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Biomedical subjects

V W van Hinsbergh

Publications and source records attributed to V W van Hinsbergh.

At least 19 recordsLinked to original sources
PubMed2001

Vero cytotoxin binding to polymorphonuclear leukocytes among households with children with hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation of patients with HUS. This study investigated whether VT bound to PMNL could be detected in persons in households with patients with HUS. Serum antibodies against E. coli O157 and, when available, fecal samples from patients with HUS and household members were studied for the presence of VTEC infection. The circulating PMNL of 82% of the household members were positive for VT, whereas stool and/or serum examination showed only 21% positivity. Thus, current methods underestimate the number of infected persons in households with patients with HUS.

Adult↗
PubMed2001

Proteolysis of the urokinase-type plasminogen activator receptor by metalloproteinase-12: implication for angiogenesis in fibrin matrices.

Pericellular proteolysis plays an important role in cell migration and the formation of new capillary structures. The plasminogen activator/plasmin and matrix degrading metalloproteinase (MMP) cascades act together in the remodeling of matrix and cell-matrix contacts. Previously we have shown that the formation of capillary structures by human foreskin microvascular endothelial cells (hMVECs) in a 3-dimensional fibrin matrix requires a functional urokinase-type plasminogen activator receptor (u-PAR). Here we report on the unexpected finding that inhibition of hMVEC-derived MMP activity by BB94 (batimastat) increased the outgrowth of capillary structures in a fibrin matrix. BB94 prevented the release of the u-PA binding domain D1 of u-PAR and thereby increased the number of functional u-PARs on hMVECs without affecting the u-PAR messenger RNA levels. Comparison of various types of protease inhibitors pointed to the prime involvement of MMP activity. Using recombinant MMPs it was shown that MMP-12 activity was able to release the D1 domain of cellularly expressed u-PAR. In addition, the expression of MMP-12 in control and basic fibroblast growth factor/tumor necrosis factor-alpha-stimulated hMVECs was shown by reverse transcriptase-polymerase chain reaction, suggesting that endothelial cell-derived MMP-12 may be involved in angiogenesis-related u-PAR shedding. This new mechanism of u-PAR cleavage provides new insights into the mutual interactions between the MMP and u-PA/plasmin systems. Moreover, it may be helpful in the interpretation of recent data on the use of specific MMP inhibitors in the treatment of several types of cancer.

Binding Sites↗
PubMed2001

Aberrant fibrin formation and cross-linking of fibrinogen Nieuwegein, a variant with a shortened Aalpha-chain, alters endothelial capillary tube formation.

A congenital dysfibrinogenemia, fibrinogen(Nieuwegein), was discovered in a young man without any thromboembolic complications or bleeding. A homozygous insertion of a single nucleotide (C) in codon Aalpha 453 (Pro) introduced a stop codon at position 454, which resulted in the deletion of the carboxyl-terminal segment Aalpha 454-610. The ensuing unpaired cysteine at Aalpha 442 generated fibrinogen-albumin complexes of different molecular weights. The molecular abnormalities of fibrinogen(Nieuwegein) led to a delayed clotting and a fibrin network with a low turbidity. Electron microscopy confirmed that thin fibrin bundles were organized in a fine network. The use of fibrinogen(Nieuwegein)-derived fibrin (fibrin(Nieuwegein)) in an in vitro angiogenesis model resulted in a strong reduction of tube formation. The ingrowth of human microvascular endothelial cells (hMVEC) was independent of alpha(v)beta(3), indicating that the reduced ingrowth is not due to the absence of the RGD-adhesion site at position Aalpha 572-574. Rather, the altered structure of fibrin(Nieuwegein) is the cause, since partial normalization of the fibrin network by lowering the pH during polymerization resulted in an increased tube formation. Whereas factor XIIIa further decreased the ingrowth of hMVEC in fibrin(Nieuwegein), tissue transglutaminase (TG), which is released in areas of vessel injury, did not. This is in line with the absence of the cross-linking site for TG in the alpha-chains of fibrinogen(Nieuwegein). In conclusion, this newly discovered congenital dysfibrinogenemia has a delayed clotting time and leads to the formation of an altered fibrin structure, which could not be cross-linked by TG and which is less supportive for ingrowth of endothelial cells.

