Successful in vivo and ex vivo transfection of pulmonary artery segments in lung isografts

Intratracheal adenovirus-mediated gene transfer is optimal in experimental lung transplantation

OBJECTIVE

Gene transfer to experimental lung grafts has been shown to reduce ischemia-reperfusion injury and acute rejection. The optimal delivery route should produce high lung expression with no inflammation and minimal systemic expression. The goal of this study was to determine the optimal gene transfer route for use in experimental lung transplantation.

METHODS

F344 rats were injected with 2.9 x 10(10) plaque-forming units of adenovirus vector encoding beta-galactosidase through intratracheal, intravenous, intraperitoneal, or intramuscular delivery routes and killed 48 hours later. Gene expression was measured by means of enzyme-linked immunosorbent assay.

RESULTS

Intratracheal delivery produces significantly greater gene expression in the lung (75,350 +/- 47,288 pg/100 microg of protein, P <.001 vs intravenous, intraperitoneal, and intramuscular routes) and minimal systemic expression (nonsignificant in serum, kidney, liver, spleen, and muscle vs that seen in control animals, P =.016 for heart). Immunohistochemistry staining showed beta-galactosidase expression in the bronchial epithelium of lungs transfected through the intratracheal route with mild inflammation.

CONCLUSIONS

Intratracheal gene transfer provides significant expression in the lung with mild to no inflammation and minimal systemic expression. This delivery strategy has tremendous potential in experimental lung transplant models to reduce ischemia-reperfusion injury and acute allograft rejection and should be investigated further.

Toxicity of cationic liposome-DNA complex in lung isografts

BACKGROUND

Cationic lipids have been successfully employed as vectors for gene transfer in lung grafts, yet those lipid vectors have potential toxicity. Furthermore, the optimal concentration of cationic lipids for gene transfection to lung grafts has not been determined. We evaluated liposome concentration/toxicity relationships in an in vivo rat lung transplantation model.

METHODS

Left lungs were harvested and infused via the pulmonary artery with chloramphenicol acetyl-transferase (CAT)-DNA/lipid 67 (cationic lipid)/dioleoylphosphatidylethanolamine complex (4:1:2 in a final concentration ratio). Donor lungs were allocated into six groups according to lipid 67 concentration: group 1, 0 microM (control); group 2, 10 microM; group 3, 50 microM; group 4, 100 microM; group 5, 250 microM; group 6, 500 microM. Forty-eight hours after orthotopic transplantation, the recipient contralateral right main pulmonary artery and bronchus were ligated. The graft was ventilated with 100% oxygen for 5 min. Arterial blood gas analysis (PaO2, PaCO2), peak airway pressure (PAP), and CAT activity of the grafts were measured.

RESULTS

Recipient survival, and PaO2, PAP, and CAT levels correlated with the lipid-DNA complex concentration. The grafts in groups 4-6 were more injured as evidenced by decreased PaO2 and increased PAP levels in comparison to the control group. CAT level was significantly lower in group 2 than in groups 3-6.

CONCLUSIONS

The pulmonary toxicity of cationic lipid is dose-dependent. The balance between lung graft function and transgene expression is optimal at a lipid 67 concentration of 50 microM.

Transtracheal gene transfection of donor lungs prior to organ procurement increases transgene levels at reperfusion and following transplantation

BACKGROUND

Gene therapy's potential to modify donor organs to better withstand the process of transplantation has yet to be realized. To determine whether gene transfection is feasible to treat the early post-transplant injury of ischemia-reperfusion, we compared transfection of lungs in the donor prior to organ procurement with transfection of harvested ex vivo lungs in a rat single lung transplant model.

METHODS

Lewis rats (donor transfection [DT]; n = 4) underwent transtracheal adenoviral-mediated transfection with 10(9) plaque forming unit of the beta-galactosidase reporter gene. Donor lungs were harvested following 6 hours of in vivo post-transfection ventilation, and then preserved for 6 hours at 4 degrees C prior to left single-lung transplantation. Ex vivo transfection was performed following organ retrieval; lungs were then preserved at 4 degrees C for 6 hours (EVT6h; n = 6) and 12 hours (EVT12h; n = 6) prior to transplantation. Lung transgene expression was measured by chemiluminescence at reperfusion, and at 2 hours following lung transplantation.

