Donate Help Contact The AHA Sign In Home
American Heart Association
Circulation
Search: search_blue_button Advanced Search
Circulation. 2001;103:576-583

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Konstantinides, S.
Right arrow Articles by Loskutoff, D. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Konstantinides, S.
Right arrow Articles by Loskutoff, D. J.
Related Collections
Right arrow Animal models of human disease
Right arrow Genetically altered mice
Right arrow Physiological and pathological control of gene expression
Right arrow Arterial thrombosis
Right arrow Coagulation and fibronolysis
Right arrow Other Vascular biology

(Circulation. 2001;103:576.)
© 2001 American Heart Association, Inc.


Basic Science Reports

Plasminogen Activator Inhibitor-1 and Its Cofactor Vitronectin Stabilize Arterial Thrombi After Vascular Injury in Mice

Stavros Konstantinides, MD; Katrin Schäfer, MD; Therese Thinnes, BS; David J. Loskutoff, PhD

From the Department of Vascular Biology, The Scripps Research Institute, La Jolla, Calif.

Correspondence to David J. Loskutoff, PhD, The Scripps Research Institute, Department of Vascular Biology, VB-3, 10550 N Torrey Pines Rd, La Jolla, CA 92037. E-mail loskutof{at}scripps.edu


*    Abstract
up arrowTop
*Abstract
down arrowIntroduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Background—The origin and contribution of plasminogen activator inhibitor-1 (PAI-1) and its cofactor vitronectin (VN) to arterial thrombosis/thrombolysis in vivo is controversial.

Methods and Results—Ferric chloride was used to induce carotid artery injury in 97 wild-type (WT), 84 PAI-1-/-, and 84 VN-/- mice. Complete thrombotic occlusion was observed in 70% of PAI-1-/- mice versus 92% of WT (P<0.001) and 87% of VN-/- (P=0.015) mice. In vessels that occluded, mean times to occlusion were significantly longer in PAI-1-/- than in WT or VN-/- mice. The initial thrombotic response of VN-/- mice was similar to that of WT mice, but their thrombi were unstable and frequently embolized. As a result, the patency rate of carotid vessels 30 minutes after injury was as high in VN-/- mice (36%) as in PAI-1-/- mice (which demonstrate progressive thrombolysis) and significantly higher than that of WT mice (12%; P=0.013). Histochemical and reverse transcription–polymerase chain reaction studies revealed an early upregulation of PAI-1 mRNA and protein expression in the thrombus and the vessel wall, which persisted for >=1 week. VN protein also accumulated after injury, but VN mRNA levels remained low at all times.

Conclusions—PAI-1 and VN participate in the thrombotic response to arterial injury by preventing premature thrombus dissolution and embolization. The accumulation of PAI-1 in the thrombus/vessel wall after injury may result, at least in part, from local synthesis, whereas the VN protein appears to be derived from plasma.


Key Words: carotid arteries • genes • fibrinolysis • embolism


*    Introduction
up arrowTop
up arrowAbstract
*Introduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Plasminogen activator inhibitor-1 (PAI-1) is the principal physiological inhibitor of both tissue (tPA) and urokinase (uPA) plasminogen activators and is a key regulator of the fibrinolytic system.1 In humans, up to 90% of circulating PAI-1 is contained within platelet {alpha}-granules, and in vitro studies suggest that it may be responsible, at least in part, for the resistance of platelet-rich arterial thrombi to thrombolysis.2 3 Clinical studies correlate elevated circulating levels of PAI-1 with an increased risk of both arterial and venous thrombosis,4 and mice lacking PAI-1 are resistant to venous thrombosis.5 Despite this, the contribution of PAI-1 to stabilization of arterial thrombi in vivo remains controversial. For example, some studies reported that the thrombotic response to arterial injury was not significantly altered in PAI-1–deficient mice,6 whereas others demonstrated prolonged times to thrombosis in these mice.7 8 PAI-1 is a relatively unstable molecule in solution but is stabilized by binding to plasma-derived vitronectin (VN).3 9 Thus, VN may promote thrombosis by localizing active PAI-1 to sites of vascular injury. VN also may contribute to thrombosis by binding to platelet integrins.10 11 However, VN-deficient mice demonstrated a significantly enhanced thrombotic reaction to arterial injury,12 suggesting that it may have an antithrombotic role in vivo. These conflicting results emphasize the need for further studies to define the exact role of PAI-1 and VN in thrombus formation and dissolution.

In addition to their role in thrombosis and thrombolysis, PAI-1 and VN also influence cell migration and the chronic wound-healing response to vascular injury9 10 through interactions with uPA, the uPA receptor, and integrins.9 13 Although PAI-1 appears to participate in the vascular remodeling process in vivo,10 14 its role in injury models that focus on arterial thrombosis and thrombolysis remains to be established. Furthermore, the origin and expression of VN in the vessel wall after arterial injury have not yet been systematically studied.

In this report, we used the FeCl3 model6 15 in gene-inactivated mice to gain further insight into the role of PAI-1 and VN in the response to arterial injury and thrombosis. Our results indicate that PAI-1 and VN both participate in the early stages of the vascular response to injury by stabilizing the initial thrombus and preventing early fibrinolysis and premature embolization. They suggest that the increased PAI-1 in the organizing thrombus and the vessel wall during the remodeling process reflects local synthesis, whereas the increased VN appears to be derived from plasma.


