Connective tissue disease type mediates branch patency of grafts in open thoracoabdominal aortic reconstruction.

OBJECTIVE: Despite a shared degenerative vascular phenotype, Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and other genetically distinct connective tissue diseases (CTDs) have unique extravascular pathologies that impact the outcomes of aortic replacement. The aim of our study was to investigate the association of CTD genotype with postoperative outcomes and branch patency following open thoracoabdominal aortic replacement in a large institutional cohort. METHODS: All patients undergoing open branched thoracoabdominal aortic replacement at a single academic center from 2006 to 2020 were included and classified as CTD or non-CTD based on the presence of genotypic documentation. Outcomes were compared using analysis of variance and χ2 testing for continuous and discrete variables, respectively. Kaplan-Meier curves were utilized to examine patency of graft branches over time. RESULTS: Overall, 172 patients were included, with a mean follow-up of 30.5 ± 34.9 months. CTD was present in 45 patients (26%); specifically, 32 had MFS, five had LDS, and eight had another CTD. Patients with CTDs had more extent II thoracoabdominal aneurysms (40% vs 15%), more reconstructed branches (3.5 vs 1.8), more frequently reconstructed visceral branches (86.7% vs 22.7%), and higher intraoperative blood loss (13.3 vs 6.8 L; all P < .05) compared with non-CTD patients. Patients with MFS were more frequently systemically anticoagulated preoperatively (50% vs 5%) and demonstrated higher rates of postoperative deep vein thrombosis/pulmonary embolism compared with non-CTD patients (9% vs 2%; both P < .05). Five-year renal branch patency was decreased among all patients compared with visceral branches (87.3% vs 95.6%; P = .05), but there were no individual branch patency differences between patients with and without CTDs (P = .086). Overall branch patency at 1 and 5 years was significantly higher in patients with MFS than in non-CTD patients (98.9% vs 89.1% at 5 years); there were no significant patency differences between non-CTD patients and any other CTD subgroup, mostly due to early patency loss. CONCLUSIONS: Open thoracoabdominal reconstruction in patients with CTD is technically challenging and associated with increased transfusion and postoperative thromboembolic events when compared with non-CTD patients. Technical outcomes of the procedure are excellent and are differentially associated with genotype, with patients with MFS experiencing significantly improved branch patency over both non-CTD patients and patients with other CTDs, a finding which has multifactorial drivers.

The association of genotype polymorphisms with vascular access patency in hemodialysis patients.

Some hemodialysis patients suffer from repeat dysfunction of dialysis vascular access and need procedures of angioplasty, thrombectomy, and even temporary catheter use. Why these patients are vulnerable to vascular access dysfunction and how to improve its patency are imperative to be discovered. Traditional risk factors for vascular access function had been widely investigated but could not fully explain this question. Several genotype polymorphisms were demonstrated to increase the incidence of cardiovascular disease and might also be linked to higher risk of vascular access dysfunction. As the major causes of arteriovenous access thrombosis are hypercoagulable status and arteriovenous access stenosis, the investigated genes mainly focus on the mediators of the coagulation cascade, inflammatory process, and endothelial dysfunction. The reported polymorphisms of genes significantly associated with arteriovenous access dysfunction included genes encoding methylene tetrahydrofolate reductase, coagulation factors, heme oxygenase-1, matrix metalloproteinase, transforming growth factor-ß1, tumor necrosis factor-α, vascular endothelial growth factor-A, renin-angiotensin-aldosterone system, and protein methyl transferase. However, further prospective study is indispensable to elucidate the association between the genotype polymorphisms and the outcome of vascular access. More and more therapeutic options that focus on genotype polymorphisms may generate a great benefit to the patency of vascular access of uremic patients.

Scavenger receptor class A member 5 (SCARA5) and suprabasin (SBSN) are hub genes of coexpression network modules associated with peripheral vein graft patency.

