Search

For the successful application of RNA interference in vivo, it is desired to achieve (local) delivery of small interfering RNAs (siRNAs) and long-term gene silencing. Nonviral electrodelivery is suitable to obtain local and prolonged expression of transgenes. By intramuscular electrodelivery of a plasmid in which two opposing human polymerase III promoters (H1 and U6) drive the expression of siRNA constructs that form functional double-stranded siRNAs, in combination with in vivo bioluminescence imaging, we were able to knock down exogenous delivered luciferase for at least 100 days in murine calf muscles. This effect was sequence specific, because scrambled siRNA had no effect. Moreover, we were able to demonstrate in vivo reduction of endogenous TLR4 expression for at least 1 week, using a similar vector expressing an siRNA for TLR4 in the muscle. In this study, we demonstrate that in vivo suppression of both endogenous (for at least 1 week) and introduced genes (>100 days) is feasible via plasmid-driven siRNA expression after electroporation-mediated intramuscular gene transfer. With this approach the short-term effect of oligonucleotides and the drawbacks of viral gene delivery, like immunological responses, could be circumvented. Therefore, this application of RNA interference is a useful tool with which to investigate gene function and might be promising as a therapeutic tool for locally acting diseases such as restenosis or tumors.

Background: Drug-eluting stents (DES) have been introduced successfully in clinical practice to prevent post-angioplasty restenosis. Nevertheless, concerns about the safety of DES still exist., Objective: To investigate the vascular pathology and transcriptional responses to sirolimus and paclitaxel in a murine model for restenosis on underlying diseased atherosclerotic arteries., Methods: Atherosclerotic lesions were induced by placement of a perivascular cuff around the femoral artery of hypercholesterolaemic ApoE*3-Leiden transgenic mice. Two weeks later these cuffs were replaced either by sirolimus- or paclitaxel-eluting cuffs. The vascular pathological effects were evaluated after two additional weeks., Results: Both anti-restenotic compounds significantly inhibited restenotic lesion progression on the atherosclerotic plaques. Vascular histopathological analyses showed that local delivery of sirolimus has no significant adverse effects on vascular disease. Conversely, high dosages of paclitaxel significantly increased apoptosis, internal elastic lamina disruption, and decreased medial and intimal smooth muscle cells and collagen content. Moreover, transcriptional analysis by real-time RT-PCR showed an increased level of pro-apoptotic mRNA transcripts (FAS, BAX, caspase 3) in paclitaxel-treated arteries., Conclusions: Sirolimus and paclitaxel are effective in preventing restenosis. Sirolimus has no significant effect on arterial disease. In contrast, paclitaxel at high concentration demonstrated adverse vascular pathology and transcriptional responses, suggesting a narrower therapeutic range of this potent drug. Since the use of overlapping stents is becoming more common in DES technology, this factor is important, given that higher dosages of paclitaxel may lead to increased apoptosis in the vessel wall and, consequently, to a more unstable phenotype of the pre-existing atherosclerotic lesion.

Objective: Inflammatory factors are thought to play a regulatory role in restenosis. Interleukin-10 (IL10) is an important anti-inflammatory cytokine with anti-atherogenic potentials. The aim of this study was to assess the effects of IL10 modulation on cuff-induced neointima formation in hypercholesterolemic APOE*3-Leiden mice., Methods: The involvement of IL10 in neointima formation was studied in a hypercholesterolemic mouse model of cuff-induced stenosis of the femoral artery by IL10 knocking-out or overexpression procedures. IL10(+/-) mice were crossbred with APOE*3-Leiden mice to generate hypercholesterolemic APOE*3-LeidenIL10(-/-) mice. To achieve IL10 overexpression in APOE*3-Leiden mice, a single intramuscular injection of a murine IL10 overexpression plasmid was performed followed by electroporation., Results: Knocking-out IL10, in hypercholesterolemic APOE*3-Leiden mice, resulted in a significant 1.9-fold increase of neointima surface as compared to APOE*3-LeidenIL10(+/+) littermates (p=0.02). Conversely, a marked 45% inhibition on cuff-induced neointima formation was obtained after IL10 overexpression (p=0.02). Electrodelivery of IL10 vector leads to detectable IL10 serum levels, with a sustained expression over the experimental period of 3 weeks. IL10 overexpression reduced plasma cholesterol levels in APOE*3-Leiden mice, whereas IL10 deficiency in these mice did not lead to altered cholesterol levels as compared to the IL10(+/+) group. Finally, IL10 overexpression stimulated endogenous IL10 mRNA expression in the spleen and reduced the transcriptional responses of several pro-inflammatory cytokines., Conclusion: Here, we clearly demonstrate the role of IL10 in the development of neointima formation in hypercholesterolemic mice and the potential therapeutic effect of non-viral electrodelivery of IL10 cDNA to inhibit post-angioplasty restenosis.

Objective: Vascular endothelial growth factor (VEGF)-induced stromal cell-derived factor-1 (SDF-1) has been implicated in angiogenesis in ischemic tissues by recruitment of CXCR4-positive bone marrow-derived circulating cells with paracrine functions in preclinical models. Here, evidence for this is provided in patients with peripheral artery disease., Methods and Results: Expression patterns of VEGF, SDF-1, and CXCR4 were studied in amputated limbs of 16 patients. VEGF-A was expressed in vascular structures and myofibers. SDF-1 was expressed in endothelial and subendothelial cells, whereas CXCR4 was expressed in proximity to capillaries. VEGF-A, SDF-1, and CXCR4 expressions were generally decreased in ischemic muscle as compared with nonischemic muscle in patients with chronic ischemia (0.41-fold, 0.97-fold, and 0.54-fold induction [medians], respectively), whereas substantially increased in 2 patients with acute-on-chronic ischemia (3.5- to 65.8-fold, 3.9- to 19.0-fold, and 4.1- to 30.6-fold induction, respectively). Furthermore, these gene expressions strongly correlated with capillary area. Only acute ischemic tissue displayed a high percentage of hypoxia-inducible factor-1alpha-positive nuclei., Conclusions: These data suggest that VEGF and SDF-1 function as pro-angiogenic factors in patients with ischemic disease by perivascular retention of CXCR4-positive cells. Furthermore, these genes are downregulated in chronic ischemia as opposed to upregulated in more acute ischemia. The VEGF-SDF-1-CXCR4 pathway is a promising target to treat chronic ischemic disease.

Genetic factors appear to be important in the process of restenosis after percutaneous coronary intervention (PCI), as well as in inflammation, a pivotal factor in restenosis. An important mediator in the inflammatory response is interleukin (IL)-10. Our aim was to study whether genetic variants in IL-10 predispose to the risk of restenosis. The GENetic DEterminants of Restenosis (GENDER) study included 3104 patients treated with successful PCI. Target vessel revascularization (TVR) was chosen as primary end point. Genotyping of the -2849G/A, -1082G/A, -592C/A and +4259A/G polymorphisms of the IL-10 gene was performed by MassArray platform. After adjusting for clinical variables, three polymorphisms significantly increased the risk of restenosis (-2849AA: relative risk (RR), 1.7, 95% confidence interval (CI), 1.2-2.5; -1082AA: RR, 1.4, 95% CI, 1.1-1.8 and +4259GG: RR, 2.0, 95% CI, 1.4-2.8). To further exclude possible involvement of neighboring genes due to LD in the IL-10 locus, additional polymorphisms were genotyped. The results reveal that association of the IL-10 gene with restenosis is independent of flanking genes. Our findings demonstrate that IL-10 is associated with restenosis and therefore support the hypothesis that anti-inflammatory genes also may be involved in developing restenosis. Furthermore, they may provide a new targeting gene for drug-eluting stents.

Innate immunity is the first line of defence against invading micro-organisms. The family of Toll-like receptors (TLRs) recognizes pathogen-associated molecular patterns (PAMPs) that are carried by the invading micro-organisms. Infectious pathogens have been implicated to play an important role in atherosclerosis. Nowadays, evidence is accumulating that TLRs play an important role in the initiation and progression of atherosclerosis too. A lot is known about the exogenous ligands that are able to activate the TLRs, but it is also known that endogenous ligands have the capacity to activate TLRs when exogenous ligands are absent. Studies on knockout mice, epidemiological studies and even human polymorphism studies confirmed the important role of TLRs in development and progression of atherosclerotic disease. Studies with antagonists against TLR ligands and vaccination studies demonstrated that TLR signaling might be a potential target for intervention in the initiation and progression of atherosclerosis.

