Plasmin inhibition increases MMP-9 activity and decreases vein wall stiffness during venous thrombosis resolution

Role of platelet count in a murine stasis model of deep vein thrombosis

Platelets are core components of thrombi but their effect on thrombus burden during deep vein thrombosis (DVT) has not been fully characterized. We examined the role of thrombopoietin-altered platelet count on thrombus burden in a murine stasis model of DVT. To modulate platelet count compared to baseline, CD1 mice were pretreated with thrombopoietin antisense oligonucleotide (THPO-ASO, 56% decrease), thrombopoietin mimetic (TPO-mimetic, 36% increase), or saline (within 1%). Thrombi and vein walls were examined on postoperative days (POD) 3 and 7. Thrombus weights on POD 3 were not different between treatment groups (p = .84). The mean thrombus weights on POD 7 were significantly increased in the TPO-mimetic cohort compared to the THPO-ASO (p = .005) and the saline (p = .012) cohorts. Histological grading at POD 3 revealed a significantly increased smooth muscle cell presence in the thrombi and CD31 positive channeling in the vein wall of the TPO-mimetic cohort compared to the saline and THPO-ASO cohorts (p < .05). No differences were observed in histology on POD 7. Thrombopoietin-induced increased platelet count increased thrombus weight on POD 7 indicating platelet count may regulate thrombus burden during early resolution of venous thrombi in this murine stasis model of DVT.

Acute T2*-Weighted Magnetic Resonance Imaging Detectable Cerebral Thrombosis in a Rat Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is associated with a high incidence of morbidity and mortality, particularly within the first 72 h after aneurysm rupture. We recently found ultra-early cerebral thrombosis, detectable on T2* magnetic resonance imaging (MRI), in a mouse SAH model at 4 h after onset. The current study examined whether such changes also occur in rat at 24 h after SAH, the vessels involved, whether the degree of thrombosis varied with SAH severity and brain injury, and if it differed between male and female rats. Adult Sprague Dawley rats were subjected to an endovascular perforation SAH model or sham surgery and underwent T2 and T2* MRI 24 h later. Following SAH, increased numbers of T2* hypointense vessels were detected on MRI. The number of such vessels correlated with SAH severity, as assessed by MRI-based grading of bleeding. Histologically, thrombotic vessels were found on hematoxylin and eosin staining, had a single layer of smooth muscle cells on alpha-smooth muscle actin immunostaining, and had laminin 2α/fibrinogen double labeling, suggesting venule thrombosis underlies the T2*-positive vessels on MRI. Capillary thrombosis was also detected which may follow the venous thrombosis. In both male and female rats, the number of T2*-positive thrombotic vessels correlated with T2 lesion volume and neurological function, and the number of such vessels was significantly greater in female rats. In summary, this study identified cerebral venous thrombosis 24 h following SAH in rats that could be detected with T2* MRI imaging and may contribute to SAH-induced brain injury.

A whole blood thrombus mimic: Constitutive behavior under simple shear

Deep vein thrombosis and pulmonary embolism affect 300,000-600,000 patients each year in the US. To better understand the highly mechanical pathophysiology of pulmonary embolism, we set out to develop an in-vitro thrombus mimic and to test this mimic under large deformation simple shear. In addition to reporting on the mechanics of our mimics under simple shear, we explore the sensitivity of their mechanics to coagulation conditions and blood storage time, and compare three hyperelastic material models for their ability to fit our data. We found that thrombus mimics made from whole blood demonstrate strain-stiffening, a negative Poynting effect, and hysteresis when tested quasi-statically to 50% strain under simple shear. Additionally, we found that the stiffness of these mimics does not significantly vary with coagulation conditions or blood storage times. Of the three hyperelastic constitutive models that we tested, the Ogden model provided the best fits to both shear stress and normal stress. In conclusion, we developed a robust protocol to generate regularly-shaped, homogeneous thrombus mimics that lend themselves to simple shear testing under large deformation. Future studies will extend our model to include the effect of maturation and explore its fracture properties toward a better understanding of embolization.

