Angiogenesis: new insights and therapeutic potential

Enhancement of cardiac angiogenesis in a myocardial infarction rat model using selenium alone and in combination with PTXF: the role of Akt/HIF-1α signaling pathway

Ischemic heart diseases such as myocardial infarction (MI) are a global health problem and a leading cause of mortality worldwide. Angiogenesis is an important approach for myocardial healing following ischemia. Thus, this study aimed to explore the potential cardiac angiogenic effects of selenium (Se), alone and in combination with the tumor necrosis factor-alpha inhibitor, pentoxifylline (PTXF), via Akt/HIF-1α signaling. MI was induced in rats using two subcutaneous doses of isoprenaline (ISP) at a 24-h interval (150 mg/kg). One week later, rats were orally given Se (150 µg/kg/day), PTXF (50 mg/kg/day), or Se/PTXF combination. ISP-induced myocardial damage was evident by increased HW/TL ratios, ST segment elevation, and increased serum levels of CK-MB, LDH, and troponin-I. ISP increased the cardiac levels of the lipid peroxidation marker MDA; the pro-inflammatory cytokines IL-6, IL-1β, and TNF-α; and the pro-apoptotic protein Bax and caspase-3. In contrast, the cardiac levels of the antioxidant markers GSH and SOD and the anti-apoptotic marker Bcl-2 were reduced. Furthermore, ISP markedly increased the cardiac levels of p-Akt and HIF-1α proteins and the cardiac gene expression of ANGPT-1, VEGF, and FGF-2. Treatment with Se both alone and in combination with PTXF ameliorated the ISP-induced myocardial damage and further increased cardiac angiogenesis via Akt/HIF-1α signaling. Se/PTXF combined therapy was more beneficial than individual treatments. Our study revealed for the first time the cardiac angiogenic effects of Se both alone and in combination with PTXF in myocardial infarction, suggesting that both may be promising candidates for clinical studies.

Specifics of Cryopreservation of Hydrogel Biopolymer Scaffolds with Encapsulated Mesenchymal Stem Cells

The demand for regenerative medicine products is growing rapidly in clinical practice. Unfortunately, their use has certain limitations. One of these, which significantly constrains the widespread distribution and commercialization of such materials, is their short life span. For products containing suspensions of cells, this issue can be solved by using cryopreservation. However, this approach is rarely used for multicomponent tissue-engineered products due to the complexity of selecting appropriate cryopreservation protocols and the lack of established criteria for assessing the quality of such products once defrosted. Our research is aimed at developing a cryopreservation protocol for an original hydrogel scaffold with encapsulated MSCs and developing a set of criteria for assessing the quality of their functional activity in vitro. The scaffolds were frozen using two alternative types of cryocontainers and stored at either -40 °C or -80 °C. After cryopreservation, the external state of the scaffolds was evaluated in addition to recording the cell viability, visible changes during subsequent cultivation, and any alterations in proliferative and secretory activity. These observations were compared to those of scaffolds cultivated without cryopreservation. It was shown that cryopreservation at -80 °C in an appropriate type of cryocontainer was optimal for the hydrogels/adipose-derived stem cells (ASCs) tested if it provided a smooth temperature decrease during freezing over a period of at least three hours until the target values of the cryopreservation temperature regimen were reached. It was shown that evaluating a set of indicators, including the viability, the morphology, and the proliferative and secretory activity of the cells, enables the characterization of the quality of a tissue-engineered construct after its withdrawal from cryopreservation, as well as indicating the effectiveness of the cryopreservation protocol.

Training the Vessels: Molecular and Clinical Effects of Exercise on Vascular Health-A Narrative Review

Accelerated biological vascular ageing is still a major driver of the increasing burden of cardiovascular disease and mortality. Exercise training delays this process, known as early vascular ageing, but often lacks effectiveness due to a lack of understanding of molecular and clinical adaptations to specific stimuli. This narrative review summarizes the current knowledge about the molecular and clinical vascular adaptations to acute and chronic exercise. It further addresses how training characteristics (frequency, intensity, volume, and type) may influence these processes. Finally, practical recommendations are given for exercise training to maintain and improve vascular health. Exercise increases shear stress on the vascular wall and stimulates the endothelial release of circulating growth factors and of exerkines from the skeletal muscle and other organs. As a result, remodeling within the vascular walls leads to a better vasodilator and -constrictor responsiveness, reduced arterial stiffness, arterio- and angiogenesis, higher antioxidative capacities, and reduced oxidative stress. Although current evidence about specific aspects of exercise training, such as F-I-T-T, is limited, and exact training recommendations cannot be given, some practical implications can be extracted. As such, repeated stimuli 5-7 days per week might be necessary to use the full potential of these favorable physiological alterations, and the cumulative volume of mechanical shear stress seems more important than peak shear stress. Because of distinct short- and long-term effects of resistance and aerobic exercise, including higher and moderate intensities, both types of exercise should be implemented in a comprehensive training regimen. As vascular adaptability towards exercise remains high at any age in both healthy individuals and patients with cardiovascular diseases, individualized exercise-based vascular health prevention should be implemented in any age group from children to centenarians.

Vascular endothelial growth factor (VEGF) delivery approaches in regenerative medicine

The utilization of growth factors in the process of tissue regeneration has garnered significant interest and has been the subject of extensive research. However, despite the fervent efforts invested in recent clinical trials, a considerable number of these studies have produced outcomes that are deemed unsatisfactory. It is noteworthy that the trials that have yielded the most satisfactory outcomes have exhibited a shared characteristic, namely, the existence of a mechanism for the regulated administration of growth factors. Despite the extensive exploration of drug delivery vehicles and their efficacy in delivering certain growth factors, the development of a reliable predictive approach for the delivery of delicate growth factors like Vascular Endothelial Growth Factor (VEGF) remains elusive. VEGF plays a crucial role in promoting angiogenesis; however, the administration of VEGF demands a meticulous approach as it necessitates precise localization and transportation to a specific target tissue. This process requires prolonged and sustained exposure to a low concentration of VEGF. Inaccurate administration of drugs, either through off-target effects or inadequate delivery, may heighten the risk of adverse reactions and potentially result in tumorigenesis. At present, there is a scarcity of technologies available for the accurate encapsulation of VEGF and its subsequent sustained and controlled release. The objective of this review is to present and assess diverse categories of VEGF administration mechanisms. This paper examines various systems, including polymeric, liposomal, hydrogel, inorganic, polyplexes, and microfluidic, and evaluates the appropriate dosage of VEGF for multiple applications.

