Early expression of angiogenesis factors in acute myocardial ischemia and infarction

Myocardial Gene Expression of Angiogenic Factors in Human Chronic Ischemic Myocardium: Influence of Acute Ischemia/Cardioplegia and Reperfusion

OBJECTIVE

Angiogenic therapies in animals have demonstrated the development of new blood vessels within ischemic myocardium. However, results from clinical protein and gene angiogenic trials have been less impressive. The present study aimed to investigate the expression of angiogenic genes in human chronic ischemic myocardium and the influence of acute ischemia/cardioplegia and reperfusion on their expression.

METHODS

Myocardial biopsies were taken from chronic ischemic and nonischemic myocardium in 15 patients with stable angina pectoris during coronary bypass surgery. Tissue samples were evaluated by oligonucleotide microarray and quantitative real-time PCR for the expression of angiogenic factors.

RESULTS

There was identical baseline expression of VEGF-A and VEGF-C mRNA in chronic ischemic myocardium compared with nonischemic myocardium. Reperfusion increased the gene expression of VEGF-A and VEGF-C mRNA both in nonischemic and ischemic myocardium. VEGF-A protein was detected mainly in the extracellular matrix around the cardiomyocytes in ischemic myocardium.

CONCLUSION

These data suggest that the nonconclusive VEGF gene therapy trials chronic coronary artery disease was not due to a preexisting upregulation of VEGF in chronic ischemic myocardium. There might be room for further therapeutic angiogenesis in chronic ischemic myocardium.

Endothelial-cardiomyocyte interactions in cardiac development and repair

Communication between endothelial cells and cardiomyocytes regulates not only early cardiac development but also adult cardiomyocyte function, including the contractile state. In the normal mammalian myocardium, each cardiomyocyte is surrounded by an intricate network of capillaries and is next to endothelial cells. Cardiomyocytes depend on endothelial cells not only for oxygenated blood supply but also for local protective signals that promote cardiomyocyte organization and survival. While endothelial cells direct cardiomyocytes, cardiomyocytes reciprocally secrete factors that impact endothelial cell function. Understanding how endothelial cells communicate with cardiomyocytes will be critical for cardiac regeneration, in which the ultimate goal is not simply to improve systolic function transiently but to establish new myocardium that is both structurally and functionally normal in the long term.

Immunohistochemical Expression of HIF-1alpha in Response to Early Myocardial Ischemia

This study aims to evaluate the effects of ischemia on the myocardial fibers and the expression of the transcriptional factor for angiogenesis hypoxia-inducible factor-1 alpha (HIF-1alpha) in human heart specimens. We have prospectively analyzed the HIF-1alpha expression in human ischemic hearts with the ABC-inmunohistochemistry technique and amplification by biotinylated tyramide. The relationship between the expression of HIF-1alpha and the temporal evolution of ischemia has also been evaluated. As pathomorphological diagnosis of early myocardial ischemia has many problems in human autopsy material with less than 4 to 6 h after clinical onset, we suggest that HIF-1alpha is helpful in the early acute myocardial infarction diagnosis, so it stains necrotic areas within the first 2 h. The amplification procedure provides a higher intensity of the final staining without losing specificity. It is concluded that in normal cardiac fibers, basal expression of HIF-1alpha is not appreciable, but it steadily increases after ischemia. With regard to the practical applicability in forensic field, our observations suggest that positive immunohistochemical expression of HIF-1alpha on heart samples may be used as a reliable indicator of myocardial damage in cases without cardiac lesion evidence, using conventional microscopy. This method is especially useful and may provide definitive proof of myocardial ischemia in unexpected deaths without previous symptoms, or in forensic cases with a short period of clinical manifestations. In addition, it may have been involved in possible future cardiovascular therapies.

Hypoxic regulation of VEGF, HIF-1(alpha) in coronary collaterals development

BACKGROUND

The interindividual variability for the development of collaterals in coronary artery disease is dependent on the hypoxic induction level of VEGF. To determine whether the hypoxic induction of VEGF is controlled by the transcription of HIF-1 (alpha), the VEGF and HIF-1 (alpha) m-RNA levels were correlated to hypoxia in monocytes harvested from patients with coronary artery disease.

METHODS

The collateral scoring system used was modified from the TIMI system. The mononuclear cell layer of the patients' blood was cultured in hypoxia (1% O2, 5% CO2, 94%N2) and normoxia (5% CO2, 95% room air) for 17 hours. The VEGF and HIF-1 (alpha) mRNA levels were measured using a RT-PCR technique. We calculated the fold inductionsof VEGF, HIF-1 (alpha) mRNA with hypoxia by dividing the hypoxic and the normoxic values.

RESULTS

We found significantly higher hypoxic inductions of VEGF m-RNA in patients with collaterals compared to patients with no collaterals. However, there was no differencein the hypoxic inductions of HIF-1 (alpha) between the two groups (VEGF m-RNA mean fold inductions 3.71 +/- 3.30 versus 1.65 +/- 0.62, p=0.012, HIF-1(alpha) mRNA 1.42 +/- 0.58 versus 1.20 +/- 0.39, p=0.165).

CONCLUSIONS

We concluded that the interindividual variability in the hypoxic inductions of VEGF m-RNA in monocytes in patients is not controlled by the transcriptional levels of HIF-1 (alpha) with hypoxia. These findings suggest that a mechanism such as the post-transcriptional modification of HIF-1(alpha) is involved in the hypoxic inductions of VEGF.

Differential Myocardial Infarct Repair with Muscle Stem Cells Compared to Myoblasts

Myoblast transplantation for cardiac repair has generated beneficial results in both animals and humans; however, poor viability and poor engraftment of myoblasts after implantation in vivo limit their regeneration capacity. We and others have identified and isolated a subpopulation of skeletal muscle-derived stem cells (MDSCs) that regenerate skeletal muscle more effectively than myoblasts. Here we report that in comparison with a myoblast population, MDSCs implanted into infarcted hearts displayed greater and more persistent engraftment, induced more neoangiogenesis through graft expression of vascular endothelial growth factor, prevented cardiac remodeling, and elicited significant improvements in cardiac function. MDSCs also exhibited a greater ability to resist oxidative stress-induced apoptosis compared to myoblasts, which may partially explain the improved engraftment of MDSCs. These findings indicate that MDSCs constitute an alternative to other myogenic cells for use in cardiac repair applications.

Differential myocardial gene delivery by recombinant serotype-specific adeno-associated viral vectors

Recombinant cross-packaging of adeno-associated virus (AAV) genome of one serotype into other AAV serotypes has the potential to optimize tissue-specific gene transduction and expression in the heart. To evaluate the role of AAV1 to 5 virion shells on AAV2 transgene transduction, we constructed hybrid vectors in which each serotype capsid coding domain was cloned into a common vector backbone containing AAV2 replication genes. Constructs were tested for expression in: (1) adult murine heart in vivo using direct injection of virus, (2) neonatal and adult murine ventricular cardiomyocytes in vitro, and (3) adult human ventricular cardiomyocytes in vitro, using green fluorescent protein (GFP) as the measurable transgene. Serotype 1 virus demonstrated the highest transduction efficiency in adult murine cardiomyocytes both in vitro and in vivo, while serotype 2 virus had the greater transduction efficiency in neonatal cardiomyocytes in vitro. Prolonged in vivo myocardial GFP expression was observed for up to 12 months using serotype 1 and 2 vectors only. In human cardiomyocytes, serotype 1 vector was superior in transduction efficiency, followed by types 2, 5, 4, and 3. These data establish a hierarchy for efficient serotype-specific vector transduction in myocardial tissue. AAV1 serotype packaging results in more efficient transduction of genes in the murine and human adult heart, compared to other AAV serotypes. Our results suggest that adult human cardiac gene therapy may be enhanced by the use of serotype 1-specific AAV vectors.

