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

Gene Therapy: Will the Promise of Optimizing Lung Allografts Become Reality?

Lung transplantation is the definitive therapy for patients living with end-stage lung disease. Despite significant progress made in the field, graft survival remains the lowest of all solid organ transplants. Additionally, the lung has among the lowest of organ utilization rates-among eligible donors, only 22% of lungs from multi-organ donors were transplanted in 2019. Novel strategies are needed to rehabilitate marginal organs and improve graft survival. Gene therapy is one promising strategy in optimizing donor allografts. Over-expression or inhibition of specific genes can be achieved to target various pathways of graft injury, including ischemic-reperfusion injuries, humoral or cellular rejection, and chronic lung allograft dysfunction. Experiments in animal models have historically utilized adenovirus-based vectors and the majority of literature in lung transplantation has focused on overexpression of IL-10. Although several strategies were shown to prevent rejection and prolong graft survival in preclinical models, none have led to clinical translation. The past decade has seen a renaissance in the field of gene therapy and two AAV-based in vivo gene therapies are now FDA-approved for clinical use. Concurrently, normothermic ex vivo machine perfusion technology has emerged as an alternative to traditional static cold storage. This preservation method keeps organs physiologically active during storage and thus potentially offers a platform for gene therapy. This review will explore the advantages and disadvantages of various gene therapy modalities, review various candidate genes implicated in various stages of allograft injury and summarize the recent efforts in optimizing donor lungs using gene therapy.

Efficient intratracheal delivery of airway epithelial cells in mice and pigs

Cellular therapy via direct intratracheal delivery has gained interest as a novel therapeutic strategy for treating various pulmonary diseases including cystic fibrosis lung disease. However, concerns such as insufficient cell engraftment in lungs and lack of large animal model data remain to be resolved. This study aimed to establish a simple method for evaluating cell retention in lungs and to develop reproducible approaches for efficient cell delivery into mouse and pig lungs. Human lung epithelial cells including normal human bronchial/tracheal epithelial (NHBE) cells and human lung epithelial cell line A549 were infected with pSicoR-green fluorescent protein (GFP) lentivirus. GFP-labeled NHBE cells were delivered via a modified intratracheal cell instillation method into the lungs of C57BL/6J mice. Two days following cell delivery, GFP ELISA-based assay revealed a substantial cell-retention efficiency (10.48 ± 2.86%, n = 7) in mouse lungs preinjured with 2% polidocanol. When GFP-labeled A549 cells were transplanted into Yorkshire pig lungs with a tracheal intubation fiberscope, a robust initial cell attachment (22.32% efficiency) was observed at 24 h. In addition, a lentiviral vector was developed to induce the overexpression and apical localization of cystic fibrosis transmembrane conductance regulator (CFTR)-GFP fusion proteins in NHBE cells as a means of ex vivo CFTR gene transfer in nonprogenitor (relatively differentiated) lung epithelial cells. These results have demonstrated the convenience and efficiency of direct delivery of exogenous epithelial cells to lungs in mouse and pig models and provided important background for future preclinical evaluation of intratracheal cell transplantation to treat lung diseases.

Searching for NF-kappaB-based treatments of ischemia reperfusion injury

When a tissue becomes ischemic, a host of changes occur at the cellular level that lead to a shift in transcriptional activity of many inflammatory and cytoprotective compounds, a process which is extensively controlled through a family of transcription factors known as nuclear factor kappa-B (NF-kappaB). This shift in activity paradoxically results in both a cytoprotective effect at the cellular level and upon reperfusion, a generally destructive inflammatory response, a phenomenon referred to as ischemia reperfusion (IR) injury. To date, a number of methods of modifying the activity of NF-kappaB through either physiologic or pharmacologic manipulation have been developed and studied in animal models of IR injury and in some cases in human clinical trials. Nearly every method of NF-kappaB antagonism has demonstrated a discrete protective effect allowing investigators to reduce myocardial infarct sizes by 60% and cerebral infarct sizes by 57% relative to untreated control animals. The problem of IR injury is all too common and represents a discrete threat not only to the tissues directly involved in the ischemic event, but also to distal sites as well as is seen in the evolution of acute respiratory distress and severe inflammatory response syndromes. In the course of this review, the nature of NF-kappaB and its involvement in IR injury is examined along with the efficacy of the various NF-kappaB-based investigational treatment developed to date.

