Vascular Endothelial Growth Factor C–induced Collateral Formation in a Model of Myocardial Ischemia

Multi-species meta-analysis identifies transcriptional signatures associated with cardiac endothelial responses in the ischaemic heart

AIM

Myocardial infarction remains the leading cause of heart failure. The adult human heart lacks the capacity to undergo endogenous regeneration. New blood vessel growth is integral to regenerative medicine necessitating a comprehensive understanding of the pathways that regulate vascular regeneration. We sought to define the transcriptomic dynamics of coronary endothelial cells following ischaemic injuries in the developing and adult mouse and human heart and to identify new mechanistic insights and targets for cardiovascular regeneration.

METHODS AND RESULTS

We carried out a comprehensive meta-analysis of integrated single-cell RNA-sequencing data of coronary vascular endothelial cells from the developing and adult mouse and human heart spanning healthy and acute and chronic ischaemic cardiac disease. We identified species-conserved gene regulatory pathways aligned to endogenous neovascularization. We annotated injury-associated temporal shifts of the endothelial transcriptome and validated four genes: VEGF-C, KLF4, EGR1, and ZFP36. Moreover, we showed that ZFP36 regulates human coronary endothelial cell proliferation and defined that VEGF-C administration in vivo enhances clonal expansion of the cardiac vasculature post-myocardial infarction. Finally, we constructed a coronary endothelial cell meta-atlas, CrescENDO, to empower future in-depth research to target pathways associated with coronary neovascularization.

CONCLUSION

We present a high-resolution single-cell meta-atlas of healthy and injured coronary endothelial cells in the mouse and human heart, revealing a suite of novel targets with great potential to promote vascular regeneration, and providing a rich resource for therapeutic development.

A Vegfc-Emilin2a-Cxcl8a Signaling Axis Required for Zebrafish Cardiac Regeneration

BACKGROUND

Ischemic heart disease following the obstruction of coronary vessels leads to the death of cardiac tissue and the formation of a fibrotic scar. In contrast to adult mammals, zebrafish can regenerate their heart after injury, enabling the study of the underlying mechanisms. One of the earliest responses following cardiac injury in adult zebrafish is coronary revascularization. Defects in this process lead to impaired cardiomyocyte repopulation and scarring. Hence, identifying and investigating factors that promote coronary revascularization holds great therapeutic potential.

METHODS

We used wholemount imaging, immunohistochemistry and histology to assess various aspects of zebrafish cardiac regeneration. Deep transcriptomic analysis allowed us to identify targets and potential effectors of Vegfc (vascular endothelial growth factor C) signaling. We used newly generated loss- and gain-of-function genetic tools to investigate the role of Emilin2a (elastin microfibril interfacer 2a) and Cxcl8a (chemokine (C-X-C) motif ligand 8a)-Cxcr1 (chemokine (C-X-C) motif receptor 1) signaling in cardiac regeneration.

RESULTS

We first show that regenerating coronary endothelial cells upregulate vegfc upon cardiac injury in adult zebrafish and that Vegfc signaling is required for their proliferation during regeneration. Notably, blocking Vegfc signaling also significantly reduces cardiomyocyte dedifferentiation and proliferation. Using transcriptomic analyses, we identified emilin2a as a target of Vegfc signaling and found that manipulation of emilin2a expression can modulate coronary revascularization as well as cardiomyocyte proliferation. Mechanistically, Emilin2a induces the expression of the chemokine gene cxcl8a in epicardium-derived cells, while cxcr1, the Cxcl8a receptor gene, is expressed in coronary endothelial cells. We further show that Cxcl8a-Cxcr1 signaling is also required for coronary endothelial cell proliferation during cardiac regeneration.

CONCLUSIONS

These data show that after cardiac injury, coronary endothelial cells upregulate vegfc to promote coronary network reestablishment and cardiac regeneration. Mechanistically, Vegfc signaling upregulates epicardial emilin2a and cxcl8a expression to promote cardiac regeneration. These studies aid in understanding the mechanisms underlying coronary revascularization in zebrafish, with potential therapeutic implications to enhance revascularization and regeneration in injured human hearts.

