Adenovirus-mediated gene transfer of transforming growth factor-beta3, but not transforming growth factor-beta1, inhibits constrictive remodeling and reduces luminal loss after coronary angioplasty

Targeting Smad-Mediated TGFß Pathway in Coronary Artery Bypass Graft

Revascularization surgeries such as coronary artery bypass grafting (CABG) are sometimes necessary to manage coronary heart disease (CHD). However, more than half of these surgeries fail within 10 years due to the development of intimal hyperplasia (IH) among others. The cytokine transforming growth factor-beta (TGFß) and its signaling components have been found to be upregulated in diseased or injured vessels, and to promote IH after grafting. Interventions that globally inhibit TGFß in CABG have yielded contrasting outcomes in in vitro and in vivo studies including clinical trials. With advances in molecular biology, it becomes clear that TGFß exhibits both protective and damaging roles, and only specific components such as some Smad-dependent TGFß signaling mediate vascular IH. The activin receptor-like kinase (ALK)-mediated Smad-dependent TGFß signaling pathways have been found to be activated in human vascular smooth muscle cells (VSMCs) following injury and in hyperplastic preimplantation vein grafts. It appears that focused targeting of TGFß pathway constitutes a promising therapeutic target to improve the outcome of CABG. This study dissects the role of TGFß pathway in CABG failure, with particular emphasis on the therapeutic potentials of specific targeting of Smad-dependent and ALK-mediated signaling.

TGFβ, smooth muscle cells and coronary artery disease: a review

Excessive vascular smooth muscle cell (SMC) proliferation, migration and extracellular matrix (ECM) synthesis are key events in the development of intimal hyperplasia, a pathophysiological response to acute or chronic sources of vascular damage that can lead to occlusive narrowing of the vessel lumen. Atherosclerosis, the primary cause of coronary artery disease, is characterised by chronic vascular inflammation and dyslipidemia, while revascularisation surgeries such as coronary stenting and bypass grafting represent acute forms of vascular injury. Gene knockouts of transforming growth factor-beta (TGFβ), its receptors and downstream signalling proteins have demonstrated the importance of this pleiotropic cytokine during vasculogenesis and in the maintenance of vascular homeostasis. Dysregulated TGFβ signalling is a hallmark of many vascular diseases, and has been associated with the induction of pathological vascular cell phenotypes, fibrosis and ECM remodelling. Here we present an overview of TGFβ signalling in SMCs, highlighting the ways in which this multifaceted cytokine regulates SMC behaviour and phenotype in cardiovascular diseases driven by intimal hyperplasia.

Delivery of viral vectors for gene therapy in intimal hyperplasia and restenosis in atherosclerotic swine

Cardiovascular diseases including atherosclerosis are a major financial and health burden globally. Inflammation associated with atherosclerosis results in the development of plaques that can rupture causing thrombosis, stroke, or death. The most widely used treatment for the removal of atherosclerotic plaques is percutaneous transluminal coronary angioplasty (PTCA) with or without stenting. Although this is a safer and minimally invasive method, restenosis and intimal hyperplasia after interventional procedure remains a major hurdle and more refined approaches are needed. Studies in large animal models such as pigs have facilitated a greater understanding of the underlying mechanisms of the disease and provided novel targets for therapeutic intervention. In pre-clinical studies, viral vector gene therapy has emerged as a promising option for the reduction and/or prevention of restenosis and intimal hyperplasia. Although studies in animal models have generated promising results, clinical trials have yet to prove the clinical efficacy of gene therapy in coronary artery diseases. In this review, we examined and critically reviewed the most recent advances in viral vector gene therapy obtained from studies using porcine model of atherosclerosis.

Local Endovascular Delivery, Gene Therapy, and Cell Transplantation for Peripheral Arterial Disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

Local Stent-Based Release of Transforming Growth Factor-β1 Limits Arterial In-Stent Restenosis

The long-term success of intra-arterial stenting remains limited by in-stent restenosis (ISR). Transforming growth factor-β1 (TGF-β1) can inhibit smooth muscle cell (SMC) proliferation and migration and convert SMCs into extracellular matrix (ECM)-synthesizing cells. Here, we evaluate the effects of stent-based delivery of TGF-β1 on ISR in a rabbit model. Channeled stents loaded with TGF-β1 or control microspheres were deployed in rabbit aortas. Stented aortas were harvested at 7 and 28 d and evaluated for Ki-67-positive cells, collagenous ECM production, and intima-to-media (I/M) ratio. At 7 d, the TGF-β1 group exhibited fewer Ki-67-positive cells were found for the TGF-β1 group (17.87 ± 2.18 cells per mm(2)) relative to control (25.07 ± 2.65 cells per mm(2), p = 0.04), but increased collagen content (31.4 ± 2.5 percentage area) compared with control (29.3 ± 1.2 percentage area, p = 0.019). The I/M ratio in the TGF-β1 group was reduced by 50% and 9.1% versus control at 7 d (0.13 ± 0.02 vs. 0.26 ± 0.02, p = 0.0001) and 28 d (1.80 ± 0.05 vs. 1.98 ± 0.08, p = 0.0038), respectively. Stent-based controlled release of TGF-β1 limits ISR and is associated with inhibition of SMC proliferation but an increase in ECM production.