Gene expression profiles in hypoxic preconditioning using cDNA microarray analysis: altered expression of an angiogenic factor, carcinoembryonic antigen-related cell adhesion molecule 1

Hypoxic preconditioning has been shown to exhibit cardioprotective effects on myocardium from ischemic or reperfusion injury. The specific regulated gene involved in the hypoxia-induced cardioprotective effects is profiled in this study. Young male Wistar rats and ICR mice were exposed to sea level (as normal control) or simulated high altitude for 15 h/day for 2, 4, or 8 weeks, or for 4 weeks at high altitude after 2 weeks at sea level. The left ventricles of the animals were isolated for mRNA isolation and cDNA microarray analysis. Our data demonstrated that hypoxic preconditioning significantly ameliorated cardiac ischemic injury by minimizing the infarct size. After cluster analysis of expression profiles after different courses of hypoxic preconditioning (0, 2, 4, and 8 weeks), 386 genes showed an ascending pattern, whereas 301 genes showed a descending pattern. The ascending genes include several angiogenic factors: FGF receptor 4, vascular endothelial growth factor (vEGF), and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1). The microvessel density was also significantly increased in hypoxic hearts. Using Western blotting and immunohistochemical analysis, the protein expression level and localization of CEACAM-1 were observed in hypoxic myocardium. The results also indicated that CEACAM-1 was upregulated as with other hypoxic angiogenic factors, heme oxygenase 1 (HO-1) and hypoxia inducible factor-1alpha (HIF-1alpha), in in vitro cultured cardiomyocytes (H9c2) after hypoxia treatment and in vivo hypoxic preconditioning. Furthermore, incubation with recombinant vEGF could also increase the expression level of CEACAM-1 in H9c2 cells. These results demonstrated that hypoxic preconditioning resulted in transcriptional changes, and some of these genes have been correlated with angiogenesis. The HIF-1/vEGF/CEACAM-1 pathway might be important for hypoxia-induced angiogenesis in the heart during hypoxic preconditioning.

Skeletal muscle HIF-1alpha expression is dependent on muscle fiber type

Oxygen homeostasis is an essential regulation system for cell energy production and survival. The oxygen-sensitive subunit α of the hypoxia inducible factor-1 (HIF-1) complex is a key protein of this system. In this work, we analyzed mouse and rat HIF-1α protein and mRNA expression in parallel to energetic metabolism variations within skeletal muscle. Two physiological situations were studied using HIF-1α–specific Western blotting and semiquantitative RT-PCR. First, we compared HIF-1α expression between the predominantly oxidative soleus muscle and three predominantly glycolytic muscles. Second, HIF-1α expression was assessed in an energy metabolism switch model that was based on muscle disuse. These two in vivo situations were compared with the in vitro HIF-1α induction by CoCl₂ treatment on C₂C₁₂ mouse muscle cells. HIF-1α mRNA and protein levels were found to be constitutively higher in the more glycolytic muscles compared with the more oxidative muscles. Our results gave rise to the hypothesis that the oxygen homeostasis regulation system depends on the fiber type.

Norepinephrine but not hypoxia stimulates HIF-1alpha gene expression in brown adipocytes

The cellular response to hypoxic stress is mainly mediated via activation of the transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha). In the present study, the sympathetically controlled brown adipose tissue was used to investigate the effect of norepinephrine on HIF-1alpha gene expression. Norepinephrine increased HIF-1alpha mRNA levels in cultured brown adipocytes, whereas the hypoxia-mimic cobalt was without effect. Cold exposure of mice increased HIF-1alpha gene expression in brown adipose tissue. In UCP1-ablated mice, which are incapable of inducing thermogenic oxygen consumption in brown adipose tissue, cold exposure generated a significantly higher elevation of HIF-1alpha mRNA levels than in wild-type. These results demonstrate that cold-induced HIF-1alpha gene expression is independent of thermogenic oxygen consumption leading to hypoxia, but is consistent with a norepinephrine regulation of HIF-1alpha gene expression. Thus, by elevating HIF-1alpha gene expression, norepinephrine may mediate an increased potential to respond to hypoxia in brown adipose tissue and possibly in other tissues.

Hypoxia-inducible factor 1-alpha reduces infarction and attenuates progression of cardiac dysfunction after myocardial infarction in the mouse

OBJECTIVES

The aim of this research was to test whether constitutive expression of hypoxia-inducible factor 1-alpha (HIF-1alpha) influences infarction size and cardiac performance after myocardial infarction.

BACKGROUND

A major question in clinical medicine is whether infarction size and border zone remodeling of the heart can be influenced by the overexpression of specific genes in the peri-infarction region.

METHODS

We investigated the role of constitutive HIF-1alpha expression in acute myocardial infarction using a transgenic model. Transgenic mice containing the HIF-1alpha gene under the control of the alpha-myosin heavy chain promoter were constructed. Myocardial infarction was produced by coronary ligation in HIF-1alpha transgenic mice and control animals. Extent of infarction was then quantitated by two-dimensional and M-mode echocardiography as well as by molecular and pathologic analysis of heart samples in infarct, peri-infarct, and remote heart regions at serial time points.

RESULTS

Constitutive overexpression of HIF-1alpha in the murine heart resulted in attenuated infarct size and improved cardiac function 4 weeks after myocardial infarction. Significantly, we found an increase in both capillary density as well as vascular endothelial growth factor and inducible nitric oxide synthase expression in peri-infarct and infarct regions in the hearts of constitutive HIF-1alpha-expressing animals compared to control animals.

CONCLUSIONS

These observations suggest the involvement of HIF-1alpha in myocardial remodeling and peri-infarct vascularization. Our results show that supranormal amounts of this peptide protect against extension of infarction and improve border zone survival in myocardial infarction.

Mobilization of CD34+, CD117+, CXCR4+, c-met+ stem cells is correlated with left ventricular ejection fraction and plasma NT-proBNP levels in patients with acute myocardial infarction

AIMS

The aim of the study was to assess the correlation between the number of CD34(+), CD117(+), c-met(+), CXCR4(+) stem cells mobilized into peripheral blood, left ventricular ejection fraction (LVEF), NT-proBNP levels, and myocardial necrosis markers in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

43 patients with STEMI were enrolled. Stem cells number was measured using flow-cytometer and concentrations of NT-proBNP, SDF-1, G-CSF, VEGF, IL-6, and HGF were measured using ELISA kits. The number of stem cells mobilized early (<12 h) in AMI was significantly, positively correlated with LVEF: r=0.49 (P=0.0012) for CD34(+) cells, r=0.48 (P=0.0018) for CXCR4(+) cells, r=0.45 (P=0.0043) for CD117(+) cells, and r=0.41 (P=0.01) for c-met(+) cells and negatively correlated with NT-proBNP levels on admission r=-0.35 (P=0.024) for CD34(+) cells, r=-0.42 (P=0.007) for CXCR4(+) cells, r=-0.33 (P=0.04). In patients with LVEF </=40%, the peak number of CD34(+), CXCR4(+), CD117(+), and c-met(+) stem cells was significantly lower when compared patients with LVEF >40%. The number of CXCR4(+) cells on admission and after 24 h was negatively correlated with respective cardiac Troponin I levels (r=-0.37; P=0.029 and r=-0.45, P=0.02) and maximum activity of CK-MB (r=-0.37; P=0.021). No significant correlations between levels of haematopoietic cytokines and LVEF were found.

