Recipient intramuscular gene transfer of active transforming growth factor-beta1 attenuates acute lung rejection

Creating superior lungs for transplantation with next-generation gene therapy during ex vivo lung perfusion

Engineering donor organs to better tolerate the harmful non-immunological and immunological responses inherently related to solid organ transplantation would improve transplant outcomes. Our enhanced knowledge of ischemia-reperfusion injury, alloimmune responses and pathological fibroproliferation after organ transplantation, and the advanced toolkit available for gene therapies, have brought this goal closer to clinical reality. Ex vivo organ perfusion has evolved rapidly especially in the field of lung transplantation, where clinicians routinely use ex vivo lung perfusion (EVLP) to confirm the quality of marginal donor lungs before transplantation, enabling safe transplantation of organs originally considered unusable. EVLP would also be an attractive platform to deliver gene therapies, as treatments could be administered to an isolated organ before transplantation, thereby providing a window for sophisticated organ engineering while minimizing off-target effects to the recipient. Here, we review the status of lung transplant first-generation gene therapies that focus on inducing transgene expression in the target cells. We also highlight recent advances in next-generation gene therapies, that enable gene editing and epigenetic engineering, that could be used to permanently change the donor organ genome and to induce widespread transcriptional gene expression modulation in the donor lung. In a future vision, dedicated organ repair and engineering centers will use gene editing and epigenetic engineering, to not only increase the donor organ pool, but to create superior organs that will function better and longer in the recipient.

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.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Pirfenidone inhibits T-cell activation, proliferation, cytokine and chemokine production, and host alloresponses

BACKGROUND

We previously showed that pirfenidone, an anti-fibrotic agent, reduces lung allograft injury or rejection. In this study, we tested the hypothesis that pirfenidone has immune modulating activities and evaluated its effects on the function of T-cell subsets, which play important roles in allograft rejection.

METHOD

We first evaluated whether pirfenidone alters T-cell proliferation and cytokine release in response to T-cell receptor (TCR) activation, and whether pirfenidone alters regulatory T cells (CD4CD25) suppressive effects using an in vitro assay. Additionally, pirfenidone effects on alloantigen-induced T-cell proliferation in vivo were assessed by adoptive transfer of carboxyfluorescein diacetate succinimidyl ester-labeled T cells across a parent->F1 major histocompatibility complex mismatch, as well as using a murine heterotopic cardiac allograft model (BALB/c->C57BL/6).

RESULTS

Pirfenidone was found to inhibit the responder frequency of TCR-stimulated CD4 cell total proliferation in vitro and in vivo, whereas both CD4 and CD8 proliferation index were reduced by pirfenidone. Additionally, pirfenidone inhibited TCR-induced production of multiple pro-inflammatory cytokines and chemokines. Interestingly, there was no change on transforming growth factor-beta production by purified T cells, and pirfenidone had no effect on the suppressive properties of naturally occurring regulatory T cells. Pirfenidone alone showed a small but significant (P<0.05) effect on the in vivo allogeneic response, whereas the combination of pirfenidone and low dose rapamycin had more remarkable effect in reducing the alloantigen response with prolonged graft survival.

CONCLUSION

Pirfenidone may be an important new agent in transplantation, with particular relevance to combating chronic rejection by inhibiting both fibroproliferative and alloimmune responses.

Pirfenidone inhibits obliterative airway disease in mouse tracheal allografts

BACKGROUND

Obliterative bronchiolitis (OB) is the histologic correlate of chronic airway rejection, which remains the most significant cause of death in long-term survivors of lung transplantation. Using an established murine heterotopic tracheal transplant model of chronic airway rejection, the effects of the oral anti-fibrotic agent pirfenidone on development of the OB-like lesion were evaluated.

METHODS

Tracheas from BALB/c mice were implanted into the sub-cutaneous tissue of C57BL/6 mice, and the allografts were evaluated morphologically for airway rejection changes and immunohistochemically for transforming growth factor (TGF)-beta at 16 or 28 days after transplantation. In addition, the potential additive effects of pirfenidone in combination with 2 immunosuppressive agents, cyclosporine or rapamycin, was evaluated.

RESULTS

Compared with untreated controls, pirfenidone-fed mice showed less epithelial cell injury and luminal granulation tissue and fibrosis. Plasma TGF-beta levels and local TGF-beta expression based on immunohistochemistry were decreased in the pirfenidone-treated animals. Pirfenidone given on Day 9 or 16 post-transplant through Day 28 resulted in no significant improvement compared with controls. There was no significant additive effect of pirfenidone in combination with cyclosporine, whereas pirfenidone plus rapamycin demonstrated additive protection against the development of the obstructive airway lesion.