XBP 1-Deficiency Abrogates Neointimal Lesion of Injured Vessels Via Cross Talk With the PDGF Signaling

OBJECTIVE

Smooth muscle cell (SMC) migration and proliferation play an essential role in neointimal formation after vascular injury. In this study, we intended to investigate whether the X-box-binding protein 1 (XBP1) was involved in these processes.

APPROACH AND RESULTS

In vivo studies on femoral artery injury models revealed that vascular injury triggered an immediate upregulation of XBP1 expression and splicing in vascular SMCs and that XBP1 deficiency in SMCs significantly abrogated neointimal formation in the injured vessels. In vitro studies indicated that platelet-derived growth factor-BB triggered XBP1 splicing in SMCs via the interaction between platelet-derived growth factor receptor β and the inositol-requiring enzyme 1α. The spliced XBP1 (XBP1s) increased SMC migration via PI3K/Akt activation and proliferation via downregulating calponin h1 (CNN1). XBP1s directed the transcription of mir-1274B that targeted CNN1 mRNA degradation. Proteomic analysis of culture media revealed that XBP1s decreased transforming growth factor (TGF)-β family proteins secretion via transcriptional suppression. TGF-β3 but not TGF-β1 or TGF-β2 attenuated XBP1s-induced CNN1 decrease and SMC proliferation.

CONCLUSIONS

This study demonstrates for the first time that XBP1 is crucial for SMC proliferation via modulating the platelet-derived growth factor/TGF-β pathways, leading to neointimal formation.

Periluminal expression of a secreted transforming growth factor-β type II receptor inhibits in-stent neointima formation following adenovirus-mediated stent-based intracoronary gene transfer

Transforming growth factor-β1 (TGF-β1) has been shown unequivocally to enhance neointima formation in carotid and ileo-femoral arteries. In our previous studies, however, TGF-β1 expression in coronary arteries actually reduced neointima formation without affecting luminal loss postangioplasty, while expression of a TGF-β1 antagonist (RIIs) in balloon-injured coronary arteries reduced luminal loss without affecting neointima formation. These observed effects may be a consequence of the mode of coronary artery gene transfer employed, but they may also represent differences in the modes of healing of coronary, carotid, and ileo-femoral arteries after endoluminal injury. To help clarify whether a gene therapy strategy to antagonize TGF-β might have application within the coronary vasculature, we have investigated the effect of high-level periluminal expression of RIIs using stent-based adenovirus-mediated intracoronary gene transfer. Porcine coronary arteries were randomized to receive a custom-made CoverStent preloaded with saline only, or with 1×10(9) infectious units of adenovirus expressing RIIs or β-galactosidase (lacZ). Vessels were analyzed 28 days poststenting, at which time angiographic in-stent diameter was significantly greater in RIIs-treated arteries, and in-stent luminal loss significantly reduced. Computerized morphometric minimum in-stent lumen area was ~300% greater in RIIs-exposed vessels than in lacZ or saline-only groups. This was because of significantly reduced neointima formation in the RIIs group. RIIs had no demonstrable effect on cellular proliferation or apoptosis, but greater normalized neointimal/medial collagen content was observed in RIIs-exposed arteries. These data highlight the qualitatively similar effect of TGF-β antagonism on neointima formation in injured coronary and noncoronary arteries, and suggest that since cellular proliferation is unaffected, TGF-β1 antagonism might prevent in-stent restenosis without the delayed healing that is associated with drug-eluting stents in current clinical use.