CONCLUSION

The mobilization of CD34(+), CD117(+), CXCR4(+), c-met(+) stem cells into peripheral blood early in STEMI is positively correlated with LVEF and negatively correlated with NT-proBNP levels and myocardial necrosis markers.

Identification of vascular progenitor cells in pulmonary arteries of patients with chronic obstructive pulmonary disease

Progenitor cells of bone marrow origin migrate to injured vessels, where they may contribute to endothelial maintenance and vessel remodeling through vascular endothelial growth factor (VEGF)-related signals. To what extent progenitor cells may play a role in vascular changes occurring in patients with chronic obstructive pulmonary disease (COPD) remains undetermined. In this study we sought to identify vascular progenitor cells in pulmonary arteries of patients with COPD and to investigate whether the presence of these cells could be related to changes in endothelial function or the expression of VEGF. Pulmonary arteries of nine patients with COPD and six control subjects were studied. Scanning electron microscopy demonstrated areas of denuded endothelium in the arteries of patients with COPD. Vascular progenitor cells were identified by immunohistochemistry and immunogold using antibodies against AC133, CD34, and CD45. AC133+ cells were localized in the endothelial surface, close to denuded areas. The number of AC133+ and CD45+ cells in pulmonary arteries was greater in patients with COPD than in control subjects. The number of AC133+ cells correlated with the response of pulmonary artery rings to hypoxic stimulus. AC133+ and CD45+ cells were also identified in the intimal layer. The wall thickness correlated with the number of progenitor cells in the intima and with VEGF and VEGF receptor-2 mRNA expression. We conclude that patients with COPD show an increased number of bone marrow-derived progenitor cells in pulmonary arteries. These cells seem to contribute to ongoing endothelial repair, but they might also be involved in the pathogenesis of pulmonary vascular remodeling.

Biomarkers in acute coronary syndromes and their role in diabetic patients

Diabetic patients with acute coronary syndromes are at high risk for cardiovascular complications but risk stratification in these patients remains challenging. Regularly, diabetic patients have a less typical clinical presentation, which could lead to delayed diagnosis and subsequent delayed initiation of treatment. Since diabetic patients derive particular benefit from aggressive anti-platelet therapy, early diagnostic and therapeutic risk stratification of these patients is of critical importance to improve their adverse outcome. Although the electrocardiogram remains a pivotal diagnostic tool in the evaluation of patients suspected of having an acute coronary syndrome, only significant ST-segment changes provide reasonable prognostic information. Therefore, repeated assessment of circulating protein biomarkers represents a valuable diagnostic tool for improving efficacy and safety of decision-making in these patients. The combined use of biomarkers reflecting distinct pathophysiological aspects, such as myocardial necrosis, vascular inflammation, oxidative stress and neurohumoral activation, may significantly improve triage of patients with chest pain. These tools may identify those patients that are at particularly high risk for short-term and/or long-term cardiovascular events. Eventually, tailored medical and interventional treatment of diabetic patients should help to prevent these cardiac events in a cost-effective manner.

Serum markers of angiogenesis and myocardial ultrasonic tissue characterization in patients with dilated cardiomyopathy

BACKGROUND AND AIMS

It has been proven that a disturbance in angiogenesis contributes to the progression of myocardial interstitial fibrosis in idiopathic dilated cardiomyopathy (DCM). This study was designed to evaluate the relationship between serum activity of angiogenic factors and myocardial ultrasonic tissue characterization in patients with DCM.

METHODS AND RESULTS

We studied 30 patients with DCM and 15 healthy control subjects. Serum levels of vascular endothelial growth factor (VEGF), interleukin (IL)-4 and IL-13 were measured using enzyme-linked immunosorbent assay. We determined calibrated myocardial integrated backscatter (IB) as the value of myocardial interstitial fibrosis using ultrasonic tissue characterization and also quantified the magnitude of cyclic variations in IB (CV-IB). Serum levels of VEGF and IL-13 were significantly higher in patients with DCM than in control subjects (both P<0.05). Calibrated IB was significantly higher and CV-IB was markedly lower in patients with DCM than in control subjects (both P<0.01). In patients with DCM, the levels of IL-13 significantly correlated with calibrated IB (r=0.520, P=0.018). In addition, there was a significant negative correlation between levels of VEGF and CV-IB (r=-0.611, P=0.007).

CONCLUSION

The increase in serum VEGF and IL-13 may be closely related to alterations in myocardial texture in DCM.

Vascular progenitor cells: origin and mechanisms of mobilization, differentiation, integration, and vasculogenesis

The recent discovery of progenitor cells in peripheral blood that can differentiate into endothelial or vascular smooth muscle cells has led to the re-evaluation of many traditionally held beliefs about vascular biology. Most notably, concepts of vascular regeneration and repair, previously considered limited to the proliferation of existing differentiated cells within vascular tissue, have been expanded to include the potential for postnatal vasculogenesis. These cells have since been identified in the bone marrow, heart, skeletal muscle, and other peripheral tissues, including the vasculature itself. The significance of these cells lies not only in developing our understanding of normal vascular biology, but also in the insights they may provide into vascular diseases such as atherosclerosis. In addition, a potential role in therapeutics has already been explored in early clinical trials in humans. The mechanisms underlying the mobilization, target tissue integration, differentiation, and the observed therapeutic benefits of these cells are now being elucidated. It is these mechanisms, and the current understanding of the lineage of these cells, that constitutes the focus of this review.

Endogenous G-CSF and CD34+ cell mobilization after acute myocardial infarction

BACKGROUND

Several reports showed an increase of CD34(+) stem/progenitor cell count early after an acute myocardial infarction (AMI), suggesting a contribution of bone marrow cells in myocardial regeneration after the acute event. Nevertheless, at present plasma mediators of CD34(+) cell mobilization from bone marrow to peripheral blood in patients with AMI are poorly understood. Aim of our study was to establish the impact of different well-known mobilizing cytokines on spontaneous stem cell mobilization in patients with different ischemic heart syndromes, such as the AMI and the chronic stable angina (CSA), compared to healthy controls.

METHODS

In 16 patients with AMI, 18 with CSA and 22 healthy blood donors the concentration of CD34(+) cells, and mobilizing cyokines (G-CSF, SCF, VEGF, SDF1-alpha) were assessed.