OBJECTIVE: Approximately 30% of autogenous vein grafts develop luminal narrowing and fail because of intimal hyperplasia or negative remodeling. We previously found that vein graft cells from patients who later develop stenosis proliferate more in vitro in response to growth factors than cells from patients who maintain patent grafts. To discover novel determinants of vein graft outcome, we have analyzed gene expression profiles of these cells using a systems biology approach to cluster the genes into modules by their coexpression patterns and to correlate the results with growth data from our prior study and with new studies of migration and matrix remodeling. METHODS: RNA from 4-hour serum- or platelet-derived growth factor (PDGF)-BB-stimulated human saphenous vein cells obtained from the outer vein wall (20 cell lines) was used for microarray analysis of gene expression, followed by weighted gene coexpression network analysis. Cell migration in microchemotaxis chambers in response to PDGF-BB and cell-mediated collagen gel contraction in response to serum were also determined. Gene function was determined using short-interfering RNA to inhibit gene expression before subjecting cells to growth or collagen gel contraction assays. These cells were derived from samples of the vein grafts obtained at surgery, and the long-term fate of these bypass grafts was known. RESULTS: Neither migration nor cell-mediated collagen gel contraction showed a correlation with graft outcome. Although 1188 and 1340 genes were differentially expressed in response to treatment with serum and PDGF, respectively, no single gene was differentially expressed in cells isolated from patients whose grafts stenosed compared with those that remained patent. Network analysis revealed four unique groups of genes, which we term modules, associated with PDGF responses, and 20 unique modules associated with serum responses. The "yellow" and "skyblue" modules, from PDGF and serum analyses, respectively, correlated with later graft stenosis (P = .005 and P = .02, respectively). In response to PDGF, yellow was also associated with increased cell growth. For serum, skyblue was also associated with inhibition of collagen gel contraction. The hub genes for yellow and skyblue (ie, the gene most connected to other genes in the module), scavenger receptor class A member 5 (SCARA5) and suprabasin (SBSN), respectively, were tested for effects on proliferation and collagen contraction. Knockdown of SCARA5 increased proliferation by 29.9% ± 7.8% (P < .01), whereas knockdown of SBSN had no effect. Knockdown of SBSN increased collagen gel contraction by 24.2% ± 8.6% (P < .05), whereas knockdown of SCARA5 had no effect. CONCLUSIONS: Using weighted gene coexpression network analysis of cultured vein graft cell gene expression, we have discovered two small gene modules, which comprise 42 genes, that are associated with vein graft failure. Further experiments are needed to delineate the venous cells that express these genes in vivo and the roles these genes play in vein graft healing, starting with the module hub genes SCARA5 and SBSN, which have been shown to have modest effects on cell proliferation or collagen gel contraction.

Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone.

Failure of the ductus arteriosus (DA) to close at birth can lead to serious complications. Conversely, certain profound congenital cardiac malformations require the DA to be patent until corrective surgery can be performed. In each instance, clinicians have a very limited repertoire of therapeutic options at their disposal - indomethacin or ibuprofen to close a patent DA (PDA) and prostaglandin E1 to maintain patency of the DA. Neither treatment is specific to the DA and both may have deleterious off-target effects. Therefore, more therapeutic options specifically targeted to the DA should be considered. We hypothesized the DA possesses a unique genetic signature that would set it apart from other vessels. A microarray was used to compare the genetic profiles of the murine DA and ascending aorta (AO). Over 4,000 genes were differentially expressed between these vessels including a subset of ion channel-related genes. Specifically, the alpha and beta subunits of large-conductance calcium-activated potassium (BKCa) channels are enriched in the DA. Gain- and loss-of-function studies showed inhibition of BKCa channels caused the DA to constrict, while activation caused DA relaxation even in the presence of O2. This study identifies subsets of genes that are enriched in the DA that may be used to develop DA-specific drugs. Ion channels that regulate DA tone, including BKCa channels, are promising targets. Specifically, BKCa channel agonists like NS1619 maintain DA patency even in the presence of O2 and may be clinically useful.

Clinical, biochemical, and genetic predictors of coronary artery bypass graft failure.