The Angiogenic Balance and Its Implications in Cancer and Cardiovascular Diseases: An Overview

Angiogenesis is the process of developing new blood vessels from pre-existing ones. This review summarizes the main features of physiological and pathological angiogenesis and those of angiogenesis activation and inhibition. In healthy adults, angiogenesis is absent apart from its involvement in female reproductive functions and tissue regeneration. Angiogenesis is a complex process regulated by the action of specific activators and inhibitors. In certain diseases, modulating the angiogenic balance can be a therapeutic route, either by inhibiting angiogenesis (for example in the case of tumor angiogenesis), or by trying to activate the process of new blood vessels formation, which is the goal in case of cardiac or peripheral ischemia.

Biological aspects in controlling angiogenesis: current progress

All living beings continue their life by receiving energy and by excreting waste products. In animals, the arteries are the pathways of these transfers to the cells. Angiogenesis, the formation of the arteries by the development of pre-existed parental blood vessels, is a phenomenon that occurs naturally during puberty due to certain physiological processes such as menstruation, wound healing, or the adaptation of athletes' bodies during exercise. Nonetheless, the same life-giving process also occurs frequently in some patients and, conversely, occurs slowly in some physiological problems, such as cancer and diabetes, so inhibiting angiogenesis has been considered to be one of the important strategies to fight these diseases. Accordingly, in tissue engineering and regenerative medicine, the highly controlled process of angiogenesis is very important in tissue repairing. Excessive angiogenesis can promote tumor progression and lack of enough angiogensis can hinder tissue repair. Thereby, both excessive and deficient angiogenesis can be problematic, this review article introduces and describes the types of factors involved in controlling angiogenesis. Considering all of the existing strategies, we will try to lay out the latest knowledge that deals with stimulating/inhibiting the angiogenesis. At the end of the article, owing to the early-reviewed mechanical aspects that overshadow angiogenesis, the strategies of angiogenesis in tissue engineering will be discussed.

Microvascular Experimentation in the Chick Chorioallantoic Membrane as a Model for Screening Angiogenic Agents including from Gene-Modified Cells

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.

Mechanisms Involved in Apice Closure of Pulpless Teeth – Literature Review

Background:

Unfinished root formation has always offered challenges in endodontics due to technical difficulties and weakened teeth resistance during the lifetime of an individual. Pulp revascularization therapy appeared as a solution for apical closure and root maturation. The existence of oral stem cells involved in the process associated with traditional resident cells requires adequate blood supply given by induced controlled injury deliberately accomplished into the periapical zone.

Objective:

The aim of this work was to research, through literature review, the main mechanisms involved in the process of apical closure through the technique of pulp revascularization.

Conclusion:

Apice closure in pulpless teeth seems to happen as a result of professional intervention and biological activity. The success rate depends on the role of traditional local immune cells and stem cells associated with adequate blood supply to finish root formation.

A highly-sensitive vascular endothelial growth factor-A(165) immunosensor, as a tool for early detection of cancer

Biomarkers can be ideal indicators for assessing the risk of the presence of a disease. In this study, a label-free electrochemical biosensor was designed to quantify the vascular endothelial growth factor A (165) (VEGF-A(165)) antigen, using reduced graphene oxide-gold nanoparticle for early detection of breast cancer. The conductivity of gold nanoparticle along with its biocompatibility provide an enhanced surface, suitable for anti-VEGF antibody immobilization. 11-mercaptoundecanoic acid was used to facilitate a single-step and convenient bonding of the antibodies to the surface, compared to previous studies. The dynamic range of the biosensor was between 20 to 120 pg/ml and its limit of detection of the biomarker VEGF-A(165) was obtained to be about 0.007 pg/ml, using different electric signal transduction modes. Hence, the biosensor is a beneficial immunosensor with high sensitivity and ideal dynamic range for early-stage diagnosis of breast cancer and other cancers diseases associated with expression of VEGF-A(165). The as-prepared immunosensor could be efficiently employed for designing a point-of-care diagnostic platform.

Non-Mitogenic Fibroblast Growth Factor 1 Enhanced Angiogenesis Following Ischemic Stroke by Regulating the Sphingosine-1-Phosphate 1 Pathway

Ischemic strokes account for about 80% of all strokes and are associated with a high risk of mortality. Angiogenesis of brain microvascular endothelial cells may contribute to functional restoration following ischemia. Fibroblast growth factor 1 (FGF1), a member of FGF superfamily, involved in embryonic development, angiogenesis, wound healing, and neuron survival. However, the mitogenic activity of FGF1 is known to contribute to several human pathologies, thereby questioning the safety of its clinical applications. Here, we explored the effects and mechanism of action of non-mitogenic FGF1 (nmFGF1) on angiogenesis in mice after ischemia stroke and an oxygen-glucose deprivation (OGD)-induced human brain microvascular endothelial cells (HBMECs) injury model. We found that intranasal administration nmFGF1 significantly promoted angiogenesis in mice after stroke, and significantly increased the formation of matrigel tube and promoted scratch migration in a dose-dependent manner in OGD-induced HBMECs in vitro. However, the co-administration of an FGF receptor 1 (FGFR1)-specific inhibitor PD173074 significantly reversed the effects of nmFGF1 in vitro, suggesting that nmFGF1 functions via FGFR1 activation. Moreover, nmFGF1 activated sphingosine-1-phosphate receptor 1 (S1PR1, S1P1) in mice after stroke in vivo. S1P1 protein antagonist VPC23019 and agonist FTY720 were used to confirm that nmFGF1 promotes angiogenesis in vitro partially through the S1P1 pathway. OGD induced downregulation of S1P1 expression. The S1P1 antagonist VPC23019 blocked the stimulatory effects of nmFGF1, whereas the S1P1 agonist FTY720 exerted effects comparable with those of nmFGF1. Furthermore, PD173074 reversed the effect of nmFGF1 on upregulating S1P1 signaling. In conclusion, nmFGF1 enhanced angiogenesis in mice following stroke and OGD-induced HBMECs through S1P1 pathway regulation mediated via FGFR1 activation. This new discovery suggests the potential therapeutic role of nmFGF1 for the treatment of ischemic strokes.

