Effects of acidic fibroblast growth factor on normal and ischemic myocardium

Healing the Broken Hearts: A Glimpse on Next Generation Therapeutics

Cardiovascular diseases are the leading cause of death worldwide, accounting for 32% of deaths globally and thus representing almost 18 million people according to WHO. Myocardial infarction, the most prevalent adult cardiovascular pathology, affects over half a million people in the USA according to the last records of the AHA. However, not only adult cardiovascular diseases are the most frequent diseases in adulthood, but congenital heart diseases also affect 0.8–1.2% of all births, accounting for mild developmental defects such as atrial septal defects to life-threatening pathologies such as tetralogy of Fallot or permanent common trunk that, if not surgically corrected in early postnatal days, they are incompatible with life. Therefore, both congenital and adult cardiovascular diseases represent an enormous social and economic burden that invariably demands continuous efforts to understand the causes of such cardiovascular defects and develop innovative strategies to correct and/or palliate them. In the next paragraphs, we aim to briefly account for our current understanding of the cellular bases of both congenital and adult cardiovascular diseases, providing a perspective of the plausible lines of action that might eventually result in increasing our understanding of cardiovascular diseases. This analysis will come out with the building blocks for designing novel and innovative therapeutic approaches to healing the broken hearts.

Fibroblast Growth Factor Type 1 Ameliorates High-Glucose-Induced Oxidative Stress and Neuroinflammation in Retinal Pigment Epithelial Cells and a Streptozotocin-Induced Diabetic Rat Model

Diabetic retinopathy (DR) is a common complication of diabetes that causes severe visual impairment globally. The pathogenesis of DR is related to oxidative stress and chronic inflammation. The fibroblast growth factor type 1 (FGF-1) mitogen plays crucial roles in cell function, development, and metabolism. FGF-1 is involved in blood sugar regulation and exerts beneficial antioxidative and anti-inflammatory effects on various organ systems. This study investigated the antioxidative and anti-inflammatory neuroprotective effects of FGF-1 on high-glucose-induced retinal damage. The results revealed that FGF-1 treatment significantly reversed the harmful effects of oxidative stress and inflammatory mediators in retinal tissue in a streptozotocin-induced diabetic rat model. These protective effects were also observed in the in vitro model of retinal ARPE-19 cells exposed to a high-glucose condition. We demonstrated that FGF-1 attenuated p38 mitogen-activated protein kinase and nuclear factor-κB pathway activation under the high-glucose condition. Our results indicated that FGF-1 could effectively prevent retinal injury in diabetes. The findings of this study could be used to develop novel treatments for DR that aim to reduce the cascade of oxidative stress and inflammatory signals in neuroretinal tissue.

Utilizing the ABC Transporter for Growth Factor Production by fleQ Deletion Mutant of Pseudomonas fluorescens

Pseudomonas fluorescens, a gram-negative bacterium, has been proven to be a capable protein manufacturing factory (PMF). Utilizing its ATP-binding cassette (ABC) transporter, a type I secretion system, P. fluorescens has successfully produced recombinant proteins. However, besides the target proteins, P. fluorescens also secretes unnecessary background proteins that complicate protein purification and other downstream processes. One of the background proteins produced in large amounts is FliC, a flagellin protein. In this study, the master regulator of flagella gene expression, fleQ, was deleted from P. fluorescens Δtp, a lipase and protease double-deletion mutant, via targeted gene knockout. FleQ directs flagella synthesis, so the new strain, P. fluorescens ΔfleQ, does not produce flagella-related proteins. This not only simplifies purification but also makes P. fluorescens ΔfleQ an eco-friendly expression host because it will not survive outside a controlled environment. Six recombinant growth factors, namely, insulin-like growth factors I and II, beta-nerve growth factor, fibroblast growth factor 1, transforming growth factor beta, and tumor necrosis factor beta, prepared using our supercharging method, were successfully secreted by P. fluorescens ΔfleQ. Our findings demonstrate the potential of P. fluorescens ΔfleQ, combined with our supercharging process, as a PMF.

Regulatory role of endogenous and exogenous fibroblast growth factor 1 in the cardiovascular system and related diseases

Fibroblast growth factor 1 (FGF1) has a critical regulatory role in the development of the cardiovascular system (CVS) and is strongly associated with the progression or treatment of cardiovascular diseases (CVDs). However, the regulatory mechanisms of FGF1 in CVS and CVDs have not yet been fully elucidated. Therefore, this review article summarized the existing literature reports on the role of FGF1 in CVS under physiological and pathological conditions. First, the expression and physiological functions of endogenous FGF1 is fully demonstrated. Then, we analyzed the role of exogenous FGF1 in normal CVS and related pathological processes. Specifically, the potential signaling pathways might be mediated by FGF1 in CVDs treatment is discussed in detail. In addition, the barriers and feasible solutions for the application of FGF1 are further analyzed. Finally, we highlight therapeutic considerations of FGF1 for CVDs in the future. Thus, this article may be as a reference to provide some ideas for the follow-up research.

Myocardial protection by nanomaterials formulated with CHIR99021 and FGF1

The mortality of patients suffering from acute myocardial infarction is linearly related to the infarct size. As regeneration of cardiomyocytes from cardiac progenitor cells is minimal in the mammalian adult heart, we have explored a new therapeutic approach, which leverages the capacity of nanomaterials to release chemicals over time to promote myocardial protection and infarct size reduction. Initial screening identified 2 chemicals, FGF1 and CHIR99021 (a Wnt1 agonist/GSK-3β antagonist), which synergistically enhance cardiomyocyte cell cycle in vitro. Poly-lactic-co-glycolic acid nanoparticles (NPs) formulated with CHIR99021 and FGF1 (CHIR + FGF1-NPs) provided an effective slow-release system for up to 4 weeks. Intramyocardial injection of CHIR + FGF1-NPs enabled myocardial protection via reducing infarct size by 20%-30% in mouse or pig models of postinfarction left ventricular (LV) remodeling. This LV structural improvement was accompanied by preservation of cardiac contractile function. Further investigation revealed that CHIR + FGF1-NPs resulted in a reduction of cardiomyocyte apoptosis and increase of angiogenesis. Thus, using a combination of chemicals and an NP-based prolonged-release system that works synergistically, this study demonstrates a potentially novel therapy for LV infarct size reduction in hearts with acute myocardial infarction.