High-throughput screening identifies idarubicin as a preferential inhibitor of smooth muscle versus endothelial cell proliferation

Intimal hyperplasia is the cause of the recurrent occlusive vascular disease (restenosis). Drugs currently used to treat restenosis effectively inhibit smooth muscle cell (SMC) proliferation, but also inhibit the growth of the protective luminal endothelial cell (EC) lining, leading to thrombosis. To identify compounds that selectively inhibit SMC versus EC proliferation, we have developed a high-throughput screening (HTS) format using human cells and have employed this to screen a multiple compound collection (NIH Clinical Collection). We developed an automated, accurate proliferation assay in 96-well plates using human aortic SMCs and ECs. Using this HTS format we screened a 447-drug NIH Clinical Library. We identified 11 compounds that inhibited SMC proliferation greater than 50%, among which idarubicin exhibited a unique feature of preferentially inhibiting SMC versus EC proliferation. Concentration-response analysis revealed this differential effect most evident over an ∼10 nM-5 µM window. In vivo testing of idarubicin in a rat carotid injury model at 14 days revealed an 80% reduction of intimal hyperplasia and a 45% increase of lumen size with no significant effect on re-endothelialization. Taken together, we have established a HTS assay of human vascular cell proliferation, and identified idarubicin as a selective inhibitor of SMC versus EC proliferation both in vitro and in vivo. Screening of larger and more diverse compound libraries may lead to the discovery of next-generation therapeutics that can inhibit intima hyperplasia without impairing re-endothelialization.

The role of shear-induced transforming growth factor-β signaling in the endothelium

OBJECTIVE

Vascular endothelial cells (ECs) are continuously exposed to blood flow that contributes to the maintenance of vessel structure and function; however, the effect of hemodynamic forces on transforming growth factor-β (TGF-β) signaling in the endothelium is poorly described. We examined the potential role of TGF-β signaling in mediating the protective effects of shear stress on ECs.

APPROACH AND RESULTS

Human umbilical vein ECs (HUVECs) exposed to shear stress were compared with cells grown under static conditions. Signaling through the TGF-β receptor ALK5 was inhibited with SB525334. Cells were examined for morphological changes and harvested for analysis by real-time polymerase chain reaction, Western blot analysis, apoptosis, proliferation, and immunocytochemistry. Shear stress resulted in ALK5-dependent alignment of HUVECs as well as attenuation of apoptosis and proliferation compared with static controls. Shear stress led to an ALK5-dependent increase in TGF-β3 and Krüppel-like factor 2, phosphorylation of endothelial NO synthase, and NO release. Addition of the NO donor S-nitroso-N-acetylpenicillamine rescued the cells from apoptosis attributable to ALK5 inhibition under shear stress. Knockdown of TGF-β3, but not TGF-β1, disrupted the HUVEC monolayer and prevented the induction of Krüppel-like factor 2 by shear.

CONCLUSIONS

Shear stress of HUVECs induces TGF-β3 signaling and subsequent activation of Krüppel-like factor 2 and NO, and represents a novel role for TGF-β3 in the maintenance of HUVEC homeostasis in a hemodynamic environment.

Preferential secretion of collagen type 3 versus type 1 from adventitial fibroblasts stimulated by TGF-β/Smad3-treated medial smooth muscle cells

Restenosis, or arterial lumen re-narrowing, occurs in 30-50% of the patients undergoing angioplasty. Adaptive remodeling is the compensatory enlargement of the vessel size, and has been reported to prevent the deleterious effects of restenosis. Our previous studies have shown that elevated transforming growth factor (TGF-β) and its signaling protein Smad3 in the media layer induce adaptive remodeling of angioplastied rat carotid artery accompanying an increase of total collagen in the adventitia. In order to gain insights into a possible role of collagen in Smad3-induced adaptive remodeling, here we have investigated a mechanism of cell-cell communication between medial smooth muscle cells (SMCs) and adventitial fibroblasts in regulating the secretion of two major collagen subtypes. We have identified a preferential collagen-3 versus collagen-1 secretion by adventitial fibroblasts following stimulation by the conditioned medium from the TGF-β1-treated/Smad3-expressing medial smooth muscle cells (SMCs), which contained higher levels of CTGF and IGF2 as compared to control medium. Treating the TGF-β/Smad3-stimulated SMCs with an siRNA to either CTGF or IGF2 reversed the effect of conditioned media on preferential collagen-3 secretion from fibroblasts. Moreover, recombinant CTGF and IGF2 together stimulated adventitial fibroblasts to preferentially secrete collagen-3 versus collagen-1. This is the first study to identify a preferential secretion of collagen-3 versus collagen-1 from adventitial fibroblasts as a result of TGF-β/Smad3 stimulation of medial SMCs, and that CTGF and IGF2 function together to mediate this signaling communication between the two cell types.

Mechanisms of post-intervention arterial remodelling

It has been appreciated over the past two decades that arterial remodelling, in addition to intimal hyperplasia, contributes significantly to the degree of restenosis that develops following revascularization procedures. Remodelling appears to be an adventitia-based process that is contributed to by multiple factors including cytokines and growth factors that regulate extracellular matrix or phenotypic transformation of vascular cells including myofibroblasts. In this review, we summarize the currently available information from animal models as well as clinical investigations regarding arterial remodelling. The factors that contribute to this process are presented with an emphasis on potential therapeutic methods to enhance favourable remodelling and prevent restenosis.

