Collateral Growth Research Articles

Coronary collateral growth—Back to the future

The coronary collateral circulation is critically important as an adaptation of the heart to prevent the damage from ischemic insults. In their native state, collaterals in the heart would be classified as part of the microcirculation, existing as arterial-arterial anastomotic connections in the range of 30 to 100 μM in diameter. However, these vessels also show a propensity to remodel into components of the macrocirculation and can become arteries larger than 1000 μM in diameter. This process of outward remodeling is critically important in the adaptation of the heart to ischemia because the resistance to blood flow is inversely related to the fourth power of the diameter of the vessel. Thus, an expansion of a vessel from 100 to 1000 μM would reduce resistance (in this part of the circuit) to a negligible amount and enable delivery of flow to the region at risk. Our goal in this review is to highlight the voids in understanding this adaptation to ischemia-the growth of the coronary collateral circulation. In doing so we discuss the controversies and unknown aspects of the causal factors that stimulate growth of the collateral circulation, the role of genetics, and the role of endogenous stem and progenitor cells in the context of the normal, physiological situation and under more pathological conditions of ischemic heart disease or with some of the underlying risk factors, e.g., diabetes. The major conclusion of this review is that there are many gaps in our knowledge of coronary collateral growth and this knowledge is critical before the potential of stimulating collateralization in the hearts of patients can be realized. This article is part of a Special Issue entitled "Coronary Blood Flow".

Resolution of Mitochondrial Oxidative Stress Rescues Coronary Collateral Growth in Zucker Obese Fatty Rats

We have previously found abrogated ischemia-induced coronary collateral growth in Zucker obese fatty (ZOF) rats compared with Zucker lean (ZLN) rats. Because ZOF rats have structural abnormalities in their mitochondria suggesting dysfunction and also show increased production of O(2), we hypothesized that mitochondrial dysfunction caused by oxidative stress impairs coronary collateral growth in ZOF. Increased levels of reactive oxygen species were observed in aortic endothelium and smooth muscle cells in ZOF rats compared with ZLN rats. Reactive oxygen species levels were decreased by the mitochondria-targeted antioxidants MitoQuinone (MQ) and MitoTempol (MT) as assessed by MitoSox Red and dihydroethidine staining. Lipid peroxides (a marker of oxidized lipids) were increased in ZOF by ≈47% compared with ZLN rats. The elevation in oxidative stress was accompanied by increased antioxidant enzymes, except glutathione peroxidase-1, and by increased uncoupling protein-2 in ZOF versus ZLN rats. In addition, elevated respiration rates were also observed in the obese compared with lean rats. Administration of MQ significantly normalized the metabolic profiles and reduced lipid peroxides in ZOF rats to the same level observed in lean rats. The protective effect of MQ also suppressed the induction of uncoupling protein-2 in the obese rats. Resolution of mitochondrial oxidative stress by MQ or MT restored coronary collateral growth to the same magnitude observed in ZLN rats in response to repetitive ischemia. We conclude that mitochondrial oxidative stress and dysfunction play a key role in disrupting coronary collateral growth in obesity and the metabolic syndrome, and elimination of the mitochondrial oxidative stress with MQ or MT rescues collateral growth.

Abstract 17107: Induced Vascular Progenitor Cells Derived from Endothelial Cells Stimulate Coronary Collateral Growth

Liya Yin, 2011 Finalist and Presenting Author

Abstract 18002: Coronary Collaterals Predict Improved Survival and Allograft Function in Patients with Coronary Allograft Vasculopathy

