Angiogenesis of the heart

Uncovering the link between diabetes and cardiovascular diseases: insights from adipose-derived stem cells

Cardiovascular diseases (CVDs) are the leading causes of morbidity and mortality worldwide. The escalating global occurrence of obesity and diabetes mellitus (DM) has led to a significant upsurge in individuals afflicted with CVDs. As the prevalence of CVDs continues to rise, it is becoming increasingly important to identify the underlying cellular and molecular mechanisms that contribute to their development and progression, which will help discover novel therapeutic avenues. Adipose tissue (AT) is a connective tissue that plays a crucial role in maintaining lipid and glucose homeostasis. However, when AT is exposed to diseased conditions, such as DM, this tissue will alter its phenotype to become dysfunctional. AT is now recognized as a critical contributor to CVDs, especially in patients with DM. AT is comprised of a heterogeneous cellular population, which includes adipose-derived stem cells (ADSCs). ADSCs resident in AT are believed to regulate physiological cardiac function and have potential cardioprotective roles. However, recent studies have also shown that ADSCs from various adipose tissue depots become pro-apoptotic, pro-inflammatory, less angiogenic, and lose their ability to differentiate into various cell lineages upon exposure to diabetic conditions. This review aims to summarize the current understanding of the physiological roles of ADSCs, the impact of DM on ADSC phenotypic changes, and how these alterations may contribute to the pathogenesis of CVDs.

Biofunctionalization and Applications of Polymeric Nanofibers in Tissue Engineering and Regenerative Medicine

The limited ability of most human tissues to regenerate has necessitated the interventions namely autograft and allograft, both of which carry the limitations of its own. An alternative to such interventions could be the capability to regenerate the tissue in vivo.Regeneration of tissue using the innate capacity of the cells to regenerate is studied under the discipline of tissue engineering and regenerative medicine (TERM). Besides the cells and growth-controlling bioactives, scaffolds play the central role in TERM which is analogous to the role performed by extracellular matrix (ECM) in the vivo. Mimicking the structure of ECM at the nanoscale is one of the critical attributes demonstrated by nanofibers. This unique feature and its customizable structure to befit different types of tissues make nanofibers a competent candidate for tissue engineering. This review discusses broad range of natural and synthetic biodegradable polymers employed to construct nanofibers as well as biofunctionalization of polymers to improve cellular interaction and tissue integration. Amongst the diverse ways to fabricate nanofibers, electrospinning has been discussed in detail along with advances in this technique. Review also presents a discourse on application of nanofibers for a range of tissues, namely neural, vascular, cartilage, bone, dermal and cardiac.

Potential of Circulating Proangiogenic MicroRNAs for Predicting Major Adverse Cardiac and Cerebrovascular Events in Unprotected Left Main Coronary Artery Disease Patients Who Underwent Coronary Artery Bypass Grafting

OBJECTIVE

This study aimed to explore the association of 14 proangiogenic microRNAs (miRNAs) with major adverse cardiac and cerebrovascular events (MACCE) occurrence in unprotected left main coronary artery disease (ULMCAD) patients who underwent coronary artery bypass grafting (CABG).

METHODS

A total of 196 ULMCAD patients who underwent first ever CABG were recruited. The peripheral blood samples were collected prior to CABG, and then plasma samples were separated to detect expressions of 14 proangiogenic miRNAs by the reverse transcription quantitative PCR. Patients were regularly followed up to MACCE occurrence or 36 months after CABG.

RESULTS

MACCE occurrence at 1 year, 2 years, and 3 years was 7.1, 11.2, and 14.3%, respectively, and accumulating MACCE occurrence time was 32.7 (95% confidence interval: 31.5-33.9) months. Both Kaplan-Meier curves and univariate Cox's regression analyses displayed that miR-let-7f, miR-19a, miR-126, miR-130a, and miR-378 high expressions were associated with lower accumulating MACCE occurrence. Furthermore, forward stepwise multivariate Cox's regression disclosed that miR-let-7f high expression and miR-378 high expression independently predicted decreased accumulating MACCE occurrence, whereas BMI (>25.0 kg/m2), diabetes, previous stroke, and higher disease extent were independent predictive factors for elevated accumulating MACCE occurrence.

CONCLUSION

Measurement of circulating proangiogenic miRNAs especially miR-let-7f, miR-19a, miR-126, miR-130a, and miR-378 helps predict MACCE risk in ULMCAD patients who underwent CABG.