The Active Compounds of Yixin Ningshen Tablet and Their Potential Action Mechanism in Treating Coronary Heart Disease- A Network Pharmacology and Proteomics Approach

Yixin Ningshen tablet is a CFDA-approved TCM formula for treating coronary heart disease (CHD) clinically. However, its active compounds and mechanism of action in treating CHD are unknown. In this study, a novel strategy with the combination of network pharmacology and proteomics was proposed to identify the active components of Yixin Ningshen tablet and the mechanism by which they treat CHD. With the application of network pharmacology, 62 active compounds in Yixin Ningshen tablet were screened out by text mining, and their 313 potential target proteins were identified by a tool in SwissTargetPrediction. These data were integrated with known CHD-related proteomics results to predict the most possible targets, which reduced the 313 potential target proteins to 218. The STRING database was retrieved to find the enriched pathways and related diseases of these target proteins, which indicated that the Calcium, MAPK, PI3K-Akt, cAMP, Rap1, AGE-RAGE, Relaxin, HIF-1, Prolactin, Sphingolipid, Estrogen, IL-17, Jak-STAT signaling pathway, necroptosis, arachidonic acid metabolism, insulin resistance, endocrine resistance, and steroid hormone biosynthesis might be the main pathways regulated by Yixin Ningshen tablet for the treatment of CHD. Through further enrichment analysis and literature study, EGFR, ERBB2, VGFR2, FGF1, ESR1, LOX15, PGH2, HMDH, ADRB1, and ADRB2 were selected and then validated to be the target proteins of Yixin Ningshen tablet by molecular docking, which indicated that Yixin Ningshen tablet might treat CHD mainly through promoting heart regeneration, new vessels' formation, and the blood supply of the myocardial region and reducing cardiac output, oxygen demand, and inflammation as well as arteriosclerosis (promoting vasodilation and intraplaque neoangiogenesis, lowering blood lipid). This study is expected to benefit the clinical application of Yixin Ningshen tablet for the treatment of CHD.

Fibroblast Growth Factor-1 Improves Insulin Resistance via Repression of JNK-Mediated Inflammation

Insulin resistance is associated with a greatly increased risk of type 2 diabetes. Administration of fibroblast growth factor-1 (FGF-1) resulted in a marked improvement in insulin sensitivity. However, the underlying molecular mechanism whereby FGF-1 represses insulin resistance remains largely unknown. Here, we sought to delineate the role of FGF-1 in insulin resistance with respect to its anti-inflammatory capability. In this study, we found that FGF-1 had positive effects on glucose intolerance, hepatic lipid accumulation, and insulin resistance, while it markedly repressed cytokine secretion (TNF-α and IL-6) in serum and reduced liver inflammation in diet-induced obesity (DIO) mice. Further, FGF-1 treatment significantly represses TNF-α-induced insulin resistance in vitro and in vivo. These results indicate that FGF-1 likely ameliorates insulin resistance via a mechanism that is independent of its glucose-lowering activity. Subsequent experiments demonstrated that FGF-1 ameliorated insulin resistance, and inflammation was accompanied by decreased c-Jun N-terminal kinase (JNK) signaling. In addition, it is likely that FGF-1 impedes JNK phosphorylation via blocking the transforming growth factor-β activated kinase 1 (TAK1) and TAK1 binding protein 1 (TAB1) interaction. These findings reveal that FGF-1 regulates insulin sensitivity and may represent an attractive therapeutic target for preventing the development of insulin resistance.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Angiogenic growth factors in myocardial infarction: a critical appraisal

In the recent past, substantial advances have been made in the treatment of myocardial infarction (MI). Despite the impact of these positive developments, MI remains to be a leading cause of morbidity as well as mortality. An interesting hypothesis is that the development of new blood vessels (angiogenesis) or the remodeling of preexisting collaterals may form natural bypasses that could compensate for the occlusion of an epicardial coronary artery. A number of angiogenic factors are proven to be elicited during MI. Exogenous supplementation of these growth factors either in the form of recombinant protein or gene would enhance the collateral vessel formation and thereby improve the outcome after MI. The aim of this review is to describe the nature and potentials of different angiogenic factors, their expression, their efficacy in animal studies, and clinical trials pertaining to MI.

Fibroblast growth factor 1 ameliorates diabetic nephropathy by an anti-inflammatory mechanism

Inflammation plays a central role in the etiology of diabetic nephropathy, a global health issue. We observed a significant reduction in the renal expression of fibroblast growth factor 1, a known mitogen and insulin sensitizer, in patients with diabetic nephropathy and in mouse models implying that fibroblast growth factor 1 possesses beneficial anti-inflammatory and renoprotective activities in vivo. To test this possibility, we investigated the effects of chronic intraperitoneal administration of fibroblast growth factor 1 into both the streptozotocin-induced type 1 diabetes and db/db type 2 diabetes models. Indeed, recombinant fibroblast growth factor 1 significantly suppressed renal inflammation (i.e., cytokines, macrophage infiltration), glomerular and tubular damage, and renal dysfunction in both type 1 and type 2 diabetes mice. Fibroblast growth factor 1 was able to correct the elevated blood glucose levels in type 2 but not in type 1 diabetic mice, suggesting that the anti-inflammatory effect of fibroblast growth factor 1 was independent of its glucose-lowering activity. The mechanistic study demonstrated that fibroblast growth factor 1-mediated inhibition of the renal inflammation in vivo was accompanied by attenuation of the nuclear factor κB and c-Jun N-terminal kinase signaling pathways, further validated in vitro using cultured glomerular mesangial cells and podocytes. Thus, fibroblast growth factor 1 holds great promise for developing new treatments for diabetic nephropathy through countering inflammatory signaling cascades in injured renal tissue.

Delivery of drugs, growth factors, genes and stem cells via intrapericardial, epicardial and intramyocardial routes for sustained local targeted therapy of myocardial disease

INTRODUCTION

Local myocardial delivery (LMD) of therapeutic agents is a promising strategy that aims to treat various myocardial pathologies. It is designed to deliver agents directly to the myocardium and minimize their extracardiac concentrations and side effects. LMD aims to enhance outcomes of existing therapies by broadening their therapeutic window and to utilize new agents that could not be otherwise be implemented systemically. Areas covered: This article provides a historical overview of six decades LMD evolution in terms of the approaches, including intrapericardial, epicardial, and intramyocardial delivery, and the wide array of classes of agents used to treat myocardial pathologies. We examines delivery of pharmaceutical compounds, targeted gene transfection and cell implantation techniques to produce therapeutic effects locally. We outline therapeutic indications, successes and failures as well as technical approaches for LMD. Expert opinion: While LMD is more complicated than conventional oral or intravenous administration, given recent advances in interventional cardiology, it is safe and may provide better therapeutic outcomes. LMD is complex as many factors impact pharmacokinetics and biologic result. The choice between routes of LMD is largely driven not only by the myocardial pathology but also by the nature and physicochemical properties of the therapeutic agents.

