Therapeutic angiogenesis with recombinant fibroblast growth factor-2 improves stress and rest myocardial perfusion abnormalities in patients with severe symptomatic chronic coronary artery disease

Therapeutic angiogenesis based on injectable hydrogel for protein delivery in ischemic heart disease

Ischemic heart disease (IHD) remains the leading cause of death and disability worldwide and leads to myocardial necrosis and negative myocardial remodeling, ultimately leading to heart failure. Current treatments include drug therapy, interventional therapy, and surgery. However, some patients with severe diffuse coronary artery disease, complex coronary artery anatomy, and other reasons are unsuitable for these treatments. Therapeutic angiogenesis stimulates the growth of the original blood vessels by using exogenous growth factors to generate more new blood vessels, which provides a new treatment for IHD. However, direct injection of these growth factors can cause a short half-life and serious side effects owing to systemic spread. Therefore, to overcome this problem, hydrogels have been developed for temporally and spatially controlled delivery of single or multiple growth factors to mimic the process of angiogenesis in vivo. This paper reviews the mechanism of angiogenesis, some important bioactive molecules, and natural and synthetic hydrogels currently being applied for bioactive molecule delivery to treat IHD. Furthermore, the current challenges of therapeutic angiogenesis in IHD and its potential solutions are discussed to facilitate real translation into clinical applications in the future.

The Association Between Contrast-Enhanced Ultrasound and Near-Infrared Spectroscopy-Derived Measures of Calf Muscle Microvascular Responsiveness in Older Adults

BACKGROUND AND AIM

Contrast-enhanced ultrasound (CEUS) measures of post-occlusion skeletal muscle microvascular responsiveness demonstrate the microvascular dysfunction associated with ageing and age-related disease. However, the accessibility of CEUS is limited by the need for intravenous administration of ultrasound contrast agents and sophisticated imaging analysis. Alternative methods are required for the broader assessment of microvascular dysfunction in research and clinical settings. Therefore, we aimed to evaluate the level of association and agreement between CEUS and near-infrared spectroscopy (NIRS)-derived measures of post-occlusion skeletal muscle microvascular responsiveness in older adults.

METHODS

During supine rest, participants (n=15, 67±11 years) underwent 5 minutes of thigh cuff-occlusion (200 mmHg). Post-occlusion CEUS measures of calf muscle microvascular responsiveness were made, including time to 95% peak acoustic intensity (TTP⁹⁵ AI) and the rate of rise (slope AI). Simultaneous measures, including time to 95% peak oxygenated haemoglobin (TTP⁹⁵ O₂Hb) and slope O₂Hb, were made using continuous-wave NIRS in the same muscle region.

RESULTS

There were strong correlations between TTP⁹⁵ measures derived from CEUS and NIRS (r=0.834, p=<0.001) and the corresponding measures of slope (r=0.735, p=0.004). The limits of agreement demonstrated by Bland Altman plot analyses for CEUS and NIRS-derived measures of TTP⁹⁵ (-9.67-1.98 s) and slope (-1.29-5.23%. s^-1) were smaller than the minimum differences expected in people with microvascular dysfunction.

CONCLUSIONS

The strong correlations and level of agreement in the present study support the use of NIRS as a non-invasive, portable and cost-effective method for assessing post-occlusion skeletal muscle microvascular responsiveness in older adults.

Coronary microvascular adaptations distal to epicardial artery stenosis

Until recently, epicardial coronary stenosis has been considered the primary outcome of coronary heart disease, and clinical interventions have been dedicated primarily to the identification and removal of flow-limiting stenoses. However, a growing body of literature indicates that both epicardial stenosis and microvascular dysfunction contribute to damaging myocardial ischemia. In this review, we discuss the coexistence of macro- and microvascular disease, and how the structure and function of the distal microcirculation is impacted by the hemodynamic consequences of an epicardial, flow-limiting stenosis. Mechanisms of endothelial dysfunction as well as alterations of smooth muscle function in the coronary microcirculation distal to stenosis are discussed. Risk factors including diabetes, metabolic syndrome, and aging exacerbate microvascular dysfunction in the myocardium distal to a stenosis, and our current understanding of the role of these factors in limiting collateralization and angiogenesis of the ischemic myocardium is presented. Importantly, exercise training has been shown to promote collateral growth and improve microvascular function distal to stenosis; thus, the current literature reporting the mechanisms that underlie the beneficial effects of exercise training in the microcirculation distal to epicardial stenosis is reviewed. We also discuss recent studies of therapeutic interventions designed to improve microvascular function and stimulate angiogenesis in clinically relevant animal models of epicardial stenosis and microvascular disease. Finally, microvascular adaptation to removal of epicardial stenosis is considered.

FGF2, an Immunomodulatory Factor in Asthma and Chronic Obstructive Pulmonary Disease (COPD)

The fibroblast growth factor 2 (FGF2) is a potent mitogenic factor belonging to the FGF family. It plays a role in airway remodeling associated with chronic inflammatory airway diseases, including asthma and chronic obstructive pulmonary disease (COPD). Recently, research interest has been raised in the immunomodulatory function of FGF2 in asthma and COPD, through its involvement in not only the regulation of inflammatory cells but also its participation as a mediator between immune cells and airway structural cells. Herein, this review provides the current knowledge on the biology of FGF2, its expression pattern in asthma and COPD patients, and its role as an immunomodulatory factor. The potential that FGF2 is involved in regulating inflammation indicates that FGF2 could be a therapeutic target for chronic inflammatory diseases.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

Engineering a microcirculation for perfusion control of ex vivo-assembled organ systems: Challenges and opportunities

Donor organ shortage remains a clear problem for many end-stage organ patients around the world. The number of available donor organs pales in comparison with the number of patients in need of these organs. The field of tissue engineering proposes a plausible solution. Using stem cells, a patient's autologous cells, or allografted cells to seed-engineered scaffolds, tissue-engineered constructs can effectively supplement the donor pool and bypass other problems that arise when using donor organs, such as who receives the organ first and whether donor organ rejection may occur. However, current research methods and technologies have been unable to successfully engineer and vascularize large volume tissue constructs. This review examines the current perfusion methods for ex vivo organ systems, defines the different types of vascularization in organs, explores various strategies to vascularize ex vivo organ systems, and discusses challenges and opportunities for the field of tissue engineering.

