Antisense basic fibroblast growth factor gene transfer reduces neointimal thickening after arterial injury

Epac1 deficiency inhibits basic fibroblast growth factor-mediated vascular smooth muscle cell migration

Vascular smooth muscle cell (VSMC) migration and the subsequent intimal thickening play roles in vascular restenosis. We previously reported that an exchange protein activated by cAMP 1 (Epac1) promotes platelet-derived growth factor (PDGF)-induced VSMC migration and intimal thickening. Because basic fibroblast growth factor (bFGF) also plays a pivotal role in restenosis, we examined whether Epac1 was involved in bFGF-mediated VSMC migration. bFGF-induced lamellipodia formation and migration were significantly decreased in VSMCs obtained from Epac1-/- mice compared to those in Epac1+/+-VSMCs. The bFGF-induced phosphorylation of Akt and glycogen synthase kinase 3β (GSK3β), which play a role in bFGF-induced cell migration, was attenuated in Epac1-/--VSMCs. Intimal thickening induced by the insertion of a large wire was attenuated in Epac1-/- mice, and was accompanied by the decreased phosphorylation of GSK3β. These data suggest that Epac1 deficiency attenuates bFGF-induced VSMC migration, possibly via Akt/GSK3β pathways.

TUG1 knockdown ameliorates atherosclerosis via up-regulating the expression of miR-133a target gene FGF1

BACKGROUND

Long non-coding RNAs (lncRNAs) have been revealed to participate in the pathological events associated with atherosclerosis. However, the exact role of lncRNA taurine-up-regulated gene 1 (TUG1) and its possible molecular mechanism in atherosclerosis remain unidentified.

METHODS

High-fat diet (HFD)-treated ApoE^-/- mice were used as an in vivo model of atherosclerosis. Ox-LDL-induced macrophages and vascular smooth muscle cells (VSMCs) were employed as cell models of atherosclerosis. qRT-PCR was performed to detect the expression of TUG1 and miR-133a. Serum levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were analyzed by commercially available enzyme kits. Oil red O and hematoxylin and eosin (H&E) staining were conducted to examine atherosclerotic lesion. Luciferase reporter assay combined with RNA immunoprecipitation (RIP) was applied to confirm the interaction between TUG1, miR-133a and FGF1. Cell proliferation ability was determined by Cell Counting Kit-8 (CCK-8) assay and trypan blue dye exclusion test. Cell apoptosis was evaluated with TUNEL assay. Expression and production of inflammatory cytokines was measured with western blot and ELISA analysis.

RESULTS

TUG1 expression was up-regulated in HFD-treated ApoE^-/- mice, as well as in ox-LDL-induced RAW264.7 and MOVAS cells. TUG1 knockdown inhibited hyperlipidemia, decreased inflammatory response, and attenuated atherosclerotic lesion in HFD-treated ApoE^-/- mice. TUG1 could function as a molecular sponge of miR-133a to suppress its expression. TUG1 overexpression accelerated cell growth, improved inflammatory factor expression, and inhibited apoptosis in ox-LDL-stimulated RAW264.7 and MOVAS cells, while this effect was abated after transfection with miR-133 mimic. Moreover, fibroblast growth factor 1 (FGF1) was identified as a direct target of miR-133a. Restored expression of FGF1 overturned the effect of miR-133a on cell proliferation, inflammatory factor secretion and apoptosis in ox-LDL-treated RAW264.7 and MOVAS cells. Finally, TUG1 was revealed to up-regulate FGF1 expression by sponging miR-133a.

CONCLUSION

TUG1 knockdown ameliorates atherosclerosis by modulating FGF1 via miR-133a, raising the possibility of targeting TUG1 as an atheroprotective therapeutic strategy.

Gene Therapy for the Extension of Vein Graft Patency: A Review

The mainstay of treatment for long-segment small-vessel chronic occlusive disease not amenable to endovascular intervention remains surgical bypass grafting using autologous vein. The procedure is largely successful and the immediate operative results almost always favorable. However, the lifespan of a given vein graft is highly variable, and less than 50% will remain primarily patent after 5 years. The slow process of graft malfunction is a result of the vein's chronic maladaptive response to the systemic arterial environment, its primary component being the uncontrolled proliferation of vascular smooth muscle cells (SMCs). It has recently been suggested that this response might be attenuated through pre-implantation genetic modification of the vein, so-called gene therapy for the extension of vein graft patency. Gene therapy seems particularly well suited for the prevention or postponement of vein graft failure since: (1) the stimulation of SMC proliferation appears to largely be an early and transient process, matching the kinetics of current gene transfer technology; (2) most veins are relatively normal and free of disease at the time of bypass allowing for effective gene transfer using a variety of systems; and (3) the target tissue is directly accessible during operation because manipulation and irrigation of the vein is part of the normal workflow of the surgical procedure. This review briefly summarizes the current knowledge of the incidence and basic mechanisms of vein graft failure, the vector systems and molecular targets that have been proposed as possible pre-treatments, the results of experimental genetic modification of vein grafts, and the few available clinical studies of gene therapy for vascular proliferative disorders.

Re-Endothelialization Study on Endovascular Stents Seeded by Endothelial Cells through Up- or Downregulation of VEGF

We studied the effects of gene transfection of endothelial cells with vascular endothelial growth factor (VEGF) on re-endothelialization and inhibition of in-stent restenosis. Transfected endothelial cells (ECs) exposed to different VEGF levels were seeded on a stent surface for evaluation in vitro. VEGF121(++) ECs and VEGF121(--) ECs were established using lentiviral-mediated HUVECs transfection. VEGF RNA transcription level and VEGF protein expression were detected by qPCR, Western blot, and ELISA. Methyl thiazolyl tetrazolium (MTT) assay, wound healing assay, and in vitro HUVEC tube formation assay showed that VEGF overexpression promoted cell proliferation, migration, and endothelial capillary-like tube formation. Downregulation of VEGF expression inhibited these activities. Using a rotational culturing system, cells tightly adhered on the stent surface. Stents seeded with transfected ECs at different VEGF levels were implanted in abdominal aortas of New Zealand white rabbits to study re-endothelialization and inhibition of in-stent restenosis. Stents with cells exposed to excess VEGF expression were almost completely covered with cells after stent implantation for 1 week (w). In the VEGF interference group this process was delayed over 4 w due to RNAi-mediated silencing of VEGF. Cryosectioning after 12 w showed that stents seeded with HUVECs exposed to excess VEGF expression significantly reduced the neointima area and stenosis when compared with bare metal stents and stents from the VEGF interference group. Transgenic HUVECs were not found in tissues of experimental animals. Furthermore, cells from these tissues were similar to those from normal tissue. In conclusion, VEGF-mediated endothelialization was found. Furthermore, ECs exposed to VEGF overexpression reduced neointimal hyperplasia, promoted endothelialization, and reduced in-stent restenosis.

MicroRNA-195 regulates vascular smooth muscle cell phenotype and prevents neointimal formation

AIMS

Proliferation and migration of vascular smooth muscle cells (VSMCs) can cause atherosclerosis and neointimal formation. MicroRNAs have been shown to regulate cell proliferation and phenotype transformation. We discovered abundant expression of microRNA-195 in VSMCs and conducted a series of studies to identify its function in the cardiovascular system.