APOPTOSIS AND ANGIOFIBROSIS IN DIABETIC TRACTIONAL MEMBRANES AFTER VASCULAR ENDOTHELIAL GROWTH FACTOR INHIBITION: Results of a Prospective Trial. Report No. 2

PURPOSE

We sought to characterize the angiofibrotic and apoptotic effects of vascular endothelial growth factor (VEGF)-inhibition on fibrovascular epiretinal membranes in eyes with traction retinal detachment because of proliferative diabetic retinopathy.

METHODS

Membranes were excised from 20 eyes of 19 patients (10 randomized to intravitreal bevacizumab, 10 controls) at vitrectomy. Membranes were stained with antibodies targeting connective tissue growth factor (CTGF) or VEGF and colabeled with antibodies directed against endothelial cells (CD31), myofibroblasts, or retinal pigment epithelium markers. Quantitative and colocalization analyses of antibody labeling were obtained through immunofluorescence confocal microscopy. Masson trichrome staining, cell counting of hematoxylin and eosin sections, and terminal dUTP nick-end labeling staining were performed.

RESULTS

High levels of fibrosis were observed in both groups. Cell apoptosis was higher (P = 0.05) in bevacizumab-treated membranes compared with controls. The bevacizumab group had a nonsignificant reduction in colocalization in CD31-CTGF and cytokeratin-VEGF studies compared with controls. Vascular endothelial growth factor in extracted membranes was positively correlated with vitreous levels of VEGF; CTGF in extracted membranes was negatively correlated with vitreous levels of CTGF.

CONCLUSION

Bevacizumab suppresses vitreous VEGF levels, but does not significantly alter VEGF or CTGF in diabetic membranes that may be explained by high baseline levels of fibrosis. Bevacizumab may cause apoptosis within fibrovascular membranes.

Angiopoietin 2 signal complexity in cardiovascular disease and cancer

The angiopoietin signal transduction system is a complex of vascular-specific kinase pathways that plays a crucial role in angiogenesis and maintenance of vascular homeostasis. Angiopoietin1 (Ang1) and 2 (Ang2), the ligand proteins of the pathway, belong to a family of glycoproteins that signal primarily through the transmembrane Tyrosine-kinase-2 receptor. Despite a considerable sequence homology, Ang1 and Ang2 manifest antagonistic effects in pathophysiological conditions. While Ang1 promotes the activation of survival pathways and the stabilization of the normal mature vessels, Ang2 can either favor vessel destabilization and leakage or promote abnormal EC proliferation in a context-dependent manner. Altered Ang1/Ang2 balance has been reported in various pathological conditions in association with inflammation and deregulated angiogenesis. In particular, increased Ang2 levels have been documented in human cancer and cardiovascular disease (CVD), including ischemic myocardial injury, heart failure and other cardiovascular complications secondary to diabetes, chronic renal damage and hypertension. Despite the obvious phenotypic differences, CVD and cancer share some common Ang2-dependent etiopathological mechanisms such as inflammation, epithelial (or endothelial) to mesenchymal transition, and adverse vascular network remodeling. Interestingly, both cancer and CVD are negatively affected by thyroid hormone dyshomeostasis. This review provides an overview of the complex Ang2-dependent signaling involved in CVD and cancer, as well as a survey of the related clinical literature. Moreover, on the basis of recent molecular acquisitions in an experimental model of post ischemic cardiac disease, the putative novel role of the thyroid hormone in the regulation of Ang1/Ang2 balance is also briefly discussed.

Ishige okamurae Extract and Its Constituent Ishophloroglucin A Attenuated In Vitro and In Vivo High Glucose-Induced Angiogenesis

Diabetes is associated with vascular complications, such as impaired wound healing and accelerated vascular growth. The different clinical manifestations, such as retinopathy and nephropathy, reveal the severity of enhanced vascular growth known as angiogenesis. This study was performed to evaluate the effects of an extract of Ishige okamurae (IO) and its constituent, Ishophloroglucin A (IPA) on high glucose-induced angiogenesis. A transgenic zebrafish (flk:EGFP) embryo model was used to evaluate vessel growth. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), gap closure, transwell, and Matrigel® assays were used to analyze the proliferation, migration, and capillary formation of EA.hy926 cells. Moreover, protein expression were determined using western blotting. IO extract and IPA suppressed vessel formation in the transgenic zebrafish (flk:EGFP) embryo. IPA attenuated cell proliferation, cell migration, and capillary-like structure formation in high glucose-treated human vascular endothelial cells. Further, IPA down regulated the expression of high glucose-induced vascular endothelial growth factor receptor 2 (VEGFR-2) and downstream signaling molecule cascade. Overall, the IO extract and IPA exhibited anti-angiogenic effects against high glucose-induced angiogenesis, suggesting their potential for use as therapeutic agents in diabetes-related angiogenesis.

Diphlorethohydroxycarmalol Isolated from Ishige okamurae Represses High Glucose-Induced Angiogenesis In Vitro and In Vivo

Diabetes mellitus causes abnormalities of angiogenesis leading to vascular dysfunction and serious pathologies. Diphlorethohydroxycarmalol (DPHC), which is isolated from Ishige okamurae, is well known for its bioactivities, including antihyperglycemic and protective functions against diabetes-related pathologies. In the present study, the inhibitory effect of DPHC on high glucose-induced angiogenesis was investigated on the human vascular endothelial cell line EA.hy926. DPHC inhibited the cell proliferation, cell migration, and tube formation in cells exposed to 30 mM of glucose to induce angiogenesis. Furthermore, the effect of DPHC against high glucose-induced angiogenesis was evaluated in zebrafish embryos. The treatment of embryos with DPHC suppressed high glucose-induced dilation in the retinal vessel diameter and vessel formation. Moreover, DPHC could inhibit high glucose-induced vascular endothelial growth factor receptor 2 (VEGFR-2) expression and its downstream signaling cascade. Overall, these findings suggest that DPHC is actively involved in the suppression of high glucose-induced angiogenesis. Hence, DPHC is a potential agent for the development of therapeutics against angiogenesis induced by diabetes.

