S. Hirayama

Technique for Prolonged Normothermic Ex Vivo Lung Perfusion

BACKGROUNDnThe inhibition of cellular metabolism induced by hypothermia obviates the possibility of substantial reparative processes occurring during organ preservation. The aim of this study was to develop a technique of extended (12-hour) ex vivo lung perfusion (EVLP) at normothermia for assessment and protective maintenance of the donor lung.nnnMETHODSnSix double-lung blocks from 35-kg pigs and 5 single human lungs were subjected to 12 hours of normothermic EVLP using acellular Steen Solution. In the animal studies, the left lung was transplanted into recipients at the end of EVLP and reperfused for 4 hours to evaluate the impact of prolonged EVLP on post-transplant lung function. A protective mode of mechanical ventilation with controlled perfusion flows and pressures in the pulmonary vasculature were employed during EVLP. Lung oxygenation capacity (DeltaPo(2)), pulmonary vascular resistance and airway pressures were evaluated in the system. Red blood cells were added to the perfusate to a hematocrit of 20% at the end of human lung EVLP to study lung functional assessment with and without cells.nnnRESULTSnLung function was stable during 12 hours of EVLP. This stability during prolonged normothermic EVLP translated into excellent post-transplant lung function (Pao(2)/Fio(2): 527 +/- 22 mm Hg), low edema formation (wet/dry ratio: 5.24 +/- 0.38) and preserved lung histology after transplantation. The acellular perfusion assessment of lung function accurately correlated with post-transplant graft function.nnnCONCLUSIONSnTwelve hours of EVLP at physiologic temperatures using an acellular perfusate is achievable and maintains the donor lungs without inflicting significant added injury. This system can be used to assess, maintain and treat injured donor lungs.

Functional Repair of Human Donor Lungs by IL-10 Gene Therapy

Treatment of damaged donor lungs with the cytokine interleukin-10 improves their function, allowing previously unacceptable organs to be used for transplantation. Living Well After Lung Replacement Bumper stickers that counsel motorists to “just breathe” abound—easier said than done when it comes to patients with serious lung disorders. Lung transplantations are on the rise, from 203 in 1990 to more than 1200 in 2008 in the United States. Earlier this year, transplant surgeons at Johns Hopkins presented evidence that more is better—hospitals that perform 20 or more lung transplants per year have the best patient survival rates. However, successful surgeries require healthy donor lungs, a resource that remains in short supply. Now, Keshavjee and colleagues describe a gene therapy treatment protocol to repair lungs after removal from the donor and before transplantation into patients. Candidates for lung transplantation are patients suffering from end-stage lung diseases, such as emphysema, cystic fibrosis, pulmonary fibrosis, and pulmonary arterial hypertension. Organ donors are people who have undergone brain death, a process that is as violent as it sounds: Brain death is accompanied by the spewing of inflammation-inducing molecules called cytokines that damage more than 80% of donated lungs. These injured organs are highly inflamed, and their alveoli—the gas exchange machinery in lungs—are disrupted and only mildly functional. To avoid primary graft dysfunction—lung damage that occurs within the 72 hours after transplantation—transplant surgeons usually reject such injured organs. A method is needed to heal these fixer-upper organs so that they can be used to give patients a new lease on life. Using IL-10, an anti-inflammatory cytokine, Keshavjee’s team devised a treatment to quell inflammation in the injured donor lungs and refurbish the alveoli. Although the standard technique for the handling of organs is to keep them on ice in a sealed bag, this IL-10 gene therapy approach must be performed at body temperature so that the lung’s cellular machinery can express the gene efficiently. The researchers then carried out prolonged ex vivo lung perfusion (EVLP) and kept the lungs breathing outside the body in conditions that mimic physiological ones. Pig lungs that were subjected to IL-10 gene therapy and EVLP for 12 hours displayed reduced inflammation and enhanced function when transplanted into donor pigs, relative to control organs. The same treatment was applied to human lungs deemed unsuitable for transplantation, and these organs, relative to controls, displayed the presence of anti-inflammatory cytokines, repair of alveoli, and improved function, determined by measuring gas exchange and pulmonary vascular resistance. This procedure can yield a larger number of usable lungs and thus more successful transplantations so that patients can “just breathe.” More than 80% of potential donor lungs are injured during brain death of the donor and from complications experienced in the intensive care unit, and therefore cannot be used for transplantation. These lungs show inflammation and disruption of the alveolar-capillary barrier, leading to poor gas exchange. Although the number of patients in need of lung transplantation is increasing, the number of donors is static. We investigated the potential to use gene therapy with an adenoviral vector encoding human interleukin-10 (AdhIL-10) to repair injured donor lungs ex vivo before transplantation. IL-10 is an anti-inflammatory cytokine that mainly exerts its suppressive functions by the inactivation of antigen-presenting cells with consequent inhibition of proinflammatory cytokine secretion. In pigs, AdhIL-10–treated lungs exhibited attenuated inflammation and improved function after transplantation. Lungs from 10 human multiorgan donors that had suffered brain death were determined to be clinically unsuitable for transplantation. They were then maintained for 12 hours at body temperature in an ex vivo lung perfusion system with or without intra-airway delivery of AdhIL-10 gene therapy. AdhIL-10–treated lungs showed significant improvement in function (arterial oxygen pressure and pulmonary vascular resistance) when compared to controls, a favorable shift from proinflammatory to anti-inflammatory cytokine expression, and recovery of alveolar–blood barrier integrity. Thus, treatment of injured human donor lungs with the cytokine IL-10 can improve lung function, potentially rendering injured lungs suitable for transplantation into patients.