Coronary angiography and percutaneous coronary intervention in the porcine model: a practical guide to the procedure

Assessment of safety and efficacy within the porcine coronary artery model remains a standard requirement for new therapies delivered to the coronary arteries before proceeding to clinical testing. Human coronary procedures carry a very low mortality rate; however, procedural mortality for porcine experiments is often high, despite these animals being young and free of atherosclerosis. Some of these deaths are due to poor technique, and therefore avoidable. However, despite the wide use of this model, a systematic description of the procedure has never been published. This article will detail how porcine angiography and stent implantation is performed in our institution and will discuss the relevant differences between humans and pigs with regard to anaesthesia, pharmacotherapy, vascular access, catheter selection and angiographic views. Important variations to the technique that have been reported are also covered.

In-vivo assessment of the natural history of coronary atherosclerosis: vascular remodeling and endothelial shear stress determine the complexity of atherosclerotic disease progression

PURPOSE OF REVIEW

Atherosclerotic disease progression is determined by localized plaque growth, which is induced by systemic and local hemodynamic factors, and the nature of the wall remodeling response. The purpose of this review is to summarize the processes underlying the heterogeneity of coronary atherosclerosis progression in relation to the local hemodynamic and arterial remodeling environment.

RECENT FINDINGS

Multiple competing biological processes in the extracellular matrix define the extent of vascular remodeling and disease progression. The remodeling phenomenon is not consistent but is characterized by great phenotypical heterogeneity which reflects the complex effect of systemic, genetic and hemodynamic factors on the arterial wall response to plaque formation and progression. The exaggeration of expansive remodeling (i.e., excessive expansive remodeling) likely contributes to the transformation of an initially favorable action into an excessive course of vessel expansion, continued disease progression and plaque instability. Extremely low endothelial shear stress and excessive expansive remodeling establish a vicious cycle which leads to the formation of severe plaques with high-risk characteristics.

SUMMARY

The dynamic interplay between the local hemodynamic environment and the wall remodeling behavior determines the complexity of the natural history of atherosclerosis and explains the development of localized plaque vulnerability.

TGF-β and restenosis revisited: a Smad link

Despite novel surgical therapies for the treatment of atherosclerosis, restenosis continues to be a significant impediment to the long-term success of vascular interventions. Transforming growth factor-beta (TGF-β), a family of cytokines found to be up-regulated at sites of arterial injury, has long been implicated in restenosis; a role that has largely been attributed to TGF-β-mediated vascular fibrosis. However, emerging data indicate that the role of TGF-β in intimal thickening and arterial remodeling, the critical components of restenosis, is complex and multidirectional. Recent advancements have clarified the basic signaling pathway of TGF-β, making evident the need to redefine the precise role of this family of cytokines and its primary signaling pathway, Smad, in restenosis. Unraveling TGF-β signaling in intimal thickening and arterial remodeling will pave the way for a clearer understanding of restenosis and the development of innovative pharmacological therapies.

Proteins mediating collagen biosynthesis and accumulation in arterial repair: novel targets for anti-restenosis therapy

Events contributing to restenosis after coronary interventions include platelet aggregation, inflammatory cell infiltration, growth factor release, and accumulation of smooth muscle cells (SMCs) and extracellular matrix (ECM). The ECM is composed of various collagen subtypes and proteoglycans and over time constitutes the major component of the mature restenotic plaque. The pathophysiology of collagen accumulation in the ECM during arterial restenosis is reviewed. Factors regulating collagen synthesis and degradation, including various cytokines and growth factors involved in the process, may be targets for therapies aimed at prevention of in-stent restenosis.

Arterial gene transfer of the TGF-beta signalling protein Smad3 induces adaptive remodelling following angioplasty: a role for CTGF

AIMS

Although transforming growth factor-beta (TGF-beta) is believed to stimulate intimal hyperplasia after arterial injury, its role in remodelling remains unclear. We investigate whether Smad3, a TGF-beta signalling protein, might facilitate its effect on remodelling.

