Wild-type p53 gene transfer inhibits neointima formation in human saphenous vein by modulation of smooth muscle cell migration and induction of apoptosis

Old blood from heterochronic parabionts accelerates vascular aging in young mice: transcriptomic signature of pathologic smooth muscle remodeling

Vascular aging has a central role in the pathogenesis of cardiovascular diseases contributing to increased mortality of older adults. There is increasing evidence that, in addition to the documented role of cell-autonomous mechanisms of aging, cell-nonautonomous mechanisms also play a critical role in the regulation of vascular aging processes. Our recent transcriptomic studies (Kiss T. et al. Geroscience. 2020;42(2):727-748) demonstrated that circulating anti-geronic factors from young blood promote vascular rejuvenation in aged mice. The present study was designed to expand upon the results of this study by testing the hypothesis that circulating pro-geronic factors also contribute to the genesis of vascular aging phenotypes. To test this hypothesis, through heterochronic parabiosis, we determined the extent to which shifts in the vascular transcriptome (RNA-seq) are modulated by the old systemic environment. We reanalyzed existing RNA-seq data, comparing the transcriptome in the aorta arch samples isolated from isochronic parabiont aged (20-month-old) C57BL/6 mice [A-(A); parabiosis for 8 weeks] and young isochronic parabiont (6-month-old) mice [Y-(Y)] and also assessing transcriptomic changes in the aortic arch in young (6-month-old) parabiont mice [Y-(A); heterochronic parabiosis for 8 weeks] induced by the presence of old blood derived from aged (20-month-old) parabionts. We identified 528 concordant genes whose expression levels differed in the aged phenotype and were shifted towards the aged phenotype by the presence of old blood in young Y-(A) animals. Among them, the expression of 221 concordant genes was unaffected by the presence of young blood in A-(Y) mice. GO enrichment analysis suggests that old blood-regulated genes may contribute to pathologic vascular remodeling. IPA Upstream Regulator analysis (performed to identify upstream transcriptional regulators that may contribute to the observed transcriptomic changes) suggests that the mechanism of action of pro-geronic factors present in old blood may include inhibition of pathways mediated by SRF (serum response factor), insulin-like growth factor-1 (IGF-1) and VEGF-A. In conclusion, relatively short-term exposure to old blood can accelerate vascular aging processes. Our findings provide additional evidence supporting the significant plasticity of vascular aging and the existence of circulating pro-geronic factors mediating pathological remodeling of the vascular smooth muscle cells and the extracellular matrix.

The p53 pathway in vasculature revisited: A therapeutic target for pathological vascular remodeling?

Pathological vascular remodeling contributes to the development of restenosis following intraluminal interventions, transplant vasculopathy, and pulmonary arterial hypertension. Activation of the tumor suppressor p53 may counteract vascular remodeling by inhibiting aberrant proliferation of vascular smooth muscle cells and repressing vascular inflammation. In particular, the development of different lines of small-molecule p53 activators ignites the hope of treating remodeling-associated vascular diseases by targeting p53 pharmacologically. In this review, we discuss the relationships between p53 and pathological vascular remodeling, and summarize current experimental data suggesting that drugging the p53 pathway may represent a novel strategy to prevent the development of vascular remodeling.

Caloric Restriction Exacerbates Angiotensin II-Induced Abdominal Aortic Aneurysm in the Absence of p53

p53-dependent vascular smooth muscle cell senescence is a key pathological process of abdominal aortic aneurysm (AAA). Caloric restriction (CR) is a nonpharmacological intervention that prevents AAA formation. However, whether p53 is indispensable to the protective role of CR remains unknown. In this study, we investigated the necessity of p53 in the beneficial role of CR in AAA formation and the underlying mechanisms. We subjected p53^+/+ and p53^-/- mice to 12 weeks of CR and then examined the incidence of Ang II (angiotensin II)-induced AAA formation. We found that both CR and p53 knockout reduced Ang II-induced AAA formation; however, CR markedly increased the incidence of AAA formation and exacerbated aortic elastin degradation in p53^-/- mice, accompanied by increased vascular senescence, reactive oxygen species generation, and reduced energy production. Analysis of mitochondrial respiratory activity revealed that dysfunctional complex IV accounts for the abnormal mitochondrial respiration in p53^-/- vascular smooth muscle cells treated by CR serum. Mechanistically, ablation of p53 almost totally blocked the protective role of CR by inhibiting SCO2 (cytochrome C oxidase assembly protein 2)-dependent mitochondrial complex IV activity. Overexpression of SCO2 restored the beneficial effect of CR on antagonizing Ang II-induced expression of AAA-related molecules and reactive oxygen species generation in p53^-/- vascular smooth muscle cells. Together, our findings demonstrate that the existence of p53 in vascular smooth muscle cells is critical to the protective role of CR in Ang II-induced AAA formation by maintaining an appropriate mitochondrial function.

p53 plays a crucial role in endothelial dysfunction associated with hyperglycemia and ischemia

p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evidence that p53 is activated with aging. Such activation has been reported to contribute to various age-associated pathologies, but its role in vascular dysfunction is largely unknown. The aim of this study was to investigate whether activation of endothelial p53 has a pathological effect in relation to endothelial function. We established endothelial p53 loss-of-function and gain-of-function models by breeding endothelial-cell specific Cre mice with floxed Trp53 or floxed Mdm2/Mdm4 mice, respectively. Then we induced diabetes by injection of streptozotocin. In the diabetic state, endothelial p53 expression was markedly up-regulated and endothelium-dependent vasodilatation was significantly impaired. Impairment of vasodilatation was significantly ameliorated in endothelial p53 knockout (EC-p53 KO) mice, and deletion of endothelial p53 also significantly enhanced the induction of angiogenesis by ischemia. Conversely, activation of endothelial p53 by deleting Mdm2/Mdm4 reduced both endothelium-dependent vasodilatation and ischemia-induced angiogenesis. Introduction of p53 into human endothelial cells up-regulated the expression of phosphatase and tensin homolog (PTEN), thereby reducing phospho-eNOS levels. Consistent with these results, the beneficial impact of endothelial p53 deletion on endothelial function was attenuated in EC-p53 KO mice with an eNOS-deficient background. These results show that endothelial p53 negatively regulates endothelium-dependent vasodilatation and ischemia-induced angiogenesis, suggesting that inhibition of endothelial p53 could be a novel therapeutic target in patients with metabolic disorders.

Functional pathways associated with human carotid atheroma: a proteomics analysis

Advances in large-scale analysis are becoming very useful in understanding health and disease. Here, we used high-throughput mass spectrometry to identify differentially expressed proteins between early and advanced lesions. Carotid endarterectomy samples were collected and dissected into early and advanced atherosclerotic lesion portions. Proteins were extracted and subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Differentially expressed proteins were identified and verified using multiple reaction monitoring (MRM), on which advanced systems biology and enrichment analyses were performed. The identified proteins were further compared to the transcriptomic data of 32 paired samples obtained from early and advanced atherosclerotic lesions. A total of 95 proteins were upregulated, and 117 proteins were downregulated in advanced lesions compared to early atherosclerotic lesions (p < 0.05). The upregulated proteins were associated with proatherogenic processes, whereas downregulated proteins were involved in extracellular matrix organization and vascular smooth muscle cytoskeleton. Many of the identified proteins were linked to various "upstream regulators", among which TGFβ had the highest connections. Specifically, a total of 19 genes were commonly upregulated, and 30 genes were downregulated at the mRNA and protein levels. These genes were involved in vascular smooth muscle cell activity, for which enriched transcription factors were identified. This study deciphers altered pathways in atherosclerosis and identifies upstream regulators that could be candidate targets for treatment.