Normothermic Ex Vivo Perfusion Prevents Lung Injury Compared to Extended Cold Preservation for Transplantation

Treatment of injured donor lungs ex vivo to accelerate organ recovery and ameliorate reperfusion injury could have a major impact in lung transplantation. We have recently demonstrated a feasible technique for prolonged (12 h) normothermic ex vivo lung perfusion (EVLP). This study was performed to examine the impact of prolonged EVLP on ischemic injury. Pig donor lungs were cold preserved in Perfadex® for 12 h and subsequently divided into two groups: cold static preservation (CSP) or EVLP at 37°C with Steen™ solution for a further 12 h (total 24 h preservation). Lungs were then transplanted and reperfused for 4 h. EVLP preservation resulted in significantly better lung oxygenation (PaO2 531 ± 43 vs. 244 ± 49 mmHg, p < 0.01) and lower edema formation rates after transplantation. Alveolar epithelial cell tight junction integrity, evaluated by zona occludens‐1 protein staining, was disrupted in the cell membranes after prolonged CSP but not after EVLP. The maintenance of integrity of barrier function during EVLP translates into significant attenuation of reperfusion injury and improved graft performance after transplantation. Integrity of functional metabolic pathways during normothermic perfusion was confirmed by effective gene transfer and GFP protein synthesis by lung alveolar cells. In conclusion, EVLP prevents ongoing injury associated with prolonged ischemia and accelerates lung recovery.

The Role of Intrapulmonary De Novo Lymphoid Tissue in Obliterative Bronchiolitis after Lung Transplantation

Chronic rejection after lung transplantation is manifested as obliterative bronchiolitis (OB). The development of de novo lymphoid tissue (lymphoid neogenesis) may contribute to local immune responses in small airways. Compared with normal lungs, the lung tissue of 13 lung transplant recipients who developed OB demonstrated a significantly larger number of small, airway-associated, peripheral node addressin-positive (PNAd+) high endothelial venules (HEVs) unique to lymphoid tissue (p < 0.001). HEVs were most abundant in lesions of lymphocytic bronchiolitis and “active” OB infiltrated by lymphocytes compared with those of “inactive” OB. T cells in lymphocytic bronchiolitis and active OB were predominantly of the CD45RO+CCR7− effector memory phenotype. Similar lymphoid tissue was also observed in the rat lung after intrapulmonary transplantation of allograft trachea (Brown Norway (BN) to Lewis), but not after isograft transplantation. Subsequent orthotopic transplantation of the recipient Lewis lung containing a BN trachea into an F1 (Lewis × BN) rat demonstrated stable homing of Lewis-derived T cells in the lung and their Ag-specific effector function against the secondary intrapulmonary BN trachea. In conclusion, we found de novo lymphoid tissue in the lung composed of effector memory T cells and HEVs but lacking delineated T cell and B cell zones. This de novo lymphoid tissue may play a critical role in chronic local immune responses after lung transplantation.

Lentivirus IL‐10 Gene Therapy Down‐Regulates IL‐17 and Attenuates Mouse Orthotopic Lung Allograft Rejection

The purpose of the study was to examine the effect of lentivirus‐mediated IL‐10 gene therapy to target lung allograft rejection in a mouse orthotopic left lung transplantation model. IL‐10 may regulate posttransplant immunity mediated by IL‐17. Lentivirus‐mediated trans‐airway luciferase gene transfer to the donor lung resulted in persistent luciferase activity up to 6 months posttransplant in the isograft (B6 to B6); luciferase activity decreased in minor‐mismatched allograft lungs (B10 to B6) in association with moderate rejection. Fully MHC‐mismatched allograft transplantation (BALB/c to B6) resulted in severe rejection and complete loss of luciferase activity. In minor‐mismatched allografts, IL‐10‐encoding lentivirus gene therapy reduced the acute rejection score compared with the lentivirus‐luciferase control at posttransplant day 28 (3.0u2009±u20090.6 vs. 2.0u2009±u20090.6 (meanu2009±u2009SD); pu2009=u20090.025; nu2009=u20096/group). IL‐10 gene therapy also significantly reduced gene expression of IL‐17, IL‐23, and retinoic acid‐related orphan receptor (ROR)‐γt without affecting levels of IL‐12 and interferon‐γ (IFN‐γ). Cells expressing IL‐17 were dramatically reduced in the allograft lung. In conclusion, lentivirus‐mediated IL‐10 gene therapy significantly reduced expression of IL‐17 and other associated genes in the transplanted allograft lung and attenuated posttransplant immune responses after orthotopic lung transplantation.