The Role of the VEGF Family in Coronary Heart Disease

The vascular endothelial growth factor (VEGF) family, the regulator of blood and lymphatic vessels, is mostly investigated in the tumor and ophthalmic field. However, the functions it enjoys can also interfere with the development of atherosclerosis (AS) and further diseases like coronary heart disease (CHD). The source, regulating mechanisms including upregulation and downregulation, target cells/tissues, and known functions about VEGF-A, VEGF-B, VEGF-C, and VEGF-D are covered in the review. VEGF-A can regulate angiogenesis, vascular permeability, and inflammation by binding with VEGFR-1 and VEGFR-2. VEGF-B can regulate angiogenesis, redox, and apoptosis by binding with VEGFR-1. VEGF-C can regulate inflammation, lymphangiogenesis, angiogenesis, apoptosis, and fibrogenesis by binding with VEGFR-2 and VEGFR-3. VEGF-D can regulate lymphangiogenesis, angiogenesis, fibrogenesis, and apoptosis by binding with VEGFR-2 and VEGFR-3. These functions present great potential of applying the VEGF family for treating CHD. For instance, angiogenesis can compensate for hypoxia and ischemia by growing novel blood vessels. Lymphangiogenesis can degrade inflammation by providing exits for accumulated inflammatory cytokines. Anti-apoptosis can protect myocardium from impairment after myocardial infarction (MI). Fibrogenesis can promote myocardial fibrosis after MI to benefit cardiac recovery. In addition, all these factors have been confirmed to keep a link with lipid metabolism, the research about which is still in the early stage and exact mechanisms are relatively obscure. Because few reviews have been published about the summarized role of the VEGF family for treating CHD, the aim of this review article is to present an overview of the available evidence supporting it and give hints for further research.

Lymphatic Vascular Structures: A New Aspect in Proliferative Diabetic Retinopathy

Diabetic retinopathy (DR) is the most common diabetic microvascular complication and major cause of blindness in working-age adults. According to the level of microvascular degeneration and ischemic damage, DR is classified into non-proliferative DR (NPDR), and end-stage, proliferative DR (PDR). Despite advances in the disease etiology and pathogenesis, molecular understanding of end-stage PDR, characterized by ischemia- and inflammation-associated neovascularization and fibrosis, remains incomplete due to the limited availability of ideal clinical samples and experimental research models. Since a great portion of patients do not benefit from current treatments, improved therapies are essential. DR is known to be a complex and multifactorial disease featuring the interplay of microvascular, neurodegenerative, metabolic, genetic/epigenetic, immunological, and inflammation-related factors. Particularly, deeper knowledge on the mechanisms and pathophysiology of most advanced PDR is critical. Lymphatic-like vessel formation coupled with abnormal endothelial differentiation and progenitor cell involvement in the neovascularization associated with PDR are novel recent findings which hold potential for improved DR treatment. Understanding the underlying mechanisms of PDR pathogenesis is therefore crucial. To this goal, multidisciplinary approaches and new ex vivo models have been developed for a more comprehensive molecular, cellular and tissue-level understanding of the disease. This is the first step to gain the needed information on how PDR can be better evaluated, stratified, and treated.

Physiological Perspective on Therapies of Lymphatic Vessels

Significance: Growth of distinctive blood vessels of granulation tissue is a central step in the post-developmental tissue remodeling. Even though lymphangiogenesis is a part of the regeneration process, the significance of the controlled restoration of lymphatic vessels has only recently been recognized.

Recent Advances: Identification of lymphatic markers and growth factors paved the way for the exploration of the roles of lymphatic vessels in health and disease. Emerging pro-lymphangiogenic therapies use vascular endothelial growth factor (VEGF)-C to combat fluid retention disorders such as lymphedema and to enhance the local healing process.