Teniposide regulates the phenotype switching of vascular smooth muscle cells in a miR-21-dependent manner

The switch of vascular smooth muscle cells (SMCs) from the contractile phenotype to proliferative one can make contributions to atherosclerosis and neointima formation. MiR-21 can prevent the rupture of advanced lesion plaques. We previously reported the protection of DNA topoisomerase II (Topo II) inhibitors against atherosclerosis and vascular calcification. However, it remains unknown if Topo II inhibitors can change SMC phenotypes. Herein, we show that teniposide protected SMC phenotype switching during atherosclerosis by enhancing expression of smooth muscle α-actin (SMA) while reducing osteopontin (OPN) expression in aortic lesion plaques. In vitro, teniposide induced expression of smooth muscle protein 22-α and calponin 1, but inhibited expression of OPN and epiregulin in human aortic SMCs (HASMCs). Moreover, teniposide attenuated platelet derived growth factor-BB-induced HASMC proliferation and migration. Mechanistically, the effect of teniposide on SMC phenotypes was completed, at least in part, by activating miR-21 expression. In addition, teniposide ameliorated ligation-induced carotid artery remodeling in C57BL/6J mice by regulating SMA and OPN expression. Taken together, our study demonstrates that teniposide regulates SMC phenotype switching by upregulating expression of contractile genes in a miR-21-dependent manner, and this function is an important anti-atherogenic mechanism of teniposide.

Carotid artery ligation induced intimal thickening and proliferation is unaffected by ageing

Following interventions to treat atherosclerosis, such as coronary artery bypass graft surgery, restenosis occurs in approximately 40% of patients. Identification of proteins regulating intimal thickening could represent targets to prevent restenosis. Our group previously demonstrated that in a murine model of vascular occlusion, Wnt4 protein expression and β-catenin signalling was upregulated which promoted vascular smooth muscle cell (VSMC) proliferation and intimal thickening. In this study, the effect of age on VSMC proliferation, intimal hyperplasia and Wnt4 expression was investigated. In vitro proliferation of VSMCs isolated from young (2 month) or old (18-20 month) C57BL6/J mice was assessed by immunocytochemistry for EdU incorporation. As previously reported, 400 ng/mL recombinant Wnt4 protein increased proliferation of VSMCs from young mice. However, this response was absent in VSMCs from old mice. As our group previously reported reduced intimal hyperplasia in Wnt4+/- mice compared to wildtype controls, we hypothesised that impaired Wnt4 signalling with age may result in reduced neointimal formation. To investigate this, carotid artery ligation was performed in young and old mice and neointimal area was assessed 21 days later. Surprisingly, neointimal area and percentage lumen occlusion were not significantly affected by age. Furthermore, neointimal cell density and proliferation were also unchanged. These data suggest that although Wnt4-mediated proliferation was impaired with age in primary VSMCs, carotid artery ligation induced neointimal formation and proliferation were unchanged in old mice. These results imply that Wnt4-mediated proliferation is unaffected by age in vivo, suggesting that therapeutic Wnt4 inhibition could inhibit restenosis in patients of all ages.

Tumor Protein p53 (TP53) Gene and Left Main Coronary Artery Disease

Patients with left main (LM) coronary artery disease (CAD) are at the highest risk of cardiovascular events. We evaluated possible gene polymorphisms of tumor protein 53 ( TP53, rs1042522, p.Arg72Pro) that can differentiate LM-CAD from patients with more peripheral CAD (MP-CAD) and healthy participants (control group) in 520 individuals (LM-CAD, n = 175; MP-CAD, n = 185; and control group, n = 160). Patients with LM-CAD had the lowest Arg/Arg genotype frequency (36.0%) compared with the MP-CAD (57.3%) and control groups (61.9%), P < .001 for both comparisons. Similarly, the Arg allele was more frequent in the control group than in patients with MP-CAD (78.8% vs 73.2%; P = .007) and LM-CAD (78.8% vs 64.0%; P < .001). The Arg/Pro genotype was more frequent in the LM-CAD group compared with the MP-CAD and control groups (56.0, 31.9, and 33.8, respectively, P < .001 for both comparisons). Furthermore, the frequency of Arg/Arg genotypes was the lowest in the LM-CAD group compared with the MP-CAD and control groups. Knowing that TP53 is an antioncogene protein that acts as a tumor suppressor and regulator of apoptosis, the lowest frequency of Arg/Arg genotype observed in these high-risk patients may indicate lower protection from the atherosclerosis process. Replication studies are needed to evaluate this association.

Inhibition of neddylation by MLN4924 improves neointimal hyperplasia and promotes apoptosis of vascular smooth muscle cells through p53 and p62

Targeting apoptosis of vascular smooth muscle cells (VSMCs) represents an attractive approach to diminish the occurrence of restenosis. Neddylation is a highly conserved post-translational modification process and inhibition of neddylation has been shown to regulate apoptosis of other cells. However, the impacts of neddylation inhibition on VSMCs and neointimal hyperplasia have not been studied. In our present study, we have shown that MLN4924, a selective inhibitor of NEDD8-activating enzyme (NAE), markedly inhibited neointimal hyperplasia and accumulation of VSMCs, whereas increased apoptosis in the vascular wall. In vitro studies revealed that MLN4924 induced G2/M arrest and apoptosis of human VSMCs. Knockdown of NAE1 had similar effects. MLN4924 upregulated p53 and p62 in human VSMCs. Knockdown of either p53 or p62 mitigated the impacts of MLN4924 on G2/M arrest and apoptosis. Moreover, p53 knockdown abolished MLN4924-induced upregulation of p62. Finally, smooth muscle p53 knockout mice were generated and subjected to femoral artery injury and MLN4924 treatment. Deficiency of p53 in smooth muscle blocked the effects of MLN4924 on neointimal hyperplasia and apoptosis. Together, our results revealed that neddylation inhibition induces apoptosis through p53 and p62 in VSMCs and improves neointimal hyperplasia mainly by promoting apoptosis through smooth muscle p53 in mice. These pre-clinical data provide strong translational implications for targeting restenosis by perturbation of neddylation using MLN4924.

Targeting Wnt/β-Catenin Activated Cells with Dominant-Negative N-cadherin to Reduce Neointima Formation

Approximately 50% of coronary artery bypass grafts using the autologous saphenous vein fail within 10 years due to intimal thickening. This study examined whether a gene therapy approach that selectively kills Wnt/β-catenin/T cell factor (TCF) activated vascular smooth muscle cells (VSMCs) using dominant-negative N-cadherin (dn-N-cadherin) reduced intimal thickening. Cultured human VSMCs infected with an adenovirus (Ad) encoding dn-N-cadherin via the TCF promoter (Ad-TOP-dn-N-cadherin) specifically expressed dn-N-cadherin in response to activation of the Wnt/β-catenin/TCF pathway. Infection with Ad-TOP-dn-N-cadherin significantly increased VSMC apoptosis (3 ± 0.2% versus 9 ± 0.7%; p < 0.05, n = 6) and significantly inhibited VSMC migration by 83 ± 15% (p < 0.05, n = 6), but did not affect VSMC proliferation (p > 0.05, n = 5). In an ex vivo human saphenous vein organ culture model, luminal delivery of Ad-TOP-dn-N-cadherin significantly increased VSMC apoptosis after 7 days of culture (4 ± 1.4% versus 9 ± 1.6%; p < 0.01, n = 6) and suppressed intimal thickening by 75 ± 7% (p < 0.05, n = 5), without a detrimental effect on endothelial cell coverage. In vivo, Ad-TOP-dn-N-cadherin significantly reduced intimal thickening at day 21 (n = 10) in comparison to the Ad-β-galactosidase (Ad-β-gal) control virus (n = 12, p < 0.05) in the mouse carotid artery ligation model. In summary, we have developed a novel approach to selectively reduce intimal thickening, which may be beneficial in reducing late vein graft failure.

