 'premature ageing' of this tissue.