Adult↗
PubMed2001

Adenoviral expression of a urokinase receptor-targeted protease inhibitor inhibits neointima formation in murine and human blood vessels.

BACKGROUND: Smooth muscle cell migration, in addition to proliferation, contributes to a large extent to the neointima formed in humans after balloon angioplasty or bypass surgery. Plasminogen activator/plasmin-mediated proteolysis is an important mediator of this smooth muscle cell migration. Here, we report the construction of a novel hybrid protein designed to inhibit the activity of cell surface-bound plasmin, which cannot be inhibited by its natural inhibitors, such as alpha(2)-antiplasmin. This hybrid protein, consisting of the receptor-binding amino-terminal fragment of uPA (ATF), linked to the potent protease inhibitor bovine pancreas trypsin inhibitor (BPTI), can inhibit plasmin activity at the cell surface. METHODS AND RESULTS: The effect of adenovirus-mediated ATF.BPTI expression on neointima formation was tested in human saphenous vein organ cultures. Infection of human saphenous vein segments with Ad.CMV.ATF.BPTI (5x10(9) pfu/mL) resulted in 87.5+/-3.8% (mean+/-SEM, n=10) inhibition of neointima formation after 5 weeks, whereas Ad.CMV.ATF or Ad.CMV.BPTI virus had only minimal or no effect on neointima formation. The efficacy of ATF.BPTI in vivo was demonstrated in a murine model for neointima formation. Neointima formation in the femoral artery of mice, induced by placement of a polyethylene cuff, was strongly inhibited (93.9+/-2%) after infection with Ad.CMV.mATF.BPTI, a variant of ATF.BPTI able to bind specifically to murine uPA receptor; Ad.CMV.mATF and Ad.CMV.BPTI had no significant effect. CONCLUSIONS: These data provide evidence that adenoviral transfer of a hybrid protein that binds selectively to the uPA receptor and inhibits plasmin activity directly on the cell surface is a powerful approach to inhibiting neointima formation and restenosis.

Adenoviridae↗
PubMed2001

The endothelium: vascular control of haemostasis.

Within many general functions the endothelium is equipped with a number of mechanisms that prevent thrombus formation in the circulatory system. It harbours factors that interrupt the coagulation cascade, such as antithrombin III, the protein C receptor thrombomodulin, and tissue factor pathway inhibitor. It prevents platelet activation by the production of nitric oxide and prostacyclin, exonucleotidases and surface heparan sulphates. Furthermore, it can trigger and control fibrinolysis by the synthesis and release of tissue-type plasminogen activator and its inhibitor PAI-1. The general properties of the endothelium are subject to adaptation by environmental factors, such as inflammatory mediators and shear forces. Interleukin-1 and tumour necrosis factor-alpha reduce the antithrombotic properties of the endothelium. Furthermore, local variation exists between different vascular beds and vessel types, such as in the endometrium. While the endothelium controls blood fluidity on its apical side, adaptation of the endothelium also prepares its involvement in tissue repair upon inflammation or damage. The fibrin matrix, which is formed after damage of the vascular system, not only acts as a sealing of the wound, but also facilitates the repair process by providing a scaffolding for cell invasion and angiogenesis.

Adaptation, Physiological↗
PubMed2001

Involvement of VEGFR-2 (kdr/flk-1) but not VEGFR-1 (flt-1) in VEGF-A and VEGF-C-induced tube formation by human microvascular endothelial cells in fibrin matrices in vitro.