Danshensu accelerates angiogenesis after myocardial infarction in rats and promotes the functions of endothelial progenitor cells through SDF-1α/CXCR4 axis

The present study was performed to investigate the potential role of Danshensu in therapeutic angiogenesis in ischemic myocardium and endothelial progenitor cells (EPCs) function. The rat model of myocardial infarction (MI) injury was induced by left anterior descending coronary artery ligation for 14 days. Danshensu significantly alleviated myocardial ischemia injury by ameliorating left ventricular function and reducing infarct size. Furthermore, Danshensu potentiated post-ischemia neovascularization as evidenced by increased microvessel density in infarction boundary zone, as well as the expression of marker proteins vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Moreover, Danshensu notably promoted stromal cell-derived factor-1α (SDF-1α) level in plasma and C-X-C chemokine receptor type 4 (CXCR4) expression in peri-infarction myocardium, and AMD3100 (CXCR4 antagonist) could reverse the angiogenic and cardioprotective effects of Danshensu. For in vitro study, EPCs were isolated from bone marrow of rats. On the one hand, Danshensu provided significant cytoprotection against hypoxia insult by boosting EPCs viability and inhibiting apoptosis, and upregulated Akt phosphorylation. On the other hand, Danshensu enhanced proangiogenic functions of EPCs on cell migration and tube formation, and increased SDF-1α and CXCR4 expression. Likewise, the cytoprotection and proangiogenic functions of Danshensu on EPCs were partly negated by LY294002 (PI3K antagonist) and CXCR4 siRNA, respectively. Taken together, our results suggested that the cardioprotection of Danshensu in MI rats may be related to promoting myocardial neovascularization. The possible mechanisms may involve improving EPCs survival in hypoxia condition through Akt phosphorylation, and accelerating EPCs proangiogenic functions through SDF-1α/CXCR4 axis.

A novel targeted angiogenesis technique using VEGF conjugated magnetic nanoparticles and in-vitro endothelial barrier crossing

Background

Vascular endothelial growth factor is well known for its angiogenesis potential. The study was performed to determine the possible pro-angiogenic role of magnetic nanoparticles coupled to VEGF in vitro and their capacity to cross an endothelial monolayer. This novel treatment technique for angiogenesis could be potentially useful for therapeutic purposes using magnetic nanoparticles.

Methods

Magnetic nanoparticles (MN) were synthesized and were conjugated with the vascular endothelial growth factor. The particles were tested in vitro in a 2D to 3D culture system. MN was seeded in different positions in relation to an HUVEC spheroid to assess a preferential migration.

To evaluate the MN capacity to cross the endothelial barrier, a confluent monolayer of HUVEC cells was seeded on top of a collagen gel. MN was placed in dissolution on the cell culture media, and the MN position was determined by confocal microscopy for 24 h.

Results

HUVEC spheroids were able to generate a preferential sprouting depending on the MN position. Meanwhile, there was random migration when the MN’s were placed all over the collagen gel and no sprouting when no MN was added. The trans-endothelial migration capacity of the MN was observed after 20 h in culture in the absence of external stimuli.

Conclusion

Here we show in vitro angiogenesis following the distribution of the MN conjugated with growth factors. These nanoparticles could be controlled with a magnet to place them in the ischemic area of interest and speed up vascular recovery. Also, MN has potentials to cross endothelium, opening the doors to a possible intravascular and extravascular treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-017-0643-x) contains supplementary material, which is available to authorized users.

Angiogenesis: Bench to Bedside, Have We Learned Anything?

End-stage ischemic cardiomyopathy patients are an ever-increasing group of coronary artery disease patients, often with no options in our current treatment armamentarium. Angiogenesis therapy pre-clinical and phase I clinical trials showed great promise, however, the benefits of single growth factor treatments have not been borne out in the larger phase II randomized trials. The complexity of angiogenesis process and the challenges in creating animal models to replicate and study this process in ischemic adult human myocardium have been major limitations to progress in this field. In addition failure to control for the powerful placebo effect in the clinical trials and inadequate methods of outcomes measures assessment have created difficult to overcome road blocks in establishing the efficacy of angiogenic strategies. Herein we review the challenges of angiogenesis research and development of treatment strategies. We also propose a structured model for further investigations of angiogenic therapies. The adherence to such a regimented approach as proposed here is, in our opinion, the only way to achieve success in angiogenesis approach development to treatment of patients with end-stage cardiac ischemia refractory to other established therapies.

Catheter-based Intramyocardial Injection of FGF1 or NRG1-loaded MPs Improves Cardiac Function in a Preclinical Model of Ischemia-Reperfusion

Cardiovascular protein therapeutics such as neuregulin (NRG1) and acidic-fibroblast growth factor (FGF1) requires new formulation strategies that allow for sustained bioavailability of the drug in the infarcted myocardium. However, there is no FDA-approved injectable protein delivery platform due to translational concerns about biomaterial administration through cardiac catheters. We therefore sought to evaluate the efficacy of percutaneous intramyocardial injection of poly(lactic-co-glycolic acid) microparticles (MPs) loaded with NRG1 and FGF1 using the NOGA MYOSTAR injection catheter in a porcine model of ischemia-reperfusion. NRG1- and FGF1-loaded MPs were prepared using a multiple emulsion solvent-evaporation technique. Infarcted pigs were treated one week after ischemia-reperfusion with MPs containing NRG1, FGF1 or non-loaded MPs delivered via clinically-translatable percutaneous transendocardial-injection. Three months post-treatment, echocardiography indicated a significant improvement in systolic and diastolic cardiac function. Moreover, improvement in bipolar voltage and decrease in transmural infarct progression was demonstrated by electromechanical NOGA-mapping. Functional benefit was associated with an increase in myocardial vascularization and remodeling. These findings in a large animal model of ischemia-reperfusion demonstrate the feasibility and efficacy of using MPs as a delivery system for growth factors and provide strong evidence to move forward with clinical studies using therapeutic proteins combined with catheter-compatible biomaterials.