Temporal cardiac remodeling post-myocardial infarction: dynamics and prognostic implications in personalized medicine

Despite dramatic improvements in short-term mortality rates following myocardial infarction (MI), long-term survival for MI patients who progress to heart failure remains poor. MI occurs when the left ventricle (LV) is deprived of oxygen for a sufficient period of time to induce irreversible necrosis of the myocardium. The LV response to MI involves significant tissue, cellular, and molecular level modifications, as well as substantial hemodynamic changes that feedback negatively to amplify the response. Inflammation to remove necrotic myocytes and fibroblast activation to form a scar are key wound healing responses that are highly variable across individuals. Few biomarkers of early remodeling stages are currently clinically adopted. The discovery of underlying pathophysiological mechanisms and associated novel biomarkers has the potential of improving prognostic capability and therapeutic monitoring. Combining these biomarkers with other prominent ones could constitute a powerful diagnostic and prognostic tool that directly reflects the pathophysiological remodeling of the LV. Understanding temporal remodeling at the tissue, cellular, and molecular level and its link to a well-defined set of biomarkers at early stages post-MI is a prerequisite for improving personalized care and devising more successful therapeutic interventions. Here we summarize the integral mechanisms that occur during early cardiac remodeling in the post-MI setting and highlight the most prominent biomarkers for assessing disease progression.

Muscle weakness during aging: a deficiency state involving declining angiogenesis

This essay begins by proposing that muscle weakness of old age from sarcopenia is due in large part to reduced capillary density in the muscles, as documented in 9 reports of aged persons and animals. Capillary density (CD) is determined by local levels of various angiogenic factors, which also decline in muscles with aging, as reported in 7 studies of old persons and animals. There are also numerous reports of reduced CD in the aged brain and other studies showing reduced CD in the kidney and heart of aged animals. Thus a waning angiogenesis throughout the body may be a natural occurrence in later years and may account significantly for the lesser ailments (physical and cognitive) of elderly people. Old age is regarded here as a deficiency state which may be corrected by therapeutic angiogenesis, much as a hormonal deficiency can be relieved by the appropriate hormone therapy. Such therapy could employ recombinant angiogenic factors which are now commercially available.

Protein engineering for cardiovascular therapeutics: untapped potential for cardiac repair

A number of new and innovative approaches for repairing damaged myocardium are currently undergoing investigation, with several encouraging results. In addition to the progression of stem cell-based approaches and gene therapy/silencing methods, evidence continues to emerge that protein therapeutics may be used to directly promote cardiac repair and even regeneration. However, proteins are often limited in their therapeutic potential by short local half-lives and insufficient bioavailability and bioactivity, and many academic laboratories studying cardiovascular diseases are more comfortable with molecular and cellular biology than with protein biochemistry. Protein engineering has been used broadly to overcome weaknesses traditionally associated with protein therapeutics and has the potential to specifically enhance the efficacy of molecules for cardiac repair. However, protein engineering as a strategy has not yet been used in the development of cardiovascular therapeutics to the degree that it has been used in other fields. In this review, we discuss the role of engineered proteins in cardiovascular therapies to date. Further, we address the promise of applying emerging protein engineering technologies to cardiovascular medicine and the barriers that must be overcome to enable the ultimate success of this approach.

Angiogenesis in the infarcted myocardium

SIGNIFICANCE

Proangiogenic therapy appeared a promising strategy for the treatment of patients with acute myocardial infarction (MI), as de novo formation of microvessels, has the potential to salvage ischemic myocardium at early stages after MI, and is also essential to prevent the transition to heart failure through the control of cardiomyocyte hypertrophy and contractility.

RECENT ADVANCES

Exciting preclinical studies evaluating proangiogenic therapies for MI have prompted the initiation of numerous clinical trials based on protein or gene transfer delivery of growth factors and administration of stem/progenitor cells, mainly from bone marrow origin. Nonetheless, these clinical trials showed mixed results in patients with acute MI.

CRITICAL ISSUES

Even though methodological caveats, such as way of delivery for angiogenic growth factors (e.g., protein vs. gene transfer) and stem/progenitor cells or isolation/culture procedure for regenerative cells might partially explain the failure of such trials, it appears that delivery of a single growth factor or cell type does not support angiogenesis sufficiently to promote cardiac repair.

FUTURE DIRECTIONS

Optimization of proangiogenic therapies might include stimulation of both angiogenesis and vessel maturation and/or the use of additional sources of stem/progenitor cells, such as cardiac progenitor cells. Experimental unraveling of the mechanisms of angiogenesis, vessel maturation, and endothelial cell/cardiomyocyte cross talk in the ischemic heart, analysis of emerging pathways, as well as a better understanding of how cardiovascular risk factors impact endogenous and therapeutically stimulated angiogenesis, would undoubtedly pave the way for the development of novel and hopefully efficient angiogenesis targeting therapeutics for the treatment of acute MI.

Acidic and basic fibroblast growth factors involved in cardiac angiogenesis following infarction

Acidic and basic fibroblast growth factors (FGF-1/FGF-2) promote angiogenesis in cancer. Angiogenesis is integral to cardiac repair following myocardial infarction (MI). The potential regulation of FGF-1/FGF-2 in cardiac angiogenesis postMI remains unexplored. Herein, we examined the temporal and spatial expression of FGF-1/FGF-2 and FGF receptors (FGFR) in the infarcted rat heart at days 1, 3, 7, and 14 postMI. FGF-1/-2 gene and protein expression, cells expressing FGF-1/-2 and FGFR expression were examined by quantitative in situ hybridization, RT-PCR; western blot, immunohistochemistry and quantitative in vitro autoradiography. Compared to the normal heart, we found that in the border zone and infarcted myocardium 1) FGF-1 gene expression was increased in the first week postMI and returned to control levels at week 2; FGF-1 protein levels were, however, largely reduced at day 1, then elevated at day 3 peaked at day 7 and declined at day 14; and cells expressing FGF-1 were primarily inflammatory cells; 2) FGF-2 gene expression was significantly elevated from day 1 to day 14; the increase in FGF-2 protein level was most evident at day 7 and cells expressing FGF-2 were primarily endothelial cells; 3) FGFR expression started to increase at day 3 and remained elevated thereafter; and 4) FGF-1/FGF-2 and FGFR expression remained unchanged in the noninfarcted myocardium. Thus, FGF-1/FGF-2 and FGFR expression are enhanced in the infarcted myocardium in the early stage after MI, which is spatially and temporally coincident with angiogenesis, suggesting that FGF-1/FGF-2 are involved in regulating cardiac angiogenesis and repair.