Different forms of vascular endothelial growth factor (VEGF) and their cellular receptors (VEGFR) are associated with angiogenesis, as demonstrated by the lethality of VEGF-A, VEGFR-1 or VEGFR-2 knockout mice. Here we have used an in vitro angiogenesis model, consisting of human microvascular endothelial cells (hMVEC) cultured on three-dimensional (3D) fibrin matrices to investigate the roles of VEGFR-1 and VEGFR-2 in the process of VEGF-A and VEGF-C-induced tube formation. Soluble VEGFR-1 completely inhibited the tube formation induced by the combination of VEGF-A and TNF alpha (VEGF-A/TNF alpha). This inhibition was not observed when tube formation was induced by VEGF-C/TNF alpha or bFGF/TNF alpha. Blocking monoclonal antibodies specific for VEGFR-2, but not antibodies specifically blocking VEGFR-1, were able to inhibit the VEGF-A/TNF alpha-induced as well as the VEGF-C/TNF alpha-induced tube formation in vitro. P1GF-2, which interacts only with VEGFR-1, neither induced tube formation in combination with TNF alpha, nor inhibited or stimulated by itself the VEGF-A/TNF alpha-induced tube formation in vitro. These data indicate that VEGF-A or VEGF-C activation of the VEGFR-2, and not of VEGFR-1, is involved in the formation of capillary-like tubular structures of hMVEC in 3D fibrin matrices used as a model of repair-associated or pathological angiogenesis in vitro.

Animals↗
PubMed2001

In vivo suppression of restenosis in balloon-injured rat carotid artery by adenovirus-mediated gene transfer of the cell surface-directed plasmin inhibitor ATF.BPTI.

Injury-induced neointimal development results from migration and proliferation of vascular smooth muscle cells (SMC). Cell migration requires controlled proteolytic degradation of extracellular matrix surrounding the cell. Plasmin is a major contributor to this process by degrading various matrix proteins directly, or indirectly by activating matrix metalloproteinases. This makes it an attractive target for inhibition by gene transfer. An adenoviral vector, Ad.ATF.BPTI, was constructed encoding a hybrid protein, which consists of the aminoterminal fragment (ATF) of urokinase-type plasminogen activator (u-PA) linked to bovine pancreas trypsin inhibitor (BPTI), a potent inhibitor of plasmin. This hybrid protein binds to the u-PA receptor, thereby inhibiting plasmin activity at the cell surface, and was found to be a potent inhibitor of cell migration in vitro. Local infection with Ad.ATF.BPTI of balloon-injured rat carotid artery resulted in detectable expression of ATF.BPTI mRNA and protein in the vessel wall. Morphometric analysis of arterial cross-sections revealed that delivery of Ad.ATF.BPTI to the carotid artery wall at the time of balloon injury inhibited neointima formation by 53% (P < 0.01) at 14 days and 19% (P = NS) at 28 days after injury when compared with control vector-infected arteries. Intima/media ratios were decreased by 60% (P < 0.01) and 35% (P < 0.05) at 14 and 28 days, respectively, when compared with control vector-infected arteries. Furthermore, a small but significant increase in medial area was found in the Ad.ATF.BPTI-treated arteries at 28 days (P < 0.05). These results show that local infection of the vessel wall with Ad.ATF.BPTI reduces neointima formation, presumably by inhibiting SMC migration, thereby offering a novel therapeutic approach to inhibiting neointima development.

Adenoviridae↗
PubMed2001

Prognostic implications of retinopathy and a high plasma von Willebrand factor concentration in type 2 diabetic subjects with microalbuminuria.