Glypican-1 nanoliposomes for potentiating growth factor activity in therapeutic angiogenesis

Therapeutic angiogenesis is a highly appealing concept for treating tissues that become ischemic due to vascular disease. A major barrier to the clinical translation of angiogenic therapies is that the patients that are in the greatest need of these treatments often have long term disease states and co-morbidities, such as diabetes and obesity, that make them resistant to angiogenic stimuli. In this study, we identified that human patients with type 2 diabetes have reduced levels of glypican-1 in the blood vessels of their skin. The lack of this key co-receptor in the tissue may make the application of exogenous angiogenic growth factors or cell therapies ineffective. We created a novel therapeutic enhancer for growth factor activity consisting of glypican-1 delivered in a nanoliposomal carrier (a "glypisome"). Here, we demonstrate that glypisomes enhance FGF-2 mediated endothelial cell proliferation, migration and tube formation. In addition, glypisomes enhance FGF-2 trafficking by increasing both uptake and endosomal processing. We encapsulated FGF-2 or FGF-2 with glypisomes in alginate beads and used these to deliver localized growth factor therapy in a murine hind limb ischemia model. Co-delivery of glypisomes with FGF-2 markedly increased the recovery of perfusion and vessel formation in ischemic hind limbs of wild type and diabetic mice in comparison to mice treated with FGF-2 alone. Together, our findings support that glypisomes are effective means for enhancing growth factor activity and may improve the response to local angiogenic growth factor therapies for ischemia.

Role of fibroblast growth factors in organ regeneration and repair

In its broad sense, regeneration refers to the renewal of lost cells, tissues or organs as part of the normal life cycle (skin, hair, endometrium etc.) or as part of an adaptive mechanism that organisms have developed throughout evolution. For example, worms, starfish and amphibians have developed remarkable regenerative capabilities allowing them to voluntarily shed body parts, in a process called autotomy, only to replace the lost parts afterwards. The bizarre myth of the fireproof homicidal salamander that can survive fire and poison apple trees has persisted until the 20th century. Salamanders possess one of the most robust regenerative machineries in vertebrates and attempting to draw lessons from limb regeneration in these animals and extrapolate the knowledge to mammals is a never-ending endeavor. Fibroblast growth factors are potent morphogens and mitogens that are highly conserved among the animal kingdom. These growth factors play key roles in organogenesis during embryonic development as well as homeostatic balance during postnatal life. In this review, we provide a summary about the current knowledge regarding the involvement of fibroblast growth factor signaling in organ regeneration and repair. We also shed light on the use of these growth factors in previous and current clinical trials in a wide array of human diseases.

Molecular imaging of angiogenesis after myocardial infarction by (111)In-DTPA-cNGR and (99m)Tc-sestamibi dual-isotope myocardial SPECT

Background

CD13 is selectively upregulated in angiogenic active endothelium and can serve as a target for molecular imaging tracers to non-invasively visualise angiogenesis in vivo. Non-invasive determination of CD13 expression can potentially be used to monitor treatment response to pro-angiogenic drugs in ischemic heart disease. CD13 binds peptides and proteins through binding to tripeptide asparagine-glycine-arginine (NGR) amino acid residues.

Previous studies using in vivo fluorescence microscopy and magnetic resonance imaging indicated that cNGR tripeptide-based tracers specifically bind to CD13 in angiogenic vasculature at the border zone of the infarcted myocardium.

In this study, the CD13-binding characteristics of an ¹¹¹In-labelled cyclic NGR peptide (cNGR) were determined. To increase sensitivity, we visualised ¹¹¹In-DTPA-cNGR in combination with ^99mTc-sestamibi using dual-isotope SPECT to localise CD13 expression in perfusion-deficient regions.

Methods

Myocardial infarction (MI) was induced in Swiss mice by ligation of the left anterior descending coronary artery (LAD). ¹¹¹In-DTPA-cNGR and ^99mTc-sestamibi dual-isotope SPECT imaging was performed 7 days post-ligation in MI mice and in control mice. In addition, ex vivo SPECT imaging on excised hearts was performed, and biodistribution of ¹¹¹In-DTPA-cNGR was determined using gamma counting. Binding specificity of ¹¹¹In-DTPA-cNGR to angiogenic active endothelium was determined using the Matrigel model.

Results

Labelling yield of ¹¹¹In-DTPA-cNGR was 95% to 98% and did not require further purification. In vivo, ¹¹¹In-DTPA-cNGR imaging showed a rapid clearance from non-infarcted tissue and a urinary excretion of 82% of the injected dose (I.D.) 2 h after intravenous injection in the MI mice. Specific binding of ¹¹¹In-DTPA-cNGR was confirmed in the Matrigel model and, moreover, binding was demonstrated in the infarcted myocardium and infarct border zone.

Conclusions

Our newly designed and developed angiogenesis imaging probe ¹¹¹In-DTPA-cNGR allows simultaneous imaging of CD13 expression and perfusion in the infarcted myocardium and the infarct border zone by dual-isotope micro-SPECT imaging.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-015-0081-7) contains supplementary material, which is available to authorized users.

The role of TGFβ1 and LRG1 in cardiac remodelling and heart failure

Heart failure is a life-threatening condition that carries a considerable emotional and socio-economic burden. As a result of the global increase in the ageing population, sedentary life-style, increased prevalence of risk factors, and improved survival from cardiovascular events, the incidence of heart failure will continue to rise. Despite the advances in current cardiovascular therapies, many patients are not suitable for or may not benefit from conventional treatments. Thus, more effective therapies are required. Transforming growth factor (TGF) β family of cytokines is involved in heart development and dys-regulated TGFβ signalling is commonly associated with fibrosis, aberrant angiogenesis and accelerated progression into heart failure. Therefore, a potential therapeutic pathway is to modulate TGFβ signalling; however, broad blockage of TGFβ signalling may cause unwanted side effects due to its pivotal role in tissue homeostasis. We found that leucine-rich α-2 glycoprotein 1 (LRG1) promotes blood vessel formation via regulating the context-dependent endothelial TGFβ signalling. This review will focus on the interaction between LRG1 and TGFβ signalling, their involvement in the pathogenesis of heart failure, and the potential for LRG1 to function as a novel therapeutic target.