*    Methods
up arrowTop
up arrowAbstract
up arrowIntroduction
*Methods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Experimental Animals
C57BL/6J wild-type (WT) mice were from Jackson Laboratories (Bar Harbor, Me), PAI-1–deficient (PAI-1-/-) mice were from Dr P. Carmeliet (Leuven, Belgium),5 and vitronectin-deficient (VN-/-) mice were from Dr D. Ginsburg (Ann Arbor, Mich).16 Only animals that were the product of >=8 backcrosses to the C57BL/6J genetic background were used. Genotyping of PAI-1-/- and VN-/- mice was performed as described previously.16 17 All animal care and experimental procedures complied with the Guide for the Care and Use of Laboratory Animals, US Department of Health and Human Services, and were approved by the Animal Research Committee of the Scripps Research Institute.

Carotid Injury and Thrombosis
Mice (6 to 8 weeks old) were subjected to carotid artery injury with 10% ferric chloride (FeCl3).6 15 Briefly, animals were anesthetized (Metofane, Schering-Plough), the left carotid artery was dissected, and then a 0.5x1.0-mm strip of Whatman No. 1 filter paper soaked in 10% FeCl3 solution was applied to the surface of the adventitia for 3 minutes. This led to the formation of a 2- to 3-mm-long carotid thrombus (Figure 1Down). Carotid blood flow was monitored with a miniature ultrasound flow probe (0.5VB, Transonic Systems) interfaced with a flowmeter (model T106, Transonic Systems) and a computerized data acquisition program (WinDaq, DATAQ Instruments). At the end of the 30-minute flow-monitoring period, some of the mice were killed with an overdose of the anesthetic for tissue harvest and processing (see below). For studies at later times, the surgical wound was sutured, the anesthesia was discontinued, and the mice were returned to their cages.



View larger version (39K):
[in this window]
[in a new window]
 
Figure 1. Carotid artery thrombosis induced by FeCl3. Left carotid artery (A, arrowhead) was exposed and elevated by 2 threads, and an ultrasound flow probe was placed around vessel. A strip of filter paper soaked in 10% FeCl3 was then applied to surface of adventitia for 3 minutes (B), leading to formation of platelet-rich thrombus (C; arrowheads). Magnification x10.

Tissue Harvest and Processing
At various times after injury, anesthetized animals were perfusion-fixed with 4% zinc formalin as described.18 The injured segment of the carotid artery was then excised such that its proximal, thinner edge corresponded to the proximal edge of the thrombus, whereas the distal, thicker edge included the carotid bifurcation. This allowed orientation of the segments for paraffin embedding. The isolated vessel segments were immersed in 4% zinc formalin for 4 hours, stored in 70% ethanol, embedded in paraffin blocks, and sectioned at 5-µm thickness for histological studies.

For gene expression studies, the animals were gently perfused with normal saline for 5 to 10 minutes. The thrombosed segment of the vessel was then removed, together with an {approx}1-mm-long noninjured, nonthrombosed margin of the carotid vessel on either side. The tissues were then snap-frozen in liquid nitrogen, and pairs of arteries were pooled for preparation of total RNA.

Histological and Immunohistochemical Studies
Masson’s trichrome reagent was used to localize fibrin, collagen, smooth muscle cells (SMCs), and platelets in the vessel after injury with FeCl3, and Perls’ iron stain was used to show the distribution of iron. Endothelial cells were identified with a rabbit anti-human/mouse von Willebrand factor (vWF) primary antibody (Dako; dilution, 1:100); SMCs were studied with a monoclonal anti–mouse {alpha}-actin primary antibody (Boehringer Mannheim; 1:20). Migrating and proliferating SMCs were identified by a polyclonal antibody to mouse vimentin19 (Santa Cruz; 1:50), and tissue-fixed macrophages were detected with a rat monoclonal CI:A3-1 antibody (BMA; 1:20). Finally, polyclonal rabbit anti-mouse antibodies were used to detect PAI-1 and VN. All incubation, blocking, and antigen unmasking steps were carried out as described.20 Sections incubated with nonimmune serum instead of the primary antibody served as negative controls.

Analysis of Gene Expression
Total RNA was extracted from pooled pairs of mouse carotid arteries with Ultraspec RNA (Biotecx) and chloroform, and PAI-1, VN, and ß-actin mRNA levels were determined by reverse transcription–polymerase chain reaction (RT-PCR),17 21 with 35 cycles used for VN and ß-actin and 30 cycles for PAI-1 and ß-actin. Aliquots of the PCR reaction (20 µL) were separated by electrophoresis through a 1.8% agarose gel, and the relative amount of the target (PAI-1 or VN) or the control (ß-actin) RNA was determined densitometrically with a computer-based image analyzer (Alpha Imager 2000, Alpha Innotech). Radiolabeled antisense and sense riboprobes for murine PAI-1 and VN were prepared, and in situ hybridization was performed17 21 with the pGEM-3Z vector system (Promega) in the presence of 35S-labeled UTP (>1200 Ci/mmol; Amersham). Hybridized slides were exposed in the dark as indicated, developed, and counterstained with hematoxylin and eosin. Parallel sections were hybridized with a sense probe as a control for nonspecific hybridization.

Statistical Analysis
Continuous variables are represented by mean values±SD. Differences between genotypes or time points within the same genotype were tested by ANOVA followed by the Bonferroni t test for pairs of means. Qualitative variables (eg, vascular patency rates at specific time points) were tested by {chi}2 and Fisher’s exact test. All statistical tests were 2-sided, with a value of P<0.05 indicating statistical significance.