Mechanical Properties of Diseased Veins

Extensive research exists on arterial mechanical properties and how they change in disease conditions, but substantially less is known about venous mechanics in healthy and disease states. Although the mechanics of both vessel types are determined by the unique layered composition of the vessel wall, the precise distribution of the layers differs greatly between arteries and veins. Thus, vein mechanics must be analyzed and understood independently from those of arteries. This review discusses the compositional attributes that are unique to veins, how these attributes contribute to venous mechanics, and the alterations that occur to both composition and material properties during venous thrombosis and insufficiency. In general, changes to the venous wall during thrombosis increase wall stiffness and decrease extensibility. During venous insufficiency, however, both the stiffness and the extensibility of the venous wall decrease. Characterizing these changes is essential to better understand disease progression and build vein-specific devices for treating venous disease.

Long non-coding RNA LUCAT1 promotes tumourigenesis by inhibiting ANXA2 phosphorylation in hepatocellular carcinoma

Long non‐coding RNAs (lncRNAs) play essential roles in diverse biological processes; however, current understanding of the mechanism underlying the regulation of tumour proliferation and metastasis is limited. Lung cancer‐associated transcript 1 (LUCAT1) has been reported in a variety of human cancers, while its role in hepatocellular carcinoma (HCC) remains unclear. This study aimed to determine the biological role and underlying mechanism of LUCAT1 on progression and metastasis in HCC cells and clinical specimens. Our results demonstrated that LUCAT1 was up‐regulated in HCC tissues and cells. Loss‐ and gain‐of‐function studies revealed that LUCAT1 promotes the proliferation and metastasis of HCC cells in vitro and in vivo. Furthermore, RNA pulldown and Western blot assays indicated that LUCAT1 inhibited the phosphorylation of Annexin A2 (ANXA2) to reduce the degradation of ANXA2‐S100A10 heterotetramer (AIIt), which in turn accelerated the secretion of plasminogen into plasmin, thereby resulting in the activation of metalloprotease proteins. In conclusion, we propose that LUCAT1 serves as a novel diagnostic and therapeutic target for HCC.

Animal models of venous thrombosis

Venous thrombosis (VT) is a prevalent clinical condition with significant adverse sequela or mortality. Anticoagulation and pharmacologic or pharmacomechanical thrombolytic therapies are the mainstays of VT treatment. An understanding of thrombosis biology will allow for more effective VT-tailored diagnosis and therapy. In vivo models of thrombosis provide indispensable tools to study the pathogenesis of thrombus formation and to evaluate novel therapeutic or preventive adjuncts for VT management or prevention. In this article, we review the most prominent in vivo models of VT created in rodents and swine species and outline how each model can serve as a useful tool to promote our understanding of VT pathogenesis and to examine novel therapies.

Rivaroxaban attenuates thrombosis by targeting the NF-κB signaling pathway in a rat model of deep venous thrombus

Anticoagulant therapy is commonly used for the prevention and treatment of patients with deep venous thrombus. Evidence has shown that rivaroxaban is a potential oral anticoagulant drug for the acute treatment of venous thromboembolism. However, the rivaroxaban-mediated molecular mechanism involved in the progression of deep venous thrombosis has not been investigated. In the present study, we investigated the efficacy of rivaroxaban and the underlying signaling pathways in the prevention and treatment of rats with deep venous thrombosis. A rat model with deep vein thrombus formation was established and received treatment with rivaroxaban or PBS as control. The thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor-1 (PAI-1) were analyzed both in vitro and in vivo. The progression of thrombosis and stroke was evaluated after treatment with rivaroxaban or PBS. Nuclear factor-κB (NF-κB) signaling pathway in venous endothelial cells and in the rat model of deep venous thrombus was assessed. The therapeutic effects of rivaroxaban were evaluated as determined by changes in deep venous thrombosis in the rat model. Our results showed that rivaroxaban markedly inhibited TAFI and PAI-1 expression levels, neutrophils, tissue factor, neutrophil extracellular traps (NETs), myeloperoxidase and macrophages in venous endothelial cells and in the rat model of deep venous thrombus. Expression levels of ADP, PAIs, von Willebrand factor (vWF) and thromboxane were downregulated in vein endothelial cells and in serum from the experimental rats. Importantly, the incidences of inferior vena cava filter thrombus were protected by rivaroxaban during heparin-induced thrombolysis deep venous thrombosis in the rat model. We observed that activity of the NF-κB signaling pathway was inhibited by rivaroxaban in vein endothelial cells both in vitro and in vivo. Notably, immunohistology indicated that rivaroxaban attenuated deep venous thrombosis and the accumulation of inflammatory factors in the lesions in venous thrombus. Matrix metalloproteinase (MMP) expression and activity were downregulated in rivaroxaban-treated rats with deep venous thrombus. Rivaroxaban inhibited the elasticity of the extracellular matrix and collagen-elastin fibers. On the whole, these results indicate that rivaroxaban attenuates deep venous thrombus through MMP-9-mediated NF-κB signaling pathway.