Serial myocardial perfusion imaging: defining a significant change and targeting management decisions

Myocardial perfusion imaging (MPI) with gated single-photon emission tomography provides important information on the extent and severity of myocardial perfusion abnormalities, including myocardial ischemia. The availability of software for automated quantitative assessment of myocardial perfusion in an objective and more reproducible manner than visual assessment has allowed MPI to be particularly effective in serial evaluation. Serial testing using MPI is widely used in guiding patient care despite the lack of well-defined appropriateness use criteria. This should not be surprising because ischemic heart disease is a life-long malady subject to dynamic changes throughout its natural course and particularly following man-made interventions that may improve or worsen the disease process, such as medical therapy and coronary revascularization. Serial MPI has filled an important clinical gap by providing crucial information for managing patients with changes in clinical presentations or in anticipation of such changes in patients with stable symptoms. In the research arena, serial MPI has been widely applied in randomized controlled trials to study the impact of various medical and interventional therapies on myocardial perfusion, as well as the relative merits of new imaging procedures (hardware and/or software), radiotracers, and stressor agents. Serial testing, however, unlike initial or 1-time testing, has more stringent requirements and is subject to variability because of technical, procedural, interpretational, and biological factors. The intrinsic variability of MPI becomes important in interpreting serial tests in order to define a true change in a given patient and to guide clinical decision making. The purpose of this first comprehensive review on this subject is to illustrate where serial MPI may be useful clinically and in research studies, and to highlight strategies for addressing the various issues that are unique to serial testing in order to derive more valid and robust data from the serial scans.

Dual gene transfer of bFGF and PDGF in a single plasmid for the treatment of myocardial infarction

Basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) have been shown to be involved in a spectrum of cellular processes. In a previous study, we constructed a novel multigenic vector that contained two separate transcription units, each consisting of a strong promoter and an efficient polyadenylation signal. The two promoters were chosen for their ability to work simultaneously. Dual gene transfer of bFGF and PDGF in a single plasmid resulted in a significant increase in collateral blood vessel formation in a rabbit model of hind limb ischemia. The aim of the present study was to investigate the effect of this dual gene transfer strategy in a rat model of acute myocardial infarction (AMI). AMI was induced in rats by ligation of the left anterior descending coronary artery. The animals were randomly divided into four groups and treated with the following therapeutic strategies: Empty plasmid (control), plasmid encoding bFGF (PL-bFGF), plasmid encoding PDGF (PL-PDGF) or plasmid encoding bFGF and PDGF (PL-F-P). Echocardiography and histological examinations were performed 28 days subsequent to gene transfer. Dual gene therapy with bFGF and PDGF resulted in a significant angiogenic effect accompanied by vessel maturation, along with a significant reduction in infarct size and improvement in cardiac function. In a rat model of AMI, single plasmid-mediated dual gene therapy with bFGF and PDGF decreased infarct size and improved cardiac function due to the formation of functionally and morphologically mature vasculature. These results are relevant to the ongoing clinical trials involving the use of single plasmid-mediated angiogenic factors for the treatment of myocardial ischemic disease.

Antagonist molecules in the treatment of angina

INTRODUCTION

Management of chronic angina has evolved dramatically in the last few decades with several options for pharmacotherapy outlined in various evidence-based guidelines.

AREAS COVERED

There is a growing list of drugs that are currently being investigated for treatment of chronic angina. These also include several herbal medications, which are now being scientifically evaluated as potential alternative or even adjunctive therapy for angina. Gene- and cell-based therapies have opened yet another avenue for management of chronic refractory angina in 'no-option' patients who are not candidates for either percutaneous or surgical revascularization and are on optimal medical therapy. An extensive review of literature using PUBMED, Cochrane database, clinical trial databases of the USA and European Union was done and summarized in this review. This review will attempt to discuss the traditional as well as novel therapeutic agents for angina.

EXPERT OPINION

Several pharmacological and non-pharmacological therapeutic options are now available for treatment and management of chronic refractory angina. Renewed interest in traditional therapies and cell- and gene-based modalities with targeted drug delivery systems will open the doors for personalized therapy for patients with chronic refractory angina.

Neovascularization and hematopoietic stem cells

Vasculogenesis and angiogenesis are the major forms of blood vessel formation. Angiogenesis is the process where new vessels grow from pre-existing blood vessels, and is very important in the functional recovery of pathological conditions, such as wound healing and ischemic heart diseases. The development of better animal model and imaging technologies in past decades has greatly enriched our understanding on vasculogenesis and angiogenesis processes. Hypoxia turned out to be an important driving force for angiogenesis in various ischemic conditions. It stimulates expression of many growth factors like vascular endothelial growth factor, platelet-derived growth factor, insulin-like growth factor, and fibroblast growth factor, which play critical role in induction of angiogenesis. Other cellular components like monocytes, T cells, neutrophils, and platelets also play significant role in induction and regulation of angiogenesis. Various stem/progenitor cells also being recruited to the ischemic sites play crucial role in the angiogenesis process. Pre-clinical studies showed that stem/progenitor cells with/without combination of growth factors induce neovascularization in the ischemic tissues in various animal models. In this review, we will discuss about the fundamental factors that regulate the angiogenesis process and the use of stem cells as therapeutic regime for the treatment of ischemic diseases.

Overcoming disease-induced growth factor resistance in therapeutic angiogenesis using recombinant co-receptors delivered by a liposomal system

Current treatment options for ischemia include percutaneous interventions, surgical bypass or pharmacological interventions aimed at slowing the progression of vascular disease. Unfortunately, while each of these treatment modalities provides some benefit for patients in the short-term, many patients have resistant or recurrent disease that is poorly managed by these therapies. A highly appealing strategy for treating ischemic disease is to stimulate the revascularization of the tissue to restore blood flow. While many techniques have been explored in this regard, clinically effective angiogenic therapies remain elusive. Here, we hypothesized that the presence of co-morbid disease states inherently alters the ability of the body to respond to angiogenic therapies. Using a mouse model of diabetes and obesity, we examined alterations in the major components for the signaling pathways for FGF-2, VEGF-A and PDGF under normal and high fat dietary conditions. In skeletal muscle, a high fat diet increased levels of growth factor receptors and co-receptors including syndecan-1, syndecan-4 and PDGFR-α in wild-type mice. These increases did not occur in Ob/Ob mice on a high fat diet and there was a significant decrease in protein levels for neuropilin-1 and heparanase in these mice. With the aim of increasing growth factor effectiveness in the context of disease, we examined whether local treatment with alginate gel-delivered FGF-2 and syndecan-4 proteoliposomes could overcome the growth factor resistance in these mice. This treatment enhanced the formation of new blood vessels in Ob/Ob mice by 6 fold in comparison to FGF-2 delivered alone. Our studies support that disease states cause a profound shift in growth factor signaling pathways and that co-receptor-based therapies have potential to overcome growth factor resistance in the context of disease.

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.