RESULTS

The peak number of circulating CD34(+) cells in AMI patients (8.58+/-2.08 cells/microl) was higher than that observed in patients with CSA (3.41+/-0.56 cells/microl, p=0.0061) or in healthy controls (2.18+/-0.35 cells/microl, p<0.001). However endogenous G-CSF was significantly higher in the serum of patients with AMI compared to CSA patients and to controls and in CSA patients compared to controls. Interestingly, as regards VEGF, while this cytokine was increased in AMI with respect to control and CSA group, the latter showed a significantly lower concentration with respect to controls. Finally SDF-1 alpha was higher in AMI patients with respect to controls. CD34(+) cells were significantly correlated to G-CSF (directly) and to SCF (inversely) in patients with AMI.

CONCLUSION

In the present study, we have demonstrated for the first time that the spontaneous mobilization of CD34(+) cells into the peripheral blood of patients with AMI is significantly correlated to endogenous G-CSF. Considering recent data suggesting a potential favourable effect of circulating CD34(+) cells on left ventricular function, the present evidence of a correlation between endogenous G-CSF and CD34(+) cell levels supports the pharmacological administration of G-CSF as a non-invasive option for regeneration of myocardial tissue after AMI.

Carvedilol modulates the expression of hypoxia-inducible factor-1alpha and vascular endothelial growth factor in a rat model of volume-overload heart failure

BACKGROUND

The use of beta-blockers has emerged as a beneficial treatment for congestive heart failure. Hypoxia-inducible factor-1alpha (HIF-1alpha) is tightly regulated in the ventricular myocardium. However, the expression of HIF-1alpha in chronic heart failure resulting from volume overload and after treatment with beta-blocker is little known.

METHODS AND RESULTS

To test the hypothesis that HIF-1alpha plays a role in the failing myocardium because of volume overload, an aorta-caval shunt was created for 4 weeks in adult Sprague-Dawley rats to induce volume-overload heart failure. Carvedilol at 50 mg/kg body weight per day after surgery was given. The heart weight and body weight ratio increased from 2.6 +/- 0.3 in the sham group to 3.9 +/- 0.7 (P < .001) in the shunt group. Left ventricular end-diastolic dimension increased from 6.5 +/- 0.5 mm to 8.7 +/- 0.6 mm (P < .001). Treatment with carvedilol in the shunt group reversed the heart weight and ventricular dimension to the baseline values. Western blot showed that HIF-1alpha, vascular endothelial growth factor (VEGF), and brain natriuretic peptide (BNP) proteins were upregulated and nerve growth factor-beta (NGF-beta) downregulated in the shunt group. Real-time polymerase chain reaction showed that mRNA of HIF-1alpha, VEGF, and BNP increased and mRNA of NGF-beta decreased in the shunt group. Treatment with carvedilol reversed both protein and mRNA of HIF-1alpha, VEGF, BNP, and NGF-beta to the baseline values. Increased immunohistochemical labeling of HIF-1alpha, VEGF, and BNP in the ventricular myocardium was observed in the shunt group and carvedilol again normalized the labeling.

CONCLUSION

HIF-1alpha and VEGF mRNA and protein expression were upregulated in the rat model of volume-overload heart failure. Treatment with carvedilol is associated with a reversal of abnormal regulation of HIF-1alpha and VEGF in the failing ventricular myocardium.

Effects of exercise and ischemia on mobilization and functional activation of blood-derived progenitor cells in patients with ischemic syndromes: results of 3 randomized studies

BACKGROUND

Exercise training (ET) has been shown to improve regional perfusion in ischemic syndromes. This might be partially related to a regeneration of diseased endothelium by circulating progenitor cells (CPCs) or CPC-derived vasculogenesis. The aim of the present study was to determine whether ischemic stimuli during ET are required to promote CPC mobilization in patients with cardiovascular diseases.

METHODS AND RESULTS

Patients with peripheral arterial occlusive disease (PAOD) were randomized to 4 weeks of daily ischemic ET or control (group A). Successfully revascularized patients with PAOD were randomized to 4 weeks of daily nonischemic ET or control (group B). Patients with stable coronary artery disease were subjected to 4 weeks of subischemic ET or control (group C). At baseline and after 4 weeks, the number of KDR+/CD34+ CPCs was determined by fluorescence-activated cell sorting analysis. Levels of vascular endothelial growth factor (VEGF) were measured by ELISA. A Matrigel assay was used to quantify CPC integration into vascular structures. Expression of the homing factor CXCR4 was determined by reverse transcription-polymerase chain reaction. In group A only, ischemic ET increased VEGF levels by 310% (P<0.05 versus control) associated with an increase in CPCs by 440% (P<0.05 versus control), increased CXCR4 expression, and enhanced integration of CPCs into endothelial networks. In contrast, subischemic ET in groups B and C increased CXCR4 expression and CPC integration.

CONCLUSIONS

In training programs, symptomatic tissue ischemia seems to be a prerequisite for CPC mobilization. However, ischemic and subischemic ET programs affect CXCR4 expression of CPCs, which might lead to an improved CPC integration into endothelial networks.

Oxygen, oxidative stress, hypoxia, and heart failure

A constant supply of oxygen is indispensable for cardiac viability and function. However, the role of oxygen and oxygen-associated processes in the heart is complex, and they and can be either beneficial or contribute to cardiac dysfunction and death. As oxygen is a major determinant of cardiac gene expression, and a critical participant in the formation of ROS and numerous other cellular processes, consideration of its role in the heart is essential in understanding the pathogenesis of cardiac dysfunction.

Unchain my heart: the scientific foundations of cardiac repair

In humans, the biological limitations to cardiac regenerative growth create both a clinical imperative--to offset cell death in acute ischemic injury and chronic heart failure--and a clinical opportunity; that is, for using cells, genes, and proteins to rescue cardiac muscle cell number or in other ways promote more efficacious cardiac repair. Recent experimental studies and early-phase clinical trials lend credence to the visionary goal of enhancing cardiac repair as an achievable therapeutic target.

Oxygen, oxidative stress, hypoxia, and heart failure

A constant supply of oxygen is indispensable for cardiac viability and function. However, the role of oxygen and oxygen-associated processes in the heart is complex, and they and can be either beneficial or contribute to cardiac dysfunction and death. As oxygen is a major determinant of cardiac gene expression, and a critical participant in the formation of ROS and numerous other cellular processes, consideration of its role in the heart is essential in understanding the pathogenesis of cardiac dysfunction.

Serum deoxyribonuclease I activity can be used as a sensitive marker for detection of transient myocardial ischaemia induced by percutaneous coronary intervention

AIMS

Cardiac markers such as troponin T (c-TnT) have proven unsuitable for the detection of early and transient myocardial ischaemia. We recently reported that abrupt elevation of serum deoxyribonuclease I (DNase I) activity in the early stage of acute myocardial infarction could be used as a diagnostic marker. To evaluate whether serum DNase I could be used as a marker of early myocardial ischaemia, we investigated alterations in its levels after transient ischaemia induced during percutaneous coronary intervention (PCI).

METHODS AND RESULTS

In 24 consecutive patients with stable angina undergoing elective PCI and 12 patients undergoing coronary angiography (CAG), serum samples were tested for DNase I, creatine kinase isoenzyme MB (CK-MB), and c-TnT before, soon after, and 3 and 12-24 h after completion of the procedures. Serum DNase I activity had risen significantly from baseline by 3 h after PCI in 21 of the 24 PCI patients. The mean per cent difference from baseline in serum DNase I activity 3 h after PCI was 35.9+/-37.5%. Even among the 16 PCI patients whose levels of CK-MB and c-TnT were within the normal range, 13 showed elevation of serum DNase I activity from baseline after PCI. In the CAG patient group, DNase I activity levels remained unchanged at all times after CAG.