Coronary allograft vasculopathy (CAV) remains the most prevalent cause of allograft failure and cardiac mortality beyond the first year following heart transplantation. To date there are few proven therapies for this important disease. The presence of coronary collaterals has previously been demonstrated to impart a favorable prognosis in patients with ischemic heart disease. To determine whether the development of coronary collaterals is also associated with improved outcomes in patients with CAV, we performed a retrospective cohort study of all patients followed in the heart transplant clinic at Barnes Jewish Hospital between 1994 and 2008. The primary endpoint was the composite of all cause mortality, retransplantation, and inotrope dependence. LV end diastolic pressure and NYHA class served as surrogate measures of allograft function and heart failure symptoms. We screened 493 patients and identified 60 (13%) with moderate to severe CAV as defined by the International Society of Heart and Lung Transplantation. Coronary collaterals were present in 34 (57%) subjects. Patients with collaterals had a significantly lower risk of death, retransplanation, or inotrope dependence compared to patients without collaterals (OR 0.15, 95% CI 0.05-0.48, p= 0.002). In addition, patients with collaterals had lower LV end diastolic pressures and NYHA class. Multivariate analysis confirmed that the presence of collaterals independently predicted each of these outcomes. Immunohistochemical staining of biopsy specimens collected from patients with CAV revealed alterations in microvascular density that correlated with the presence of angiographically visible collaterals. Together these data demonstrate that the development of coronary collaterals predicts a favorable prognosis in patients with CAV and suggests that interventions aimed at promoting collateral growth may serve as effective therapies for this disease.

Abstract 17107: Induced Vascular Progenitor Cells Derived From Endothelial Cells Stimulate Coronary Collateral Growth

Although regenerative medicine has great potential in stimulating vascular growth in the heart, there have been mixed results and the ideal cell type for therapy has not been resolved. Induced pluripotent cells (iPSCs) show promise, because they can be autologous, but they suffer from the problem of potential tumor formation. To circumvent this problem, we reasoned that reprogramming cells to a progenitor-type cell, rather than to pluripotency, but would reduce the chances for tumor formation; yet still enable their application in stimulating coronary collateral growth in a rat model of repetitive ischemia. Accordingly, we reprogrammed endothelial cells (EC(s)) to “induced vascular progenitor cell(s)” (iVPC(s)), which should remain committed to a vascular lineage. We hypothesized that these cells would better stimulate coronary collateral growth than fully reprogrammed iPSCs because the latter can differentiate into various cell types other than vascular lineage. Rat vascular ECs were transduced with Oct4, Klf4, Sox2 and c-Myc. A population of reprogrammed cells expressing pluripotent markers, Oct4, SSEA-1, Rex1 and AP and markers of hemangioblasts, CD133, Flk1, c-kit were generated. These cells were named iVPCs, because they remained committed to vascular lineage and could differentiate into vascular ECs or vascular smooth muscle cells in vitro. iVPCs demonstrated better in vitro angiogenic potential (tube network on 2D culture, tube formation in serum reduced matrigel) than native ECs. In contrast to iPSCs, iVPCs had far less risk of teratoma formation. When iVPCs were implanted into rat myocardium, they engrafted into the blood vessels, increased coronary collateral flow measured by microspheres and improved cardiac function during coronary occlusion measured by echocardiography better than iPSCs or sham treatment (all difference were significant at P<0.05). Thus we successfully reprogrammed ECs into iVPCs. iVPCs had a better effect on coronary collateral growth and cardiac function during a coronary occlusion in vivo than iPS cells did. We conclude that “induced vascular progenitor cells,” generated by partial reprogramming of ECs, are an ideal cell type for regenerative therapy to stimulate coronary collateral growth.

Induction of Vascular Progenitor Cells From Endothelial Cells Stimulates Coronary Collateral Growth