Comparison of Intramyocardial and Intravenous Routes of Delivering Bone Marrow Cells for the Treatment of Ischemic Heart Disease: An Experimental Study

The implantation of bone marrow cells (BMCs) into ischemic heart after myocardial infarction can induce angiogenesis and improve heart function. We compared the advantages of delivering BMCs intramyocardially and intravenously. An acute myocardial infarction model was created by the ligation of left anterior descending artery in female Dark Agouti rats. The rats were then randomly divided into four treatment groups: one given an intramyocardial injection of phosphate-buffered saline (PBS group), one given an intravenous injection of 2 × 107 BMCs from male rats (IV group), one given an intramyocardial injection with total of 2 × 107 BMCs from male rats at four points in the infarction area (IM group), and one given an intravenous injection of 10-fold the number of BMCs from male rats (10xIV group). Quantitative analysis of the SRY gene by real-time PCR showed that the survival of BMCs in the infarcted area was significantly higher in the IM group than in the IV and 10xIV groups, 3 days after treatment (p < 0.05), but not thereafter. However, the blood flow in the infarcted myocardium was significantly better in the IM and 10xIV groups than in the PBS and IV groups 14 days after treatment (p < 0.05). Echocardiography showed that the LVEF continued to decrease in the PBS and IV groups, but was stable after 3 days in the IM and 10xIV groups. By 14 days after treatment, the LVEF was significantly higher in the IM and 10xIV groups than in the PBS and IV groups (p < 0.01). Our results showed that BMCs were more effective delivered intramyocardially than intravenously for inducing angiogenesis and repairing injured myocardium.

Distinct Expression of Various Angiogenesis Factors in Mice Brain After Whole-Brain Irradiation by X-ray

Radiation-induced brain injury (RBI) is the most serious complication after radiotherapy. However, the etiology of RBI remains elusive. In order to evaluate the effect of X-rays on normal brain tissue, adult male BALB/C mice were subjected to whole-brain exposure with a single dose of 10 Gy or sham radiation. The structure and number of mice brain vessels were investigated 1, 7, 30, 90 and 180 days after irradiation by H&E staining and immune-fluorescence staining. Compared with sham control mice, in addition to morphological changes, a significant reduction of microvascular density was detected in irradiated mice brains. Whole-brain irradiation also caused damage in tight junction (TJ). Increased expression of glial fibrillary acidic protein (GFAP) and vascular endothelial growth factor (VEGF) was observed in irradiated mouse brains showed by Western Blot. Immune-fluorescence staining results also verified the co-labeling of GFAP and VEGF after whole-brain irradiation. Furthermore, the protein expression levels of other angiogenesis factors, angiopoietin-1 (Ang-1), endothelial-specific receptor tyrosine kinase (Tie-2), and angiopoietin-2 (Ang-2) in brain were determined by Western Blot. Increased expression of Ang-2 was shown in irradiated mouse brains. In contrast, whole-brain irradiation significantly decreased Ang-1 and Tie-2 expression. Our data indicated that X-rays induced time-dependent microvascular injury and activation of astrocytes after whole-brain irradiation in mouse brain. Distinct regulation of VEGF/Ang2 and Ang-1/Tie-2 are closely associated with RBI, suggesting that angiogenesis interventions might be beneficial for patients with RBI.

Nanoparticle drug delivery systems and their use in cardiac tissue therapy

Cardiovascular diseases make up one of the main causes of death today, with myocardial infarction and ischemic heart disease contributing a large share of the deaths reported. With mainstream clinical therapy focusing on palliative medicine following myocardial infarction, the structural changes that occur in the diseased heart will eventually lead to end-stage heart failure. Heart transplantation remains the only gold standard of cure but a shortage in donor organs pose a major problem that led to clinicians and researchers looking into alternative strategies for cardiac repair. This review will examine some alternative methods of treatment using chemokines and drugs carried by nanoparticles as drug delivering agents for the purposes of treating myocardial infarction through the promotion of revascularization. We will also provide an overview of existing studies involving such nanoparticulate drug delivery systems, their reported efficacy and the challenges facing their translation into ubiquitous clinical use.

Strategies for the chemical and biological functionalization of scaffolds for cardiac tissue engineering: a review

The development of biomaterials for cardiac tissue engineering (CTE) is challenging, primarily owing to the requirement of achieving a surface with favourable characteristics that enhances cell attachment and maturation. The biomaterial surface plays a crucial role as it forms the interface between the scaffold (or cardiac patch) and the cells. In the field of CTE, synthetic polymers (polyglycerol sebacate, polyethylene glycol, polyglycolic acid, poly-l-lactide, polyvinyl alcohol, polycaprolactone, polyurethanes and poly(N-isopropylacrylamide)) have been proven to exhibit suitable biodegradable and mechanical properties. Despite the fact that they show the required biocompatible behaviour, most synthetic polymers exhibit poor cell attachment capability. These synthetic polymers are mostly hydrophobic and lack cell recognition sites, limiting their application. Therefore, biofunctionalization of these biomaterials to enhance cell attachment and cell material interaction is being widely investigated. There are numerous approaches for functionalizing a material, which can be classified as mechanical, physical, chemical and biological. In this review, recent studies reported in the literature to functionalize scaffolds in the context of CTE, are discussed. Surface, morphological, chemical and biological modifications are introduced and the results of novel promising strategies and techniques are discussed.