Development of VEGF-loaded PLGA matrices in association with mesenchymal stem cells for tissue engineering

The association of bioactive molecules, such as vascular endothelial growth factor (VEGF), with nanofibers facilitates their controlled release, which could contribute to cellular migration and differentiation in tissue regeneration. In this research, the influence of their incorporation on a polylactic-co-glycolic acid (PLGA) scaffold produced by electrospinning on cell adhesion and viability and cytotoxicity was carried out in three groups: 1) PLGA/BSA/VEGF; 2) PLGA/BSA, and 3) PLGA. Morphology, fiber diameter, contact angle, loading efficiency and controlled release of VEGF of the biomaterials, among others, were measured. The nanofibers showed smooth surfaces without beads and with interconnected pores. PLGA/BSA/VEGF showed the smallest water contact angle and VEGF released for up to 160 h. An improvement in cell adhesion was observed for the PLGA/BSA/VEGF scaffolds compared to the other groups and the scaffolds were non-toxic for the cells. Therefore, the scaffolds were shown to be a good strategy for sustained delivery of VEGF and may be a useful tool for tissue engineering.

T3 enhances Ang2 in rat aorta in myocardial I/R: comparison with left ventricle

Angiogenesis is important for recovery after tissue damage in myocardial ischemia/reperfusion, and tri-iodothyronine (T3) has documented effects on angiogenesis. The angiopoietins 1/2 and tyrosine kinase receptor represent an essential system in angiogenesis controlling endothelial cell survival and vascular maturation. Recently, in a 3-day ischemia/reperfusion rat model, the infusion of a low dose of T3 improved the post-ischemic recovery of cardiac function.Adopting this model, our study aimed to investigate the effects of T3 on the capillary index and the expression of angiogenic genes as the angiopoietins 1/2 and tyrosine kinase receptor system, in the thoracic aorta and in the left ventricle. In the thoracic aorta, T3 infusion significantly improved the angiogenic sprouting and angiopoietin 2 expression. Instead, Sham-T3 group did not show any significant increment of capillary density and angiopoietin 2 expression. In the area at risk (AAR) of the left ventricle, T3 infusion did not increase capillary density but restored levels of angiopoietin 1, which were reduced in I/R group. Angiopoietin 2 levels were similar to Sham group and unchanged by T3 administration. In the remote zone, T3 induced a significant increment of both angiopoietin 1/2. In conclusion, T3 infusion induced a different response of angiopoietin 1/2 between the ventricle (the AAR and the remote zone) and the thoracic aorta, probably reflecting the different action of angiopoietin 1/2 in cardiomyocytes and endothelial cells. Overall, these data suggest a new aspect of T3-mediated cardioprotection through angiogenesis.

Endothelial colony-forming cells: Biological and functional abnormalities in patients with recurrent, unprovoked venous thromboembolic disease

INTRODUCTION

Endothelial cells (ECs) are an important component of the blood coagulation system because it maintains blood fluid. Because in patients with venous thromboembolic disease (VTD) a thrombophilic condition is not found sometimes, we investigated if endothelial colony-forming cells (ECFCs) from these patients have biological and functional abnormalities.

PATIENTS AND METHODS

Human mononuclear cells (MNCs) were obtained from peripheral blood from patients with VTD and controls to obtain ECFCs. These cells were assayed for their immunophenotype and electron microscopy characteristics and their ability to form capillary-like structures and to produce pro-inflammatory and pro-angiogenic cytokines and reactive oxygen species (ROS).

RESULTS

ECFCs appeared at 7 and 21 days of culture in VTD patients and controls, respectively. ECFCs increased 8-fold in patients and emerged 1 week earlier. No differences in the size of the colonies of ECFCs were found. Numbers and time of appearance of ECFCs was different between groups. ECFC-derived ECs (ECFC-ECs) of both groups expressed CD31, CD34, CD146, and CD-309 but none expressed CD45, CD14, or CD90. Interest CD34 was highly expressed in ECFC-ECs from patients. In both groups, ECFC-ECs showed similar capacity to form capillary-like structures but ECFC-ECs from patients had significant abnormalities in the mitochondrial membrane. We found a significant increase in ROS production in ECFC-ECs from patients. There were significant differences in cytokine profiles between VTD patients and controls.

CONCLUSIONS

We found a dysfunctional state in ECFC from VTD patients resembling some characteristics of dysfunctional ECs. These findings may help to understand some pathophysiological aspects of VTD.

Molecular Mechanisms for Exercise Training-Induced Changes in Vascular Structure and Function: Skeletal Muscle, Cardiac Muscle, and the Brain

Compared with resting conditions, during incremental exercise, cardiac output in humans is elevated from ~5 to 25 L min(-1). In conjunction with this increase, the proportion of cardiac output directed toward skeletal muscle increases from ~20% to 85%, while blood flow to cardiac muscle increases 500% and blood flow to specific brain structures increases nearly 200%. Based on existing evidence, researchers believe that blood flow in these tissues is matched to the increases in metabolic rate during exercise. This phenomenon, the matching of blood flow to metabolic requirement, is often referred to as functional hyperemia. This chapter summarizes mechanical and metabolic factors that regulate functional hyperemia as well as other exercise-induced signals, which are also potent stimuli for chronic adaptations in vascular biology. Repeated exposure to exercise-induced increases in shear stress and the induction of angiogenic factors alter vascular cell gene expression and mediate changes in vascular volume and blood flow control. The magnitude and regulation of this coordinated response appear to be tissue specific and coupled to other factors such as hypertrophy and hyperplasia. The cumulative effects of these adaptations contribute to increased exercise capacity, reduced relative challenge of a given submaximal exercise bout and ameliorated vascular outcomes in patient populations with pathological conditions. In the subsequent discussion, this chapter explores exercise as a regulator of vascular biology and summarizes the molecular mechanisms responsible for exercise training-induced changes in vascular structure and function in skeletal and cardiac muscle as well as the brain.