Janus-like role of fibroblast growth factor 2 in arteriosclerotic coronary artery disease: atherogenesis and angiogenesis

Angiogenic stimulation is a promising new strategy for treating patients with arteriosclerotic coronary artery disease. This strategy aims to ameliorate cardiac function by improving myocardial perfusion and lowering the risk of myocardial infarction. However, angiogenesis may contribute to the growth of atherosclerotic lesions. Atherogenesis is also a potential side effect of angiogenic therapy. Early clinical trials were performed using fibroblast growth factor 2 (FGF2) protein, which enhances the formation of new collateral vessels to reduce ischaemic symptoms. Conversely, angiogenic stimulation by FGF2 is a dilemma because it could cause negative angiogenic effects, such as atherosclerosis. Thus far, clinical trials in patients with recombinant FGF2 protein therapy have not yet yielded undisputable beneficial effects. Future trials should determine whether an improvement can be obtained in patients with coronary artery disease using a combination of FGF2 and other growth factors or a combination of the FGF2 gene and stem cell therapy. This review summarises the multiple roles of FGF2 in the progression of atherosclerosis, its effect on pro-angiogenesis and improvement of cardiac function in coronary artery disease, and the potentially unfavourable effect of angiogenesis on the prevention and treatment of atherogenesis.

Reduced peripheral vascular reactivity in refractory angina pectoris: Effect of enhanced external counterpulsation

AIMS

To examine if the skin microvascular bed is altered and can be modified by enhanced external counterpulsation (EECP) in patients with chronic refractory angina.

METHODS

Twenty patients diagnosed with refractory angina were divided into EECP (n = 10) or no EECP (n = 10) groups. The data were compared to matched healthy subjects (n = 20). The cutaneous forearm microvascular blood flow was measured by Laser-Doppler flowmetry. The vascular responsiveness to iontophoretic administration of acetylcholine (ACh), sodium nitroprusside (SNP) and local skin warming were studied. Measurements of Canadian Cardiovascular Society (CCS)-class, blood pressure and plasma samples were registered.

RESULTS

EECP patients showed reduced CCS-class compared to no EECP (P < 0.05). Both EECP and no EECP (P < 0.05) groups had decreased systolic blood pressure (SBP) as compared to SBP at baseline (P < 0.05). There was no difference in resting blood flow between the two refractory groups at baseline as well as after EECP and seven weeks of follow-up. Responses to heating, the responses to ACh and SNP in the cutaneous microcirculation were lower in both groups of refractory angina patients as compared to healthy subjects (P < 0.05). EECP patients corresponded positively to the treatment shown by reduced plasma level of soluble interleukin-2 receptor and CCS-class.

CONCLUSIONS

Refractory angina patients have reduced responsiveness in their cutaneous microcirculation to ACh, SNP and heat compared to healthy subjects. Although EECP reduced the CCS-class, this effect was not associated with improvements in responsiveness of the cutaneous microcirculation.

Therapeutic angiogenesis for myocardial ischemia revisited: basic biological concepts and focus on latest clinical trials

Therapeutic angiogenesis is based on the premise that the development of new blood vessels can be augmented by exogenous administration of the appropriate growth factors. Over the last years, successful preclinical studies and promising results of early clinical trials have created great excitement about the potential of therapeutic angiogenesis for patients with advanced ischemic heart disease. The authors provide an overview of the biology of angiogenesis, the basic characteristics of angiogenic factors, and the different routes of their delivery. They discuss experimental studies in animal models of myocardial ischemia and outline available clinical studies on therapeutic angiogenesis for myocardial ischemia. Related safety issues are also addressed followed by a critical perspective about the future of proangiogenic therapies for ischemic cardiovascular disorders. Despite the established proof of concept and reasonable safety, however, results of the latest trials on therapeutic angiogenesis for myocardial ischemia have provided inconsistent results and the definite means of inducing clinically useful therapeutic angiogenesis remain elusive. More studies are required to gain further insights into the biology of angiogenesis and address pharmacological limitations of current approaches of angiogenic therapy. The authors hope and envisage that in the not-too-distant future, these investigative efforts will lead to important new strategies for treatment of myocardial ischemic syndromes. Means of non-invasive individualized pharmacological therapeutic neovascularization may be the next major advance in the treatment of ischaemic heart disease.

Role of the SDF-1/CXCR4 system in myocardial infarction

Myocardial infarction (MI) is accompanied by an inflammatory response, leading to the recruitment of leukocytes and subsequent myocardial injury and healing. Chemokines are potent chemoattractant cytokines that regulate leukocyte trafficking in inflammatory processes. Recent evidence indicates that chemokines play a role not only in leukocyte trafficking but also in angiogenesis and cardioprotection. In particular, stromal cell-derived factor-1alpha (SDF-1alpha) has generated considerable interest for its role in the pathophysiology of MI. This review will focus on the role of SDF-1 and its receptor CXC chemokine receptor 4 (CXCR4; ie, the SDF-1/CXCR4 system) in the pathophysiology of MI and discuss their potential as therapeutic targets for MI.

Imaging myocardial angiogenesis

Imaging myocardial angiogenesis presents a major technical challenge because the ideal spatial resolution required is substantially higher than that available with standard X-ray angiography and nuclear medicine imaging. Moreover, these clinical imaging methods are currently inadequate (because of insufficient resolution) for clinical trials of angiogenic agents for the treatment of ischemic heart disease. Specialized techniques in MRI, ultrasonography, echocardiography and CT that are under development might provide improved means of imaging myocardial angiogenesis. Molecular imaging technologies are also being developed to improve resolution and to provide a better mechanistic insight into angiogenic therapies for ischemic heart diseases. This Review examines advanced methods for imaging angiogenesis. These technologies might soon permit data to be obtained directly from scientific studies and clinical trials.