Danhong huayu koufuye prevents deep vein thrombosis through anti-inflammation in rats

BACKGROUND

Danhong huayu koufuye (DHK) has traditionally been used clinically for a long time in China. This study was to evaluate the effect of DHK in treating deep vein thrombosis (DVT) in rats and explore its possible mechanism.

METHODS

Forty-eight Sprague-Dawley rats were divided into four groups, performed with incomplete inferior vena cava ligation to induce DVT, and orally administered with DHK (3.20 mg/kg/d), warfarin (2.00 mg/kg/d), or vehicle for 7 days. The involved inferior vena cava and thrombi were collected and measured in size. The tissue specimens were performed for routine histopathologic evaluation and immunohistochemical staining with tissue factor and matrix metalloproteinases-9. Blood samples were collected for detecting coagulation function, blood cell count, and the levels of interleukin-6 and tumor necrosis factor-α.

RESULTS

The treatment of DHK markedly reduced the size of thrombi by 49.26%, and the vein wall thickness by 47.86%. The recanalization rate was significant higher in the DHK-treated group than the vehicle-treated group (26.34 ± 6.53% versus 15.91 ± 3.93%, P < 0.01). Comparing to vehicle control, DHK significantly reduced neutrophils (P < 0.05) and lymphocytes (P < 0.05), serum tumor necrosis factor-α level (4.90 ± 1.14 pg/mL versus 6.60 ± 1.62 pg/mL, P < 0.01), and the expression of matrix metalloproteinases-9 and tissue factor (P < 0.05) in thrombi.

CONCLUSIONS

DHK effectively prevented DVT through anti-inflammatory action in rats.

Matrix Metalloproteinase 9 (MMP-9) Regulates Vein Wall Biomechanics in Murine Thrombus Resolution

Objective

Deep venous thrombosis is a common vascular problem with long-term complications including post-thrombotic syndrome. Post-thrombotic syndrome consists of leg pain, swelling and ulceration that is related to incomplete or maladaptive resolution of the venous thrombus as well as loss of compliance of the vein wall. We examine the role of metalloproteinase-9 (MMP-9), a gene important in extracellular remodeling in other vascular diseases, in mediating thrombus resolution and biomechanical changes of the vein wall.

Methods and Results

The effects of targeted deletion of MMP-9 were studied in an in vivo murine model of thrombus resolution using the FVB strain of mice. MMP-9 expression and activity significantly increased on day 3 after DVT. The lack of MMP-9 impaired thrombus resolution by 27% and this phenotype was rescued by the transplantation of wildtype bone marrow cells. Using novel biomechanical techniques, we demonstrated that the lack of MMP-9 significantly decreased thrombus-induced loss of vein wall compliance. Biomechanical analysis of the contribution of individual structural components showed that MMP-9 affected the elasticity of the extracellular matrix and collagen-elastin fibers. Biochemical and histological analyses correlated with these biomechanical effects as thrombi of mice lacking MMP-9 had significantly fewer macrophages and collagen as compared to those of wildtype mice.

Conclusions

MMP-9 mediates thrombus-induced loss of vein wall compliance by increasing stiffness of the extracellular matrix and collagen-elastin fibers during thrombus resolution. MMP-9 also mediates macrophage and collagen content of the resolving thrombus and bone-marrow derived MMP-9 plays a role in resolution of thrombus mass. These disparate effects of MMP-9 on various aspects of thrombus illustrate the complexity of individual protease function on biomechanical and morphometric aspects of thrombus resolution.

Divergent effects of Tlr9 deletion in experimental late venous thrombosis resolution and vein wall injury