Angiogenic therapy for cardiac repair based on protein delivery systems

Cardiovascular diseases remain the first cause of morbidity and mortality in the developed countries and are a major problem not only in the western nations but also in developing countries. Current standard approaches for treating patients with ischemic heart disease include angioplasty or bypass surgery. However, a large number of patients cannot be treated using these procedures. Novel curative approaches under investigation include gene, cell, and protein therapy. This review focuses on potential growth factors for cardiac repair. The role of these growth factors in the angiogenic process and the therapeutic implications are reviewed. Issues including aspects of growth factor delivery are presented in relation to protein stability, dosage, routes, and safety matters. Finally, different approaches for controlled growth factor delivery are discussed as novel protein delivery platforms for cardiac regeneration.

Biodegradable collagen patch with covalently immobilized VEGF for myocardial repair

Vascularization of engineered tissues in vitro and in vivo remains a key problem in translation of engineered tissues to clinical practice. Growth factor signalling can be prolonged by covalent tethering, thus we hypothesized that covalent immobilization of vascular endothelial growth factor (VEGF-165) to a porous collagen scaffold will enable rapid vascularization in vivo. Covalent immobilization may be preferred over controlled release or cell transfection if the effects are desired within the biomaterial rather than the surrounding tissue. Scaffolds were prepared with 14.5 ± 1.4 ng (Low) or 97.2 ± 8.0 ng (High) immobilized VEGF, or left untreated (control), and used to replace a full right ventricular free wall defect in rat hearts. In addition to rapid vascularization, an effective cardiac patch should exhibit neither thinning nor dilatation upon implantation. In vitro, VEGF enhanced the growth of endothelial and bone marrow cells seeded onto scaffolds. In vivo, High VEGF patches had greater blood vessel density (p < 0.01) than control at Day 7 and 28 due to increased cell recruitment and proliferation (p < 0.05 vs. control). At Day 28, VEGF-treated patches were significantly thicker (p < 0.05) than control, and thickness correlated positively with neovascularization (r = 0.67, p = 0.023). Importantly, angiogenesis in VEGF scaffolds contributed to improved cell survival and tissue formation.

Defining conditions for covalent immobilization of angiogenic growth factors onto scaffolds for tissue engineering

Rapid vascularization of engineered tissues in vitro and in vivo remains one of the key limitations in tissue engineering. We propose that angiogenic growth factors covalently immobilized on scaffolds for tissue engineering can be used to accomplish this goal. The main objectives of this work were: (a) to derive desirable experimental conditions for the covalent immobilization of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1) on porous collagen scaffolds; and (b) to determine whether primary endothelial cells respond to these scaffolds with covalently immobilized angiogenic factors. VEGF and Ang1 were covalently immobilized onto porous collagen scaffolds, using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) chemistry. To improve covalent immobilization conditions: (a) different reaction buffers [phosphate-buffered saline (PBS), distilled water, or 2-(N-morpholino)ethanesulphonic acid (MES)] were used; and (b) step immobilization was compared to bulk immobilization. In step immobilization, growth factors are applied after EDC activation of the scaffold, while in bulk immobilization, reagents are simultaneously applied to the scaffold. PBS as the reaction buffer resulted in higher amounts of VEGF and Ang1 immobilized (ELISA), higher cell proliferation rates (XTT) and increased lactate metabolism compared to water and MES as the reaction buffers. Step immobilization in PBS buffer was also more effective than bulk immobilization. Immobilized growth factors resulted in higher cell proliferation and lactate metabolism compared to soluble growth factors used at comparable concentrations. Tube formation by CD31-positive cells was also observed in collagen scaffolds with immobilized VEGF or Ang1 using H5V and primary rat aortic endothelial cells but not on control scaffolds.

Scaffolds with covalently immobilized VEGF and Angiopoietin-1 for vascularization of engineered tissues

The aim of this study was to engineer a biomaterial capable of supporting vascularization in vitro and in vivo. We covalently immobilized vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang1) onto three-dimensional porous collagen scaffolds using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) chemistry. Over both 3 and 7 days in vitro, seeded endothelial cells (ECs) had increased proliferation on scaffolds with immobilized VEGF and/or Ang1 compared to unmodified scaffolds and soluble growth factor controls. Notably, the group with co-immobilized VEGF and Ang1 showed significantly higher cell number (P=0.0079), higher overall lactate production rate (P=0.0044) and higher overall glucose consumption rate (P=0.0034) at Day 3, compared to its corresponding soluble control for which growth factors were added to culture medium. By Day 7, hematoxylin and eosin, live/dead, CD31, and von Willebrand factor staining all showed improved tube formation by ECs when cultivated on scaffolds with co-immobilized growth factors. Interestingly, scaffolds with co-immobilized VEGF and Ang1 showed increased EC infiltration in the chorioallantoic membrane (CAM) assay, compared to scaffolds with independently immobilized VEGF/Ang1. This study presents an alternative method for promoting the formation of vascular structures, via covalent immobilization of angiogenic growth factors that are more stable than soluble ones and have a localized effect.