RESULTS

Donor transfection lungs showed significantly higher levels of transgene expression as compared with EVT lungs at the time of reperfusion (DT = 3,408+/-1,301 relative light units/mg protein; EVT6h = 218+/-7; EVT12h = 213+/-26; p < 0.02) and at 2 hours after lung transplantation (DT = 2900+/-870; EVT6h = 62+/-27; EVT12h = 123+/-21; p < 0.005). Transgene expression measured in the heart, liver, kidney, and serum from DT rats demonstrated virtually no evidence of collateral transfection at 12 hours post-transfection (all <5.0).

CONCLUSIONS

Gene transfection of donor lungs produces significantly higher levels of transgene expression in lungs at the critical time of reperfusion and in the early period following lung transplantation as compared to ex vivo transfection of cold preserved lungs. Transtracheal donor-lung transfection does not appear to result in collateral transfection of other transplantable organs. Local adenoviral-mediated transfection of the lungs is possible in the multiorgan donor prior to organ procurement and may provide the optimal strategy for gene therapeutic manipulations to address post-transplant ischemia-reperfusion injury.

Transfection of pulmonary artery segments in lung isografts during storage

BACKGROUND

Proximal pulmonary artery segment (PPAS) endothelial transfection of lung grafts may be useful in ameliorating ischemia-reperfusion injury and rejection and may provide beneficial downstream effects on the whole lung graft. Transfection immediately after lung transplantation may be efficacious in ameliorating allograft dysfunction after transplantation.

METHODS

In F344 rats, the PPAS was isolated and injected with 0.03 mL of GL-67/DOPE-chloramphenicol acetyl transferase (CAT) plasmid DNA. The PPASs were exposed for 60 minutes at several temperatures. The lung grafts were stored in saline solution (group 1, n = 24) or LPDG solution (group 2, n = 27) for 12 or 24 hours at 4 degrees to 37 degrees C. In group 3 (n = 42), PPASs were stored in endothelial cell culture medium and incubated at 10 degrees or 37 degrees C in a carbon dioxide incubator for 3 to 72 hours. Group 4 (n = 18) served as transplanted controls; after 3 to 24 hours' preservation at 4 degrees C in LPDG solution, lung grafts were transplanted. Transgene expression of PPASs was assessed with two CAT activity assays, thin-layer chromatography enzyme-linked immunosorbent assay and immediately after the preservation period (groups 1 to 3) or 24 hours after transplantation (group 4).

RESULTS

In group 1, transgene expression did not appear. In groups 2 and 3, transgene expression was apparent after any storage duration at 37 degrees C. Transgene expression increased successively with longer storage periods. In group 4, transgene expression was detected after any storage duration. The enzyme-linked immunosorbent assay is able to quantify the expression of CAT activity, but thin-layer chromatography is more sensitive.

CONCLUSIONS

Transgene expression did not occur during conventional cold storage. Transgene expression in rat PPASs during storage is possible with warm storage (37 degrees C) and appropriate storage solution.

Ex vivo transfection of pulmonary artery segments in lung isografts

BACKGROUND

Gene transfer to lung grafts may be useful in ameliorating ischemia-reperfusion injury and rejection. Proximal pulmonary artery endothelial transfection may provide beneficial downstream effects on the whole lung graft. We have already demonstrated the feasibility of in vivo and ex vivo transfection in proximal pulmonary artery segments of rat lung grafts. The aim of this study was to determine the optimal conditions for and duration of transfection.

METHODS

Orthotopic left lung transplantation was performed in F344 rats after donor lung proximal pulmonary artery segments were isolated and injected with lipid 67/DOPE-chloramphenicol acetyl transferase (CAT) complementary deoxyribonucleic acid construct. Effect of exposure time was studied by exposing donor pulmonary artery segments to the construct for 0, 30, and 60 minutes prior to transplantation. In another series of experiments, pulmonary artery segments were exposed to the construct for 60 minutes prior to transplantation. Onset and duration of gene expression were determined after sacrificing animals at 3, 6, 12, and 24 hours and 3 days as well as 1 week, 2, 4, and 8 weeks after transplantation. Effect of exposure temperature was studied by exposing pulmonary artery segments to the construct for 60 minutes at 4 degrees, 10 degrees, and 23 degrees C. These recipients were sacrificed on postoperative day 3. Effect of exposure pressure was studied by using two volumes of the construct (0.01 and 0.03 mL). These recipients were sacrificed on postoperative day 3. Transgene expression was assessed by chloramphenicol acetyl transferase activity assay.

RESULTS

Transgene expression was similar after 30- and 60-minute exposure. Transgene expression was evident within 3 to 6 hours after operation and persisted at 8 weeks after operation. Expression was detected at all temperatures and was equivalent at both exposure pressures.

CONCLUSIONS

Gene transfection into graft pulmonary artery segments is possible under a range of conditions applicable to clinical lung transplantation.