Critical Issues: The relevance of recently identified lymphatic functions awaits verification by their association with pathologic conditions. Further, despite a century of research, the complete etiology of secondary lymphedema, a fluid retention disorder directly linked to the lymphatic function, is not understood. Finally, the specificity of pro-lymphangiogenic therapy depends on VEGF-C transfection efficiency, dose exposure, and the age of the subject, factors that are difficult to standardize in a heterogeneous human population.

Future Directions: Further research should reveal the role of lymphatic circulation in internal organs and connect its impairment with human diseases. Pro-lymphangiogenic therapies that aim at the acceleration of tissue healing should focus on the controlled administration of VEGF-C to increase their capillary specificity, whereas regeneration of collecting vessels might benefit from balanced maturation and differentiation of pre-existing lymphatics. Unique features of pre-nodal lymphatics, fault tolerance and functional hyperplasia of capillaries, may find applications outreaching traditional pro-lymphangiogenic therapies, such as immunomodulation or enhancement of subcutaneous grafting.

Cardiac Lymphatics - A New Avenue for Therapeutics?

Recent progress in lymphatic vessel biology and in novel imaging techniques has established the importance of the lymphatic vasculature as part of the cardiovascular system. The lymphatic vessel network regulates many physiological processes important for heart function such as fluid balance, transport of extravasated proteins, and trafficking of immune cells. Therefore, lymphangiogenic therapy could be beneficial in the treatment of cardiovascular diseases, for example by improving reverse cholesterol transport (RCT) from atherosclerotic lesions or by resolving edema and fibrosis after myocardial infarction. In this review we first describe recent findings on the development and function of cardiac lymphatic vessels, and subsequently focus on the prospects of pro- and anti-lymphangiogenic therapies in cardiovascular diseases.

Mild coronary artery stenosis has no impact on cardiac and vascular parameters in miniature swine exposed to positive acceleration stress

BACKGROUND

Exposure of pilots' heart to acceleration-associated stress (+Gz stress) is an adverse effect of high-performance aviation. The occurrence of coronary heart diseases is one of the most frequent medical causes leading to cessation of flying.

AIM

To assess the effects of +Gz stress on coronary artery stenosis (CAS) in a minimally invasive miniature swine model with a fast recovery.

METHODS

The proximal left anterior descending branch was ligated in 20 swine using silk suture. CAS degree (mild, moderate, severe) was analyzed by quantitative computerized angiography. Five swine underwent a sham operation. +Gz stress exposure was performed and venous blood was collected before/after exposure. Plasma C-reactive protein (CRP), endothelin (ET)-1, angiotensin (Ang) II and urotensin 2 (U2) levels were measured.

RESULTS

CAS models were successful in 18 animals. Two swine exhibited ventricular fibrillation during the procedure and died. Plasma CRP, ET-1, Ang II and U2 changed significantly after maximal tolerated +Gz stress exposure (all P < 0.05). After maximal tolerated +Gz stress exposure, plasma CRP, ET-1, Ang II and U2 levels increased in the moderate and severe stenosis groups, compared with the sham group (all P < 0.05), but there was no significant difference between the mild stenosis group and the sham group (all P > 0.05).

CONCLUSION

The fully endoscopic operation method successfully generated animal models of different degrees of CAS. Plasma CRP, ET-1, Ang II and U2 levels increased after +Gz stress exposure with increasing CAS severity. Animals with mild stenosis showed no ill effect under +Gz stress, suggesting that pilots with mild stenosis might be allowed to continue flying, but it must be confirmed in humans.

Optimizing the host substrate environment for cardiac angiogenesis, arteriogenesis, and myogenesis

INTRODUCTION

The diseased host milieu, such as endothelial dysfunction (ED), decreased NO bioavailability, and ischemic/inflammatory post-MI environment, hamper the clinical success of existing cardiac regenerative therapies. Area covered: In this article, current strategies including pharmacological and nonpharmacological approaches for improving the diseased host milieu are reviewed. Specifically, the authors provide focus on: i) the mechanism of ED in patients with cardiovascular diseases, ii) the current results of ED improving strategies in pre-clinical and clinical studies, and iii) the use of biomaterials as a novel modulator in damaged post-MI environment. Expert opinion: Adjunct therapies which improve host endothelial function have demonstrated promising outcomes, potentially overcoming disappointing results of cell therapy in human studies. In the future, elucidation of the interactions between the host tissue and therapeutic agents, as well as downstream signaling pathways, will be the next challenges in enhancing regenerative therapy. More careful investigations are also required to establish these agents' safety and efficacy for wide usage in humans.