MicroRNAs in Cardiovascular Biology and Heart Disease

MicroRNAs play important roles in many cellular and biological functions via the regulation of mRNA target translation. In the cardiovascular field, microRNAs are now acknowledged as fundamental in regulating the expression of genes that governs physiological and pathological myocardial adaptation to stress. Here, we review recent progress in the understanding of microRNA functions and their involvement in heart disease.

Hypoxia-specific gene expression for ischemic disease gene therapy

Gene therapy for ischemic diseases has been developed with various growth factors and anti-apoptotic genes. However, non-specific expression of therapeutic genes may induce deleterious side effects such as tumor formation. Hypoxia-specific regulatory systems can be used to regulate transgene expression in hypoxic tissues, in which gene expression is induced in ischemic tissues, but reduced in normal tissues by transcriptional, translational or post-translational regulation. Since hypoxia-inducible factor 1 (HIF-1) activates transcription of genes in hypoxic tissues, it can play an important role in the prevention of myocardial and cerebral ischemia. Hypoxia-specific promoters including HIF-1 binding sites have been used for transcriptional regulation of therapeutic genes. Also, hypoxia-specific untranslated regions (UTRs) and oxygen dependent degradation (ODD) domains have been investigated for translational and post-translational regulations, respectively. Hypoxia-specific gene expression systems have been applied to various ischemic disease models, including ischemic myocardium, stroke, and injured spinal cord. This review examines the current status and future challenges of hypoxia-specific systems for safe and effective gene therapy of ischemic diseases.

Mesenchymal Stem Cells Genetically Modified with the Angiopoietin-1 Gene Enhanced Arteriogenesis in a Porcine Model of Chronic Myocardial Ischaemia

The direct injection by thoracoscope of mesenchymal stem cells (MSCs) that had been genetically modified to express angiopoietin-1 was investigated in a porcine model to determine their effect on arteriogenesis and the effectiveness of this technique. Chronic myocardial ischaemia was established using a thoracoscope to insert an ameroid constrictor around the left circumflex coronary artery. Six weeks after establishing the ischaemia, 20 pigs were randomly divided into three groups to receive injections by thoracoscope of either genetically-modified MSCs, unmodified MSCs or phosphate-buffered saline into the ischaemic border area. The injections were repeated 1 month later. The genetically modified MSCs were found to restore blood flow significantly more than the other observed treatments and immunohistochemical evaluation of arteriogenesis supported this finding. In conclusion, the injection of MSCs that had been genetically modified to express angiopoietin-1 improved arteriogenesis and increased collateral blood flow in the myocardial ischaemic area. Thoracoscope delivery of the injection was safe and minimally invasive.

Toward microRNA-based therapeutics for heart disease: the sense in antisense

MicroRNAs act as negative regulators of gene expression by inhibiting the translation or promoting the degradation of target mRNAs. Because individual microRNAs often regulate the expression of multiple target genes with related functions, modulating the expression of a single microRNA can, in principle, influence an entire gene network and thereby modify complex disease phenotypes. Recent studies have identified signature expression patterns of microRNAs associated with pathological cardiac hypertrophy, heart failure, and myocardial infarction in humans and mouse models of heart disease. Gain- and loss-of-function studies in mice have revealed profound and unexpected functions for these microRNAs in numerous facets of cardiac biology, including the control of myocyte growth, contractility, fibrosis, and angiogenesis, providing glimpses of new regulatory mechanisms and potential therapeutic targets for heart disease. Especially intriguing is the discovery of a network of muscle-specific microRNAs embedded within myosin heavy chain genes, which control myosin expression and the response of the heart to stress and thyroid hormone signaling. Disease-inducing cardiac microRNAs can be persistently silenced in vivo through systemic delivery of antimiRs, allowing for the direct therapeutic modulation of disease mechanisms. Here, we summarize current knowledge of the roles of miRNAs in heart disease and consider the advantages and potential challenges of microRNA-based approaches compared to conventional drug-based therapies.

The endothelial-specific microRNA miR-126 governs vascular integrity and angiogenesis

Endothelial cells play essential roles in maintenance of vascular integrity, angiogenesis, and wound repair. We show that an endothelial cell-restricted microRNA (miR-126) mediates developmental angiogenesis in vivo. Targeted deletion of miR-126 in mice causes leaky vessels, hemorrhaging, and partial embryonic lethality, due to a loss of vascular integrity and defects in endothelial cell proliferation, migration, and angiogenesis. The subset of mutant animals that survives displays defective cardiac neovascularization following myocardial infarction. The vascular abnormalities of miR-126 mutant mice resemble the consequences of diminished signaling by angiogenic growth factors, such as VEGF and FGF. Accordingly, miR-126 enhances the proangiogenic actions of VEGF and FGF and promotes blood vessel formation by repressing the expression of Spred-1, an intracellular inhibitor of angiogenic signaling. These findings have important therapeutic implications for a variety of disorders involving abnormal angiogenesis and vascular leakage.