Deep-vein thrombosis (DVT) resolves via a sterile inflammatory response. Defining the inflammatory response of DVT may allow for new therapies that do not involve anticoagulation. Previously, we have shown that Toll-like receptor 9 (Tlr9) gene deleted mice had impaired venous thrombosis (VT) resolution. Here, we further characterise the role of Tlr9 signalling and sterile inflammation in chronic VT and vein wall responses. First, we found a human precedent exists with Tlr9+ cells present in chronic post thrombotic intraluminal tissue. Second, in a stasis VT mouse model, endogenous danger signal mediators of uric acid, HMGB-1, and neutrophil extracellular traps marker of citrullinated histone-3 (and extracellular DNA) were greater in Tlr9-/- thrombi as compared with wild-type (WT), corresponding with larger VT at 8 and 21 days. Fewer M1 type (CCR2+) monocyte/macrophages (MØ) were present in Tlr9-/- thrombi than WT controls at 8 days, suggesting an impaired inflammatory cell influx. Using bone marrow-derived monocyte (BMMØ) cell culture, we found decreased fibrinolytic gene expression with exposure to several endogenous danger signals. Next, adoptive transfer of cultured Tlr9+/+ BMMØ to Tlr9-/- mice normalised VT resolution at 8 days. Lastly, although the VT size was larger at 21 days in Tlr9-/- mice and correlated with decreased endothelial antigen markers, no difference in fibrosis was found. These data suggest that Tlr9 signalling in MØ is critical for later VT resolution, is associated with necrosis clearance, but does not affect later vein wall fibrosis. These findings provide insight into the Tlr9 MØ mechanisms of sterile inflammation in this disease process.

Recanalization and flow regulate venous thrombus resolution and matrix metalloproteinase expression in vivo

OBJECTIVE

We examined the role of thrombus recanalization and ongoing blood flow in the process of thrombus resolution by comparing two murine in vivo models of deep venous thrombosis.

METHODS

In CD1 mice, we performed surgical inferior vena cava ligation (stasis thrombosis), stenosis (thrombosis with recanalization), or sham procedure. We analyzed thrombus weight over time as a measure of thrombus resolution and quantified the messenger RNA and protein levels of membrane-type matrix metalloproteinases (MT-MMPs) as well as effectors of the plasmin complex at days 4, 8, and 12 after surgery.

RESULTS

Despite similar initial thrombus size, the presence of ongoing blood flow (stenosis model) was associated with a 45.91% subsequent improvement in thrombus resolution at day 8 and 12.57% at day 12 compared with stasis thrombosis (ligation model). Immunoblot and real-time polymerase chain reaction analysis demonstrated a difference in MMP-2 and MMP-9 activity at day 8 between the two models (P = .03 and P = .006, respectively) as well as a difference in MT2-MMP gene expression at day 8 (P = .044) and day 12 (P = .03) and MT1-MMP protein expression at day 4 (P = .021). Histologic analyses revealed distinct areas of recanalization in the thrombi of the stenosis model compared with the ligation model as well as the recruitment of inflammatory cells, especially macrophages, and a focal pattern of localized expression of MT1-MMP and MT3-MMP proteins surrounding the areas of recanalization in the stenosis model.

CONCLUSIONS

Recanalization and ongoing blood flow accelerate deep venous thrombus resolution in vivo and are associated with distinct patterns of MT1-MMP and MT3-MMP expression and macrophage localization in areas of intrathrombus recanalization.

The effect of matrix metalloproteinase 2 and matrix metalloproteinase 2/9 deletion in experimental post-thrombotic vein wall remodeling

BACKGROUND

Vein wall fibrotic injury following deep venous thrombosis (VT) is associated with elevated matrix metalloproteinases (MMPs). Whether and by what mechanism MMP2 contributes to vein wall remodeling after VT is unknown.

METHODS

Stasis VT was produced by ligation of the inferior vena cava and tissue was harvested at 2, 8, and 21 days in MMP2 -/- and genetic wild type (WT) mice. Tissue analysis by immunohistochemistry, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and zymography was performed.

RESULTS

Thrombus resolution was less at 8 days in MMP2 -/- compared with WT, evidenced by a 51% increase in VT size (P < .01), and threefold fewer von Willebrand's factor positive channels (P < .05). In MMP2 -/- mice, the main phenotypic fibrotic differences occurred at 8 days post-VT, with significantly less vein wall collagen content (P = .013), fourfold lower procollagen III gene expression (P < .01), but no difference in procollagen I compared with WT. Decreased inflammation in MMP2 -/- vein walls was suggested by ∼ threefold reduced TNFα and IL-1β at 2 days and 8 days post-VT (P < .05). A fourfold increase in vein wall monocytes (P = .03) with threefold decreased apoptosis (P < .05), but no difference in cellular proliferation at 8 days was found in MMP2 -/- compared with WT. As increased compensatory MMP9 activity was observed in the MMP2 -/-mice, MMP2/9 double null mice had thrombus induced with VT harvest at 8 days. Consistently, twofold larger VT, a threefold decrease in vein wall collagen, and a threefold increase in monocytes were found (all P < .05). Similar findings were observed in MMP9 -/- mice administered an exogenous MMP2 inhibitor.