Gene therapy to stimulate angiogenesis to treat diffuse coronary artery disease

Cardiac gene therapy offers a strategy to treat diffuse coronary artery disease (CAD), a disorder with no therapeutic options. The use of genes to revascularize the ischemic myocardium has been the focus of two decades of preclinical research with a variety of angiogenic mediators, including vascular endothelial growth factor, fibroblast growth factor, hepatocyte growth factor, and others encoded by DNA plasmids or adenovirus vectors. The multifaceted challenge for developing efficient induction of collateral vessels in the ischemic heart requires a choice for route of delivery, dosing level, a relevant animal model, duration of treatment, and assessment of phenotype for efficacy. Overall, studies of gene therapy for ischemia in experimental models are very encouraging, with clear evidence of safety and efficacy, strongly supporting the concept that gene therapy to induce angiogenesis is a viable therapeutic approach for CAD. Clinical studies of cardiac gene therapy with angiogenic factors have added substantially to the evidence for efficacy, but definitive studies have not yet led to commercial approval. This review provides the general concepts for angiogenesis-based therapeutic approaches for diffuse CAD and summarizes the results from key studies in the field with recommendations for refinement to a successful product design and evaluation.

Cell-based vasculogenic studies in preclinical models of chronic myocardial ischaemia and hibernation

INTRODUCTION

Coronary artery disease commonly leads to myocardial ischaemia and hibernation. Relevant preclinical models of these conditions are essential to evaluate new therapeutic options such as cell-based vasculogenic therapies.

AREAS COVERED

In this article, the authors first review basic concepts of myocardial ischaemia/hibernation and relevant techniques to assess myocardial viability. Then, preclinical models of chronic myocardial ischaemia and hibernation, induced by devices such as ameroid constrictors, Delrin stenosis, hydraulic occluders, and coils/stents are described. Lastly, the authors discuss cell-based vasculogenic therapy, and summarise studies conducted in large animal models of chronic myocardial ischaemia and hibernation.

EXPERT OPINION

Approximately one-third of patients with viable myocardium do not undergo revascularisation; however, this population is at high risk for cardiac events and would surely benefit from effective cell-based therapy. Because of the modest benefits in clinical studies, preclinical models accurately representing clinical myocardial ischemia/hibernation are necessary to better understand and appropriately direct regenerative therapy research.

AAV9-mediated VEGF-B gene transfer improves systolic function in progressive left ventricular hypertrophy

Mechanisms of the transition from compensatory hypertrophy to heart failure are poorly understood and the roles of vascular endothelial growth factors (VEGFs) in this process have not been fully clarified. We determined the expression profile of VEGFs and relevant receptors during the progression of left ventricular hypertrophy (LVH). C57BL mice were exposed to transversal aortic constriction (TAC) and the outcome was studied at different time points (1 day, 2, 4, and 10 weeks). A clear compensatory phase (2 weeks after TAC) was seen with following heart failure (4 weeks after TAC). Interestingly, VEGF-C and VEGF-D as well as VEGF receptor-3 (VEGFR-3) were upregulated in the compensatory hypertrophy and VEGF-B was downregulated in the heart failure. After treatment with adeno-associated virus serotype 9 (AAV9)-VEGF-B(186) gene therapy in the compensatory phase for 4 weeks the function of the heart was preserved due to angiogenesis, inhibition of apoptosis, and promotion of cardiomyocyte proliferation. Also, the genetic programming towards fetal gene expression, a known phenomenon in heart failure, was partly reversed in AAV9-VEGF-B(186)-treated mice. We conclude that VEGF-C and VEGF-D are associated with the compensatory LVH and that AAV9-VEGF-B(186) gene transfer can rescue the function of the failing heart and postpone the transition towards heart failure.