OBJECTIVES: To identify novel predictors for coronary artery bypass grafting failure, we probed for associations with known clinical and biochemical risk factors for atherosclerosis. We also used microarray analysis to identify novel single nucleotide polymorphisms to better understand the genetics and pathogenesis of graft occlusion. METHODS: The present study was a nested case-control substudy of the Radial Artery Patency Study 5-year follow-up data. From 1996 to 2001, 87 patients underwent coronary artery bypass grafting. Of these, 26 patients (29.9%) had an occluded study graft (saphenous vein or radial artery) at 8.0 ± 1.1 years. The clinical parameters, late angiography, blood biomarker levels, and surgical outcomes data were included in a multivariate analysis to determine the independent predictors of graft failure. RESULTS: The risk factors of graft failure were fibrinogen (odds ratio [OR], 3.94; 95% confidence interval [CI], 1.33-11.63; P = .01), creatinine (OR, 1.06; 95% CI, 1.02-1.10; P = .006), and diabetes mellitus (OR, 5.15; 95% CI, 1.08-24.59; P = .04). High-density lipoprotein (OR, 0.74; 95% CI, 0.53-1.02; P = .06) was weakly protective; however, low-density lipoprotein and total cholesterol were not predictors. We then identified the association of several human single nucleotide polymorphisms with graft failure, including mutations in glutathione-S-transferase α3. Human coronary arteries and bypass grafts demonstrated increased protein expression of glutathione-S-transferase α3, a known cardioprotective factor, in the atherosclerotic regions and surrounding adventitial tissues. CONCLUSIONS: We identified diabetes as a potential clinical predictor and plasma fibrinogen, creatinine, and high-density lipoprotein as potential novel biomarkers. These might help risk stratify patients for the development of graft failure. We also demonstrated a novel association between glutathione-S-transferase α3 and graft failure.

A single nucleotide polymorphism in the p27(Kip1) gene is associated with primary patency of lower extremity vein bypass grafts.

OBJECTIVE: Factors responsible for the variability in outcomes after lower extremity vein bypass grafting (LEVBG) are poorly understood. Recent evidence has suggested that a single nucleotide polymorphism (SNP) in the promoter region of the p27(Kip1) gene, a cell-cycle regulator, is associated with coronary in-stent restenosis. We hypothesized an association with vein graft patency. METHODS: This was a retrospective genetic association study nested within a prospective cohort of 204 patients from three referral centers undergoing LEVBG for claudication or critical ischemia. The main outcome measure was primary vein graft patency. RESULTS: All patients were followed up for a minimum of 1 year with duplex graft surveillance (median follow-up, 893 days; interquartile range, 539-1315). Genomic DNA was isolated and SNP analysis for the p27(Kip1)-838C>A variants was performed. Allele frequencies were correlated with graft outcome using survival analysis and Cox proportional hazards modeling. The p27(Kip1)-838C>A allele frequencies observed were CA, 53%; CC, 30%; and AA, 17%, satisfying Hardy-Weinberg equilibrium. Race (P = .025) and history of coronary artery disease (P = .027) were different across the genotypes; all other baseline variables were similar. Primary graft patency was greater among patients with the -838AA genotype (75% AA vs 55% CA/CC at 3 years; P = .029). In a Cox proportional hazards model including age, sex, race, diabetes, critical limb ischemia, redo (vs primary) bypass, vein type, and baseline C-reactive protein level, the p27(Kip1)-838AA genotype was significantly associated with higher graft patency (hazard ratio for failure, 0.4; 95% confidence interval, 0.17-0.93). Genotype was also associated with early (0-1 month) changes in graft lumen diameter by ultrasound imaging. CONCLUSIONS: These data suggest that the p27(Kip1)-838C>A SNP is associated with LEVBG patency and, together with previous reports, underscore a central role for p27(Kip1) in the generic response to vascular injury.

Interleukin-6 -634 C/G and -174 G/C polymorphisms in Korean patients undergoing hemodialysis.

BACKGROUND/AIMS: Chronic inflammatory status is a possible risk factor for vascular access dysfunction in hemodialysis (HD) patients, but susceptibility differences appear among individuals. Interleukin (IL)-6 is a well-known inflammatory cytokine with various polymorphisms. We examined whether IL-6 polymorphisms are associated with vascular access dysfunction in HD patients. METHODS: A total of 80 HD patients (including 42 diabetic patients) were enrolled. Polymorphisms in the IL-6 gene promoter (-634 C/G and -174 G/C) were studied using restriction length polymorphism polymerase chain reaction analysis. Vascular access patency was compared between the patient groups with respect to IL-6 polymorphisms. An additional 89 healthy individuals were enrolled in the control group. Plasma IL-6 levels were determined by enzyme-linked immunosorbent assay. RESULTS: The GG genotype and G allele at position -634 in the IL-6 promoter were more frequently observed in HD patients than in controls. Furthermore, the distribution of the -634 polymorphism differed according to vascular access patency in non-diabetic HD patients. However, the G allele was not a significant risk factor for early access failure. No significant association appeared between the IL-6 -634 C/G polymorphism and plasma IL-6 levels. The C allele of the IL-6 -174 G/C polymorphism was not detected in our study population. CONCLUSIONS: The IL-6 -634 G allele appears with greater frequently in patients with end-stage renal disease and may be associated with vascular access dysfunction in non-diabetic HD patients.

