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

Mechanistic, technical, and clinical perspectives in therapeutic stimulation of coronary collateral development by angiogenic growth factors

Stimulation of collateral vessel development in the heart by angiogenic growth factor therapy has been tested in animals and humans for almost two decades. Discordance between the outcome of preclinical studies and clinical trials pointed to the difficulties of translation from animal models to patients. Lessons learned in this process identified specific mechanistic, technical, and clinical hurdles, which need to be overcome. This review summarizes current understanding of the mechanisms leading to the establishment of a functional coronary collateral network and the biological processes growth factor therapies should stimulate even under conditions of impaired natural adaptive vascular response. Vector delivery methods are recommended to maximize angiogenic gene therapy efficiency and reduce side effects. Optimization of clinical trial design should include the choice of clinical end points which provide mechanistic proof-of-concept and also reflect clinical benefits (e.g., surrogates to assess increased collateral flow reserve, such as myocardial perfusion imaging). Guidelines are proposed to select patients who may respond to the therapy with high(er) probability. Both short and longer term strategies are outlined which may help to make therapeutic angiogenesis (TA) work in the future.

Catheter-based intramyocardial delivery (NavX) of adenovirus achieves safe and accurate gene transfer in pigs

BACKGROUND

Hepatocyte growth factor (HGF) is one of the major angiogenic factors being studied for the treatment of ischemic heart diseases. Our previous study demonstrated adenovirus-HGF was effective in myocardial ischemia models. The first clinical safety study showed a positive effect in patients with severe and diffused triple coronary disease.

METHODS

12 Pigs were randomized (1:1) to receive HGF, which was administered as five injections into the infarcted myocardium, or saline (control group). The injections were guided by EnSite NavX left ventricular electroanatomical mapping.

RESULTS

The catheter-based injections caused no pericardial effusion, malignant arrhythmia or death. During mapping and injection, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, serum creatinine and creatine kinase-MB levels have no significant increase as compared to those before and after the injection in HGF group(P>0.05). HGF group has high HGF expression with Western blot, less myocardial infarct sizes by electroanatomical mapping (HGF group versus after saline group, 5.28 ± 0.55 cm(2) versus 9.06 ± 1.06 cm(2), P<0.01), better cardiac function with Gated-Single Photon Emission Computed Tomography compared with those in saline group. Histological, strongly increased lectin-positive microvessels and microvessel density were found in the myocardial ischemic regions in HGF group.

CONCLUSION

Intramyocardial injection guided by NavX system provides a method of feasible and safe percutaneous gene transfer to myocardial infarct regions.

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.

Novel therapy for myocardial infarction: can HGF/Met be beneficial?

Myocardial infarction (MI) is a leading cause of hospitalization worldwide. A recently developed strategy to improve the management of MI is based on the use of growth factors which are able to enhance the intrinsic capacity of the heart to repair itself or regenerate after damage. Among others, hepatocyte growth factor (HGF) has been proposed as a modulator of cardiac repair of damage due to the pleiotropic effects elicited by Met receptor stimulation. In this review we describe the mechanistic basis for autocrine and paracrine protection of HGF in the injured heart. We also analyse the role of HGF/Met in stem cell maintenance and in stem cell therapies for MI. Finally, we summarize the most significant results on the use of HGF in experimental models of heart injury and discuss the potential of the molecule for treating ischaemic heart disease in humans.

Nonviral gene delivery to mesenchymal stem cells using cationic liposomes for gene and cell therapy

Mesenchymal stem cells (MSCs) hold a great promise for application in several therapies due to their unique biological characteristics. In order to harness their full potential in cell-or gene-based therapies it might be advantageous to enhance some of their features through gene delivery strategies. Accordingly, we are interested in developing an efficient and safe methodology to genetically engineer human bone marrow MSC (BM MSC), enhancing their therapeutic efficacy in Regenerative Medicine. The plasmid DNA delivery was optimized using a cationic liposome-based reagent. Transfection efficiencies ranged from ~2% to ~35%, resulting from using a Lipid/DNA ratio of 1.25 with a transgene expression of 7 days. Importantly, the number of plasmid copies in different cell passages was quantified for the first time and ~20,000 plasmid copies/cell were obtained independently of cell passage. As transfected MSC have shown high viabilities (>90%) and recoveries (>52%) while maintaining their multipotency, this might be an advantageous transfection strategy when the goal is to express a therapeutic gene in a safe and transient way.