Gene targeting in ischemic heart disease and failure: translational and clinical studies

Alternative and innovative targeted strategies hold relevance in improving the current treatments for ischemic heart disease (IHD). One potential treatment modality, gene targeting, may provide a unique alternative to current IHD therapies. The principal function of gene targeting in IHD is to augment the expression of an endogenous gene through amplification of an exogenous gene, delivered by a plasmid or a viral vector to enhance myocardial perfusion, and limit the long-term sequelae. The initial clinical studies of gene targeting in IHD were focused upon induction of angiogenic factors and the outcomes were equivocal. Nevertheless, significant advancements have been made in viral vectors, mode of delivery, and potentially relevant targets for IHD. Several of these advancements, particularly with a focus on translational large animal studies, are the focus of this review. The development of novel vectors with prolonged transduction efficiency and minimal inflammation, coupled with hybrid perfusion-mapping delivery devices, and improving the safety of vector use and efficacy of gene systems are but a few of the exciting progresses that are likely to proceed to clinical studies in the near future.

Gene delivery technologies for cardiac applications

Ischemic heart disease (IHD) and heart failure (HF) are major causes of morbidity and mortality in the Western society. Advances in understanding the molecular pathology of these diseases, the evolution of vector technology, as well as defining the targets for therapeutic interventions has placed these conditions within the reach of gene-based therapy. One of the cornerstones of limiting the effectiveness of gene therapy is the establishment of clinically relevant methods of genetic transfer. Recently there have been advances in direct and transvascular gene delivery methods with the use of new technologies. Current research efforts in IHD are focused primarily on the stimulation of angiogenesis, modify the coronary vascular environment and improve endothelial function with localized gene-eluting catheters and stents. In contrast to standard IHD treatments, gene therapy in HF primarily targets inhibition of apoptosis, reduction in adverse remodeling and increase in contractility through global cardiomyocyte transduction for maximal efficacy. This article will review a variety of gene-transfer strategies in models of coronary artery disease and HF and discuss the relative success of these strategies in improving the efficiency of vector-mediated cardiac gene delivery.

Assessment of collateral artery function and growth in a pig model of stepwise coronary occlusion

Therapeutic stimulation of collateral artery growth is a promising approach for treatment of cardiovascular diseases. Unfortunately, translation into clinical practice yet remains cumbersome. Cardiovascular physiology and anatomy are major determinants of vascular growth processes. Hence, large-animal models are needed to improve clinical translatability of preclinical research. Furthermore, acute complete occlusions are mostly applied in experimental research, whereas stepwise occlusions are more often observed in human disease. We developed a model of coronary collateral artery growth in which 1) the artery is occluded in a step wise approach, and 2) effects of local treatment can be measured individually for each supplying coronary vessel. A hemodynamically relevant stenosis was created by implantation of a tapered stent at day 0 (d0) in the left circumflex artery (LCX), followed by complete arterial occlusion at day 14 (d14). Fluorescent microspheres were injected for demarcation of perfusion territories at each time point. Three and four weeks after induction of stenosis, collateral conductance measurements were performed for each coronary artery separately using differently labeled fluorescent microspheres. Postmortem angiography after acute LCX occlusion confirmed the presence of preexistent coronary anastomoses in the pig. The tapered stent created a hemodynamically significant stenosis immediately postplacement (fractional flow reserve, 0.70 ± 0.03). Between day 21 and 28, collateral conductance significantly increased in both the left anterior descending (LAD) and the right coronary artery (RCA)-supplied, collateral-dependent territories (LAD d21, 0.77 ± 0.14; LAD d28, 1.35 ± 0.12; RCA d21, 0.88 ± 0.29; RCA d28, 1.70 ± 0.16 ml·min−1·g−1·100 mmHg−1), indicating collateral artery growth. We here describe a new translational minimally invasive model of coronary collateral artery growth in pigs, according to a defined protocol of LCX-stenosis and subsequent occlusion, allowing preclinical evaluation of arteriogenic therapies.