Long-term effect of gene therapy for chronic ischemic myocardium using platelet-derived endothelial cell growth factor in dogs

BACKGROUND

We previously reported the 2-week benefits of platelet-derived endothelial cell growth factor (PD-ECGF) gene therapy in chronically ischemic myocardium. However, the long-term effects and safety using this gene have not been reported.

METHODS

Chronic myocardial ischemia was created in 24 dogs by stenosing the origin of the left anterior descending coronary artery (LAD) using an ameroid constrictor. Two weeks later, the PD-ECGF gene, the LacZ gene, or saline was infused directly into the myocardium in the LAD area. The myocardial blood volume and myocardial function were examined prior to ischemia, immediately before gene injection, and for 6 months following injection, and then the organs were harvested for histological and molecular examination.

RESULTS

PD-ECGF gene treatment significantly attenuated endocardial infarction at 6 months. Myocardial blood volume and myocardial function decreased in all three groups after ameroid implantation, but recovered after 2 weeks in the PD-ECGF-treated group, and maintained a higher level of function during the examination period. Histological analysis demonstrated that angiogenesis and arteriogenesis occurred after PD-ECGF gene treatment. There was a decreased expression of the pro-apoptotic proteins, active caspase-3 and Bax, and the number of apoptotic myocardial cells was lower in the PD-ECGF-treated group. Histological examination demonstrated that no abnormal histological changes or neoplasms were found in any organs.

CONCLUSIONS

We conclude that gene targeting of ischemic myocardium using PD-ECGF generated long-term improvement in cardiac function by causing angiogenesis, arteriogenesis and inhibiting apoptosis, but did not induce neoplasms in the remote organs, and may be a promising therapy.

Therapeutic opportunities in biological responses of ultrasound

The therapeutic benefits of several existing ultrasound-based therapies such as facilitated drug delivery, tumor ablation and thrombolysis derive largely from physical or mechanical effects. In contrast, ultrasound can also trigger various time-dependent biochemical responses in the exposed biological milieu. Several biological responses to ultrasound exposure have been previously described in the literature but only a handful of these provide therapeutic opportunities. These include the use of ultrasound for healing of soft tissues and bones, the use of ultrasound for inducing non-necrotic tumor atrophy as well as for potentiation of chemotherapeutic drugs, activation of the immune system, angiogenesis and suppression of phagocytosis. A review of these therapeutic opportunities is presented with particular emphasis on their mechanisms. Overall, this review presents the increasing importance of ultrasound's role as a biological sensitizer enabling novel therapeutic strategies.

Transcriptional and post-translational regulatory system for hypoxia specific gene expression using the erythropoietin enhancer and the oxygen-dependent degradation domain

Gene therapy with angiogenic factors is a promising strategy for the treatment of ischemic diseases. However, unregulated expression of an angiogenic factor may induce pathological angiogenesis. In this study, a hypoxia specific gene expression plasmid, pSV-Luc-ODD, was constructed with the oxygen-dependent degradation (ODD) domain for rapid degradation of a target protein under normoxia. In the transfection assay, luciferase activity in the pSV-Luc-ODD transfected cells was much lower under normoxia than that under hypoxia. However, the luciferase mRNA levels under hypoxia and normoxia were not significantly different. Therefore, decrease of luciferase activity under normoxia is not due to pre-translational events such as change of transcription rate or mRNA stability, but to post-translational degradation. For more hypoxia specific gene expression, pEpo-SV-Luc-ODD was constructed with the erythropoietin (Epo) enhancer and the ODD domain. pEpo-SV-Luc-ODD showed more than 1000 times increase of gene expression under hypoxia in Neuro2A cells, compared to normoxia. In addition, reoxygenation studies after hypoxia incubation showed that gene expression was decreased in response to increased oxygen concentration. This highly hypoxia specific gene expression system will be useful for development of targeting gene therapy for ischemic diseases.

Ultrasound-induced cavitation: applications in drug and gene delivery

Ultrasound, which has been conventionally used for diagnostics until recently, is now being extensively used for drug and gene delivery. This transformation has come about primarily due to ultrasound-mediated acoustic cavitation - particularly transient cavitation. Acoustic cavitation has been used to facilitate the delivery of small molecules, as well as macromolecules, including proteins and DNA. Controlled generation of cavitation has also been used for targeting drugs to diseased tissues, including skin, brain, eyes and endothelium. Ultrasound has also been employed for the treatment of several diseases, including thromboembolism, arteriosclerosis and cancer. This review provides a detailed account of mechanisms, current status and future prospects of ultrasonic cavitation in drug and gene delivery applications.