Unlabelled: Sclerostin is an osteocyte-derived negative regulator of bone formation. It inhibits BMP-stimulated bone formation both in vitro and in vivo but has no direct effect on BMP signaling. Instead, sclerostin inhibits Wnt signaling that is required for BMP-stimulated osteoblastic differentiation., Introduction: Sclerostin is a member of the Dan family of glycoproteins of which many members have been reported to antagonize BMP activity. Sclerostin has been shown to inhibit BMP-stimulated bone formation, but its mechanism of action seems to be different from classical BMP antagonists. In this study, we investigated the mechanism by which sclerostin inhibits BMP-stimulated bone formation., Materials and Methods: DNA electroporation of calf muscle of mice using expression plasmids for BMP and sclerostin was used to study the effect of sclerostin on BMP-induced bone formation in vivo. Transcriptional profiling using microarrays of osteoblastic cells treated with BMP in the absence or presence of sclerostin was used to find specific growth factor signaling pathways affected by sclerostin. The affected pathways were further studied using growth factor-specific reporter constructs., Results: BMP-induced ectopic bone formation in calf muscle of mice was prevented by co-expression of sclerostin in vivo. Transcriptional profiling analysis of osteoblastic cultures indicated that sclerostin specifically affects BMP and Wnt signaling out of many other growth signaling pathways. Sclerostin, however, did not inhibit stimulation of direct BMP target genes. Furthermore, we did not obtain any evidence for sclerostin acting as a direct BMP antagonist using a BMP-specific reporter construct. In contrast, sclerostin shared many characteristics with the Wnt antagonist dickkopf-1 in antagonizing BMP-stimulated bone formation and BMP- and Wnt-induced Wnt reporter construct activation., Conclusions: Sclerostin inhibits BMP-stimulated bone formation but does not affect BMP signaling. Instead, it antagonizes Wnt signaling in osteoblastic cells. High bone mass in sclerosteosis and van Buchem disease may, therefore, result from increased Wnt signaling.

Objective: Neointima formation is the underlying mechanism of (in-stent) restenosis. 17beta-Estradiol (E2) is known to inhibit injury-induced neointima formation and post-angioplasty restenosis. Estrogen receptor alpha (ERalpha) has been demonstrated to mediate E2 anti-restenotic properties. However, the role of estrogen receptor beta (ERbeta) is not fully elucidated. In the present study, the specific role of vascular ERalpha and ERbeta in neointima formation is assessed., Methods and Results: Neointima formation was induced by placement of a perivascular cuff around the femoral artery of male C57BL/6J mice. E2-eluting cuffs significantly inhibited cuff-induced neointima formation. To address the specific roles of ERalpha and ERbeta on neointima formation, the ERalpha-selective agonist 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)tris-phenol (PPT) and the ERbeta-selective agonist 2,3-bis(4-hydroxy-phenyl)-propionitrile (DPN) were applied via a drug-eluting cuff. PPT inhibited neointima formation at low but not at high concentrations. Conversely, DPN inhibited neointima formation dose dependently. To demonstrate the specificity of these responses, an ERalpha-selective antagonist, MPP, was also used in combination with E2, PPT, or DPN. While the effect of PPT on neointima formation inhibition was blocked by co-delivery of MPP, E2 and DPN could still inhibit neointima formation., Conclusions: Our data suggest that, in addition to ERalpha, specific ERbeta activation inhibits neointima formation in a mouse model of restenosis. These data reveal a yet unidentified protective role of ERbeta on neointima formation.

Ischemic disease represents the new epidemic worldwide. Animal models of ischemic disease are useful because they can help us to understand the underlying pathogenetic mechanisms and develop new therapies. The present review article summarizes the results of a consensus conference on the status and future development of experimentation in the field of cardiovascular medicine using murine models of peripheral and myocardial ischemia. The starting point was to recognize the limits of the approach, which mainly derive from species- and disease-related differences in cardiovascular physiology. For instance, the mouse heart beats at a rate 10 times faster than the human heart. Furthermore, healing processes are more rapid in animals, as they rely on mechanisms that may have lost relevance in man. The main objective of the authors was to propose general guidelines, diagnostic end points and relevance to clinical problems.

Objective: Because late vein graft failure is caused by intimal hyperplasia (IH) and accelerated atherosclerosis, and these processes are thought to be inflammation driven, influx of monocytes is one of the first phenomena seen in IH, we would like to provide direct evidence for a role of the MCP-1 pathway in the development of vein graft disease., Methods and Results: MCP-1 expression is demonstrated in various stages of vein graft disease in a murine model in which venous interpositions are placed in the carotid arteries of hypercholesterolemic ApoE3Leiden mice and in cultured human saphenous vein (HSV) segments in which IH occurs. The functional involvement of MCP-1 in vein graft remodeling is demonstrated by blocking the MCP-1 receptor CCR-2 using 7ND-MCP-1. 7ND-MCP1 gene transfer resulted in 51% reduction in IH in the mouse model, when compared with controls. In HSV cultures neointima formation was inhibited by 53%. In addition, we demonstrate a direct inhibitory effect of 7ND-MCP-1 on the proliferation of smooth muscle cell (SMC) in HSV cultures and in SMC cell cultures., Conclusions: These data, for the first time, prove that MCP-1 has a pivotal role in vein graft thickening due to intimal hyperplasia and accelerated atherosclerosis.

Despite advances in revascularization techniques, limb salvage and relief of pain cannot be achieved in many diabetic patients with diffuse peripheral vascular disease. Our objective was to determine the effect of intramuscular administration of phVEGF165 (vascular endothelial growth factor gene-carrying plasmid) on critical limb ischemia (CLI) compared with placebo (0.9% NaCl). A double-blind, placebo-controlled study was performed in 54 adult diabetic patients with CLI. The primary end point was the amputation rate at 100 days. Secondary end points were a 15% increase in pressure indices (ankle-to-brachial index and toe-to-brachial index), clinical improvement (skin, pain, and Quality of Life score), and safety. In patients (n=27) treated with placebo versus phVEGF165-treated patients (n=27) the following results were found: 6 amputations versus 3 (p=not significant [NS]); hemodynamic improvement in 1 versus 7 (p=0.05); improvement in skin ulcers, 0 versus 7 (p=0.01); decrease in pain, 2 versus 5 (p=NS); and overall, 3 versus 14 responding patients (p=0.003). No grade 3 or 4 adverse effects were seen in these patients. We conclude that this small, randomized gene therapy study failed to meet the primary objective of significant amputation reduction. However, significant and meaningful improvement was found in patients treated with a VEGF165-containing plasmid. There were no substantial adverse events.

In coronary artery bypass surgery, the patency of arterial grafts is higher than that of venous grafts because of vein-graft disease, which involves excessive proliferation of venous smooth muscle cells (SMCs) and subsequent accelerated atherosclerosis. We studied the function of TR3 nuclear orphan receptor (TR3) in the early response of SMCs to mechanical strain, a major initiator of vein-graft disease. We demonstrate that TR3 expression is induced in human saphenous vein segments exposed ex vivo to whole-blood perfusion under arterial pressure. Cultured venous SMCs challenged by cyclic stretch displayed TR3 induction and enhanced DNA synthesis, whereas SMCs derived from the internal mammary artery remained quiescent. Small-interfering RNA-mediated knockdown of TR3 and adenovirus-mediated overexpression of TR3 in venous SMCs enhanced and abolished stretch-induced DNA synthesis, respectively. Accordingly, in organ cultures of wild-type murine vessel segments exposed to cyclic stretch, p27(Kip1) was down-regulated, whereas expression of this cell cycle inhibitor was unaffected by cyclic stretch in TR3-transgenic vessels, concordant with a lower proliferative response. Finally, stretch-mediated proliferation was inhibited by 6-mercaptopurine, an agonist of TR3. In conclusion, TR3 represents inhibitory mechanisms to restrict venous SMC proliferation and may contribute to prevention of vein-graft disease.

Objective: Collateral artery development (arteriogenesis), a vital compensatory mechanism in patients with arterial obstructive disease, may be deregulated by vascular risk factors, eg, diabetes or hypercholesterolemia. Here, we compared the effects of either disturbed glucose metabolism or disturbed lipid metabolism on arteriogenesis., Methods and Results: Femoral artery occlusion was performed in streptozotocin(STZ)-treated mice, nonobese diabetic (NOD) mice, and insulin-resistant Ob/Ob mice on regular diet, and APOE3*Leiden mice on different hypercholesterolemic diets. Angiography and laser Doppler perfusion analysis of hindlimbs were performed postoperatively. Surprisingly, angiographic arteriogenesis was not impaired in diabetic and insulin-resistant mice. Perfusion recovery in STZ-treated and Ob/Ob mice was only decreased by 19% and 16%, respectively (P<0.05). Furthermore, perfusion recovery was unchanged between high-glycemic and mild-glycemic NOD mice. Angiographic arteriogenesis in APOE3*Leiden mice, however, was markedly impaired at 7 days and 14 days (P< or =0.01). Correspondingly, perfusion recovery was 41% decreased in APOE3*Leiden mice (P<0.05). There was an inverse correlation of perfusion recovery with plasma cholesterol (P=0.02), but not with triglyceride, free fatty acid, glucose, or insulin levels., Conclusions: Hypercholesterolemia reduces arteriogenesis more dominantly than hyperglycemia or hyperinsulinemia in mice. This suggests that a disturbed lipid metabolism as observed in diabetic patients might be crucial for the impairment of collateral formation.