Protein therapeutics for cardiac regeneration after myocardial infarction

Although most medicines have historically been small molecules, many newly approved drugs are derived from proteins. Protein therapies have been developed for treatment of diseases in almost every organ system, including the heart. Great excitement has now arisen in the field of regenerative medicine, particularly for cardiac regeneration after myocardial infarction. Every year, millions of people suffer from acute myocardial infarction, but the adult mammalian myocardium has limited regeneration potential. Regeneration of the heart after myocardium infarction is therefore an exciting target for protein therapeutics. In this review, we discuss different classes of proteins that have therapeutic potential to regenerate the heart after myocardial infarction. Protein candidates have been described that induce angiogenesis, including fibroblast growth factors and vascular endothelial growth factors, although thus far clinical development has been disappointing. Chemotactic factors that attract stem cells, e.g., hepatocyte growth factor and stromal cell-derived factor-1, may also be useful. Finally, neuregulins and periostin are proteins that induce cell-cycle reentry of cardiomyocytes, and growth factors like IGF-1 can induce growth and differentiation of stem cells. As our knowledge of the biology of regenerative processes and the role of specific proteins in these processes increases, the use of proteins as regenerative drugs could develop as a cardiac therapy.

Coronary vessel development and insight towards neovascular therapy

Formation of the coronary arteries consists of a precisely orchestrated series of morphogenetic and molecular events which can be divided into three distinct processes: vasculogenesis, angiogenesis and arteriogenesis (Risau 1997; Carmeliet 2000). Even subtle perturbations in this process may lead to congenital coronary artery anomalies, as occur in 0.2-1.2% of the general population (von Kodolitsch et al. 2004). Contrary to the previously held dogma, the process of vasculogenesis is not limited to prenatal development. Both vasculogenesis and angiogenesis are now known to actively occur within the adult heart. When the need for regeneration arises, for example in the setting of coronary artery disease, a reactivation of embryonic processes ensues, redeploying many of the same molecular regulators. Thus, an understanding of the mechanisms of embryonic coronary vasculogenesis and angiogenesis may prove invaluable in developing novel strategies for cardiovascular regeneration and therapeutic coronary angiogenesis.

Therapeutic angiogenesis: a new treatment approach for ischemic heart disease--Part II

Angiogenesis is the biologic process of forming new blood vessels and is being investigated as an innovative therapeutic approach to help manage ischemic heart disease and peripheral vascular disease. Research studies have identified various angiogenic growth factors and progenitor cells that can enhance new blood vessel formation. This is Part II of an article that began publication in the July/August issue of Cardiology in Review. Preclinical investigations in animal models have explored the potential use of growth factors with and without progenitor cells to treat myocardial ischemia. The results of clinical trials with growth factor infusions and gene therapy techniques to enhance growth factor production have shown some promise, but therapeutic angiogenesis remains at an early stage of development.

Growth factors and cell therapy in myocardial regeneration

Despite significant advances in myocardial revascularization and reperfusion, coronary artery disease and subsequently myocardial infarction, are the leading cause of morbidity and mortality in the US. Thus one of the main goals in the treatment of myocardial ischemia is the development of effective therapy for angiogenesis. The first evidence is the demonstration of alleviation of myocardial ischemia and increased number of collateral blood vessels in the early 1990s following intra-coronary administration of basic fibroblast growth factor protein in dog. Multiple animal studies, has confirmed the concept of stimulation of collateral development by pharmacological and molecular means. This includes direct delivery of growth factors into the ischemic target tissues, or of genes that encode for synthesis of growth factors by target tissues. Both cell therapy and gene therapy have proven to be effective to promote neovascularization in various animal models. Cell therapy alone is proven to be beneficial however the combination of cell and gene therapy (growth factors) may enhance therapeutic neovascularization. Thus clinically relevant, combined strategy could be an excellent strategy for treating patients with myocardial infarction.

Therapeutic angiogenesis in cardiovascular disease

Atherosclerotic disease of the arteries is a major cause of coronary artery disease, peripheral vascular disease and stroke. Some patients are however not candidate for the standard treatment of angioplasty or bypass surgery. Hence there is tremendous enthusiasm for the utilization of angiogenesis as a therapeutic modality for atherosclerotic arterial disease. This augmentation of physiological neo-vascularization in cardiovascular disease can be achieved through different pathways. In this article we are reviewing the Use of Gene therapy, Protein therapy and cellular therapy.

Neovascularization of ischemic myocardium by newly isolated tannins prevents cardiomyocyte apoptosis and improves cardiac function

During remodeling progress post myocardial infarction, the contribution of neoangiogenesis to the infarct-bed capillary is insufficient to support the greater demands of the hypertrophied but viable myocardium resulting in further ischemic injury to the viable cardiomyocytes at risk. Here we reported the bio-assay-guided identification and isolation of angiogenic tannins (angio-T) from Geum japonicum that induced rapid revascularization of infarcted myocardium and promoted survival potential of the viable cardiomyocytes at risk after myocardial infarction. Our results demonstrated that angio-T displayed potent dual effects on up-regulating expression of angiogenic factors, which would contribute to the early revascularization and protection of the cardiomyocytes against further ischemic injury, and inducing antiapoptotic protein expression, which inhibited apoptotic death of cardiomyocytes in the infarcted hearts and limited infarct size. Echocardiographic studies demonstrated that angio-T-induced therapeutic effects on acute infarcted myocardium were accompanied by significant functional improvement by 2 days after infarction. This improvement was sustained for 14 days. These therapeutic properties of angio-T to induce early reconstitution of a blood supply network, prevent apoptotic death of cardiomyocytes at risk, and improve heart function post infarction appear entirely novel and may provide a new dimension for therapeutic angiogenesis medicine for the treatment of ischemic heart diseases.

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.