Hypoxia-inducible gene expression system using the erythropoietin enhancer and 3′-untranslated region for the VEGF gene therapy

Gene therapy with the vascular endothelial growth factor (VEGF) gene is a potential treatment for many disorders or injuries with ischemia. However, unregulated expression of VEGF may induce pathological angiogenesis, promoting tumor growth, diabetic proliferative retinopathy and rupture of atherosclerotic plaque. Therefore, the effective regulation of the gene expression is one of the requirements for the VEGF gene therapy. In this research, we evaluated the hypoxia-inducible gene expression system with the erythropoietin (Epo) enhancer and the Epo 3'-untranslated region (UTR). The luciferase plasmids were constructed with the Epo enhancer (pEpo-SV-Luc), the Epo 3'-UTR (pSV-Luc-EpoUTR) or both (pEpo-SV-Luc-EpoUTR). The polyethylenimine/plasmid complexes were transfected to 293 or A7R5 cells and the cells were incubated under normoxia or hypoxia. The results showed that the Epo enhancer or Epo 3'-UTR increased the target gene expression under hypoxia. pEpo-SV-Luc-EpoUTR showed the highest luciferase expression. The VEGF expression plasmid with the Epo enhancer and 3'-UTR was also constructed. The VEGF expression by pEpo-SV-VEGF-EpoUTR showed the highest specificity of the gene expression in the hypoxic cells. The results suggest that the VEGF plasmid with the Epo enhancer and the Epo 3'-UTR may be useful for gene therapy for ischemic diseases.

Identification of Sokotrasterol Sulfate As a Novel Proangiogenic Steroid

The potential to promote neovascularization in ischemic tissues using exogenous agents has become an exciting area of therapeutics. In an attempt to identify novel small molecules with angiogenesis promoting activity, we screened a library of natural products and identified a sulfated steroid, sokotrasterol sulfate, that induces angiogenesis in vitro and in vivo. We show that sokotrasterol sulfate promotes endothelial sprouting in vitro, new blood vessel formation on the chick chorioallantoic membrane, and accelerates angiogenesis and reperfusion in a mouse hindlimb ischemia model. We demonstrate that sulfation of the steroid is critical for promoting angiogenesis, as the desulfated steroid exhibited no endothelial sprouting activity. We thus developed a chemically synthesized sokotrasterol sulfate analog, 2beta,3alpha,6alpha-cholestanetrisulfate, that demonstrated equivalent activity in the hindlimb ischemia model and resulted in the generation of stable vessels that persisted following cessation of therapy. The function of sokotrasterol sulfate was dependent on cyclooxygenase-2 activity and vascular endothelial growth factor induction, as inhibition of either cyclooxygenase-2 or vascular endothelial growth factor blocked angiogenesis. Surface expression of alpha(v)beta(3) integrin was also necessary for function, as neutralization of alpha(v)beta(3) integrin, but not beta(1) integrin, binding abrogated endothelial sprouting and antiapoptotic activity in response to sokotrasterol sulfate. Our findings indicate that sokotrasterol sulfate and its analogs can promote angiogenesis in vitro and in vivo and could potentially be used for promoting neovascularization to relieve the sequelae of vasoocclusive diseases.

Angiogenic and antiangiogenic gene therapy

Gene therapy is thought to be a promising method for the treatment of various diseases. One gene therapy strategy involves the manipulations on a process of formation of new vessels, commonly defined as angiogenesis. Angiogenic and antiangiogenic gene therapy is a new therapeutic approach to the treatment of cardiovascular and cancer patients, respectively. So far, preclinical and clinical studies are successfully focused mainly on the treatment of coronary artery and peripheral artery diseases. Plasmid vectors are often used in preparations in angiogenic gene therapy trials. The naked plasmid DNA effectively transfects the skeletal muscles or heart and successfully expresses angiogenic genes that are the result of new vessel formation and the improvement of the clinical state of patients. The clinical preliminary data, although very encouraging, need to be well discussed and further study surely continued. It is really possible that further development of molecular biology methods and advances in gene delivery systems will cause therapeutic angiogenesis as well as antiangiogenic methods to become a supplemental or alternative option to the conventional methods of treatment of angiogenic diseases.

Angiogenesis and arteriogenesis are increased in fibrin gel chambers implanted in prehypertensive spontaneously hypertensive rats

OBJECTIVE

Microvascular rarefaction by an unbalanced angiogenesis could promote the onset of hypertension in spontaneously hypertensive rats and in hypertensive patients. We studied the angiogenic potency in the fibrin gel chamber model in prehypertensive spontaneously hypertensive rats and their controls, Wistar-Kyoto rats.