In 2001, the first human study with drug-eluting stents (DES) was published showing a nearly complete abolition of restenosis by using a sirolimus-eluting stent. This success was very encouraging to test new compounds in combination with the DES platform. Nevertheless, several other anti-restenotic compounds have been used in human clinical trials with disappointing outcomes. Little is known concerning potential adverse effects on vessel wall integrity and (re)healing, atherosclerotic lesion formation, progression, and plaque stability of these DES. Although efficacy and safety need to be determined clinically, preclinical testing of candidate drugs in well-defined animal models is extremely helpful to gain insight into the basic biological responses to candidate compounds. Here, we discuss and report an animal model which enables rapid screening of candidate drugs for DES on an atherosclerotic background. The results from drug testing using this novel model could help to quickly and cost-effectively establish the dose range of candidate drugs with reasonable potential for DES.

Pericellular proteases play an important role in angiogenesis and vasculogenesis. They comprise (membrane-type) matrix metalloproteinases [(MT-)MMPs], serine proteases, cysteine cathepsins, and membrane-bound aminopeptidases. Specific inhibitors regulate them. Major roles in initiating angiogenesis have been attributed to MT1-matrix metalloproteinase (MMP), MMP-2, and MMP-9. Whereas MT-MMPs are membrane-bound by nature, MMP-2 and MMP-9 can localize to the membrane by binding to alphavbeta3-integrin and CD44, respectively. Proteases switch on neovascularization by activation, liberation, and modification of angiogenic growth factors and degradation of the endothelial and interstitial matrix. They also modify the properties of angiogenic growth factors and cytokines. Neovascularization requires cell migration, which depends on the assembly of protease-protein complexes at the migrating cell front. MT1-MMP and urokinase (u-PA) form multiprotein complexes in the lamellipodia and focal adhesions of migrating cells, facilitating proteolysis and sufficient support for endothelial cell migration and survival. Excessive proteolysis causes loss of endothelial cell-matrix interaction and impairs angiogenesis. MMP-9 and cathepsin L stimulate the recruitment and action of blood- or bone-marrow-derived accessory cells that enhance angiogenesis. Proteases also generate fragments of extracellular matrix and hemostasis factors that have anti-angiogenic properties. Understanding the complexity of protease activities in angiogenesis contributes to recognizing new targets for stimulation or inhibition of neovascularization in disease.

Objective: The aim of this study was to assess whether the anti-inflammatory agent dexamethasone can inhibit vein graft thickening without the occurrence of serious side effects., Methods: Venous interposition grafting was performed in the common carotid artery of hypercholesterolemic ApoE3Leiden transgenic mice. Mice were treated with dexamethasone (0.15 mg.kg(-1).d(-1) orally), and after 28 days, vein graft thickening was quantified., Results: Treatment with dexamethasone resulted in a significant 43% reduction in lesion area without changes in lesion composition when compared with nontreated controls. However, dexamethasone, when administered for a prolonged period of time, is known for its potentially serious side effects. To overcome these potential side effects of prolonged dexamethasone treatment, the effect of a short-term 7-day dexamethasone treatment was studied. This short dexamethasone treatment resulted in a 49% decrease of vein graft thickening at 28 days. Furthermore, it was demonstrated that dexamethasone treatment led to reduced local expression of several proinflammatory cytokines and factors in the vein grafts 24 hours after surgery. Finally, observations in mice were verified in human saphenous organ cultures. Exposure to dexamethasone for either 7 or 28 days significantly reduced intimal hyperplasia formation on cultured saphenous vein segments., Conclusions: Short-term anti-inflammatory treatment with dexamethasone leads to a significant reduction in vein graft thickening over an extended period, possibly by the reduction of early expression of proinflammatory cytokines. This 7-day treatment minimizes the risk of unwanted side effects of long-term dexamethasone treatment and may be a new approach to prevent graft failure.

Genetic factors appear to be important in the restenotic process after percutaneous coronary intervention (PCI), as well as in inflammation, a pivotal factor in restenosis. TNFalpha, a key regulator of inflammatory responses, may exert critical influence on the development of restenosis after PCI. The GENetic DEterminants of Restenosis (GENDER) project included 3104 patients who underwent a successful PCI. Systematic genotyping for six polymorphisms in the TNFalpha gene was performed. The role of TNFalpha in restenosis was also assessed in ApoE*3-Leiden mice, TNFalpha knockout mice, and by local delivery of a TNFalpha biosynthesis inhibitor, thalidomide. The -238G-1031T haplotype of the TNFalpha gene increased clinical and angiographic risk of restenosis (P=0.02 and P=0.002, respectively). In a mouse model of reactive stenosis, arterial TNFalpha mRNA was significantly time-dependently up-regulated. Mice lacking TNFalpha or treated locally with thalidomide showed a reduction in reactive stenosis (P=0.01 and P=0.005, respectively). Clinical and preclinical data indicate that TNFalpha plays an important role in restenosis. Therefore, TNFalpha genotype may be used as a risk marker for restenosis and may contribute to individual patient screening prior to PCI in clinical practice. Inhibition of TNFalpha may be an anti-restenotic target strategy.

Objective: Dexamethasone-eluting stents are currently under evaluation to prevent post-angioplasty restenosis. The efficacy and safety of dexamethasone as an anti-restenotic agent is still unclear. We assess the effect of perivascular delivery of dexamethasone on vascular pathology in a mouse model of restenosis., Methods and Results: In this study we investigate the ability of both systemic and local dexamethasone treatment to inhibit neointima formation after cuff placement around C57BL/6 mouse femoral artery. As in the clinical situation, systemic dexamethasone treatment shows adverse side effects in animals, including weight loss. In contrast, local delivery of dexamethasone using a drug-eluting polymer cuff inhibits neointima formation and has no systemic adverse effects. Pathobiological examination of the experimental arteries, however, reveals a dose-dependent medial atrophy, a reduction in vascular smooth muscle cells and collagen content, an increase in apoptotic cell count and disruption of the internal elastic lamina., Conclusions: Our results demonstrate that although local dexamethasone delivery is effective as an inhibitor for neointima formation, it is dose-dependently associated with adverse vascular morphological changes pointing to a loss of vascular integrity.

Oncolytic adenoviruses exhibiting tumor-selective replication are promising anticancer agents. Insertion and expression of a transgene encoding tissue inhibitor of metalloproteinase-3 (TIMP-3), which has been reported to inhibit angiogenesis and tumor cell infiltration and induce apoptosis, may improve the antitumor activity of these agents. To assess the effects of TIMP-3 gene transfer to glioma cells, a replication-defective adenovirus encoding TIMP-3 (Ad.TIMP-3) was employed. Ad.TIMP-3 infection of a panel of glioma cell cultures decreased the proliferative capacity of these cells and induced morphologic changes characteristic for apoptosis. Next, a conditionally replicating adenovirus encoding TIMP-3 was constructed by inserting the TIMP-3 expression cassette into the E3 region of the adenoviral backbone containing a 24-bp deletion in E1A. This novel oncolytic adenovirus, AdDelta24TIMP-3, showed enhanced oncolytic activity on a panel of primary cell cultures and two glioma cell lines compared with the control oncolytic virus AdDelta24Luc. In vivo inhibition of matrix metalloproteinase (MMP) activity by AdDelta24TIMP-3 was shown in s.c. glioma xenografts. The functional activity of TIMP-3 was imaged noninvasively using a near-IR fluorescent MMP-2-activated probe. Tumoral MMP-2 activity was significantly reduced by 58% in the AdDelta24TIMP-3-treated tumors 24 hours after infection. A study into the therapeutic effects of combined oncolytic and antiproteolytic therapy was done in both a s.c. and an intracranial model for malignant glioma. Treatment of s.c. (U-87MG) or intracranial (U-87deltaEGFR) tumors with AdDelta24TIMP-3 and AdDelta24Luc both significantly inhibited tumor growth and prolonged survival compared with PBS-treated controls. However, expression of TIMP-3 in the context of AdDelta24 did not significantly affect the antitumor efficacy of this oncolytic agent.