WT1 regulates angiogenesis in Ewing Sarcoma

Angiogenesis is required for tumor growth. WT1, a protein that affects both mRNA transcription and splicing, has recently been shown to regulate expression of vascular endothelial growth factor (VEGF), one of the major mediators of angiogenesis. In the present study, we tested the hypothesis that WT1 is a key regulator of tumor angiogenesis in Ewing sarcoma. We expressed exogenous WT1 in the WT1-null Ewing sarcoma cell line, SK-ES-1, and we suppressed WT1 expression using shRNA in the WT1-positive Ewing sarcoma cell line, MHH-ES. Suppression of WT1 in MHH-ES cells impairs angiogenesis, while expression of WT1 in SK-ES-1 cells causes increased angiogenesis. Different WT1 isoforms result in vessels with distinct morphologies, and this correlates with preferential upregulation of particular VEGF isoforms. WT1-expressing tumors show increased expression of pro-angiogenic molecules such as VEGF, MMP9, Ang-1, and Tie-2, supporting the hypothesis that WT1 is a global regulator of angiogenesis. We also demonstrate that WT1 regulates the expression of a panel of pro-angiogenic molecules in Ewing sarcoma cell lines. Finally, we found that WT1 expression is correlated with VEGF expression, MMP9 expression, and microvessel density in samples of primary Ewing sarcoma. Thus, our results demonstrate that WT1 expression directly regulates tumor angiogenesis by controlling the expression of a panel of pro-angiogenic genes.

Effects of integrins and integrin αvβ3 inhibitor on angiogenesis in cerebral ischemic stroke

Integrins such as αvβ3, α5β1 play a key role in angiogenesis regulation, invasion and metastasis, inflammation, wound healing, etc. The up-regulation of integrin αvβ3 after cerebral ischemic stroke can promote angiogenesis, which in turn improves functional recovery. In addition, the integrin αvβ3 inhibitor can block the blood-brain barrier (BBB) leakage induced by vascular endothelial growth factor (VEGF) and also can reduce inflammatory reaction, decrease the deposition of fibrinogen. Other studies showed that integrin αvβ3 is not essential in revascularization. Therefore, the effect of integrin αvβ3 in the whole process of brain function recovery merits further study.

Silicate bioceramics enhanced vascularization and osteogenesis through stimulating interactions between endothelia cells and bone marrow stromal cells

The facts that biomaterials affect the behavior of single type of cells have been widely accepted. However, the effects of biomaterials on cell-cell interactions have rarely been reported. Bone tissue engineering involves osteoblastic cells (OCs), endothelial cells (ECs) and the interactions between OCs and ECs. It has been reported that silicate biomaterials can stimulate osteogenic differentiation of OCs and vascularization of ECs. However, the effects of silicate biomaterials on the interactions between ECs and OCs during vascularization and osteogenesis have not been reported, which are critical for bone tissue regeneration in vivo. Therefore, this study aimed to investigate the effects of calcium silicate (CS) bioceramics on interactions between human umbilical vein endothelial cells (HUVECs) and human bone marrow stromal cells (HBMSCs) and on stimulation of vascularization and osteogenesis in vivo through combining co-cultures with CS containing scaffolds. Specifically, the effects of CS on the angiogenic growth factor VEGF, osteogenic growth factor BMP-2 and the cross-talks between VEGF and BMP-2 in the co-culture system were elucidated. Results showed that CS stimulated co-cultured HBMSCs (co-HBMSCs) to express VEGF and the VEGF activated its receptor KDR on co-cultured HUVECs (co-HUVECs), which was also up-regulated by CS. Then, BMP-2 and nitric oxide expression from the co-HUVECs were stimulated by CS and the former stimulated osteogenic differentiation of co-HBMSCs while the latter stimulated vascularization of co-HVUECs. Finally, the poly(lactic-co-glycolic acid)/CS composite scaffolds with the co-cultured HBMSCs and HUVECs significantly enhanced vascularization and osteogenic differentiation in vitro and in vivo, which indicates that it is a promising way to enhance bone regeneration by combining scaffolds containing silicate bioceramics and co-cultures of ECs and OCs.

Angiogenesis factors involved in the pathogenesis of colorectal cancer

Colorectal cancer stands at the top of oncologic pathology in the world, and in the same measure in Romania because is the third most frequent cancer diagnosed in men and women. Colorectal cancer develops as a result of mutations in genes that control proliferation and cell death. It was established that in the development of a tumor there is originally a prevascular phase followed by a phase of tumor angiogenesis. In the future it is necessary to develop new clinical protocols that angiogenesis inhibitors are associated with chemo or radiotherapy, conventional or other methods such as immunotherapy and gene therapy.

Vulnerability of the developing brain to hypoxic-ischemic damage: contribution of the cerebral vasculature to injury and repair?

As clinicians attempt to understand the underlying reasons for the vulnerability of different regions of the developing brain to injury, it is apparent that little is known as to how hypoxia-ischemia may affect the cerebrovasculature in the developing infant. Most of the research investigating the pathogenesis of perinatal brain injury following hypoxia-ischemia has focused on excitotoxicity, oxidative stress and an inflammatory response, with the response of the developing cerebrovasculature receiving less attention. This is surprising as the presentation of devastating and permanent injury such as germinal matrix-intraventricular haemorrhage (GM-IVH) and perinatal stroke are of vascular origin, and the origin of periventricular leukomalacia (PVL) may also arise from poor perfusion of the white matter. This highlights that cerebrovasculature injury following hypoxia could primarily be responsible for the injury seen in the brain of many infants diagnosed with hypoxic-ischemic encephalopathy (HIE). Interestingly the highly dynamic nature of the cerebral blood vessels in the fetus, and the fluctuations of cerebral blood flow and metabolic demand that occur following hypoxia suggest that the response of blood vessels could explain both regional protection and vulnerability in the developing brain. However, research into how blood vessels respond following hypoxia-ischemia have mostly been conducted in adult models of ischemia or stroke, further highlighting the need to investigate how the developing cerebrovasculature responds and the possible contribution to perinatal brain injury following hypoxia. This review discusses the current concepts on the pathogenesis of perinatal brain injury, the development of the fetal cerebrovasculature and the blood brain barrier (BBB), and key mediators involved with the response of cerebral blood vessels to hypoxia.