METHODS AND RESULTS

MicroRNA-195 expression was initially found to be altered when VSMCs were treated with oxidized low-density lipoprotein (oxLDL) in a non-replicated microRNA array experiment. Using cellular studies, we found that microRNA-195 reduced VSMC proliferation, migration, and synthesis of IL-1β, IL-6, and IL-8. Using bioinformatics prediction and experimental studies, we showed that microRNA-195 could repress the expression of Cdc42, CCND1, and FGF1 genes. Using a rat model, we found that the microRNA-195 gene, introduced by adenovirus, substantially reduced neointimal formation in a balloon-injured carotid artery. In situ hybridization confirmed the presence of microRNA-195 in the treated arteries but not in control arteries. Immunohistochemistry experiments showed abundant Cdc42 in the neointima of treated arteries.

CONCLUSIONS

We showed that microRNA-195 plays a role in the cardiovascular system by inhibiting VSMC proliferation, migration, and proinflammatory biomarkers. MicroRNA-195 may have the potential to reduce neointimal formation in patients receiving stenting or angioplasty.

The impact of vascular endothelial growth factor-transfected human endothelial cells on endothelialization and restenosis of stainless steel stents

OBJECTIVES

The purpose of this study was to investigate the effects of gene transfection of endothelial cells with vascular endothelial growth factor (VEGF) on re-endothelialization and inhibiting in-stent restenosis.

METHODS

Stents coated with human umbilical vein endothelial cells (HUVECs) transfected with VEGF(121) were studied both in vitro and in vivo. In vitro studies were performed using a homemade extracorporeal circulation system. In vivo studies were performed using the rabbit abdominal aorta model.

RESULTS

In vitro studies confirmed that VEGF(121)-transfected cells adhered on the surface of stainless steel stents with over 90% of the surface covered within 24 hours of seeding. In vivo results showed that VEGF(121)-transfected HUVECs-coated stents were covered with seeding cells after implanting, and almost completely covered with cells after stent implantation for 1 week. In contrast, the non-endothelialized areas of bare metal stents and glutin/poly-L-lysine-coated stents were covered at 4 weeks, and the monolayers of cells were not observed, but fragile neointima was found on the surface. After 12 weeks, VEGF(121)-transfected HUVECs-coated stents significantly reduced the neointima area (0.78 ± 0.03 mm(2)) and stenosis (15.69 ± 2.61%) as compared with those for bare metal stents (neointima area = 2.26 ± 0.67 mm(2); the percentage of stenosis = 47.55 ± 7.10%;P < .01) and glutin/poly-L-lysine-coated stents (neointima area = 1.40 ± 0.37 mm(2); the percentage of stenosis = 31.37 ± 8.18%;P < .01).

CONCLUSION

In this small animal study, VEGF transfected human endothelial cells, when coated on stainless steel stents, reduce neointimal hyperplasia, promote endothelialization, and reduce in-stent restenosis. Additional studies with this technology are necessary to determine its ultimate utility in improving stents performance.

Role of the soluble pattern recognition receptor PTX3 in vascular biology

Pentraxins act as soluble pattern recognition receptors with a wide range of functions in various pathophysiological conditions. The long-pentraxin PTX3 shares the C-terminal pentraxin-domain with short-pentraxins C-reactive protein and serum amyloid P component and possesses an unique N-terminal domain. These structural features suggest that PTX3 may have both overlapping and distinct biological/ligand recognition properties when compared to short-pentraxins. PTX3 serves as a mechanism of amplification of inflammation and innate immunity. Indeed, vessel wall elements produce high amounts of PTX3 during inflammation and the levels of circulating PTX3 increase in several pathological conditions affecting the cardiovascular system. PTX3 exists as a free or extracellular matrix-associated molecule and it binds the complement fraction C1q. PTX3 binds also apoptotic cells and selected pathogens, playing a role in innate immunity processes. In endothelial cells and macrophages, PTX3 upregulates tissue factor expression, suggesting its action as a regulator of endothelium during thrombogenesis and ischaemic vascular disease. Finally, PTX3 binds the angiogenic fibroblast growth factor-2, thus inhibiting its biological activity. Taken together, these properties point to a role for PTX3 during vascular damage, angiogenesis, atherosclerosis, and restenosis.

Basic fibroblast growth factor (FGF-2): the high molecular weight forms come of age

After over thirty years from its discovery, research on basic fibroblast growth factor (FGF-2) keeps revealing new aspects of the complexity of its gene expression as it evolved in the eukaryotic organisms. The discovery of multiple forms of FGF-2 generated by alternative translation from AUG and non-canonical CUG codons on the same mRNA transcript has led to the characterization of a low molecular weight (LMW) FGF-2 form and various high molecular weight (HMW) forms (four in humans). In this review, we discuss the biochemical features and biological activities of the different FGF-2 forms. In particular, we focus on the properties that are unique to the HMW forms and its biological functions.

Gene therapy for restenosis: biological solution to a biological problem

Coronary artery disease remains a significant health threat afflicting millions of individuals worldwide. Despite the development of a variety of technologies and catheter based interventions, post-procedure restenosis is still a significant concern. Gene therapy has emerged as a promising approach aimed at modification of cellular processes that give rise to restenosis. When juxtaposed alongside the failure of traditional pharmacotherapeutics to eliminate restenosis, gene therapy has engendered great expectations for cubing coronary restenosis. In this review we have discussed an overview of gene therapy approaches that hve been utilized to reduce restenosis in preclinical and clinical studies, current status of anti-restenosis gene therapy and perspectives on its future application. For brevity, we have limited our discussion on anti-restenosis gene therapy to the introduction of a nucleic acid to the cell, tissue, organ or organism in order to give rise to the expression of a protein, the function of which will confer therapeutic effect. For the purpose of this review, we have focused ou discussion on two relevant anti-restenosis strategies, anti-proliferative and pro-endothelialization.

Fibroblast growth factor-2 expression is altered in lambs with increased pulmonary blood flow and pulmonary hypertension

A lamb model of pulmonary hypertension, developed by inserting an aortopulmonary vascular graft (shunt), displays vascular remodeling and increased pulmonary blood flow characteristic of children with congenital heart disease. The purpose of this study was to determine whether expression of fibroblast growth factor-2 (FGF-2), a smooth muscle cell mitogen, is altered in shunt lambs. FGF-2 mRNA and protein levels were increased in lung tissue extracts from shunt lambs at 4 wk of age relative to age-matched controls (p < 0.05). FGF-2 protein levels were also increased in the pulmonary arteries and serum of shunt lambs (p < 0.05). Pulmonary arterial smooth muscle cells (PASMC) and endothelial cells (PAEC) were isolated from 4 wk-old lambs and subjected to cyclic stretch and laminar shear stress to mimic increased pulmonary blood flow. Stretch and shear increased FGF-2 promoter activity, and intracellular and extracellular FGF-2 protein levels in both cell types (p < 0.05). Exogenous FGF-2 stimulated PASMC proliferation at levels detected in the extracellular medium of sheared cells (p < 0.05). Elevated FGF-2 signaling by PASMC and PAEC exposed to increased pulmonary blood flow may play a role in the pulmonary vascular remodeling associated with the shunt model of pulmonary hypertension secondary to congenital heart disease.