Background: Furin-like proprotein convertases (PCs) are proteolytic activators of proproteins, like membrane type 1-matrix metalloproteinase (MT1-MMP) and transforming growth factor beta (TGF-beta), that are described in the arterial response to injury. However, the involvement of furin-like PCs in the arterial response to injury has not been studied yet. We studied furin, MT1-MMP, MMP levels and TGF-beta signaling after arterial injury. We also investigated the effect of an inhibitor of furin-like PCs, alpha1-antitrypsin Portland (alpha1-PDX), on arterial injury following balloon dilation., Methods and Results: NZW rabbit femoral and iliac arteries (N=42) were balloon dilated unilaterally and harvested after 2, 7, 14, 28 or 42 days. Furin mRNA levels were increased after 2 and 7 days. MMP-2 and MT1-MMP levels were increased after day 7 and TGF-beta signaling, by phosphorylating Smad 1/5 and 2/3, was increased at all time points. Inhibition of furin-like PCs, by adenoviral over-expression of alpha1-PDX, blocked proTGF-beta activation and Smad phosphorylation, and reduced MT1-MMP and MMP-2 activation (N=5). In vivo adventitial inhibition of furin-like PCs (N=9) resulted in a reduction of 13.1+/-5.2% in advential and 23.6+/-7.9% in intimal areas (P<0.05), but had no effect on lumen size due to decreased vessel areas., Conclusions: This study demonstrates that furin-like PCs are involved in the arterial response to injury possibly through activation of the TGF-beta-Smad signaling pathway and identifies furin-like PCs as a possible target to inhibit intimal hyperplasia.

Objectives: We sought to identify polymorphisms in genes that predispose to restenosis., Background: Variations in the lipoprotein lipase (LPL) gene have been implicated in a number of pathophysiologic conditions associated with coronary heart disease. The present study examines the impact of polymorphisms in the LPL gene on restenosis (defined by target vessel revascularization [TVR]) in a large patient population undergoing percutaneous coronary intervention (PCI). A mouse model for restenosis was used to further investigate LPL's role in restenosis., Methods: The GENetic DEterminants of Restenosis (GENDER) project is a multicenter, prospective study design that enrolled 3,104 consecutive patients after successful PCI. These patients were genotyped for four different LPL gene polymorphisms. In apolipoprotein E (ApoE)*3-Leiden transgenic mice, arterial messenger ribonucleic acid (mRNA) was used to assess LPL expression during a cuff-induced restenotic process., Results: Using multivariable analysis, carriers of the 447Ter allele of the LPL enzyme showed a lower risk of TVR compared with 447Ser homozygotes (p = 0.005). In the mouse model, LPL mRNA levels were increased 40-fold compared with control arteries at 6 h after cuff placement., Conclusions: The LPL C/G polymorphism (Ser447Ter), resulting in a truncation of the two C-terminal amino acids of the mature LPL protein, appears to be an important protective factor for TVR in humans. The role of LPL in this process was further established in a mouse model, where LPL expression was very strongly up-regulated in the target arterial wall, suggesting a contribution of this lipolytic enzyme to restenosis. Possibly, LPL Ser447Ter genotyping may lead to better risk stratification and tailored therapy in the prevention of restenosis after PCI.

The introduction of drug-eluting stents (DES) to prevent in-stent restenosis is one of the major advances in interventional cardiology. Currently many types of DES are under evaluation for effectiveness and safety, a time-consuming and difficult procedure in humans. An animal model that allows rapid evaluation of the present and upcoming therapeutic approaches to prevent in-stent restenosis is most valuable and still lacking. Here, a perivascular cuff to induce restenosis was constructed of a poly(epsilon-caprolactone) (PCL) formulation suitable for the controlled delivery of drugs. Placing the PCL cuff around the femoral artery, in vivo, resulted in reproducible restenosis-like lesions containing predominantly smooth muscle-actin positive cells. Loading the cuff with the anti-restenotic compounds paclitaxel and rapamycin resulted, in vitro, in a sustained and dose-dependent release for at least 3 weeks. Paclitaxel- and rapamycin-eluting PCL cuffs placed around the femoral artery of mice in vivo significantly reduced intimal thickening by 76 +/- 2% and 75 +/- 6%, respectively, at 21 days. Perivascular sustained release of both anti-restenotic agents is restricted to the cuffed vessel segment with no systemic adverse effects or effect on cuffed contralateral femoral arteries. Drug-eluting PCL cuffs provide an easy and rapid tool to evaluate anti-restenotic agents to be used in combination with the DES strategies.

Aims: Intimal hyperplasia, characterised by smooth muscle cell migration and proliferation, requires extracellular matrix degradation which is mediated by matrix metalloproteinases (MMPs). In this study, the effect of tetracycline derived doxycycline, a specific MMP inhibitor of both activity and synthesis, on intimal hyperplasia in vitro and in vivo was assessed., Methods and Results: Segments of human saphenous veins were cultured for 4 weeks in absence or presence of doxycycline (10microg/ml) (n=6). A 81% inhibition in intimal hyperplasia was observed in the doxycycline treated segments compared to controls. To assess the effect of doxycycline on intimal hyperplasia in vivo, perivascular cuffs were placed around femoral arteries in mice with or without doxycycline in the drinking water (3 mg/ml). In this in vivo model for intimal hyperplasia doxycycline significantly reduced (68%, n=6) intimal hyperplasia when compared to controls. In addition the effect of doxycycline on vein graft thickening was assessed in a murine venous interposition model. In this in vivo model vein graft thickening was reduced by 35 % in the doxycycline treated mice (3 mg/ml in drinking water). Furthermore, a reduction in vascular MMP expression was observed in these mice., Conclusion: Treatment with tetracycline derived doxycycline results in significant inhibition of intimal hyperplasia in vitro and in vivo and may be an effective strategy to prevent post interventional restenosis and vein graft disease.

Apart from counteracting matrix metalloproteinases, tissue inhibitor of metalloproteinases-3 (TIMP-3) has proapoptotic properties. These features have been attributed to the inhibition of metalloproteinases involved in the shedding of cell surface receptors such as the TNFR. However, little is known about effects of TIMP-3 in cells that are not susceptible to apoptosis by TNF-alpha. In this study, we report that gene transfer of TIMP-3 into human rheumatoid arthritis synovial fibroblasts and MRC-5 human fetal lung fibroblasts facilitates apoptosis and completely reverses the apoptosis-inhibiting effects of TNF-alpha. Although TNF-alpha inhibits Fas/CD95-induced apoptosis in untransfected and mock-transfected cells, fibroblasts ectopically expressing TIMP-3 are sensitized most strongly to Fas/CD95-mediated cell death by TNF-alpha. Neither synthetic MMP inhibitors nor glycosylated bioactive TIMP-3 are able to achieve these effects. Gene transfer of TIMP-3 inhibits the TNF-alpha-induced activation of NF-kappaB in rheumatoid arthritis synovial fibroblasts and reduces the up-regulation of soluble Fas/CD95 by TNF-alpha, but has no effects on the cell surface expression of Fas. Collectively, our data demonstrate that intracellularly produced TIMP-3 not only induces apoptosis, but also modulates the apoptosis-inhibiting effects of TNF-alpha in human rheumatoid arthritis synovial fibroblast-like cells. Thus, our findings may stimulate further studies on the therapeutic potential of gene transfer strategies with TIMP-3.

In-stent restenosis is the major drawback of percutaneous coronary interventions, occurring in 10-40% of the patients. Recently, new stents have emerged which are loaded with anti-inflammatory, anti-migratory, anti-proliferative or pro-healing drugs. These drugs are supposed to inhibit inflammation and neointimal growth and subsequently in-stent restenosis. In this review article the results of human clinical studies investigating drug-eluting stents are discussed from a clinical point of view, focussing on the efficacy in the prevention of restenosis and their potential side effects. Both success and failure in the field of drug-eluting stents have been described. Successful devices are the sirolimus-eluting and the polymer-based paclitaxel-eluting stents. Potentially dangerous side effects of drug-eluting stents are adverse drug interactions, incomplete stent apposition and increased in-stent thrombosis rates. Demonstration of long-term efficacy is mandatory since in some animal studies a delayed healing has been observed. Currently, the successful drug-eluting stents are under investigation in all types of lesions. We conclude that the results with some drug-eluting stents are promising, but further evidence on long-term efficacy and safety, also in high-risk subgroups, is needed.