Gene therapy for ischemic heart disease

Current pharmacologic therapy for ischemic heart disease suffers multiple limitations such as compliance issues and side effects of medications. Revascularization procedures often end with need for repeat procedures. Patients remain symptomatic despite maximal medical therapy. Gene therapy offers an attractive alternative to current pharmacologic therapies and may be beneficial in refractory disease. Gene therapy with isoforms of growth factors such as VEGF, FGF and HGF induces angiogenesis, decreases apoptosis and leads to protection in the ischemic heart. Stem cell therapy augmented with gene therapy used for myogenesis has proven to be beneficial in numerous animal models of myocardial ischemia. Gene therapy coding for antioxidants, eNOS, HSP, mitogen-activated protein kinase and numerous other anti apoptotic proteins have demonstrated significant cardioprotection in animal models. Clinical trials have demonstrated safety in humans apart from symptomatic and objective improvements in cardiac function. Current research efforts are aimed at refining various gene transfection techniques and regulation of gene expression in vivo in the heart and circulation to improve clinical outcomes in patients that suffer from ischemic heart disease. In this review article we will attempt to summarize the current state of both preclinical and clinical studies of gene therapy to combat myocardial ischemic disease. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Vascular endothelial growth factor (VEGF) response to dental trauma: a preliminary study in rats

BACKGROUND

Successful periodontal healing and pulpal revascularization after trauma may be age-related. After dental trauma, age-related impaired angiogenesis may play a role in the revascularization rate during the healing process.

OBJECTIVES

The aim of the present preliminary in vivo study was to detect the presence of vascular endothelial growth factor (VEGF) in venous and whole blood from the alveolar socket immediately post-tooth extraction.

MATERIALS AND METHODS

The study consisted of 16 Wistar rats divided into two groups: eight young (6 weeks) with incomplete root development and open apices, and eight adult (4 months) with complete root development. One first mandibular molar was extracted and whole blood from the alveolar socket collected immediately and at 5, 10 and 15 min post-extraction. Venous blood samples were collected immediately pre- and 24-h post-extraction. All samples were tested for VEGF.

RESULTS

Increased VEGF levels were found in the venous blood 24 h post-extraction, with a significant difference in the young rats (P < 0.05). The increased VEGF serum concentration in the young rats was significantly higher (12.2 +/- 4.6 pg ml(-1), median 12.1) than that in the adult rats (7.6 +/- 3.8 pg ml(-1), median 6.7) (P = 0.037). VEGF at the extraction site was not significantly different at 15 min post-extraction. At the extraction site, there was no significant difference of VEGF concentration between young and adult rats.

CONCLUSIONS

Young rats had higher post-extraction serum VEGF levels, which may contribute to the healing process after dental trauma.

Transgenic induction of vascular endothelial growth factor-C is strongly angiogenic in mouse embryos but leads to persistent lymphatic hyperplasia in adult tissues

Vascular endothelial growth factor-C (VEGF-C) is the quintessential lymphangiogenic growth factor that is required for the development of the lymphatic system and is capable of stimulating lymphangiogenesis in adults by activating its receptor, VEGFR-3. Although VEGF-C is a major candidate molecule for the development of prolymphangiogenic therapy for defective lymphatic vessels in lymphedema, the stability of lymph vessels generated by exogenous VEGF-C administration is not currently known. We studied VEGF-C-stimulated lymphangiogenesis in inducible transgenic mouse models in which growth factor expression can be spatially and temporally controlled without side effects, such as inflammation. VEGF-C induction in adult mouse skin for 1 to 2 weeks caused robust lymphatic hyperplasia that persisted for at least 6 months. VEGF-C induced lymphangiogenesis in numerous tissues and organs when expressed in the vascular endothelium in either neonates or adult mice. Very few or no effects were observed in either blood vessels or collecting lymph vessels. Additionally, VEGF-C stimulated lymphangiogenesis in embryos after the onset of lymphatic vessel development. Strikingly, a strong angiogenic effect was observed after VEGF-C induction in vascular endothelium at any point before embryonic day 16.5. Our results indicate that blood vessels can undergo VEGF-C-induced angiogenesis even after down-regulation of VEGFR-3 in embryos; however, transient VEGF-C expression in adults can induce long-lasting lymphatic hyperplasia with no obvious side effects on the blood vasculature.