BACKGROUND: Microalbuminuria in subjects with type 2 diabetes may be heterogeneous with respect to clinical features, renal histology, and prognosis. There may be at least two types of microalbuminuria in diabetes, namely with and without generalized endothelial dysfunction. We investigated whether, among microalbuminuric subjects with type 2 diabetes, the presence of generalized endothelial dysfunction, as indicated by the presence of retinopathy or a high plasma von Willebrand factor (vWf) level, has prognostic implications. METHODS: In 173 type 2 diabetic subjects of a population-based cohort, we assessed the urinary albumin-to-creatinine ratio, the plasma vWf level, and the presence of retinopathy. The main outcome was cardiovascular mortality. RESULTS: The absolute difference in 7 years' cardiovascular mortality between microalbuminuric (albumin-to-creatinine ratio 2.0-30.0 mg/mmol) and normoalbuminuric subjects was higher in the presence as compared to the absence of retinopathy (55.6 vs 11.1%). The age- and sex-adjusted relative risk (95% confidence interval) of cardiovascular mortality, as compared to normoalbuminuric subjects without retinopathy, was 1.1 (0.1-9.2) for normoalbuminuric subjects with retinopathy, 1.8 (0.5-6.7) for microalbuminuric subjects without retinopathy, and 9.8 (3.1-30.9) for microalbuminuric subjects with retinopathy. The absolute difference in risk of 7 years' cardiovascular mortality between microalbuminuric and normoalbuminuric subjects was higher in the presence as compared to the absence of a high (>1.89 IU/ml) vWf level (49.8 vs 16.4%). The age- and sex-adjusted relative risk of cardiovascular mortality, as compared to normoalbuminuric subjects without a high vWf level, was 1.5 (0.4-5.5) for normoalbuminuric subjects with a high vWf level, 2.6 (0.7-9.6) for microalbuminuric subjects without a high vWf level, and 12.0 (2.9-49.5) for microalbuminuric subjects with a high vWf level. These differences in risk of cardiovascular mortality did not change materially after further adjustment for known duration of diabetes, hypertension, creatinine clearance, level of glycated haemoglobin and high-density lipoprotein cholesterol, and presence of cardiovascular disease. Analysis of all-cause instead of cardiovascular mortality showed a similar difference in risk of mortality between microalbuminuric subjects with or without retinopathy or a high vWf level. CONCLUSIONS: Among type 2 diabetic subjects with microalbuminuria, the presence of retinopathy or a high plasma vWf level affects the risk of cardiovascular death. Although larger studies are necessary, these findings support the concept that microalbuminuria in type 2 diabetes can occur in the absence or the presence of generalized endothelial dysfunction, and that the latter is a much more 'malignant' condition than the former.

Aged↗
PubMed2001

Role of fibrin matrix in angiogenesis.

Angiogenesis, the formation of new blood vessels from existing vessels, plays an important role during development. In the adult, it is limited to the female reproductive system and to tissue repair and pathological conditions. Repair associated angiogenesis is usually accompanied by the presence of inflammatory cells, vascular leakage, and fibrin deposition. The temporary fibrin matrix acts, not only as a sealing matrix, but also as a scaffolding for invading leukocytes and endothelial cells during tissue repair. We have used a three-dimensional fibrin matrix to study the outgrowth of human microvascular endothelial cells in capillary-like tubular structures. This process is induced by the simultaneous addition of an angiogenic growth factor (bFGF or VEGF) and the cytokine TNF alpha, and is enhanced by hypoxia. It involves proteolytic activities, in particular cell bound urokinase/plasmin and matrix metalloproteinase activities. Modulation of the fibrin structure markedly affects the extent and stability of capillary tube formation in vitro. Preparation of fibrin at different pH (7.0-7.8) or crosslinking of the fibrin matrix induces differences in fibrin matrix rigidity and structure. This is accompanied by a change in capillary ingrowth. Heparins, in particular low molecular weight heparins, modulate the fibrin structure and by this action affect angiogenesis in vitro. A mutant fibrinogenNieuwegein, which lacks the terminal part of the A alpha chain of fibrin harboring an RGD sequence and the transglutaminase sequence, provided additional evidence that the structure of fibrin is an important determinant for angiogenesis. These findings may have impact on improving wound healing and on influencing angiogenesis in malignancies with a fibrinous stroma.

