Gene transfection with human hepatocyte growth factor complementary DNA plasmids attenuates cardiac remodeling after acute myocardial infarction in goat hearts implanted with ventricular assist devices

Cardiac stem cells: Current knowledge and future prospects

Regenerative medicine is the field concerned with the repair and restoration of the integrity of damaged human tissues as well as whole organs. Since the inception of the field several decades ago, regenerative medicine therapies, namely stem cells, have received significant attention in preclinical studies and clinical trials. Apart from their known potential for differentiation into the various body cells, stem cells enhance the organ's intrinsic regenerative capacity by altering its environment, whether by exogenous injection or introducing their products that modulate endogenous stem cell function and fate for the sake of regeneration. Recently, research in cardiology has highlighted the evidence for the existence of cardiac stem and progenitor cells (CSCs/CPCs). The global burden of cardiovascular diseases’ morbidity and mortality has demanded an in-depth understanding of the biology of CSCs/CPCs aiming at improving the outcome for an innovative therapeutic strategy. This review will discuss the nature of each of the CSCs/CPCs, their environment, their interplay with other cells, and their metabolism. In addition, important issues are tackled concerning the potency of CSCs/CPCs in relation to their secretome for mediating the ability to influence other cells. Moreover, the review will throw the light on the clinical trials and the preclinical studies using CSCs/CPCs and combined therapy for cardiac regeneration. Finally, the novel role of nanotechnology in cardiac regeneration will be explored.

Cardiac stem cells: Current knowledge and future prospects

Regenerative medicine is the field concerned with the repair and restoration of the integrity of damaged human tissues as well as whole organs. Since the inception of the field several decades ago, regenerative medicine therapies, namely stem cells, have received significant attention in preclinical studies and clinical trials. Apart from their known potential for differentiation into the various body cells, stem cells enhance the organ's intrinsic regenerative capacity by altering its environment, whether by exogenous injection or introducing their products that modulate endogenous stem cell function and fate for the sake of regeneration. Recently, research in cardiology has highlighted the evidence for the existence of cardiac stem and progenitor cells (CSCs/CPCs). The global burden of cardiovascular diseases' morbidity and mortality has demanded an in-depth understanding of the biology of CSCs/CPCs aiming at improving the outcome for an innovative therapeutic strategy. This review will discuss the nature of each of the CSCs/CPCs, their environment, their interplay with other cells, and their metabolism. In addition, important issues are tackled concerning the potency of CSCs/CPCs in relation to their secretome for mediating the ability to influence other cells. Moreover, the review will throw the light on the clinical trials and the preclinical studies using CSCs/CPCs and combined therapy for cardiac regeneration. Finally, the novel role of nanotechnology in cardiac regeneration will be explored.

Guidelines for in vivo mouse models of myocardial infarction

Despite significant improvements in reperfusion strategies, acute coronary syndromes all too often culminate in a myocardial infarction (MI). The consequent MI can, in turn, lead to remodeling of the left ventricle (LV), the development of LV dysfunction, and ultimately progression to heart failure (HF). Accordingly, an improved understanding of the underlying mechanisms of MI remodeling and progression to HF is necessary. One common approach to examine MI pathology is with murine models that recapitulate components of the clinical context of acute coronary syndrome and subsequent MI. We evaluated the different approaches used to produce MI in mouse models and identified opportunities to consolidate methods, recognizing that reperfused and nonreperfused MI yield different responses. The overall goal in compiling this consensus statement is to unify best practices regarding mouse MI models to improve interpretation and allow comparative examination across studies and laboratories. These guidelines will help to establish rigor and reproducibility and provide increased potential for clinical translation.

Angiogenic and pleiotropic effects of VEGF165 and HGF combined gene therapy in a rat model of myocardial infarction