CONCLUSION

Elevation of serum DNase I activity can be used as a sensitive marker for detection of transient myocardial ischaemia.

Physiological activation of hypoxia inducible factor-1 in human skeletal muscle

The human hypoxia inducible factor 1 (HIF-1) system is activated under various pathological conditions, yet less is known about its physiological regulation in healthy human tissue. We have studied the effect of exercise on the activation of HIF-1 in human skeletal muscle. Employing a model where oxygen consumption increases and oxygen tension can be manipulated, nine healthy male subjects performed 45 min of one-legged knee-extension exercise. Biopsies were taken before, directly after, and 30, 120, and 360 min after exercise. Exercise led to elevated HIF-1alpha protein levels and a more prevalent nuclear staining of HIF-1alpha. Interestingly, a concurrent decrease in von Hippel-Lindau tumor suppressor protein (VHL) levels was detected in some subjects. Moreover, exercise induced an increase in the DNA binding activity of HIF-1alpha. Characterization of gene expression by real-time PCR demonstrated that the HIF-1 target genes VEGF and EPO were activated. VEGF mRNA was further increased when blood flow to the exercising leg was restricted. In conclusion, these data clearly demonstrate that physical activity induces the HIF-1-mediated signaling pathway in human skeletal muscle, providing the first evidence that human HIF-1alpha can be activated during physiologically relevant conditions.

Adaptive myogenesis under hypoxia

Previous studies have indicated that myoblasts can differentiate and repair muscle injury after an ischemic insult. However, it is unclear how hypoxia or glucose deprivation in the ischemic microenvironment affects myoblast differentiation. We have found that myogenesis can adapt to hypoxic conditions. This adaptive mechanism is accompanied by initial inhibition of the myoD, E2A, and myogenin genes followed by resumption of their expression in an oxygen-dependent manner. The regulation of myoD transcription by hypoxia is correlated with transient deacetylation of histones associated with the myoD promoter. It is noteworthy that, unlike the differentiation of other cell types such as preadipocytes or chondroblasts, the effect of hypoxia on myogenesis is independent of HIF-1, a ubiquitous regulator of transcription under hypoxia. While myogenesis can also adapt to glucose deprivation, the combination of severe hypoxia and glucose deprivation found in an ischemic environment results in pronounced loss of myoblasts. Our studies indicate that the ischemic muscle can be repaired via the adaptive differentiation of myogenic precursors, which depends on the levels of oxygen and glucose in the ischemic microenvironment.

Hypoxia inducible factor-1 expression mediates myocardial response to ischemia late after acute myocardial infarction

We report hypoxia-inducible factor-1 (HIF-1) expression in myocardium of patients with recent acute myocardial infarction (AMI), supporting the hypothesis of HIF-1 as a possible mediator of response to ischemia. A potential diagnostic role of determining tissue expression of HIF-1 as a marker of ischemia, and potential therapeutic implications by trying to modulate HIF-1 activity in order to promote beneficial effects of HIF-1 related genes (e.g. expression of vascular endothelial growth factor (VEGF)) may derive.

Endothelial progenitor cells: characterization and role in vascular biology

Infusion of different hematopoietic stem cell populations and ex vivo expanded endothelial progenitor cells augments neovascularization of tissue after ischemia and contributes to reendothelialization after endothelial injury, thereby, providing a novel therapeutic option. However, controversy exists with respect to the identification and the origin of endothelial progenitor cells. Overall, there is consensus that endothelial progenitor cells can derive from the bone marrow and that CD133/VEGFR2 cells represent a population with endothelial progenitor capacity. However, increasing evidence suggests that there are additional bone marrow-derived cell populations (eg, myeloid cells, "side population" cells, and mesenchymal cells) and non-bone marrow-derived cells, which also can give rise to endothelial cells. The characterization of the different progenitor cell populations and their functional properties are discussed. Mobilization and endothelial progenitor cell-mediated neovascularization is critically regulated. Stimulatory (eg, statins and exercise) or inhibitory factors (risk factors for coronary artery disease) modulate progenitor cell levels and, thereby, affect the vascular repair capacity. Moreover, recruitment and incorporation of endothelial progenitor cells requires a coordinated sequence of multistep adhesive and signaling events including adhesion and migration (eg, by integrins), chemoattraction (eg, by SDF-1/CXCR4), and finally the differentiation to endothelial cells. This review summarizes the mechanisms regulating endothelial progenitor cell-mediated neovascularization and reendothelialization.

Protein-, gene-, and cell-based therapeutic angiogenesis for the treatment of myocardial ischemia

Therapeutic angiogenesis aims at restoring perfusion to chronically ischemic myocardial territories by using growth factors or cells, without intervening on the epicardial coronary arteries. Despite angiogenesis having received considerable scientific attention over the last decade, it has not yet been shown to provide clinical benefit and is still reserved for patients who have failed conventional therapies. Nevertheless, angiogenesis is a very potent physiologic process involved in the growth and development of every animal and human, and it is likely that its use for therapeutic purposes, once its underlying mechanistic basis is better understood, will one day become an important modality for patients with CAD and other types of organ ischemia. This review summarizes current knowledge in therapeutic angiogenesis research.

Endothelium and angiogenesis in white coat hypertension

Hypertensive patients are at particular risk of cardiovascular complications, possibly related to endothelial damage or dysfunction, or to abnormal angiogenesis. The aim of this study was to compare the risk conferred by white coat hypertension (WCH) vs sustained hypertension in the development of the endothelial dysfunction and abnormal angiogenesis by evaluating nitric oxide (NO=NO2+NO3), endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and E-selectin levels in plasma. The study group included 102 subjects, 34 with WCH (17 male and 17 female patients) aged 49+/-11 years, 34 sustained hypertensives (HT) (15 male and 19 female patients) aged 47+/-11 years and 34 normotensive control subjects (NT) (16 male and 18 female patients) aged 48+/-10 years. WCH was defined as clinical hypertension and daytime ambulatory blood pressure less than 135/85 mmHg. The subjects were matched for age, gender, body mass index and the patients with smoking habit, dyslipidaemia, and diabetes mellitus were excluded from the study. The NO, ET-1, VEGF and E-selectin levels were analysed by ELISA technique. The WCH subjects had significantly higher levels of NO than the HT (41.68+/-2.23 vs 32.18+/-2.68 micromol/l; P<0.001) and significantly lower values than the NT (48.24+/-4.29 micromol/l; P<0.001). ET-1 levels of the WCH group were significantly higher than the NT (8.10+/-0.92 vs 5.95+/-0.26 ng/ml; P<0.001) and significantly lower than the HT (11.46+/-0.59 ng/ml; P<0.001). Considering with VEGF, the WCH group had significantly higher levels than the NT (195.88+/-11.84 vs 146.26+/-18.67 pg/ml; P<0.001), but the difference from the HT group was not significant (203.35+/-7.48 pg/ml; P=0.062). E-selectin in the WCH group was significantly lower than the HT (4.77+/-0.52 vs 8.49+/-2.85; P<0.001), but the difference from the NT group was not significant (3.86+/-0.67; P=0.077). Our data demonstrate that WCH is associated with endothelial dysfunction and abnormal angiogenesis. The degree of these changes is not as severe as observed in hypertensive population.