Expression and function of endothelial nitric oxide synthase messenger RNA and protein are higher in internal mammary than in radial arteries.

BACKGROUND: The internal mammary artery (IMA) has a better long-term patency rate than the radial artery (RA), but the underlying molecular mechanisms are unclear. We compared endothelial nitric oxide synthase (eNOS) and related NO release in these two arteries. METHODS: Real-time polymerase chain reaction was used to quantify eNOS messenger RNA (mRNA) expression level in the endothelial cells of IMAs and RAs. eNOS protein localization was determined by immunohistochemistry. NO release from the endothelium of IMAs and RAs was directly measured by an electrochemical method using a membrane-type NO-sensitive electrode. RESULTS: Endothelial nitric oxide synthase mRNA expression level was significantly higher in the endothelial cells of IMAs than in RAs (1.03±0.19 vs 0.53±0.09, n=7, p<0.05), but was similar in the whole vascular tissue. eNOS protein immunoreactivity was higher in the endothelial cells of IMAs than in RAs. NO release at both levels in IMAs was significantly greater than in RAs (basal: 17.5±1.9 vs 10.2±0.7 nM, n=11 each, p=0.003; stimulated with bradykinin -7 log M: 31.5±3.6 vs 14.3±5.3 nM, n=6 each, p=0.02). CONCLUSIONS: Endothelial cells in the IMA express higher levels of eNOS mRNA and protein than those in the RA, which is linked with higher release of NO. These findings may be related to the superior long-term patency rate of the IMA vs the RA. This study also provides some basic genetic information for grafting arteries.

Genetic ablation of IRAK4 kinase activity inhibits vascular lesion formation.

Inflammation is critically involved in atherogenesis. Signaling from innate immunity receptors TLR2 and 4, IL-1 and IL-18 is mediated by MyD88 and further by interleukin-1 receptor activated kinases (IRAK) 4 and 1. We hypothesized that IRAK4 kinase activity is critical for development of atherosclerosis. IRAK4 kinase-inactive knock-in mouse was crossed with the ApoE-/- mouse. Lesion development was stimulated by carotid ligation. IRAK4 functional deficiency was associated with down-regulation of several pro-inflammatory genes, inhibition of macrophage infiltration, smooth muscle cell and lipid accumulation in vascular lesions. Reduction of plaque size and inhibition of outward remodeling were also observed. Similar effects were observed when ApoE-/- mice subjected to carotid ligation were treated with recombinant IL-1 receptor antagonist thereby validating the model in the relevant pathway context. Thus, IRAK4 functional deficiency inhibits vascular lesion formation in ApoE-/- mice, which further unravels mechanisms of vascular inflammation and identifies IRAK4 as a potential therapeutic target.

Relation of polymorphisms in five genes to long-term aortocoronary saphenous vein graft patency.

Saphenous veins grafts (SVGs) continue to be used as conduits for coronary bypass surgery in nearly 350,000 patients annually in the United States. A possible genetic contribution to SVG longevity has not been well studied. We analyzed 168 single nucleotide polymorphisms from 150 candidate genes in 155 patients (2.1 SVGs/patient) followed for 10 +/- 4 years who underwent coronary angiography for clinical indications. Age at coronary bypass was 54 +/- 8 years, 61% were men, and 39% had diabetes mellitus. At the time of study entry, 76% were on statins. SVG patency (<70% diameter stenosis, no intervention), the primary study end point, was 60% at 5 years and 19% at 10 years. After adjustment for other factors associated with SVG patency (male gender, p = 0.007; low low-density lipoprotein, p = 0.016), 7 polymorphisms in 5 genes were associated with SVG patency (p <0.01). In conclusion, these data represent an initial step toward the use of a personalized genetic approach to coronary revascularization.

Shear stress contributes to t-PA mRNA expression in human endothelial progenitor cells and nonthrombogenic potential of small diameter artificial vessels.