CONCLUSIONS

In aggregate, these results show that the anti-fibrotic agent pirfenidone inhibits the development of the OB-like lesion in this mouse model of human chronic airway rejection, and that these effects may be mediated by TGF-beta. The results also suggest that pirfenidone may be worthy of investigation in human lung transplant recipients at high risk of developing OB.

Gene Therapy for Lung Diseases

Gene therapy is under development for a variety of lung disease, both those caused by single gene defects, such as cystic fibrosis and α₁-antitrypsin deficiency, and multifactorial diseases such as cancer, asthma, lung fibrosis, and ARDS. Both viral and nonviral approaches have been explored, the major limitation to the former being the inability to repeatedly administer, which renders this approach perhaps more applicable to conditions requiring single administration, such as cancer. Progress in development and clinical trials in each of these diseases is reviewed, together with some potential newer approaches for the future.

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.

Gene transfer of tumor necrosis factor inhibitor improves the function of lung allografts

BACKGROUND

Tumor necrosis factor is an important mediator of lung transplant acute rejection. Soluble type I tumor necrosis factor receptor binds to tumor necrosis factor-alpha and -beta and inhibits their function. The objectives of this study were to demonstrate efficient in vivo gene transfer of a soluble type I tumor necrosis factor receptor fusion protein (sTNF-RI-Ig) and determine its effects on lung allograft acute rejection.

METHODS

Three groups of Fischer rats (n = 6 per group) underwent recipient intramuscular transfection 24 hours before transplantation with saline, 1 x 10(10) plaque-forming units of control adenovirus encoding beta-galactosidase, or 1 x 10(10) plaque-forming units of adenovirus encoding human sTNF-RI-Ig (Ad.sTNF-RI-Ig). One group (n = 6) received recipient intramuscular transfection with 1 x 10(10) Ad.sTNF-RI-Ig at the time of transplantation. Brown Norway donor lung grafts were stored for 5 hours before orthotopic lung transplantation. Graft function and rejection scores were assessed 5 days after transplantation. Time-dependent transgene expression in muscle, serum, and lung grafts were evaluated by using enzyme-linked immunosorbent assay of human soluble type I tumor necrosis factor receptor.

RESULTS

Recipient intramuscular transfection with 1 x 10(10) plaque-forming units of Ad.sTNF-RI-Ig significantly improved arterial oxygenation when delivered 24 hours before transplantation compared with saline, beta-galactosidase, and Ad.sTNF-RI-Ig transfection at the time of transplantation (435.8 +/- 106.6 mm Hg vs 142.3 +/- 146.3 mm Hg, 177.4 +/- 153.7 mm Hg, and 237.3 +/- 185.2 mm Hg; P =.002,.005, and.046, respectively). Transgene expression was time dependent, and there was a trend toward lower vascular rejection scores (P =.066) in the Ad.sTNF-RI-Ig group transfected 24 hours before transplantation.

CONCLUSIONS

Recipient intramuscular Ad.sTNF-RI-Ig gene transfer improves allograft function in a well-established model of acute rejection. Maximum benefit was observed when transfection occurred 24 hours before transplantation.

Attenuation of Reperfusion-Induced Systemic Inflammation by Preconditioning With Nitric Oxide in an In Situ Porcine Model of Normothermic Lung Ischemia

STUDY OBJECTIVES

Inhalation of nitric oxide (NO) can ameliorate pulmonary ischemia/reperfusion (I/R) injury of the lung in several experimental models, but toxic effects of NO were also reported. Here we investigate whether NO inhalation for a short period prior to surgery is sufficient to prevent symptoms of lung I/R injury, especially the inflammatory response.

DESIGN

Using an in situ porcine lung model, normothermic left lung ischemia was maintained for 90 min, followed by a 5-h reperfusion period (group 1, n = 7). In group 2 (n = 6), I/R was preceded by inhalation of NO (10 min, 15 ppm). Animals in group 3 (n = 7) underwent sham surgery without NO inhalation or ischemia.

MEASUREMENTS

Oxygenation and hemodynamic parameters were measured as indicators of lung functional impairment. Plasma levels of interleukin (IL)-1beta, IL-6, and transforming growth factor (TGF)-beta1 were determined throughout the I/R maneuver. In addition, tissue macrophages were analyzed by lectin binding.