Since development of plasmid gene therapy for therapeutic angiogenesis by J. Isner this approach was an attractive option for ischemic diseases affecting large cohorts of patients. However, first placebo-controlled clinical trials showed its limited efficacy questioning further advance to practice. Thus, combined methods using delivery of several angiogenic factors got into spotlight as a way to improve outcomes. This study provides experimental proof of concept for a combined approach using simultaneous delivery of VEGF165 and HGF genes to alleviate consequences of myocardial infarction (MI). However, recent studies suggested that angiogenic growth factors have pleiotropic effects that may contribute to outcome so we expanded focus of our work to investigate potential mechanisms underlying action of VEGF165, HGF and their combination in MI. Briefly, Wistar rats underwent coronary artery ligation followed by injection of plasmid bearing VEGF165 or HGF or mixture of these. Histological assessment showed decreased size of post-MI fibrosis in both—VEGF165- or HGF-treated animals yet most prominent reduction of collagen deposition was observed in VEGF165+HGF group. Combined delivery group rats were the only to show significant increase of left ventricle (LV) wall thickness. We also found dilatation index improved in HGF or VEGF165+HGF treated animals. These effects were partially supported by our findings of c-kit+ cardiac stem cell number increase in all treated animals compared to negative control. Sporadic Ki-67+ mature cardiomyocytes were found in peri-infarct area throughout study groups with comparable effects of VEGF165, HGF and their combination. Assessment of vascular density in peri-infarct area showed efficacy of both–VEGF165 and HGF while combination of growth factors showed maximum increase of CD31+ capillary density. To our surprise arteriogenic response was limited in HGF-treated animals while VEGF165 showed potent positive influence on a-SMA+ blood vessel density. The latter hinted to evaluate infiltration of monocytes as they are known to modulate arteriogenic response in myocardium. We found that monocyte infiltration was driven by VEGF165 and reduced by HGF resulting in alleviation of VEGF-stimulated monocyte taxis after combined delivery of these 2 factors. Changes of monocyte infiltration were concordant with a-SMA+ arteriole density so we tested influence of VEGF165 or HGF on endothelial cells (EC) that mediate angiogenesis and inflammatory response. In a series of in vitro experiments we found that VEGF165 and HGF regulate production of inflammatory chemokines by human EC. In particular MCP-1 levels changed after treatment by recombinant VEGF, HGF or their combination and were concordant with NF-κB activation and monocyte infiltration in corresponding groups in vivo. We also found that both–VEGF165 and HGF upregulated IL-8 production by EC while their combination showed additive type of response reaching peak values. These changes were HIF-2 dependent and siRNA-mediated knockdown of HIF-2α abolished effects of VEGF165 and HGF on IL-8 production. To conclude, our study supports combined gene therapy by VEGF165 and HGF to treat MI and highlights neglected role of pleiotropic effects of angiogenic growth factors that may define efficacy via regulation of inflammatory response and endothelial function.

Hepatocyte growth factor (HGF) and hemodialysis: physiopathology and clinical implications

Hepatocyte growth factor (HGF) is a pleiotropic cytokine which exerts a variety of effects on several cells, being involved in the regulation of many biological processes, such as inflammation, tissue repair, morphogenesis, angiogenesis, tumour propagation, immunomodulation of viral infections and cardio-metabolic activities. Patients undergoing regular hemodialysis (HD) present elevated levels of HGF, mainly due to the leukocyte activation associated with HD treatment. High HGF levels might account for specific clinical features of HD patients, i.e. mild liver damage in course of HCV-infection and high cardiovascular risk profile. Moreover, in patients with acute kidney injury, the induction of HGF may represent a crucial step to promote renal recovery, which can have important prognostic consequences in the short and long-term. In this review we discuss the mechanisms underlying HGF production in HD patients, the role of HGF in this particular patient population and the potential clinical implications derived from the study of HGF in HD patients.

An engineered dimeric fragment of hepatocyte growth factor is a potent c-MET agonist

Hepatocyte growth factor (HGF), through activation of the c-MET receptor, mediates biological processes critical for tissue regeneration; however, its clinical application is limited by protein instability and poor recombinant expression. We previously engineered an HGF fragment (eNK1) that possesses increased stability and expression yield and developed a c-MET agonist by coupling eNK1 through an introduced cysteine residue. Here, we further characterize this eNK1 dimer and show it elicits significantly greater c-MET activation, cell migration, and proliferation than the eNK1 monomer. The efficacy of the eNK1 dimer was similar to HGF, suggesting its promise as a c-MET agonist.