METHODS

Four-week-old prehypertensive spontaneously hypertensive rats (n = 9) and Wistar-Kyoto rats (n = 9) were implanted with four fibrin gel chambers located in the dorsal subcutaneous space. After 14 days, vasculoconjunctive buds had invaded the fibrin gel through the 10 hole-perforated bottom slip of the chamber. The intact vascular buds were studied using optical microscopy, alpha-actin and von Willebrand factor stainings. Capillaries and arterialized vessels were counted in three peripheral and one central field in each bud. The immunodetection of vascular endothelial growth factor and fibroblast growth factor 2 was performed on the neovascular buds.

RESULTS

In fibrin chambers implanted in spontaneously hypertensive rats, the number of peripheral vessels was significantly higher than in Wistar-Kyoto rats. There were significantly more arterialized vessels in spontaneously hypertensive rats compared with Wistar-Kyoto rats. The number of immunostained cells for fibroblast growth factor 2 was significantly greater in spontaneously hypertensive rats compared with Wistar-Kyoto rats. There was no significant difference in vascular endothelial growth factor staining between the two strains of rats.

CONCLUSION

Angiogenesis and arteriogenesis are increased in fibrin chambers implanted in prehypertensive spontaneously hypertensive rats compared with Wistar-Kyoto rats. These results argue against microvascular rarefaction as a cause of hypertension using this model of angiogenesis.

Angiogenesis is confined to the transient period of VEGF expression that follows adenoviral gene delivery to ischemic muscle

Therapeutic angiogenesis involves the introduction of exogenous growth factor proteins and genes into ischemic tissues to augment endogenous factors and promote new vessel growth. Positive results from studies in animal models of peripheral arterial disease (PAD) and coronary artery disease over the past decade have supported the implementation of clinical trials testing vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) proteins and genes. Although several clinical trials reported positive results, others have been disappointing and results of a recent Phase II trial of VEGF delivered by adenovirus (the RAVE trial) were negative. It has been suggested that the duration of gene expression following delivery by adenovirus may be insufficient to produce stable vessels. Here we present direct evidence in support of this using the rabbit ischemic hindlimb model injected with adenovirus encoding VEGF165. Immunohistology indicated an activation of endothelial cell cycling and proliferation 2-3 days after VEGF delivery that coincided closely with transient VEGF expression. Ki-67-positive endothelial nuclei were evident at high levels in capillaries and large vessels in muscles from treated animals. Angiography indicated increased density of both large and small vessels in Ad-VEGF-treated muscle at 1 week, but no significant differences thereafter. The early burst of endothelial proliferation was accompanied by increased nuclear fragmentation and condensation in VEGF-treated muscles, suggesting coincident apoptosis. No further endothelial cell proliferation took place after 1 week although there was still evidence of apoptosis. The results suggest that angiogenesis is confined to the short period of VEGF expression produced by adenovirus and early gains in collateralization rapidly regress to control levels when VEGF production ceases.

Ultrastructure and histochemistry of rat myocardial capillary endothelial cells in response to diabetes and hypertension

Insufficient growth and rarefaction of capillaries, followed by endothelial dysfunction may represent one of the most critical mechanisms involved in heart damage. In this study we examined histochemical and ultrastructural changes in myocardial capillary endothelium in two models of heart failure streptozotocin-induced diabetes mellitus (STZ) and NO-deficient hypertension in male Wistar rats. Diabetes was induced by a single i.v. dose of STZ (45 mg/kg) and chronic 9-week stage was analysed. To induce NO-deficient hypertension, animals were treated with inhibitor of NO synthase L-nitroarginine methylester (L-NAME) (40 mg/kg) for 4 weeks. Left ventricular tissue was processed for enzyme catalytic histochemistry of capillary alkaline phosphatase (AlPh), dipeptidyl peptidase IV (DPP IV), and endothelial NO synthase/NADPH-diaphorase (NOS) and for ultrastructural analysis. In diabetic and hypertensive rats, lower/absent AlPh and DPP IV activities were found in focal micro-areas. NOS activity was significantly reduced and persisted only locally. Quantitative evaluation demonstrated reduction of reaction product intensity of AlPh, DPP and NOS by 49.50%, 74.36%, 20.05% in diabetic and 62.93%, 82.71%, 37.65% in hypertensive rats. Subcellular alterations of endothelial cells were found in heart of both groups suggesting injury of capillary function as well as compensatory processes. Endothelial injury was more significant in diabetic animals, in contrast the adaptation was more evident in hypertensive ones. CONCLUDING: both STZ-induced diabetes- and NO-deficient hypertension-related cardiomyopathy were accompanied by similar features of structural remodelling of cardiac capillary network manifested as angiogenesis and angiopathy. The latter was however, predominant and may accelerate disappearance of capillary endothelium contributing to myocardial dysfunction.