A well-developed coronary collateral circulation improves the morbidity and mortality of patients following an acute coronary occlusion. Although regenerative medicine has great potential in stimulating vascular growth in the heart, to date there have been mixed results, and the ideal cell type for this therapy has not been resolved. To generate induced vascular progenitor cells (iVPCs) from endothelial cells, which can differentiate into vascular smooth muscle cells (VSMCs) or endothelial cells (ECs), and test their capability to stimulate coronary collateral growth. We reprogrammed rat ECs with the transcription factors Oct4, Klf4, Sox2, and c-Myc. A population of reprogrammed cells was derived that expressed pluripotent markers Oct4, SSEA-1, Rex1, and AP and hemangioblast markers CD133, Flk1, and c-kit. These cells were designated iVPCs because they remained committed to vascular lineage and could differentiate into vascular ECs and VSMCs in vitro. The iVPCs demonstrated better in vitro angiogenic potential (tube network on 2-dimensional culture, tube formation in growth factor reduced Matrigel) than native ECs. The risk of teratoma formation in iVPCs is also reduced in comparison with fully reprogrammed induced pluripotent stem cells (iPSCs). When iVPCs were implanted into myocardium, they engrafted into blood vessels and increased coronary collateral flow (microspheres) and improved cardiac function (echocardiography) better than iPSCs, mesenchymal stem cells, native ECs, and sham treatments. We conclude that iVPCs, generated by partially reprogramming ECs, are an ideal cell type for cell-based therapy designed to stimulate coronary collateral growth.

Macrophage skewing by Phd2 haplodeficiency prevents ischaemia by inducing arteriogenesis

PHD2 serves as an oxygen sensor that rescues blood supply by regulating vessel formation and shape in case of oxygen shortage. However, it is unknown whether PHD2 can influence arteriogenesis. Here we studied the role of PHD2 in collateral artery growth by using hindlimb ischaemia as a model, a process that compensates for the lack of blood flow in case of major arterial occlusion. We show that Phd2 (also known as Egln1) haplodeficient (Phd2(+/-)) mice displayed preformed collateral arteries that preserved limb perfusion and prevented tissue necrosis in ischaemia. Improved arteriogenesis in Phd2(+/-) mice was due to an expansion of tissue-resident, M2-like macrophages and their increased release of arteriogenic factors, leading to enhanced smooth muscle cell (SMC) recruitment and growth. Both chronic and acute deletion of one Phd2 allele in macrophages was sufficient to skew their polarization towards a pro-arteriogenic phenotype. Mechanistically, collateral vessel preconditioning relied on the activation of canonical NF-κB pathway in Phd2(+/-) macrophages. These results unravel how PHD2 regulates arteriogenesis and artery homeostasis by controlling a specific differentiation state in macrophages and suggest new treatment options for ischaemic disorders.

The coronary circulation in exercise training.

Exercise training (EX) induces increases in coronary transport capacity through adaptations in the coronary microcirculation including increased arteriolar diameters and/or densities and changes in the vasomotor reactivity of coronary resistance arteries. In large animals, EX increases capillary exchange capacity through angiogenesis of new capillaries at a rate matched to EX-induced cardiac hypertrophy so that capillary density remains normal. However, after EX coronary capillary exchange area is greater (i.e., capillary permeability surface area product is greater) at any given blood flow because of altered coronary vascular resistance and matching of exchange surface area and blood flow distribution. The improved coronary capillary blood flow distribution appears to be the result of structural changes in the coronary tree and alterations in vasoreactivity of coronary resistance arteries. EX also alters vasomotor reactivity of conduit coronary arteries in that after EX, α-adrenergic receptor responsiveness is blunted. Of interest, α- and β-adrenergic tone appears to be maintained in the coronary microcirculation in the presence of lower circulating catecholamine levels because of increased receptor responsiveness to adrenergic stimulation. EX also alters other vasomotor control processes of coronary resistance vessels. For example, coronary arterioles exhibit increased myogenic tone after EX, likely because of a calcium-dependent PKC signaling-mediated alteration in voltage-gated calcium channel activity in response to stretch. Conversely, EX augments endothelium-dependent vasodilation throughout the coronary arteriolar network and in the conduit arteries in coronary artery disease (CAD). The enhanced endothelium-dependent dilation appears to result from increased nitric oxide bioavailability because of changes in nitric oxide synthase expression/activity and decreased oxidant stress. EX also decreases extravascular compressive forces in the myocardium at rest and at comparable levels of exercise, mainly because of decreases in heart rate and duration of systole. EX does not stimulate growth of coronary collateral vessels in the normal heart. However, if exercise produces ischemia, which would be absent or minimal under resting conditions, there is evidence that collateral growth can be enhanced. While there is evidence that EX can decrease the progression of atherosclerotic lesions or even induce the regression of atherosclerotic lesions in humans, the evidence of this is not strong due to the fact that most prospective trials conducted to date have included other lifestyle changes and treatment strategies by necessity. The literature from large animal models of CAD also presents a cloudy picture concerning whether EX can induce the regression of or slow the progression of atherosclerotic lesions. Thus, while evidence from research using humans with CAD and animal models of CAD indicates that EX increases endothelium-dependent dilation throughout the coronary vascular tree, evidence that EX reverses or slows the progression of lesion development in CAD is not conclusive at this time. This suggests that the beneficial effects of EX in CAD may not be the result of direct effects on the coronary artery wall. If this suggestion is true, it is important to determine the mechanisms involved in these beneficial effects.