Neovascularization of ischemic myocardium by newly isolated tannins prevents cardiomyocyte apoptosis and improves cardiac function

During remodeling progress post myocardial infarction, the contribution of neoangiogenesis to the infarct-bed capillary is insufficient to support the greater demands of the hypertrophied but viable myocardium resulting in further ischemic injury to the viable cardiomyocytes at risk. Here we reported the bio-assay-guided identification and isolation of angiogenic tannins (angio-T) from Geum japonicum that induced rapid revascularization of infarcted myocardium and promoted survival potential of the viable cardiomyocytes at risk after myocardial infarction. Our results demonstrated that angio-T displayed potent dual effects on up-regulating expression of angiogenic factors, which would contribute to the early revascularization and protection of the cardiomyocytes against further ischemic injury, and inducing antiapoptotic protein expression, which inhibited apoptotic death of cardiomyocytes in the infarcted hearts and limited infarct size. Echocardiographic studies demonstrated that angio-T-induced therapeutic effects on acute infarcted myocardium were accompanied by significant functional improvement by 2 days after infarction. This improvement was sustained for 14 days. These therapeutic properties of angio-T to induce early reconstitution of a blood supply network, prevent apoptotic death of cardiomyocytes at risk, and improve heart function post infarction appear entirely novel and may provide a new dimension for therapeutic angiogenesis medicine for the treatment of ischemic heart diseases.

Repair of Infarcted Myocardium by an Extract of Geum japonicum with Dual Effects on Angiogenesis and Myogenesis

Background: It has become apparent recently that cardiac myocytes can divide after myocardial infarction, a circumstance that challenges the orthodox view that myocytes may be terminally differentiated. Replacement of the necrosed heart tissue by newly regenerated functional myocardium is a therapeutic ideal, but attempts to reconstitute functional myocardia and coronary vessels have been less successful.

Methods: We isolated a fraction containing 5 compounds from the Chinese herb Geum japonicum, which stimulates the processes of angiogenesis and cardiomyogenesis. We investigated these dual properties in both ex vivo and in vivo systems.

Results: We observed that this bioactive fraction displayed favorable dual actions on early angiogenesis and cardiomyogenesis in acute myocardial infarction in an animal model. Our results demonstrated that application of this bioactive fraction showed pronounced effects on limiting infarct size by 35%–45%, stimulating early development of new blood vessels in 24 h, and regenerating myocardium, replacing ∼49% of the total infarction volume after 2 weeks. Echocardiographic studies demonstrated marked improvement of left ventricular function within 2 days after infarction, and the improvement was sustained for >1 month.

Conclusions: The properties of this bioactive fraction appear to be entirely novel and represent a new approach for the treatment of ischemic heart disease.

Highly stable mutants of human fibroblast growth factor-1 exhibit prolonged biological action

Fibroblast growth factor 1 (FGF-1) shows strong angiogenic, osteogenic and tissue-injury repair properties that might be relevant to medical applications. Since FGF-1 is partially unfolded at physiological temperature we decided to increase significantly its conformational stability and test how such an improvement will affect its biological function. Using an homology approach and rational strategy we designed two new single FGF-1 mutations: Q40P and S47I that appeared to be the most strongly stabilizing substitutions among those reported so far, increasing the denaturation temperature by 7.8 deg. C and 9.0 deg. C, respectively. As our goal was to produce highly stable variants of the growth factor, we combined these two mutations with five previously described stabilizing substitutions. The multiple mutants showed denaturation temperatures up to 27 deg. C higher than the wild-type and exhibited full additivity of the mutational effects. All those mutants were biologically competent in several cell culture assays, maintaining typical FGF-1 activities, such as binding to specific cell surface receptors and activation of downstream signaling pathways. Thus, we demonstrate that the low denaturation temperature of wild-type FGF-1 is not related to its fundamental cellular functions, and that FGF-1 action is not affected by its stability. A more detailed analysis of the biological behavior of stable FGF-1 mutants revealed that, compared with the wild-type, their mitogenic properties, as probed by the DNA synthesis assay, were significantly increased in the absence of heparin, and that their half-lives were extensively prolonged. We found that the biological action of the mutants was dictated by their susceptibility to proteases, which strongly correlated with the stability. Mutants which were much more resistant to proteolytic degradation always displayed a significant improvement in the half-life and mitogenesis. Our results show that engineered stable growth factor variants exhibit enhanced and prolonged activity, which can be advantageous in terms of the potential therapeutic applications of FGF-1.

FGF-1: a human growth factor in the induction of neoangiogenesis

Currently available approaches for treating human coronary heart disease aim to relieve symptoms and the risk of myocardial infarction either by reducing myocardial oxygen demand, preventing further disease progression, restoring coronary blood flow pharmacologically or mechanically, or bypassing the stenotic lesions and obstructed coronary artery segments. Gene therapy, especially using angiogenic growth factors, has emerged recently as a potential new treatment for cardiovascular disease. Following extensive experimental research on angiogenic growth factors, the first clinical studies on patients with coronary heart disease and peripheral vascular lesions have been performed. The polypeptides fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) appear to be particularly effective in initiating neovascularisation (neo-angiogenesis) in hypoxic or ischaemic tissues. The first clinical study on patients with coronary heart disease treated by local intramyocardial injection of FGF-1 showed a 3-fold increase of capillary density mediated by the growth factor. Angiogenic therapy of the human myocardium introduces a new modality of treatment for coronary heart disease in terms of regulation of blood vessel growth. Beyond drug therapy, angioplasty and bypass surgery, this new approach may evolve into a fourth principle of treatment of atherosclerotic cardiovascular disease.

Angiogenic strategy for human ischemic heart disease: brief overview

In the Western World ischemic coronary disease is the leading cause of morbidity and mortality. Therapeutic approaches mostly aim to restore flow to a localized segment by angioplasty or bypass surgery. Therapeutic angiogenesis and or arteriogenesis describes a strategy where blood vessel formation is induced for the purposes of treating and/or preventing ischemic disease. At present, at least 17 clinical trials of myocardial angiogenesis have been presented involving over 900 patients. Therapeutic angiogenesis makes use of the administration of angiogenic growth factor protein or gene to promote the development of endogenous collateral vessels in ischemic myocardium. Most recently, interest has grown in the potential angiogenesis effects of cell therapy--such as autologous bone marrow cells or cultured stem cells--and there are now several groups initiating phase I/II trials in this area.

