Growth factor upregulation during obliterative bronchiolitis in the mouse model

Lymphocyte Depleting and Modulating Therapies for Chronic Lung Allograft Dysfunction

Chronic lung rejection, also called chronic lung allograft dysfunction (CLAD), remains the major hurdle limiting long-term survival after lung transplantation, and limited therapeutic options are available to slow the progressive decline in lung function. Most interventions are only temporarily effective in stabilizing the loss of or modestly improving lung function, with disease progression resuming over time in the majority of patients. Therefore, identification of effective treatments that prevent the onset or halt progression of CLAD is urgently needed. As a key effector cell in its pathophysiology, lymphocytes have been considered a therapeutic target in CLAD. The aim of this review is to evaluate the use and efficacy of lymphocyte depleting and immunomodulating therapies in progressive CLAD beyond usual maintenance immunosuppressive strategies. Modalities used include anti-thymocyte globulin, alemtuzumab, methotrexate, cyclophosphamide, total lymphoid irradiation, and extracorporeal photopheresis, and to explore possible future strategies. When considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin and total lymphoid irradiation appear to offer the best treatment options currently available for progressive CLAD patients. SIGNIFICANCE STATEMENT: Effective treatments to prevent the onset and progression of chronic lung rejection after lung transplantation are still a major shortcoming. Based on existing data to date, considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin, and total lymphoid irradiation are currently the most viable second-line treatment options. However, it is important to note that interpretation of most results is hampered by the lack of randomized controlled trials.

Antifibrotic drugs in lung transplantation and chronic lung allograft dysfunction: a review

This review aims to provide an overview of pre-transplant antifibrotic therapy on peri-transplant outcomes and to address the possible role of antifibrotics in lung transplant recipients with chronic lung allograft dysfunction.Lung transplantation is an established treatment modality for patients with various end-stage lung diseases, of which idiopathic pulmonary fibrosis and other progressive fibrosing interstitial lung diseases are growing indications. Theoretically, widespread use of antifibrotics prior to lung transplantation may increase the risk of bronchial anastomotic complications and impaired wound healing.Long-term graft and patient survival are still hampered by development of chronic lung allograft dysfunction, on which antifibrotics may have a beneficial impact.Antifibrotics until the moment of lung transplantation proved to be safe, without increasing peri-transplant complications. Currently, best practice is to continue antifibrotics until time of transplantation. In a large multicentre randomised trial, pirfenidone did not appear to have a beneficial effect on lung function decline in established bronchiolitis obliterans syndrome. The results of antifibrotic therapy in restrictive allograft syndrome are eagerly awaited, but nonrandomised data from small case reports/series are promising.

Early Immune Response to Acute Gastric Fluid Aspiration in a Rat Model of Lung Transplantation

OBJECTIVES

Chronic aspiration of gastric fluid contents can decrease long-term survival of pulmonary transplants due to development of obliterative bronchiolitis. However, little is known about the early immune response and the cascade of events involved in the development of obliterative bronchiolitis.

MATERIALS AND METHODS

We utilized a rat orthotopic pulmonary transplant model and a single aspiration of either gastric fluid or normal saline to investigate the histologic, cellular, and cytokine changes associated with an acute gastric fluid aspiration event compared with normal saline at 2 and 10 days after aspiration.

RESULTS

Our observations included a decrease in pulmonary compliance and increased airway inflammation and acute rejection of the transplanted lung, as well as increases in macrophages, granulocytes, and proinflammatory cytokines such as interleukin 1β, transforming growth factor β1 and β2, and tumor necrosis factor α in bronchoalveolar lavage fluid from the transplanted lung of gastric fluid-aspirated rats compared with normal saline-aspirated rats.

CONCLUSIONS

The acute inflammatory response observed in the present study is consistent with changes found in chronic models of aspiration-associated injury and suggests a potentially important role for mast cells in the development of obliterative bronchiolitis.

The activity of nintedanib in an animal model of allogenic left lung transplantation resembling aspects of allograft rejection

AIM OF THE STUDY

The prevention and treatment of chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx) remain unsatisfactory. Growth factors may play an important role in the development of CLAD. This study evaluated the effects of nintedanib, a receptor tyrosine kinase inhibitor, in the treatment of CLAD after experimental LTx.

MATERIALS AND METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to evaluate the effect of nintedanib (50 mg/kg per day) on the development of CLAD. Therapy with nintedanib began 2 days before LTx and ended on postoperative day (POD) 20 (n = 6) or 60 (n = 6). Nontreated animals who underwent LTx (n = 12) were used as controls, whereas naïve lungs (n = 24) served as reference for physiological healthy organs without transplantation damage or medical effects. Acute and chronic rejection were evaluated on POD 20 and 60, respectively.

RESULTS

Immunohistologic analysis showed a decrease in growth factors/receptors on POD 60 (nintedanib-treated vs. nontreated controls: platelet-derived growth factor (PDGF) A: [P ≤ 0.001]; PDGF receptor-α: [P ≤ 0.001]; vascular endothelial growth factor (VEGF) A: [P ≤ 0.001]; VEGF receptor-2: [P ≤ 0.001]). However, no reductions in fibrotic changes were observed in nintedanib-treated allografts compared with nontreated allografts. Although nintedanib treatment started before LTx none of the animals showed impaired wound healing. No dehiscence of the sutures of the bronchus, vessels or skin, or stenosis of the bronchus was found.