The effect of intracoronary fibroblast growth factor-2 on restenosis after primary angioplasty or stent placement in a pig model of atherosclerosis

BACKGROUND

Therapeutic angiogenesis, if combined with primary percutaneous transluminal coronary angioplasty or stent placement, could improve the outcome of patients suffering from multifocal coronary disease.

HYPOTHESIS

Because of the concern that angiogenic growth factors might promote restenosis, we studied the effect of a single intracoronary administration of recombinant fibroblast growth factor (rFGF)-2 on restenosis after balloon angioplasty and stent placement in a pig model of coronary atherosclerosis.

METHODS

In 24 Yucatan minipigs, coronary lesions were induced by arterial injury and 3 months of atherogenic diet. After 3 months, repeat catheterization was performed with balloon dilation or stent placement at the injured sites, with a follow-up of 6 weeks. Results were monitored using quantitative angiography, intravascular ultrasound (IVUS), and histomorphometry.

RESULTS

Intracoronary rFGF-2 2 microg/kg did not affect neointima formation or remodeling in this model. A small but significant aggravation of late lumen loss was observed in the reference segments of the rFGF-2-treated group. Angiographic and echographic late lumen loss, intimal hyperplasia, and arterial remodeling, as well as histologic neointima were all similar in the rFGF-2- and the vehicle-treated group. Confirming earlier studies from our group and those of others, stented arteries compared with balloon-dilated arteries had increased angiographic late lumen loss, a trend toward increased intimal hyperplasia and decreased remodeling.

CONCLUSION

We conclude that rFGF-2 does not aggravate restenosis after balloon dilation or stenting in this pig model of coronary atherosclerosis. Future combinations of angioplasty and therapeutic angiogenesis in a single session should be pursued as a feasible and safe strategy.

Gene deletion of NF-kappaB p105 enhances neointima formation in a mouse model of carotid artery injury

The role of nuclear factor kappa-B (NF-kappaB) p105 for vascular inflammatory gene expression and neointima formation after arterial injury was studied. Mice carotid arteries were injured by ligation. Vascular NF-kappaB activation was monitored using a NF-kappaB luciferase reporter mouse. Mice with gene deletion of the NF-kappaB p105 subunit (p50 precursor) and the corresponding wild types were assessed for vascular gene expression and neointimal hyperplasia. NF-kappaB was activated in the injured vessel wall in wild type mice, and this was accompanied by increased expression of the proinflammatory genes tumor necrosis factor alpha, interleukin 1 beta, and inducible nitric oxide synthase. In contrast, NF-kappaB p105 knockout mice had reduced expression of the inflammatory genes and enhanced neointima formation four weeks after ligation. Basic fibroblast growth factor (bFGF) gene expression increased after arterial ligation. A higher percentage of bFGF positive cells were found in lesions from NF-kappaB p105 knock out mice. These data indicate that the p105 subunit of NF-kappaB plays an essential role in vascular healing, and defects in NF-kappaB p105 promote neointima hyperplasia.

Pentraxin 3 Inhibits Fibroblast Growth Factor 2–Dependent Activation of Smooth Muscle Cells In Vitro and Neointima Formation In Vivo

Objective— The fibroblast growth factor (FGF)/FGF receptor system plays an important role in smooth muscle cell (SMC) activation. Long-pentraxin 3 (PTX3) is a soluble pattern recognition receptor with non-redundant functions in inflammation and innate immunity. PTX3 is produced by different cell types of the vessel wall, including SMCs. PTX3 binds FGF2 and inhibits its angiogenic activity on endothelial cells. We investigated the capacity of PTX3 to affect FGF2-dependent SMC activation in vitro and in vivo.

Methods and Results— When added to human coronary artery SMCs, human PTX3 inhibits cell proliferation driven by endogenous FGF2 and the mitogenic and chemotactic activity exerted by exogenous recombinant FGF2. Accordingly, PTX3 prevents 125 I-FGF2 interaction with FGF receptors on the same cells. Also, PTX3 overexpression after recombinant adeno-associated virus- PTX3 gene transfer inhibits human coronary artery SMC proliferation and survival promoted by FGF2 in vitro. Consistently, a single local endovascular injection of recombinant adeno-associated virus- PTX3 gene inhibits intimal thickening after balloon injury in rat carotid arteries.

Conclusions— PTX3 is a potent inhibitor of the autocrine and paracrine stimulation exerted by FGF2 on SMCs. Local PTX3 upregulation may modulate SMC activation after arterial injury.

Intratumoural administration of dendritic cells: hostile environment and help by gene therapy

Like paratroopers in special operations, dendritic cells (DCs) can be deployed behind the enemy borders of malignant tissue to ignite an antitumour immune response. 'Cross-priming T cell responses' is the code name for their mission, which consists of taking up antigen from transformed cells or their debris, migrating to lymphoid tissue ferrying the antigenic cargo, and meeting specific T cells. This must be accomplished in such an immunogenic manner that specific T lymphocytes would mount a robust enough response as to fully reject the malignancy. To improve their immunostimulating activity, local gene therapy can be very beneficial, either by transfecting DCs with genes enhancing their performance, or by preparing tumour tissue with pro-inflammatory mediators. In addition, endogenous DCs from the tumour host can be attracted into the malignant tissue following transfection of certain chemokine genes into tumour cells. On their side, tumour stroma and malignant cells set up a hostile immunosuppressive environment for artificially released or attracted DCs. This milieu is usually rich in transforming growth factor-beta, vascular endothelial growth factor, and IL-10, -6 and -8, among other substances that diminish DC performance. Several molecular strategies are being devised to interfere with the immunosuppressive actions of these substances and to further enhance the level of anticancer immunity achieved after artificial release of DCs intratumourally.

PDGF-BB induces vascular smooth muscle cell expression of high molecular weight FGF-2, which accumulates in the nucleus

Basic fibroblast growth factor (FGF-2) and platelet-derived growth factor (PDGF) are implicated in vascular remodeling secondary to injury. Both growth factors control vascular endothelial and smooth muscle cell proliferation, migration, and survival through overlapping intracellular signaling pathways. In vascular smooth muscle cells PDGF-BB induces FGF-2 expression. However, the effect of PDGF on the different forms of FGF-2 has not been elucidated. Here, we report that treatment of vascular aortic smooth muscle cells with PDGF-BB rapidly induces expression of 20.5 and 21 kDa, high molecular weight (HMW) FGF-2 that accumulates in the nucleus and nucleolus. Conversely, PDGF treatment has little or no effect on 18 kDa, low-molecular weight FGF-2 expression. PDGF-BB-induced upregulation of HMW FGF-2 expression is controlled by sustained activation of extracellular signal-regulated kinase (ERK)-1/2 and is abolished by actinomycin D. These data describe a novel interaction between PDGF-BB and FGF-2, and indicate that the nuclear forms of FGF-2 may mediate the effect of PDGF activity on vascular smooth muscle cells.

Vascular injury induces expression of periostin: implications for vascular cell differentiation and migration

OBJECTIVE

Periostin mRNA is among the most strongly upregulated transcripts in rat carotid arteries after balloon injury. The goal of the present study was to gain insight into the significance of periostin in the vasculature.