Efficient and durable gene transfer to transplanted heart using adeno-associated virus 9 vector

BACKGROUND

In this investigation we studied the efficacy and durability of recombinant adeno-associated virus serotype 9 (rAAV9) vector-mediated gene transfer to the transplanted rat heart.

METHODS

A rAAV9-CMV-lacZ vector diluted in cold (4 degrees C) University of Wisconsin solution was used to perfuse the rat coronary vasculature for 20 minutes prior to syngeneic heterotopic transplantation. Perfusion experiments (six groups, n = 3/group) were performed without rAAV9 and at four separate doses ranging from 2 x 10(9) to 2 x 10(12) viral genomes/ml. The transplanted heart was recovered 10 days or 3 months after transplantation and expression of lacZ assessed by histology, enzyme-linked immunoassay and real-time reverse transcript-polymerase chain reaction (RT-PCR). In a final group (n = 3), rAAV9 was administered systemically to compare the cardiac transduction efficiency and viral distribution to other organs.

RESULTS

Transduction efficiency of perfused virus correlated with vector dose (p < 0.0001), with myocardial transduction ranging up to 71.74% at the highest dose. Cardiac expression of lacZ was equivalent at 10 days and 3 months. There was no evidence of viral gene transfer to other organs after heart transplantation.

CONCLUSIONS

Our findings demonstrate efficient and durable rAAV9-mediated gene transfer to the transplanted heart after ex vivo perfusion and suggest that AAV9 is a promising vector for cardiac gene therapy.

Ligation of Ameroid-Stenosed Coronary Artery Leads to Reproducible Myocardial Infarction—A Pilot Study in a Porcine Model

OBJECTIVE

Myocardial gene and cellular therapies have revived the use of porcine ischemic heart models. Commonly applied ameroid-obstruction produces inconsistent coronary stenoses and myocardial lesions, whereas abrupt coronary occlusion causes arrhythmias and sudden death. To produce a constant myocardial lesion after adaptation to ischemia, we surgically modified the ameroid-model by ligation. As a pilot study for further cell therapy research, the spontaneous myocardial response is described.

MATERIALS AND METHODS

Simultaneously with ameroid application, a loose loop of nonabsorbable thread was placed around the left circumflex artery (LCx) on 11 domestic piglets. Three weeks later, the loop was tightened. Coronary arteriograms with Rentrop collateral grading from 0 to 3, and 99mTc-single photon emission computerized tomography studies were performed 1 to 5 wk after ligation. At autopsy, the hearts were analyzed macroscopically, histologically, and with von Willebrandt factor-staining.

RESULTS

LCx-banding was well-tolerated in nine animals, of which angiographic occlusion was gained in eight. Postmortem analysis revealed a 5 to 10 cm(2) transmural or subendocardial lateral myocardial infarction in all except one heart. One week after occlusion, LCx showed well-developed collateral filling (Rentrop-grade 2.7 +/- 0.4), which remained unchanged at 5 wk. On single photon emission computerized tomography-scans, lateral wall perfusion increased spontaneously between 1 and 5 wk (P = 0.02), and von Willebrandt factor revealed clusters of neovascularization at the borders of infarct areas.

CONCLUSIONS

This new modification of ameroid model standardizes myocardial lesion, which might reduce animal number in preclinical studies, thus having ethical aspect. The remarked potential for spontaneous recovery in ischemic porcine myocardium should be considered in preclinical therapeutic studies.