Effect of Hypoxia-Inducible Factor-1α Gene Therapy on Walking Performance in Patients With Intermittent Claudication

Hypoxia-inducible factor-1α (HIF-1α) is a transcriptional regulatory factor that orchestrates cellular responses to hypoxia. It increases collateral vessel growth and blood flow in models of hind-limb ischemia. This study tested whether intramuscular administration of Ad2/HIF-1α/VP16, an engineered recombinant type 2 adenovirus vector encoding constitutively active HIF-1α, improves walking time in patients with peripheral artery disease and intermittent claudication. Two hundred eighty-nine patients with claudication were randomized in a double-blind manner to 1 of 3 doses of Ad2/HIF-1α/VP16 (2×10(9), 2×10(10), or 2×10(11) viral particles) or placebo, administered by 20 intramuscular injections to each leg. Graded treadmill tests were performed at baseline and then 3, 6, and 12 months after treatment. The primary end point was the change in peak walking time from baseline to 6 months. The secondary end point was change in claudication onset time, and tertiary end points included changes in ankle-brachial index and quality-of-life assessments. Median peak walking time increased by 0.82 minutes (interquartile range, -0.05-1.93 minutes) in the placebo group and by 0.82 minutes (interquartile range, -0.07-2.12 minutes), 0.28 minutes (interquartile range, -0.37-1.70 minutes), and 0.78 minutes (interquartile range, -0.02-2.10 minutes) in the HIF-1α 2×10(9), 2×10(10), and 2×10(11) viral particle groups, respectively (P=NS between placebo and each HIF-1α treatment group). There were no significant differences in claudication onset time, ankle-brachial index, or quality-of-life measurements between the placebo and each HIF-1α group. Gene therapy with intramuscular administration of Ad2/HIF-1α/VP16 is not an effective treatment for patients with intermittent claudication. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00117650.

Circulation : Clinical Summaries

<i>Circulation</i> : Clinical Summaries

MMPs 2 and 9 are essential for coronary collateral growth and are prominently regulated by p38 MAPK

Transient, repetitive ischemia (RI) stimulates coronary collateral growth (CCG) in normal, healthy (SD) rats, which requires p38 MAPK activation. In contrast, RI does not induce CCG in the metabolic syndrome (JCR) rats, which is associated with lack of p38 MAPK activation. The functional consequences of p38 MAPK activation in CCG remain unknown. Theoretically, effective collateral growth would require extracellular matrix remodeling; however, direct assessment as well as identification of proteases responsible for this degradation are lacking. In this study, we investigated the role of p38 MAPK in the regulation of matrix metalloproteinases 2 and 9 (MMPs 2 and 9) and their requirement for CCG in SD vs. JCR rats. The rats underwent the RI protocol (8 LAD occlusions, 40s each, every 20min, in 8h cycles for 0, 3, 6, or 9days). MMP expression was measured in the ischemic, collateral-dependent zone (CZ) and the normal zone (NZ) by Western blot, and MMP activity by zymography. Expression and activation of MMP 2 and 9 were significantly increased (~3.5 fold) on day 3 of RI in the CZ of SD rats. In vivo p38 MAPK inhibition completely blocked RI-induced MMP 2 and 9 expression and activation. MMP activation correlated with increased degradation of components of the basement membrane and the vascular elastic laminae: elastin (~3 fold), laminin (~3 fold) and type IV collagen (~2 fold). This was blocked by MMP 2 and 9 inhibition, which also abolished RI-induced CCG. In contrast, in JCR rats, RI did not induce expression or activation of MMP 2 or 9 and there was no associated degradation of elastin, laminin or type IV collagen. In conclusion, MMP 2 and 9 activation is essential for CCG and is mediated, in part, by p38 MAPK. Furthermore, compromised CCG in the metabolic syndrome may be partially due to the lack of p38 MAPK-dependent activation of MMP 2 and 9 and resultant decreased extracellular matrix degradation.