METHODS AND RESULTS

Periostin expression after injury was localized to smooth muscle cells of the neointima and the adventitia. The expression of periostin in smooth muscle cells in vitro was not regulated by cytokines such as fibroblast growth factor-2 (FGF-2). In contrast, stimulation of MC3T3-E1 osteoblastic cells, NIH3T3 fibroblasts, or mesenchymal C3H10T1/2 cells with FGF-2 reduced periostin mRNA levels to <5% of controls, whereas conversely bone morphogenetic protein-2 (BMP-2) increased periostin mRNA levels. Periostin expression was induced and maintained during retinoic acid-induced smooth muscle cell differentiation in A404 cells. In addition, overexpression of periostin in C3H10T1/2 cells caused an increase in cell migration that could be blocked with an anti-periostin antibody.

CONCLUSIONS

Periostin expression is associated with smooth muscle cell differentiation in vitro and promotes cell migration. Unlike other mesenchymally derived cell lines, periostin expression is not regulated by FGF-2 in smooth muscle cells. This distinction may be useful in discriminating smooth muscle and fibroblast lineages.

Copper chelation represses the vascular response to injury

The induction of an acute inflammatory response followed by the release of polypeptide cytokines and growth factors from peripheral blood monocytes has been implicated in mediating the response to vascular injury. Because the Cu2+-binding proteins IL-1alpha and fibroblast growth factor 1 are exported into the extracellular compartment in a stress-dependent manner by using intracellular Cu2+ to facilitate the formation of S100A13 heterotetrameric complexes and these signal peptideless polypeptides have been implicated as regulators of vascular injury in vivo, we examined the ability of Cu2+ chelation to repress neointimal thickening in response to injury. We observed that the oral administration of the Cu2+ chelator tetrathiomolybdate was able to reduce neointimal thickening after balloon injury in the rat. Interestingly, although immunohistochemical analysis of control neointimal sections exhibited prominent staining for MAC1, IL-1alpha, S100A13, and the acidic phospholipid phosphatidylserine, similar sections obtained from tetrathiomolybdate-treated animals did not. Further, adenoviral gene transfer of the IL-1 receptor antagonist during vascular injury also significantly reduced the area of neointimal thickening. Our data suggest that intracellular copper may be involved in mediating the response to injury in vivo by its ability to regulate the stress-induced release of IL-1alpha by using the nonclassical export mechanism employed by human peripheral blood mononuclear cells in vitro.

Applied gene therapy in preclinical models of vascular injury

Atherosclerosis remains the major cause of morbidity and mortality in Western countries. Atherothrombotic complications, including vascular occlusions and severe narrowing of nutrient blood vessels in the cerebral, coronary, or peripheral circulation, usually require invasive revascularization strategies. As molecular mediators contributing to these complications are being identified in more representative experimental injury models, and as gene transfer platforms and vectors acquire improved safety and efficacy profiles, there is ground for cautious optimism that gene-based interventions will likely reduce the clinical burden of these diseases. Increased generation of reactive oxygen species in diseased atherosclerotic vessels has been implicated in vasospasm, exaggerated neointima formation, and enhanced thrombosis. Ex vivo pressurized vascular gene transfer in venous bypass grafts using antisense oligonucleotides directed against cell-cycle control genes can modify the venous graft's phenotype and confer clinical benefit with improved long-term graft survival. Alternatively, percutaneous intra-arterial gene transfer is feasible, but at relatively low transgene expression levels. Although this may suffice in the case of secreted gene products with marked paracrine or bystander effects, including nitric oxide synthase and heme oxygenase-1, drug- and gene-eluting stents may provide the preferred future vehicle for well-controlled, quantifiable, and safe vascular gene transfer. Continued efforts to improve gene transfer technology in diseased human vessels and to increase our understanding of molecular targets are required before the full therapeutic potential of vascular gene therapy can be realized.

Antisense basic fibroblast growth factor alters the time course of mitogen-activated protein kinase in arterialized vein graft remodeling

PURPOSE

Neointimal hyperplasia (NIH) is complete by 3 weeks in rabbit vein grafts implanted into the arterial circulation. Activation of the mitogen-activated protein kinase (MAPK) family of protein kinases is thought to be critical in remodeling events such as cellular proliferation, differentiation, and migration, as found in NIH. We previously demonstrated that antisense basic fibroblast growth factor (ASbFGF) inhibited the synthesis of basic fibroblast growth factor (bFGF) in the balloon injury model of NIH. We examined the effect of ASbFGF on NIH and the time course of MAPK, extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal protein kinase (JNK), and p38 kinase activation in arterialized vein grafts.

METHODS

Carotid interposition of a vein bypass graft was performed in 75 New Zealand White rabbits. Segments of the external jugular vein were transfected with a replication-deficient adenovirus containing the messenger RNA sequence for rat ASbFGF at 1 x 10(10) plaque-forming units per milliliter; control animals were given phosphate-buffered saline solution (PBS) alone. Rabbits were killed at 30 minutes, 4 days, 7 days, and 21 days (n = 8). Four grafts in each group were fixed with formalin and embedded in paraffin, then processed with elastin-collagen and hematoxylin-eosin stains. The other four grafts were individually frozen, and total protein was extracted. Phosphorylation of MAPK, ERK1/2, JNK, and p38, was determined with Western blot analysis and immunohistochemistry. Groups were compared with analysis of variance.

RESULTS

The thickness of neointima in the PBS group and the ASbFGF group at 21 days was 60.2 +/- 2.1 and 39.4 +/- 2.1 microm, respectively (P <.01). In both the control and ASbFGF groups, all 3 MAPKs demonstrated activation compared with preimplantation levels. However, when compared with the PBS group the ASbFGF group showed greater than 33% inhibition of all three MAPKs by day 4 and day 7 (P <.05), but no significant difference in any MAPK activation by day 21 (P >.05, all groups). Cells staining positive for activated MAPK were found in the neointima and adventitia of vein grafts in both the PBS and ASbFGF groups.

CONCLUSION

MAPKs are activated during the first week after vein graft implantation. Grafts treated with ASbFGF demonstrated reduced MAPK activation and less neointimal thickening. These results suggest that the process of vein graft adaptation to the arterial circulation, and subsequent NIH, may depend on basic fibroblast growth factor activity, which is mediated, at least in part, by a MAPK-dependent mechanism.

Gene therapy using tissue-specific replication competent HSV

Tissue- or cell-specific targeting of vectors is critical to the success of gene therapy. I describe a novel approach to viral-mediated gene therapy, where viral replication and associated cytotoxicity are limited to a specific cell-type by the regulated expression of an essential immediate-early viral gene product. This is illustrated with two herpes simplex virus type 1 vectors (G92A and d12.CALP) whose growth are restricted to albumin- or calponin-expressing cells, respectively. G92A was constructed by inserting an albumin enhancer/promoter--ICP4 transgene into the thymidine kinase gene of mutant herpes simplex virus type 1 d120, deleted for both copies of the ICP4 gene. This vector also contains the Escherichia coli lacZ gene under control of the thymidine kinase promoter, a viral early promoter, to permit easy detection of infected cells containing replicating vector. In the adult, albumin is expressed uniquely in the liver and in hepatocellular carcinoma and is transcriptionally regulated. G92A efficiently replicated in vitro in two human hepatoma cell lines expressing albumin, but not in three human non-hepatoma, albumin-non-expressing tumor cell lines, while all cell lines were equally susceptible to a tissue non-specific HSV recombinant, hrR3. In vivo, G92A replicated well in subcutaneous xenografts of human hepatoma cells (Hep3B) in athymic mice, but not in non-hepatoma subcutaneous tumors (PC3 and HeLa), whereas, hrR3 replicated well in both tumor types. Intratumoral inoculation of G92A inhibited the growth of established subcutaneous hepatoma tumors in nude mice, but not prostate tumors. D12CALP also revealed the cell-specific replication to leiomyosarcoma in which calponin expression was augmented. Using hrR3, we demonstrated inhibition of re-stenosis of rat carotid arteries caused by balloon injury. The antiproliferative effects of this virus was marked in the proliferating smooth muscle cells, however, there still remained the fear for the injury of the endothelial cells. Confining a productive, cytotoxic viral infection to a specific cell-type should be useful for tumor therapy and the ablation of specific cell-types for the generation of animal models of disease. Further experiments using d12CALP will be focused on the arteriosclerosis due to balloon angioplasty or organ transplantation.

