Current Vascular Pharmacology - Volume 11, Issue 1, 2013

Chronic arterial occlusion leads to growth of collaterals - a process termed arteriogenesis, in which macrophages play a prominent role in remodelling and growth. However, a detailed analysis which of distinct macrophage subpopulations involved in arteriogenesis has never been performed. In the present study the temporal and spatial distribution of macrophage subtypes during arteriogenesis in a rat model with chronically elevated fluid shear stress (FSS) is investigated. Local macrophage subpopulations were histologically immuno-phenotyped using CD68 (a ubiquitous macrophage marker) and CD163, a specific M2 macrophage marker. Without occlusion few M2-macrophages reside in the perivascular space. Early after occlusion (12h) the number of M2 macrophages increases strongly and M1 macrophages begin emerging into the collateral. After 3 days they appear in the perivascular space. Both macrophage subtypes increase until 28d after treatment, whereas M2 macrophages dominate at the site of collateral growth. The local distribution of the subpopulations changes during the arteriogenic process. Whereas M1 macrophages are detected directly adjacent to the media, M2 macrophages are present in the most outer perivascular region of the growing collateral vessel. Systemic alterations of blood leucocytes in mice after femoral artery ligature (FAL) were investigated by FACS analysis of serial blood samples. During collateral remodelling histological changes were not reflected in circulating monocytes in the peripheral blood. The activation state of macrophages in mice with FAL was modulated by injections of either dexamethasone or the interleukins IL10 or IL3/IL14. The arteriogenic response was assessed by hind limb perfusion with laser Doppler measurements after 3, 7 and 14d. Suppressing inflammatory monocyte subtypes (M1) with dexamethasone led to impaired perfusion recovery after FAL in mice, whereas IL10 or IL4/IL13 application significantly increased perfusion recovery. This investigation demonstrates that a forced shift towards M2 macrophages improves the arteriogenic response. The distinct early increase and spatial distribution of M2 macrophages support the idea that this subtype plays a predominant role during collateral remodelling.

Objective: Lack of the adhesion molecule CD44 reduces collateral artery growth (arteriogenesis) in a murine hindlimb model. CD44 function is influenced by expression of 10 alternatively spliced exons (v1-v10), with unknown effects on arteriogenesis. As the variant exon CD44v3 binds heparan sulphate and facilitates preservation of growth factors, we hypothesized that the variably spliced exon region of CD44, especially exon CD44v3, is involved in arteriogenesis. Materials and Methods: The right femoral artery of C57BL/6J-mice was ligated and tissue was processed for histological and qPCR analysis of CD44-isoform expression. Microsphere perfusion measurements were performed in mice lacking the variably spliced exon region (CD44s knock-in mice), and in knock-in strains with specific isoform expression (CD44v3-10 and CD44v4-10), as well as in double knock-in mice, expressing CD44v3-10 and CD44s. Results: Expression of total CD44 and CD44v3 mRNA following femoral artery ligation was increased, accompanied by increased mRNA levels of the CD44-relevant splicing factors Tra2-beta1 and SRm160. CD44v3-expression was limited to the vessel wall of growing collateral arteries. Perfusion restoration was significantly reduced in mice lacking the variably spliced exon region (CD44s):20.1±1.3%, compared to the background strain: 57.3±2.2%. Mice expressing exon v3 (CD44v3-10) showed perfusion percentages of 25.9±1.1%, compared to mice lacking this exon (CD44v4-10):19.1±0.7%. Combined expression of CD44v3 and CD44s further improved perfusion restoration: 33.1±2.6%. Conclusion: Total CD44 and CD44v3 mRNA are upregulated during arteriogenesis. The absence of the variably spliced exon region impairs arteriogenesis. Presence of exon v3 of CD44 results in improved arteriogenesis. Expression of CD44s and CD44v3 provides a synergistic effect on arteriogenesis. As this combined expression still resulted in hampered arteriogenesis, a specific role of exon v2 in arteriogenesis appears likely.

Objective: The adaptive growth of blood vessels is important to prevent tissue loss following arterial occlusion. Extravasation of monocytes is essential for this process. The peptidase CD26 targets SDF-1 alpha, a chemokine regulating monocyte trafficking. We hypothesized that blocking SDF-1 alpha inactivation, using a commercially available CD26 inhibitor, accelerates perfusion recovery without detrimental side effects on plaque stability. Methods and Results: Atherosclerosis prone ApoE-/- mice underwent femoral artery ligation and received a CD26 inhibitor or placebo. CD26 inhibition increased short term (7 days) perfusion recovery after both single and daily doses compared to placebo, 36%±2 (p=0.017) and 39%±2 (p=0.008) vs. 29%±3 respectively. Long term (56 days) perfusion recovery increased after daily treatment compared to placebo 83%±3 vs. 60%±2, (p<0.001). CD26 inhibition did not result in increased atherosclerotic plaque instability or inflammatory cell infiltration. CD26 inhibition increased macrophage number around growing collaterals, SDF-1 alpha plasma levels and monocyte expression of the activation marker CD11b and the SDF-1 alpha receptor CXCR-4. Conclusions: CD26 inhibition enhanced perfusion recovery following arterial occlusion via attenuated SDF-1 alpha inactivation and increased monocyte activation. There was no observable aggravation of atherosclerosis and CD26 inhibition could therefore offer a novel approach for therapeutic arteriogenesis in patients.