CONCLUSION

In conclusion, while nintedanib reduced the expression of growth factors/receptors in a rat LTx model, a reduction in fibrotic alterations was not observed at POD 60.

Revascularization of the graft in obliterative bronchiolitis after heterotopic tracheal transplantation

Obliterative bronchiolitis is the principal long-term problem for lung transplant patients. One of the simplest and most reproducible animal models of obliterative bronchiolitis is heterotopic tracheal transplantation in subcutaneous tissue, where the graft is not primarily vascularized. We demonstrate here the rapid graft revascularization and the kinetics of expression of its angiogenic and lymphatic factors. We performed iso- and allotracheal transplantations harvested on day 0-21. The number of functional blood vessels, quantified after intravenous biotinylated dextran administration, increased from D0 (0 for both iso- and allografts) to D21 (44 ± 8 vessels/mm(2) in isografts and 22 ± 3 in allografts, P < 0.001 for both vs. D0). VEGF mRNA expression assessed by qPCR peaked on D1 (4.3-fold increase in isografts and 4.0-fold in allografts, P < 0.0001 for both vs. D0), but receded thereafter. Angiopoietin-1, involved in the maturation of the neoformed vessels, increased later on, by 6.2-fold (P < 0.05) in isografts and 11.5-fold in allografts (P < 0.001) by D21, and angiopoietin-2 by 7.8-fold in isografts (P < 0.05) and 13.8-fold in allografts (P < 0.01). Although always present in the iso- and allografts, there were significantly more and larger LYVE1(+) lymphatic vessels at D21 in allografts than in isografts. Thus, we demonstrate that tracheal grafts are rapidly revascularized by functional blood and lymphatic vessels, due to early VEGF and subsequent angiopoietins expression, which is a new advantage of this model, in addition to its ease of use, reproducibility, and viability in the absence of immunosuppressive treatment.

Cytokine mediated tissue fibrosis

Acute inflammation is a recognised part of normal wound healing. However, when inflammation fails to resolve and a chronic inflammatory response is established this process can become dysregulated resulting in pathological wound repair, accumulation of permanent fibrotic scar tissue at the site of injury and the failure to return the tissue to normal function. Fibrosis can affect any organ including the lung, skin, heart, kidney and liver and it is estimated that 45% of deaths in the western world can now be attributed to diseases where fibrosis plays a major aetiological role. In this review we examine the evidence that cytokines play a vital role in the acute and chronic inflammatory responses that drive fibrosis in injured tissues. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

TNFα from classically activated macrophages accentuates epithelial to mesenchymal transition in obliterative bronchiolitis

Bronchiolitis obliterans syndrome is characterized by fibrotic obliteration of small airways which severely impairs graft function and survival after lung transplantation. Bronchial epithelial cells from the transplanted lung can undergo epithelial to mesenchymal transition and this can be accentuated by activated macrophages. Macrophages demonstrate significant plasticity and change phenotype in response to their microenvironment. In this study we aimed to identify secretory products from macrophages that might be therapeutic targets for limiting the inflammatory accentuation of epithelial to mesenchymal transition in bronchiolitis obliterans syndrome. TNFα, IL-1β and IL-8 are elevated in bronchoalveolar lavage from lung transplant patients prior to diagnosis of bronchiolitis obliterans syndrome. Classically activated macrophages secrete more TNFα and IL-1β than alternatively activated macrophages and dramatically accentuate TGF-β1-driven epithelial to mesenchymal transition in bronchial epithelial cells isolated from lung transplant patients. Blocking TNFα, but not IL-1β, inhibits the accentuation of epithelial to mesenchymal transition. In a pilot unblinded therapeutic intervention in five patients with progressive bronchiolitis obliterans syndrome, anti-TNFα treatment improved forced expiratory volume in 1 second and 6-min walk distances in four patients. Our data identify TNFα as a potential new therapeutic target in bronchiolitis obliterans syndrome deserving of a randomized placebo controlled clinical trial.

Aqueous fraction of Sauropus androgynus might be responsible for bronchiolitis obliterans

BACKGROUND AND OBJECTIVE

Bronchiolitis obliterans (BO) has been reported to develop following ingestion of Sauropus androgynus (SA), a leafy shrub distributed in Southeast Asia. Little is known about direct effects of SA on airway resident cells or haematopoietic cells in vitro. Identification of the SA component responsible for the development of BO would be an important key to elucidate its mechanism. We sought to elucidate the direct effects of SA on airway resident cells or haematopoietic cells and identify the SA element responsible for the pathogenesis of BO.

METHODS

SA dry powder was partitioned into fractions by solvent extraction. Human and murine monocytic cells, epithelial cells and endothelial cells were cultured with SA solution or fractions eluted from SA. We also investigated the effect of SA in vivo using a murine BO syndrome (BOS) model.