CONCLUSIONS

In stasis VT, deletion of MMP2 was associated with less midterm vein wall fibrosis and inflammation, despite an increase in monocytes. Consideration that VT resolution was impaired with MMP2 (and MMP2/9) deletion suggests direct inhibition will likely also require anticoagulant therapy.

Matrix metalloproteinase-9 deletion is associated with decreased mid-term vein wall fibrosis in experimental stasis DVT

INTRODUCTION

Post thrombotic syndrome therapy is primarily palliative, and the associated vein wall inflammatory mechanisms are unclear. Vein wall fibrotic injury following deep venous thrombosis (VT) is associated with elevated matrix metalloproteinases (MMPs). Whether and by what mechanism MMP9 directly contributes to vein wall remodeling after VT is unknown.

METHODS

WT and MMP9 -/- mice underwent stasis VT by ligation of the inferior vena cava (IVC) and tissue was harvested at 2, 8, and 21days. Assessment of thrombus size, and gene, protein and structural vein wall determinations were done.

RESULTS

VT resolution was increased in MMP9-/- mice as compared with controls at 21d only. The primary phenotypic fibrotic vein wall differences occurred at 8d post VT, with significantly less vein wall collagen content as assessed by Picosirius red staining in MMP9 -/- mice as compared with WT. Increased monocytic vein wall influx with less IL-1b and TGFb was found in MMP9 -/- vein walls as compared with WT. Corresponding levels of PAI-1 were increased in MMP9 -/- compared with WT, and no difference in FSP-1+cells as compared with controls.

CONCLUSIONS

In stasis VT, MMP9 modulates midterm vein wall collagen content, with an altered local inflammatory and profibrotic environment, likely directed by monocytes. Thus, MMP9 plays a role in both vein wall responses as well as late thrombus resolution.

The role of urokinase plasminogen activator and plasmin activator inhibitor-1 on vein wall remodeling in experimental deep vein thrombosis

OBJECTIVE

Deep vein thrombosis (DVT) resolution instigates an inflammatory response, resulting in vessel wall damage and scarring. Urokinase-plasminogen activator (uPA) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), are integral components of the fibrinolytic system, essential for venous thrombosis (VT) resolution. This study determined the vein wall response when exposed to increased and decreased plasmin activity.

METHODS

A mouse inferior vena cava (IVC) ligation model in uPA -/- or PAI-1 -/- and their genetic wild types (B6/SvEv and C57/BL6, respectively) was used to create stasis thrombi, with tissue harvest at either 8 or 21 days. Tissue analysis included gene expression of vascular smooth muscle cells (alpha smooth muscle actin [αSMA], SM22) and endothelial marker (CD31), by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, matrix metalloproteinase (MMP)-2 and -9 activity by zymography, and vein wall collagen by picro-Sirius red histologic analysis. A P < .05 was considered significant.

RESULTS

Thrombi were significantly larger in both 8-day and 21-day uPA -/- as compared with wild type (WT) and were significantly smaller in both 8-day and 21-day PAI-1 -/- as compared with WT. Correspondingly, 8-day plasmin levels were reduced in half in uPA -/- and increased three-fold in PAI-1 -/- when compared with respective WT thrombi (P < .05; n = 5-6). The endothelial marker CD31 was elevated two-fold in PAI-1 -/- mice at 8 days, but reduced 2.5-fold at 21 days in uPA -/- as compared with WT (P = .02; n = 5-6), suggesting less endothelial preservation. Vein wall vascular smooth muscle cell (VSMC) gene expression showed that 8-day and 21-day PAI-1 -/- mice had 2.3- and 3.8-fold more SM22 and 1.8- and 2.3-fold more αSMA expression than respective WT (P < .05; n = 5-7), as well as 1.8-fold increased αSMA (+) cells (P ≤ .05; n = 3-5). No significant difference in MMP-2 or -9 activity was found in the PAI-1 -/- mice compared with WT, while 5.4-fold more MMP-9 was present in 21-day WT than 21-day uPA -/- (P = .03; n = 5). Lastly, collagen was ∼two-fold greater at 8 days in PAI-1 -/- IVC as compared with WT (P = .03; n = 6) with no differences observed in uPA -/- mice.