In the endometrium, angiogenesis is a physiological process, whereas in most adult tissues neovascularization is initiated only during tissue repair or pathological conditions. Pericellular proteolysis plays an important role in angiogenesis being required for endothelial cell migration, invasion, and tube formation. We studied the expression of proteases by human endometrial microvascular endothelial cells (hEMVECs) and their involvement in the formation of capillary tubes and compared these requirements with those of foreskin MVECs (hFMVECs). Inhibition of urokinase and matrix metalloproteinase (MMP) both reduced tube formation in a fibrin or fibrin/collagen matrix. hEMVECs expressed various MMP mRNAs and proteins; in particular MMP-1, MMP-2, and membrane-type (MT)1-, MT3-, and MT4-MMPs. MT3- and MT4-MMP mRNA expressions were significantly higher in hEMVECs than in hFMVECs. Other MT-MMP mRNAs and MMP-9 were hardly detectable. Immunohistochemistry confirmed the presence of MT3-MMP in endothelial cells of endometrial tissue. Overexpression of tissue inhibitor of MMP (TIMP)-1 or TIMP-3 by adenoviral transduction of hEMVECs reduced tube formation to the same extent, whereas only TIMP-3 was able to inhibit tube formation by hFMVECs. Tube formation by hEMVECs was partly inhibited by the presence of anti-MT3-MMP IgG. Thus, in contrast to tube formation by hFMVECs, which largely depends on MT1-MMP, capillary-like tube formation by hEMVECs is, at least in part, regulated by MT3-MMP.

Therapeutic angiogenesis using vascular endothelial growth factor (VEGF) is considered a promising new therapy for patients with arterial obstructive disease. Clinical improvements observed consist of improved muscle function and regression of rest pain or angina. However, direct evidence for improved vascularization, as evaluated by angiography, is weak. In this study, we report an angiogenesis-independent effect of VEGF on ischemic skeletal muscle, ie, upregulation of myoglobin after VEGF treatment. Mice received intramuscular injection with adenoviral VEGF-A or either adenoviral LacZ or PBS as control, followed by surgical induction of acute hindlimb ischemia at day 3. At day 6, capillary density was increased in calf muscle of Ad.VEGF-treated versus control mice (P<0.01). However, angiographic score of collateral arteries was unchanged between Ad.VEGF-treated and control mice. More interestingly, an increase in myoglobin was observed in Ad.VEGF-treated mice. Active myoglobin was 1.5-fold increased in calf muscle of Ad.VEGF-treated mice (P< or =0.01). In addition, the number of myoglobin-stained myofibers was 2.6-fold increased in Ad.VEGF-treated mice (P=0.001). Furthermore, in ischemic muscle of 15 limb amputation patients, VEGF and myoglobin were coexpressed. Finally, in cultured C2C12 myotubes treated with rhVEGF, myoglobin mRNA was 2.8-fold raised as compared with PBS-treated cells (P=0.02). This effect could be blocked with the VEGF receptor tyrosine kinase inhibitor SU5416. In conclusion, we show that VEGF upregulates myoglobin in ischemic muscle both in vitro and in vivo. Increased myoglobin expression in VEGF-treated muscle implies an improved muscle oxygenation, which may, at least partly, explain observed clinical improvements in VEGF-treated patients, in the absence of improved vascularization.

Objective: Endovascular aneurysm repair is an alternative treatment of abdominal aortic aneurysm. The procedure is less invasive, and morbidity and most probably mortality are reduced. However, some problems, such as endoleakage, are yet to be resolved. Endoleakage can occur after graft migration, as a result of insufficient fixation of the stent graft. One cause is deficient healing between the aortic neck and the stent graft. We hypothesize that better healing, achieved by induction of vascular cell ingrowth into the graft material, results in better graft fixation. Previously we demonstrated ingrowth of neointima into the graft material if the stent graft is impregnated with a coat of basic fibroblast growth factor (bFGF), heparin, and collagen. In this study we evaluated healing with bFGF-heparin-collagen-coated stent grafts in vivo., Methods: In 4 pigs, 32 endovascular stent grafts, manufactured from standard Dacron and Gianturco Z-stents, were placed in the aorta. The stent grafts were impregnated with either bFGF-heparin containing collagen (n=16) or control collagen (n=16). After 4 and 8 weeks animals were killed, and ingrowth and healing of the stent grafts were macroscopically and electron microscopically evaluated., Results: After 8 weeks all bFGF-impregnated stent grafts demonstrated ingrowth of tissue and healing between the graft and the aorta, whereas the control nonimpregnated stent grafts showed no ingrowth. Microscopic evaluation demonstrated alpha-smooth muscle actin-positive cells, most probably smooth muscle cells or myofibroblasts, growing from the vascular wall through the graft material., Conclusion: A Dacron prosthesis impregnated with collagen, heparin, and bFGF induced graft healing in an in vivo pig model, in contrast to nonimpregnated stent grafts. This in vivo study confirms our previous findings in vitro. These results indicate that healing between Dacron and the aorta can be achieved, and suggest that type I endoleakage may be resolved by inducing healing between the aortic wall and the prosthesis with graft material containing growth factor.

Background: Toll-like receptor 4 (Tlr4) is the receptor for exogenous lipopolysaccharides (LPS). Expression of endogenous Tlr4 ligands, heat shock protein 60 (Hsp60) and extra domain A of fibronectin, has been observed in arthritic and oncological specimens in which matrix turnover is an important feature. In atherosclerosis, outward remodeling is characterized by matrix turnover and a structural change in arterial circumference and is associated with a vulnerable plaque phenotype. Since Tlr4 ligands are expressed during matrix turnover, we hypothesized that Tlr4 is involved in arterial remodeling., Methods and Results: In a femoral artery cuff model in the atherosclerotic ApoE3 (Leiden) transgenic mouse, Tlr4 activation by LPS stimulated plaque formation and subsequent outward arterial remodeling. With the use of the same model in wild-type mice, neointima formation and outward remodeling occurred. In Tlr4-deficient mice, however, no outward arterial remodeling was observed independent of neointima formation. Carotid artery ligation in wild-type mice resulted in outward remodeling without neointima formation in the contralateral artery. This was associated with an increase in Tlr4 expression and EDA and Hsp60 mRNA levels. In contrast, outward remodeling was not observed after carotid ligation in Tlr4-deficient mice., Conclusions: These findings provide genetic evidence that Tlr4 is involved in outward arterial remodeling, probably through upregulation of Tlr4 and Tlr4 ligands.

Objective: Endothelial cells play a pivotal role in vascular homeostasis. In this study, we investigated the function of the nerve growth factor-induced protein-B (NGFI-B) subfamily of nuclear receptors comprising the TR3 orphan receptor (TR3), mitogen-induced nuclear orphan receptor (MINOR), and nuclear orphan receptor of T cells (NOT) in endothelial cells., Methods and Results: The mRNA expression of TR3, MINOR, and NOT in atherosclerotic lesions was assessed in human vascular specimens. Each of these factors is expressed in smooth muscle cells, as described before, and in subsets of endothelial cells, implicating that they might affect endothelial cell function. Adenoviral overexpression of TR3 in cultured endothelial cells resulted in decreased [3H]thymidine incorporation, whereas a dominant-negative TR3 variant that inhibits the activity of endogenous TR3-like factors enhanced DNA synthesis. TR3 interfered with progression of the cell cycle by upregulating p27Kip1 and downregulating cyclin A, whereas expression levels of a number of other cell cycle-associated proteins remained unchanged., Conclusions: These findings demonstrate that TR3 is a modulator of endothelial cell proliferation and arrests endothelial cells in the G1 phase of the cell cycle by influencing cell cycle protein levels. We hypothesize involvement of TR3 in the maintenance of integrity of the vascular endothelium.

Adult angiogenesis, associated with pathologic conditions, is often accompanied by the formation of a fibrinous exudate. This temporary matrix consists mainly of fibrin but is intermingled with plasma proteins and collagen fibers. The formation of capillary structures in a fibrinous matrix in vivo was mimicked by an in vitro model, in which human microvascular endothelial cells (hMVECs) seeded on top of a fibrin-10% collagen matrix form capillarylike tubular structures after stimulation with basic fibroblast growth factor/tumor necrosis factor alpha (bFGF/TNF-alpha) or vascular endothelial growth factor (VEGF)/TNF-alpha. In the fibrin-collagen matrix the metalloproteinase inhibitor BB94 inhibited tubule formation by 70% to 80%. Simultaneous inhibition of plasmin and metalloproteinases by aprotinin and BB94 caused a nearly complete inhibition of tubule formation. Adenoviral transduction of tissue inhibitor of metalloproteinases 1 (TIMP-1) and TIMP-3 into endothelial cells revealed that TIMP-3 markedly inhibited angiogenesis, whereas TIMP-1 had only a minor effect. Immunohistochemical analysis showed the presence of matrix metalloproteinase 1 (MMP-1), MMP-2, and membrane-type 1 (MT1)-MMP, whereas MMP-9 was absent. The endothelial production of these MMPs was confirmed by antigen assays and real-time polymerase chain reaction (PCR). MT1-MMP mRNA was markedly increased in endothelial cells under conditions that induced tubular structures. The presence of MMP-1, MMP-2, and MT1-MMP was also demonstrated in vivo in the newly formed vessels of a recanalized arterial mural thrombus. These data suggest that MMPs, in particular MT-MMPs, play a pivotal role in the formation of capillarylike tubular structures in a collagen-containing fibrin matrix in vitro and may be involved in angiogenesis in a fibrinous exudate in vivo.

