Ex vivo hypothermic recirculatory adenoviral gene transfer to the transplanted pig heart

Gene therapy during ex situ heart perfusion: a new frontier in cardiac regenerative medicine?

Ex situ organ preservation by machine perfusion can improve preservation of organs for transplantation. Furthermore, machine perfusion opens up the possibilities for selective immunomodulation, creation of tolerance to ischemia-reperfusion injury and/or correction of a pathogenic genetic defect. The application of gene modifying therapies to treat heart diseases caused by pathogenic mutations during ex situ heart perfusion seems promising, especially given the limitations related to delivery of vectors that were encountered during clinical trials using in vivo cardiac gene therapy. By isolating the heart in a metabolically and immunologically favorable environment and preventing off-target effects and dilution, it is possible to directly control factors that enhance the success rate of cardiac gene therapy. A literature search of PubMed and Embase databases was performed to identify all relevant studies regarding gene therapy during ex situ heart perfusion, aiming to highlight important lessons learned and discuss future clinical prospects of this promising approach.

Mitochondrial Reprogramming—What Is the Benefit of Hypothermic Oxygenated Perfusion in Liver Transplantation?

Although machine perfusion is a hot topic today, we are just at the beginning of understanding the underlying mechanisms of protection. Recently, the first randomized controlled trial reported a significant reduction of ischemic cholangiopathies after transplantation of livers donated after circulatory death, provided the grafts were treated with an endischemic hypothermic oxygenated perfusion (HOPE). This approach has been known for more than fifty years, and was initially mainly used to preserve kidneys before implantation. Today there is an increasing interest in this and other dynamic preservation technologies and various centers have tested different approaches in clinical trials and cohort studies. Based on this, there is a need for uniform perfusion settings (perfusion route and duration), and the development of general guidelines regarding the duration of cold storage in context of the overall donor risk is also required to better compare various trial results. This article will highlight how cold perfusion protects organs mechanistically, and target such technical challenges with the perfusion setting. Finally, the options for viability testing during hypothermic perfusion will be discussed.

Locoregional intravascular viral therapy of cancer: precision guidance for Paris's arrow?

Viral therapy of cancer includes strategies such as viral transduction of tumour cells with 'suicide genes', using viral infection to trigger immune-mediated tumour cell death and using oncolytic viruses for their direct anti-tumour action. However, problems still remain in terms of adequate viral delivery to tumours. A role is also emerging for single-organ isolation and perfusion. Having begun with the advent of isolated limb perfusion for extremity malignancy, experimental systems have been developed for the perfusion of other organs, particularly the liver, kidneys and lungs. These are beginning to be adopted into clinical treatment pathways. The combination of these two modalities is potentially significant. Locoregional perfusion increases the exposure of tumour cells to viral agents. In addition, the avoidance of systemic elimination through the immune and reticulo-endothelial systems should provide a mechanism for increased transduction/infection of target cells. The translation of laboratory research to clinical practice would occur within the context of perfusion programmes, which are already established in the clinic. Many of these programmes include the use of vasoactive cytokines such as tumour necrosis factor-alpha, which may have an effect on viral uptake. Evidence of activation of specific anti-tumour immunological responses by intratumoural and other existing methods of viral administration raises the intriguing possibility of a locoregional therapy, with the ability to affect distant sites of disease. In this review, we examined the state of the literature in this area and summarized current findings before indicating likely areas of continuing interest.

Designing heart performance by gene transfer

The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.

Percutaneous transendocardial delivery of self-complementary adeno-associated virus 6 achieves global cardiac gene transfer in canines

Achieving efficient cardiac gene transfer in a large animal model has proven to be technically challenging. Previous strategies have used cardiopulmonary bypass or dual catheterization with the aid of vasodilators to deliver vectors, such as adenovirus, adeno-associated virus (AAV), or plasmid DNA. Although single-stranded AAV (ssAAV) vectors have shown the greatest promise, they suffer from delayed expression, which might be circumvented using self-complementary vectors. We sought to optimize cardiac gene transfer using a percutaneous transendocardial injection catheter to deliver adeno-associated viral vectors to the canine myocardium. Four vectors were evaluated--ssAAV9, self-complementary AAV9 (scAAV9), scAAV8, scAAV6--so that comparison could be made between single-stranded and self-complementary vectors as well as among serotypes 9, 8, and 6. We demonstrate that scAAV is superior to ssAAV and that AAV 6 is superior to the other serotypes evaluated. Biodistribution studies revealed that vector genome copies were 15-4,000 times more abundant in the heart than in any other organ for scAAV6. Percutaneous transendocardial injection of scAAV6 is a safe, effective method to achieve efficient cardiac gene transfer.