Animals↗
PubMed2001

Cytoskeletal effects of rho-like small guanine nucleotide-binding proteins in the vascular system.

Rho-like small GTPases, with their main representatives (Rho, Rac, and Cdc42), have been recognized in the past decade as key regulators of the F-actin cytoskeleton. Rho-like small GTPases are now known to play a major role in vascular processes caused by changes in the actin cytoskeleton, such as smooth muscle cell contraction, endothelial permeability, platelet activation, and leukocyte migration. Data are now accumulating regarding the involvement of Rho GTPases in vascular disorders associated with vascular remodeling, altered cell contractility, and cell migration. The unraveling of signal transduction pathways used by the Rho-like GTPases revealed many upstream regulators and downstream effector molecules, and their number is still growing. An important action of Rho, Rac, and Cdc42 is their ability to regulate the phosphorylation status of the myosin light chain, a major regulator of actin-myosin interaction. Present knowledge of the Rho-like small GTPases has resulted in the development of promising new strategies for the treatment of many vascular disorders, including hypertension, vasospasms, and vascular leakage.

Actins↗
PubMed2001

Impact of apolipoprotein(a) on in vitro angiogenesis.

Angiostatin, which consists of the kringle I-IV domains of plasminogen and which is secreted into urine, is an efficient inhibitor of angiogenesis and tumor growth. Because N-terminal apolipoprotein(a) [apo(a)] fragments, which also contain several types of kringle IV domains, are found in urine as well, we evaluated the potential angiostatic properties of these urinary apo(a) fragments and of a recombinant form of apo(a) [r-apo(a)]. We used human microvascular endothelial cell (hMVEC)-based in vitro assays of tube formation in 3-dimensional fibrin matrixes. Purified urinary apo(a) fragments or r-apo(a) inhibited the basic fibroblast growth factor/tumor necrosis factor-alpha-induced formation of capillary-like structures. At concentrations varying from 0.2 to 10 microgram/mL, urinary apo(a) fragments inhibited tube formation by as much as 70%, whereas there was complete inhibition by r-apo(a). The highest concentrations of both inhibitors also reduced urokinase plasminogen activator production of basic fibroblast growth factor-induced hMVEC proliferation. The inhibitors had no effect on plasminogen activator inhibitor-1 expression. If our in vitro model for angiogenesis is valid for the in vivo situation as well, our data point toward the possibility that apo(a) may also be physiologically operative in modulating angiogenesis, as the concentration of free apo(a) found in humans exceeds that tested herein.

Angiogenesis Inhibitors↗
PubMed2001

Decreased smooth muscle cell/extracellular matrix ratio of media of femoral artery in patients with atherosclerosis and hyperhomocysteinemia.

The aim of this study was to determine whether the morphology of the muscular femoral artery in patients with atherosclerosis and hyperhomocysteinemia differs from that of atherosclerotic vessels from patients with normal homocysteine levels. Whole-vessel biopsies of the superficial femoral artery were taken from patients with symptomatic atherosclerotic disease with and without hyperhomocysteinemia and from patients without atherosclerosis from traumatic amputations. The morphology of these specimens was studied qualitatively by light and electron microscopy and quantitatively by light microscopy in combination with a video overlay system. Atherosclerotic lesions in patients with hyperhomocysteinemia were morphologically similar to those in patients with normal homocysteine levels, except for a significantly decreased smooth muscle cell/extracellular matrix ratio of the media in hyperhomocysteinemic patients (P=0.02 versus normohomocysteinemic atherosclerotic group and P=0.001 versus group without a history of cardiovascular disease). Hyperhomocysteinemia is associated with a significant decrease of the smooth muscle cell/extracellular matrix ratio of the media of muscular femoral arteries without significant changes in medial thickness. Further investigations should concentrate on the cause of this newly discovered phenomenon and its impact on vascular compliance.

