Highly efficient ex vivo gene transfer to the transplanted heart by means of hypothermic perfusion with a low dose of adenoviral vector

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.

Prolonged cardiac allograft survival using iodine 131 after human sodium iodide symporter gene transfer in a rat model

BACKGROUND

Radioiodine is efficiently concentrated by tissues expressing the human sodium iodide symporter (hNIS).

OBJECTIVE

To analyze the effects of iodine 131 on acute cardiac allograft rejection after ex vivo hNIS gene transfer in a rat model of cardiac allotransplantation.

MATERIALS AND METHODS

Hearts from Brown Norway rats were perfused ex vivo either with UW (University of Wisconsin) solution (n = 9) or UW solution containing 1 x 10(9) pfu/mL of adenovirus 5 plus NIS (Ad-NIS) (n = 18). Donor hearts were transplanted heterotopically into the abdomen of Lewis rats, and recipients were treated on postoperative day 3 with either 15,000 microCi of (131)I or saline solution. The hearts were explanted when no longer beating, and were evaluated histologically for evidence of rejection and other changes.

RESULTS

Grafts perfused with the Ad-NIS vector survived significantly longer in recipients injected with (131)I (mean [SD], 11.3 [1.9] days) compared with control animals not treated with (131)I (5.7 [0.65] days) (P < .001). Treatment with (131)I did not prolong graft survival in recipients of hearts that were not perfused with Ad-NIS (5.5 [1.0] vs 5.3 [0.8] days). In Ad-NIS (131)I-treated transplants, the level of myocardial damage on day 6 after surgery, when control hearts were rejected, was significantly lower (60.8 [28.0] vs 99.7 [0.8]; P < .05).

CONCLUSION

Our findings indicate that (131)I, after NIS gene transfer, can effectively prolong cardiac allograft survival. To our knowledge, this is the first report of the use of NIS-targeted (131)I therapy in cardiac transplantation. Further studies are required to determine the mechanism of this effect and its potential for clinical application.

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.

Sodium iodide symporter (hNIS) permits molecular imaging of gene transduction in cardiac transplantation

BACKGROUND

We evaluated the feasibility of noninvasive micro-single photon emission computed tomography (SPECT)/computed tomography (CT) imaging and quantification of cardiac gene expression after sodium iodide symporter (hNIS) gene transfer in cardiac transplantation.

METHODS

Donor rat hearts were perfused ex vivo with adenovirus expressing hNIS (Ad-hNIS), Ad-Null, or University of Wisconsin (UW) solution prior to heterotopic transplantation into syngeneic recipients. In the first group of recipients, imaging of the transplanted hearts with micro-SPECT/CT on day 5 was followed by immediate explant of the organs for ex vivo analyses. Radioactivity counts in the explanted hearts were obtained ex vivo and expressed as a percentage of the injected dose per gram of tissue (%ID/g). Intensities of the SPECT images of the transplanted hearts were quantified and converted to radioactive counts using a standard equation. The second group of recipients was imaged sequentially after injection of I on days 2 to 14 after transplantation.

RESULTS

Higher ex vivo radioiodine counts were noted in the hearts perfused with Ad-hNIS (1.04+/-0.2) compared to either the UW group (0.31+/-0.11, P<0.001) or the Ad-Null group (0.32+/-0.08, P<0.001). Image intensity in the Ad-NIS group (0.9+/-0.2) was also significantly higher than in the UW group (0.4+/-.03, P=0.003) or the Ad-Null group (0.5+/-0.1, P<0.05). Sequential imaging of Ad-NIS-perfused hearts between postoperative days 2 and 14 revealed peak image intensity at day 5. Overall, image intensities correlated with ex vivo counts of radioactivity (rho=0.74, P<0.05).

CONCLUSIONS

These data demonstrate that hNIS gene transfer permits sequential real-time detection and quantification of reporter gene expression in the transplanted heart with micro-SPECT/CT imaging.

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.

Recombinant adeno-associated virus vector for gene transfer to the transplanted rat heart

Efficient durable viral vector transduction of the transplanted heart remains elusive. This study assesses the potential of recombinant adeno-associated virus (rAAV) mediated gene delivery to the transplanted rat heart. rAAV serotype 1, 2 and 5 vectors encoding the green fluorescent protein (GFP) gene (1 x 10(11) viral particles/ml) were diluted in cold University of Wisconsin solution and circulated through the coronary vasculature of the donor organs for 30 min before syngeneic rat heterotopic heart transplantation was performed. Study 1: animals (n = 5 each serotype) were killed at 21 days post-transplant to evaluate the efficiency of GFP transduction using RT-PCR and expression by fluorescence microscopy. Study 2: using rAAV-1, animals (n = 5 each group) were killed at 7, 21 and 84 days to evaluate the durability of GFP expression. The maximum cardiac GFP expression at 21 days was observed in rAAV-1. GFP expression by rAAV-1 was detectable at 7 days, improved at 21 days, and was still evident at 84 days. This study demonstrates cardiac rAAV gene transduction with a cold perfusion preservation system of the donor heart. These data show that AAV-1 is superior to AAV-2 and AAV-5 for this purpose and that durable expression is achievable.