Stromal activation and formation of lymphoid-like stroma in chronic lung allograft dysfunction.

Background. Lymphoid neogenesis is associated with the development of chronic lung allograft dysfunction (CLAD). Activation of stromal resident cells may be an important mechanism of lymphoid neogenesis. Methods. Twenty CLAD lungs explanted for retransplantation were immunohistochemically examined for lymphoid neogenesis, ectopic lymphoid chemokines, and dendritic cells (DCs). Formation of peripheral lymph node addressin (PNAd)+ high endothelial venule (HEV)-like vessels was examined in 134 transbronchial biopsies taken over 2 years posttransplant from 20 consecutive lung transplant recipients. Results. CLAD lungs were characterized by higher grades of CXCL12 in alveolar (P=0.002) and airway epithelial cells (P=0.001), CCL21+ lymph vessels (P=0.01), and infiltration of DC-specific intercellular adhesion molecule-grabbing nonintegrin+ immature DCs (P=0.056) than normal control lungs. Activation of stromal resident cells in CLAD lungs was highlighted by formation of lymphoid-like stroma including expression of CCL21 and CXCL13, fibroblastic reticular-like cells and DC-specific lysosome-associated membrane protein+ mature DCs in association with a significantly larger number of lymphoid aggregates (P<0.001) with lymphangitc distribution compared with normal lungs. A larger number of PNAd+ HEV-like vessels were also observed outside of lymphoid aggregates with a lymphangitic distribution (P<0.001). HEV-like vessels in transbronchial biopsies were more graded in lungs that eventually developed CLAD (n=7) than those that did not (n=13) by 3 years after transplantation (P=0.001). Conclusion. Lymphoid neogenesis associated with CLAD accompanies activation of stromal resident cells and formation of lymphoid-like stroma. Induction of PNAd+ HEV-like vessels occurs before the manifestation of CLAD.

Local Long-Term Expression of Lentivirally Delivered IL-10 in the Lung Attenuates Obliteration of Intrapulmonary Allograft Airways

Obliterative bronchiolitis (OB) is a form of chronic rejection after lung transplantation. Lentiviral vectors (LVs) facilitate long-term gene transduction in many tissues and organs. We hypothesized that lentiviral gene transfer of interleukin (IL)-10, a potent immune-modulating cytokine, to the lung could modulate the alloimmune responses in the lung after transplantation. C57BL6 mice received LVs encoding luciferase, enhanced green fluorescent protein (eGFP), or human IL-10 (huIL-10) through airways and underwent repeated bioluminescent imaging, immunofluorescence imaging, or ELISA of lung tissues, respectively. Luciferase activities peaked at day 7 and were stable after day 28 to over 15 months. eGFP staining demonstrated LV-mediated gene transduction mainly in alveolar macrophages. LV-huIL-10 delivery resulted in stable long-term expression of huIL-10 in the lung tissue (average 3.66u2009pg/mg at 1 year). Intrapulmonary allograft tracheal transplantation (BALBc→C57BL6) was used as a model of OB. LV-huIL-10 or LV-eGFP were delivered 7 days before transplantation and compared with no LV-transfection group. Allograft airways at day 28 were almost completely obliterated in all the groups. However, at day 42, allograft airways treated with LV-huIL-10 showed a spectrum of attenuation in airway fibrosis ranging from complete obliteration through bubble-like partial opening to complete patency with epithelial coverage in association with a significantly reduced obliteration ratio compared with the other groups (p<0.05). In conclusion, lentivirus-mediated gene transduction is useful in achieving long-term transgene expression in the lung. Long-term IL-10 expression has the potential to attenuate allograft airway obliteration. LV-mediated gene therapy could be a useful strategy to prevent or treat OB after lung transplantation.

MMP-dependent migration of extrapulmonary myofibroblast progenitors contributing to posttransplant airway fibrosis in the lung.