CONCLUSIONS

In stasis DVT, plasmin activity is critical for thrombus resolution. Divergent vein wall responses occur with gain or loss of plasmin activity, and despite smaller VT, greater vein wall fibrosis was associated with lack of PAI-1.

Gαq G proteins modulate MMP-9 gelatinase during remodeling of the murine femoral artery

BACKGROUND

Vessels heal after injury and G protein-coupled receptors are involved in the vascular smooth muscle cell proliferation required to form intimal hyperplasia. We have previously identified the role of Gαq in vascular smooth muscle cell proliferation in vitro. This study now examines the role of Gαq in the developing intimal hyperplasia in a murine model and the impact of disruption of Gαq signaling on intimal hyperplasia development.

METHODS

We employed a murine femoral wire injury model in which a micro-wire is passed through a branch of the femoral artery and used to denude the common femoral artery. We perfusion-fixed specimens and stained sections with hematoxylin-eosin and Movat's stains such that morphometric analysis could be performed using an Image-Pro system. We also harvested additional specimens of femoral artery and snap-froze them for Western blotting or zymography, to allow for the study of G protein expression and both protease expression and activity. We used contralateral vessels as controls. We immersed additional vessels in pluronic gel containing the chemical Gαq G protein inhibitors GP-2A, siRNA to Gαq or adenovirus containing mutant inactive Gαq.

RESULTS

Gαq expression increased in a time-dependent manner after femoral artery injury. Sham-operated vessels did not produce such a response. Inhibition of Gαq reduced cell proliferation without affecting cell migration. Interruption of Gαq signaling also inhibited the development of intimal hyperplasia. Inhibition of Gαq did not alter peak urinary-type plasminogen activator activity and expression, but did increase early plasminogen activator inhibitor-1 activity and expression. Inhibition of Gαq reduced peak metalloproteinase (MMP)-9 activity at Day 3 but did not influence peak MMP-2 activity at Day 7. Protein expression for MMP-9 was also decreased, but that of MMP-2 was not affected. There were no changes in the expression or the activity of the respective inhibitors for MMP-9 and MMP-2, and tissue inhibitor of metalloproteinases-1 and -2.

CONCLUSIONS

These data demonstrate that femoral wire injury in the mouse is associated with a time-dependent increase in Gαq expression. Inhibition of Gαq alters cell proliferation and is associated with decreased MMP-9 expression and activity.

Postthrombotic vein wall remodeling: preliminary observations

BACKGROUND

Postthrombotic syndrome is characterized by a fibrotic vein injury following deep vein thrombosis (DVT). We sought to quantify the change in vein wall thickness in patients who fail to resolve DVT by 6 months and whether there were differences in blood or plasma levels of inflammatory proteins associated with venous remodeling.

METHODS

Patients presenting with confirmed lower extremity DVT were prospectively recruited for this study. Duplex imaging of the lower extremity venous system was performed, and blood was collected at entrance and repeat evaluation with blood draw and ultrasound imaging at 1 and 6 months. DVT resolution and thickness of the vein wall was quantified by ultrasound imaging in each segment affected by thrombus, and a contralateral, unaffected vein wall served as a control. Gene and protein expression of inflammatory markers were examined from leukocytes and serum, respectively. Analysis of variance or Student t-tests were used, and a P < .05 was significant. N = 10 to 12 for all analyses.

RESULTS

Thirty-two patients (12 patients with DVT resolution at 6 months, 10 patients with persistent thrombus at 6 months, and 10 healthy controls) were compared. Both resolving and nonresolving DVT were associated with a 1.5- to 1.8-fold increased vein wall thickness at 6 months (P = .008) as compared with nonaffected vein wall segments. However, the thickness of the affected segments was 1.4-fold greater in patients who had total resolution of the DVT by 6 months than in patients who had persistent chronic thrombus 6 months after presentation (P = .01). There was a four- to five-fold increased level of matrix metalloproteinase-9 (MMP-9) antigen in thrombosed patients compared with nonthrombosed patient controls (P < .05), while Toll-like receptor-9 (TLR-9) gene expression was three-fold less than controls (P < .05) at enrollment. D-dimer and P-selectin were higher in thrombosed as compared to controls at diagnosis but not at 6 months. Both TLR-4 (marker of inflammation) and P-selectin gene expression were higher in leukocytes from patients with chronic DVT compared with those who resolved at 1 month after diagnosis (P < .05).