Evaluation of the Porcine Ameroid Constrictor Model of Myocardial Ischemia for Therapeutic Angiogenesis Studies

The porcine ameroid model of chronic myocardial ischemia has been widely used for the evaluation of coronary collateralization development. The impact of target vessel occlusion on the presence of myocardial ischemia, and the relationship between morphological, functional, and hemodynamic measurements in the context of therapeutic angiogenesis studies, however, has not been studied thus far. The authors therefore performed a systematic analysis of 94 animals undergoing ameroid constrictor placement around the left circumflex coronary artery (LCX) and, furthermore, a comprehensive evaluation including echocardiography and coronary angiography 26 +/- 1 (mean +/- SEM) days after ameroid placement. Complete LCX occlusion was observed in 34/94 animals (36%) and identified those with myocardial ischemia of the lateral wall, both at rest and under pharmacological stress. By applying a set of angiographic criteria (TIMI <or= 2 flow in LCX and/or collateral flow Rentrop class >or= 1), another 27/94 animals with myocardial ischemia under conditions of pharmacological stress conditions could be identified. Interestingly, echocardiographic parameters of regional and global myocardial function were not correlated with myocardial blood flow or the degree of ischemia. There was no relationship between the extent of coronary collateralization, as assessed by angiography, echocardiographic parameters, or myocardial blood flow. The authors therefore conclude that complete occlusion of the ameroid instrumented coronary artery is not a prerequisite for successfully establishing the pathophysiology of myocardial ischemia. Defined angiographic criteria are important in identifying ischemic animals, thus reducing total animal numbers. Angiographic assessment of the degree of coronary collateralization, however, is not associated with myocardial blood flow or function and should not be used as a primary outcome measure of therapeutic angiogenesis studies in this model.

Biological functions of the low and high molecular weight protein isoforms of fibroblast growth factor-2 in cardiovascular development and disease

Fibroblast growth factor 2 (FGF2) consists of multiple protein isoforms (low molecular weight, LMW, and high molecular weight, HMW) produced by alternative translation from the Fgf2 gene. These protein isoforms are localized to different cellular compartments, indicating unique biological activity. FGF2 isoforms in the heart have distinct roles in many pathological circumstances in the heart including cardiac hypertrophy, ischemia-reperfusion injury, and atherosclerosis. These studies suggest distinct biological activities of FGF2 LMW and HMW isoforms both in vitro and in vivo. Yet, due to the limitations that only the recombinant FGF2 LMW isoform is readily available and that the FGF2 antibody is nonspecific with regards to its isoforms, much remains to be determined regarding the role(s) of the FGF2 LMW and HMW isoforms in cellular behavior and in cardiovascular development and pathophysiology. This review summarizes the activities of LMW and HMW isoforms of FGF2 in cardiovascular development and disease.

Ultrasonic gene and drug delivery to the cardiovascular system

Ultrasound targeted microbubble destruction has evolved as a promising tool for organ specific gene and drug delivery. This technique has initially been developed as a method in myocardial contrast echocardiography, destroying intramyocardial microbubbles to characterize refill kinetics. When loading similar microbubbles with a bioactive substance, ultrasonic destruction of microbubbles may release the transported substance in the targeted organ. Furthermore, high amplitude oscillations of microbubbles lead to increased capillary and cell membrane permeability, thus facilitating tissue and cell penetration of the released substance. While this technique has been successfully used in many organs, its application in the cardiovascular system has dominated so far. Drug delivery using microbubbles has played a minor role in the cardiovascular system. In contrast, gene transfer has been successfully achieved in many studies. Both viral and non-viral vectors were used for loading on microbubbles. This review article will give an overview on studies that have applied ultrasound targeted microbubble destruction to deliver substances in the heart and blood vessels. It will show potential therapeutic targets, especially for gene therapy, describe feasible substances that can be loaded on microbubbles, and critically discuss prospects and limitations of this technique.

Vascular growth in ischemic limbs: a review of mechanisms and possible therapeutic stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Treatment of chronical myocardial ischemia by adenovirus-mediated hepatocyte growth factor gene transfer in minipigs

Growth factor gene transfer-induced therapeutic angiogenesis has become a novel approach for the treatment of myocardial ischemia. In order to provide a basis for the clinical application of an adenovirus with hepatocyte growth factor gene (Ad-HGF) in the treatment of myocardial ischemia, we established a minipig model of chronically ischemic myocardium in which an Ameroid constrictor was placed around the left circumflex branch of the coronary artery (LCX). A total of 18 minipigs were randomly divided into 3 groups: a surgery control group, a model group and an Ad-HGF treatment group implanted with Ameroid constrictor. Ad-HGF or the control agent was injected directly into the ischemic myocardium, and an improvement in heart function and blood supply were evaluated. The results showed that myocardial perfusion remarkably improved in the Ad-HGF group compared with that in both the control and model groups. Four weeks after the treatment, the density of newly formed blood vessels was higher and the number of collateral blood vessels was greater in the Ad-HGF group than in the model group. The area of myocardial ischemia reduced evidently and the left ventricular ejection fraction improved significantly in the Ad-HGF group. These results suggest that HGF gene therapy may become a novel approach in the treatment of chronically ischemic myocardium.

Adenoviral gene transfer of sphingosine kinase 1 protects heart against ischemia/reperfusion-induced injury and attenuates its postischemic failure

Sphingosine kinase 1 (SPK1) has been identified as a central mediator of ischemia preconditioning and plays a protective role in ischemia/reperfusion (I/R)-induced cardiomyocyte death. In the present study, we investigated the protective effect of adenovirus-mediated SPK1 gene (Ad-SPK1) transfer on I/R-induced cardiac injury, and evaluated its therapeutic action on postinfarction heart failure. Cardiac SPK1 activity was increased about 5-fold by injection of Ad-SPK1, compared with injection of adenovirus carrying the green fluorescent protein gene (Ad-GFP). A more potent performance and a lower incidence of arrhythmia were observed in Ad-SPK1-injected hearts during the reperfusion period, compared with Ad-GFP-injected hearts. An enzymatic activity assay showed that creatine kinase release was also less in Ad-SPK1-injected hearts. To investigate the therapeutic action of the SPK1 gene on postischemic heart failure, the left anterior descending branch of the coronary artery in Wistar rats was ligated after direct intramyocardial injection of Ad-SPK1 or Ad-GFP as a control. Ad-SPK1 injection significantly preserved cardiac systolic and diastolic function, as evidenced by left ventricular (LV) systolic pressure, LV end-diastolic pressure, and peak velocity of contraction (dP/dt). The LV morphometric parameters of Ad-SPK1-treated animals were also preserved. In addition, SPK1 gene delivery significantly enhanced angiogenesis and reduced fibrosis. These results demonstrate that adenovirus-mediated SPK1 gene transfer could efficiently prevent I/R-induced myocardial injury and attenuate postischemic heart failure. Thus, SPK1 gene delivery would be a novel strategy for the treatment of coronary heart disease.