Effects of p53-knockout in vascular smooth muscle cells on atherosclerosis in mice

In vitro and in vivo evidence has indicated that the tumor suppressor, p53, may play a significant role in the regulation of atherosclerotic plaque formation. In vivo studies using global knockout mice models, however, have generated inconclusive results that do not address the roles of p53 in various cell types involved in atherosclerosis. In this study, we have specifically ablated p53 in vascular smooth muscle cells (VSMC) in the ApoE^-/- mouse model to investigate the roles of p53 in VSMC in atherosclerotic plaque formation and stability. We found that p53 deficiency in VSMC alone did not affect the overall size of atherosclerotic lesions. However, there was a significant increase in the number of p53^-/- VSMC in the fibrous caps of atherosclerotic plaques in the early stages of plaque development. Loss of p53 results in migration of VSMC at a faster rate using wound healing assays and augments PDGF-induced formation of circular dorsal ruffles (CDR), known to be involved in cell migration and internalization of surface receptors. Furthermore, aortic VSMC from ApoE^-/- /p53^-/- mice produce significantly more podosomes and are more invasive. We conclude that p53^-/- VSMC are enriched in the fibrous caps of lesions at early stages of plaque formation, which is caused in part by an increase in VSMC migration and invasion as shown by p53^-/- VSMC in culture having significantly higher rates of migration and producing more CDRs and invasive podosomes.

Inhibition of Smooth Muscle β-Catenin Hinders Neointima Formation After Vascular Injury

OBJECTIVE

Smooth muscle cells (SMCs) contribute to neointima formation after vascular injury. Although β-catenin expression is induced after injury, whether its function is essential in SMCs for neointimal growth is unknown. Moreover, although inhibitors of β-catenin have been developed, their effects on SMC growth have not been tested. We assessed the requirement for SMC β-catenin in short-term vascular homeostasis and in response to arterial injury and investigated the effects of β-catenin inhibitors on vascular SMC growth.

APPROACH AND RESULTS

We used an inducible, conditional genetic deletion of β-catenin in SMCs of adult mice. Uninjured arteries from adult mice lacking SMC β-catenin were indistinguishable from controls in terms of structure and SMC marker gene expression. After carotid artery ligation, however, vessels from mice lacking SMC β-catenin developed smaller neointimas, with lower neointimal cell proliferation and increased apoptosis. SMCs lacking β-catenin showed decreased mRNA expression of Mmp2, Mmp9, Sphk1, and S1pr1 (genes that promote neointima formation), higher levels of Jag1 and Gja1 (genes that inhibit neointima formation), decreased Mmp2 protein expression and secretion, and reduced cell invasion in vitro. Moreover, β-catenin inhibitors PKF118-310 and ICG-001 limited growth of mouse and human vascular SMCs in a dose-dependent manner.

CONCLUSIONS

SMC β-catenin is dispensable for maintenance of the structure and state of differentiation of uninjured adult arteries, but is required for neointima formation after vascular injury. Pharmacological β-catenin inhibitors hinder growth of human vascular SMCs. Thus, inhibiting β-catenin has potential as a therapy to limit SMC accumulation and vascular obstruction.

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.

Fibroblast Growth Factor 12 Is a Novel Regulator of Vascular Smooth Muscle Cell Plasticity and Fate

OBJECTIVE

Vascular smooth muscle cells (VSMCs) modulate their phenotype between synthetic and contractile states in response to environmental changes; this modulation plays a crucial role in the pathogenesis of restenosis and atherosclerosis. Here, we identified fibroblast growth factor 12 (FGF12) as a novel key regulator of the VSMC phenotype switch.

APPROACH AND RESULTS

Using murine models and human specimens, we found that FGF12 was highly expressed in contractile VSMCs of normal vessel walls but was downregulated in synthetic VSMCs from injured and atherosclerotic vessels. In human VSMCs, FGF12 expression was inhibited at the transcriptional level by platelet-derived growth factor-BB. Gain- and loss-of-function experiments showed that FGF12 was both necessary and sufficient for inducing and maintaining the quiescent and contractile phenotypes of VSMCs. FGF12 inhibited cell proliferation through the p53 pathway and upregulated the key factors involved in VSMC lineage differentiation, such as myocardin and serum response factor. Such FGF12-induced phenotypic change was mediated by the p38 MAPK (mitogen-activated protein kinase) pathway. Moreover, FGF12 promoted the differentiation of mouse embryonic stem cells and the transdifferentiation of human dermal fibroblasts into SMC-like cells. Furthermore, adenoviral infection of FGF12 substantially decreased neointima hyperplasia in a rat carotid artery injury model.

CONCLUSIONS

In general, FGF family members induce a synthetic VSMC phenotype. Interestingly, the present study showed the unanticipated finding that FGF12 belonging to FGF family, strongly induced the quiescent and contractile VSMC phenotypes and directly promoted VSMC lineage differentiation. These novel findings suggested that FGF12 could be a new therapeutic target for treating restenosis and atherosclerosis.

Soluble N-cadherin: A novel inhibitor of VSMC proliferation and intimal thickening

Reoccurrence of symptoms occurs in 30-50% of coronary artery disease patients receiving vein grafts or bare-metal stents due to intimal thickening (restenosis). Restenosis is caused by vascular smooth muscle cell (VSMC) migration and proliferation. New therapeutic approaches that reduce VSMC migration and proliferation while promoting endothelial cell (EC) coverage are required. We assessed the effect of a soluble form of N-cadherin (SNC-Fc, a fusion of the extracellular portion of N-Cadherin to a mutated Fc fragment of IgG), a cell-cell junction molecule, on human saphenous VSMC proliferation and migration in vitro. We also assessed its effect on intimal thickening in a validated human ex vivo organ culture model. We observed that SNC-Fc significantly inhibited VSMC proliferation and to a lesser extent migration. The anti-proliferative effect of SNC-Fc was mediated by the interaction of SNC-Fc with the FGFR, rather than through inhibition of β-catenin signalling. SNC-Fc also significantly reduced intimal thickening by ~85% in the ex vivo organ culture model. SNC-Fc treatment inhibited proliferation of the intimal cells but did not affect migration. SNC-Fc reduced EC apoptosis, without detrimental effects on EC proliferation and migration in vitro. Importantly SNC-Fc increased EC coverage in the ex vivo model of intimal thickening. In conclusion, we suggest that SNC-Fc may have potential as an anti-proliferative therapeutic agent for reducing restenosis which has no detrimental effects on endothelial cells.

Efficient transduction of primary vascular cells by the rare adenovirus serotype 49 vector

Neointima formation and vascular remodeling through vascular smooth muscle cell migration and proliferation can limit the long-term success of coronary interventions, for example, in coronary artery bypass grafting (CABG). Ex vivo gene therapy has the potential to reduce unnecessary cell proliferation and limit neointima formation in vascular pathologies. To date, the species C adenovirus serotype 5 has been commonly used for preclinical gene therapy; however, its suitability is potentially limited by relatively poor tropism for vascular cells and high levels of preexisting immunity in the population. To avoid these limitations, novel species of adenovirus are being tested; here we investigate the potential of adenovirus 49 (Ad49) for use in gene therapy. Transduction of primary human vascular cells by a range of adenovirus serotypes was assessed; Ad49 demonstrated highest transduction of both vascular smooth muscle and endothelial cells. Gene transfer with Ad49 in vascular smooth muscle and endothelial cells was possible following short exposure times (<1 hr) and with low MOI, which is clinically relevant. Ex vivo delivery to surplus CABG tissue showed efficient gene transfer with Ad49, consistent with the in vitro findings. Luminal infusion of Ad49GFP into intact CABG samples ex vivo resulted in efficient vessel transduction. In addition, no seroprevalence rates to Ad49 were observed in a Scottish cohort of patients from cardiovascular clinics, thus circumventing issues with preexisting immunity. Our results show that Ad49 has tropism for vascular cells in vitro and ex vivo and demonstrate that Ad49 may be an improved vector for local vascular gene therapy compared with current alternatives.