Heart-rate reduction by If-channel inhibition with ivabradine restores collateral artery growth in hypercholesterolemic atherosclerosis

Collateral arteries protect tissue from ischaemia. Heart rate correlates with vascular events in patients with arterial obstructive disease. Here, we tested the effect of heart-rate reduction (HRR) on collateral artery growth. The I(f)-channel inhibitor ivabradine reduced heart rate by 11% in wild-type and 15% in apolipoprotein E (ApoE)(-/-) mice and restored endothelium-dependent relaxation in aortic rings of ApoE(-/-) mice. Microsphere perfusion and angiographies demonstrated that ivabradine did not change hindlimb perfusion in wild-type mice but improved perfusion in ApoE(-/-) mice from 40.5 ± 15.8-60.2 ± 18.5% ligated/unligated hindlimb. Heart rate reduction (13%) with metoprolol failed to improve endothelial function and perfusion. Protein expression of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS, and eNOS activity were increased in collateral tissue following ivabradine treatment of ApoE(-/-) mice. Co-treatment with nitric oxide-inhibitor N (G)-nitro-L-arginine methyl ester abolished the effects of ivabradine on arteriogenesis. Following ivabradine, classical inflammatory cytokine expression was lowered in ApoE(-/-) circulating mononuclear cells and in plasma, but unaltered in collateral-containing hindlimb tissue, where numbers of perivascular macrophages also remained unchanged. However, ivabradine reduced expression of anti-arteriogenic cytokines CXCL10and CXCL11 and of smooth muscle cell markers smoothelin and desmin in ApoE(-/-) hindlimb tissue. Endothelial nitric oxide synthase and inflammatory cytokine expression were unchanged in wild-type mice. Ivabradine did not affect cytokine production in HUVECs and THP1 mononuclear cells and had no effect on the membrane potential of HUVECs in patch-clamp experiments. Ivabradine-induced HRR stimulates adaptive collateral artery growth. Important contributing mechanisms include improved endothelial function, eNOS activity, and modulation of inflammatory cytokine gene expression.

Myoblast-mediated gene therapy via encephalomyosynangiosis – A novel strategy for local delivery of gene products to the brain surface

An encephalomyosynangiosis (EMS) is a temporal muscle graft that is placed onto the surface of the brain to serve as a source for collateral vessel growth for brain revascularization in patients with Moyamoya Disease (MMD). To facilitate an EMS in patients with occlusive cerebrovascular diseases other than MMD, the transfer of pro-angiogenic genes via transplantation of retrovirally transduced myoblasts into the temporal muscle may represent an innovative approach to augment collateralization. Thus, we tested whether retrovirally transfected myoblasts can spontaneously fuse with the non-ischemic and uninjured muscle tissue and if a reporter gene can be stably expressed within the temporal muscle of the EMS. Primary mouse myoblasts expressing a reporter gene were implanted into the temporal muscle prior to an EMS being performed on C57/BL6 mice. Three different implantation modalities were evaluated: (a) intramuscular injection, (b) application of a cell pellet and (c) a combination of both techniques. Myoblast implantation resulted in spontaneous fusion with the host muscle fibers and stable reporter gene expression at both the muscle/brain interface and within the non-ischemic and uninjured temporal muscle in all animals. The mean number of fused hybrid myofibers was 59±28 after injection, 37±30 after pellet application and 60±23 after a combination of both techniques. Regardless of the implantation modality, an abundant extracellular expression of the reporter gene was evident at the muscle/brain interface; in the case of myoblast delivery by injection, expression was also observed around the needle tract marking the implantation site. This method could be used in the future to deliver angiogenic growth factors to the muscle/brain interface in order to improve revascularization after an EMS.