METHODS AND RESULTS

Using the rat carotid angioplasty model, we assess Smad3 expression following arterial injury. We then test the effect of arterial Smad3 overexpression on the response to injury, and use a conditioned media experimental design to confirm an Smad3-dependent soluble factor that mediates this response. We use small interfering RNA (siRNA) to identify this factor as connective tissue growth factor (CTGF). Finally, we attempt to replicate the effect of medial Smad3 overexpression through adventitial application of recombinant CTGF. Injury induced medial expression of Smad3; overexpression of Smad3 caused neointimal thickening and luminal expansion, suggesting adaptive remodelling. Smad3 overexpression, though exclusively medial, caused adventitial changes: myofibroblast transformation, proliferation, and collagen production, all of which are associated with adaptive remodelling. Supporting the hypothesis that Smad3 initiated remodelling and these adventitial changes via a secreted product of medial smooth muscle cells (SMCs), we found that media conditioned by Smad3-expressing recombinant adenoviral vector (AdSmad3)-infected SMCs stimulated adventitial fibroblast transformation, proliferation, and collagen production in vitro. This effect was attenuated by pre-treatment of SMCs with siRNA specific for CTGF, abundantly produced by AdSmad3-infected SMCs, and significantly up-regulated in Smad3-overexpressing arteries. Moreover, periadventitial administration of CTGF replicated the effect of medial Smad3 overexpression on adaptive remodelling and neointimal hyperplasia.

CONCLUSION

Medial gene transfer of Smad3 promotes adaptive remodelling by indirectly influencing the behaviour of adventitial fibroblasts. This arterial cell-cell communication is likely to be mediated by Smad3-dependent production of CTGF.

Exercise training decreases the size and alters the composition of the neointima in a porcine model of percutaneous transluminal coronary angioplasty (PTCA)

Exercise training (EX) following percutaneous transluminal coronary angiography (PTCA) reduces progression to restenosis and increases event-free survival rates. Our aim was to determine whether EX inhibits lesion development and/or alters the extracellular matrix (ECM) composition of the neointima (NI) in a porcine PTCA model. Miniature Yucatan swine were assigned to cage confinement (SED) or EX for 20 wk. After 16 wk, all animals underwent a PTCA procedure of the left anterior descending artery (LAD) and left circumflex artery (LCX), with subsequent placement of an externalized jugular catheter. Animals recovered for 2 days and then resumed the previous protocol of SED or EX. Twelve days following PTCA, all animals received an intravenous bromodeoxyuridine (BrdU) injection to label proliferating cells. At 28 days following PTCA, the animals were euthanized, the LAD and LCX excised, and underwent standard histological processing for total collagen, type I collagen, fibronectin, BrdU, and Verhoeff-van Gieson stain. Our results demonstrate that EX significantly decreased lesion size and NI proliferation (-48%) in the LAD (P < 0.05) but not the LCX. Furthermore, EX attenuated type I collagen expression only in LAD, whereas total collagen was increased (5.9%) and fibronectin was decreased (-7.9%) in the NI of both vessels (P < 0.05). In conclusion, EX following PTCA may increase event-free survival rates following PTCA by decreasing lesion size and altering ECM composition.

Adenovirus-mediated gene transfer of fibromodulin inhibits neointimal hyperplasia in an organ culture model of human saphenous vein graft disease

Poor long-term graft patency remains a major limitation of coronary artery bypass grafting using saphenous vein aortocoronary grafts. Neointimal hyperplasia (NIH) represents the principal mechanism of graft failure; a substantial body of evidence implicates transforming growth factor-beta1 (TGF-beta1) in the pathogenesis of NIH. The small leucine-rich proteoglycans decorin and fibromodulin possess TGF-beta-antagonist activity to differing extents and with differing avidities for the isoforms of TGF-beta. We compared their ability to inhibit NIH in an ex vivo model of human saphenous vein organ culture following adenovirus-mediated gene transfer. Surgically prepared human saphenous vein segments received adenovirus expressing fibromodulin (Ad5-Fmod), decorin (Ad5-Dcn), beta-galactosidase (Ad5-lacZ) or vehicle-only. Computerized morphometry 14 days after infection revealed significantly reduced neointimal area, neointimal thickness and intima/media ratio in Ad5-Fmod- and Ad5-Dcn-infected veins. Each parameter was significantly smaller in Ad5-Fmod- than in Ad5-Dcn-exposed segments. Fibrillar collagen content and levels of biologically active TGF-beta were lower in vessels receiving Ad5-Fmod or Ad5-Dcn than in those receiving Ad5-lacZ or vehicle-only. Fibromodulin is a more potent inhibitor of NIH in cultured human saphenous vein than decorin and offers potential therapeutic benefits in saphenous vein graft failure (and possibly in other forms of accelerated atherosclerosis) by reduction of associated neointima formation.