*    Results
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
*Results
down arrowDiscussion
down arrowReferences
 
Role of PAI-1 and VN in Thrombosis and Recanalization After Injury
Carotid artery injury (see Figure 1Up) was induced in 97 WT, 84 PAI-1-/-, and 84 VN-/- mice, and hemodynamic (Figure 2Down), histological, and gene expression studies were performed. On induction of injury, rapid and complete thrombotic occlusion occurred in 92% of WT versus 87% of VN-/- mice but in only 70% of PAI-1-/- mice (P<0.001 and P=0.015 versus WT and VN-/- animals, respectively). In vessels that occluded (Figure 2BDown), the mean time to occlusion was significantly longer in PAI-1-/- versus WT (11.0±3.0 versus 8.7±1.9 minutes; P<0.001) or versus VN-/- (9.2±1.8 minutes; P<0.001) mice. Although no significant differences could be detected between WT and VN-/- animals at early times, the patency rate of injured carotid vessels at 30 minutes after injury (Figure 2CDown) was as high in VN-/- as in PAI-/- mice (36%) and significantly higher than that of WT animals (12%; P=0.013). Patency was slowly restored in the arteries of all mice, and by 7 to 21 days, there were no significant differences between the 3 genotypes. Analysis of flow profiles revealed that injury of WT mice (Figure 3ADown) generally resulted in rapid thrombosis without subsequent recanalization during the first 30 minutes. In contrast, {approx}30% of the vessels of PAI-1-/- mice failed to thrombose completely but instead underwent progressive thrombolysis over the 30-minute period (Figure 3BDown). In the VN-/- mice that occluded, the initial thrombotic response appeared to be similar to that of the WT animals, but the thrombi were unstable and repeatedly embolized (Figure 3CDown and 3DDown), leading to early recanalization and restoration of flow.



View larger version (11K):
[in this window]
[in a new window]
 
Figure 2. Thrombotic occlusion and recanalization after injury. Displayed are baseline rates of carotid blood flow in anesthetized WT, PAI-1-/-, and VN-/- mice (A), their times to thrombotic occlusion after injury (B), and their proportion of patent vessels at various times thereafter (C). Individual values for each animal are shown in A and B. Horizontal lines indicate mean for each genotype. C, Open bars represent WT mice; crosshatched bars, PAI-1-/-; and solid bars, VN-/-.



View larger version (83K):
[in this window]
[in a new window]
 
Figure 3. Characteristic flow profiles after FeCl3-induced injury. After recording baseline carotid blood flow (phase 1), ultrasound flow monitoring was interrupted for {approx}3 minutes to permit application of FeCl3 to vessel (phase 2). Filter was removed, and flow was monitored for next 30 minutes (phase 3). Typical flow patterns from WT mouse (A), PAI-1-/- mouse (B), and VN-/- mice (C, D).

Morphological Changes in the Carotid Artery After Injury
Figures 4Down and 5Down display the histochemical changes that occur in the carotid arteries of WT mice after injury (similar results were obtained with the PAI-1-/- and VN-/- mice; not shown). For example, Masson’s trichrome stain (Figure 4Down, left column) revealed the formation of an occlusive, platelet-rich thrombus within 30 minutes after injury, progressive accumulation of fibrin in the thrombus (dark red) at 24 hours, and organization of the thrombus at 7 days with disruption of the internal elastic lamina, migration of cells from the medial layers to the intima, and increased cellularity with marked thickening of the adventitia. At 3 weeks, the adventitial reaction to injury had subsided, and the most prominent finding was the presence of a multilayered neointima.



View larger version (131K):
[in this window]
[in a new window]
 
Figure 4. Histochemical studies of carotid arteries at various times after injury. Left column: Masson’s trichrome stain (MTC). Arrow indicates disrupted internal elastic lamina. Middle column: Staining for vWF protein. Arrow indicates endothelial denudation at 7 days. Right column: Perls’ iron stain (blue). Arrow indicates migration of cells through disrupted internal elastic lamina 7 days after injury. Magnification: Top 3 panels of left column, x200; other panels, x1000.



View larger version (79K):
[in this window]
[in a new window]
 
Figure 5. Temporal changes in vascular cells after injury. Immunohistochemical markers were used to study changes in mature SMCs ({alpha}-actin; top row), in dedifferentiated (proliferating/migrating) SMCs (vimentin, Vim; middle row), and in tissue-fixed macrophages (M{phi}; bottom row). Magnification x1000.

By 30 minutes after injury, vWF was diffusely present in the platelet-rich thrombus but absent in the intima (Figure 4Up, middle column). Endothelial denudation persisted at least until the end of the first week, with reendothelialization observed by 3 weeks. Perls’ iron stain (Figure 4Up, right column) revealed that iron accumulated at the interface between the thrombus and the vessel wall at 30 minutes after injury but then was cleared rapidly during the wound-healing process.

FeCl3 injury resulted in the loss of staining for both {alpha}-actin (Figure 5Up, top row) and the cytoskeletal protein vimentin (Figure 5Up, middle row) within 30 minutes, and few, if any, intact cells or cell nuclei could be detected in the media or adventitia. These changes persisted for 24 hours after injury, but by 7 days, marked repopulation of the vessel wall was observed, with some {alpha}-actin–positive cells in the neointima and abundant vimentin-positive cells throughout the vessel wall. These round/globular cells were tentatively identified as proliferating/migrating SMCs.19 Three weeks after injury, multiple layers of redifferentiated, flat, {alpha}-actin–positive SMCs could be detected in the neointima. Although isolated macrophages were detected in the adventitia 7 days after injury (Figure 5Up, bottom row), most had disappeared again by the end of the third week. Proliferation rates (proliferating cell nuclear antigen–stained nuclei; Zymed) in the vessel wall decreased from 13±10% to 7.2±8.1% within 24 hours after injury, then increased dramatically to 55±27% by the end of the first week (P<0.001 versus uninjured vessels), and finally returned to preinjury levels by 3 weeks (5.1±7.7%). The majority of proliferating cells were dedifferentiated migrating SMCs (see Reference 1919 ; not shown).