Adult↗
PubMed2001

Enhanced angiogenic capacity and urokinase-type plasminogen activator expression by endothelial cells isolated from human endometrium.

The endometrium is a tissue unique for its cyclic destruction and rapid regeneration of blood vessels. Angiogenesis, indispensable for the regeneration process, provides a richly vascularized, receptive endometrium fundamental for implantation, placentation, and embryogenesis. Human endometrial microvascular endothelial cells (hEMVEC) were isolated to better understand the properties and angiogenic behavior of these cells. Unlike human foreskin microvascular endothelial cells (hFMVEC), which proliferated better upon stimulation by basic fibroblast growth factor, hEMVEC were much more sensitive to vascular endothelial growth factor A (VEGF-A) stimulation, probably due to enhanced VEGF receptor 2 expression. In addition, hEMVEC displayed an enhanced expression of the urokinase-type plasminogen activator (u-PA) compared with hFMVEC. No differences were found in tissue-type PA, PA inhibitor-1, and u-PA receptor expression. The high expression of u-PA by hEMVEC was also found in tissue sections. hEMVEC formed capillary-like structures when cultured in 20% human serum on top of three-dimensional fibrin matrices, and VEGF-A or basic fibroblast growth factor increased this tube formation. This is in contrast with hFMVEC, which formed tubes only after simultaneous stimulation by a growth factor and tumor necrosis factor-alpha. The high basal level of u-PA contributes to and may explain the higher angiogenic properties of hEMVEC (in vitro).

Capillaries↗
PubMed2001

Hypoxia in combination with FGF-2 induces tube formation by human microvascular endothelial cells in a fibrin matrix: involvement of at least two signal transduction pathways.

Hypoxia in combination with a growth factor is a strong inducer of angiogenesis. Among several effects, hypoxia can activate endothelial cells directly, but the mechanism by which it acts is not fully elucidated. In vitro, human microvascular endothelial cells (hMVEC) form capillary-like tubules in fibrin solely after stimulation with a combination of fibroblast growth factor (FGF)-2 or vascular endothelial growth factor (VEGF) and the cytokine tumour necrosis factor (TNF)alpha. We show in this paper that in hypoxic conditions, FGF-2-stimulated hMVEC form tube-like structures in a fibrin matrix in the absence of TNFalpha. Hypoxia/FGF-2-stimulated cells express more urokinase-type plasminogen activator (u-PA) receptor than normoxia/FGF-2-stimulated cells and display a slightly higher turnover of u-PA. This small increase in u-PA activation probably cannot fully explain the hypoxia/FGF-2-induced tube formation. Hypoxia activated at least two signal pathways that may contribute to the enhanced angiogenic response. In hypoxia/FGF-2-stimulated hMVEC the transcription factor p65 was activated and translocated to the nucleus, whereas in normoxia/FGF-2-stimulated cells p65 remained inactive. Furthermore, in hypoxic conditions, the amounts of phosphorylated mitogen-activated protein kinases ERK1/2 were increased compared to normoxic conditions. We conclude that hypoxia is able to activate different signal pathways in FGF-2-stimulated human endothelial cells, which may be involved in hypoxia-induced angiogenesis.

Cell Hypoxia↗
PubMed2001

Vascular endothelial growth factor enhances the expression of urokinase receptor in human endothelial cells via protein kinase C activation.

Among other proteolytic enzymes, the urokinase-type plasminogen activator (u-PA)/plasmin cascade contributes to cell migration and the formation of capillary-like structures in a fibrinous exudate. The u-PA receptor (u-PAR) focuses proteolytical activity on the cell surface of the endothelial cell and hereby accelerates the pericellular matrix degradation. Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF)-2 enhance u-PA receptor expression in human endothelial cells. In this paper we show that the protein kinase C (PKC) inhibitors Ro31-8220 and GF109203X inhibit VEGF165-induced u-PAR antigen expression in human endothelial cells, whereas PKC inhibition had no effect on FGF-2-induced u-PAR antigen enhancement. In addition, inhibition of PKC activity had no effect on VEGF165- or FGF-2-induced proliferation in human endothelial cells. We conclude that VEGF165 induces u-PAR via a PKC-dependent pathway, whereas proliferation is induced via a different pathway probably involving tyrosine phosphorylation of proteins downstream of the VEGF receptors.