Cyclic mechanical stretch induces VEGF and FGF-2 expression in pulmonary vascular smooth muscle cells

Vascular endothelial growth factor (VEGF) and basic (b) fibroblast growth factor (FGF-2/bFGF) are involved in vascular development and angiogenesis. Pulmonary artery smooth muscle cells express VEGF and FGF-2 and are subjected to mechanical forces during pulsatile blood flow. The effect of stretch on growth factor expression in these cells is not well characterized. We investigated the effect of cyclic stretch on the expression of VEGF and FGF-2 in ovine pulmonary artery smooth muscle cells. Primary confluent cells from 6-wk-old lambs were cultured on flexible silicon membranes and subjected to cyclic biaxial stretch (1 Hz; 5-25% stretch; 4-48 h). Nonstretched cells served as controls. Expression of VEGF and FGF-2 was determined by Northern blot analysis. Cyclic stretch induced expression of both VEGF and FGF-2 mRNA in a time- and amplitude-dependent manner. Maximum expression was found at 24 h and 15% stretch (VEGF: 1.8-fold; FGF-2: 1.9-fold). These results demonstrate that mechanical stretch regulates VEGF and FGF-2 gene expression, which could play a role in pulmonary vascular development or in postnatal pulmonary artery function or disease.

Prevention of restenosis by a herpes simplex virus mutant capable of controlled long-term expression in vascular tissue in vivo

Neointimal hyperplasia resulting from vascular smooth muscle cell (SMC) proliferation and luminal migration is the major cause of autologous vein graft failure following vascular coronary or peripheral bypass surgery. Strategies to attenuate SMC proliferation by the delivery of oligonucleotides or genes controlling cell division rely on the use of high concentrations of vectors, and require pre-emptive disruption of the endothelial cell layer. We report a genetically engineered herpes simplex virus (HSV-1) mutant that, in an in vivo rabbit model system, infects all vascular layers without prior injury to the endothelium; expresses a reporter gene driven by a viral promoter with high efficiency for at least 4 weeks; exhibits no systemic toxicity; can be eliminated at will by administration of the antiviral drug acyclovir; and significantly reduces SMC proliferation and restenosis in vein grafts in immunocompetent hosts.

Relationship of the 20S proteasome and the proteasome activator PA28 to atherosclerosis and intimal hyperplasia in the human vascular system

Down-regulation of the proteasome activator PA28 results in abnormal proteasome activation and has been implicated in the development of intimal hyperplasia (IH) in animal models. Demonstration of proteasome and PA28 expression has not yet been documented in the human vascular system. This study sought to define the distribution of the 20S proteasome and its activator PA28 in human vessels and determine the relationship between the expression of the proteasome and PA28 and the development of atherosclerosis and IH. Vascular biopsies were obtained from 70 patients at the time of surgery, were snap frozen and sectioned in 5-micron sections, and prepared using standard histological techniques. The immunoperoxidase technique was used to identify 20S proteasome and PA28 expression in diseased and normal human arteries and veins as well as in patent bypass grafts with and without IH. Expression was graded by a blinded pathologist (scale: 1-4). Repeat quantification of the immunopositive cells was also performed. Expression of 20S proteasome and PA28 was identified in all vascular tissues examined. The proteins were identified predominately within the cytoplasm of vascular smooth muscle cells and endothelial cells. PA28 was more intensely expressed in quiescent regions of the vessel wall as compared to areas undergoing active proliferation and remodeling. PA28-mediated activation of the proteasome may be necessary to maintain normal cellular homeostasis and prevent excessive cellular proliferation in the human vascular system. Abnormalities of proteasome activation may have a significant role in the development of atherosclerosis and IH.

Anti-remodelling drugs for the treatment of asthma: requirement for animal models of airway wall remodelling

1. Airway wall remodelling (AWR), the structural change induced by acute and chronic inflammation in the airways, may be one of the most significant and difficult to reverse components of progressive asthma. 2. The mechanisms underlying the development of AWR are not known. Studies of only the most superficial wall structures of large airways can be conducted in living humans because of the degree of invasiveness required to measure airway structural changes. These studies reveal that currently available agents do not fully prevent or reverse AWR. Thus, animal models of asthma pathology may be used to assess the contribution of particular mediators and cells to the development of remodelling and may also prove to be useful in the initial screening of potential anti-remodelling agents. 3. Airway hyperresponsiveness and AWR stimulated by chronic antigen challenge in previously disease-free animals is the most popular of the currently used models of remodelling. Other animal models include the use of specially bred strains with intrinsic airway hyperresponsiveness or animals that have a naturally occurring asthma-like disease, such as cats with feline asthma or horses with heaves. The further development of animal models of AWR will facilitate the development of novel anti-asthma therapies.

Adenoviral mediated uteroglobin gene transfer to the adventitia reduces arterial intimal hyperplasia

PURPOSE

The aim of this study was to investigate the feasibility of gene transfer of uteroglobin, a potent anti-inflammatory and immunomodulatory agent, via adenoviral mediated gene transfer to the adventitia in the mouse carotid ligation injury model and also to investigate the efficacy of uteroglobin in reducing neointimal hyperplasia.

METHODS

Forty-five C57bl/6NHSD mice were anesthetized and left common carotid artery ligation was performed. Adenoviral vector encoding the uteroglobin gene (Ad.UG; 15 microl of 1.35 x 10(11) pfu/mL) was applied to the adventitia of the injured artery in 16 mice. In our control groups, 16 mice received adenoviral vector encoding the beta-galactosidase reporter gene (Ad.lacZ; 15 microl of 1.0 x 10(11) pfu/mL) and 13 mice received PBS only. Six mice from each group were sacrificed at 4 days for carotid artery protein extraction and Western blot analysis. The remainder were harvested at 30 days for histologic and morphometric analysis. The intima/media area ratios were calculated for each artery. The results were analyzed and compared using ANOVA and Bonferroni/Dunn post hoc testing.

RESULTS

Two mice from the LacZ group and one from the PBS group died before the 30-day endpoint. Uteroglobin expression was demonstrated in the Ad.UG treated arteries by Western blot analysis. Morphometric analysis demonstrated a statistically significant reduction in the intima/media area ratio of Ad.UG treated carotids compared to controls. There was a reduction of intima/media ratio with Ad. UG treatment of 68% compared to Ad.lacZ treatment (P < 0.0001) and 62% compared to PBS treatment (P = 0.0006). There was no statistical difference between the control groups.