Matrix metalloproteinases (MMPs) are believed to be pivotal enzymes in the invasion of articular cartilage by synovial tissue in rheumatoid arthritis (RA). Here, we investigated the effects of gene transfer of tissue inhibitors of metalloproteinases (TIMPs) on the invasiveness of RA synovial fibroblasts (RASF) in vitro and in vivo. Adenoviral vectors (Ad) were used for gene transfer. The effects of AdTIMP-1 and AdTIMP-3 gene transfer on matrix invasion were investigated in vitro in a transwell system. Cartilage invasion in vivo was studied in the SCID mouse co-implantation model for 60 days. In addition, the effects of AdTIMP-1 and AdTIMP-3 on cell proliferation were investigated. A significant reduction in invasiveness was demonstrated in vitro as well as in vivo in both the AdTIMP-1- and AdTIMP-3-transduced RASF compared with untransduced SF or SF that were transduced with control vectors. in vitro, the number of invading cells was reduced to 25% (P<0.001) in the AdTIMP-1-transduced cells and to 13% (P<0.0001) in the AdTIMP-3-transduced cells (% of untransduced cells). Cell proliferation was significantly inhibited by AdTIMP-3 and, less, by AdTIMP-1. In conclusion, overexpression of TIMP-1 and TIMP-3 by Ad gene transfer results in a marked reduction of the invasiveness of RASF in vitro and in the SCID mouse model. Apart from the inhibition of MMPs, a reduction in proliferation rate may contribute to this effect. These results suggest that overexpression of TIMPs, particularly TIMP-3 at the invasive front of pannus tissue, may provide a novel therapeutic strategy for inhibiting joint destruction in RA.

Objective: One of the most life-threatening vascular diseases is rupture of an abdominal aneurysm. The conventional treatment is based on surgical reconstruction. An alternative treatment is endovascular aneurysm repair (EVAR). Despite many advantages, one of the problems of EVAR is endoleakage from deficient healing between the aortic neck and the fabric of the endograft. We hypothesize that better healing, achieved with induction of vascular cell ingrowth into the graft material, would lead to better graft healing., Methods: Both pig aorta and human normal and aneurysmal aortic wall were used for organ cultures. Various growth factors were evaluated for the potential to induce intimal hyperplasia (ie, platelet-derived growth factor, vascular endothelial growth factor, and basic fibroblast growth factor [bFGF]). After the most potent growth factor had been selected, a vascular prosthetic material (Dacron fabric) impregnated with collagen and heparin was incubated with this growth factor. Impregnated pieces of Dacron were fixated on top of the aortic organ cultures for study of ingrowth of the neointima formation into the graft material., Results: bFGF was the most potent growth factor to induce neointima in aortic organ cultures. The pieces of impregnated Dacron had a release of 5 ng/24 h of bFGF for a period of at least 28 days. With fixation on top of the aortic organ cultures, the impregnated Dacron was capable of inducing neointima formation and ingrowth of the neointima into the graft material after 28 days., Conclusion: We showed that a Dacron prosthesis impregnated with collagen, heparin, and bFGF is capable of inducing graft healing in our in vitro model, the aortic organ cultures of pig and human aortas. These results suggest that the problem of endoleakage with EVAR may be solved with a perfect proximal healing between the aortic wall and the prosthesis.

Intimal hyperplasia resulting from vascular injury remains a major obstacle in the long-term success of coronary artery bypass grafts. Inhibition of smooth muscle cell (SMC) proliferation using adenoviral gene transfer of cell cycle inhibitors resulted in reduced neointima formation in various animal models. However, little is known about the effect on human SMCs and neointima formation. Here we report the effects of infection with an adenoviral vector encoding a constitutively active form of the retinoblastoma gene (Ad. delta Rb) on proliferation of human saphenous vein SMCs (HSVSMCs) and neointima formation in organ cultures of human saphenous vein. Proliferation of SMCs was inhibited dose-dependently after infection with Ad. delta Rb. A near-total inhibition was found at an Ad. delta Rb concentration of 10(8) pfu/ml. Organ cultures of human saphenous vein segments were used to evaluate the effect of Ad. delta Rb infection on neointima formation and vein graft disease. Segments cultured for 4 weeks develop a neointima that is morphologically highly similar to early initimal lesions found in pathological vein grafts in vivo. Infection of saphenous vein segments with 2 x 10(9) pfu/ml Ad. delta Rb resulted in a 59% reduction of neointimal area when compared to uninfected counterparts, whereas infection with control adenovirus, Ad.LacZ, had no significant effect. The results of this study show that Ad. delta Rb gene transfer might be an efficient approach to prevent neointima formation in human saphenous vein grafts.

Proteases of the plasminogen activator (PA) and matrix metalloproteinase (MMP) system play an important role in smooth muscle cell (SMC) migration and neointima formation after vascular injury. Inhibition of either PAs or MMPs has previously been shown to result in decreased neointima formation in vivo. To inhibit both protease systems simultaneously, a novel hybrid protein, TIMP-1.ATF, was constructed consisting of the tissue inhibitor of metalloproteinase-1 (TIMP-1) domain, as MMP inhibitor, linked to the receptor-binding amino terminal fragment (ATF) of urokinase. By binding to the u-PA receptor this protein will not only anchor the TIMP-1 moiety directly to the cell surface, it will also prevent the local activation of plasminogen by blocking the binding of urokinase-type plasminogen activator (u-PA) to its receptor. Adenoviral expression of TIMP-1.ATF was used to inhibit SMC migration and neointima formation in human saphenous vein segments in vitro. SMC migration was inhibited by 65% in Ad.TIMP-1.ATF-infected cells. Infection with adenoviral vectors encoding the individual domains, Ad.TIMP-1 and Ad.ATF, reduced migration by 32% and 52%, respectively. Neointima formation in saphenous vein organ cultures infected with Ad.TIMP-1.ATF was inhibited by 72% compared with 42% reduction after Ad.TIMP-1 infection and 34% after Ad.ATF infection. These data show that binding of TIMP-1.ATF hybrid protein to the u-PA receptor at the cell surface strongly enhances the inhibitory effect of TIMP-1 on neointima formation in human saphenous vein cultures.

Background: Inflammation plays an important role in atherogenesis. The toll-like receptor 4 (TLR4) is the receptor for bacterial lipopolysaccharides and also recognizes cellular fibronectin and heat shock protein 60, endogenous peptides that are produced in response to tissue injury. To explore a possible role for this receptor in arterial obstructive disease, we determined the expression of TLR4 in the atherosclerotic arterial wall, including adventitia, and studied the effect of adventitial TLR4 activation on neointima formation in a mouse model., Methods and Results: Localization of TLR4 was studied in human atherosclerotic coronary arteries by immunohistochemistry and detected in plaque and adventitia. In the adventitia, not all TLR4-positive cells colocalized with macrophages. In primary human adventitial fibroblasts, expression of TLR4 was demonstrated by immunofluorescence, Western blot, and reverse transcriptase-polymerase chain reaction. Adding lipopolysaccharide to these fibroblasts induced activation of NF-kappaB and an increase of mRNAs of various cytokines. The effect of adventitial stimulation of TLR4 was studied in a mouse model. A peri-adventitial cuff was placed around the femoral artery. Application of lipopolysaccharide between cuff and artery augmented neointima formation induced by the cuff (intimal area+/-SEM, 9134+/-1714 versus 2353+/-1076 microm(2), P<0.01). In TLR4-defective mice, application of cuff and lipopolysaccharide resulted in a smaller neointima than in wild-type mice (intimal area, 3859+/-904 microm(2), P=0.02 versus wild type)., Conclusions: A functional TLR4 is expressed in human adventitial fibroblasts and macrophages. Adventitial TLR4 activation augmented neointima formation in a mouse model. These results provide evidence for a link between the immune receptor TLR4 and intimal lesion formation.