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

BACKGROUND

To facilitate the application of adenoviral gene therapy in clinical heart transplantation, we developed an ex vivo hypothermic recirculatory adenoviral gene transfer method to the transplanted pig heart.

METHODS

Experimental animals were assigned into three groups; controls, 1x10(8) plaque-forming units (pfu)/ml group and 1x10(9) pfu/ml group. During the 30 min gene transfer perfusion, 200 ml of University of Wisconsin solution containing the adenoviral vector was recirculated through the coronary vessels. The myocardial temperature was maintained below 4 degrees C and the perfusion pressure was adjusted at 50 mmHg.

RESULTS

Cardiac myocyte transduction efficiencies in the 1x10(8) pfu/ml group were 0.04% and 0.07%, whereas transduction efficiencies in the 1x10(9) pfu/ml group were widely distributed from 0.45% to 22.62%. The gene transduction efficiency increased with the virus titer. Additionally, no difference in the transduction efficiency was observed between different segments of the left ventricle. The current gene transfer method at 1x10(9) pfu/ml of adenovirus titer enabled homogeneous gene transduction into the transplanted pig heart up to a maximum of 22.62%.

CONCLUSIONS

This model can be applied to a large isolated heart and will greatly facilitate the investigation of gene therapy in large animal models of heart transplantation.

Gene transfer of RANTES and MCP-1 chemokine antagonists prolongs cardiac allograft survival

Vascularized organ allografts are rapidly destroyed by host immune cells that are recruited along chemokine gradients. Among chemokines, Regulated on Activation, Normal T-cell Expressed and Secreted (RANTES) CC chemokine ligand (CCL5) and monocyte chemoattractant protein (MCP)-1 (CCL2) are upregulated in rejecting cardiac allografts. To antagonize these chemokines, we constructed adenoviral vectors expressing NH(2)-terminal deletion (8ND) mutants of the respective genes. Using the F344-to-LEW rat model, intragraft gene transfer of chemokine analogs prolonged cardiac allograft survival from 10.1+/-0.7 and 10.4+/-0.7 days using non-coding adenovirus and vehicle alone, respectively, to 17.0+/-0.7 days for 8ND-RANTES (P<0.001) and 14.2+/-0.8 days for 8ND-MCP-1 (P<0.01). 8ND-RANTES reduced graft infiltration by monocytes/macrophages, cluster of differentiation (CD) 8alpha(+) and T-cell receptor alphabeta(+) cells, while 8ND-MCP-1 reduced monocytes/macrophages. In mixed leukocyte reactions in vitro, proliferation of host lymphocytes from regional lymph nodes in response to donor splenocytes was unaffected by 8ND-RANTES gene transfer. Using a two-gene approach, the contribution of 8ND-MCP-1 was negligible, consistent with available evidence that 8ND-RANTES inhibits both RANTES and MCP-1 activities. 8ND-RANTES gene transfer and a short course of low-dose cyclosporine A synergistically prolonged graft survival to 37.8+/-5.5 vs 15.4+/-0.5 days with cyclosporine alone (P<0.001). These results suggest a role for anti-chemokine gene therapy as an adjuvant therapy in heart transplantation.

Adenovirus type 5 intrinsic adsorption rates measured by surface plasmon resonance

Intrinsic adsorption rates of whole adenovirus type 5 (Ad5) onto a diethylaminoethyl (DEAE) anion exchange surface are measured for the first time by surface plasmon resonance (SPR). Fitting SPR sensorgrams to a two-compartment mass transport reaction model distinguishes intrinsic adsorption rates from slow diffusive Ad5 mass transport. Ad5 is a widely used viral vector for gene therapy that binds electrostatically to surfaces of cells and synthetics such as membranes, chromatographic resins, and glass. Increasing NaCl concentration from 4.8 to 14.4mM shifts binding of whole Ad5 from diffusion control to a regime where both sorption and diffusion affect binding. Intrinsic adsorption rates for Ad5-DEAE interaction are 16 times faster than intrinsic adsorption rates for Ad5 fiber knob interacting with soluble extracellular domain of coxsackievirus adenovirus receptors (s-CAR).