Changes in PAI-1 and VN Gene Expression in Injured Vessels
RT-PCR revealed relatively low levels of PAI-1 mRNA in the carotid artery before and 30 minutes after injury (Figure 6ADown and 6BDown). Increased PAI-1 mRNA was detected 6 hours after injury, however; it remained relatively high from 1 to 7 days and then returned to baseline levels by 3 weeks. In contrast, little VN mRNA was detected in the normal vessel, and it did not increase at any time after injury (Figure 6CDown and 6DDown). In situ hybridization (Figure 7Down) revealed that in uninjured vessels and at very early times (30 minutes) after injury, PAI-1 mRNA could be detected only within isolated cells ({alpha}-actin–positive; not shown) of the media and adventitia. By 6 hours after injury, some intact endothelial cells (vWF-positive; not shown) and SMCs also began to express PAI-1 mRNA. At 7 days, a strong multifocal signal for PAI-1 mRNA (blue color) was detected in the organizing thrombus and in all layers of the vessel wall (Figures 7Down and 8Down). This pattern was similar to the distribution of PAI-1 antigen (Figure 8Down). The PAI-1 signal was localized predominantly to proliferating/migrating SMCs19 in the media and adventitia. Three weeks after injury, the intensity of the PAI-1 signal decreased in accordance with the PCR findings.



View larger version (21K):
[in this window]
[in a new window]
 
Figure 6. Temporal changes in PAI-1 and VN gene expression after injury. RT-PCR analysis of PAI-1 mRNA levels (A, WT mice; B, VN-/- mice) and of VN mRNA levels (C, WT mice; D, PAI-1-/- mice), calculated as percentage of ß-actin mRNA expression. Bars represent mean±SD of independent pools of carotid arteries (4 to 8 pools per time point). *P<0.01 and **P<0.001 vs uninjured carotid arteries.



View larger version (77K):
[in this window]
[in a new window]
 
Figure 7. Spatial distribution of PAI-1 and VN mRNAs. In situ hybridization studies were performed in sections from mouse carotid vessels at indicated times after injury. Arrows indicate examples of PAI-1 mRNA–positive cells at early times. Magnification x400.



View larger version (100K):
[in this window]
[in a new window]
 
Figure 8. Distribution of PAI-1 and VN in organizing thrombus and vessel wall. In situ hybridization (ISH) and immunohistochemistry (IHC) studies performed 7 days after injury reveal distribution of PAI-1 mRNA (top) and protein (middle) compared with VN protein (bottom). Magnification x1000.

Although VN gene expression could not be detected by in situ hybridization in the carotid wall before (not shown) or after (Figure 7Up) injury, VN antigen was readily detected in the thrombus by 30 minutes after injury (not shown) and in the vessel wall by 6 hours. It remained in the organizing thrombus and in all layers of the vessel wall throughout the wound-healing process (Figure 8Up). Its diffuse immunosignal, however, was distinctly different from the multifocal signal for PAI-1 mRNA and protein.


*    Discussion
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
*Discussion
down arrowReferences
 
Recent studies6 7 8 12 yield contradictory results with regard to the thrombotic response of PAI-1– and VN-deficient mice to vascular injury and thus raise questions about the true effects of PAI-1 and VN on the balance between thrombosis and fibrinolysis in vivo. The data summarized in this report address these inconsistencies. They demonstrate that PAI-1 and VN are both essential for preventing early fibrinolysis and premature thrombus embolization. For example, arterial injury with FeCl3 led to thrombotic occlusion in a significantly lower proportion of PAI-1-/- (70%) compared with WT (92%) mice (Figure 2Up). Moreover, the mean time to thrombosis in vessels that occluded was significantly longer in PAI-1-/- animals, and >30% of the PAI-1-/- vessels were patent within 30 minutes (versus 12% in WT mice). Our results thus confirm and extend the findings of previous studies that reported enhanced endogenous thrombolysis in the absence of PAI-1.7 8 22

VN-deficient mice also exhibited an attenuated thrombotic response to injury (Figures 2Up and 3Up). In this case, the proportion of vessels that initially thrombosed after injury and the mean time to thrombotic occlusion did not differ significantly versus WT mice (Figure 2BUp). A large proportion of the thrombi were unstable, however, and frequently embolized (Figure 3CUp and 3DUp), leading to a high patency rate 30 minutes after injury (Figure 2CUp). This instability may reflect the absence of the stabilizing effect of VN on PAI-1 at the site of arterial injury3 23 or impaired hemostatic function because of a defect in platelet aggregation caused by VN deficiency.10 11 Further studies are needed to clarify this issue.

Our results indicating instability of arterial thrombi in VN-/- mice differ from those of recent studies12 showing shortened times to thrombosis in these mice (ie, <=3.0 minutes). The mouse strains and protocols used to induce arterial injury in the 2 studies were similar, suggesting that the differences might be due to differences in the anesthetics used. To test this hypothesis, we induced carotid artery injury in WT and VN-/- mice after anesthetizing the animals with either 120 mg/kg pentobarbital IP12 or inhaled methoxyflurane according to our protocol. Baseline carotid blood flow was lower in both mouse genotypes under pentobarbital compared with methoxyflurane anesthesia (0.8±0.3 versus 1.5±0.3 mL/min; P=0.002), and the time to thrombotic occlusion after injury was significantly shorter (6.7±0.6 versus 9.5±2.3 minutes; P=0.007). None of the mice, however, whether anesthetized with metofane or pentobarbital, developed occlusive carotid thrombi <=3.0 minutes after injury. It is possible that the carotid vessels were handled more vigorously in the earlier study, and that this, together with the lower flow rate induced by pentobarbital, contributed to the shortened times to occlusion.