RESULTS

Symptoms of I/R injury (pulmonary hypertension and decreased oxygenation) in group 1 animals were attenuated by NO inhalation. The reperfusion-induced increases of the levels of IL-1beta and IL-6 in plasma were reduced by NO pretreatment. A peak of TGF-beta1 immediately after NO administration was observed in group 2, but not in groups 1 and 3. There was no significant effect of NO on tissue macrophages.

CONCLUSION

NO inhalation for a short period prior to lung I/R is sufficient to protect against pulmonary hypertension, impaired oxygenation, and the inflammatory response of pulmonary I/R injury.

Optimal modes and targets of gene therapy in transplantation

Genetic modification strategies have the potential to improve outcome following cell/organ transplantation. A unique opportunity in transplantation is that gene therapies need not be restricted to in vivo approaches and that ex vivo genetic modification of cell and/or organs can be of value. Improvements in vector design, production, and delivery should enhance transfection efficiency and optimize gene expression. Herein, we discuss potential modes of gene therapy, focusing on viral, liposome, or naked DNA-based systems for gene delivery. We suggest gene therapy targets taking into consideration the essential constituents of anti-allograft repertory. In addition to strategies that may have salutary effects in mitigating the threat of acute rejection, we suggest genetic strategies for minimizing ischemia/reperfusion injury as well as for the perennial problem of progressive functional loss of the transplanted organ. Data from pre-clinical transplant models support the idea that gene therapy may improve allograft function and survival. We are optimistic that gene therapy will be of clinical value in the near future in the management of recipients of allografts; we believe that genetic strategies would be essential for successful breaching of the formidable challenge of xenotransplantation.

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.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Medical applications of transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) proteins and their antagonists have entered clinical trials. These multi-functional regulators of cell growth and differentiation induce extracellular matrix proteins and suppress the immune system making TGF-betas useful in treatment of wounds with impaired healing, mucositis, fractures, ischemia-reperfusion injuries, and autoimmune disease. In diseases such as keloids, glomerulonephritis and pulmonary fibrosis, excessive expression of TGF-beta has been implicated as being responsible for accumulation of detrimental scar tissue. In these conditions, agents that block TGF-beta have prevented or reversed disease. Similarly, in carcinogenesis, blocking TGF-beta activity may be valuable in stimulating an immune response towards metastasis. As these blocking agents receive approval, we will likely have new therapies for previously recalcitrant diseases.

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.

Intramuscular gene transfer of interleukin-10 reduces neutrophil recruitment and ameliorates lung graft ischemia-reperfusion injury

Interleukin-10 (IL-10) has potent anti-inflammatory properties but its direct effects on neutrophil trafficking in lung transplant ischemia-reperfusion (I/R) injury are unknown. This study was performed to determine if recipient intramuscular IL-10 gene transfer reduces neutrophil infiltration in lung isografts and ameliorates I/R injury. Twenty-four hours before transplantation, recipient rodents received intramuscular injection with 1 x 10(10) plaque-forming units (pfu) adenovirus encoding human IL-10 (hIL-10), 1 x 10(10) pfu adenovirus control encoding p-galactosidase, or saline. Gene expression in muscle and plasma was confirmed. Lung grafts were harvested, stored at 4 degrees C for 18h, and assessed 24 h after transplantation. Peak muscle and plasma expression of hIL-10 was achieved 24h after gene transfer and returned to baseline by 7 days (p < 0.05 vs. controls). Gene transfer of hIL-10 reduced neutrophil sequestration and emigration in lung grafts as measured by morphometry and myeloperoxidase activity (p < 0.03 vs. controls). Furthermore, hIL-10 improved graft oxygenation and reduced lung edema (p <0.01 vs. controls). Intramuscular gene transfer of hIL-10 releases hIL-10 protein into plasma and reduces neutrophil sequestration and emigration in lung isografts. This is associated with a reduction in I/R injury with improved isograft oxygenation and reduced tissue edema. Intramuscular gene transfer may be a useful strategy to reduce clinical l/R injury.

Recipient intramuscular cotransfection of naked plasmid transforming growth factor beta1 and interleukin 10 ameliorates lung graft ischemia-reperfusion injury

OBJECTIVE

Multiple gene transfer might permit modulation of concurrent biochemical pathways involved in lung graft ischemia-reperfusion injury. In this study we analyzed whether recipient intramuscular naked plasmid cotransfection of transforming growth factor beta(1) and interleukin 10 would result in amelioration of lung graft ischemia-reperfusion injury.