Seeding endothelial progenitor cells (EPCs) onto the surface of vascular grafts has been proved to be a promising strategy to improve nonthrombogenic potentials of small diameter artificial vessels. Here, we investigated whether in vitro shear stress modulates the tissue-type plasminogen activator (t-PA) secretion and mRNA expression in human EPCs and improves patency of the EPC-seeded polyurethane small diameter vascular grafts implanted in the canine carotid artery in vivo. In vitro shear stress, in a dose-dependent manner, increased t-PA secretion and mRNA expression of human EPCs. The in vivo implantation of EPC-seeded vascular grafts remained highly patent in shear stress pretreatment compared with stationary condition. The present findings demonstrate for the first time that in vitro shear stress can enhance t-PA secretion and gene expression in human EPCs, which contributes to improvement in nonthrombogenic potentials of EPC-seeded small diameter artificial vessels with maintenance of in vivo highly patency rate.

Polymorphism in glutamate-cysteine ligase modifier subunit gene is associated with impairment of nitric oxide-mediated coronary vasomotor function.

BACKGROUND: The minor -588T allele of polymorphism -588C/T of a modifier subunit gene in glutamate-cysteine ligase (GCLM), a rate-limiting enzyme for glutathione (GSH) synthesis, was associated with lower plasma GSH levels and was a risk factor for myocardial infarction. METHODS AND RESULTS: We examined effects of the -588C/T polymorphism on coronary arterial diameter and blood flow responses to intracoronary infusion of acetylcholine in 157 consecutive subjects who had normal coronary angiograms. In multivariate linear regression analysis with covariates including traditional risk factors, the minor -588T allele had an independent association with impaired dilation or enhanced constriction of epicardial coronary arteries in response to acetylcholine, and it was independently associated with blunted increase in coronary flow response to acetylcholine. In a subgroup of 59 consecutive subjects, constrictor responses of epicardial coronary diameter to intracoronary infusion of NG-monomethyl-l-arginine, reflecting the presence of coronary nitric oxide (NO) bioactivity, had an inverse and independent association with the -588T allele in multivariate analysis. CONCLUSIONS: The -588T polymorphism of the GCLM gene causes a decrease in endothelial NO bioactivity, leading to impairment of endothelium-dependent vasomotor function in large and resistance coronary arteries. The GCL-GSH-NO axis may play a role in the defense system against coronary artery disease.

Can screening for genetic markers improve peripheral artery bypass patency?

OBJECTIVE: Three genetic mutations have been associated with an increased risk of thromboembolic events: factor V Leiden R506Q, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T (MTHFR) mutations. The aim of this study was to determine the effect of these mutations on patency of peripheral bypass procedures and preoperative and postoperative thromboembolic events. METHODS: Two hundred forty-four randomly selected volunteers participating in the Veterans Affairs Cooperative Study #362 were tested for factor V Leiden, prothrombin, or MTHFR mutations with polymerase chain reaction. Patients enrolled in the study were randomized to receive aspirin therapy or aspirin and warfarin therapy after a peripheral bypass procedure. The frequencies of preoperative and postoperative thromboembolic events and primary patency (PP), assisted primary patency (APP), and secondary patency (SP) rates were compared among carriers of the various mutations. RESULTS: Fourteen patients (5.7%) were heterozygous for the factor V Leiden mutation, seven (2.9%) were heterozygous for the prothrombin mutation, and 108 (44.6%) were heterozygous and 15 (6.2%) homozygous for the MTHFR mutation. After surgery, patients homozygous for the MTHFR gene mutation had increased graft thrombosis, compared with patients who were heterozygous (33.3% versus 11.1%; P =.01), and lower PP, APP and SP rates (P <.05). Furthermore, patients heterozygous for the MTHFR mutation had fewer graft thromboses (11.1% versus 24.4%; P =.01), fewer below-knee amputations (0.9% versus 7.6%; P =.02), and higher PP, APP, and SP rates (PP, 79.6%; APP, 88.9%; SP, 90.7%; P <.05) compared with wild-type control subjects (PP, 63%; APP, 75.6%; SP, 76.5%; P <.05). CONCLUSION: Patients with either factor V Leiden or prothrombin mutations were not at an increased risk for postoperative graft occlusion or thromboembolic events. Patients heterozygous for MTHFR mutation had a lower risk of graft thrombosis and higher graft patency rates compared with both homozygous and wild-type control subjects. Patients homozygous for the MTHFR mutation had lower graft patency rates compared with patients who were heterozygous, and a trend was seen toward lower patency rates compared with wild-type control subjects. Therefore, screening for the MTHFR gene mutation before surgery may identify patients at an increased risk of graft thrombosis.