Induction of Smooth Muscle Cell Migration During Arteriogenesis Is Mediated by Rap2

Collateral artery growth or arteriogenesis is the primary means of the circulatory system to maintain blood flow in the face of major arterial occlusions. Arteriogenesis depends on activation of fibroblast growth factor (FGF) receptors, but relatively little is known about downstream mediators of FGF signaling. We screened for signaling components that are activated in response to administration of FGF-2 to cultured vascular smooth muscle cells (VSMCs) and detected a significant increase of Rap2 but not of other Ras family members, which corresponded to a strong upregulation of Rap2 and C-Raf in growing collaterals from rabbits with femoral artery occlusion. Small interfering RNAs directed against Rap2 did not affect FGF-2 induced proliferation of VSMC but strongly inhibited their migration. Inhibition of FGF receptor-1 (FGFR1) signaling by infusion of a sulfonic acid polymer or infection with a dominant-negative FGFR1 adenovirus inhibited Rap2 upregulation and collateral vessel growth. Similarly, expression of dominant-negative Rap2 blocked arteriogenesis, whereas constitutive active Rap2 enhanced collateral vessel growth. Rap2 is part of the arteriogenic program and acts downstream of the FGFR1 to stimulate VSMC migration. Specific modulation of Rap2 might be an attractive target to manipulate VSMC migration, which plays a role in numerous pathological processes.

Arteriogenesis Is Modulated By Bradykinin Receptor Signaling

Positive outward remodeling of pre-existing collateral arteries into functional conductance arteries, arteriogenesis, is a major endogenous rescue mechanism to prevent cardiovascular ischemia. Collateral arterial growth is accompanied by expression of kinin precursor. However, the role of kinin signaling via the kinin receptors (B1R and B2R) in arteriogenesis is unclear. The purpose of this study was to elucidate the functional role and mechanism of bradykinin receptor signaling in arteriogenesis. Bradykinin receptors positively affected arteriogenesis, with the contribution of B1R being more pronounced than B2R. In mice, arteriogenesis upon femoral artery occlusion was significantly reduced in B1R mutant mice as evidenced by reduced microspheres and laser Doppler flow perfusion measurements. Transplantation of wild-type bone marrow cells into irradiated B1R mutant mice restored arteriogenesis, whereas bone marrow chimeric mice generated by reconstituting wild-type mice with B1R mutant bone marrow showed reduced arteriogenesis after femoral artery occlusion. In the rat brain 3-vessel occlusion arteriogenesis model, pharmacological blockade of B1R inhibited arteriogenesis and stimulation of B1R enhanced arteriogenesis. In the rat, femoral artery ligation combined with arterial venous shunt model resulted in flow-driven arteriogenesis, and treatment with B1R antagonist R715 decreased vascular remodeling and leukocyte invasion (monocytes) into the perivascular tissue. In monocyte migration assays, in vitro B1R agonists enhanced migration of monocytes. Kinin receptors act as positive modulators of arteriogenesis in mice and rats. B1R can be blocked or therapeutically stimulated by B1R antagonists or agonists, respectively, involving a contribution of peripheral immune cells (monocytes) linking hemodynamic conditions with inflammatory pathways.