Update on donor assessment, resuscitation, and acceptance criteria, including novel techniques--non-heart-beating donor lung retrieval and ex vivo donor lung perfusion

The shortage of adequate organ donors remains a great challenge in clinical lung transplantation. With increasing experience in the medical management and surgical technique of lung transplantation, gradual expansion of the criteria for lung donor selection has occurred with beneficial effects on the donor pool. Interest in donation after cardiac death also is increasing as the gap increases between donors and the needs of listed patients. Successful use of these new sources of lungs depends on the accurate assessment and prediction of transplanted lung function. Promising techniques for lung assessment and diagnostics include investigating key genes associated with graft failure or good graft performance using molecular approaches, and ex vivo evaluation. Further studies are needed to answer remaining questions about the best technique and solution to reperfuse human lungs for several hours without edema formation. As the predictive ability to discern good from injured donor lungs improves, strategies to repair donor lungs become increasingly important. Prolonged normothermic EVLP seems to be a platform on which many reparative strategies can be realized. With these new methods for assessing and resuscitating lungs accurately, it is hoped that inroads will be made toward providing every listed patient a chance for successful lung transplantation.

Inhibition of nuclear factor κB by IκB superrepressor gene transfer ameliorates ischemia-reperfusion injury after experimental lung transplantation

OBJECTIVES

Ischemia-reperfusion injury after lung transplantation is associated with significant morbidity and mortality. The activation of the transcription factor nuclear factor kappaB is central to the 2 important pathways that characterize ischemia-reperfusion injury, namely the inflammatory response and apoptosis. The purpose of this study was to determine the effects of nuclear factor kappaB inhibition on experimental lung transplant ischemia-reperfusion injury with gene transfer of the nuclear factor kappaB inhibitor IkappaB in a superrepressor form (IkappaBSR).

METHODS

An orthotopic left lung transplant model in isogeneic rats was used, with 18 hours of prolonged cold storage of donor lung grafts used to create severe ischemia-reperfusion injury. Donor rats underwent endobronchial gene transfection with saline alone or adenovirus encoding either beta-galactosidase control or IkappaBSR 48 hours before harvest. The function of transplanted lung grafts was assessed on the basis of isolated graft oxygenation, wet/dry lung weight ratio, and myeloperoxidase activity. Nuclear factor kappaB activation was assessed by means of enzyme-linked immunosorbent assay. Apoptotic cell death was assessed by evaluating the levels of histone-associated DNA fragments and caspase-3 activity.

RESULTS

Treatment of donor lung grafts with IkappaBSR resulted in significantly improved oxygenation compared with that seen in control tissue 24 hours after transplantation. IkappaBSR-treated lungs also demonstrated less pulmonary edema and reduced neutrophil infiltration 24 hours after reperfusion. Nuclear factor kappaB activation and apoptotic cell death induction 2 hours after transplantation was significantly reduced in IkappaBSR-treated lungs compared with in control lungs.

CONCLUSIONS

Inhibition of nuclear factor kappaB activation by IkappaBSR gene transfer improves transplanted lung graft oxygenation, decreases pulmonary edema and neutrophil sequestration, and reduces apoptotic cell death after experimental lung transplantation.

In vivo molecular imaging characterizes pulmonary gene expression during experimental lung transplantation

Experimental gene therapy is a promising strategy to prevent ischemia-reperfusion (I/R) injury and allograft rejection after lung transplantation, and methods will eventually be needed to characterize pulmonary transgene expression in vivo in humans. Therefore, we studied positron emission tomography (PET) as a means of performing in vivo molecular imaging in rodent models of lung transplantation. Rats were transfected endotracheally with adenovirus encoding a fusion gene of a mutant Herpes simplex virus-1 thymidine kinase and the green fluorescent protein gene (the former serving as an imaging reporter gene). Twenty-four hours after transfection, lungs were transplanted in groups representing normal transplantation, I/R injury and acute allograft rejection. Imaging was obtained either 24 h after transplantation to study reperfusion injury or 4 days after transplantation to study graft rejection. After imaging, lungs were excised and analyzed for thymidine kinase activity. Imaging detected transgene expression in transplanted lungs even in the presence of acute rejection or I/R injury. The PET imaging signal correlated with in vitro lung tissue assays of thymidine kinase activity (r(2) = 0.534). Thus, noninvasive molecular imaging with PET is a feasible, sensitive and quantitative method for characterizing pulmonary transgene expression in experimental lung transplantation.

Recipient intramuscular cotransfection of transforming growth factor β1 and interleukin 10 ameliorates acute lung graft rejection

OBJECTIVE

Multiple gene transfer might permit modulation of concurrent biochemical pathways involved in acute lung graft rejection. We investigated whether gene cotransfection into the recipient reduces acute lung graft rejection.