Aberrant angiogenesis: The gateway to diabetic complications

Diabetes Mellitus is a metabolic cum vascular syndrome with resultant abnormalities in both micro- and macrovasculature. The adverse long-term effects of diabetes mellitus have been described to involve many organ systems. Apart from hyperglycemia, abnormalities of angiogenesis may cause or contribute toward many of the clinical manifestations of diabetes. These are implicated in the pathogenesis of vascular abnormalities of the retina, kidneys, and fetus, impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. The current article hereby reviews the molecular mechanisms including abnormalities in growth factors, cytokines, and metabolic derangements, clinical implications, and therapeutic options of dealing with abnormal angiogenesis in diabetes.

Nongenomic effects of thyroid hormones on the immune system cells: New targets, old players

It is now widely accepted that thyroid hormones, l-thyroxine (T(4)) and 3,3',5-triiodo-l-thyronine (T(3)), act as modulators of the immune response. Immune functions such as chemotaxis, phagocytosis, generation of reactive oxygen species, and cytokine synthesis and release, are altered in hypo- and hyper-thyroid conditions, even though for many immune cells no clear correlation has been found between altered levels of T(3) or T(4) and effects on the immune responses. Integrins are extracellular matrix proteins that are important modulators of many cellular responses, and the integrin αvβ3 has been identified as a cell surface receptor for thyroid hormones. Rapid signaling via this plasma membrane binding site appears to be responsible for many nongenomic effects of thyroid hormones, independent of the classic nuclear receptors. Through the integrin αvβ3 receptor the hormone can activate both the ERK1/2 and phosphatidylinositol 3-kinase pathways, with downstream effects including intracellular protein trafficking, angiogenesis and tumor cell proliferation. It has recently become clear that an important downstream target of the thyroid hormone nongenomic pathway may be the mammalian target of rapamycin, mTOR. New results demonstrate the capability of T(3) or T(4) to induce in the short time range important responses related to the immune function, such as reactive oxygen species production and cell migration in THP-1 monocytes. Thus thyroid hormones seem to be able to modulate the immune system by a combination of rapid nongenomic responses interacting with the classical nuclear response.

Activation of alternative pathways of angiogenesis and involvement of stem cells following anti-angiogenesis treatment in glioma

Malignant gliomas are hypervascular tumors that are highly resistant to all the currently available multimodal treatments. Therefore, anti-angiogenic therapies targeting VEGF or VEGF receptors (VEGFRs) were designed and thought to be an effective tool for controlling the growth of malignant gliomas. However, recent results of early clinical trials using humanized monoclonal antibodies against VEGF (Bevacizumab), as well as small-molecule tyrosine kinase inhibitors that target different VEGF receptors (VEGFRs) (Vatalanib, Vandetanib, Sunitinib, Sorafenib, etc) alone or in combination with other therapeutic agents demonstrated differing outcomes, with the majority of reports indicating that glioma developed resistance to the employed anti-angiogenic treatments. It has been noted that continued anti-angiogenic therapy targeting only the VEGF-VEGFR system might affect pro-angiogenic factors other than VEGF, such as basic fibroblast growth factor (bFGF), stromal derived factor 1 (SDF-1) and Tie-2. These factors may in turn stimulate angiogenesis by mobilizing bone marrow derived precursor cells, such as endothelial progenitor cells (EPCs), which are known to promote angiogenesis and vasculogenesis. In this short review, the current antiangiogenic treatments, possible mechanisms of activation of alternative pathways of angiogenesis, and possible involvement of bone marrow derived progenitor cells in the failure of anti-angiogenic treatments are discussed.

Seasonal Changes in Testes Vascularisation in the Domestic Cat (Felis domesticus): Evaluation of Microvasculature, Angiogenic Activity, and Endothelial Cell Expression

Some male seasonal breeders undergo testicular growth and regression throughout the year. The objective of this study was to understand the effect of seasonality on: (i) microvasculature of cat testes; (ii) angiogenic activity in testicular tissue in vitro; and (iii) testicular endothelial cells expression throughout the year. Testicular vascular areas increased in March and April, June and July, being the highest in November and December. Testes tissue differently stimulated in vitro angiogenic activity, according to seasonality, being more evident in February, and November and December. Even though CD143 expression was higher in December, smaller peaks were present in April and July. As changes in angiogenesis may play a role on testes vascular growth and regression during the breeding and non-breeding seasons, data suggest that testicular vascularisation in cats is increased in three photoperiod windows of time, November/December, March/April and June/July. This increase in testicular vascularisation might be related to higher seasonal sexual activity in cats, which is in agreement with the fact that most queens give birth at the beginning of the year, between May and July, and in September.

Endothelial dysfunction and diabetes: effects on angiogenesis, vascular remodeling, and wound healing

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by inappropriate hyperglycemia due to lack of or resistance to insulin. Patients with DM are frequently afflicted with ischemic vascular disease or wound healing defect. It is well known that type 2 DM causes amplification of the atherosclerotic process, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. These complications ultimately lead to impairment of neovascularization and diabetic wound healing. Therapeutic angiogenesis remains an attractive treatment modality for chronic ischemic disorders including PAD and/or diabetic wound healing. Many experimental studies have identified better approaches for diabetic cardiovascular complications, however, successful clinical translation has been limited possibly due to the narrow therapeutic targets of these agents or the lack of rigorous evaluation of pathology and therapeutic mechanisms in experimental models of disease. This paper discusses the current body of evidence identifying endothelial dysfunction and impaired angiogenesis during diabetes.