Pseudotyping the adenovirus serotype 5 capsid with both the fibre and penton of serotype 35 enhances vascular smooth muscle cell transduction

Ex vivo gene therapy during coronary artery bypass grafting (CABG) holds great potential to prevent excessive smooth muscle cell (SMC) proliferation, neointima formation and graft failure. The most successful preclinical strategies to date have utilised vectors based on the species C adenovirus, Ad5, which engages the Coxsackie and Adenovirus receptor (CAR) as its primary attachment receptor. Profiling receptors on human SMCs demonstrated the absence of CAR but substantial expression of the species B receptor CD46. We performed transduction experiments using Ad5 and the CD46-utilising adenovirus Ad35, and found Ad35 significantly more efficient at transducing SMCs. To evaluate whether transduction could be further augmented, we evaluated chimeric CD46-utilising Ad5/Ad35 vectors comprising the Ad5 capsid pseudotyped with the Ad35 fibre alone (Ad5/F35) or in combination with the Ad35 penton (Ad5/F35/P35). In human smooth muscle cells (hSMCs), Ad5/F35/P35 mediated significantly higher levels of transduction than either parental vector or Ad5/F35. Ex vivo transduction experiments using mouse aortas from CD46 transgenics demonstrated that Ad5/F35/P35 was significantly more efficient at transducing SMCs than the other vectors tested. Finally, ex vivo transduction and immunofluorescent colocalisation experiments using human tissue from CABG procedures confirmed the preclinical potential of Ad5/F35/P35 as an efficient vector for vascular transduction during CABG.

Integrase-deficient lentiviral vectors mediate efficient gene transfer to human vascular smooth muscle cells with minimal genotoxic risk

We have previously shown that injury-induced neointima formation was rescued by adenoviral-Nogo-B gene delivery. Integrase-competent lentiviral vectors (ICLV) are efficient at gene delivery to vascular cells but present a risk of insertional mutagenesis. Conversely, integrase-deficient lentiviral vectors (IDLV) offer additional benefits through reduced mutagenesis risk, but this has not been evaluated in the context of vascular gene transfer. Here, we have investigated the performance and genetic safety of both counterparts in primary human vascular smooth muscle cells (VSMC) and compared gene transfer efficiency and assessed the genotoxic potential of ICLVs and IDLVs based on their integration frequency and insertional profile in the human genome. Expression of enhanced green fluorescent protein (eGFP) mediated by IDLVs (IDLV-eGFP) demonstrated efficient transgene expression in VSMCs. IDLV gene transfer of Nogo-B mediated efficient overexpression of Nogo-B in VSMCs, leading to phenotypic effects on VSMC migration and proliferation, similar to its ICLV version and unlike its eGFP control and uninfected VSMCs. Large-scale integration site analyses in VSMCs indicated that IDLV-mediated gene transfer gave rise to a very low frequency of genomic integration compared to ICLVs, revealing a close-to-random genomic distribution in VSMCs. This study demonstrates for the first time the potential of IDLVs for safe and efficient vascular gene transfer.

Preventing intimal thickening of vein grafts in vein artery bypass using STAT-3 siRNA

BACKGROUND

Proliferation and migration of vascular smooth muscle cells (VSMCs) play a key role in neointimal formation which leads to restenosis of vein graft in venous bypass. STAT-3 is a transcription factor associated with cell proliferation. We hypothesized that silencing of STAT-3 by siRNA will inhibit proliferation of VSMCs and attenuate intimal thickening.

METHODS

Rat VSMCs were isolated and cultured in vitro by applying tissue piece inoculation methods. VSMCs were transfected with STAT 3 siRNA using lipofectamine 2000. In vitro proliferation of VSMC was quantified by the MTT assay, while in vivo assessment was performed in a venous transplantation model. In vivo delivery of STAT-3 siRNA plasmid or scramble plasmid was performed by admixing with liposomes 2000 and transfected into the vein graft by bioprotein gel applied onto the adventitia. Rat jugular vein-carotid artery bypass was performed. On day 3 and7 after grafting, the vein grafts were extracted, and analyzed morphologically by haematoxylin eosin (H&E), and assessed by immunohistochemistry for expression of Ki-67 and proliferating cell nuclear antigen (PCNA). Western-blot and reverse transcriptase polymerase chain reaction (RT-PCR) were used to detect the protein and mRNA expression in vivo and in vitro. Cell apoptosis in vein grafts was detected by TUNEL assay.

RESULTS

MTT assay shows that the proliferation of VSMCs in the STAT-3 siRNA treated group was inhibited. On day 7 after operation, a reduced number of Ki-67 and PCNA positive cells were observed in the neointima of the vein graft in the STAT-3 siRNA treated group as compared to the scramble control. The PCNA index in the control group (31.3 ± 4.7) was higher than that in the STAT-3 siRNA treated group (23.3 ± 2.8) (P < 0.05) on 7d. The neointima in the experimental group(0.45 ± 0.04 μm) was thinner than that in the control group(0.86 ± 0.05 μm) (P < 0.05).Compared with the control group, the protein and mRNA levels in the experimental group in vivo and in vitro decreased significantly. Down regulation of STAT-3 with siRNA resulted in a reduced expression of Bcl-2 and cyclin D1. However, apoptotic cells were not obviously found in all grafts on day 3 and 7 post surgery.

CONCLUSIONS

The STAT-3 siRNA can inhibit the proliferation of VSMCs in vivo and in vitro and attenuate neointimal formation.

p53 gene therapy modulates signal transduction in the apoptotic and cell cycle pathways downregulating neointimal hyperplasia

PURPOSE

To investigate the molecular mechanisms that lead to inhibition of intimal hyperplasia (IH) following p53 gene therapy.

METHODS

In vivo p53 gene transfer to balloon injured rat carotid arteries was performed by utilizing adenovirus. The relationship between p53, p21, retinoblastoma protein (Rb), B-cell lymphoma 2 (Bcl-2), Bax, and Bcl-x was examined by immunohistochemistry. Expression of cyclin D1, Fas/CD95, and poly(ADP-ribose)polymerase (PARP) was determined.

RESULTS

Our data indicate increased expression of p53 in the nuclei of vascular smooth muscle cells (VSMCs) in the media (P < .01) compared with the controls. In the treated animals, Bax and Bcl-x, p21, and Rb were significantly upregulated (P < .01). Immunoreactivity to Bcl-2 was observed only in the neointima of untreated groups at 14 days. An increased presence of Fas and decreased expression of PARP was observed in the cytoplasm of the VSMCs of p53-treated animals.

CONCLUSIONS

P53 gene transfer activated a battery of downstream effector genes whose products are directly involved in cell cycle arrest, DNA repair, and apoptosis.

Inhibition of MDM2 attenuates neointimal hyperplasia via suppression of vascular proliferation and inflammation

AIMS

Tumour protein p53 plays an important role in the vascular remodelling process as well as in oncogenesis. p53 is negatively regulated by murine double minute 2 (MDM2). A recently developed MDM2 inhibitor, nutlin-3, is a non-genotoxic activator of the p53 pathway. So far, the effect of MDM2 inhibition on vascular remodelling has not been elucidated. We therefore investigated the effect of nutlin-3 on neointima formation.

METHODS AND RESULTS

Nutlin-3 up-regulated p53 and its downstream target p21 in vascular smooth muscle cells (VSMCs). DNA synthesis assay and flow cytometric analysis revealed that nutlin-3 inhibited platelet-derived growth factor (PDGF)-induced VSMC proliferation by cell cycle arrest. This inhibitory effect was abrogated in p53-siRNA-transfected VSMCs. Furthermore, nutlin-3 inhibited PDGF-stimulated VSMC migration. Treatment with nutlin-3 attenuated neointimal hyperplasia at 28 days after vascular injury in mice, associated with up-regulation of p53 and p21. BrdU incorporation was decreased at 14 days after injury in nutlin-3-treated mice. TUNEL assay showed that nutlin-3 did not exaggerate apoptosis of the injured vessels. Infiltration of macrophages and T-lymphocytes and mRNA expression of chemokine (C-C motif) ligand-5, interleukin-6, and intercellular adhesion molecule-1 were decreased in the injured vessels of nutlin-3-treated mice. Nutlin-3 suppressed NF-κB activation in VSMCs, but not in p53-siRNA-transfected VSMCs.

CONCLUSIONS

The MDM2 antagonist nutlin-3 inhibits VSMC proliferation, migration, and NF-κB activation, and also attenuates neointimal hyperplasia after vascular injury in mice, which is associated with suppression of vascular cell proliferation and an inflammatory response. Targeting MDM2 might be a potential therapeutic strategy for the treatment of vascular proliferative diseases.