Clinical Applications of Stem Cells for the Heart

Repair of the heart is an old dream of physicians caring for patients with cardiac disease. Experimental studies suggest that cardiac transfer of stem and progenitor cells can have a favorable impact on tissue perfusion and contractile performance of the injured heart. Some researchers favor stable stem cell engraftment by fusion or transdifferentiation into cardiomyocyte or vascular cell lineages as likely explanations for these beneficial effects. Others have proposed that transient cell retention may be sufficient to promote functional effects, eg, by release of paracrine mediators. Although the mechanistic underpinnings of stem cell therapy are still intensely debated, the concept of cell therapy has already been introduced into the clinical setting, where a flurry of small, mostly uncontrolled trials indicate that stem cell therapy may be feasible in patients. The overall clinical experience also suggests that stem cell therapy can be safely performed, if the right cell type is used in the right clinical setting. Preliminary efficacy data indicate that stem cells have the potential to enhance myocardial perfusion and/or contractile performance in patients with acute myocardial infarction, advanced coronary artery disease, and chronic heart failure. The field now is rapidly moving toward intermediate-size, double-blinded trials to gather more safety and efficacy data. Ultimately, large outcome trials will have to be conducted. We need to proceed cautiously with carefully designed clinical trials and keep in mind that patient safety must remain the key concern. At the same time, continued basic research to elucidate the underlying mechanism of stem cell therapy is clearly needed.

Diabetic cardiomyopathy: mechanisms, diagnosis and treatment

Independent of the severity of coronary artery disease, diabetic patients have an increased risk of developing heart failure. This clinical entity has been considered to be a distinct disease process referred to as 'diabetic cardiomyopathy'. Experimental studies suggest that extensive metabolic perturbations may underlie both functional and structural alterations of the diabetic myocardium. Translational studies are, however, limited and only partly explain why diabetic patients are at increased risk of cardiomyopathy and heart failure. Although a range of diagnostic methods may help to characterize alterations in cardiac function in general, none are specific for the alterations in diabetes. Treatment paradigms are very much limited to interpretation and translation from the results of interventions in non-diabetic patients with heart failure. This suggests that there is an urgent need to conduct pathogenetic, diagnostic and therapeutic studies specifically in diabetic patients with cardiomyopathy to better understand the factors which initiate and progress diabetic cardiomyopathy and to develop more effective treatments.

Idiopathic benign biliary strictures in surgically resected patients with presumed cholangiocarcinoma

OBJECTIVE

Distinguishing between malignant and benign biliary strictures remains problematic. The aim of this study was to compare and contrast the clinical features of patients with benign and malignant biliary strictures.

METHODS

Medical records of patients who underwent surgical resection for presumed cholangiocarcinoma were reviewed. Immunohistochemistry for hypoxia inducible factor-1-alpha (HIF-1-alpha) was performed on all bile ductule samples.

RESULTS

Twelve patients with benign strictures (group I) were compared to 26 patients with cholangiocarcinoma (group II). Group I was predominantly female (ratio 2: 1), (p<0.01), whereas the gender ratio was 1: 1 in patients in group II. Bismuth-Corlette type strictures in group I were more likely to be type I/II, whereas type III strictures predominated in group II. The CA 19-9 was <100 U/ml in 6 and >100 U/ml in 1 patient of group I and <100 in 13 and >100 in 11 patients in group II. Half of the patients in group I had positive immunoreactivity for HIF-1-alpha in bile ductules.

CONCLUSION

Benign biliary strictures masquerading as cholangiocarcinomas occur more often in women, are less often Bismuth-Corlette type III, have serum CA 19-9 values <100 U/ml, and hypoxia may play a role in a subset of these strictures.

Vascular endothelial growth factor and angiogenesis

Angiogenesis is a hallmark of wound healing, the menstrual cycle, cancer, and various ischemic and inflammatory diseases. A rich variety of pro- and antiangiogenic molecules have already been discovered. Vascular endothelial growth factor (VEGF) is an interesting inducer of angiogenesis and lymphangiogenesis, because it is a highly specific mitogen for endothelial cells. Signal transduction involves binding to tyrosine kinase receptors and results in endothelial cell proliferation, migration, and new vessel formation. In this article, the role of VEGF in physiological and pathological processes is reviewed. We also discuss how modulation of VEGF expression creates new therapeutic possibilities and describe recent developments in this field.

Mobilization of CD34/CXCR4+, CD34/CD117+, c-met+ stem cells, and mononuclear cells expressing early cardiac, muscle, and endothelial markers into peripheral blood in patients with acute myocardial infarction

BACKGROUND

Adult stem cells can contribute to myocardial regeneration after ischemic injury. Bone marrow and skeletal muscles contain a population of CXCR4+ cells expressing genes specific for muscle progenitor cells that can be mobilized into the peripheral blood. The aims of the study were (1) to confirm the presence of early tissue-committed cells expressing cardiac, muscle, and endothelial markers in populations of mononuclear cells in peripheral blood and (2) to assess the dynamics and magnitude of the mobilization of CD34+, CD117+, CXCR4+, c-met+, CD34/CD117+, and CD34/CXCR4+ stem cells into peripheral blood in relation to inflammatory and hematopoietic cytokines in patients with ST-segment-elevation acute myocardial infarction (STEMI).

METHODS AND RESULTS

Fifty-six patients with STEMI (<12 hours), 39 with stable angina, and 20 healthy control subjects were enrolled. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was used for detection of tissue-specific markers. The number of the cells was assessed by use of a flow cytometer on admission, after 24 hours, and after 7 days. RT-PCR revealed increased expression of mRNA (up to 3.5-fold increase) for specific cardiac (GATA4, MEF2C, Nkx2.5/Csx), muscle (Myf5, Myogenin, MyoD), and endothelial (VE-cadherin, von Willebrand factor) markers in peripheral blood mononuclear cells. The number of CD34/CXCR4+ and CD34/CD117+ and c-met+ stem cells in peripheral blood was significantly higher in STEMI patients than in stable angina and healthy subjects, peaking on admission, without further significant increase after 24 hours and 7 days.

CONCLUSIONS

The study demonstrates in the setting of STEMI a marked mobilization of mononuclear cells expressing specific cardiac, muscle, and endothelial markers as well as CD34/CXCR4+ and CD34/CD117+ and c-met+ stem cells and shows that stromal cell-derived factor-1 is an important factor influencing the mobilization.

Growth Factors in the Collateral Circulation of Chronic Total Coronary Occlusions

Background— Despite extensive animal experimental evidence, there are few data on the relation of growth factors and collateral function in humans.