Multigene adenoviral therapy for the attenuation of ischemia-reperfusion injury after preservation for cardiac transplantation

OBJECTIVE

The protective effect of adenovirus-mediated ex vivo multigene transfer with superoxide dismutase, a free radical scavenger, and nitric oxide, a vasodilator with anti-inflammatory properties, was examined in the rat heart during experimental ischemia-reperfusion mimicking preservation for cardiac transplantation.

METHODS

Donor rat hearts (n = 6 per group) were perfused with solution containing adenoviral vector carrying genes for beta-galactosidase (group A), endothelial nitric oxide synthase (group B), manganese superoxide dismutase (group C), or both endothelial nitric oxide synthase and manganese superoxide dismutase (group D). Hearts were then implanted heterotopically into the abdomens of recipient rats. Four days later, transplanted hearts were collected, connected to a Langendorff perfusion apparatus, and subjected to 6 hours of ischemia followed by 1 hour of reperfusion. Cardiac function was evaluated with an intraventricular balloon at the beginning of Langendorff perfusion and after ischemia-reperfusion.

RESULTS

Effective gene transfection was confirmed with X-gal staining in group A hearts. Positive immunoreactivity for endothelial nitric oxide synthase, manganese superoxide dismutase, or both was present predominantly in cardiomyocytes in group B, C, and D hearts. Percentage recovery of preischemic left ventricular developed pressure was 62.1% +/- 7.36% in group A; recoveries were increased to 79.6% +/- 6.4%, 86.8% +/- 9.1%, and 79.4% +/- 6.2% in groups B, C, and D, respectively.

CONCLUSION

These results indicate that adenoviral gene transfer of manganese superoxide dismutase and endothelial nitric oxide synthase can attenuate myocardial ischemia-reperfusion injury, with the former providing the most significant protection. Combined overexpression of manganese superoxide dismutase and endothelial nitric oxide synthase did not enhance myocardial recovery any further.

Adenovirus-mediated gene transfer to the transplanted piglet heart after intracoronary injection

BACKGROUND

The advent of cardiac gene therapy in clinical practice requires a more efficient and safer myocardial gene delivery in large animals. A new approach to adenovirus-mediated intracoronary gene transfer in the piglet, using a heterotopic heart transplantation model, was designed to maximize the duration of contact between the vector and the heart in noncoronary flow conditions.

METHODS

Recombinant adenoviruses harboring a nucleus-localized beta-galactosidase gene under the control of a viral promoter were injected into the coronary vessels of the harvested hearts at a dose ranging from 10(10) to 2 x 10(11) pfu. The graft was maintained for 75 min in saline solution and then implanted in the abdomen of recipients. Gene transfer to allografts was evaluated 4 days after grafting by immunohistochemical and enzymatic analysis of beta-galactosidase expression.

RESULTS

Transgene expression was detected in all cardiac areas and up to 64, 44, 32, and 15% of positive nuclei were estimated in the left ventricle wall in four animals out of eleven. In the remaining animals, transgene expression was focally distributed, mainly in the left ventricle wall. PCR analysis revealed the presence of adenoviral sequences, albeit minimal, in exposed organs such as the liver and lung.

CONCLUSIONS

This procedure demonstrated that direct intracoronary gene transfer can be achieved using an ex vivo gene transfer strategy.

Conditions of vector delivery improve efficiency of adenoviral-mediated gene transfer to the transplanted heart

OBJECTIVES

Conditions for ex vivo gene transfer to the transplanted heart were studied in a model of syngeneic abdominal heterotopic heart transplantation in the rat. Various methods of adenoviral-mediated gene transfer to the transplanted heart were compared.

METHODS

In the first experiment, a dose response study, an adenoviral vector encoding the beta-galactosidase gene was infused into the donor heart with the pulmonary artery open and flushed out prior to performing the transplant. In the second experiment, the effects of clamping the pulmonary artery during vector infusion and not flushing out the viral solution, resulting in vector dwell during the warm ischemia, were examined.

RESULTS

In the first experiment, gene transfer was relatively inefficient; however, transgene expression improved with increases in the vector dose (range, 1x10(7)-1x10(9)). The efficiency of gene transfer was significantly greater when the conditions of the second experiment were applied. In all models studied, cardiomyocytes and not vascular endothelial cells were the predominant cell type transduced.

CONCLUSIONS

This study indicates that the conditions of adenoviral vector delivery are critical for optimizing gene transfer in the transplant setting. In addition, intravascular administration of adenoviral vector to the donor heart results predominantly in cardiomyocyte transgene expression.