The mechanisms underlying the formation of platelet-rich arterial thrombi after application of FeCl3 to the adventitia of the mouse vessel are largely unknown. Iron may injure endothelial cells24 and/or promote platelet activation and thrombosis.25 Whether changes in plasma components, in local gene expression, or in specific proteins and cells also contribute to the vascular remodeling process in this model is similarly unknown. These issues also were addressed in this study. We found that FeCl3 accumulates at the interface between the thrombus and the vessel wall (Figure 4Up), resulting in endothelial denudation and loss of medial SMCs within 30 minutes. The intima, media, and adventitia appeared to be acellular at early times after injury (ie, 30 minutes, 24 hours). By 7 days, however, there was a peak in cellular proliferation (Figures 4Up and 5Up), particularly in the adventitia, and the beginning of cell migration into the media and neointima. The vast majority of the proliferating and migrating cells exhibited characteristics of dedifferentiated SMCs (so-called synthetic phenotype).19 By 3 weeks, reendothelialization, repopulation of the media, and formation of a multilayered, {alpha}-actin–positive neointima had occurred, and the cellular proliferation rate in the vessel wall had returned to preinjury levels. Thus, the temporal response of cells to FeCl3 injury in the mouse resembles that observed in the electrical and the rose bengal injury models.18 26 Cellular proliferation and migration occur earlier after mechanical carotid injury,27 probably because of the absence of severe damage to the medial cells in that model.

Although PAI-1 gene expression was very low in the wall of uninjured mouse carotid vessels, it increased significantly early (6 hours) after injury (Figure 6Up), consistent with previous reports in the rat28 and the rabbit.29 In situ hybridization studies showed that at 6 hours, local PAI-1 synthesis was confined to surviving endothelial cells and SMCs in the injured vascular segment (Figure 7Up). By 7 days, however, dedifferentiated proliferating/migrating SMCs in the organizing thrombus and throughout the vessel wall appeared to synthesize PAI-1 (Figures 7Up and 8Up). PAI-1 gene expression returned to background levels when arterial remodeling was complete (by 3 weeks). The spatial and temporal changes in PAI-1 mRNA and protein expression observed after injury suggest that the inhibitor may play a role in the regulation of cell migration and neointima formation in vivo.30 It remains to be determined, however, whether the extent or the rate of restenosis in this model differs significantly between wild-type and PAI-1–deficient mice. Accelerated neointima formation in PAI-1-/- mice was reported after electrical injury,14 suggesting that PAI-1 may inhibit, or at least retard, excessive thickening of the vessel wall and narrowing of the lumen during the remodeling process. The effects may be different in human atherothrombosis, however, and in models of experimental injury that induce a marked thrombotic response in the vessel (ie, the FeCl3 model). In such instances, earlier and more complete dissolution of the thrombus in the absence of PAI-1 may remove an important stimulus for ongoing cell proliferation and migration and thus actually reduce neointimal thickening.

Finally, our observations revealed an abundance of VN antigen in the thrombus and the vessel wall over the 3-week period after FeCl3-induced injury. The diffuse distribution pattern of VN antigen, the presence of very low levels of VN mRNA, and the absence of upregulation of VN gene expression in the thrombus and vessel wall after injury, however, suggest that the VN protein was derived from plasma and not synthesized locally. This hypothesis is consistent with other reports20 21 31 (see, however, a differing view32 ). As in the case of PAI-1, further studies are necessary to confirm the role of VN in vascular remodeling in vivo. In particular, the possibility that the lack of VN may affect the rate and/or extent of neointima formation after arterial injury with FeCl3 in the mouse needs to be tested.


*    Acknowledgments
 
This work was supported by a grant from Boehringer Ingelheim to Dr Konstantinides, a grant from the Deutsche Forschungsgemeinschaft (German Research Association, DFG Scha 808/1-1) to Dr Schäfer, and NIH grants HL-31950 and HL-47819 to Dr Loskutoff. The authors gratefully acknowledge B. Fay and D. Ginsburg (University of Michigan, Ann Arbor, Mich) for helping us to establish the FeCl3 model.

Received May 2, 2000; revision received July 18, 2000; accepted August 4, 2000.


*    References
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
up arrowDiscussion
*References
 
1. Loskutoff DJ, Samad F. The adipocyte and hemostatic balance in obesity studies of PAI-1. Arterioscler Thromb Vasc Biol. 1998;18:1–6.[Free Full Text]

2. Fay WP, Eitzman DT, Shapiro AD, et al. Platelets inhibit fibrinolysis in vitro by both plasminogen activator inhibitor-1-dependent and -independent mechanisms. Blood. 1994;83:351–356.[Abstract/Free Full Text]

3. Van Meijer M, Pannekoek H. Structure of plasminogen activator inhibitor 1 (PAI-1) and its function in fibrinolysis: an update. Fibrinolysis. 1995;9:263–276.

4. Hamsten A, De Faire U, Walldius G, et al. Plasminogen activator inhibitor in plasma: risk factor for recurrent myocardial infarction. Lancet. 1987;2:3–9.[Medline] [Order article via Infotrieve]

5. Carmeliet P, Stassen JM, Schoonjans L, et al. Plasminogen activator inhibitor-1 gene-deficient mice, II: effects on hemostasis, thrombosis, and thrombolysis. J Clin Invest. 1993;92:2756–2760.