Spatiotemporal control over growth factor signaling for therapeutic neovascularization

Many of the qualitative roles of growth factors involved in neovascularization have been delineated, but it is unclear yet from an engineering perspective how to use these factors as therapies. We propose that an approach that integrates quantitative spatiotemporal measurements of growth factor signaling using 3-D in vitro and in vivo models, mathematic modeling of factor tissue distribution, and new delivery technologies may provide an opportunity to engineer neovascularization on demand.

Therapeutic myocardial angiogenesis

Armed with an improved understanding of the mediators of angiogenesis, physicians and scientists have made significant efforts at harnessing this naturally occurring process in order to treat patients with a variety of peripheral vascular and coronary ischemic syndromes. There is a growing population of patients with end-stage coronary artery disease (CAD) who are no longer candidates for mechanical revascularization, yet suffer from chronic myocardial ischemia who may benefit from regeneration of the depleted microvasculature.

Gated SPECT imaging to detect changes in myocardial blood flow during progressive coronary occlusion

BACKGROUND

The ability to track dynamic changes in myocardial blood flow (MBF) and wall motion with serial gated perfusion imaging may be a limiting factor in assessing new therapies. The purpose of this study was to determine whether gated Tc-99 m sestamibi (MIBI) SPECT imaging can track small changes in MBF in a model of progressive ischemia.

METHODS

Eight pigs (20 kg) underwent lateral thoracotomy for placement of an ameroid constrictor on the left circumflex coronary artery (LCX) and indwelling femoral and left atrial catheters for serial microsphere determinations of absolute MBF. Animals underwent concurrent left atrial microsphere and Tc-99 m sestamibi (0.3 mCi/Kg IV) injections at weekly intervals over 6 weeks per animal. Gated SPECT imaging was acquired for each injection using high resolution collimation and standard processing. The animals were sacrificed on day 42. Mean signal intensity (SI) from regions of interest (ROI) corresponding to control and ischemic MBF by microspheres was measured for three SPECT short-axis images. Mean contrast ratio (MCR) was calculated from the ratio of ischemic to control SI per slice. Regional wall motion (RWM) from gated images was scored 1-5 using a 16 segment model and a score index (RWMI) was calculated.

RESULTS

MBF decreased progressively (27% below resting values [P < 0.0001]) but with a clear and significant partial recovery by day 42 (13% improvement from peak ischemia, [P < 0.01]). SPECT perfusion and gated RWM closely paralleled the dynamic pattern of MBF caused by the ameroid constrictor. SPECT MCR decreased 21% from baseline scans in the LCX territory (P < 0.0001) and improved 11% from peak ischemia (P < 0.01) while the gated RWMI (1.0 at baseline) peaked at 1.36 and improved to 1.13 by day 42.

CONCLUSION

Gated SPECT-a technique readily available-tracks dynamic changes in MBF closely with both perfusion and RWM. For trials of new therapies for the alleviation of chronic ischemia, these findings have direct implications for measuring efficacy.

Combinatorial protein therapy of angiogenic and arteriogenic factors remarkably improves collaterogenesis and cardiac function in pigs

Establishment of functional and stable collaterals in the ischemic myocardium is crucial to restoring cardiac function after myocardial infarction. Here, we show that only dual delivery of a combination of angiogenic and arteriogenic factors to the ischemic myocardium could significantly reestablish stable collateral networks and improve myocardial perfusion and function. A combination of FGF-2 with PDGF-BB, two factors primarily targeting endothelial cells and vascular smooth muscle cells, remarkably promotes myocardial collateral growth and stabilizes the newly formed collateral networks, which significantly restore myocardial perfusion and function. Using various members of the PDGF family together with FGF-2 in an angiogenesis assay, we demonstrate that PDGFR-alpha is mainly involved in angiogenic synergism, whereas PDGFR-beta mediates vessel stability signals. Our findings provide conceptual guidelines for the clinical development of proangiogenic/arteriogenic factors for the treatment of ischemic heart disease.

A randomized, double-blind, placebo-controlled, multicenter, pilot study of the safety and feasibility of catheter-based intramyocardial injection of AdVEGF121 in patients with refractory advanced coronary artery disease

BACKGROUND

The experience with direct myocardial injection of adenovirus encoding angiogenic growth factor is limited to invasive surgical approach. Accordingly, we sought to evaluate, for the first time, in a randomized, double-blind, placebo-controlled, phase I pilot study the safety and feasibility of percutaneous catheter-based intramyocardial delivery of a replication-deficient adenovector encoding the 121-amino-acid isoform of vascular endothelial growth factor (AdVEGF121).

METHODS

Ten "no-option" patients with severe coronary artery disease were randomized (2:1) to receive AdVEGF121 (4 x 10(10) pu) or placebo as fifteen 100 microL, evenly distributed, endomyocardial injections using a nonflouroscopic, 3-dimensional mapping and injection (NOGA) catheter-based system.

RESULTS

Injection procedure was successfully completed in all cases and was associated with no major adverse events. AdVEGF121 was considered potentially associated with a single serious adverse event of transient moderate fever. Elevated postprocedure CK and CK-MB fraction levels were recorded in two placebo-treated and three AdVEGF121-treated patients; all CK measured values were <1.5 times upper limit of normal. All adenoviral cultures (urine and throat swab) were negative 24-hr after dosing, and no significant changes in serial plasma VEGF levels were noted over time. At 12 months follow-up, no cancers, proliferative retinal changes, or significant abnormalities in hepatic, renal or hematological indices were observed.

CONCLUSIONS

Percutaneous, catheter-based AdVEGF121 intramyocardial injection is a practical, feasible, and potentially safe approach for intramyocardial gene transfer. A larger randomized, phase II efficacy study is warranted.

Gene and cell therapy for chronic ischaemic heart disease

Viable treatment options are becoming available for the 'no-option' patient with chronic ischaemic heart disease. Instead of revascularising the highly diseased epicardial coronary arteries, scientists and clinicians have been looking at augmenting mother nature's way of providing biological bypass in an attempt to provide symptomatic relief in these patients. The novel use of gene and cell therapies for myocardial neovascularisation has exploded into a flurry of early clinical trials. This translational research has been motivated by an improved understanding of the biological mechanisms involved in tissue repair after ischaemic injury. While safety concerns will be top in priority in these trials, different types or combination of therapies, dose and route of delivery are being tested before further optimisation and establishment. With cautious optimism, a new era in the treatment of ischaemic heart disease is being entered. This article reviews the present state in gene and cell therapies for ischaemic heart disease, the modalities of their delivery, novel imaging techniques and future perspectives.