METHODS

Brown Norway rats were used as donors, and F344 rats were used as recipients. Recipient animals were injected with saline (groups I/VI) or 1 x 10(10) pfu of adenovirus encoding beta-galactosidase (groups II/VII), transforming growth factor beta1 (groups III/VIII), interleukin 10 (groups IV/IX), or both transforming growth factor beta1 and interleukin 10 (groups V/X) into both leg muscles 2 days before transplantation (groups I-V) or at the time of harvest (groups VI-X). The Kruskal-Wallis test for rejection score and 1-way analysis of variance were used to compare groups.

RESULTS

Oxygenation was significantly improved in the cotransfected groups treated 2 days before transplantation and at the time of harvest. Rejection scores were also reduced in the cotransfected groups. In group V cotransfection suppressed endogenous interleukin 2 but not interferon gamma and tumor necrosis factor alpha.

CONCLUSION

Recipient intramuscular cotransfection of transforming growth factor beta1 and interleukin 10 suppressed interleukin 2 expression and provided a synergistic effect that reduced acute lung graft rejection. This approach might be applied to the clinical setting because transplant recipients could be treated at the time of implantation.

Growth hormone (GH) action in the developing lung: Changes in lung proteins after adenoviral GH overexpression

Growth hormone (GH) recently has been shown to be expressed in the neonatal rat lung during alveolarization. The possible functional importance of lung GH in lung function, therefore, has been assessed by determining changes in GH-responsive proteins in the developing rat lung after the overexpression of the GH gene in this tissue. GH overexpression was achieved using an adenovirus that expressed the mouse GH gene. This adenovirus was effective in inducing mouse GH expression in cultured rat lung L2 epithelial cells. It was also shown to be strongly expressed in the alveoli of 14-day-old rat pup lungs 10 days after it was administered by intratracheal injection, during a period of rapid lung development. Expression of the transgene in these pups was accompanied by changes in lung protein concentrations determined by two-dimensional gel electrophoresis and mass spectrometry. The lung concentrations of specific enzymes (nucleotide diphosphate kinase B, Cu/Zn superoxide dismutase, glutathione-S-transferase, and aldehyde reductase-1) were increased by the adenoviral expression of mouse GH, as were the concentrations of beta subunit G-protein calponin 2, beta-5 tubulin, retinoblastoma binding protein 4, and fetuin A. In contrast, the lung concentrations of haptoglobin and major acute phase alpha-1 protein were reduced by adenoviral expression of mouse GH. Although most of these proteins have not previously been identified as GH-responsive proteins, these results demonstrate actions of GH in the rat lung and support the possibility that GH acts as an autocrine/paracrine during early lung development.

Endobronchial Gene Transfer of Soluble Type I Interleukin-1 Receptor Ameliorates Lung Graft Ischemia-Reperfusion Injury

BACKGROUND

Soluble type I interleukin-1 receptor is a competitive inhibitor of interleukin-1 and may reduce its proinflammatory actions. The objective of this experiment was to demonstrate that endobronchial gene transfer of soluble type I interleukin-1 receptor IgG to donor lung grafts reduces posttransplant ischemia-reperfusion injury.

METHODS

All experiments utilized an orthotopic left lung isograft transplant model. Donors were divided into three groups (n = 6 each) for endobronchial transfection: group I received 2 x 10(7) plaque-forming units of adenovirus encoding soluble type I interleukin-1 receptor IgG; group II received 2 x 10(7) plaque-forming units of nonfunctional control adenovirus encoding beta-galactosidase; and group III received 0.1 mL of saline. Left lungs were harvested 24 hours after transfection and stored for 18 hours before transplantation. Graft function was assessed 24 hours after reperfusion using three measurements: isolated graft oxygenation, wet-to-dry lung weight ratio, and tissue myeloperoxidase activity. Transgene expression of soluble type I interleukin-1 receptor IgG was also evaluated using enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

Isolated graft arterial oxygenation was significantly improved in group I compared with groups II and III (281.8 +/- 134.8 versus 115.7 +/- 121.5 and 88.0 +/- 58.9 mm Hg, p = 0.0197 and p = 0.0081, respectively). Myeloperoxidase activity was also significantly reduced in group I compared with groups II and III (0.083 +/- 0.044 versus 0.155 +/- 0.043 and 0.212 +/- 0.079 optical density units per minute per milligram protein, p = 0.0485 and p = 0.0016, respectively). Expression of soluble type I interleukin-1 receptor IgG was detected only in lungs from group I.