Vein grafts fail due to development of intimal hyperplasia and accelerated atherosclerosis. Many murine genetic models in which genes are overexpressed, deleted, or mutated have been introduced recently. Therefore, mouse models are very well suited to dissect the relative contribution of different genes in the development of accelerated atherosclerosis. In the present study, we evaluated whether accelerated atherosclerosis in human vein grafts could be mimicked in hypercholesterolemic APOE*3 Leiden transgenic mice. Venous bypass grafting was performed in the carotid artery in APOE*3 Leiden mice fed either a standard chow diet or a high cholesterol-rich diet for 4 weeks. At several time points (0 hour to 28 days), mice were euthanized and the morphology of the vein grafts was analyzed. In normocholesterolemic mice, vein graft thickening up to 10-fold original thickness, predominantly consisting of alpha-smooth muscle cell actin-positive cells, was observed after 28 days. In hypercholesterolemic mice, accelerated atherosclerosis with accumulation of lipid-loaded foam cells was observed within 7 days after surgery. This accelerated atherosclerosis progressed in time and resulted in significant increase in vein graft thickening up to 50 times original thickness with foam cell-rich lesions and calcification within 28 days after surgery. The atherosclerotic lesions observed in these murine grafts show high morphological resemblance with the atherosclerotic lesions observed in human vein grafts. This accelerated, diet-dependent induction of atherosclerotic-like lesions in murine vein grafts provides a valuable tool in evaluating the mechanisms of accelerated atherosclerosis and therapeutic interventions of vein graft disease.

Objective: Vein grafts fail because of the development of intimal hyperplasia and accelerated atherosclerosis. Placement of an external stent around vein grafts resulted in an inhibition of intimal hyperplasia in several animal studies. Here, we assess the effects of external stenting on accelerated atherosclerosis in early vein grafts in carotid arteries in hypercholesterolemic apolipoprotein E*3-Leiden transgenic mice., Methods and Results: Venous interposition grafting was performed in apolipoprotein E*3-Leiden mice fed standard chow or a highly cholesterol-rich diet for 4 weeks. After engraftment, external stents with different inner diameters (0.4 or 0.8 mm) were placed. In unstented vein grafts in hypercholesterolemic mice, thickening up to 50 times the original thickness, with foam cell-rich lesions, calcification, and necrosis, was observed within 28 days. The atherosclerotic lesions observed show high morphological resemblance to atherosclerotic lesions observed in human vein grafts. In stented vein grafts in hypercholesterolemic mice, no foam cell accumulation or accelerated atherosclerosis was observed. Compared with unstented vein grafts, stenting of vein grafts in a hypercholesterolemic environment resulted in a 94% reduction of vessel wall thickening. These effects were independent of stent size., Conclusions: Extravascular stent placement results in strong inhibition of accelerated vein graft atherosclerosis in hypercholesterolemic transgenic mice and thereby provides a perspective for therapeutic intervention in vein graft diseases.

Activin A alters the characteristics of human arterial smooth muscle cells (SMCs) toward a contractile, quiescent phenotype. We hypothesize that activin A may prevent SMC-rich neointimal hyperplasia. Here, we study the effect of adenovirus-mediated expression of activin A on neointima formation in vitro and in vivo. Human saphenous vein organ cultures, in which a neointima is formed spontaneously, were infected either with activin A- or lacZ-adenovirus. Activin A-overexpression reduces neointima formation by 78%, whereas no significant reduction was observed after control infection. In addition, the effect of activin A on neointima formation was assessed in vivo in mice with cuffed femoral arteries. In activin A adenovirus-infected mice (IV injection), neointimal hyperplasia is reduced by 77% compared with the SMC-rich neointima in mock-infected or in noninfected mice. Cultured human saphenous vein SMCs and murine aorta SMCs were incubated with activin A and an increased expression of SM22alpha and SM alpha-actin mRNA, and SM alpha-actin protein was demonstrated. Laser-capture microdissection on sections of cuffed murine arteries and subsequent real-time RT-PCR established in vivo induction of SM alpha-actin mRNA in the media of activin A-treated mice. In summary, activin A inhibits neointima formation in vitro and in vivo by preventing SMC dedifferentiation.

Since targeting of recombinant adenovirus vectors to defined cell types in vivo is a major challenge in gene therapy and vaccinology, we explored the natural diversity in human adenovirus tissue tropism. Hereto, we constructed a library of Ad5 vectors carrying fibers from other human serotypes. From this library, we identified vectors that efficiently infect human cells that are important for diverse gene therapy approaches and for induction of immunity. For several medical applications (prenatal diagnosis, artificial bone, vaccination, and cardiovascular disease), we demonstrate the applicability of these novel vectors. In addition, screening cell types derived from different species revealed that cellular receptors for human subgroup B adenoviruses are not conserved between rodents and primates. These results provide a rationale for utilizing elements of human adenovirus serotypes to generate chimeric vectors that improve our knowledge concerning adenovirus biology and widen the therapeutic window for vaccination and many different gene transfer applications.

The very low density lipoprotein receptor (VLDLR) has been shown to modulate cell migration and foam cell formation in vitro. This suggests a role for the VLDLR in vascular pathology associated with intimal thickening and atherogenesis. In the present paper both intimal thickening and atherosclerosis were studied using VLDLR knockout and transgenic mouse models. The role of the VLDLR in intimal thickening was established in an in vivo model for vascular injury. A non-restrictive cuff was placed around the femoral artery of VLDLR deficient (VLDLR-/-), heterozygous deficient (VLDLR+/-) and wild type (WT) mice. Intimal thickening was assessed after 3 weeks by determining the intima to media (I/M) volume ratio. Both VLDLR-/- (I/M ratio 42%) and VLDLR+/- (I/M ratio 40%) mice showed a significant increase as compared with WT littermates (I/M ratio 25%). The effect of VLDLR deficiency on atherosclerosis was examined in VLDLR-/- mice on an LDLR deficient (LDLR-/-) background. In addition, we assessed whether increased endothelial VLDLR expression levels affect atherosclerotic lesion formation. Therefore, atherosclerosis was studied in LDLR deficient mice that over express the VLDLR in endothelial cells (PVL, LDLR-/-). Both VLDLR deficiency and endothelial VLDLR over expression did not affect the atherosclerotic lesion size. Interestingly, VLDLR-/-, LDLR-/- mice showed a high incidence of necrosis in both fatty streaks and atherosclerotic plaques as compared with LDLR-/- mice (75 vs. 0% and 76 vs. 45%, respectively). In conclusion, deficiency for the VLDLR profoundly increased intimal thickening after vascular injury.

Background: The mesothelium has an important role in maintaining an adequate fibrinolytic capacity in the peritoneal cavity and thus in preventing the formation of fibrinous peritoneal adhesions by secreting the fibrinolytic enzyme tissue-type plasminogen activator (t-PA). The fibrinolytic activity of human mesothelial cells (HMCs) is counteracted by rapid uptake of t-PA via the low-density lipoprotein receptor-related protein (LRP). The 39 kD receptor-associated protein (RAP) is an inhibitor of binding of t-PA to LRP, but RAP itself is also rapidly degraded via LRP., Methods: Adenovirus-mediated RAP gene transfer technology was used to evaluate the effect of prolonged overexpression of RAP on t-PA accumulation in conditioned medium of HMCs under basal and inflammatory conditions., Results: Infection of HMCs with a recombinant adenovirus carrying the RAP cDNA resulted within one day in t-PA levels that were maximally twofold to threefold increased as compared with noninfected or adenovirus-beta-galactosidase-infected cells. Whereas upon prolonged incubation, t-PA levels in the conditioned medium of uninfected cells leveled off because of rapid uptake and degradation via LRP, t-PA concentrations in the medium of adenovirus-RAP-infected cells continued to increase, reaching fivefold control levels after 72 hours. The increased t-PA accumulation persisted for seven days and then slowly returned to control values over the next few weeks. In contrast, the production of a specific inhibitor of t-PA, plasminogen activator inhibitor-1 (PAI-1), was not affected by adenoviral RAP gene transfer. Northern blotting analysis showed that t-PA, PAI-1, and LRP mRNA concentrations were not changed after adenoviral infection, underlining that the elevated t-PA levels are the result of RAP-blocked uptake and degradation of t-PA rather than increased t-PA synthesis. RAP gene transfer also restored diminished fibrinolytic activity of cytokine-treated mesothelial cells., Conclusions: Adenovirus-mediated transfer of the RAP gene provides an efficient way of transiently increasing the fibrinolytic capacity of mesothelial cells.