Cell Division↗
PubMed2000

Simvastatin improves disturbed endothelial barrier function.

BACKGROUND: Recent clinical trials have established that inhibitors of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) reduce the risk of acute coronary events. These effects of statins cannot be fully explained by their lipid-lowering potential. Improved endothelial function may contribute to the positive effects of statin treatment. METHODS AND RESULTS: In the present study, we report that simvastatin reduces endothelial barrier dysfunction, which is associated with the development of atherosclerosis. Treatment of human umbilical vein endothelial cells for 24 hours with 5 micromol/L simvastatin reduced the thrombin-induced endothelial barrier dysfunction in vitro by 55+/-3%, as assessed by the passage of peroxidase through human umbilical vein endothelial cell monolayers. Similar effects were found on the thrombin-induced passage of (125)I-LDL through human aortic endothelial cell monolayers. This reduction in barrier dysfunction by simvastatin was both dose and time dependent and was accompanied by a reduction in the thrombin-induced formation of stress fibers and focal adhesions and membrane association of RhoA. Simvastatin treatment had no effect on intracellular cAMP levels. In Watanabe heritable hyperlipidemic rabbits, treatment for 1 month with 15 mg/kg simvastatin reduced vascular leakage in both the thoracic and abdominal part of the aorta, as evidenced by the Evans blue dye exclusion test. The decreased permeability was not accompanied by a reduction of oil red O-stainable atherosclerotic lesions. CONCLUSIONS: These data show that simvastatin, in a relatively high concentration, improves disturbed endothelial barrier function both in vitro and in vivo. The data also support the beneficial effects of simvastatin in acute coronary events by mechanisms other than its lipid-lowering effect.

Animals↗
PubMed2000

Unfractionated and low molecular weight heparin affect fibrin structure and angiogenesis in vitro.

Cancer patients treated for venous thromboembolism with low molecular weight heparin (LMWH) have a better survival rate than patients treated with unfractionated heparin (UFH). Because fibrin-associated angiogenesis is an important determinant in the progression and metastasis of many solid tumors, the effects of heparins on in vitro angiogenesis were investigated. Both UFH and LMWH inhibited bFGF-induced proliferation of human microvascular endothelial cells (hMVECs) to the same the extent (36-60%). VEGF165-induced proliferation was inhibited to a to a lesser extent (19-33%). Turbidity measurements and electron microscopy showed that the presence of LMWH during polymerization of the fibrin matrix led to a more transparent rigid network with thin fibrin bundles, whereas the presence of UFH resulted in a more opaque more porous network with thick fibrin fibers. We used a human in vitro angiogenesis model, which consisted of hMVECs seeded on top of a fibrin matrix, and stimulated the cells with basic fibroblast growth factor plus tumor necrosis factor a to induce capillary-like tubular structures. The formation of capillary-like tubular structures was retarded with matrices polymerized in the presence of LMWH (46% inhibition compared with a control matrix for both 1.5 and 10 units/ml LMWH), whereas matrices polymerized in the presence of UFH facilitated tubular structure formation (72 and 36% stimulation compared with a control matrix for 1.5 and 10 units/ml UFH, respectively). Similar results were obtained for cells stimulated with vascular endothelial growth factor plus tumor necrosis factor alpha. These data demonstrate the inhibitory effect of heparins on proliferation of hMVECs and provide a novel mechanism by which LMWH may affect tumor progression, namely reduced ingrowth of microvascular structures in a fibrinous stroma matrix by rendering it less permissive for invasion.

Cell Division↗