CONCLUSIONS

This preliminary study suggests ongoing vein wall remodeling after DVT, measurable by ultrasound and associated with certain biomarkers. At 6 months, the vein wall is markedly thickened and directly correlates with resolution. This suggests that the vein wall response is initiated early following thrombus formation and persists even in the presence of total resolution.

A biomechanical analysis of venous tissue in its normal and post-phlebitic conditions

Although biomechanical studies of the normal rat vein wall have been reported (Weizsacker, 1988; Plante, 2002), there are no published studies that have investigated the mechanical effects of thrombus formation on murine venous tissue. In response to the lack of knowledge concerning the mechanical consequences of thrombus resolution, distinct thrombus-induced changes in the biomechanical properties of the murine vena cava were measured via biaxial stretch experiments. These data served as input for strain energy function (SEF) fitting and modeling (Gasser et al., 2006). Statistical differences were observed between healthy and diseased tissue with respect to the structural coefficient that represents the response of the non-collagenous, isotropic ground substance. Alterations following thrombus formation were also noted for the SEF coefficient which describes the anisotropic contribution of the fibers. The data indicate ligation of the vena cava leads to structural alterations in the ground substance and collagen fiber network.

Vein wall remodeling after deep vein thrombosis: differential effects of low molecular weight heparin and doxycycline

BACKGROUND

Venous thrombus resolution sets up an early intense inflammatory reaction, from which vein wall damage results. Tissue response to injury includes matrix metalloproteinase (MMP) activation and extracellular matrix protein turnover. This study sought to determine the effect of exogenous MMP inhibition and its potential attenuation of early vein wall injury.

METHODS

Rats received treatment beginning 24 hr after a stasis venous thrombosis by near occlusive ligation and until harvest at day 7. Three groups were evaluated: (1) vehicle saline controls (NaCl), (2) low molecular weight heparin (LMWH; Lovenox, 3 mg/kg daily SQ), and (3) doxycycline (DOXY, 30 mg/kg daily PO). Thrombus size (mg/mm), levels of tumor necrosis factor alpha (TNF alpha) and D-dimer by colorimetric assay, and monocytes counts by immunohistochemistry were assessed. Vein wall assessment included stiffness by tensiometry, interleukin 1beta (IL-1 beta protein levels by enzyme-linked immunosorbent assay, MMP2 and -9 by zymography, and histological analysis of intimal thickness (IT). Comparisons were by t-test to control. p < 0.05 was considered significant.

RESULTS

Thrombus sizes were similar at days 2 and 7 for all three groups, while thrombus TNFalpha was increased in 2-day LMWH- and DOXY-treated groups (NaCl = 1.0 +/- 0.8, LWMH = 9 +/- 3, DOXY = 27 +/- 5 pg/mg protein, n = 6-8, p < 0.05) and at 7 days in the DOXY group (NaCl = 3.0 +/- 2.5, DOXY = 23 +/- 4.2 pg/mg protein, n = 5, p < 0.05). Vein wall stiffness at 7 days was less with LMWH treatment, but not with DOXY, compared to controls (NaCl = 0.33 +/- 0.05, LMWH = 0.17 +/- 0.03, DOXY = 0.43 +/- 0.09 N/mm, n = 5-7, p < 0.05). Vessel-wall IL-1 beta was reduced only in the DOXY group at 7 days (NaCl = 26 +/- 3, LMWH = 38 +/- 17, DOXY = 6 +/- 3 pg/mg protein, n = 4-6, p < 0.05), as was the IT score versus controls (NaCl = 2.2 +/- 0.6, LMWH =1.7 +/- 0.3, DOXY = 0.8 +/- 0.20, n = 4-6, p < 0.05). Zymographic MMP9 activity was significantly reduced at 2 days in the LMWH and DOXY groups (NaCl = 85 +/- 24, LMWH = 23 +/- 7( *), DOXY = 13 +/- 5 U/mg protein, n = 6-8, p < 0.05). MMP2 zymographic activity, thrombus monocyte cell counts, and D-dimer activity were not significantly different across groups.

CONCLUSION

Treatment with LMWH or DOXY did not alter the size of deep vein thrombosis, mildly altered thrombus composition, and differentially affected vein wall injury, despite similar reductions in early MMP9 activity. Whether exogenous MMP inhibition affects long-term vein wall fibrosis will require further study.