Structure of cerebral arterioles in cystathionine beta-synthase-deficient mice.

We examined effects of hyperhomocysteinemia on structure and mechanics of cerebral arterioles. We measured plasma total homocysteine (tHcy) and pressure, diameter, and cross-sectional area of the vessel wall in maximally dilated cerebral arterioles in heterozygous cystathionine beta-synthase-deficient (CBS(+/-)) mice and wild-type (CBS(+/+)) littermates that were provided with drinking water that was unsupplemented (control diet) or supplemented with 0.5% L-methionine (high-methionine diet). Plasma tHcy was 5.0+/-1.1 micro mol/L in CBS(+/+) mice and 8.3+/-0.9 micro mol/L in CBS(+/-) mice (P<0.05 versus CBS(+/+) mice) fed the control diet. Plasma tHcy was 17.2+/-4.6 micro mol/L in CBS(+/+) mice and 21.2+/-3.9 micro mol/L in CBS(+/-) mice (P<0.05) fed the high-methionine diet. Cross-sectional area of the vessel wall was significantly increased in CBS(+/-) (437+/-22 micro m(2)) mice fed control diet and CBS(+/+) (442+/-36 micro m(2)) and CBS(+/-) (471+/-46 micro m(2)) mice fed high-methionine diet relative to CBS(+/+) (324+/-18 micro m(2)) mice fed control diet (P<0.05). During maximal dilatation, the stress-strain curves in cerebral arterioles of CBS(+/-) mice on control diet and CBS(+/+) and CBS(+/-) mice on high-methionine diet were shifted to the right of the curve in cerebral arterioles of CBS(+/+) mice on control diet, an indication that distensibility of cerebral arterioles was increased in mice with elevated levels of plasma tHcy. Thus, hyperhomocysteinemia in mice was associated with hypertrophy and an increase in distensibility of cerebral arterioles. These findings suggest that hyperhomocysteinemia promotes cerebral vascular hypertrophy and altered cerebral vascular mechanics, both of which may contribute to the increased incidence of stroke associated with hyperhomocysteinemia.

Different mechanisms of increased luminal stenosis after arterial injury in mice deficient for urokinase- or tissue-type plasminogen activator.

BACKGROUND: Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are thought to play critical roles in vascular remodeling after injury, with tPA mediating intravascular clot lysis and uPA modulating cell migration within the vessel wall. In human vascular disease, however, thrombus organization and neointimal formation are closely interrelated processes. This study examines the differential roles of tPA and uPA in these processes in mice. METHODS AND RESULTS: Carotid artery injury and thrombosis were induced in wild-type (WT), uPA-deficient (uPA(-/-)), and tPA-deficient (tPA(-/-)) mice with the use of ferric chloride. The expression of uPA and tPA was significantly upregulated in the vessel wall of WT mice 1 week after injury, and compared with WT mice, uPA(-/-) and tPA(-/-) mice had lower carotid patency rates after injury. At 3 weeks, only 55% of uPA(-/-) mouse vessels were patent compared with 81% in tPA(-/-) mice and 100% in WT mice (P=0.014). Morphometric analysis of injured arterial segments revealed severe luminal stenosis (62+/-28%) in uPA(-/-) mice compared with their tPA(-/-) (16+/-12%) and WT (6.3+/-3.6%, P<0.001) counterparts. Moreover, although the vascular walls of WT mice and, particularly, tPA(-/-) mice developed a cell-rich multilayered neointima and media, the lumen of uPA(-/-) vessels remained obstructed with acellular unorganized thrombotic material, and their medial areas did not expand. CONCLUSIONS: These results indicate that the roles of uPA and tPA in the arterial response to injury are different and more complex than previously assumed and emphasize the critical role of thrombus organization and resolution in neointimal formation and vascular pathology.