Determinants of Preformed Collateral Vessels in the Human Heart without Coronary Artery Disease

Background: Coronary collaterals protect myocardium jeopardized by coronary artery disease (CAD). Promotion of collateral circulation is desirable before myocardial damage occurs. Therefore, determinants of collateral preformation in patients without CAD should be elucidated. Methods: In 106 patients undergoing coronary angiography who were free of coronary stenoses, a total of 39 clinical test variables were collected. The coronary collateral flow index (CFI) was measured. Stepwise multiple linear regression analysis was performed after choosing a restricted number of candidates emerging from univariate testing. Separate multiple regression analyses were performed in patients with and without beta-blocker therapy. Results: Nine parameters were found to be possible determinants of CFI by univariate analysis: arterial hypertension (aHT), dyslipidemia, statins, diuretics, age, height, heart rate (HR), pulse pressure amplitude, and left ventricular end-diastolic pressure (LVEDP). After multiple regression analysis, a low HR, absence of aHT, and elevated LVEDP were significantly related to CFI (F = 5.31, p = 0.002, adjusted r² = 0.12). In patients without beta-blockers, a low HR and absence of aHT were independent predictors of CFI (F = 8.03, p < 0.001, n = 50, adjusted r² = 0.30). Conclusions: A low HR and absence of aHT are both related to collateral preformation in humans. We suppose that bradycardia favors fluid shear stress in coronary arteries, thus triggering collateral growth.

Preeclampsia, a disease of the maternal endothelium: the role of antiangiogenic factors and implications for later cardiovascular disease.

Preeclampsia is a clinical syndrome defined as the new onset of hypertension and proteinuria during the second half of pregnancy.1 It afflicts 3% to 5% of pregnancies and is a leading cause of maternal mortality, especially in developing countries.2,3 Because the only known remedy is delivery of the placenta, in developed countries preeclampsia is an important cause of premature delivery, usually medically indicated for the benefit of the mother. This results in infant morbidity and substantial healthcare expenditure.4 Despite the considerable morbidity and mortality, the cause of preeclampsia has remained enigmatic. Both hypertension and proteinuria implicate the endothelium as the target of the disease. The hypertension of preeclampsia is characterized by peripheral vasoconstriction and decreased arterial compliance.5,6 The proteinuria of preeclampsia is associated with a pathognomonic renal lesion known as glomerular endotheliosis, in which the endothelial cells of the glomerulus swell and endothelial fenestrations are lost.7,8 Podocyturia has been recently associated with preeclampsia during clinical disease9; however, whether this is the cause or effect of proteinuria is unknown. The glomerular filtration rate is decreased compared with normotensive pregnant women; in rare cases, acute renal failure may develop. Preeclampsia is a systemic vascular disorder that may also affect the liver and the brain in the mothers. When the liver is involved, women may present with abdominal pain, nausea, vomiting, and elevated liver enzymes. Pathological examination of the liver reveals periportal and sinusoidal fibrin deposition and, in more extreme cases, hemorrhage and necrosis.10 The severe preeclampsia variant HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) occurs in ≈20% of women with severe preeclampsia,11 and is named not only for the liver involvement, but also for the disorder of the coagulation system that develops.12 Approximately 20% of …

Quantification of collateral artery growth by automated fluorescent microsphere perfusion

BackgroundSince their introduction, genetically modified mice have become more and more important to examine molecular mechanisms involved in vascular growth. Today the gold standard for measuring vessel conductivity is to directly assess in vivo perfusion. However, this usually becomes more complicated the smaller the animal, especially due to the need for extensive instrumentation and requirement of maximal vasodilation. MethodsWe developed an automated system that allows pressure-controlled in vivo perfusion of small animals with differently labeled fluorescent microspheres. ResultsBesides precise operation of the system (mean pressures divergence 0.08%), automation of small animal microsphere perfusion is reliable and highly accurate in mice with and without femoral artery occlusion. In sham-operated control mice, which did not undergo femoral occlusion, highly reproducible measurements of hind limb perfusion (right vs. left=1.03±0.037) could be assessed. In mice after unilateral femoral artery occlusion, mean perfusion ratios of the automated method (ratio occluded vs. non-occluded hind limb=0.598±0.046) were comparable to the manual approach (0.561±0.062). However, inter-individual variances were significantly smaller with the automated system. ConclusionWe describe here a novel and innovative technical approach for pressure-controlled fluid handling specifically designed for microsphere perfusion measurements in small animals.