Thrombus resolution and vein wall injury: dependence on chemokines and leukocytes

Chronic venous insufficiency resulting in post-thrombotic syndrome occurs commonly after acute deep vein thrombosis, and is a prevalent cause of vascular disease morbidity in the community. Therefore, a better understanding of the pathophysiologic mechanisms that promote the development of chronic venous insufficiency could lead to novel approaches to interrupt the natural history and prevent post-thrombotic syndrome. In this paper, we will review the evidence that venous thrombus resolution is an inflammatory process that is dependent on chemokines and leukocytes.

Deep vein thrombosis resolution is impaired in diet-induced type 2 diabetic mice

OBJECTIVE

Type 2 diabetes mellitus results in a procoagulant and thrombogenic state that could predispose diabetic individuals to develop venous thrombosis. We sought to determine whether diet-induced type 2 diabetes mellitus affects deep venous thrombosis (DVT) resolution in a murine model.

METHODS

C57Bl/6 mice were fed a low-fat or a high-fat diet (n = 10) for 10 weeks, after which DVT was created in the inferior vena cava (IVC) by a combination of low flow and endothelial damage. The IVC and thrombus were harvested at 1 and 2 weeks. Thrombus resolution and neovascularization were investigated through transfemoral angiography (n = 10), thrombus size (n = 4) and weight (n = 10), and nitric oxide synthase 3 immunoquantification (n = 4). Macrophage content was assessed by CD68 immunoreactivity (n = 4). The fibrinolytic system (urokinase plasminogen activator [uPA] and plasminogen activator inhibitor-1 [PAI-1]) was analyzed by Western immunoblotting (n = 6) and immunohistochemistry (n = 4). Total collagen was stained by Sirius red. Matrix metalloproteinases (MMP)-2 and MMP-9 activities were evaluated by zymography and their expressions by Western immunoblotting (n = 6) and immunohistochemistry (n = 4).

RESULTS

Diabetic mice had significantly larger and heavier thrombi at 1 and 2 weeks (P < .05), threefold less neovascularization (P < .05), and 35-fold increase in macrophage content (P < .01), than control mice 2 weeks after surgery. IVC recanalization was documented in 90% of 2-week control mice and in 10% of 2-week diabetic mice (P < .01). Increased vein wall collagen and less uPA and more PAI-1 expressions with a decreased uPA/PAI-1 ratio (31%, P < .01) were documented at 2 weeks in diabetic mice. MMP-2 and MMP-9 activities and expressions were significantly increased in diabetic mice at 1 and 2 weeks (P < .05) compared with control mice.

CONCLUSION

Diet-induced type 2 diabetes may impair DVT resolution through altered inflammatory, fibrinolytic, and MMP responses.

Effects of reduced cyclic stretch on vascular smooth muscle cell function of pig carotids perfused ex vivo

BACKGROUND

With advancing age arteries stiffen, reducing arterial compliance and leading to the development of systolic hypertension and to a substantial increase in pulse pressure. An augmented pulse pressure can be a predictor of the development of hypertension, which has been linked to several cardiovascular diseases including atherosclerosis, and to pathologies such as diabetes and renal dysfunction. In this study, we tested the hypothesis that reduced wall compliance induces pulse-pressure-mediated changes in arterial wall metabolism and remodeling.

METHODS

Porcine carotid arteries were perfused for 24 h using an ex vivo arterial support system. Control arteries were exposed to a pulse shear stress (6 +/- 3 dynes/cm(2)) combined with a pulse pressure of 80 +/- 10 mm Hg, yielding a physiological cyclic stretch of 4-5%. A reduced compliance group was also studied, in which arteries were wrapped with an external band, thereby decreasing cyclic stretch to levels <1%.

RESULTS

The experimentally reduced compliance caused a decreased contraction capacity induced by norepinephrine(NE), and this was associated with lower levels of alpha-smooth muscle cell-actin (alpha-SMC-actin) and desmin protein expressions. Arteries that were exposed to a reduced cyclic stretch exhibited a higher level of matrix metalloproteinase-2 (MMP-2) expression activity as well as an increase in Ki67 expression, thereby suggesting that matrix degradation and cellular proliferation had been initiated. Furthermore, the expression of plasminogen activator inhibitor-1 (PAI-1) in stiffened arteries was lower than in the control arteries.

CONCLUSIONS

These findings underline the importance of cyclic stretch in the maintenance of a differentiated and fully functional phenotype of vascular SMCs, as well as in the regulation of migratory properties, proliferation, and matrix turnover.