Over-expression of mitogen-activated protein kinase phosphatase-2 enhances adhesion molecule expression and protects against apoptosis in human endothelial cells

BACKGROUND AND PURPOSE

We assessed the effects of over-expressing the dual-specific phosphatase, mitogen-activated protein (MAP) kinase phosphatase-2 (MKP-2), in human umbilical vein endothelial cells (HUVECs) on inflammatory protein expression and apoptosis, two key features of endothelial dysfunction in disease.

EXPERIMENTAL APPROACHES

We infected HUVECs for 40 h with an adenoviral version of MKP-2 (Adv.MKP-2). Tumour necrosis factor (TNF)-α-stimulated phosphorylation of MAP kinase and protein expression was measured by Western blotting. Cellular apoptosis was assayed by FACS.

KEY RESULTS

Infection with Adv.MKP-2 selectively abolished TNF-α-mediated c-Jun-N-terminal kinase (JNK) activation and had little effect upon extracellular signal-regulated kinase or p38 MAP kinase. Adv.MKP-2 abolished COX-2 expression, while induction of the endothelial cell adhesion molecules, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), two NFκB-dependent proteins, was not affected. However, when ICAM and VCAM expression was partly reduced by blockade of the NFκB pathway, Adv.MKP-2 was able to reverse this inhibition. This correlated with enhanced TNF-α-induced loss of the inhibitor of κB (IκB)α loss, a marker of NFκB activation. TNF-α in combination with NFκB blockade also increased HUVEC apoptosis; this was significantly reversed by Adv.MKP-2. Protein markers of cellular damage and apoptosis, H2AX phosphorylation and caspase-3 cleavage, were also reversed by MKP-2 over-expression.

CONCLUSIONS AND IMPLICATIONS

Over-expression of MKP-2 had different effects upon the expression of inflammatory proteins due to a reciprocal effect upon JNK and NFκB signalling, and also prevented TNF-α-mediated endothelial cell death. These properties may make Adv.MKP-2 a potentially useful future therapy in cardiovascular diseases where endothelial dysfunction is a feature.

Inhibition of N-cadherin retards smooth muscle cell migration and intimal thickening via induction of apoptosis

Objectives

Inhibition of vascular smooth muscle cell (VSMC) migration is a potential strategy for reducing intimal thickening during in-stent restenosis and vein graft failure. In this study, we examined the effect of disrupting the function of the VSMC adhesion molecule, N-cadherin, using antagonists, neutralizing antibodies, and a dominant negative, on VSMC migration and intimal thickening. Migration was assessed by the scratch-wound assay of human saphenous vein VSMCs and in a human saphenous vein ex vivo organ culture model of intimal thickening.

Results

Inhibition of cadherin function using a pan-cadherin antagonist, significantly reduced migration by 53% ± 8% compared with the control peptide (n = 3; P < .05). Furthermore, inhibition of N-cadherin function with an N-cadherin antagonist, neutralizing antibodies, and adenoviral expression of dominant negative N-cadherin (RAd dn-N-cadherin), significantly reduced migration by 31% ± 2%, 23% ± 1% and 32% ± 7% compared with controls, respectively (n = 3; P < .05). Inhibition of cadherin function significantly increased apoptosis by between 1.5- and 3.3-fold at the wound edge. In an ex vivo model of intimal thickening, inhibition of N-cadherin function by infection of human saphenous vein segments with RAd dn-N-cadherin significantly reduced VSMC migration by 55% and increased VSMC apoptosis by 2.7-fold. As a result, intimal thickening was significantly suppressed by 54% ± 14%. Importantly, there was no detrimental effect of dn-N-cadherin on endothelial coverage; in fact, it was significantly increased, as was survival of cultured human saphenous vein endothelial cells.

Conclusions

Under the condition of this study, cell-cell adhesion mediated by N-cadherin regulates VSMC migration via modulation of viability. Interestingly, inhibition of N-cadherin function significantly retards intimal thickening via inhibition of VSMC migration and promotion of endothelial cell survival. We suggest that disruption of N-cadherin-mediated cell-cell contacts is a potential strategy for reducing VSMC migration and intimal thickening.

Intimal thickening occurs in a large number of coronary artery vein grafts, lower extremity vein grafts, and stented arteries and is therefore a significant clinical problem. Intimal thickening is caused by migration of vascular smooth muscle cells (VSMC) from the intima to the media where they proliferate. In this study, we have shown that inhibition of the function of N-cadherin (a cell-cell contact protein) significantly retards VSMC migration and intimal thickening, while promoting endothelial coverage, and may therefore be clinically useful for treating intimal thickening.

p53 Levels positively correlate with carotid intima-media thickness in patients with subclinical atherosclerosis

BACKGROUND

The level of circulating p53 is related to inflammation in asymptomatic subjects with cardiovascular risk factors. Whether p53 is associated with the severity of atherosclerosis remains to be determined.

HYPOTHESIS

This study examines the relationship of systemic p53 levels with atherosclerotic risk factors and subclinical atherosclerosis.

METHODS

Circulating levels of p53 and markers of inflammation were measured in 356 subjects with cardiovascular risk factors but who were free from clinical cardiovascular disease. Subclinical atherosclerosis was evaluated by both the mean carotid intima-media thickness (IMT) and the presence of atherosclerotic plaques with the use of B-mode ultrasound in all subjects.

RESULTS

p53 levels were positively correlated with age (r = 0.382, P < 0.001), intercellular adhesion molecular-1 (ICAM-1; r = 0.510, P < 0.01), vascular cell adhesion molecular-1 (VCAM-1; r = 0.497, P < 0.01), E-selectin (r = 0.337, P < 0.01), and carotid IMT (r = 0.594, P < 0.01). The association between p53 and IMT remained significant in multiple regression analysis (P < 0.01) when controlling for traditional atherosclerotic risk factors and inflammatory markers.

CONCLUSION

Higher plasma p53 levels were associated with an increase in inflammatory markers, as well as increased carotid IMT. Circulating p53 may be useful in identifying subclinical atherosclerosis in subjects symptomatically free from cardiovascular disease.

DNA damage and repair in a model of rat vascular injury

Restenosis rate following vascular interventions still limits their long-term success. Oxidative stress plays a relevant role in this pathophysiological phenomenon, but less attention has been devoted to its effects on DNA damage and to the subsequent mechanisms of repair. We analysed in a model of arteriotomy-induced stenosis in rat carotids the time-dependent expression of DNA damage markers and of DNA repair genes, together with the assessment of proliferation and apoptosis indexes. The expression of the oxidative DNA damage marker 7,8-dihydro-8-oxo-2'-deoxyguanosine was increased at 3 and 7 days after arteriotomy, with immunostaining distributed in the injured vascular wall and in perivascular tissue. The expression of the DNA damage marker phospho-H2A.X was less relevant but increasing from 4 hrs to 7 days after arteriotomy, with immunostaining prevalently present in the adventitia and, to a lesser extent, in medial smooth muscle cells at the injury site. RT-PCR indicated a decrease of 8 out of 12 genes of the DNA repair machinery we selected from 4 hrs to 7 days after arteriotomy with the exception of increased Muyth and Slk genes (p<0.05). Western Blot revealed a decrease of p53 and catalase at 3 days after arteriotomy (p<0.05). A maximal 7% of BrdU-positive cells in endothelium and media occurred at 7 days after arteriotomy, while the apoptotic index peaked at 3 days after injury (p<0.05). Our results highlight a persistent DNA damage presumably related to a temporary decreased expression of the DNA repair machinery and of the antioxidant enzyme catalase, playing a role in stenosis progression.