Structural characteristics of small intestinal submucosa constructs dictate in vivo incorporation and angiogenic response

The rate of angiogenesis and cellular infiltration into degradable biomaterials determines scaffold persistence in vivo. The ability to tune the degradation properties of naturally derived biomaterials has been a popular goal in tissue engineering, yet has often depended on chemical crosslinking. Small intestinal submucosa (SIS) is a naturally derived, collagen-based, bioactive scaffold that has broad clinical success in many therapeutic applications. Two methods for producing multilayer, non-crosslinked SIS constructs were compared in vitro and in vivo. Traditional and cryo SEM, mercury intrusion porosimetry, and a novel enzymatic degradation assay determined that lyophilization produced an open, porous scaffold, in contrast to the collapsed, denser structure of SIS constructs produced using a vacuum press process. The angiogenic responses to lyophilized and vacuum-pressed SIS constructs were evaluated in vivo using a subcutaneous implant assay in mice. Explanted samples were compared after 7 and 21 days using fluorescence microangiography and light microscopy. Capacity of the implant neovasculature was also determined. These experiments revealed that the lyophilized SIS was infiltrated and vascularized more rapidly than the vacuum pressed. These data demonstrate the tunable incorporation of a non-crosslinked ECM-based biomaterial, which may have implications for the persistence of this degradable scaffold in tissue engineering.

Hypoxia increases placenta growth factor expression in human myocardium and cultured neonatal rat cardiomyocytes

BACKGROUND

Placenta growth factor (PlGF) plays an important role in pathologic angiogenesis and is believed to be an independent biomarker in patients with coronary artery disease. However, little is known regarding the regulation of PlGF expression in heart tissue.

METHODS

We determined expression changes in PlGF and its receptor, VEGFR1, in normal and abnormal biopsies from human cardiac allografts and in cardiomyocytes cultured under hypoxia or cyclical stretch conditions.

RESULTS

Human donor myocardium and biopsies from allografts without fibrin deposits expressed PlGF and VEGFR1 mRNA. Biopsies (n = 7) with myocardial fibrin, elevated serum cardiac troponin I titers (p < 0.03) and cellular infiltrates (p < 0.05) expressed 1.6-fold more PlGF mRNA than biopsies from allografts without fibrin (n = 11; p < 0.05). PlGF protein was localized in cardiomyocytes, extracellular matrix and some microvessels in areas with fibrin deposition. VEGFR1 mRNA expression was not different between groups. Cultured neonatal rat cardiomyocytes constitutively expressed PlGF/VEGFR1 under normoxia. PlGF expression was increased 3.88 +/- 0.62-fold after 12 hours (n = 6; p </= 0.05) and 3.64 +/- 0.41-fold after 24 hours of hypoxia (n = 6; p <or= 0.05). Shorter periods of hypoxia, conditioned media from hypoxic cells and cyclical stretch did not significantly alter PlGF or VEGFR1 expression.

CONCLUSIONS

Cardiomyocyte PIGF expression is upregulated by hypoxia in vitro and its expression increases significantly in allografts with myocardial damage. Collectively, these results provide important temporal and spatial evidence that endogenous PlGF may facilitate cardiac healing after myocardial hypoxia/ischemia.

Secretome from mesenchymal stem cells induces angiogenesis via Cyr61

It is well known that bone marrow-derived mesenchymal stem cells (MSCs) are involved in wound healing and regeneration responses. In this study, we globally profiled the proteome of MSCs to investigate critical factor(s) that may promote wound healing. Cysteine-rich protein 61 (Cyr61) was found to be abundantly present in MSCs. The presence of Cyr61 was confirmed by immunofluorescence staining and immunoblot analysis. Moreover, we showed that Cyr61 is present in the culture medium (secretome) of MSCs. The secretome of MSCs stimulates angiogenic response in vitro, and neovascularization in vivo. Depletion of Cyr61 completely abrogates the angiogenic-inducing capability of the MSC secretome. Importantly, addition of recombinant Cyr61 polypeptides restores the angiogenic activity of Cyr61-depleted secretome. Collectively, these data demonstrate that Cyr61 polypeptide in MSC secretome contributes to the angiogenesis-promoting activity, a key event needed for regeneration and repair of injured tissues. J. Cell. Physiol. 219: 563-571, 2009. (c) 2009 Wiley-Liss, Inc.

Drawbacks to stem cell therapy in cardiovascular diseases

Stem cells seem to have unlimited potential for repairing injured tissues derived from cardiovascular diseases. Much as the initial euphoria over preclinical models has ushered in some skepticism, several reports have advised caution against over exuberance, as cellular therapy has both theoretical and reported safety concerns. Embryonic stem cells, skeletal myoblasts, bone marrow-derived stem cells and mesenchymal stem cells are current candidates for cell therapy in end-stage cardiovascular diseases. However, before large-scale clinical trials can take place, a few safety concerns have to be clarified, such as atherogenesis, postangioplasty or stenting restenosis, tumorigenesis, stem cell metastasis, stem cell-mobilized cytokine-related complications and arrhythmogenesis. In this review, potential ways to overcome these issues are discussed, including medical and gene manipulations, dedicated cell-purification techniques, antiarrhythmic cell therapy design, and new concepts such as using natural constructs. With these safety issues under control, stem cell therapy still has a promising future in the next decade.