Currently available ventricular-assist devices: capabilities, limitations and future perspectives

The continuous progress in ventricular-assist device (VAD) technology and the management of patients with VADs has broadened the treatment options for end-stage heart failure patients. The available line-up of clinical devices provides the current optimal therapies to meet the specific needs of each patient. The extended durability, safety, efficacy and improved quality of life of the patients provides sufficient proof for the VAD to be a likely alternative therapy to heart transplantation. The sequential progress from the first-, to the second- and to the third-generation VAD technology is expected to bring increasing benefits to clinical outcomes. This article reviews the current status, capabilities, limitations and future perspectives of currently available VADs by generally classifying them via support duration, alignment of pump devices and via pulsatile or nonpulsatile mode of perfusion. Furthermore, the future direction of research and development for next-generation VADs is presented based on the lessons learned from currently available VADs.

Effects of recombinant adenovirus hepatocyte growth factor gene on myocardial remodeling in spontaneously hypertensive rats

BACKGROUND AND OBJECTIVES

Myocardial hypertrophy and fibrosis are important determinants of congestive heart failure. Previous work has shown that hepatocyte growth factor (HGF) can reduce acute myocardial injury and tissue fibrosis. This study was designed to examine the effects of HGF on myocardial remodeling following sustained hypertension.

METHODS AND RESULTS

There were 4 experimental groups (n = 6) that included spontaneously hypertensive rats (SHRs) injected with 0.1 mL of adenovirus (Ad)-null into the left ventricular (LV) free wall, SHR injected with 0.1 mL of Ad-HGF gene (5 × 10(9) pfu/mL), and SHR injected with 0.1 mL of normal saline, and Wistar Kyoto rats injected with 0.1 mL of Ad-null served as control. At 4 weeks after injection, rats were sacrificed, and HGF expression, myocardial fibrosis, and LV function were determined. We observed that HGF protein expression was reduced in the hearts of SHR (P < .05 vs normal control) and it was markedly increased in SHR injected with Ad-HGF (P < .01 vs SHR injected with Ad-null). Myocardial fibrosis, collagen I, LV mass index (LVMI), and LV end-diastolic pressure (LVEDP) were increased and -dP/dtmax was decreased in SHR injected with Ad-null or normal saline (P < .01 vs normal control). Upregulation of myocardial HGF expression in SHR significantly suppressed myocardial fibrosis, collagen I content, LVMI, LVEDP, and increased -dP/dtmax (all P < .05 vs SHR-Ad-null, n = 6).

CONCLUSIONS

These findings indicate that HGF expression is attenuated in hypertrophic and fibrotic myocardium of SHR. The forced increase in HGF exerts a salutary effect on myocardial fibrosis, collagen I expression, and hemodynamic parameters.

Recombinant human hepatocyte growth factor transfection alleviates hyperkinetic pulmonary artery hypertension in rabbit models

OBJECTIVE

The study objective was to investigate the effect of recombinant human hepatocyte growth factor gene transfection via an endotracheal approach on hyperkinetic pulmonary artery hypertension rabbit models.

METHODS

The rabbits with established pulmonary artery hypertension were separated into a gene transfection group (rabbits treated with intratracheal instillation of human hepatocyte growth factor 2 × 10(9) plaque-forming units coded by replication-defective recombinant adenovirus), an empty vector group, and a control group. Two weeks after endotracheal gene transfection, immunohistochemistry examination and Western blot were used to detect the protein expression of human hepatocyte growth factor. The hemodynamic data were measured, and pulmonary angiography was performed to investigate the pulmonary collateral vessels. The vascular density in lung also was analyzed.

RESULTS

Two weeks after gene transfection, human hepatocyte growth factor was expressed in the gene transfection group. The mean pulmonary artery pressure in the gene transfection group was lower than in the control and empty vector groups (P < .05 for both). The arteriolar density in the lung tissues of the gene transfection group was higher than in the other groups (P < .05), which was confirmed by immunohistochemistry, double-labeling immunofluorescence, and pulmonary angiography.

CONCLUSIONS

Human hepatocyte growth factor was expressed in rabbit lung after gene transfection via an airway approach. Recombinant human hepatocyte growth factor transfection ameliorates the pulmonary artery hypertension induced by shunt flow by promoting angiogenesis in lung tissues.