Methods and Results— In 104 patients with a chronic total coronary occlusion (CTO; >2 weeks’ duration), collateral function was assessed invasively during recanalization by intracoronary Doppler and pressure recordings. A collateral resistance index, R Coll , was calculated. Blood samples were drawn from the distal coronary bed supplied by the collaterals and from the aortic root to measure basic fibroblast growth factor (bFGF), monocytic chemotactic protein-1 (MCP-1), transforming growth factor-β (TGF-β), placenta growth factor (PlGF), and tumor necrosis factor-α (TNF-α). The bFGF concentration in the collateralized artery was higher than in the aortic root (34±20 versus 18±14 pg/mL; P <0.001). bFGF was highest in recent occlusions (2 to 12 weeks) with the highest R Coll . Higher collateral concentrations were also observed for MCP-1, TGF-β, and PlGF, but without a close relation to the duration of occlusion. TNF-α was not increased in collaterals compared with the systemic circulation. MCP-1, PlGF, and TGF-β were significantly increased in small collaterals with the highest shear stress. Diabetic patients had lower bFGF and higher MCP-1 levels than nondiabetics.

Conclusions— In CTOs, the continuous release of bFGF into collaterals showed a close relation to the duration of occlusion and collateral function, which underscores its therapeutic potential. Other factors influencing growth factor release appeared to be shear stress for MCP-1, TGF-β, and PlGF and the presence of diabetes.

Endothelium-Targeted Gene and Cell-Based Therapies for Cardiovascular Disease

Most common cardiovascular diseases are accompanied by endothelial dysfunction. Because of its predominant role in the pathogenesis of cardiovascular disease, the vascular endothelium is an attractive therapeutic target. The identification of promoter sequences capable of rendering endothelial-specific transgene expression together with the recent development of vectors with enhanced tropism for endothelium may offer opportunities for the design of new strategies for modulation of endothelial function. Such strategies may be useful in the treatment of chronic diseases such as hypertension, atherosclerosis, and ischemic artery disease, as well as in acute myocardial infarction and during open heart surgery for prevention of ischemia and reperfusion (I/R)-induced injury. The recent identification of putative endothelial progenitor cells in peripheral blood may allow the design of autologous cell-based strategies for neovascularization of ischemic tissues and for the repair of injured blood vessels and bioengineering of vascular prosthesis. "Proof-of-concept" for some of these strategies has been established in animal models of cardiovascular disease. However the successful translation of these novel strategies into clinical application will require further developments in vector and delivery technologies. Further characterization of the processes involved in mobilization, migration, homing, and incorporation of endothelial progenitor cells into the target tissues is necessary, and the optimal conditions for therapeutic application of these cells need to be defined and standardized.

Expression of angiogenic factors during acute coronary syndromes in human type 2 diabetes

Inadequate angiogenic response to ischemia in diabetic myocardium could result in poor collateral formation. Because hypoxia-inducible factor (HIF)-1alpha is a transcriptional activator of vascular endothelial growth factor (VEGF) and is critical for initiating angiogenic responses to hypoxia, we investigated the expression of HIF-1alpha and VEGF in specimens of human heart tissue to elucidate the molecular responses to myocardial ischemia in diabetic patients during unstable angina. Moreover, accumulation of a marker of protein nitration nitrotyrosine, as well as the superoxide anion (O(2)(-)) levels and inducible nitric oxide synthase (iNOS), were evaluated. Ventricular biopsy specimens from 15 type 2 diabetic and 14 nondiabetic patients presenting with unstable angina (ischemic group) and from 20 patients (11 type 2 diabetic and 9 nondiabetic patients) who underwent coronary bypass surgery without angina within the preceding 10 days (control group) were collected during coronary bypass surgery. Nondiabetic patients had higher HIF-1alpha and VEGF expressions compared with diabetic patients (P < 0.001). As compared with nondiabetic specimens, diabetic specimens showed higher levels of both iNOS mRNA and protein levels (P < 0.001) associated with the highest tissue levels of nitrotyrosine and O(2)(-) (P < 0.001). Diabetes is associated with increased myocardial tissue levels of iNOS, O(2)(-), and nitrotyrosine and reduced expression of myocardial angiogenesis factors during ischemia.

ANP and BNP but not VEGF are regionally overexpressed in ischemic human myocardium

Angiogenic gene therapy in angina pectoris has been disappointing so far. Reasons might be that the administered genes already are overexpressed in ischemic myocardium, or that atrial and brain natriuretic peptides (ANP and BNP) are overexpressed, as they have anti-angiogenic effects. Five stable angina pectoris patients without heart failure were studied. Left ventricular biopsies were taken during coronary by-pass surgery from a region with stress-inducible ischemia and from a normal region. Both ANP and BNP but not vascular endothelial growth factor (VEGF) and VEGF-receptor 1 and 2 were overexpressed in ischemic regions compared to non-ischemic regions as measured by real-time PCR. The expression of 15 other angiogenic genes measured by oligonucleotide arrays was not consistently increased in ischemic regions. The overexpression of ANP and BNP suggests an anti-angiogenic effect in ischemic heart disease. The lack of overexpression of angiogenic genes supports the concept of therapeutic overexpression of these genes.

Plasma angiopoietin-1, angiopoietin-2, angiopoietin receptor tie-2, and vascular endothelial growth factor levels in acute coronary syndromes

BACKGROUND

Angiopoietin (Ang) -1 and -2, their receptor Tie-2, and vascular endothelial growth factor (VEGF) regulate angiogenesis and may be important in myocardial collateral development. Elevated levels of growth factors and their receptors are reported in myocardial infarction (MI), but changes after an acute coronary event are unknown.

METHODS AND RESULTS

Plasma Ang-1, Ang-2, Tie-2, and VEGF levels were measured on admission (baseline) and at 48 hours (acute stage) in 126 patients with acute coronary syndrome (82 MI, 44 unstable angina pectoris). Baseline levels were compared with those of 40 patients with stable angina and 40 healthy controls. Measurements were repeated in 38 MI patients at 6 and 18 weeks (chronic stage). Baseline Ang-2 and Tie-2 levels were highest in MI patients (P<0.001). Patients with MI and unstable angina pectoris had higher VEGF levels compared with stable angina patients and healthy control subjects (P<0.001). In patients with acute MI, serial changes in all indexes from baseline to 18 weeks were observed (all P<0.001). Ang-1 levels were unchanged from baseline to 6 weeks but were elevated at 18 weeks. Ang-2 changes followed a biphasic pattern, being higher at baseline and 6 weeks but lower at 48 hours and 18 weeks. Tie-2 levels increased from baseline and remained elevated in the chronic phase. VEGF peaked at 6 weeks and then decreased toward baseline at 18 weeks.

CONCLUSIONS

Plasma Ang-2, Tie-2, and VEGF levels but not Ang-1 levels were increased in patients with acute coronary syndrome. Serial changes in the plasma levels and interrelationships among Ang-1, Ang-2, Tie-2, and VEGF levels from the acute to the chronic stages in MI may reflect the progressive stages of angiogenesis activity in the ischemic-necrotic myocardium in vivo.