Gene transfer of heat shock protein 70 protects lung grafts from ischemia-reperfusion injury

BACKGROUND

We recently demonstrated that heat stress induction of heat shock protein 70 (HSP70) in donor animals before harvest decreases posttransplant ischemia-reperfusion injury in preserved rat lung isografts. The purpose of this study was to investigate the feasibility of HSP70 gene transfection into rat lung isografts using an adenoviral vector, and to study the effects of gene expression on subsequent ischemia-reperfusion injury.

METHODS

In preliminary studies to determine the optimal titer, animals were injected with various titers of adenovirus-HSP70 (saline, 5 x 10(9), 1 x 10(10), and 2 x 10(10) plaque forming units [pfu]) and sacrificed 5 days after injection. To determine the optimal exposure time, animals were sacrificed at different times (0, 6, 24, and 72 hours) after intravenous injection of adenovirus-HSP70. In a subsequent series of transplant experiments, donors were allocated to three groups according to transfection strategy. Group 1 (n = 8) donors received 5 x 10(9) pfu adenovirus-HSP70 intravenously, group 2 (n = 7) donors received 5 x 10(9) pfu adenovirus-beta-galactosidase (as a virus control), and group 3 (n = 7) donors received saline and served as a negative control. Twenty-four hours after treatment all grafts were harvested and stored for 18 hours before orthotopic left lung transplantation. Twenty-four hours after implantation animals were sacrificed for assessment. The expression of HSP70 was assessed by Western blot analysis.

RESULTS

In preliminary studies, HSP70 was detectable even at low titers (5 x 10(9) pfu) of adenovirus-HSP70, and was detectable at low levels as early as 6 hours after intravenous administration. Heat shock protein 70 expression was maximal at 24 hours. In transplant experiments, Western blot analysis showed that overexpression of HSP70 occurred in the HSP70-transfected lungs. The mean arterial oxygenation 24 hours after reperfusion in group 1 was superior in comparison with other groups (p < 0.05). Wet to dry weight ratio (p < 0.05) and myeloperoxidase activity (p < 0.05) were also significantly less in group 1 grafts compared with the other groups.

CONCLUSIONS

This study demonstrates that in vivo, donor adenovirus-mediated gene transfer of HSP70 decreases subsequent ischemia-reperfusion injury in rat lung isografts.

Ex vivo transfection of transforming growth factor-beta1 gene to pulmonary artery segments in lung grafts

OBJECTIVE

Proximal pulmonary artery segment transfection may provide beneficial downstream effects on the whole-lung graft. In this study, transforming growth factor-beta1 was transfected to proximal pulmonary artery segments, and the efficacy of transforming growth factor-beta1 transfection was examined in ischemia-reperfusion injury and acute rejection models of rat lung transplantation.

METHODS

In the ischemia-reperfusion injury model, orthotopic left lung transplantation was performed in F344 rats. In group I, the PPAS was isolated and injected with saline solution. In 2 other groups, lipid67:DOPE:sense (group II) or antisense transforming growth factor-beta1pDNA construct (group III) was injected instead of saline solution. After cold preservation at 4 degrees C for 18 hours, lung grafts were implanted. Graft function was assessed 24 hours later. In the acute rejection model, donor lung grafts were harvested. Proximal pulmonary artery segments were injected with saline solution (group I) or sense (group II) or antisense lipid gene construct (group III) and then implanted. Graft function was assessed on postoperative day 5.

RESULTS

In the ischemia-reperfusion injury study, there were no significant differences in oxygenation, wet-to-dry weight ratios, graft myeloperoxidase activity, or transforming growth factor-beta1 levels in platelet-poor serum or proximal pulmonary artery segment homogenates. In the acute rejection study, oxygenation was significantly improved in group II receiving transforming growth factor-beta1 (group II vs I and III, 136.0 +/- 32.5 vs 54.0 +/- 9.6 mm Hg and 53.8 +/- 14.8 mm Hg; P =.016 and.016). There were no significant pathologic differences. Transforming growth factor-beta1 concentrations from proximal pulmonary artery segment homogenates in group II were significantly higher compared with controls.

CONCLUSIONS

Ex vivo transfection of transforming growth factor-beta1 to proximal pulmonary artery segments did not affect reperfusion injury of lung isografts. In acute rejection, however, ex vivo transfection of transforming growth factor-beta 1 to proximal pulmonary artery segments improved allograft function. This suggests that transfection to proximal pulmonary artery segments exerts beneficial downstream effects on the whole-lung allograft.