6. Farrehi PM, Ozaki CK, Carmeliet P, et al. Regulation of arterial thrombolysis by plasminogen activator inhibitor-1 in mice. Circulation. 1998;97:1002–1008.[Abstract/Free Full Text]

7. Matsuno H, Kozawa O, Niwa M, et al. Differential role of components of the fibrinolytic system in the formation and removal of thrombus induced by endothelial injury. Thromb Haemost. 1999;81:601–604.[Medline] [Order article via Infotrieve]

8. Eitzman DT, Westrick RJ, Nabel EG, et al. Plasminogen activator inhibitor-1 and vitronectin promote vascular thrombosis in mice. Blood. 2000;95:577–580.[Abstract/Free Full Text]

9. Loskutoff DJ, Curriden SA, Hu G, et al. Regulation of cell adhesion by PAI-1. APMIS. 1999;107:54–61.[Medline] [Order article via Infotrieve]

10. Preissner KT, Seiffert D. Role of vitronectin and its receptor in haemostasis and vascular remodeling. Thromb Res. 1998;89:1–21.[Medline] [Order article via Infotrieve]

11. Asch E, Podack E. Vitronectin binds to activated human platelets and plays a role in platelet aggregation. J Clin Invest. 1990;85:1372–1378.

12. Fay WP, Parker AC, Ansari MN, et al. Vitronectin inhibits the thrombotic response to arterial injury in mice. Blood. 1999;93:1825–1830.[Abstract/Free Full Text]

13. Chapman HA. Plasminogen activators, integrins, and the coordinated regulation of cell adhesion and migration. Curr Opin Cell Biol. 1997;9:714–724.[Medline] [Order article via Infotrieve]

14. Carmeliet P, Moons L, Lijnen R, et al. Inhibitory role of plasminogen activator inhibitor-1 in arterial wound healing and neointima formation: a gene targeting and gene transfer study in mice. Circulation. 1997;96:3180–3191.[Abstract/Free Full Text]

15. Kurz KD, Main BW, Sandusky GE. Rat model of arterial thrombosis induced by ferric chloride. Thromb Res. 1990;60:269–280.[Medline] [Order article via Infotrieve]

16. Zheng X, Saunders TL, Camper SA, et al. Vitronectin is not essential for normal mammalian development and fertility. Proc Natl Acad Sci U S A. 1995;92:12426–12430.[Abstract/Free Full Text]

17. Yamamoto K, Loskutoff DJ. Fibrin deposition in tissues from endotoxin-treated mice correlates with decreases in the expression of urokinase-type but not tissue-type plasminogen activator. J Clin Invest. 1996;97:2440–2451.[Medline] [Order article via Infotrieve]

18. Carmeliet P, Moons L, Stassen J-M, et al. Vascular wound healing and neointima formation induced by perivascular electric injury in mice. Am J Pathol. 1997;150:761–776.[Abstract]

19. Kocher O, Gabbiani F, Gabbiani G, et al. Phenotypic features of smooth muscle cells during the evolution of experimental carotid artery intimal thickening. Lab Invest. 1991;65:459–470.[Medline] [Order article via Infotrieve]

20. Van Aken BE, Seiffert D, Thinnes T, et al. Localization of vitronectin in the normal and atherosclerotic human vessel wall. Histochem Cell Biol. 1997;107:313–320.[Medline] [Order article via Infotrieve]

21. Seiffert D, Keeton M, Eguchi Y, et al. Detection of vitronectin mRNA in tissues and cells of the mouse. Proc Natl Acad Sci U S A. 1991;88:9402–9406.[Abstract/Free Full Text]

22. Biemond BJ, Levi M, Coronel R, et al. Thrombolysis and reocclusion in experimental jugular vein and coronary artery thrombosis: effects of a plasminogen activator inhibitor type 1–neutralizing monoclonal antibody. Circulation. 1995;91:1175–1181.[Abstract/Free Full Text]

23. Deng G, Royle G, Seiffert D, et al. The PAI-1/vitronectin interaction: two cats in a bag? Thromb Haemost. 1995;74:66–70.[Medline] [Order article via Infotrieve]

24. Balla G, Vercellotti GM, Eaton JW, et al. Iron loading of endothelial cells augments oxidant damage. J Lab Clin Med. 1990;116:546–554.[Medline] [Order article via Infotrieve]

25. Praticò D, Pasin M, Barry OP, et al. Iron-dependent human platelet activation and hydroxyl radical formation: involvement of protein kinase C. Circulation. 1999;99:3118–3124.[Abstract/Free Full Text]

26. Kikuchi S, Umemura K, Kondo K, et al. Photochemically induced endothelial injury in the mouse as a screening model for inhibitors of vascular intimal thickening. Arterioscler Thromb Vasc Biol. 1998;18:1069–1078.[Abstract/Free Full Text]

27. Lindner V, Fingerle J, Reidy M. Mouse model of arterial injury. Circ Res. 1993;73:792–796.[Abstract/Free Full Text]

28. Hasenstab D, Forough R, Clowes AW. Plasminogen activator inhibitor type 1 and tissue inhibitor of metalloproteinases-2 increase after arterial injury in rats. Circ Res. 1997;80:490–496.[Abstract/Free Full Text]

29. Sawa H, Lundgren C, Sobel BE, et al. Increased intramural expression of plasminogen activator inhibitor type 1 after balloon injury: a potential progenitor of restenosis. J Am Coll Cardiol. 1994;24:1742–1748.[Abstract]

30. Loskutoff DJ. PAI-1 inhibits neointimal formation after arterial injury in mice: a new target for controlling restenosis? Circulation. 1997;96:2772–2774.