Effects of adeno-associated virus (AAV) of transforming growth factors beta1 and beta3 (TGFbeta1,3) on promoting synthesis of glycosaminoglycan and collagen type II of dedifferentiated nucleus pulposus (NP) cells

The effects of AAV-TGFbeta(1) and AAV-TGFbeta(3) on promoting synthesis of glycosaminoglycan and collagen type II of dedifferentiated rabbit lumbar disc NP cells were studied in this work. The rabbit lumbar disc NP cells were isolated and cultured. The earlier and later dedifferentiated NP cells were established by subculture. The AAV transfection efficiency to dedifferentiated NP cells was analyzed with AAV-EGFP in vitro. After dedifferentiated NP cells were transfected by AAV-TGFbeta(1) or AAV-TGFbeta(3), their biological effects on promoting synthesis of glycosaminoglycan or collagen type II were detected and compared by the methods of (35)S incorporation or immunoblotting. The experimental results showed that AAV could transfect efficiently the earlier dedifferentiated NP cells, but its transfection rate was shown to be at a low level to the later dedifferentiated NP cells. Both AAV-TGFbeta(1) and AAV-TGFbeta(3) could promote the earlier dedifferentiated NP cells to synthesize glycosaminoglycan and collagen type II, and the effect of AAV-TGFbeta(1) was better than that of AAV-TGFbeta(3). For the later dedifferentiated NP cells, the AAV-TGFbeta(3) could promote their synthesis, but AAV-TGFbeta(1) could slightly inhibit their synthesis. Therefore, AAV-TGFbeta(1) and AAV-TGFbeta(3) could be used for the earlier dedifferentiated NP cells, and the TGFbeta(3) could be used as the objective gene for the later dedifferentiated NP cells.

Rosiglitazone Suppresses Cyclosporin-Induced Chronic Transplant Dysfunction and Prolongs Survival of Rat Cardiac Allografts

BACKGROUND

The lack of effective treatment for chronic transplant dysfunction restricts the long-term survival of solid organ allografts. Peroxisome proliferator-activated receptor ligands can suppress vascular inflammation. The aim of this study was to analyze the effects of rosiglitazone on chronic transplant dysfunction in a rat cardiac transplant model.

METHODS

Inbred male Fisher 344 (F344, RT1lvl) and Lewis (LEW, RT1(1)) rats were subjected to heterotopic abdominal heart transplantation according to standard procedures. Cyclosporine A was administered intraperitoneally to cover acute rejection, and rosiglitazone was administered orally by gavage daily from 3 days before the operation to the end of experiments.

RESULTS

Rosiglitazone significantly prolonged the survival of cardiac allografts in rats (F344 to LEW) that had received a 10-day course of cyclosporin A compared to treatment with immunosuppressant alone. Analysis of allografts at 120 days posttransplantation showed that rosiglitazone reduced the inflammatory cell infiltrate in both the vessels and graft parenchyma as were neointimal formation, vascular occlusion, and fibrosis. Expression of transforming growth factor-beta and related proteins was less abundant after cyclosporin A/rosiglitazone treatment.

CONCLUSIONS

The findings reported here demonstrate that rosiglitazone given under the cover of short-term treatment with cyclosporin A prolongs cardiac allograft survival and reduces the severity of chronic transplant dysfunction. This may be mediated in part through the downregulation of transforming growth factor-beta and related proteins. The combined effects of rosiglitazone and immunosuppressive drugs are potentially beneficial to patients receiving organ transplants.

TGF-beta- and CTGF-mediated fibroblast recruitment influences early outward vein graft remodeling

Luminal shearing forces have been shown to impact both geometric remodeling and the development of intimal hyperplasia. Less well studied is the influence of intramural wall stresses on vessel growth and adaptation. Using a vein graft-fistula configuration to isolate the impact of circumferential wall stress, we identify the reorganization of adventitial myofibroblasts as the dominant histological event that limits early outward remodeling of vein grafts in response to elevated wall stress. We hypothesize that increased production of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) induces recruitment of myofibroblasts, promotes adventitial reorganization, and limits early outward remodeling in response to increased intramural wall stress. Vein grafts with a distal arteriovenous fistula in the neck of rabbits were constructed, resulting in a fourfold differential in circumferential wall stress. Using this model, we demonstrate 1) elevated wall stress augments the production of TGF-beta and CTGF, 2) increased TGF-beta expression and CTGF expression are correlated with the enhanced differentiation from fibroblasts to myofibroblasts, as evidenced by the significant increase in the alpha-actin-positive cells in adventitia, and 3) the levels of TGF-beta, CTGF, and alpha-actin are inversely correlated with the magnitude of outward remodeling of the graft wall. Increased wall stress after vein graft implantation appears to induce a TGF-beta- and CTGF-mediated recruitment of adventitial fibroblasts and a conversion to a myofibroblast phenotype. Although important in the maintenance of wall stability in the face of an increased mechanical load, this adventitial adaptation limits early outward remodeling of the vein conduit and may prove deleterious in maintaining long-term vein graft patency.