Reappraisal of recent clinical trials of angiogenic therapy in myocardial ischemia

We review the clinical trials of angiogenic therapy for myocardial ischemia, focusing on why the results are unsatisfactory in more recent larger and better designed trials. Critical reappraisal of such trials, in view of the pathophysiologic complexity of the angiogenic process at a molecular level, suggests that the strategy of therapies based on a single growth factor protein or gene may not be adequate for optimal therapeutic response.

Quantitative proteomic analysis of sokotrasterol sulfate-stimulated primary human endothelial cells

The endothelium forms a continuous monolayer at the interface between blood and tissue and contributes significantly to the sensing and transducing of signals between blood and tissue. New blood vessel formation, or angiogenesis, is initiated by the activation of endothelial cells and is an important process required for various pathological and physiological situations. This study used cleavable isotope-coded affinity tag reagents combined with mass spectrometry to investigate the molecular basis of a recently discovered angiogenesis-promoting steroid, sokotrasterol sulfate. Changes in the relative abundances of over 1000 proteins within human endothelial cells treated with sokotrasterol sulfate and vehicle-treated cells were identified and quantitated using this technique. A method that examines the entire ensemble of quantitative measurements was developed to identify proteins that showed a statistically significant change in relative abundance resulting from treatment with sokotrasterol sulfate. A total of 93 proteins was significantly up-regulated, and 37 were down-regulated in response to sokotrasterol sulfate stimulation of endothelial cells. Among the up-regulated proteins, several were identified that are novel to endothelial cells and are likely involved in cell communication and morphogenesis. These findings are consistent with a role for sokotrasterol sulfate in endothelial sprouting.

Enhanced Protein Profiling Arrays with ELISA-Based Amplification for High-Throughput Molecular Changes of Tumor Patients’ Plasma

PURPOSE

The purpose of this study is to develop a high-throughput approach to detect protein expression from hundreds and thousands of samples and to apply this technology to profile circulating angiogenic factor protein levels in patients with gynecological tumors.

EXPERIMENTAL DESIGN

Analytes containing a mixture of protein are immobilized onto antibody-coated surface of support in array format. The presence of protein in analytes is detected with biotin-labeled antibody coupled with an enhanced chemiluminescence or fluorescence detection system. The exact amount of protein can be quantitatively measured. The expression levels of five angiogenic factors (angiogenin, interleukin 8, vascular endothelial growth factor, platelet-derived growth factor, and epidermal growth factor) from 157 samples were quantitatively measured using this novel protein array technology and were statistically analyzed. The expression patterns of angiogenic factors were analyzed using two-way hierarchical cluster analysis approach.

RESULTS

A novel protein array technology, which can simultaneously and quantitatively measure few protein levels from hundreds and thousands of samples was developed. Only minute amounts of sample are required for the assay. This approach also features high sensitivity and specificity. Using this novel protein array approach, we analyzed the plasma expression levels of five angiogenic factors in 137 patients diagnosed with a tumor and 20 controls. Statistical analysis reveals different expression levels of angiogenic factors between patients and controls. Cluster analysis suggests a possible classification of normal subjects from patients.

CONCLUSIONS

Enhanced protein profiling arrays provide a high-throughput and sensitive system to detect one or few protein from hundreds and thousands of samples. Such an approach should have broad application in biomedical discovery.

HSP90 and Akt modulate Ang-1-induced angiogenesis via NO in coronary artery endothelium

This study examines the notion that heat shock protein (HSP) 90 binding to nitric oxide (NO), endothelial NO synthase (eNOS), and PI3K-Akt regulate angiopoietin (Ang)-1-induced angiogenesis in porcine coronary artery endothelial cells (PCAEC). Exposure to Ang-1 (250 ng/ml) for periods up to 2 h resulted in a time-dependent increase in eNOS phosphorylation at Ser 1177 that occurred by 5 min and peaked at 60 min. This was accompanied by a gradual increase in NO release. Ang-1 also led to stimulation of HSP90 binding to eNOS and a significant increase in Akt phosphorylation. Thirty minutes of pretreatment of cells with either 1 microg/ml geldanamycin (a specific inhibitor of HSP90) or 500 nM wortmannin [a specific phosphatidylinositol 3 (PI3)-kinase (PI3K) inhibitor] significantly attenuated Ang-1-stimulated eNOS phosphorylation and NO production. Exposure to Ang-1 caused an increase in endothelial cell migration, tube formation, and sprouting from PCAEC spheroids, and pharmacological blockage of HSP90 function or inhibition of PI3K-Akt pathway completely abolished these effects. Inhibition of nitric oxide synthase by NG-nitro-l-arginine methyl ester (2.5 mM) also resulted in a significant decrease in Ang-1-induced angiogenesis. We conclude that stimulated HSP90 binding to eNOS and activation of the PI3-Akt pathway contribute to Ang-1-induced eNOS phosphorylation, NO production, and angiogenesis in PCAEC.