31. Robbie LA, Booth NA, Brown PAJ, et al. Inhibitors of fibrinolysis are elevated in atherosclerotic plaque. Arterioscler Thromb Vasc Biol. 1996;16:539–545.[Abstract/Free Full Text]

32. Dufourcq P, Louis H, Moreau C, et al. Vitronectin expression and interaction with receptors in smooth muscle cells from human atheromatous plaque. Arterioscler Thromb Vasc Biol. 1998;18:168–176.[Abstract/Free Full Text]




This article has been cited by other articles:


Home page
BloodHome page
A. J. Ablooglu, J. Kang, B. G. Petrich, M. H. Ginsberg, and S. J. Shattil
Antithrombotic effects of targeting {alpha}IIb{beta}3 signaling in platelets
Blood, April 9, 2009; 113(15): 3585 - 3592.
[Abstract] [Full Text] [PDF]


Home page
Circ. Res.Home page
M. R. Schroeter, M. Leifheit, P. Sudholt, N.-M. Heida, C. Dellas, I. Rohm, F. Alves, M. Zientkowska, S. Rafail, M. Puls, et al.
Leptin Enhances the Recruitment of Endothelial Progenitor Cells Into Neointimal Lesions After Vascular Injury by Promoting Integrin-Mediated Adhesion
Circ. Res., August 29, 2008; 103(5): 536 - 544.
[Abstract] [Full Text] [PDF]


Home page
StrokeHome page
D. C. Lelong, I. Bieche, E. Perez, K. Bigot, J. Leemput, I. Laurendeau, M. Vidaud, J.-P. Jais, M. Menasche, and M. Abitbol
Novel Mouse Model of Monocular Amaurosis Fugax
Stroke, December 1, 2007; 38(12): 3237 - 3244.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
P. F. Bodary
Links Between Adipose Tissue and Thrombosis in the Mouse
Arterioscler. Thromb. Vasc. Biol., November 1, 2007; 27(11): 2284 - 2291.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
R. J. Westrick, M. E. Winn, and D. T. Eitzman
Murine Models of Vascular Thrombosis
Arterioscler. Thromb. Vasc. Biol., October 1, 2007; 27(10): 2079 - 2093.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
W. P. Fay, N. Garg, and M. Sunkar
Vascular Functions of the Plasminogen Activation System
Arterioscler. Thromb. Vasc. Biol., June 1, 2007; 27(6): 1231 - 1237.
[Abstract] [Full Text] [PDF]


Home page
Circ. Res.Home page
U. J.H. Sachs and B. Nieswandt
In Vivo Thrombus Formation in Murine Models
Circ. Res., April 13, 2007; 100(7): 979 - 991.
[Abstract] [Full Text] [PDF]


Home page
Proc. Natl. Acad. Sci. USAHome page
C. Kannemeier, A. Shibamiya, F. Nakazawa, H. Trusheim, C. Ruppert, P. Markart, Y. Song, E. Tzima, E. Kennerknecht, M. Niepmann, et al.
Extracellular RNA constitutes a natural procoagulant cofactor in blood coagulation
PNAS, April 10, 2007; 104(15): 6388 - 6393.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
C. V. Denis and D. D. Wagner
Platelet Adhesion Receptors and Their Ligands in Mouse Models of Thrombosis
Arterioscler. Thromb. Vasc. Biol., April 1, 2007; 27(4): 728 - 739.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
K. Schafer, M. R. Schroeter, C. Dellas, M. Puls, M. Nitsche, E. Weiss, G. Hasenfuss, and S. V. Konstantinides
Plasminogen Activator Inhibitor-1 From Bone Marrow-Derived Cells Suppresses Neointimal Formation After Vascular Injury in Mice
Arterioscler. Thromb. Vasc. Biol., June 1, 2006; 26(6): 1254 - 1259.
[Abstract] [Full Text] [PDF]


Home page
Eur Heart JHome page
T. Raupach, K. Schafer, S. Konstantinides, and S. Andreas
Secondhand smoke as an acute threat for the cardiovascular system: a change in paradigm
Eur. Heart J., February 2, 2006; 27(4): 386 - 392.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
M. J. Heeb, K. M. Cabral, and L. Ruan
Down-regulation of Factor IXa in the Factor Xase Complex by Protein Z-dependent Protease Inhibitor
J. Biol. Chem., October 7, 2005; 280(40): 33819 - 33825.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Pathol.Home page
L. Campagnolo, A. Leahy, S. Chitnis, S. Koschnick, M. J. Fitch, J. T. Fallon, D. Loskutoff, M. B. Taubman, and H. Stuhlmann
EGFL7 Is a Chemoattractant for Endothelial Cells and Is Up-Regulated in Angiogenesis and Arterial Injury
Am. J. Pathol., July 1, 2005; 167(1): 275 - 284.
[Abstract] [Full Text] [PDF]


Home page
J Am Coll CardiolHome page
S. Yokoyama, H. Ikeda, N. Haramaki, H. Yasukawa, T. Murohara, and T. Imaizumi
Platelet P-selectin plays an important role in arterial thrombogenesis by forming large stable platelet-leukocyte aggregates
J. Am. Coll. Cardiol., April 19, 2005; 45(8): 1280 - 1286.
[Abstract] [Full Text] [PDF]


Home page
CLIN APPL THROMB HEMOSTHome page
H. Ekmekci, O. B. Ekmekci, H. Sonmez, Z. Ozturk, N. Domanic, and E. Kokoglu
Evaluation of Fibronectin, Vitronectin, and Leptin Levels in Coronary Artery Disease: Impacts on Thrombosis and Thrombolysis
Clinical and Applied Thrombosis/Hemostasis, January 1, 2005; 11(1): 63 - 70.
[Abstract] [PDF]


Home page
BloodHome page
H. Brogren, L. Karlsson, M. Andersson, L. Wang, D. Erlinge, and S. Jern
Platelets synthesize large amounts of active plasminogen activator inhibitor 1
Blood, December 15, 2004; 104(13): 3943 - 3948.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
S. Konstantinides, K. Schafer, J. G. Neels, C. Dellas, and D. J. Loskutoff
Inhibition of Endogenous Leptin Protects Mice From Arterial and Venous Thrombosis
Arterioscler. Thromb. Vasc. Biol., November 1, 2004; 24(11): 2196 - 2201.
[Abstract] [Full Text] [PDF]