Angiogenic signal during cardiac repair

Despite significant advances in myocardial revascularization and reperfusion, coronary artery disease and subsequently myocardial infarction, are the leading causes of morbidity and mortality in the United States. Strategies which improve the myocardial substrate during and following a myocardial infarction-such as the regrowth of functional blood vessels to the ischemic myocardium would be of great clinical importance. This review article attempts to address this important clinical issue through identifying potential signalling mechanisms by various mode of preconditioning that cause angiogenesis.

Granulocyte-macrophage colony-stimulating factor-induced arteriogenesis reduces energy failure in hemodynamic stroke

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a powerful arteriogenic factor in the hypoperfused rat brain. To test the pathophysiological relevance of this response, the influence of GM-CSF on brain energy state was investigated in a model of hemodynamic stroke. Sprague-Dawley rats were submitted to three-vessel (bilateral vertebral and unilateral common carotid artery) occlusion (3-VO) to induce unilaterally accentuated brain hypoperfusion. One week later, hemodynamic stroke was induced by additional lowering of arterial blood pressure. Experiments were terminated by in situ freezing of the brain. ATP was measured in cryostat sections by using a bioluminescence method. The use of 3-VO, in combination with 15 min of hypotension of 50, 40, or 30 mmHg, did not produce disturbances of energy metabolism, however, focal areas of ATP depletion were unilaterally detected after 3-VO, in combination with 15 min of hypotension of 20 mmHg. Treating such animals with GM-CSF (40 microg.kg(-1).d(-1)) during the 1-week interval between 3-VO and induced hypotension significantly reduced the hemispheric volume of energy depletion from 48.8 +/- 44.2% (untreated group, n = 10) to 15.8 +/- 17.4% (treated group, n = 8, P = 0.033). GM-CSF-induced arteriogenesis is another approach to protect the brain against ischemic injury.

Potential role for antiangiogenic proteins in the myocardial infarction repair process

OBJECTIVE

Although angiogenic proteins have been identified as positive modulators of myocardial revascularization following acute myocardial infarction, little if anything is known regarding the role that antiangiogenic proteins have in myocardial revascularization. We explored the temporospatial distribution of endothelial-monocyte activating polypeptide (EMAP) II to determine whether antiangiogenic proteins have a role in the repair of myocardial tissue following infarction.

METHODS

A rat model of myocardial infarction was utilized to examine EMAP II distribution (in situ hybridization) and protein expression (Western analysis) over a 6-week period.

RESULTS

At baseline, EMAP II protein and mRNA are minimally expressed with transcription products localizing predominately to the perivascular stroma region in the normal rat myocardium. Six hours following myocardial infarction, EMAP II changes its distribution from the perivascular stroma to an invading inflammatory cell population. This is associated with a 2-fold (P < 0.0009) increase in EMAP II protein and its transcription primarily localized to the infarct region. EMAP II protein expression remains elevated throughout the weeks following the infarction with transcription limited to the infarct region and a notable decrease in EMAP II transcription products noted in the viable vasculature surrounding the infarct zone. Six weeks following myocardial infarction, EMAP II protein is elevated above control, changes its location of transcription from the inflammatory cell population to that of the fibroblasts located in the relative avascular scar tissue, and has resumed its perivascular stromal distribution in the viable periinfarct tissue.

CONCLUSIONS

Thus, the temporospatial distribution of this antiangiogenic protein suggests that negative vascular modulators may have a function in the revascularization process following acute myocardial infarction.

Current perspectives in therapeutic myocardial angiogenesis

The complex mechanisms mediating the development of new blood vessels are now beginning to be unraveled. In conjunction with major biotechnology advances, this has facilitated the initiation of translational research related to a novel treatment strategy for patients with myocardial or leg ischemia due to obstructive arterial disease--therapeutic angiogenesis. At present, at least 17 clinical trials of myocardial angiogenesis have been presented involving over 900 patients. Uncertainty exists as to the optimal delivery route and angiogenic agent, and this uncertainty is reflected in the diverse methodology of the trials published thus far. The majority of patients received an angiogenic protein via the intracoronary route. Other delivery techniques--such as direct intramyocardial injection via transepicardial or transendocardial routes--and other angiogenic agents, including master genes, have also been studied. Most recently, interest has grown in the potential angiogenesis effects of cell therapy--such as autologous bone marrow cells or cultured stem cells--and there are now several groups initiating Phase I/II trials in this area. This review summarizes the current evidence pertaining to the safety, feasibility, and efficacy of various angiogenic techniques aimed at enhancing myocardial blood flow and alleviating angina.

Gene-based therapeutic angiogenesis

Stimulating new blood vessel growth in ischemic hearts or limbs is a hopeful new approach for patients with advanced vascular disease. This approach is based generally upon the hypothesis that sufficient exposure of a vascular bed to an angiogenic protein will stimulate neovascularization. Most angiogenic proteins have a markedly short serum half-life. To overcome this, researchers have turned to gene therapy to ensure continuous expression of angiogenic proteins and prolonged exposure in the targeted vascular beds. This field is still evolving, and although early clinical trial results suggest angiogenic gene therapy can be successful, many questions remain. As we continue to learn more about the complex interplay and coordinated action of the various factors involved in regulating angiogenesis, it is likely that strategies for therapeutic angiogenesis will continue to change. This review addresses the current state of angiogenic gene therapy, contrasts gene therapy with angiogenic protein delivery, describes early and recent clinical trial data, and discusses potential new directions in the field.

Invasive and non-invasive evaluation of spontaneous arteriogenesis in a novel porcine model for peripheral arterial obstructive disease

Our current knowledge regarding the efficacy of factors stimulating collateral artery growth in the peripheral circulation primarily stems from models in small animals. However, experimental models in large sized animals are a prerequisite for extrapolation of growth factor therapy to patients with peripheral atherosclerotic obstructive disease. Therefore, we have developed a novel porcine femoral artery ligation model using non-invasive and invasive evaluation techniques. In 12 young farm pigs and nine older minipigs, a ligation of the superficial femoral artery was performed. Using an intra-arterial catheter, phosphate buffered saline (PBS) was administered with a first-pass over the collateral vascular bed. Directly after ligation as well as after 2 weeks of continuous infusion of PBS, perfusion of the leg was measured using various flow and pressure parameters. Using a pump driven extracorporal system, collateral conductance was determined under maximal vasodilatation. Conductance decreased after acute ligation to similar levels in both young farm pigs as well as the older minipigs (both 9.3% of normal perfusion) and recovered after 2 weeks to a higher value in farm pigs compared with minipigs (22.4 vs. 12.7% of normal; P<0.05). Angiography using both X-ray and magnetic resonance imaging was performed to visualize the formed collateral arteries. To the best of our knowledge this is the first in vivo pig model for hemodynamic assessment of growth of collateral arteries in the peripheral circulation, that is suitable for evaluation of arteriogenic effects of growth factors or genes.