Cardiac gene therapy in large animals: bridge from bench to bedside

Several clinical trials are evaluating gene transfer as a therapeutic approach to treat cardiac diseases. Although it has just started on the path to clinical application, recent advances in gene delivery technologies with increasing knowledge of underlying mechanisms raise great expectations for the cardiac gene therapy. Although in vivo experiments using small animals provide the therapeutic potential of gene transfer, there exist many fundamental differences between the small animal and the human hearts. Before applying the therapy to clinical patients, large animal studies are a prerequisite to validate the efficacy in an animal model more relevant to the human heart. Several key factors including vector type, injected dose, delivery method and targeted cardiac disease are all important factors that determine the therapeutic efficacy. Selecting the most optimal combination of these factors is essential for successful gene therapy. In addition to the efficacy, safety profiles need to be addressed as well. In this regard, large animal studies are best suited for comprehensive evaluation at the preclinical stages of therapeutic development to ensure safe and effective gene transfer. As the cardiac gene therapy expands its potential, large animal studies will become more important to bridge the bench side knowledge to the clinical arena.

Plasmid-mediated gene therapy for cardiovascular disease

Gene transfer within the cardiovascular system was first demonstrated in 1989 yet, despite extensive basic-science and clinical research, unequivocal benefit in the clinical setting remains to be demonstrated. Potential reasons for this include the fact that recombinant viral vectors, used in the majority of clinical studies, have inherent problems with immunogenicity that are difficult to circumvent. Attention has turned therefore to plasmid vectors, which possess many advantages over viruses in terms of safety and ease of use, and many clinical studies have now been performed using non-viral technology. This review will provide an overview of clinical trials for cardiovascular disease using plasmid vectors, recent developments in plasmid delivery and design, and potential directions for this modality of gene therapy.

Ovine models for chronic heart failure

PURPOSE

Testing and optimizing of surgical therapies for chronic heart failure (CHF) requires large animal models. CHF has been induced in several large animal species. Sheep have modest body mass increase and demonstrate docile behavior and are therefore a preferred species in research on surgical therapies for CHF METHODS: A literature search for existing ovine CHF models was performed, using search terms "sheep" and "heart failure". Relevant secondary references were traced.

RESULTS

Rapid ventricular pacing produces rapid-onset CHFE Its severity ranges from moderate left ventricular failure to severe biventricular failure, depending on length and frequency of pacing. Its counterpart in human CHF is tachycardia-induced HF since it is reversible upon cessation of pacing. Myocardial damage models include CHF induced by cardiototoxic drugs and ischemia. Ischemia-based models include coronary microembolization, occlusion and ischemia/reperfusion models. The microembolization model is relevant to diabetic cardiomyopathy. Coronary occlusion models exhibit variable functional impairment, some with aneurysm formation, and some with mitral valve regurgitation, depending on occlusion localization. They are relevant to CHF following non-reperfused myocardial infarction. Coronary occlusion/reperfusion models are relevant to the occurrence of human ãã despite coronary artery recanalization. Pressure overload of left and right ventricle is induced by aortic and pulmonary artery banding, respectively. Hypertrophy precedes CHF as in patients with valve stenosis and hypertension. Volume overload is induced by valve damage or shunt creation. Atrioventricular valve regurgitation is the most important clinical counterpart.

CONCLUSION

Several ovine CHF models exist. Since they exhibit important cardiac pathology differences, the choice of model should be based on the specific experimental question.

Non-viral gene therapy for myocardial engineering

Despite significant advances in surgical and pharmacological techniques, myocardial infarction (MI) remains the main cause of morbidity in the developed world because no remedy has been found for the regeneration of infarcted myocardium. Once the blood supply to the area in question is interrupted, the inflammatory cascade, among other mechanisms, results in the damaged tissue becoming a scar. The goals of cardiac gene therapy are essentially to minimize damage, to promote regeneration, or some combination thereof. While the vector is, in theory, less important than the gene being delivered, the choice of vector can have a significant impact. Viral therapies can have very high transfection efficiencies, but disadvantages include immunogenicity, retroviral-mediated insertional mutagenesis, and the expense and difficulty of manufacture. For these reasons, researchers have focused on non-viral gene therapy as an alternative. In this review, naked plasmid delivery, or the delivery of complexed plasmids, and cell-mediated gene delivery to the myocardium will be reviewed. Pre-clinical and clinical trials in the cardiac tissue will form the core of the discussion. While unmodified stem cells are sometimes considered therapeutic vectors on the basis of paracrine mechanisms of action basic understanding is limited. Thus, only genetically modified cells will be discussed as cell-mediated gene therapy.