METHODS

Forty-eight hours before transplantation, 6 groups (n = 6) of F344 rats received intramuscular injection of naked plasmid encoding chloramphenicol acetyltransferase, chloramphenicol acetyltransferase plus beta-galactosidase, transforming growth factor beta(1), interleukin 10, or transforming growth factor beta(1) plus interleukin 10 or were not treated. Donor lungs were flushed and stored for 18 hours at 4 degrees C before transplantation. Twenty-four hours later, grafts were assessed immediately before the animals were killed. Arterial oxygenation, wet/dry ratio, myeloperoxidase, and proinflammatory cytokines (interleukin 1, tumor necrosis factor alpha, interferon gamma, and interleukin 2) were measured, and immunohistochemistry was performed.

RESULTS

For lung graft function, the arterial oxygenation was considerably higher in the cotransfected group receiving transforming growth factor beta(1) plus interleukin 10 compared with that in all other groups (P < or =.03). The wet/dry ratio, reflecting lung edema, was reduced in the cotransfected group compared with that in control animals (nontreated, P <.02; chloramphenicol acetyltransferase, P <.03; chloramphenicol acetyltransferase plus beta-galactosidase, P <.01). Myeloperoxidase, which measures neutrophil sequestration, was also reduced with cotransfection compared with that seen in control animals (P < or =.03). All proinflammatory cytokines were decreased in the cotransfected group compared with those in all other groups (interleukin 1beta, P <.04; tumor necrosis factor alpha, P <.002; interferon gamma, P <.0001; interleukin 2, P <.03). These results indicate that cotransfection provides a synergistic benefit in graft function versus either cytokine alone, neutrophil sequestration, or inflammatory cytokine expression. Immunohistochemistry showed positive staining of transforming growth factor beta(1) plus interleukin 10 in type I and II pneumocytes and localized edema fluid.

CONCLUSIONS

Recipient intramuscular naked plasmid cotransfection of transforming growth factor beta(1) and interleukin 10 provides a synergistic effect in ameliorating lung reperfusion injury after prolonged ischemia.

Low-dose endobronchial gene transfer to ameliorate lung graft ischemia-reperfusion injury

OBJECTIVE

This study was undertaken to determine whether low-dose endobronchial transfer to the donor of the gene for human interleukin 10 would decrease ischemia-reperfusion injury in lung transplantation.

METHODS

Experiments used male Fischer rats. Donor animals underwent right thoracotomy. A catheter was introduced into the left main bronchus, and vector was instilled. Group I (n = 6) received 2 x 10(7) plaque-forming units of adenovirus encoding human interleukin 10, group II (n = 6) received an adenovirus control encoding beta-galactosidase, and group III (n = 6) received saline solution. After instillation the left main bronchus was clamped for 60 minutes. Lungs were removed 24 hours later and stored in low-potassium dextran glucose solution for 18 hours before left lung transplantation. Graft function was assessed at 24 hours immediately before the animals were killed. Ratio of wet to dry weight and tissue myeloperoxidase activity were measured. Transgenic expression of human interleukin 10 was evaluated by means of enzyme-linked immunosorbent assay and immunohistochemical assay.

RESULTS

Arterial oxygenation was significantly improved in group I relative to groups II and III (257.6 +/- 59.7 mm Hg vs 114.6 +/- 66.9 mm Hg and 118.6 +/- 91.1 mm Hg, P =.008 and P =.007, respectively). Neutrophil sequestration, as measured by myeloperoxidase activity, was also significantly reduced in group I relative to groups II and III (0.141 +/- 0.025 vs 0.304 +/- 0.130 and 0.367 +/- 0.153 Delta optical density units/[min. mg protein], P =.029 and P =.004, respectively). Enzyme-linked immunosorbent assay and immunohistochemical assay demonstrated the expression of human interleukin 10 in transfected lungs only.

CONCLUSIONS

Low-dose endobronchial transfer to the donor of the gene for human interleukin 10 ameliorated ischemia-reperfusion injury in rodent lung transplantation by improving graft oxygenation and reducing neutrophil sequestration. Only 2 x 10(7) plaque-forming units of adenoviral vector were required for functional transgenic expression. Endobronchial gene transfer to lung grafts may be a useful delivery route even at low doses.