Molecular cardiovascular imaging using scintigraphic methods

Molecular cardiovascular imaging plays an increasingly important role both in basic research and in clinical diagnosis. Scintigraphic methods have long been used to study pathophysiological changes on a cellular and molecular level, and they are likely to remain important molecular imaging modalities in the foreseeable future. This article provides an overview over current developments in cardiovascular molecular imaging using scintigraphic methods. The focus lies on imaging of cardiac innervation, plaque instability, hypoxia and angiogenesis, gene expression and stem and progenitor cell migration and proliferation.

The effect of intracoronary fibroblast growth factor-2 on restenosis after primary angioplasty or stent placement in a pig model of atherosclerosis

BACKGROUND

Therapeutic angiogenesis, if combined with primary percutaneous transluminal coronary angioplasty or stent placement, could improve the outcome of patients suffering from multifocal coronary disease.

HYPOTHESIS

Because of the concern that angiogenic growth factors might promote restenosis, we studied the effect of a single intracoronary administration of recombinant fibroblast growth factor (rFGF)-2 on restenosis after balloon angioplasty and stent placement in a pig model of coronary atherosclerosis.

METHODS

In 24 Yucatan minipigs, coronary lesions were induced by arterial injury and 3 months of atherogenic diet. After 3 months, repeat catheterization was performed with balloon dilation or stent placement at the injured sites, with a follow-up of 6 weeks. Results were monitored using quantitative angiography, intravascular ultrasound (IVUS), and histomorphometry.

RESULTS

Intracoronary rFGF-2 2 microg/kg did not affect neointima formation or remodeling in this model. A small but significant aggravation of late lumen loss was observed in the reference segments of the rFGF-2-treated group. Angiographic and echographic late lumen loss, intimal hyperplasia, and arterial remodeling, as well as histologic neointima were all similar in the rFGF-2- and the vehicle-treated group. Confirming earlier studies from our group and those of others, stented arteries compared with balloon-dilated arteries had increased angiographic late lumen loss, a trend toward increased intimal hyperplasia and decreased remodeling.

CONCLUSION

We conclude that rFGF-2 does not aggravate restenosis after balloon dilation or stenting in this pig model of coronary atherosclerosis. Future combinations of angioplasty and therapeutic angiogenesis in a single session should be pursued as a feasible and safe strategy.

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.

Skeletal muscle cells expressing VEGF induce capillary formation and reduce cardiac injury in rats

BACKGROUND

We tested a preemptive combined cell/gene therapy strategy of skeletal myoblasts transfected with Ad(5)RSVVEGF-165 in an ischemia/reperfusion rat model to increase collateral blood flow to nonischemic heart tissue.

METHODS

Lewis rats were injected with placebo (Control), 10(6) skeletal myoblasts (SkM), or 10(6) skeletal myoblasts transfected with Ad(5)RSVVEGF-165 (SkM(+)) into the left ventricle 1week before ischemia. Left ventricle end-diastolic pressure, scar area, and capillary density were assessed 4weeks later.

RESULTS

Local expression of human vascular endothelial growth factor was accompanied by an increase in capillary density in the SkM(+) group compared with that in the SkM and Control groups (700+/-40 vs. 289+/-18 and 318+/-59capillaries/mm(2), respectively; p<0.05). After 3weeks, the myocardial scar area was reduced in SkM(+) vs. Control (5.3+/-0.4% and 14.8+/-1.6%, p<0.05), while injected cells alone (SkM) did not cause improvement compared with Control (11.8+/-2.1% vs. 14.8+/-1.6%, p>0.05). The decrease in the scar area in SkM(+) was accompanied by an increase in the capillary density compared with that in SkM and Control 30days after cell injection (1005+/-108 vs. 524+/-16 and 528+/-26capillaries/mm(2), respectively; p<0.05). The scar areas were discrete (5.3-14.8%) and left ventricle end-diastolic pressure in all groups were comparable (p>0.05).

CONCLUSIONS

The combined cell/gene therapy strategy of genetically modified myoblast cells expressing angiogenic factors injected into the myocardium induced capillary formation and prevented the extension and development of cardiac damage associated with ischemia/reperfusion in rats.

Cardiovascular imaging to quantify the evolution of cardiac diseases in clinical development

Cardiovascular diseases are the leading causes of mortality in western countries, leading to the development of a large set of preventive and curative treatments. Medical imaging is the gold standard to evaluate both cardiac perfusion and cardiac function and can be used even before the advent of hard events to accurately assess treatment effects. This study reviews the different image modalities that can be used to evaluate the evolution of cardiac diseases, especially coronary artery diseases. It also reviews different techniques heavily relying upon image co-registration techniques and population model designs that enable accurate quantitative evaluation of cardiac perfusion and cardiac function through time. It will draw the pros and cons of the different imaging modalities in actual clinical trials: Gated or tagged MRI, MRI for perfusion, PET, SPECT, Gated SPECT, MUGA, Ultrasound. This study also details the latest advances in quantification of cardiac SPECT, which has wide use in clinical trials today.

Skin-Derived Micro-Organs Induce Angiogenesis in Rabbits

We have recently reported an alternative cell therapy approach to induce angiogenesis. The approach is based on small organ fragments--micro-organs (MOs)--whose geometry allows preservation of the natural epithelial/mesenchymal interactions and ensures appropriate diffusion of nutrients and gases to all cells. We have shown that lung-derived MOs, when implanted into hosts, transcribe a wide spectrum array of angiogenic factors and can induce an angiogenic response that can rescue experimentally induced ischemic regions in mice. From a clinical perspective, skin-derived MOs are particularly appealing as they could readily be obtained from a skin biopsy taken from the same target patient. In the present work we have investigated the angiogenesis-inducing capacity of rabbit and human skin-derived micro-organs in vitro and in vivo. Rabbit skin MOs were implanted into homologous adult rabbits and human skin MOs were encapsulated and implanted into xenogenic mice. Skin-derived MOs, as lung-derived MOs, were found to secrete a whole array of angiogenic factors and to induce a powerful angiogenic response when implanted back into animals. We believe the approach presented suggests a novel, efficacious and simple approach for therapeutic angiogenesis.