Hif-1α, a master regulator of ischemia-responsive gene induction, controls pro-angiogenic gene expression of VEGF-A, flt-1, IGF-1 and erythropoietin, rendering its overexpression an attractive tool for therapeutic neovascularization. Utilizing an adenoviral vector system, we investigated the efficacy of selective pressure-regulated venous retroinfusion of an enhanced Hif-1α mutant (Hif-1α/VP16) in a randomized investigator-blinded study. Methods: Pigs were subjected to percutaneous implantation of a reduction-stent into the circumflex artery, leading to progressive stenosis and complete occlusion at day 28. Selective pressure-regulated retroinfusion of the great cardiac vein was performed at day 28 for regional delivery of either saline or empty vector or Ad2/Hif-1α/VP16. Collateral growth and global myocardial function were obtained by fluoroscopy, whereas regional blood flow and regional myocardial function were assessed by fluorescent microsphere analysis and sonomicrometry, respectively. Capillary density in the ischemic myocardium was analyzed by PECAM-1 staining. Results: Compared to saline and Ad empty vector controls, overexpression of Hif-1α in the ischemic region induced an increase of small (capillary) and large (collateral) vessels, resulting in an improved perfusion of the ischemic myocardium. Concomitantly, an ischemia induced loss of myocardial function (hibernating myocardium) was resolved only after transfection with the Hif 1-α transgene, but not the empty vector or saline control. Conclusion: Retroinfusion of Ad2/Hif-1α/VP16, combining a master pro-angiogenic protein with regional myocardial application, may offer an efficient approach to cardiac gene therapy of chronic ischemic cardiomyopathy.

Aims: Recent data have demonstrated the feasibility of therapeutic induction of coronary collateral growth (arteriogenesis); however, mechanisms of action of such therapeutic collateral stimulation in humans are unknown. The aim of this study was to evaluate potential mechanisms, especially the involvement of arteriogenesis-relevant genes. Methods and Results: A total of 52 patients were randomized into two groups: subcutaneous G-CSF (10μg/kg; n=26) or placebo (n=26). Before and after this 2-week treatment, collateral-flow index (CFI) was determined by simultaneous measurement of mean aortic, distal coronary occlusive and central venous pressure. CD34+ endothelial progenitor cells (EPC) and monocytes were quantified before, during and after treatment; gene-expression analysis of monocytes was performed with real-time polymerase chain reaction (RT-PCR). G-CSF lead to a significant increase of EPC and monocytes (4.8 and 2.6 fold, p<0.05); for both cell types, the extent of increase correlated with CFI increase (r=0.23 and 0.14, p<0.05). G-CSF also induced a change in gene expression of pro-and anti-arteriogenic genes in monocytes. Among nine assessed genes, three were found to be differentially regulated (IL8, JAK2, and PNPLa4; p<0.05). Conclusions: The mechanism of induction of collateral growth by G-CSF is related to an increase of EPC and of peripheral monocytes. It also leads to a change toward a pro-arteriogenic gene expression in peripheral monocytes.

Antiplatelet therapy plays an important role in the management of atherosclerotic disease and numerous studies have shown their efficacy in the reduction of cardiovascular mortality and morbidity. Antiplatelets are given in patients subjected to lower limb bypass aiming not only to reduce cardiovascular mortality and morbidity but also improve graft patency. Various antiplatelet agents have been used for this purpose. The aim of this review article is to critically evaluate the existing evidence on the impact of antiplatelet therapy for maintaining infrainguinal graft patency and highlight the mechanisms involved along these lines.

Statins exert several beneficial effects on patients with peripheral arterial disease, whether managed conservatively or undergoing open surgical/endovascular procedures. Statins improve perioperative and long-term mortality and morbidity rates in these patients. There is also evidence that statins improve infrainguinal bypass graft patency rates and are associated with reduced graft restenosis and amputation rates in these procedures. This review considers the beneficial effects of statins on patients undergoing infrainguinal bypass graft procedures and discusses the implicated pathomechanisms.

Stroke is a devastating disease affecting millions of people worldwide every year. Female stroke victims have higher mortality rates and they do not re-cover as well as men. Women's longevity and different vascular risk factor burden like a larger prevalence of atrial fibrillation play a role. Women also have unique risk factors such as oral contraception, pregnancy, estrogen decrease after the menopause and hormone replacement therapy, which should all be evaluated and taken into consideration in treatment decisions both in the acute phase of stroke and in secondary prevention. In this review, the evidence regarding these hormonal aspects and the risk of stroke in women are evaluated. The relevant guidelines are studied and research gaps identified. Future topics for research are recommended and current treatment possibilities and their risks discussed.