Percutaneous transendocardial VEGF gene therapy: MRI guided delivery and characterization of 3D myocardial strain

BACKGROUND

Patients with myocardial infarcts have unfavorable left ventricular (LV) remodeling and devastating outcomes. This study was performed to determine whether VEGF-gene delivered transendocardially under MR-guidance improves LV three-dimensional (3D) strain (circumferential, longitudinal and radial), reduces infarct transmurality and increases vascular density in a canine model of permanent LAD coronary artery occlusion.

METHODS

Imaging was performed using a 1.5-T MR scanner. Three days after occlusion, a percutaneous catheter was advanced under MR-guidance into the LV chamber for transendocardial delivery of VEGF-gene therapy (n=6) or LacZ-gene as control (n=6) into infarcted and peri-infarcted myocardium. MRI was performed before (3 days) and after (50 days) the delivery of therapy using cine, tagged and delayed contrast enhancement. Histochemical and pathological stains were used to assess myocardial viability and vascular density, respectively.

RESULTS

Transendocardial delivery of VEGF-gene therapy and LacZ-gene under MRI guidance was successful in all animals. Significant improvement in 3D strain was observed within 50 days in treated animals. On the other hand, control animals demonstrated deterioration in regional strain over time. Significant reductions in infarct transmurality and increases in capillary and arteriole densities were also observed in VEGF-treated as compared to control animals.

CONCLUSION

MR-guided transendocardial delivery of VEGF-gene improved myocardial strain and enhanced transmural infarct resorption. This minimally invasive technique may be useful for delivery of local therapies, designed to promote angiogenesis or myogenesis.

Quantitative MR measurements of regional and global left ventricular function and strain after intramyocardial transfer of VM202 into infarcted swine myocardium

Previous studies have shown the beneficial effects of the hepatocyte growth factor (HGF) gene on myocardial perfusion and infarction size but not on the regional strain in relationship to global left ventricular function. A noninvasive magnetic resonance (MR) study was performed to determine the effect of a new HGF gene, VM202, expressing two isoforms of HGF, on regional and global left ventricular function. Pigs (8/group) were divided into three groups: 1) controls without infarction; 2) reperfused, infarcted controls; and 3) infarcted, treated (1 h after reperfusion) with VM202 injected at eight sites. Cine, tagging, and delayed enhancement MR images were acquired at 3 and 50 +/- 3 days after infarction. At 50 days, ejection fraction in infarcted, treated animals increased (38 +/- 1% to 47 +/- 2%, P < 0.01) to the level of controls without infarction (52 +/- 1%, P = 0.16) but decreased in infarcted controls (41 +/- 1% to 37 +/- 1%, P < 0.05). Two-dimensional strain improved in remote, peri-infarcted, and infarcted myocardium. Furthermore, the infarction size was smaller in infarcted, treated animals (7.0 +/- 0.5%) compared with infarcted controls (13.2 +/- 1.6%, P < 0.05). Histopathology showed a lack of hypertrophy in myocytes in peri-infarcted and remote myocardium and the formation of islands/peninsulas of myocytes in infarcted, treated animals but not in infarcted controls. In conclusion, the plasmid HGF gene caused a near complete recovery of ejection fraction and improved the radial and circumferential strain of remote, peri-infarcted, and infarcted regions within 50 days. These beneficial effects may be explained by the combined effects of a speedy and significant infarct resorption and island/peninsulas of hypertrophied myocytes within the infarcted territory but not by compensatory hypertrophy. The combined use of cine and tagging MR imaging provides valuable information on the efficacy of gene therapy.

Gene therapy progress and prospects: therapeutic angiogenesis for ischemic cardiovascular disease

During the past decade, both in vitro and in vivo studies have provided new insights into the cellular and molecular mechanisms that govern angiogenesis and arteriogenesis. However, therapeutic angiogenesis clinical trials using recombinant protein or gene therapy formulations of single angiogenic growth factors have yielded at best only modest success to date. Among the second generation of angiogenic agents are therapeutic transgenes that enhance expression of two or more proangiogenic cytokines. These include synthetic constructs that mimic that activity of endogenous transcriptional regulators and other upstream, regulatory factors that have the potential to induce formation of morphologically and physiologically functional vessels. These agents are now beginning to be evaluated in clinical trials for patients with advanced ischemic cardiac and peripheral vascular disease.