In vivo modulation of Nogo-B attenuates neointima formation

Nogo-B was recently identified as a novel vascular marker; the normally high vascular expression of Nogo-B is rapidly lost following vascular injury. Here we assess the potential therapeutic effects of Ad-Nogo-B delivery to injured vessels in vivo. Nogo-B overexpression following Ad-Ng-B infection of vascular smooth muscle cells (VSMCs) was shown to block proliferation and migration in a dose-dependent manner in vitro. We next assessed the effects of Ad-Ng-B treatment on neointima formation in two in vivo models of acute vascular injury. Adventitial delivery of Ad-Ng-B to wire-injured murine femoral arteries led to a significant decrease in the intimal area [0.014 mm(2) versus 0.030 mm(2) (P = 0.049)] and the intima:media ratio [0.78 versus 1.67 (P = 0.038)] as compared to the effects of Ad-beta-Gal control virus at 21 days after injury. Similarly, lumenal delivery of Ad-Ng-B to porcine saphenous veins prior to carotid artery grafting significantly reduced the intimal area [2.87 mm(2) versus 7.44 mm(2) (P = 0.0007)] and the intima:media ratio [0.32 versus 0.55 (P = 0.0044)] as compared to the effects following the delivery of Ad- beta-Gal, at 28 days after grafting. Intimal VSMC proliferation was significantly reduced in both the murine and porcine disease models. Gene delivery of Nogo-B exerts a positive effect on vascular injury-induced remodeling and reduces neointimal development in two arterial and venous models of vascular injury.

Edifoligide: a transcription factor decoy to modulate smooth muscle cell proliferation in vein bypass

The era of genomics and recombinant DNA technology has ushered in an entirely new class of therapeutic agents designed to influence disease progression at a genetic level. The scope and utility of this technology is not fully realized. However, multiple trials of therapeutic agents have been completed and many more are ongoing. Here we report on edifoligide, a double-stranded oligodeoxynucleotide (ODN) that competitively inhibits the transcription factor E2F, a critical regulator of the cell cycle. Edifoligide has undergone extensive clinical testing for the treatment of intimal hyperplasia following vascular bypass procedures. In this review we address the rationale for targeting E2F in vascular disease, the pharmacology of edifoligide, and the results of preclinical and clinical studies using this novel compound.

Regulation of cell-matrix contacts and beta-catenin signaling in VSMC by integrin-linked kinase: implications for intimal thickening

Vascular smooth muscle cell (VSMC) proliferation and migration is responsible for intimal thickening that occurs in restenosis and atherosclerosis. Integrin-linked kinase (ILK) is a serine/threonine protein kinase implicated in signaling pathways involved in cell proliferation and migration. We studied the involvement of ILK in intimal thickening. ILK expression was significantly increased in two models of intimal thickening: balloon-injured rat carotid arteries and human saphenous vein organ cultures. Over-expression of a dominant negative ILK (DN-ILK) significantly reduced intimal thickening by approximately 50% in human saphenous vein organ cultures, demonstrating an important role in intimal thickening. ILK protein and activity was reduced on laminin and up-regulated on fibronectin, indicating ILK protein expression is modulated by extracellular matrix composition. Inhibition of ILK by siRNA knockdown and DN-ILK significantly decreased VSMC proliferation and migration while wild type ILK significantly increased proliferation and migration on laminin, confirming an essential role of ILK in both processes. Localization of paxillin and vinculin and protein levels of FAK and phospho-FAK indicated that inhibition of ILK reduced focal adhesion formation. Additionally, inhibition of ILK significantly attenuated the presence of the cell-cell complex proteins N-cadherin and beta-catenin, and beta-catenin signaling. We therefore suggest ILK modulates VSMC proliferation and migration at least in part by acting as a molecular scaffold in focal adhesions as well as modulating the stability of cell-cell contact proteins and beta-catenin signaling. In summary, ILK plays an important role in intimal thickening by modulating VSMC proliferation and migration via regulation of cell-matrix and cell-cell contacts and beta-catenin signaling.

p53 dominant-negative mutant R273H promotes invasion and migration of human endometrial cancer HHUA cells

Dominant negative (DN) mutations of tumor suppressor p53 (TP53) are clinically associated with cancer progression and metastasis of endometrial malignancy. To investigate the DN effect on tumor migration and invasion, we generated cells that stably co-expressed wild-type (wt) and R273H DN mutant TP53 (273H cells), and wt and R213Q recessive mutant TP53 (213Q cells), by transfection in endometrial cancer cells HHUA that expressed wt p53. R273H, but not R213Q, repressed wt p53-stimulated transcription of p21, Bax, and MDM2. 273H cells also showed markedly increased in vitro invasion and migration potentials, and displayed reduced Maspin, PAI-1, and KAI1 mRNA expressions as compared with 213Q and wt cells. The induction of wt p53 function by use of Adriamycin resulted in the inhibition of the invasion/migration capacity in association with the up-regulation of p53 target genes to a far greater degree in 213Q and wt cells than in 273H cells. R273H expression in p53-null cancer cell SK-OV-3 and Saos-2 did not significantly affect cell invasion and migration activities. Taken together, these results suggest that transdominance of R273H mutant over wt p53 rather than a gain-of-function promotes tumor metastasis by increasing invasion and migration in HHUA cells.

Cardiovascular gene therapy: current status and therapeutic potential

Gene therapy is emerging as a potential treatment option in patients suffering from a wide spectrum of cardiovascular diseases including coronary artery disease, peripheral vascular disease, vein graft failure and in-stent restenosis. Thus far preclinical studies have shown promise for a wide variety of genes, in particular the delivery of genes encoding growth factors such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) to treat ischaemic vascular disease both peripherally and in coronary artery disease. VEGF as well as other genes such as TIMPs have been used to target the development of neointimal hyperplasia to successfully prevent vein graft failure and in-stent restenosis in animal models. Subsequent phase I trials to examine safety of these therapies have been successful with low levels of serious adverse effects, and albeit in the absence of a placebo group some suggestion of efficacy. Phase 2 studies, which have incorporated a placebo group, have not confirmed this early promise of efficacy. In the next generation of clinical gene therapy trials for cardiovascular disease, many parameters will need to be adjusted in the search for an effective therapy, including the identification of a suitable vector, appropriate gene or genes and an effective vector delivery system for a specific disease target. Here we review the current status of cardiovascular gene therapy and the potential for this approach to become a viable treatment option.

DNA damage, p53, apoptosis and vascular disease

Atherosclerosis is the commonest cause of death in the Western world. The atherosclerotic plaque shows evidence of DNA damage, activation of damage repair pathways, p53 expression and apoptosis, involving a variety of different cell types. This review summarises the evidence for DNA damage in atherosclerosis, the likely stimuli inducing damage, and the increasing role of p53 in mediating apoptosis and its consequences in atherosclerosis.

Role of nuclear Ca2+/calmodulin-stimulated phosphodiesterase 1A in vascular smooth muscle cell growth and survival

In response to biological and mechanical injury, or in vitro culturing, vascular smooth muscle cells (VSMCs) undergo phenotypic modulation from a differentiated "contractile" phenotype to a dedifferentiated "synthetic" one. This results in the capacity to proliferate, migrate, and produce extracellular matrix proteins, thus contributing to neointimal formation. Cyclic nucleotide phosphodiesterases (PDEs), by hydrolyzing cAMP or cGMP, are critical in the homeostasis of cyclic nucleotides that regulate VSMC growth. Here, we demonstrate that PDE1A, a Ca2+-calmodulin-stimulated PDE preferentially hydrolyzing cGMP, is predominantly cytoplasmic in medial "contractile" VSMCs but is nuclear in neointimal "synthetic" VSMCs. Using primary VSMCs, we show that cytoplasmic and nuclear PDE1A were associated with a contractile marker (SM-calponin) and a growth marker (Ki-67), respectively. This suggests that cytoplasmic PDE1A is associated with the "contractile" phenotype, whereas nuclear PDE1A is with the "synthetic" phenotype. To determine the role of nuclear PDE1A, we examined the effects loss-of-PDE1A function on subcultured VSMC growth and survival using PDE1A RNA interference and pharmacological inhibition. Reducing PDE1A function significantly attenuated VSMC growth by decreasing proliferation via G1 arrest and inducing apoptosis. Inhibiting PDE1A also led to intracellular cGMP elevation, p27Kip1 upregulation, cyclin D1 downregulation, and p53 activation. We further demonstrated that in subcultured VSMCs redifferentiated by growth on collagen gels, cytoplasmic PDE1A regulates myosin light chain phosphorylation with little effect on apoptosis, whereas inhibiting nuclear PDE1A has the opposite effects. These suggest that nuclear PDE1A is important in VSMC growth and survival and may contribute to the neointima formation in atherosclerosis and restenosis.