In recent years, we have witnessed a revolution in the treatment of coronary artery disease. The development and improvement of drug eluting stents (DES) have lowered the incidence of restenosis to one-digit figures. In the search for a superior efficacy, animal models have played a key role. The classical swine model of coronary stenting remains the preferred model to measure restenosis, although the rabbit iliac artery stenting has become an accepted alternative. After widespread clinical use of DES, an unforeseen complication arose: late stent thrombosis. In a back-to-bench step, some data from animal models helped to explain the phenomenon. A delayed and incomplete vascular healing was detected. Toxic and hypersensitivity reactions to polymers and/or drugs seem to be the underlying causes. So, translational research focused on the safety aspect of these devices: development of better drug carriers as absorbable polymers or fully bioresorbable scaffolds, selection of different drugs and assessment of the re-endothelialization process. We review and evaluate the efficacy and safety of coronary stents in different animal models. Further improvements in this field such as, the selection of better animal models (e.g. hyperlipidemic, diabetic, atherosclerotic) that closely mimic the clinical setting and longer follow-up periods to detect late complications are also discussed.

Objectives: Some early trials comparing intensive glucose control in type 2 diabetics with an acute myocardial infarction (MI) reported a decrease in mortality over a short period of follow up leading to a presumption of improved survival with intensive glucose control. Later data refuted this hypothesis. The 2009 ACC/AHA focused update on ST elevation MI gave a weak recommendation for the use of an insulin based regimen to achieve and maintain blood glucose less than 180 mg/dL. We decided to assess the validity of this recommendation. Methods: The authors searched the Pub- Med, Cochrane CENTRAL and EMBASE databases for randomized controlled trials from 1965 through 2011.Trials included were direct head-to-head comparisons of an intensive blood glucose control strategy using pharmacological means (insulin in most cases) with a less intensive regimen. The primary outcome assessed was the risk of all -cause mortality in the two groups at the end of follow up. Also assessed was the rate of hypoglycemia. The methodological quality of the studies was assessed. Event rates were compared using a forest plot of relative risk (RR; 95% confidence interval [CI]) using a random effects model (Mantel-Haenszel) assuming inter-study heterogeneity. Statistical analysis was done with Review Manager V5.1 and SYSTAT. Meta-regression was done with duration of therapy as covariate. Results: Three studies (total N = 2113) met the inclusion - exclusion criteria. Mortality was not different between the groups (RR 0.94, 95% CI of 0.66-1.34; p=0.73.). Rate of hypoglycemia was significantly higher in the intensive glucose control group (RR 13.40, 95% CI 3.69-48.61; p<0.01), with a 12% absolute risk increase and a number needed to harm (NNH) of 9 (95% CI 6.8- 9.8)-even without achieving target glycemic control. Neither did intensive control improve CHF, arrhythmias and reinfarction rates. Meta regression revealed that mortality with intensive glycemic control was worse with increased duration of therapy (p=0.001, for trend). Conclusions: This systematic review suggests limited benefit of intensive glycemic control in type 2 diabetics with an MI, with a significant risk of serious hypoglycemia.

Background: Epoxyeicosatrienoic acids (EETs) have been shown to play a role in cardiovascular protection by reducing ischemia reperfusion injury, producing anti-inflammatory effects, and promoting angiogenesis. EETs are regulated through conversion to less active corresponding diols by soluble epoxide hydrolase (sEH). Inhibition of sEH enhances the beneficial properties of EETs and has been investigated as a possible treatment for cardiovascular diseases. Content: sEH inhibitors (sEHIs) have anti-inflammatory effects by stabilizing anti-inflammatory EETs. Additionally, sEHIs strongly inhibit and reverse cardiac hypertrophy. sEHIs have been shown to protect myocardial cells from ischemiareperfusion injury, treat atherosclerosis and prevent the development of hypertension. sEHIs promote blood vessels to release bradykinin via an EET-mediated STAT3 signaling pathway to elicit tolerance to ischemia. Summary: Inhibition of sEH has been shown to improve several aspects of cardiovascular diseases, including inflammation, hypertension, cardiac hypertrophy and atherosclerosis. For this reason, sEHIs are promising new pharmaceutical for the treatment of cardiovascular diseases.

Introduction/Aim: We reviewed the literature for studies evaluating the effects of statins on vascular patients undergoing open surgical or endovascular procedures. Methods: MEDLINE was searched using the search terms “statins and vascular surgery”, “statins and endovascular procedures”, “statins and perioperative effects” and “statins and postoperative complications”. Results: Preoperative statin use is associated with lower perioperative/periprocedural death, myocardial infarction and stroke rates. Statins may also reduce postoperative complications as well as hospitalization rates and costs. Statins reduce the incidence of postoperative/postprocedural renal insufficiency and help the earlier recovery of complete kidney function in vascular patients. A loading dose of statins prior to a procedure may be associated with improved cardiovascular outcomes. Conclusions: Statins are associated with several beneficial actions in patients undergoing open surgical or endovascular procedures. Nevertheless, statin use in vascular patients still remains underutilized and suboptimal. Ideally, statins should be initiated a minimum of 2 weeks before the procedure. Extended-release formulas may be preferable perioperatively to cover the first 1-2 days after the procedure when oral intake may not be feasible. Statins should be administered to all vascular disease patients, whether they are managed conservatively or are undergoing open surgical or endovascular procedures.