Home page
BloodHome page
Y.-P. Wu, H. J. Bloemendal, E. E. Voest, T. Logtenberg, P. G. de Groot, M. F. B. G. Gebbink, and H. C. de Boer
Fibrin-incorporated vitronectin is involved in platelet adhesion and thrombus formation through homotypic interactions with platelet-associated vitronectin
Blood, August 15, 2004; 104(4): 1034 - 1041.
[Abstract] [Full Text] [PDF]


Home page
Cardiovasc ResHome page
C Roncal, J Orbe, J.A Rodriguez, M Belzunce, O Beloqui, J Diez, and J.A Paramo
Influence of the 4G/5G PAI-1 genotype on angiotensin II-stimulated human endothelial cells and in patients with hypertension
Cardiovasc Res, July 1, 2004; 63(1): 176 - 185.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
K. Schafer, K. Muller, A. Hecke, E. Mounier, J. Goebel, D. J. Loskutoff, and S. Konstantinides
Enhanced Thrombosis in Atherosclerosis-Prone Mice Is Associated With Increased Arterial Expression of Plasminogen Activator Inhibitor-1
Arterioscler. Thromb. Vasc. Biol., November 1, 2003; 23(11): 2097 - 2103.
[Abstract] [Full Text] [PDF]


Home page
Proc. Natl. Acad. Sci. USAHome page
H. Ni, P. S. T. Yuen, J. M. Papalia, J. E. Trevithick, T. Sakai, R. Fassler, R. O. Hynes, and D. D. Wagner
Plasma fibronectin promotes thrombus growth and stability in injured arterioles
PNAS, March 4, 2003; 100(5): 2415 - 2419.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
S. Konstantinides, K. Schafer, and D. J. Loskutoff
Do PAI-1 and Vitronectin Promote or Inhibit Neointima Formation?: The Exact Role of the Fibrinolytic System in Vascular Remodeling Remains Uncertain
Arterioscler. Thromb. Vasc. Biol., December 1, 2002; 22(12): 1943 - 1945.
[Full Text] [PDF]


Home page
CirculationHome page
K. Schafer, S. Konstantinides, C. Riedel, T. Thinnes, K. Muller, C. Dellas, G. Hasenfuss, and D. J. Loskutoff
Different Mechanisms of Increased Luminal Stenosis After Arterial Injury in Mice Deficient for Urokinase- or Tissue-Type Plasminogen Activator
Circulation, October 1, 2002; 106(14): 1847 - 1852.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. Chavakis, R. A. Pixley, I. Isordia-Salas, R. W. Colman, and K. T. Preissner
A Novel Antithrombotic Role for High Molecular Weight Kininogen as Inhibitor of Plasminogen Activator Inhibitor-1 Function
J. Biol. Chem., August 30, 2002; 277(36): 32677 - 32682.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. Chavakis, N. Boeckel, S. Santoso, R. Voss, I. Isordia-Salas, R. A. Pixley, E. Morgenstern, R. W. Colman, and K. T. Preissner
Inhibition of Platelet Adhesion and Aggregation by a Defined Region (Gly-486-Lys-502) of High Molecular Weight Kininogen
J. Biol. Chem., June 21, 2002; 277(26): 23157 - 23164.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
L. Peng, N. Bhatia, A. C. Parker, Y. Zhu, and W. P. Fay
Endogenous Vitronectin and Plasminogen Activator Inhibitor-1 Promote Neointima Formation in Murine Carotid Arteries
Arterioscler. Thromb. Vasc. Biol., June 1, 2002; 22(6): 934 - 939.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
J.-C. Murciano, D. Harshaw, D. G. Neschis, L. Koniaris, K. Bdeir, S. Medinilla, A. B. Fisher, M. A. Golden, D. B. Cines, M. T. Nakada, et al.
Platelets inhibit the lysis of pulmonary microemboli
Am J Physiol Lung Cell Mol Physiol, March 1, 2002; 282(3): L529 - L539.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. J. Podor, S. Campbell, P. Chindemi, D. M. Foulon, D. H. Farrell, P. D. Walton, J. I. Weitz, and C. B. Peterson
Incorporation of Vitronectin into Fibrin Clots. EVIDENCE FOR A BINDING INTERACTION BETWEEN VITRONECTIN AND gamma A/gamma ' FIBRINOGEN
J. Biol. Chem., February 22, 2002; 277(9): 7520 - 7528.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. J. Podor, D. Singh, P. Chindemi, D. M. Foulon, R. McKelvie, J. I. Weitz, R. Austin, G. Boudreau, and R. Davies
Vimentin Exposed on Activated Platelets and Platelet Microparticles Localizes Vitronectin and Plasminogen Activator Inhibitor Complexes on Their Surface
J. Biol. Chem., February 22, 2002; 277(9): 7529 - 7539.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
M. Cattaruzza, K. Schafer, and M. Hecker
Cytokine-induced Down-regulation of zfm1/Splicing Factor-1 Promotes Smooth Muscle Cell Proliferation
J. Biol. Chem., February 15, 2002; 277(8): 6582 - 6589.
[Abstract] [Full Text] [PDF]


This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Konstantinides, S.
Right arrow Articles by Loskutoff, D. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Konstantinides, S.
Right arrow Articles by Loskutoff, D. J.
Related Collections
Right arrow Animal models of human disease
Right arrow Genetically altered mice
Right arrow Physiological and pathological control of gene expression
Right arrow Arterial thrombosis
Right arrow Coagulation and fibronolysis
Right arrow Other Vascular biology