Angiogenesis of the heart

Despite continued advances in the prevention and treatment of coronary artery disease, there are still a large number of patients who are not candidates for the conventional revascularization techniques of balloon angioplasty and stenting, or coronary artery bypass grafting (CABG). Therapeutic angiogenesis, in the form of the administration of growth factor protein or gene therapy, has emerged as a promising new method of treatment for patients with coronary artery disease. The goal of this strategy is to promote the development of supplemental blood conduits that will act as endogenous bypass vessels. New vessel formation occurs through the processes of angiogenesis, vasculogenesis, and arteriogenesis, under the control of growth factors such as those that belong to the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and angiopoeitin (Ang) families of molecules. Preclinical studies have suggested that such an approach is both feasible and effective; however many questions remain to be answered. This review will address the elements of pharmacologic revascularization, focusing on gene and protein-based therapy. The important growth factors, the vector (for gene therapy), routes of delivery, the desired therapeutic effect, and quantifiable clinical end points for trials of angiogenesis will all be addressed.

Very-low-dose combination of the angiotensin-converting enzyme inhibitor perindopril and the diuretic indapamide induces an early and sustained increase in neovascularization in rat ischemic legs

After acute ischemia of tissues, neovascularization must be sufficient and fast enough to preserve tissue integrity and organ function, and may thus be considered as a therapeutic strategy. This study examined the possible role of the very-low-dose combination of perindopril (angiotensin-converting enzyme inhibitor) and indapamide (diuretic), used first-line in the treatment of essential hypertension, on ischemia-induced angiogenesis. Ischemia was produced by artery femoral occlusion in rats treated or not with the very-low-dose combination (perindopril 0.76 mg/kg/day + indapamide 0.24 mg/kg/day) or each component given alone at the same dosage for 3 and 28 days. At day 3, angiographic vessel density and laser Doppler perfusion data showed significant improvement in ischemic/nonischemic leg ratio by, respectively, 1.9-fold and 1.5-fold in rats treated with the very-low-dose combination when compared with controls (p < 0.05). This was associated with an increase in vascular endothelial growth factor (VEGF; 2.2-fold) and endothelial nitric-oxide synthase (1.6-fold) protein content in the ischemic hindlimb, assessed by Western blot. At day 28, the very-low-dose combination (3- and 1.6-fold) and perindopril alone (1.8- and 1.4-fold) and indapamide alone (2.0- and 1.4-fold) increased the angiograhic score and blood flow perfusion, respectively, in reference to controls (p < 0.05). Furthermore, addition of VEGF-neutralizing antibody (2.5 microg/kg twice a week) or NOS inhibitor (N(G)-nitro-L-arginine methyl ester, 10 mg/kg/day) prevented the pro-angiogenic effect induced by the perindopril/indapamide combination. The very-low-dose combination of perindopril and indapamide induces an early and sustained effect on the revascularization process observed in ischemic tissue and may provide a favorable therapeutic neovascularization after ischemia.

Direct fibrin injection to promote new collateral growth in hind limb ischemia in a rabbit model

Local stimulation of angiogenesis is a new approach for the treatment of critical limb ischemia. Our investigation tested intramuscular (i.m.) injection of a modified fibrin meshwork in a rabbit model.

METHODS

The left external iliac and femoral arteries were excised in 24 rabbits that were divided into four groups: control; i.m. saline injection; fibrin meshwork plus low dose (2.5 mg) fibrinogen i.m.; fibrin meshwork plus high-dose (5.0 mg) fibrinogen i.m. Angiography was performed before surgery, immediately after surgery, and one month postoperatively. Lower limb-calf blood pressure was measured immediately after surgery and at postoperative days 10, 20, and 30. On day 30, conventional indirect immunostaining was performed to determine the percentage of the area occupied by capillaries.

RESULTS

Immediately after surgery, in all four groups, the number of contract-opacified arteries (COA) crossing a specific segment of a grid decreased from 5.3 +/- 1.3 to 3.2 +/- 1.0 (p < 0.05); the number of grid intersections decreased from 30.2 +/- 6.5 to 19.3 +/- 4.8 (p < 0.05); and the total number of grids with COA decreased from 18.3 +/- 3.8 to 12.2 +/- 2.5 (p < 0.05). One month after surgery, in the control group, these parameters were 6.2 +/- 1.1, 33.2 +/- 5.7 and 20.3 +/- 1.5, respectively; in the saline-treated group, these parameters were 6.1 +/- 0.8, 28.3 +/- 6.9 and 19.8 +/- 1.1, respectively (p > 0.05 versus control and versus baseline data). When fibrin containing 5.0 mg fibrinogen was used, these parameters increased to 8.5 +/- 0.9, 48.3 +/- 5.1, and 27.1 +/- 0.9, respectively (p < 0.001 versus immediately after surgery and p < 0.05 versus control). In all four series, no Doppler flow signal was detected from the posterior tibial artery by day 10. By day 30, the lower limb-calf blood pressure ratio had improved in all four series, but was significantly improved in only the two groups treated with fibrin sealant (0.3 +/- 0.05 control; 0.3 +/- 0.08 saline; 0.6 +/- 0.06 fibrinogen 2.5; 0.7 +/- 0.05 fibrinogen 5.0).

CONCLUSION

Intramuscular injection of a fibrin meshwork considerably increased angiogenesis in the severely ischemic hind limb and may be strongly recommended for clinical use in patients with limb-threatening ischemia.