CONCLUSIONS

Endobronchial gene transfer of soluble type I interleukin-1 receptor IgG to donor lung grafts subjected to prolonged cold ischemia ameliorates ischemia-reperfusion injury by improving graft oxygenation and reducing lung edema and neutrophil sequestration.

Transbronchial administration of adenoviral-mediated interleukin-10 gene to the donor improves function in a pig lung transplant model

Interleukin-10 (IL-10) gene transfection of donor lungs prior to transplantation is an attractive strategy to reduce ischemia-reperfusion induced lung injury. However, experimental data with gene therapy in large animal models of lung transplantation are generally lacking. We have developed a simple clinically applicable technique for adenoviral-mediated gene delivery of human IL-10 to the lung of large animals that provides homogenous gene expression after 12-24 h of transfection. Using this technique of gene delivery, we have studied the dynamics of adenoviral gene delivery to the lung in the setting of lung transplantation. Although there is a persistent inflammatory response to the adenoviral vector, we achieved significant expression of human IL-10 in lung tissue before lung retrieval to obviate the deleterious impact of the adenoviral vector on the donor lung. The administration of adenoviral-mediated human IL-10 to the donor lung reduced ischemia-reperfusion injury and improved graft function after lung transplantation in this pig lung transplantation model. Transfection of adenoviral-mediated human IL-10 to the donor lung prevented the release of inflammatory cytokines such as IL-6 in lung tissue and plasma. We have demonstrated that IL-10 gene therapy has significant potential to prevent or treat the inflammatory response associated with ischemia-reperfusion injury in lung transplantation. In the future, IL-10 gene therapy could also be used for immunomodulation or tolerance induction.

Tumor necrosis factor inhibitor gene transfer ameliorates lung graft ischemia-reperfusion injury

OBJECTIVE

Tumor necrosis factor is an important mediator of lung transplant ischemia-reperfusion injury, and soluble type I tumor necrosis factor receptor binds to tumor necrosis factor and works as a tumor necrosis factor inhibitor. The objectives of this study were to demonstrate that gene transfer of type I tumor necrosis factor receptor-IgG fusion protein reduces lung isograft ischemia-reperfusion injury and to compare donor endobronchial versus recipient intramuscular transfection strategies.

METHODS

Three donor groups of Fischer rats (n = 6/group) underwent endobronchial transfection with either saline, 2 x 10(7) plaque-forming units of control adenovirus encoding beta-galactosidase, or 2 x 10(7) plaque-forming units of adenovirus encoding type I tumor necrosis factor receptor-IgG fusion protein. Left lungs were harvested 24 hours later. Two recipient groups (n = 6/group) underwent intramuscular transfection with 2 x 10(7) plaque-forming units or 1 x 10(10) plaque-forming units of adenovirus encoding type I tumor necrosis factor receptor-IgG fusion protein 24 hours before transplantation. All donor lung grafts were stored for 18 hours before orthotopic lung transplantation. Graft function was assessed 24 hours after reperfusion. Transgene expression was evaluated by means of enzyme-linked immunosorbent assay and immunohistochemistry of type I tumor necrosis factor receptor.

RESULTS

Endobronchial transfection of donor lung grafts with 2 x 10(7) plaque-forming units of adenovirus encoding type I tumor necrosis factor receptor-IgG fusion protein significantly improved arterial oxygenation compared with the saline and beta-galactosidase donor groups (366.6 +/- 137.9 vs 138.8 +/- 159.9 and 140.6 +/- 131.4 mm Hg, P =.009 and.010, respectively). Recipient intramuscular transfection with 1 x 10(10) plaque-forming units of adenovirus encoding type I tumor necrosis factor receptor-IgG fusion protein improved lung graft oxygenation compared with that seen in the low-dose intramuscular group (2 x 10(7); 320.3 +/- 188.6 vs 143.6 +/- 20.2 mm Hg, P =.038). Type I tumor necrosis factor receptor-IgG fusion protein was expressed in endobronchial transfected grafts. In addition, intramuscular type I tumor necrosis factor receptor-IgG fusion protein expression was dose dependent.

CONCLUSIONS

Donor endobronchial and recipient intramuscular adenovirus-mediated gene transfer of type I tumor necrosis factor receptor-IgG fusion protein improved experimental lung graft oxygenation after prolonged ischemia. However, donor endobronchial transfection required 500-fold less vector. Furthermore, at low vector doses, it does not create significant graft inflammation.