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.

Recombinant adenoviral gene transfer does not affect cardiac allograft vasculopathy

BACKGROUND

Adenovirus serotype 5 has remained the pre-eminent vector in pre-clinical gene therapy applications in cardiac transplantation. Concerns over the potential effects of adenoviral vectors on the later development of cardiac allograft vasculopathy (CAV) are addressed in this study.

METHODS

Hearts (n = 22) harvested from Brown Norway rats were perfused ex vivo with either University of Wisconsin (UW) solution with no virus, Ad-CMV-LacZ or Ad-CMV-Null. Donor hearts were transplanted heterotopically into the abdomen of Lewis rats. All recipients received cyclosporine for the duration of the experiment. Transplanted hearts were recovered for analysis at 120 days. Sections of the heart were stained with elastic-van Gieson stain for morphometric analysis of the vessels to ascertain the degree of vascular luminal occlusion. Hematoxylin-eosin staining facilitated diagnosis of chronic rejection.

RESULTS

Seventy-seven percent of transplanted hearts showed signs of chronic rejection with no difference in the proportion of animals between groups (p = 0.797). No difference was noted in the degree of vascular luminal occlusion between the Ad-Null (0.57 +/- 0.22), Ad-LacZ (0.62 +/- 0.19) and UW (0.47 +/- 0.29) groups (p = 0.653).

CONCLUSIONS

Vascularized cardiac allografts transplanted from Brown Norway to Lewis rats demonstrated cardiac allograft vasculopathy CAV at 120 days. Adenoviral perfusion of the donor heart ex vivo did not affect the development of CAV.

Non-invasive radioiodine imaging for accurate quantitation of NIS reporter gene expression in transplanted hearts

OBJECTIVE

We studied the concordance of transgene expression in the transplanted heart using bicistronic adenoviral vector coding for a transgene of interest (human carcinoembryonic antigen: hCEA - beta human chorionic gonadotropin: betahCG) and for a marker imaging transgene (human sodium iodide symporter: hNIS).

METHODS

Inbred Lewis rats were used for syngeneic heterotopic cardiac transplantation. Donor rat hearts were perfused ex vivo for 30 min prior to transplantation with University of Wisconsin (UW) solution (n=3), with 10(9) pfu/ml of adenovirus expressing hNIS (Ad-NIS; n=6), hNIS-hCEA (Ad-NIS-CEA; n=6) and hNIS-betahCG (Ad-NIS-CG; n=6). On postoperative day (POD) 5, 10, 15 all animals underwent micro-single photon emission computed tomography/computed tomography (SPECT/CT) imaging of the donor hearts after tail vein injection of 1000 microCi (123)I and blood sample collection for hCEA and betahCG quantification.

RESULTS

Significantly higher image intensity was noted in the hearts perfused with Ad-NIS (1.1+/-0.2; 0.9+/-0.07), Ad-NIS-CEA (1.2+/-0.3; 0.9+/-0.1) and Ad-NIS-CG (1.1+/-0.1; 0.9+/-0.1) compared to UW group (0.44+/-0.03; 0.47+/-0.06) on POD 5 and 10 (p<0.05). Serum levels of hCEA and betahCG increased in animals showing high cardiac (123)I uptake, but not in those with lower uptake. Above this threshold, image intensities correlated well with serum levels of hCEA and betahCG (R(2)=0.99 and R(2)=0.96, respectively).

CONCLUSIONS

These data demonstrate that hNIS is an excellent reporter gene for the transplanted heart. The expression level of hNIS can be accurately and non-invasively monitored by serial radioisotopic SPECT imaging. High concordance has been demonstrated between imaging and soluble marker peptides at the maximum transgene expression on POD 5.