CONCLUSION

Adenoviral mediated gene transfer via the adventitia is an effective mode of gene delivery. Adventitial uteroglobin gene transfer using an adenoviral vector induces uteroglobin protein production and significantly reduces neointimal hyperplasia in the mouse carotid ligation injury model.

A novel recombinant basic fibroblast growth factor and its secretion

Basic fibroblast growth factor (FGF-2) is a pleiotropic mitogen which plays an important role in cell growth, differentiation, migration, and survival in different cells and organ systems. Recently, several clinical applications for FGF-2 gene transfer are being evaluated in wound healing and collateral artery development to relieve myocardial and peripheral ischemia due to the ability of FGF-2 to regulate the growth and function of vascular cells. However, FGF-2 lacks a classical hydrophobic secretion signal peptide, the FGF-2 chimeras containing various signal sequences have been explored. In this study, a novel recombinant 4sFGF-2 was constructed by replacing nine residues from the amino-terminus of native FGF-2 (Met1 to Leu9) with eight amino acid residues of signal peptide of FGF-4 (Met1 to Ala8) to better increase the secretion level of FGF-2. When the recombinant FGF-2 gene, cloned into the expression vector with CMV promoter, was expressed in COS-7 cells, the recombinant 4sFGF-2 was highly secreted into the media. The secreted 4sFGF-2 showed the same biological activity as the native FGF-2 in the dose-response effects on DNA synthesis and cell growth of rat aortic smooth muscle cells (RASMCs) and NIH3T3 cells. The 4sFGF-2 also was able to activate MAPK as wild FGF-2 in RASMCs. These results indicate that a novel recombinant 4sFGF-2 may be useful as clinical applicability of angiogenic growth factor gene transfer.

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.

Antisense and gene therapy to prevent restenosis

A primary pathologic response to vascular injury is the proliferation and migration of vascular smooth muscle cells and the development of neointimal lesions. An increasing body of knowledge regarding the molecular and genetic basis of neointimal disease has created a unique opportunity for the treatment of this complex disorder. Gene therapy attempts to correct pathobiological processes by either inhibiting or correcting cellular functions at the level of gene expression. These endpoints are achieved by the delivery of either functional genes or oligonucleotides, capable of interfering with a cell's programmed machinery. Since the early 1990s, the evolution of this technology, along with an ever-expanding source of pathobiological information, has led to many novel approaches for the treatment of restenosis in arterial balloon injury as well as vein graft bypass failure. Using a variety of targets, inhibition of proliferation has predominantly been achieved through direct disruption of the cell cycle machinery. In addition, others have demonstrated successful inhibition by interfering with the signals for cellular proliferation or the enhancement of anti-proliferative stimuli. As this exciting therapeutic alternative evolves, improvements in safety, specificity and efficiency will enhance the likelihood of widespread clinical application.

Gene therapy for vein graft disease

Applying gene therapeutics to vein graft disease requires foundational knowledge of the underlying pathophysiology. This review details a brief description of vein graft disease, examines published and unpublished data on gene transfer to veins, and reviews the genes, which have significantly altered vascular biology.

Restenosis and gene therapy

Atherosclerosis is one of the main causes of mortality and morbidity in westernised countries. Treatment of symptomatic atherosclerosis by angioplasty involves major vascular responses such as neointima formation and constrictive vascular remodelling leading to restenosis. Stent placement prevents vasoconstriction but is associated with in-stent neointima formation. Therefore, stent placement requires adjunctive therapy. In this review we discuss the potential of local gene therapy for restenosis. More particularly, we focus on strategies to inhibit smooth muscle cell (SMC) proliferation and migration, prevent thrombosis, decrease oxidative stress in the arterial wall and enhance re-endothelialisation associated with adaptive remodelling. The potential of different vector systems and devices for local gene transfer in the arterial wall is discussed.

Adenoviral-mediated uteroglobin gene transfer inhibits neointimal hyperplasia after balloon injury in the rat carotid artery

OBJECTIVE

Uteroglobin is a protein with potent anti-inflammatory and immunomodulatory effects. We hypothesize that induction of uteroglobin expression in the artery wall by local adenoviral gene transfer will decrease neointimal hyperplasia in the rat carotid artery after balloon injury.

METHODS

Seven male Sprague-Dawley rats underwent balloon injury of the common carotid artery. After the injury, with flow occluded, the artery was instilled with 50 microL of the adenoviral vector encoding uteroglobin gene (Ad.UG) at a concentration of 1.35 x 10(11) pfu/mL (n = 7) or 0.68 x 10(11) pfu/mL (n = 7) (n = 7). Control animals were similarly treated: either an adenovirus encoding for beta-galactosidase gene (Ad.LacZ) at 1 x 10(11) pfu/mL (n = 7) or the phosphate-buffered saline (PBS) vehicle (n = 6) was used. The solution was allowed to dwell for 20 minutes. The rats were humanely killed after 14 days by perfusion fixation, and the carotid arteries were sectioned for analysis with computerized planimetry. The intima-media area ratios were calculated for each artery and compared with analysis of variance with Bonferroni/Dunn post hoc testing. One additional rat from the PBS, Ad.LacZ, and Ad.UG (1.35 x 10(11) pfu/mL) groups was humanely killed 4 days after treatment for carotid artery protein extraction and Western blotting.

RESULTS

Uteroglobin protein production was confirmed in the Ad.UG-treated arteries with Western blotting. Morphometric analysis showed that the Ad.UG group at 1.35 x 10(11) pfu/mL had a significantly lower intima-media area ratio than both the Ad.LacZ (P =.002) and PBS (P =.004) controls. The Ad.UG group at 0.68 x 10(11) pfu/mL was also significantly different from the Ad. LacZ (P =.003) and PBS (P =.006) controls. There was no statistical difference between the two control groups or between the two Ad.UG groups.

CONCLUSION

Adenoviral gene transfer of uteroglobin, delivered intraluminally after arterial injury causes the production of uteroglobin protein and has an inhibitory effect on neointimal accumulation in the rat model.

Novel approaches for the prevention of restenosis

Restenosis, the re-narrowing of the lumen of the coronary artery, in the months following a successful percutaneous balloon angioplasty or stenting, remains the main limitation to percutaneous coronary revascularisation. Serial intravascular ultrasound studies have shown that restenosis after conventional balloon angioplasty represents a complex interplay between elastic recoil, smooth muscle proliferation and vascular remodelling, while restenosis after stent deployment is due almost entirely to smooth muscle hyperplasia and matrix proliferation. Despite intensive investigation in animal models and in clinical trials, most pharmacological agents have been found to be ineffective in preventing restenosis after percutaneous balloon angioplasty or stenting. Although studies frequently report success in the suppression of neointimal proliferation in animal models of balloon vascular injury, few of them have been successful in clinical trials. Lately, the advent of endovascular radiation, new antiproliferative agents, recombinant DNA, growth factor regulators and novel local drug delivery systems have shown promising results. In the past five years, intracoronary radiation with gamma- and beta-emitting sources has been evaluated intensively with very encouraging results. This is the first potent non-pharmacological approach that has been successful in a large number of patients in controlling excessive tissue proliferation. It is very likely that a combination of stents and pharmacological and/or non-pharmacological inhibition of neointimal hyperplasia will likely result in further reductions in the incidence if restenosis. The continued attractiveness of percutaneous coronary revascularisation, as an alternative to medical treatment or bypass surgery for patients with coronary artery disease, will depend upon our ability to control the restenotic process. Due to the vast literature on the subject, this review will focus mainly on clinical trials that show the most promise and will highlight those that warrant further investigation.