Redox signaling of angiogenesis

Reactive oxygen species (ROS) play a crucial role in vascular angiogenesis. Both in vitro and in vivo studies indicate that angiogenic response in vascular tissue is triggered by ROS signaling in a highly coordinated manner. It appears that massive amounts of ROS produced during ischemia and reperfusion in the vascular tissue, especially in heart, cause significant injury to the cardiomyocyte and endothelial cells. However, during the reperfusion, the same ROS potentiates a repair process and triggers a signal transduction cascade leading to angiogenesis. Although several other factors are likely to be involved for such angiogenic response, ROS certainly plays a crucial role as evident from its direct role as mediator of angiogenesis and inhibition of angiogenesis with free radical scavengers and/or antioxidants. Angiogenesis is regulated by redox-sensing transcription factors such as nuclear factor-kappaB, and oxidants such as hydrogen peroxide and free radicals, such as nitric oxide may function as second messengers in this highly coordinated process. Furthermore, expression of many angiogenic genes including those for vascular endothelial growth factor, fibroblast growth factor, platelet-derived growth factor, and receptors such as Flt-1, Flk-1, Ang-1, and Ang-2 are likely to be regulated by redox signaling. It is tempting to speculate that the angiogenic response is under the autocrine and/or paracrine control of one or more cytokines, which in turn is redox-regulated. Through angiogenesis, ROS appear to pave the way of repairing the vascular tissues that have been damaged during ischemia and reperfusion.

Therapeutic angiogenesis in critical limb and myocardial ischemia

Research in animal models of ischemia has shown that administration of angiogenic growth factors, either as a recombinant protein or by gene transfer, can augment nutrient perfusion through neovascularization to promote the development of supplemental collateral blood vessels that will constitute endogenous bypass conduits around occluded native arteries; a strategy termed "therapeutic angiogenesis." In animal models and clinical trials, the best studied cytokines with angiogenic activity are vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Clinical trials of therapeutic angiogenesis in patients with critical limb ischemia demonstrated resolution of rest pain and/or improved limb integrity, increased pain-free walking time and ankle-brachial index, newly visible collateral vessels by digital subtraction angiography, and qualitative evidence of improved distal flow by magnetic resonance imaging. Initial clinical trials in patients with end-stage coronary artery disease using direct myocardial injection via thoracotomy resulted in large increases in exercise time and marked reductions in anginal symptoms, as well as objective evidence of improved perfusion and left ventricular function. Larger scale placebo-controlled trials have been limited to intracoronary and intravenous administration of recombinant protein, and have not shown significant improvement in exercise time or angina compared to placebo. Larger scale placebo-controlled studies of gene transfer using catheter-based endocardial delivery are in progress. Future clinical studies are required to determine the optimal dose, formulation, route of administration, and combinations of growth factors, as well as the requirement for endothelial progenitor cell or stem cell supplementation, to provide effective and safe therapeutic angiogenesis for patients with critical limb ischemia and chronic myocardial ischemia who are not candidates for conventional revascularization procedures.

[Growth factors for therapeutic angiogenesis in cardiovascular diseases]

Therapeutic angiogenesis based on the administration of growth factors with angiogenic activity allows enhancement of collateral vessels able to palliate insufficient tissue perfusion secondary to obstruction of native arteries. At present, this type of therapy is addressed to patients that fail to respond to conventional treatment (surgical or percutaneous revascularization). The most extensively investigated angiogenic growth factors are vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). These cytokines can be administered either as recombinant proteins or as the genes encoding for these proteins. Both approaches have pros and cons that are under investigation in animal models and in clinical studies. Although clinical trials consist so far of small, often non-randomized series, preliminary results are promising. For example, administration of VEGF or FGF has been associated to objective evidence of increased tissue perfusion in patients with myocardial ischemia, and to a significant improvement of pain and ischemia in patients with peripheral arterial disease. Contrarily to expected, these interventions have been associated to scant adverse side effects, although larger clinical trials will be necessary in order to prove the safety and effectiveness of these interventions. Nevertheless, it seems clear that it is feasible to induce effective therapeutic angiogenesis in selected patients without significant associated toxicity.

Targeting kinin receptors for the treatment of tissue ischaemia

Kinins, the biological end-products of the kallikrein-kininogen system, influence many aspects of the cellular function. Interest in this peptidergic system has been renewed recently by the discovery that kinins exert cardiovascular protective effects and promote post-ischaemic recovery by stimulating vascular growth. Pharmacological and genetic studies indicate that induction of kallikrein and kinin receptors by ischaemia is functionally relevant in the natural host response that permits perfusion recovery and tissue healing. Furthermore, potentiation of the generation of kinins by continuous supply of tissue kallikrein promotes reparative angiogenesis through stimulation of the release of nitric oxide and prostaglandins. Strategies that activate kinin receptors might be applicable to the treatment of occlusive vascular disease, whereas kinin receptor antagonists could represent therapeutic reagents against pathological angiogenesis in cancer and chronic inflammatory conditions.

Angiogenesis gene therapy to rescue ischaemic tissues: achievements and future directions

Ischaemic diseases are characterized by an impaired supply of blood resulting from narrowed or blocked arteries that starve tissues of needed nutrients and oxygen. Coronary-atherosclerosis induced myocardial infarction is one of the leading causes of mortality in developed countries. Ischaemic disease also affects the lower extremities. Considerable advances in both surgical bypassing and percutaneous revascularization techniques have been reached. However, many patients cannot benefit from these therapies because of the extension of arterial occlusion and/or microcirculation impairment. Consequently, the need for alternative therapeutic strategies is compelling. An innovative approach consists of stimulating collateral vessel growth, a natural host defence response that intervenes upon occurrence of critical reduction in tissue perfusion (Isner & Asahara, 1999). This review will debate the relevance of therapeutic angiogenesis for promotion of tissue repair. The following issues will receive attention: (a) vascular growth patterns, (b) delivery systems for angiogenesis gene transfer, (c) achievements of therapeutic angiogenesis in myocardial and peripheral ischaemia, and (d) future directions to improve effectiveness and safety of vascular gene therapy.

Effects of liposome-mediated gene transfer of VEGF in ischemic rat gracilis muscle

The purpose of the current study was to determine the effects of vascular endothelial growth factor (VEGF) on muscle flap survival and vascularity in a rat gracilis ischemia-reperfusion model. A total of 12 adult male Wistar rats were divided into two groups (n = 6). The experimental group received the plasmid encoding VEGF(165) cDNA plus lipofectamine (cationic liposome) injected directly to the gracilis muscle following 4 h of ischemia. The control group received lipofectamine only. The viability and vascularity of the flaps were evaluated after 7 days of reperfusion. The data demonstrated that the VEGF plasmid- and lipofectamine-treated muscle flaps had significantly greater total survival and capillary count 7 days after reperfusion compared with the flaps treated only with lipofectamine. These results indicate that VEGF exerts a protective effect on ischemic skeletal muscle flaps.