Gene therapy for ischemic heart disease

Introduction: Coronary artery disease (CAD) is still the leading cause of death in industrialized nations. Even though revascularization strategies such as percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG) as well as drug therapy have significantly reduced mortality, about 30% of patients will develop chronic heart failure over time. Ischemic heart disease and heart failure are characterized by an adverse remodeling of the heart, featuring cardiomyocyte hypertrophy, increased fibrosis and capillary rarification.Areas covered: Beside an assessment of current vector systems, this review focuses on potential target genes affecting angiogenesis/arteriogenesis and contractility. The potential of micro RNA (miRNA) modulation for the de-repression of survival and pro-angiogenic genes is discussed. Since gene therapy of the target region is preferable to avoid systemic contamination, application routes are discussed.Expert opinion: miRNAs are a promising new development for successful gene therapy, especially for acute myocardial infarction since their miRNA antagonists are easy to apply and appear to be selectively absorbed by the ischemic myocardial tissue. Rapid uptake and prolonged presence of known antimirs and antagomirs support this notion. For ischemic heart disease the most promising gene therapeutic approach seems to be the regional intravenous application of suitable AAV vectors and vascular growth factors, providing the full scope of angiogenesis, vessel maturation and collateral growth optionally combined with genes enhancing contractility.

Endothelial progenitor cells (CD34+KDR+) and monocytes may provide the development of good coronary collaterals despite the vascular risk factors and extensive atherosclerosis

Endothelial progenitor cells (EPC) have a regenerative role in the vascular system. In this study, we aimed to evaluate simultaneously the effects of EPC and inflammatory cells on the presence and the extent of coronary artery disease (CAD) and the grade of coronary collateral growth in patients with clinical suspicion of CAD. This study has a cross-sectional and observational design. We enrolled 112 eligible patients who underwent coronary angiography consecutively (mean age: 59±9 years). The association of circulating inflammatory cells and EPC (defined by CD34+KDR+ in the lymphocyte and monocyte gate) with the presence, severity and extent of CAD and the degree of collateral growth were investigated. Logistic regression analysis was used to define the predictors of collateral flow. Of 112 patients 30 had normal coronary arteries (NCA, 27%, 55±9 years) and 82 had CAD (73%, 61±8 years). Among the patients with CAD, the percent degree of luminal stenosis was <50% in 12 patients; 50-90% in 35 patients; and ≥90% in the other 35 patients. Circulating inflammatory cells were higher (leukocytes, 7150±1599 vs 8163±1588 mm(-3), p=0.001; neutrophils, 4239±1280 vs 4827±1273 mm(-3), p=0.021; monocytes, 512±111 vs 636±192 mm(-3), p=0.001) and EPCs were lower (0.27±0.15% vs 0.17±0.14%, p<0.001; 21±15 vs 13±12 mm(-3), p=0.004) in CAD group than NCA group. When we investigated the collateral growth in patients having ≥90% stenosis in at least one major coronary artery, we found that the patients with good collateral growth had significantly higher EPC (0.22±0.17% vs 0.10±0.05%, p=0.009; 18±15 vs 7±3 mm(-3), p=0.003) in comparison to patients with poor collateral growth. Presence of EPC was associated with reduced risk for coronary artery disease (OR: 0.934, 95%CI: 0.883-0.998, p=0.018) and was an independent predictor for good collateral growth (OR: 1.295, 95%CI: 1.039-1.615, p=0.022). A sum of CD34+KDR-, CD34+KDR+ and CD34-KDR+ cells (192±98 mm(-3)), and a CD34-KDR- cell subpopulation within monocyte gate (514±173 mm(-3)) reached to highest counts in good collateral group among all study population. Endothelial progenitor cells can be mobilized from bone marrow to induce the coronary collateral growth in case of myocardial ischemia even in presence of the vascular risk factors and extensive atherosclerosis. This finding may be supportive to investigate the molecules, which can specifically mobilize EPC without inflammatory cells.