Mechanisms of lumen narrowing of saphenous vein bypass grafts 12 months after implantation: an intravascular ultrasound study

BACKGROUND

Previous long-term (>1 year) studies have suggested that saphenous vein bypass grafts (SVGs) undergo vascular remodeling similar to native coronary arteries. However, early morphologic stages of SVG remodeling have not been characterized in vivo.

METHODS

Thirty SVGs were studied 12 months after implantation using an intravascular ultrasound automated pullback system. Intravascular ultrasound images were analyzed between 10 and 60 mm from the tip of the guide. Lumen area (LA), intima area (IA), and vessel area (VA, defined as the area within the outer border of a hypoechoic intimal layer) were computed at 3 cross sections: the minimum LA (MLA) site and the proximal and distal reference sites. Area changes (Delta) were calculated as the MLA site minus the average of the reference sites.

RESULTS

In this cohort, 70% of the MLA sites had a smaller VA than the average references. On average, MLA sites had significantly smaller VA (9.7 +/- 2.9 vs 10.7 +/- 3.2 mm2, P < .01) and larger IA (2.5 +/- 2.1 vs 1.2 +/- 1.3 mm2, P < .01) than at the reference sites. The relative contribution of DeltaVA (-1.0 +/- 1.4 mm2) and DeltaIA (1.3 +/- 1.3 mm2) to lumen compromise (-2.3 +/- 1.4 mm2) were 43% and 57%, respectively. On the other hand, simple linear regression analysis revealed a significant positive correlation between DeltaIA and DeltaVA (y = -1.7 + 0.52x, r = 0.50, P < .01).

CONCLUSIONS

Within the first year, the mechanism of lumen compromise in SVG is a combination of negative remodeling and intimal hyperplasia. Positive remodeling is seen in a minority of cases. However, the direction and extent of remodeling correlated with change in intimal thickness.

Opportunities for gene therapy in preventing vein graft failure after coronary artery bypass surgery

The poor patency rates for coronary artery bypass grafting (CABG) using autologous saphenous vein necessitate the need for continued research into the potential clinical utility of gene therapy. Bypass grafting is ideally suited for gene therapy, as graft can be genetically modified ex vivo prior to grafting in the coronary vasculature. Research to date has demonstrated effective blockade of late vein graft failure through overexpression of a variety of transgenes that modulate the proliferative, migratory and/or apoptotic indexes of cells in the graft wall. This has resulted in a substantial wealth of preclinical data that support advancement to clinical trials. Future translation into clinical trials will ensure that this exciting and highly relevant area of gene therapy is fully evaluated for potential routine clinical practice to improve patency rates of bypass graft procedures involving saphenous vein.

Regulation of vascular smooth muscle cell proliferation, migration and death by heparan sulfate 6-O-endosulfatase1

Migration, proliferation and death of vascular smooth muscle cells (VSMC) are important events in vascular pathology regulated by heparan sulfate proteoglycans and hence potentially by cell surface HS 6-O-endosulfatase1 (sulf1). Sulf1 mRNA expression was increased in cultured VSMC compared to rat aorta. Furthermore, adenovirus mediated overexpression of quail sulf1 decreased adhesion, and increased proliferation and apoptosis of VSMC. Overexpression of a dominant negative variant also decreased adhesion of VSMC and increased proliferation, apoptosis, migration and chemotaxis of VSMC. Our results imply that only normal levels of 6-O-sulfation maintained by sulf1 are optimal for several functions of VSMC.

Protein kinase C delta induces apoptosis of vascular smooth muscle cells through induction of the tumor suppressor p53 by both p38-dependent and p38-independent mechanisms

Apoptotic death of vascular smooth muscle cells (SMCs) is a prominent feature of blood vessel remodeling. In the present study, we examined the novel PKC isoform protein kinase C delta (PKCdelta) and its role in vascular SMC apoptosis. In A10 SMCs, overexpression of PKCdelta was sufficient to induce apoptosis, whereas inhibition of PKCdelta diminished H2O2-induced apoptosis. Moreover, evidence is provided that the tumor suppressor p53 is an essential mediator of PKCdelta-induced apoptosis in SMCs. Activation of PKCdelta led to accumulation as well as phosphorylation of p53 in SMCs; this induction correlated with apoptosis. Furthermore, blocking p53 induction with small interference RNA or targeted gene deletion prevented PKCdelta-induced apoptosis, whereas restoring p53 expression rescued the ability of PKCdelta to induce apoptosis in p53 null SMCs. We also establish that PKCdelta regulates p53 at both transcriptional and post-translational levels. Specifically, the transcriptional regulation required p38 MAPK, whereas the post-translational modification, at least for serine 46, did not involve MAPK. Additionally, PKCdelta, p38 MAPK, and p53 co-associate in cells under conditions favoring apoptosis. Together, our data suggest that SMC apoptosis proceeds through a pathway that involves PKCdelta, the intermediary p38 MAPK, and the downstream target tumor suppressor p53.

Smoking-gene interaction and disease development: relevance to pancreatic cancer and atherosclerosis

There is little doubt that cigarette smoking remains a major environmental health risk that humans are facing in the twenty-first century. Cigarette smokers are more likely to develop many forms of diseases than nonsmokers, including cancers and vascular diseases. With the availability of the human genome sequence, we become more aware of the genetic contributions to these common diseases, especially the interactive relations between environmental factors (e.g., smoking) and genes on disease susceptibility, development, and prognosis. Although smoking is responsible for up to 30% of pancreatic cancers and about 10% of cases are ascribed to genetic reasons, some genetic variants do not predispose carriers to disease development unless they are exposed to a specific adverse environment such as smoking. This smoke-gene interaction could potentially be responsible for most of the cases. Certain polymorphisms in genes such as CYP1A1 have been shown particularly sensitive to smoking-induced pathogenesis, including pancreatic cancer and atherosclerosis. We found that individuals with CYP1A1 CC genotype had a more than three fold increase in risk for severe coronary atherosclerosis when they smoked. Patients with endothelial nitric oxide synthase (eNOS) intron 4 27 repeat homozygotes were more likely to develop severe coronary stenosis when they smoked. On the other hand, DNA variants at the eNOS gene also dictate how smoking affects the expression of eNOS. We showed that GSTM1 deficiency was not involved in smoking-induced vascular diseases, but p53 polymorphisms tended to modify the disease severity in smokers. We are still at an early stage of defining the pairs and mechanisms of smoke-gene interaction, and this etiologic mechanism may hold great potential for risk assessment, treatment strategy, and prognostic predictions.

N-Cadherin–Dependent Cell–Cell Contacts Promote Human Saphenous Vein Smooth Muscle Cell Survival

OBJECTIVE

Vascular smooth muscle cell (VSMC) apoptosis is thought to contribute to atherosclerotic plaque instability. Cadherin mediates calcium-dependent homophilic cell-cell contact. We studied the role of N-cadherin in VSMC apoptosis.

METHODS AND RESULTS

Human saphenous vein VSMCs were grown in agarose-coated wells to allow cadherin-mediated aggregate formation. Cell death and apoptosis were determined after disruption of cadherins using several approaches (n> or =3 per approach). Calcium removal from culture medium or addition of nonspecific cadherin antagonist peptides significantly decreased aggregate formation and increased cell death by apoptosis (34+/-6% versus 75+/-1% and 19+/-1% versus 40+/-5%, respectively; P<0.05). Specific inhibition of N-cadherin using antagonists and neutralizing antibodies similarly increased apoptosis. Supporting this, overexpression of full-length N-cadherin significantly reduced VSMC apoptosis from 44+/-10% to 20+/-3% (P<0.05), whereas abolishing N-cadherin expression by overexpression of a dominant-negative N-cadherin significantly, even in the presence of cell-matrix contacts, increased apoptosis from 9+/-2% to 50+/-1% (P<0.05). Interestingly, cell-cell contacts provided a similar degree of protection from apoptosis to cell-matrix contacts. Finally, N-cadherin-mediated cell-cell contacts initiated anti-apoptotic signaling by increasing Akt and Bad phosphorylation.