Attenuation of cerebral vasospasm after subarachnoid hemorrhage in mice overexpressing extracellular superoxide dismutase.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage (SAH) increases production of vascular extracellular superoxide anion (*O2-). We examined whether overexpression of murine extracellular superoxide dismutase (EC-SOD) alters SAH-induced cerebral vasospasm, oxidative stress, and neurological outcome. METHODS: Mice exhibiting a 2-fold increase in vascular EC-SOD and wild-type (WT) littermates were subjected to sham surgery or SAH by perforation of the right anterior cerebral artery. Neurological deficits were scored 72 hours later. Middle cerebral artery (MCA) diameter was measured or immunohistochemically stained for nitrotyrosine. RESULTS: MCA diameter (mean+/-SD) was greater in EC-SOD versus WT mice after SAH but not sham surgery (EC-SOD SAH=56+/-10 microm; WT SAH=38+/-13 microm [P<0.01]; EC-SOD sham=99+/-16 microm; WT sham=100+/-15 microm). SAH decreased median (range) neurological score (scoring scale, 9 to 39; no deficit=39) versus shams, but there was no difference between EC-SOD and WT groups (EC-SOD SAH=26 [23 to 30]; WT SAH=23 [19 to 29] [P=0.27]; EC-SOD sham=39 [39]; WT sham=39 [39]). Sensory-motor deficits correlated with MCA diameter (P<0.001) but worsened primarily between 60 and 50 micro m, plateauing below this threshold. The percentage of mice with MCA nitrotyrosine staining increased after SAH in WT (sham=29%; SAH=100% [P<0.05]) but not EC-SOD (sham=33%; SAH=44% [P=0.80]) mice. CONCLUSIONS: Endogenous overexpression of EC-SOD attenuated vasospasm and oxidative stress but failed to reduce neurological deficits after SAH. Extracellular *O2- likely plays a direct role in the etiology of vasospasm.

Single nucleotide polymorphism (G994-->T) in the plasma platelet-activating factor-acetylhydrolase gene is associated with graft patency of femoropopliteal bypass.

BACKGROUND: Plasma platelet-activating factor-acetylhydrolase (PAF-AH) is known to catalyze platelet-activating factor (PAF). The single nucleotide polymorphism (SNP) of plasma PAF-AH gene (G994 -->T in exon 9) is associated with a decreased level of plasma PAF-AH activity. This study analyzed the risk of the SNP on graft occlusion of femoropopliteal bypass in patients with atherosclerotic occlusive disease. METHODS: We retrospectively assessed the patency of 50 above-knee femoropopliteal bypass grafting in 50 patients. Genomic DNA was analyzed for the mutant allele. Plasma PAF-AH activity was measured by radioimmunoassay. RESULTS: The 10-year cumulative primary patency of the bypass was 78.5% in GG (normal genotype) and 50.0% in GT (heterozygous) or TT (homozygous deficient) (P <.05, Kaplan-Meier method). The relative risk of graft failure in GT or TT genotypes was 1.68 (P =.08, Cox proportional hazards model). PAF-AH activity (nmol/min/50 microL) was 1.92 +/- 0.82 in patients with patent grafts and 1.42 +/- 0.47 in those with occluded grafts (mean +/- standard deviation; P <.05, unpaired t test). CONCLUSIONS: The SNP of plasma PAF-AH was associated with a decreased primary graft patency of above-knee femoropopliteal bypass. The risk of graft failure may increase when patients have the SNP. To confirm the independent risk of graft failure by the SNP, further study is necessary and prospective study should be performed.

Is there a role of angiotensin-converting enzyme gene polymorphism in the failure of arteriovenous femoral shunts for hemodialysis?

In humans, thrombosis and neointimal hyperplasia are the major factors responsible for prosthetic graft occlusion. Previous studies suggest that the renin-angiotensin system is one of the key enzymes in the vascular system and has been implicated in the pathogenesis of thrombosis and neointimal hyperplasia. We conducted a case-control study to determine the frequency of the different angiotensin-converting enzyme (ACE) genotypes among the patients who had PTFE graft implantation for hemodialysis access. Between 1997 and 1999, 30 graft implantations were performed. Twelve individuals (40%) developed thrombotic complications, 8 of the 12 patients had ACE ID polymorphism, and 2 patients had DD and 2 patients had II polymorphism. The ID polymorphism was significantly more frequent in the thrombosed arteriovenous (A-V) grafts than in nonthrombosed A-V grafts (chi2 = 7.57 and p = 0.02). Overall, the frequency of the D and I alleles was 66.6 and 33.3%, respectively. In conclusion, ID polymorphism of the ACE gene plays an important role in the pathogenesis of vascular access thrombosis in subjects undergoing hemodialysis for chronic renal failure.