Myofibroblasts play a central role in fibroproliferative airway remodeling in obliterative bronchiolitis (OB) after lung transplantation. The purpose of the study is to elucidate the mechanisms whereby matrix metalloproteinases (MMPs) contribute to myofibroblast‐mediated allograft airway fibrosis. In an intrapulmonary tracheal transplant model of OB, broad‐spectrum MMP inhibitors, SC080 and MMI270 reduced the number of myofibroblasts at day 28 without changing differentiation, proliferation or apoptosis of myofibroblasts or fibroblasts. Next, myofibroblasts in allograft airway fibrosis were demonstrated to be almost exclusively of extrapulmonary origin by analyzing RT1An positive myofibroblasts in an animal model combining orthotopic lung transplantation (from Lewis (RT1Al) to F1 (Brown–Norway (RT1An) × Lewis)) and intrapulmonary tracheal transplantation (from a Wister–Furth rat (RT1Au) into the transplanted Lewis‐derived lung). Using peripheral blood mononuclear cells (PBMCs) that can differentiate into α‐SMA positive myofibroblasts in vitro, we demonstrated their contribution to the myofibroblast population of allograft airway fibrosis in vivo using a fluorescence‐labeling cell tracking system. Moreover, PBMC‐derived fibroblast‐like cells expressed high levels of MMP‐9 and MMP‐12 and their migration was inhibited by MMP inhibitors in a wound healing assay. In conclusion, MMP‐dependent migration of PBMC‐derived myofibroblast precursors is an important contributing mechanism to the development of allograft airway fibrosis.

Halofuginone treatment reduces interleukin-17A and ameliorates features of chronic lung allograft dysfunction in a mouse orthotopic lung transplant model.

BACKGROUNDnIncreasing evidence suggests that interleukin (IL)-17A plays an important role in chronic lung allograft dysfunction (CLAD), characterized by airway and lung parenchymal fibrosis, after lung transplantation. Halofuginone is a plant derivative that has been shown to inhibit Th17 differentiation. The purpose of this study was to examine the effect of halofuginone on CLAD development using a minor alloantigen‒mismatched mouse orthotopic lung transplant model.nnnMETHODSnC57BL/6 recipient mice received an orthotopic left lung transplant from C57BL/10 donors, mismatched for minor antigens. Lung transplant recipients received daily intraperitoneal injections of 2.5 μg halofuginone or vehicle alone. Lung grafts were assessed on Days 7, 14, and 28 post-transplant.nnnRESULTSnCompared with control mice, on Day 28 post-transplant, lung grafts of mice treated with halofuginone showed a significant reduction in the percentage of obliterated airways (6.8 ± 4.7% vs 52.5 ± 13.8%, p < 0.01), as well as significantly reduced parenchymal fibrosis (5.5 ± 2.3% vs 35.9 ± 10.9%, p < 0.05). Immunofluorescent staining for IL-17A demonstrated a decreased number and frequency of IL-17A‒positive cells in halofuginone-treated lung grafts on Day 28, as compared with controls. Halofuginone treatment also decreased IL-17A and IL-22 transcripts at Day 14, transforming growth factor-β1 and matrix metalloproteinase-2 transcripts at Days 14 and 28.nnnCONCLUSIONnThe beneficial effect of halofuginone on development of airway and lung parenchymal fibrosis in the mouse lung transplant model highlights the important role of IL-17A in CLAD and merits further pre-clinical and clinical studies.

Regression of Allograft Airway Fibrosis: The Role of MMP-Dependent Tissue Remodeling in Obliterative Bronchiolitis after Lung Transplantation

Obliterative bronchiolitis after lung transplantation is a chronic inflammatory and fibrotic condition of small airways. The fibrosis associated with obliterative bronchiolitis might be reversible. Matrix metalloproteinases (MMPs) participate in inflammation and tissue remodeling. MMP-2 localized to myofibroblasts in post-transplant human obliterative bronchiolitis lesions and to allograft fibrosis in a rat intrapulmonary tracheal transplant model. Small numbers of infiltrating T cells were also observed within the fibrosis. To modulate inflammation and tissue remodeling, the broad-spectrum MMP inhibitor SC080 was administered after the allograft was obliterated, starting at post-transplant day 21. The allograft lumen remained obliterated after treatment. Only low-dose (2.5 mg/kg per day) SC080 significantly reduced collagen deposition, reduced the number of myofibroblasts and the infiltration of T cells in association with increased collagenolytic activity, increased MMP-2 gene expression, and decreased MMP-8, MMP-9, and MMP-13 gene expression. In in vitro experiments using cultured myofibroblasts, a relatively low concentration of SC080 increased MMP-2 activity and degradation of type I collagen. Moreover, coculture with T cells facilitated persistence of myofibroblasts, suggesting a role for T-cell infiltration in myofibroblast persistence in fibrosis. By combining low-dose SC080 with cyclosporine in vivo at post-transplant day 28, partial reversal of obliterative fibrosis was observed at day 42. Thus, modulating MMP activity might reverse established allograft airway fibrosis by regulating inflammation and tissue remodeling.