Adventitial VEGF165 gene transfer prevents lumen loss through induction of positive arterial remodeling after PTCA in porcine coronary arteries

Negative arterial remodeling still plays an important role in the pathogenesis of coronary restenosis even in the era of interventional stenting (e.g. arterial narrowing occurs proximal and distal of a stented segment). Previous studies suggest that increased angiogenesis and inhibited regression of injury-induced adventitial microvessels prevents negative remodeling. We have examined the effect of local vascular endothelial growth factor (VEGF(165)) gene transfer on adventitial microvessel angiogenesis/regression and arterial remodeling after coronary angioplasty. Twenty pigs underwent angioplasty, each one in two major coronary arteries, followed by plasmid liposome gene transfer with either VEGF(165) or control gene LacZ (50 microg DNA with 50 microg of Lipofectine) into the (peri)adventitial space using a needle injection catheter. Arteries were examined at days 1, 7, 14, and 28. Local delivery of VEGF(165) gene into the outer compartments of balloon-injured porcine coronary arteries reduced lumen area loss due to distinct positive remodeling (arterial enlargement). Prevention of adventitial microvessel regression, enhanced adventitial elastin accumulation, reduced adventitial myofibroblast numbers, and a pronounced adventitial inflammatory response considered as a part of arterial healing seem to be the main VEGF-mediated mechanisms indicating the therapeutic potential of VEGF for restenosis prevention.

Increased plasma monocyte chemoattractant protein-1 level in idiopathic pulmonary arterial hypertension

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1), a pro-inflammatory chemokine, has potent chemoattractant activity for monocytes/macrophages. We sought to investigate the clinical significance of MCP-1 in idiopathic pulmonary arterial hypertension (IPAH).

METHODS

This study included 28 patients with IPAH, seven patients with pulmonary arterial hypertension (PAH) related to collagen vascular disease, and 13 healthy subjects. Plasma MCP-1 levels were measured together with serum IL-6 and tumour necrosis factor-alpha (TNF-alpha) levels.

RESULTS

Circulating levels of MCP-1, IL-6 and TNF-alpha were significantly higher in patients with IPAH than in healthy controls, although they were lower than in patients with PAH related to collagen vascular disease. Plasma MCP-1 did not significantly correlate with any haemodynamic variables. However, plasma MCP-1 levels correlated negatively with the disease duration (time from symptom onset).

CONCLUSIONS

Plasma MCP-1 levels were elevated in patients with IPAH, and this elevation was particularly marked in the early stage of disease. Taking into account the chemoattractant activity of MCP-1, these results imply a contribution of MCP-1 to the development of pulmonary hypertension.

In Vivo Attenuation of Myointimal Hyperplasia Using Transforming Growth Factor-Beta3 in an Interposition Graft Model

PURPOSE

To examine if transforming growth factor-beta3 (TGFbeta3) can attenuate the development of para-anastomotic myointimal hyperplasia in an animal model of small-diameter vascular graft failure.

METHODS

Under general anesthesia, 10 adult goats underwent bilateral polyurethane interposition graft insertion in the carotid position. Following completion of the anastomoses, each artery received adventitial infiltration of 50 ng of TGFbeta3 around the anastomoses; a placebo was administered to the other side. Postoperatively, each animal received 150 mg of aspirin daily. The arteries were explanted, half at 6 weeks and the remaining 5 at 3 months, for histological examination.

RESULTS

Vessel wall thickness surrounding the anastomosis was reduced by 37% in TGFbeta3-treated arteries compared to placebo at 6 weeks and 3 months, principally due to reduced smooth muscle cell proliferation. There was decreased overall luminal loss on angiography. Total collagen content was not significantly different between TGFbeta3 and placebo sides. Further analysis for the subendothelial matrix component collagen type VIII showed decreased levels on the treated side. Total elastin content was reduced on the TGFbeta3-treated side.

CONCLUSION

Direct single-dose subadventitial infiltration of TGFbeta3 following insertion of an interposition graft reduces SMC proliferation and elastin content. It would appear that TGFbeta3 holds promise as a prophylaxis against the development of myointimal hyperplasia, the predominant cause of graft failure in peripheral bypass surgery.

Reduction of myointimal hyperplasia after arterial anastomosis by local injection of transforming growth factor beta3

BACKGROUND

The transforming growth factor (TGF)-beta family of cytokines exerts pleiotropic actions on vascular smooth muscle cell phenotype, proliferation, and extracellular matrix synthesis. This in vivo study assessed the use of TGF-beta3 in attenuating the development of postanastomotic smooth muscle cell proliferation.