CONCLUSIONS

Our results indicate that VSMC survival is dependent on N-cadherin-mediated cell-cell contacts, which could be important in the context of plaque instability.

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.

Aging exacerbates neointimal formation, and increases proliferation and reduces susceptibility to apoptosis of vascular smooth muscle cells in mice

OBJECTIVES

In response to injury, aging mediates exaggerated neointimal formation, the pathologic hallmark of obliterative vascular diseases. We assessed the development of neointima in a model of mechanical vascular injury in aging mice (18 months old) and young mice (2 months old). To investigate the mechanisms by which aging affects neointimal formation, we also carried out a set of in vitro studies to characterize the biologic properties of vascular smooth muscle cells (VSMCs) derived from aging and young mice.

METHODS

Aging and young mice were subjected to wire injury to the carotid artery. Four weeks later injured arteries were harvested, and neointimal formation was histologically assessed. The profiles of angiogenesis-related genes between aortic VSMCs derived from aging and young mice were compared with complementary DNA arrays. Expression of platelet-derived growth factor receptor-alpha (PDGFR-alpha) and proliferation in response to platelet-derived growth factor-BB (PDGF-BB) by VSMCs were assessed. Susceptibility to apoptosis in aging and young VSMCs in response to nitric oxide and serum starvation was investigated. In addition, the level of apoptosis in neointimal VSMCs (by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay) was compared between aging and young animals.

RESULTS

When compared with young mice, aging mice exhibited exaggerated neointimal formation (intima-media ratio, 1.17 +/- 0.57 vs 0.49 +/- 0.16; P < .0001). Aging VSMCs expressed higher levels of PDGFR-alpha (12.0% +/- 2.7% vs 3.2 +/- 0.67%; P = .034) and greater proliferative response (4-fold increase) to PDGF-BB, compared with young VSMCs. However, aging VSMCs were less susceptible to apoptosis when subjected to serum starvation (75% less) and exposure to nitric oxide (50% less). Furthermore, there was more apoptosis in the neointima of young arteries than in their aging counterparts (8.75% +/- 3.3% vs 2.8% +/- 1.9; P = .021).

CONCLUSIONS

Age-dependent increases in PDGFR-alpha may alter VSMC proliferation, and when coupled with resistance to apoptosis could contribute to exaggerated neointima formation in aging animals. Of significance, our findings in the mouse will enable application of abundant molecular tools afforded by this species to further dissect the mechanisms of exaggerated neointimal formation associated with aging.

CLINICAL RELEVANCE

Neointimal formation is the pathologic hallmark of obliterative vascular diseases, including primary atherosclerosis, post stent restenosis, graft occlusion after vascular bypass procedures, and transplant allograft vasculopathy. Aging is an independent risk factor for development of cardiovascular diseases, and aging exaggerates neointimal formation after vascular injury. Understanding the mechanisms responsible for this phenomenon may facilitate prevention or provide new therapies for vascular occlusive diseases, which are so prevalent in the aging population. Our ability to reproduce the model in the mouse will no doubt facilitate such understanding.

Endogenous p53 protects vascular smooth muscle cells from apoptosis and reduces atherosclerosis in ApoE knockout mice

Recent studies have indicated that the tumor suppressor gene p53 limits atherosclerosis in animal models; p53 expression is also increased in advanced human plaques compared with normal vessels, where it may induce growth arrest and apoptosis. However, controversy exists as to the role of endogenous levels of p53 in different cell types that comprise plaques. We examined atherosclerotic plaque development and composition in brachiocephalic arteries and aortas of p53-/-/ApoE-/- mice versus wild type p53 controls. p53-/- mice demonstrated increased aortic plaque formation, with increased rates of cell proliferation and reduced rates of apoptosis in brachiocephalic arteries. Although most proliferating cells were monocyte/macrophages, apoptotic cells were both vascular smooth muscle cells (VSMCs) and macrophages. Transplant of p53 bone marrow to p53-/-/ApoE-/- mice reduced aortic plaque formation and cell proliferation in brachiocephalic plaques, but also markedly reduced apoptosis. To examine p53 regulation of these processes, we studied proliferation and apoptosis in macrophages, bone marrow stromal cells and VSMCs cultured from these mice. Although endogenous p53 promoted apoptosis in macrophages, it protected VSMCs and stromal cells from death, a hitherto unknown function in these cells, in part by inhibiting DNA damage response enzymes. p53 also inhibited stromal cell expression of VSMC markers. We conclude that endogenous levels of p53 protect VSMCs and stromal cells against apoptosis, while promoting apoptosis in macrophages, and protect against atherosclerosis development.

Intramuscular gene transfer of CGRP inhibits neointimal hyperplasia after balloon injury in the rat abdominal aorta

CGRP is a well-known neuropeptide that has various protective effects on cardiovascular system. Our previous studies have shown that CGRP inhibits vascular smooth muscle cell (VSMC) proliferation in vitro. The present study aimed to explore the role of the CGRP in neointimal formation after balloon injury in the rat aortic wall and the underlying mechanism. Gene transfer of CGRP was performed with the use of intramuscular electroporation in a balloon-injured rat aorta model. Apoptosis in VSMCs was determined by electrophoresis assessment of DNA fragmentation and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay. Overexpression of the CGRP gene significantly inhibited the neointimal formation after balloon injury compared with the mock transfer, as assessed by the intima-to-media ratio 14 days after balloon injury (29.2 +/- 3.7% vs. 52.7 +/- 5.4%; n = 9-12, P < 0.05). In addition, CGRP gene expression increased the number of apoptotic cells in the neointima in vivo 14 days after balloon injury. Similarly, the addition of bioactive CGRP and the nitric oxide donor induced similar apoptosis in cultured VSMCs. The antagonist of the CGRP(1) receptor and inhibitors of cAMP-PKA and nitric oxide blocked CGRP-mediated apoptosis. Furthermore, CGRP gene transfer increased inducible nitric oxide synthase and p53 but decreased PCNA and Bcl-2 protein levels in balloon-injured rat aorta. Our data demonstrated that CGRP potently inhibited neointimal thickening in the rat aorta, at least in part through its distinct effects on apoptosis and proliferation of VSMCs both in vivo and in vitro. Therefore, delivery of the CGRP gene may have therapeutic implications in limiting vascular restenosis.

The calcium channel blocker amlodipine exerts its anti¬proliferative action via p21 (Waf1/Cip1) gene activation

Proliferation of vascular smooth muscle cells (VSMC) contributes to the progression of atherosclerotic plaques. Calcium channel blockers have been shown to reduce VSMC proliferation, but the underlying molecular mechanism remains unclear. p21(Waf1/Cip1) is a potent inhibitor of cell cycle progression. Here, we demonstrate that amlodipine (10(-6) to 10(-8) M) activates de novo synthesis of p21(Waf1/Cip1) in vitro. We show that amlodipine-dependent activation of p21(Waf1/Cip1) involves the action of the glucocorticoid receptor (GR) and C/EBP-alpha. The underlying pathway apparently involves the action of mitogen-activated protein kinase or protein kinase C, but not of extracellular signal-related kinase or changes of intracellular calcium. Amlodipine-induced p21(Waf1/Cip1) promoter activity and expression were abrogated by C/EBP-alpha antisense oligonucleotide or by the GR antagonist RU486. Amlodipine-dependent inhibition of cell proliferation was partially reversed by RU486 at 10(-8) M (58%+/-29%), antisense oligonucleotides targeting C/EBP-alpha (91%+/-26%), or antisense mRNAs targeting p21(Waf1/Cip1) (96%+/-32%, n=6); scrambled antisense oligonucleotides or those directed against C/EBP-beta were ineffective. The data suggest that the anti-proliferative action of amlodipine is achieved by induction of the p21 (Waf1/Cip1) gene, which may explain beneficial covert effects of this widely used cardiovascular therapeutic drug beyond a more limited role as a vascular relaxant.