Detection of migration of locally implanted AC133+ stem cells by cellular magnetic resonance imaging with histological findings

This study investigated the factors responsible for migration and homing of magnetically labeled AC133(+) cells at the sites of active angiogenesis in tumor. AC133(+) cells labeled with ferumoxide-protamine sulfate were mixed with either rat glioma or human melanoma cells and implanted in flank of nude mice. An MRI of the tumors including surrounding tissues was performed. Tumor sections were stained for Prussian blue (PB), platelet-derived growth factor (PDGF), hypoxia-inducible factor-1alpha (HIF-1alpha), stromal cell derived factor-1 (SDF-1), matrix metalloproteinase-2 (MMP-2), vascular endothelial growth factor (VEGF), and endothelial markers. Fresh snap-frozen strips from the central and peripheral parts of the tumor were collected for Western blotting. MRIs demonstrated hypointense regions at the periphery of the tumors where the PB(+)/AC133(+) cells were positive for endothelial cells markers. At the sites of PB(+)/AC133(+) cells, both HIF-1alpha and SDF-1 were strongly positive and PDGF and MMP-2 showed generalized expression in the tumor and surrounding tissues. There was no significant association of PB(+)/AC133(+) cell localization and VEGF expression in tumor cells. Western blot demonstrated strong expression of the SDF-1, MMP-2, and PDGF at the peripheral parts of the tumors. HIF-1alpha was expressed at both the periphery and central parts of the tumor. This work demonstrates that magnetically labeled cells can be used as probes for MRI and histological identification of administered cells.

Late-Outgrowth Endothelial Cells Attenuate Intimal Hyperplasia Contributed by Mesenchymal Stem Cells After Vascular Injury

Objectives— Mesenchymal stem cells (MSCs) are one of a number of cell types undergoing extensive investigation for cardiac regeneration therapy. It has not yet been determined whether this cell therapy also substantially contributes to vascular remodeling of diseased vessels.

Methods and Results— Human MSCs and a variety of progenitor and vascular cells were used for in vitro and in vivo experiments. Wire-induced vascular injury mobilized MSCs into the circulation. Compared with human aortic smooth muscle cells, MSCs exhibited a 2.8-fold increase in the adhesion capacity in vitro ( P <0.001) and a 6.3-fold increase in vivo ( P <0.001). In all animal models, a significant amount of MSCs contributed to intimal hyperplasia after vascular injury. MSCs were able to differentiate into cells of endothelial or smooth muscle lineage. Coculture experiments demonstrated that late-outgrowth endothelial cells (OECs) guided MSCs to differentiate toward an endothelial lineage through a paracrine effects. In vivo, cell therapy with OECs significantly attenuated the thickness of the neointima contributed by MSCs (intima/media ratio, from 3.2±0.4 to 0.4±0.1, P <0.001).

Conclusions— Tissue regeneration therapy with MSCs or cell populations containing MSCs requires a strategy to attenuate the high potential of MSCs to develop intimal hyperplasia on diseased vessels.

Imaging of angiogenesis in cardiology

In the past decade, there have been major improvements in our understanding of angiogenesis at the genetic, molecular and cellular levels. Concentrated efforts in this area have led to new therapeutic approaches to ischaemic heart disease using angiogenic factors, gene therapy and progenitor cells. Despite very promising experimental results in animal studies, large clinical trials have failed to confirm the results in patients with coronary artery disease. Important questions such as selection of growth factors and donor cells, as well as the timing, dose and route of administration, have been raised and need to be answered. Molecular imaging approaches which may provide specific markers of the angiogenic process (e.g. integrin expression in endothelial cells) have been introduced and are expected to address some of these questions. Although few clinical imaging results are currently available, animal studies suggest the potential role of molecular imaging for characterisation of the angiogenetic process in vivo and for the monitoring of therapeutic effects.

Angiogenesis therapies for cardiovascular disease

PURPOSE OF REVIEW

The purpose was to summarize the findings of the proangiogenic clinical trials using protein and gene therapy, with analysis of the problems and an interpretation of the results.

RECENT FINDINGS

Recent findings include several new large clinical trials, using both gene and protein therapies. There has been development of new basic science concepts, especially with regard to endothelial activation and stabilization of newly formed microvessels. This review provides a critical analysis of the most recent clinical trials, both in efforts to understand the pitfalls of earlier clinical trials, and also to focus on requirements for future studies.

SUMMARY

This article reviews many of the clinical trials utilizing proangiogenic therapy, assesses the pitfalls seen within the current trials, and discusses the conclusions drawn and the future of angiogenesis therapy.

Upregulation of hypoxia inducible factor 1α mRNA is associated with elevated vascular endothelial growth factor expression and excessive angiogenesis and predicts a poor prognosis in gastric carcinoma

AIM: To investigate the implication of the hypoxia inducible factor HIF-1α mRNA in gastric carcinoma and its relation to the expression of vascular endothelial growth factor (VEGF) protein, tumor angiogenesis invasion/metastasis and the patient's survival.

METHODS: In situ hybridization was used to examine expression of HIF-1α mRNA, and immunohistochemical staining was used to examine expression of VEGF protein and CD34 in 118 specimens from patients with gastric carcinoma.

RESULTS: The positive rates of HIF-1α mRNA and VEGF protein were 49.15% and 55.92%, respectively. Positive expressions of HIF-1α and VEGF in stage T₃-T₄ tumors and those with vessel invasion, lymph node metastasis and distant metastasis were dramatically stronger than stage T₁-T₂ cases and those without vessel invasion, lymph node metastasis and distant metastasis. The mean microvascular density (MVD) in stage T₃-T₄ tumors and those with vessel invasion, lymph node metastasis and distant metastasis was significantly higher than stage T₁-T₂ tumors and those without vessel invasion, lymph node metastasis and distant metastasis. The mean MVD in tumors with positive HIF-1α and VEGF expression was significantly higher than that in tumors with negative HIF-1α and VEGF expression. The expression of HIF-1α was positively correlated with VEGF protein. There were positive correlations between MVD and expression of HIF-1α and VEGF. The mean survival time and the 5-year survival rate in cases with positive expression HIF-1α and VEGF and MVD value ≥ 41.5/0.72 mm² were significantly lower than those with negative expression of HIF-1α and VEGF and MVD value < 41.5/0.72 mm².

CONCLUSION: Overexpression of HIF-1α is found in gastric carcinoma. HIF-1α may induce the angiogenesis in gastric carcinoma by upregulating the transcription of VEGF gene, and take part in tumor invasion and metastasis. They can be used as prognostic markers of gastric cancer in clinical practice.