Persistent induction of HIF-1alpha and -2alpha in cardiomyocytes and stromal cells of ischemic myocardium

Hypoxia-inducible factor (HIF)-1alpha and -2alpha are key regulators of the transcriptional response to hypoxia and pivotal in mediating the consequences of many disease states. In the present work, we define their temporo-spatial accumulation after myocardial infarction and systemic hypoxia. Rats were exposed to hypoxia or underwent coronary artery ligation. Immunohistochemistry was used for detection of HIF-1alpha and -2alpha proteins and target genes, and mRNA levels were determined by RNase protection. Marked nuclear accumulation of HIF-1alpha and -2alpha occurred after both systemic hypoxia and coronary ligation in cardiomyocytes as well as interstitial and endothelial cells (EC) without pronounced changes in HIF mRNA levels. While systemic hypoxia led to widespread induction of HIF, expression after coronary occlusion occurred primarily at the border of infarcted tissue. This expression persisted for 4 wk, included infiltrating macrophages, and colocalized with target gene expression. Subsets of cells simultaneously expressed both HIF-alpha subunits, but EC more frequently induced HIF-2alpha. A progressive increase of HIF-2alpha but not HIF-1alpha occurred in areas remote from the infarct, including the interventricular septum. Cardiomyocytes and cardiac stromal cells exhibit a marked potential for a prolonged transcriptional response to ischemia mediated by HIF. The induction of HIF-1alpha and -2alpha appears to be complementary rather than solely redundant.

Surgery and angiogenesis

Surgery may be regarded as an angiogenesis-inducing condition since it evokes the release of many angiogenic factors. Regarding the mechanistic overlap between tumor-associated neovascularisation and (physiological) angiogenesis in response to injury and hypoxia, surgery may promote the uncontrolled growth of residual dormant tumor cells. With the advent of anti-angiogenic agents, surgeons will be faced with more patients undergoing surgery for primary and secondary tumors under anti-angiogenic treatment. This could present problems with regard to angiogenesis-dependent phenomena such as wound repair, healing of intestinal anastomoses and liver regeneration. In this review we will discuss these matters from a biomedical and clinical point of view.

Inflammatory Cytokines and Postmyocardial Infarction Remodeling

Inflammatory response and cytokine elaboration are particularly active after myocardial infarction and contribute to cardiac remodeling and eventual host outcome. The triggers of cytokine release in the acute postinfarction period include mechanical deformation, ischemic stimulus, reactive oxygen species (ROS), and cytokine self-amplification pathways. Acutely, the elaboration of tumor necrosis factor, IL-1 and IL-6, transforming growth factor families of cytokines, contribute to survival or deaths of myocytes, modulation of cardiac contractility, alterations of vascular endothelium, and recruitment of additional circulating cells of inflammation to the injured myocardium. This leads to further local oxidative stress and remodeling but also initiates the processes of wound healing. Chronically, sustained presence of cytokines leads to myocyte phenotype transition and activation of matrix metalloproteinases that modifies interstitial matrix, augmenting further the remodeling process. This in turn alters the local collagen composition and also the integrins that constitute the interface between myocytes and the matrix. These processes ultimately, when favorable, pave the way for angiogenesis and cellular regeneration. Thus, the insightful modulation of cytokines through current and future therapies could promote improved healing and cardiac remodeling postmyocardial infarction.

Hypoxia-inducible factor 1 (HIF-1) in cancer

Hypoxia is a common feature of many cancers. It contributes to local and systemic tumour progression as well as potentially compromising radiotherapy and chemotherapy. Hypoxia-inducible factor 1 (HIF-1) is an essential component in changing the transcriptional response of tumours under hypoxia. It targets the transcription of over 60 genes involved in many aspects of cancer biology including cell survival, glucose metabolism, cell invasion and angiogenesis. Over-expression of HIF-1 has been associated with increased patient mortality in several cancer types including breast, stomach, cervical, endometrial and ovarian cancers. The pharmacological manipulation of HIF-1 has marked effects on tumour growth, and it could prove to be an important target for drug therapy, both in cancer and in other hypoxia-dependent disease states.

Cardiac myocyte-specific HIF-1alpha deletion alters vascularization, energy availability, calcium flux, and contractility in the normoxic heart

At a resting pulse rate the heart consumes almost twice-as much oxygen per gram tissue as the brain and more than 43 times more than resting skeletal muscle (1). Unlike skeletal muscle, cardiac muscle cannot sustain anaerobic metabolism. Balancing oxygen demand with availability is crucial to cardiac function and survival, and regulated gene expression is a critical element of maintaining this balance. We investigated the role of the hypoxia-inducible transcription factor HIF-1alpha in maintaining this balance under normoxic conditions. Cardiac myocyte-specific HIF-1alpha gene deletion in the hearts of genetically engineered mice caused reductions in contractility, vascularization, high-energy phosphate content, and lactate production. This was accompanied by altered calcium flux and altered expression of genes involved in calcium handling, angiogenesis, and glucose metabolism. These findings support a central role for HIF-1alpha in coordinating energy availability and utilization in the heart and have implications for disease states in which cardiac oxygen delivery is impaired. Heart muscle requires a constant supply of oxygen. When oxygen supply does not match myocardial demand cardiac contractile dysfunction occurs, and prolongation of this mismatch leads to apoptosis and necrosis. Coordination of oxygen supply and myocardial demand involves immediate adaptations, such as coronary vasodilatation, and longer-term adaptations that include altered patterns of gene expression (2-4). How the expression of multiple genes is coordinated with oxygen availability in the heart and the impact of oxygen-dependent gene expression on cardiac function are insufficiently understood. Further elucidating these relationships may help clarify the molecular pathology of various cardiovascular disease states, including ischemic cardiomyopathy and myocardial hibernation (5, 6).

Antiapoptotic action of hypoxia-inducible factor-1 alpha in human endothelial cells

Hypoxia-inducible factor-1 (HIF-1) is the major transcription factor involved in the adaptive response to hypoxia and consists of HIF-1 alpha and HIF-1 beta subunits. Indirect evidence suggests that HIF-1 alpha may exert both proapoptotic and antiapoptotic actions in response to hypoxia. In this study, we evaluated the effects of RNA interference (RNAi) targeting HIF-1 alpha messenger RNA (mRNA) on apoptosis in primary cultured human umbilical vascular endothelial cells (HUVECs) exposed to anoxia and reoxygenation (A/R). HUVECs were transfected with specific 21-nt small interfering RNA (siRNA) duplexes targeting HIF-1 alpha mRNA sequences or scrambled RNA duplexes and subjected either to normoxia for 251/2 h or to anoxia for 11/2 h, and subsequently normoxia for 24 h (A/R). Control samples were subjected to A/R but not transfected. HUVECs apoptosis was evaluated by Tdt-mediated dUTP nick end-labeling (TUNEL) assay and by activated caspase-3 immunostaining and immunoblotting. The efficacy of RNAi was assessed by knockdown of HIF-1 alpha mRNA and protein expression via in situ hybridization, real-time quantitative PCR, immunohistochemistry, and Western blotting. When compared with normoxic cultures, A/R significantly upregulated HIF- 1 alpha mRNA and protein expression in HUVECs, but did not appreciably alter the percentage of apoptotic cells. In contrast, a significantly greater proportion of HUVECs transfected with specific siRNA duplexes and exposed to A/R demonstrated evidence of apoptosis when compared with nontransfected cells. Transfection with specific siRNA duplexes knocked down HIF-1 alpha mRNA and protein expression in A/R-treated cells by approximately 60%, whereas transfection with scrambled siRNA duplexes had no noticeable effect on HIF-1 alpha expression. These findings strongly suggest that HIF-1 alpha exerts an antiapoptotic role in HUVECs stressed by anoxia.