Gene Therapy for Cardiovascular Disease

During the past decade, gene therapy for the treatment of many inherited and acquired medical problems has become the subject of increasing focus in both the scientific litera ture and the lay press. This review examines the history and current status of gene therapy for advanced chronic periph eral and myocardial ischemia.

Sealing of polyester prostheses with autologous fibrin glue and bone marrow

The purpose of this study was to develop a sealing technique for polyester prosthetic grafts able to promote healing and reduce intimal hyperplasia. The porcine experimental model was aortoiliac bypass with a 6-mm diameter knitted polyester prosthetic graft implanted for 14 and 90 days. Animals were divided into three groups according to sealing technique as follows: pre-clotting with blood (group I, n = 12), sealing with autologous fibrin glue (group II, n = 14), and sealing with autologous fibrin glue and bone marrow cells (group III, n = 16). Feasibility and quality of sealing were evaluated by scanning electron microscopy prior to implantation and by assessment of blood loss. After removal, prostheses were cut into three segments comprising the proximal anastomosis, midsection, and distal anastomosis. Pieces were fixed, embedded in paraffin, and serially sectioned for histologic study. Histological study focused on the degree of stenosis and hyperplasia of the neointima of each prosthesis. The results of this short-term study indicate that sealing of polyester vascular prosthetic grafts with autologous fibrin glue and bone marrow cells is effective in reducing intimal hyperplasia. However further study will be needed to assess long-term healing.

Effect of p53 gene therapy combined with CTLA4Ig selective immunosuppression on prolonged neointima formation reduction in a rat model

In a previous study, we have demonstrated a significant reduction of neointimal formation following adenovirus-mediated gene transfer of p53 to the injured rat carotid artery. The purpose of this study was to determine if the effect of p53 gene in reducing neointimal formation would still be present up to 8 weeks after arterial injury and whether it could be enhanced by adding immunosuppression. Cytotoxic T lymphocyte-associated antigen-4 Ig (CTLA41g), a novel immunosuppressive agent, is a recombinant soluble protein that blocks T cell-dependent immune response. Animals were divided into eight groups (n = 6 in each). In vivo gene transfer was used in isolated segments of balloon-injured rat carotid arteries. Genetically modified adenovirus encoding for wild-type p53 protein was applied at 8 x 10(10) pfu/mL. Control rats received adenovirus null at the same concentration. A daily dose of 300 microg of CTLA41g was given intraperitoneally, either once, twice, or three times. Expression of p53 was determined by Western blot analysis. Neointimal formation was assessed at 4 or 8 weeks by harvesting carotid arteries and determining the intima/media (I/M) ratio cross-sectional area measurements. p53 expression was confirmed by Western blot analysis. We concluded that adenovirus-mediated p53 gene transfer significantly decreases the formation of neointima up to 8 weeks following rat carotid injury. However, there is loss of effectiveness on neointimal formation inhibition as time elapses. When CTLA41g is added, there is significant improvement in results, with sustained neointimal formation inhibition at 8 weeks after the procedure.

Adenoviral-mediated expression of antisense RNA to basic fibroblast growth factor reduces tangential stress in arterialized vein grafts

PURPOSE

The purpose of this study was to test whether basic fibroblast growth factor (bFGF) participates in arterialized vein graft remodeling.

METHODS

Rabbits underwent in vivo gene transfer and carotid interposition vein grafting. Segments of external jugular vein were infected with an adenovirus that expressed antisense bFGF RNA (Ad.ASbFGF) at 1 x 10(10) PFU/mL to inhibit new synthesis of bFGF by cells in the vein graft wall. Control rabbits were treated with either adenovirus that encoded beta-galactosidase (Ad.lacZ) at 1 x 10(10) PFU/mL or vehicle (phosphate-buffered saline solution [PBS]). At 3 days, 3 grafts per treatment group were harvested for the determination of gene expression of ASbFGF RNA by reverse transcriptase-polymerase chain reaction. Rabbits were killed, and perfusion was fixed 2 months after the grafting. Total wall thickness and lumen circumference of vein grafts and normal arteries were measured in cross sections. Calculated mean tangential stress (+/-SD) for the ASbFGF-treated group and controls was compared for significance. Grafts were immunohistochemically stained to assess bFGF protein production.

RESULTS

Only the grafts infected with the Ad.ASbFGF gene expressed ASbFGF RNA. Grafts that were treated with Ad.ASbFGF displayed lower tangential stress (10.9 +/- 2.3 dynes/cm(2)) than PBS alone (22 +/- 2.8 dynes/cm(2)) or Ad. lacZ-treated controls (20.6 +/- 5.4 dynes/cm(2); P <.001). Tangential stress in the Ad.ASbFGF group was comparable to a normal carotid artery (13.9 +/- 2.1 dynes/cm(2)). The difference in mean total wall thickness was significant among the 3 treatment groups: Ad.ASbFGF, 164 +/- 3.4 microm); Ad.lacZ, 100 +/- 3.3 microm; and PBS, 96 +/- 3.6 microm; P <.01). Luminal circumference was not different among the groups. The Ad.ASbFGF-treated vein graft wall was composed of thick layers of concentric smooth muscle cells and elastin fibers in contrast to the sponge-like appearance observed in control arterialized vein grafts. Reduction in bFGF protein was noted only in the Ad.ASbFGF-treated group.

CONCLUSION

Inhibition of bFGF synthesis in vivo with the use of adenoviral gene transfer of antisense RNA to bFGF promotes a vein graft with decreased tangential stress while maintaining the luminal area. The vein graft wall is remodeled and qualitatively resembles an artery so that wall tangential stress in Ad.ASbFGF and normal artery are not significantly different. The lack of significant difference in lumen circumference among groups suggests that wall thickening in the Ad. ASbFGF grafts is not at the expense of luminal narrowing. Our results suggest that ASbFGF RNA expression may represent an effective strategy in limiting the failure of arterialized venous conduits.

Autocrine signaling through Ras prevents apoptosis in vascular smooth muscle cells in vitro

Vascular smooth muscle cell (SMC) apoptosis contributes to physiological and pathological vascular remodeling. Autocrine fibroblast growth factor (FGF) signaling promotes survival in SMC in vitro. Interruption of autocrine FGF signaling results in apoptosis that can be rescued by other growth factors such as PDGF (platelet-derived growth factor) or EGF (epidermal growth factor). Such heterologous growth factor rescue is prevented by pharmacological inhibition of MAPK, implicating signaling through Ras in mediating survival. This study was designed to test the hypothesis that signaling through Ras is both necessary and sufficient to mediate SMC survival in vitro. Recombinant adenoviruses encoding dominant-negative (Ras(N17)) and constitutively active (Ras(L61)) mutants of Ras were used. Ras(N17) blocks growth factor-mediated MAPK activation and can itself induce SMC apoptosis. Ras(N17) is synergistic with inhibition of autocrine FGF signaling in triggering apoptosis and prevents heterologous growth factor rescue. Conversely, Ras(L61) prevents apoptosis resulting from inhibition of autocrine FGF signaling. Rescue by Ras(L61) can be partially prevented by pharmacological inhibition of MEK or phosphatidylinositol 3-kinase, two downstream effectors of Ras. These results suggest that Ras signaling is both necessary and sufficient to mediate survival in SMC in vitro. Further work is required to determine how these signaling events are regulated in the context of vascular remodeling in vivo.