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.

To identify improved adenovirus vectors for cardiovascular gene therapy, a library of adenovirus vectors based on adenovirus serotype 5 (Ad5) but carrying fiber molecules of other human serotypes, was generated. This library was tested for efficiency of infection of human primary vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Based on luciferase, LacZ, or green fluorescent protein (GFP) marker gene expression, several fiber chimeric vectors were identified that displayed improved infection of these cell types. One of the viruses that performed particularly well is an Ad5 carrying the fiber of Ad16 (Ad5.Fib16), a subgroup B virus. This virus showed, on average, 8- and 64-fold-increased luciferase activities on umbilical vein ECs and SMCs, respectively, compared to the parent vector. GFP and lacZ markers showed that approximately 3-fold (ECs) and 10-fold (SMCs) more cells were transduced. Experiments performed with both cultured SMCs and organ cultures derived from different vascular origins (saphenous vein, iliac artery, left interior mammary artery, and aorta) and from different species demonstrated that Ad5.Fib16 consistently displays improved infection in primates (humans and rhesus monkeys). SMCs of the same vessels of rodents and pigs were less infectable with Ad5.Fib16 than with Ad5. This suggests that either the receptor for human Ad16 is not conserved between different species or that differences in the expression levels of the putative receptor exist. In conclusion, our results show that an Ad5-based virus carrying the fiber of Ad16 is a potent vector for the transduction of primate cardiovascular cells and tissues.

Nitric oxide (NO) is involved in the regulation of SMC proliferation during intimal hyperplasia as has been shown by the inhibitory effect on intimal hyperplasia of adenovirus-mediated ceNOS overexpression in injured arteries in pig. Good assays to quantify the NO-producing enzymes, i.e., NO synthases (NOS), are essential to analyze the mechanism of action of NO in this process. We have developed novel flow cytometric assays for the simultaneous detection of NOS-3 protein, using NOS-3 specific antibodies, and NO production using 4,5-diaminofluorescein-diacetate (DAF-2/DA). The presence of NOS-3 protein and NO production is demonstrated on human A549 and HepG2 cells infected with a NOS-3 adenovirus (Ad.NOS-3). A comparative study showed that the flow cytometric assays are equally sensitive as Western blot analysis, the citrulline assay, or the Sievers assay. On human endothelial and SMC, NOS-3 protein and NO production were simultaneously detected with the assays, both under basal conditions and after Ad.NOS-3transduction. Simultaneous analysis of NOS-3 protein and NO production, made possible by the here-described novel flow cytometric assays, is of significant value to those investigating NOS-3 and NO., (Copyright 2001 Academic Press.)

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.

Smooth muscle cell migration plays a role in the development of intimal hyperplasia. Given the established role of the plasminogen activation system in cell migration, an approach to therapy is to overexpress an inhibitor of plasmin. Therefore, an adenoviral vector was constructed encoding the hybrid protein ATF.BPTI, which contains the active domain of bovine pancreas trypsin inhibitor (BPTI), fused to ATF, the amino terminal fragment or receptor-binding domain of u-PA. Adenoviral vectors expressing ATF and BPTI individually were also constructed, and a fourth vector was constructed encoding ATF.BPTI linked by an internal ribosomal entry site to Green Fluorescent Protein (ABIG). Both the expression and functionality of the recombinant proteins were established in human vascular smooth muscle cells. Adenoviral gene transfer of ATF.BPTI inhibited SMC migration more efficiently than the expression of ATF or BPTI individually. Expression of ABIG resulted in the co-expression of ATF.BPTI and Green Fluorescent Protein, thereby providing a tool to monitor transfection efficiency and the behavior of the transfected cells.

Intimal hyperplasia after vascular injury is usually studied in animal models with healthy, normocholesterolemic animals. Here, we assess the effect of diet-induced hypercholesterolemia on the induction of intimal hyperplasia in ApoE*3Leiden mice. A nonconstrictive polyethylene cuff was placed around the femoral artery of ApoE3*Leiden mice fed a highly cholesterol-rich diet, a mildly cholesterol-rich diet, or a chow diet for 4 weeks. Diets were continued after cuff placement until euthanization. At several time points (1 to 14 days), mice were euthanized and the intimal hyperplasia in the cuffed arteries was analyzed. In mice fed a chow diet, a 2- to 4-cell-layer-thick intima, predominantly consisting of alpha smooth muscle cell actin-positive cells, was observed after 14 days. A mildly cholesterol-rich diet (mean plasma-cholesterol level, 10.5 mmol/L) resulted in a 2.7-fold increase of total intimal area, and a highly cholesterol-rich diet (mean plasma cholesterol level 28. 6 mmol/L), in a 7.8-fold increase. In the high-cholesterol group, the intima consisted predominantly of lipid-loaded foam cells and alpha smooth muscle cell actin-positive cells. Foam cell accumulation could be observed by as early as 3 days, resulting in a near-total occlusion of the lumen after 14 days. Hypercholesterolemia resulted in a rapid, cholesterol-dependent induction of foam cell-rich intimal hyperplasia in cuffed femoral arteries of ApoE*3Leiden mice. In conclusion, the present data show that the combination of a local (cuff placement) and a systemic (hypercholesterolemic) risk factor of atherosclerosis results in a rapid induction (within 14 days) of atherosclerotic-like lesions in ApoE*3Leiden mice.

Objective: Joint destruction in rheumatoid arthritis (RA) is a result of degradation and invasion of the articular cartilage by the pannus tissue. The present study was undertaken to examine the role of the plasminogen activation system in cartilage degradation and invasion by synovial fibroblasts and investigate a novel gene therapeutic approach using a cell surface-targeted plasmin inhibitor (ATF.BPTI)., Methods: Adenoviral vectors were used for gene transfer. The effects of ATF.BPTI gene transfer on RA synovial fibroblast-dependent cartilage degradation were studied in vitro, and cartilage invasion was studied in vivo in the SCID mouse coimplantation model., Results: The results indicate that cartilage matrix degradation by rheumatoid synovial fibroblasts is plasmin mediated and depends on urokinase-type plasminogen activator for activation. Targeting plasmin inhibition to the cell surface of the fibroblasts by gene transfer of a cell surface-binding plasmin inhibitor resulted in a significant reduction of cartilage matrix degradation in vitro and of cartilage invasion in vivo. Compared with uninfected rheumatoid synovial fibroblasts, the mean +/-SEM cartilage degradation in vitro was reduced to 87.9+/-0.9% after LacZ gene transfer versus a reduction to 24.0+/-1.6% after ATF.BPTI gene transfer (P<0.0001). The mean +/- SEM in vivo cartilage invasion score was 3.1+/-0.4 in the control-transduced fibroblasts and 1.8+/-0.4 in the ATF.BPTI-transduced fibroblasts (P<0.05)., Conclusion: These results indicate a role of the plasminogen activation system in synovial fibroblast-dependent cartilage degradation and invasion in RA, and demonstrate an effective way to inhibit this by gene transfer of a cell surface-targeted plasmin inhibitor.

Recent reports suggest that elevated levels of plasminogen activator inhibitor-1 (PAI-1) may contribute to tumour progression. The studies reported here were designed to help elucidate PAI-1's contribution to the invasive and migratory phenotype. Antibodies to PA-1 dose-dependently, and significantly, inhibited the invasive and migratory potential of human HT1080 fibrosarcoma cells, as did an antibody to uPA and the plasmin inhibitor aprotinin. Invasion of the human melanoma cell line, BLM, was also attenuated by the anti-PAI-1 monoclonal antibody MAI-12. The non-invasive human melanoma cell line, IF6, which does not express uPA, provided further confirmation of PAI-1 and uPA's role as, upon transfection with uPA, this cell line attained an invasive phenotype, which was again attenuated by MAI-12. Although antibodies to PAI-1 did not affect the adhesion of HT1080 cells to vitronectin, the antibody to uPA reduced their attachment. Addition of exogenous PAI-1, however, prevented HT1080 cell adhesion (IC50 180 nM) and promoted cell detachment from vitronectin. Furthermore melanoma cells transfected with a uPA variant, which had an impaired interaction with PAI-1, were not invasive and had impaired binding to vitronectin. These data highlight the importance of a balanced proteolysis and suggest an additional role for PAI-1 distinct from its role in proteolysis. These data also suggest that uPA and PAI-1 may co-operate in the migratory process by respectively facilitating the attachment to, and subsequent detachment from, vitronectin in the extracellular matrix. These results support the clinical findings and indicate that modulation of PAI-1 activity may be of therapeutic benefit for the treatment of cancer.