METHODS

Under general anesthesia, 10 adult goats underwent transection and reanastomosis of both common carotid arteries. After reanastomosis, one artery was infiltrated with 50 ng of TGF-beta3 in 100 microL of pH buffer around the anastomosis, and the other side was infiltrated with buffer only. After surgery, each animal received 150 mg of aspirin daily. The arteries were explanted after 3 months for histologic examination.

RESULTS

Vessel wall thickness surrounding the anastomosis was reduced by 30% after TGF-beta3 treatment compared with placebo (P = .003), with a 20% (P = .002) reduction in cellular content. Although total collagen content was not significantly different between TGF-beta3 and placebo, collagen type VIII content was reduced around the TGF-beta3 anastomoses (P = .011). A reduction in the total elastin content (P = .003) and number of elastic fiber lamellae (P = .042) was found surrounding TGF-beta3-treated anastomoses, but not placebo-treated anastomosis. A 29% increase in vasa vasorum (P = .044) was present around TGF-beta3-treated anastomoses. No differences in inflammatory cell infiltration were seen between sides.

CONCLUSIONS

Direct subadventitial infiltration of TGF-beta3 immediately after creation of an arterial anastomosis attenuates cell proliferation, with a reduction in elastin and collagen type VIII content and vessel wall thickness.

Radiation therapy induced modulation of wound healing at experimental vein graft anastomoses

OBJECTIVES

The aim of this study was to investigate if radiation therapy (RT) favorably modulates wound healing at vein graft anastomoses.

MATERIALS AND METHODS

Jugular vein grafts were sewn into carotid arteries in 32 rats which were randomly divided into two groups: RT (gamma source, 14 Gray, n=16) and control (C, sham irradiation, n=16). Grafts and adjacent arteries were analyzed at 2 (n=8) and 8 weeks (n=8) by histology, immunohistochemistry, and morphometry.

RESULTS

Although, RT did not reduce the overall occurrence of intimal hyperplasia, the distribution differed. RT led to a reduction of intimal hyperplasia in arterial segments (median: C: 41.873 microm2; RT: 6.452 microm2, p < 0.0007). In contrast, RT augmented intimal hyperplasia in vein grafts (median: C: 30.287 microm2; RT: 90.455 microm2, p < 0.014). Vein graft diameters after RT were enlarged (median: C: 2.098 microm; RT: 3.381, p < 0.031). Over 80% of the cells were of mesenchymal origin in both groups.

CONCLUSIONS

RT reduced intimal hyperplasia in arterial segments. However, RT led to graft dilatation and increased intimal hyperplasia in vein grafts. RT did not favorably modulate the vascular wound healing response in this model.

Transforming growth factor-beta is activated by plasmin and inhibits smooth muscle cell death in human saphenous vein

BACKGROUND

The effect of activation of endogenous transforming growth factor-beta (TGF-beta) on smooth muscle cell apoptosis was assessed in human saphenous vein.

METHODS

Segments of human saphenous vein, obtained at the time of bypass graft surgery, were cultured for 14 days. During this time, smooth muscle cells accumulated in the intima as a result of proliferation and migration, partly counterbalanced by apoptotic cell death.

RESULTS

Addition of exogenous TGF-beta(1) had no effect on smooth muscle cell proliferation or apoptosis. However, antibody neutralization of endogenous TGF-beta(1) caused significant increases in smooth muscle cell death in the media and intima without any change in proliferation. A plasmin inhibitor (alpha-N-acetyl-L-lysine methyl ester), a specific urokinase-type plasminogen activator (uPA) inhibitor (amiloride) and an anti-catalytic anti-uPA antibody all caused decreases in the tissue content of active TGF-beta and increases in smooth muscle cell death in the media and intima.

CONCLUSIONS

These data suggest that the amount of TGF-beta in human saphenous vein is sufficient, when in the active form, to protect smooth muscle cells against apoptosis. Adding exogenous TGF-beta(1) has no beneficial effect, but decreasing the amount of active TGF-beta causes smooth muscle cells to undergo apoptosis. Plasmin, generated by uPA, appears to be an important activator of endogenous latent TGF-beta.

Local endovascular delivery, gene therapy, and cell transplantation for peripheral arterial disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

The role of transforming growth factor β1 in the vascular system

The transforming growth factor beta (TGFbeta) family of cytokines exert pleiotropic effects upon a wide variety of cell types. TGFbeta1 has been demonstrated to be of fundamental importance in the development, physiology and pathology of the vascular system. As the role of TGFbeta1 in these processes becomes clearer, influencing its activity for therapeutic benefit is now beginning to be investigated. This review presents an overview of the role of TGFbeta1 in the vasculature. The cellular and extracellular biology of the TGFbeta family is first addressed, followed by an overview of the function of TGFbeta1 during vascular development, atherogenesis, hypertension, and vessel injury.