Inhibition of rat vascular smooth muscle cell proliferation in vitro and in vivo by recombinant replication-competent herpes simplex virus

BACKGROUND AND PURPOSE

The proliferation of vascular smooth muscle cells (VSMCs) is a common feature associated with vascular proliferative disorders such as atherosclerosis and restenosis after balloon angioplasty. We examined the antiproliferative effects of recombinant replication-competent herpes simplex virus (HSV), hrR3, to proliferative VSMCs both in vitro and in vivo.

METHODS

Early passages of Sprague-Dawley rat VSMCs were infected with hrR3 at a low multiplicity of infection (0.01 to 1.0) to examine the in vitro cytotoxic activity of this recombinant HSV to VSMCs in a proliferative state. Sprague-Dawley rats underwent balloon dilatation injury of the left carotid artery to induce neointimal formation. The injured carotid arteries were infected with hrR3 five days after balloon injury. Two weeks after injury, the left carotid arteries were fixed, and the areas of the neointimal and medial layers were analyzed microscopically. Because the reporter Escherichia coli lacZ gene in hrR3 is expressed only in infected cells in which the virus is actively replicating, virus replication was confirmed by X-gal staining.

RESULTS

A morphometric analysis revealed that there were significant differences in the intima/media ratio between the HSV-treated group and mock-infected group (0. 354+/-0.068 and 1.08+/-0.055, respectively). In the histological study (X-gal staining), positive X-gal staining was observed chiefly in the VSMCs in the medial layer just beneath the internal elastic lamina, indicating active viral replication.

CONCLUSIONS

Virus-mediated cytocidal therapy using recombinant HSV vector is a promising modality for the treatment of the restenosis after balloon angioplasty.

Gene therapy as a therapeutic intervention for vascular disease

Gene therapy for the treatment of many medical problems, including vascular disease, has become the subject of increasing discussion in both the scientific literature and the national press over the past decade. This review will examine the history and current status of gene therapy for vascular proliferative disorders and advanced chronic peripheral and cardiac ischemia.

p53 gene transfer to the injured rat carotid artery decreases neointimal formation

PURPOSE

We studied the effect of adenovirus-mediated p53 gene transfer on the injured rat carotid artery to determine its ability to decrease the formation of neointima.

METHODS

In vivo gene transfer was used in isolated segments of balloon-injured rat carotid arteries. Genetically modified adenovirus containing the gene encoding for wild-type p53 (AdWTp53) was applied in three concentrations: 8 x 10(10), 1.6 x 10(10), and 8 x 10(9) pfu/mL. Control rats received either adenovirus null (AdNull), 8 x 10(10) pfu/mL, or Medium-199 solution (vehicle). Expression of p53 was determined 4 days after gene transfer by Western blotting. Neointimal formation was assessed after 14 days by harvesting carotid arteries and determining the intima/media (I/M) ratio based on cross-sectional area measurement. Simultaneously, immunohistochemistry was done to detect the presence of p53 on smooth muscle cell nuclei.

RESULTS

P53 expression was confirmed by Western blotting. There was a significant reduction in neointimal formation on all treated animals compared with controls. The highest dose of AdWTp53 (8 x 10(10) pfu/mL) resulted in a near-total arrest of neointimal formation (I/M = 0.09 +/- 0.03, mean +/- SEM) with P <. 0001 versus vehicle (I/M = 2.23 +/- 0.15) or AdNull (I/M = 2.12 +/-. 12). The intermediate dose of AdWTp53 (1.6 x 10(10) pfu/mL) resulted in an I/M value of 1.04 +/- 0.18, with P <.001 versus vehicle and P =.001 versus AdNull. The lowest dose (8 x 10(9) pfu/mL) resulted in an I/M value of 1.12 +/- 0.18, with P <.001 versus vehicle and P <. 002 versus AdNull. The immunohistochemistry was positive for the presence of p53 in rats infected with AdWTp53.

CONCLUSIONS

Adenovirus-mediated gene transfer of p53 protein significantly decreases the formation of neointima in the rat carotid injury model. This may represent a potential therapy for restenosis in humans.

In vitro growth suppression of vascular smooth muscle cells using adenovirus-mediated gene transfer of a truncated form of fibroblast growth factor receptor

Vascular smooth muscle cell (VSMC) proliferation associated with arterial injury causes restenosis, which remains to be resolved in cardiovascular and ischemic cerebrovascular disease, especially after balloon angioplasty. Fibroblast growth factor (FGF) is a potent mitogen and a trophic factor for a variety of cells, including VSMCs. We constructed a replication-deficient adenovirus vector, designated AxCA delta FR, coding a truncated form of fibroblast growth factor receptor-1 (FGFR-1) gene lacking the intracellular domain to interrupt receptor-mediated FGF signaling, and examined its effect on the proliferation of primary-cultured rat VSMCs. We transferred the truncated form of the FGFR-1 gene to the VSMCs and confirmed its expression and localization in infected cells by Western blotting and immunofluorescence study. The VSMCs infected with AxCA delta FR degenerated and the proliferation of these cells was suppressed markedly by the infection with this virus in vitro. Our results suggest that the receptor-mediated signal of FGFs has an important role in VSMC proliferation and gene transfer of a truncated form of FGFR using adenoviral vector may be useful for the treatment of the diseases caused by excessive proliferation of VSMCs like restenosis after percutaneous transluminal angioplasty or carotid endoarterectomy.

Autocrine FGF signaling is required for vascular smooth muscle cell survival in vitro

Expression of both basic fibroblast growth factor (bFGF) and FGF receptors (FGFR) by vascular smooth muscle cells suggests that autocrine FGF signaling mechanisms may have important functions. Inhibition of smooth muscle cell bFGF expression provokes apoptosis, suggesting that endogenous bFGF generates an anti-apoptotic signal. The purpose of this study was to determine whether the survival function of endogenous bFGF requires signaling through FGFR. A recombinant adenovirus encoding a truncated murine FGFR-1 lacking the kinase domain (DN-FGFR) efficiently expressed the transgene in cultured rat aortic smooth muscle cells. The truncated receptor acted in a dominant negative fashion to effectively prevent receptor-mediated signaling, assessed by phosphorylation of p42/p44 MAP kinase. Expression of DN-FGFR provoked apoptosis of SMC in a dose-dependent fashion that was insensitive to recombinant bFGF but could be rescued by platelet derived growth factor or epidermal growth factor. Heterologous growth factor rescue was inhibited by PD98059, an inhibitor of MEK (MAP kinase-kinase). These data demonstrate that inhibition of FGF receptor activation results in apoptosis and suggest that an intact autocrine FGF signaling loop is required for vascular smooth muscle cell survival in vitro. These findings also implicate the Ras/Raf/MEK/MAP kinase cascade in generating or sustaining the survival signal. The functional significance of an autocrine FGF signaling loop in non-transformed cells has important implications for cardiovascular development, remodeling and disease.