RESULTS

The aqueous fraction of SA induced significant increases of inflammatory cytokine and chemokine production from monocytic lineage cells. This fraction also induced significant apoptosis of endothelial cells and enhanced intraluminal obstructive fibrosis in allogeneic trachea allograft in the murine BOS model. We found individual differences in tumour necrosis factor α (TNF-α) production from monocytes of healthy controls stimulated by this aqueous fraction of SA, whereas it induced high-level TNF-α production from monocytes of patients with SA-induced BO.

CONCLUSIONS

These results suggest that an aqueous fraction of SA may be responsible for the pathogenesis of BO.

Tumor necrosis factor alpha inhibitors as immunomodulatory antirejection agents after intestinal transplantation

We reported the successful administration of infliximab for late-onset OKT3-resistant rejection in two patients, who presented persistent ulcerative inflammation of the ileal graft after intestinal transplantation (ITX). Based on this experience, the present study demonstrated our long-term experience with infliximab for different types of rejection-related and inflammatory allograft alterations. Infliximab administration (5 mg/kg body weight (BW)) was initiated at a mean of 18.2 ± 14.1 months after transplantation. The number of administrations per patient averaged 8.4 ± 6.7. Repeat dosing was timed according to clinical signs and graft histology in addition to serum-levels of tumor necrosis factor alpha (TNFα), lipopolysaccharide binding protein (LBP) and C-reactive protein (CRP). Infliximab was successful in the following patients: patients with late-onset OKT3- and steroid-refractory rejection who presented persistent ulcerative alterations of the ileal graft (n = 5), patients with ulcerative ileitis/anastomositis, who did not show typical histological rejection signs (n = 2), and one patient with early-onset OKT3-resistant rejection. Infliximab was not successful in one patient with early-onset OKT3-resistant rejection that was accompanied by treatment-refractory humoral rejection. In conclusion, infliximab can expand therapeutic options for late-onset OKT3- and steroid-refractory rejection and chronic inflammatory graft alterations in intestinal allograft recipients.

Low-molecular-weight heparins do not modify obliterative airway disease in rat tracheal allografts

Immunosuppressive and antiproliferative effects of heparin may be beneficial in the field of solid organ transplantation. The aim of this study was to examine the effect of low-molecular-weight heparin (LMWH) compounds on the development of obliterative airway disease (OAD) in the rat tracheal transplant model. Allogenic heterotopic tracheal transplantations were performed from Brown-Norway into Lewis rats. Recipients were treated either with nadroparin, enoxaparin, parnaparin, or vehicle from day 0 until harvesting at day 7 or 21. Graft rejection was morphometrically assessed to determine the extent of luminal obliteration end epithelial necrosis. All tracheal grafts harvested at day 7 demonstrated nearly equivalent degree of luminal obstruction regardless of treatment regimen. Likewise, at day 21 the extent of airway narrowing and the degree of inflammatory cell infiltration were similar among the groups. Moreover, loss of airway epithelium was not prevented by LMWH treatments. Finally, intragraft mRNA expression for transforming growth factor-β1 and platelet-derived growth factor-A, interleukin-2, interferon-γ, and monocyte chemoattractant protein-1 did not differ between the groups. In contrast with findings in other animal models, treatment with LMWH preparations did not modify the development of OAD in rat tracheal allografts.

Overexpression of transforming growth factor (TGF)-beta1 and TGF-beta3 genes in lung of toxic-inhaled patients

Iraq frequently used toxic inhalants during the war with Iran, exposing over 100,000 people to chemical reagents. Bronchiolitis obliterans (BO) is a major pulmonary disease caused by exposure to harmful gases. Recently defect in clearance of apoptotic cells (efferocytosis) has been suggested as a mechanism that leads to several lung diseases. Transforming growth factor (TGF)-beta, a cytokine produced by efferocytotic macrophages, suppresses the inflammation and enhances the regeneration of tissue. In this study, the authors compared the expression of these 3 isoforms of TGF-beta at mRNA level in lung biopsies of Iranian victims of chemical gases with lung biopsies of control healthy volunteers. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) technique was used to examine the expression level of TGF-beta isoforms using glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene as an internal control. The results indicated that that levels of TGF-beta1 and TGF-beta3 mRNAs were significantly higher in chemical gas-injured patients than noninjured group (P < .05). Therefore, the authors speculate that TGF-beta1 and TGFbeta3, but not TGF-beta2, secretion is a result of efficient efferocytosis in chemically injured patients, playing a protective role by improving airway remodeling and lung homeostasis in this group. These properties of TGF-beta are consistent with long-time survival of chemical-injured people suffering from BO.

Lipid raft facilitated ligation of K-alpha1-tubulin by specific antibodies on epithelial cells: Role in pathogenesis of chronic rejection following human lung transplantation

Long term function of human lung allografts is hindered by development of chronic rejection manifested as Bronchiolitis Obliterans Syndrome (BOS). We have previously identified the development of antibodies (Abs) following lung transplantation to K-alpha1-tubulin (KAT), an epithelial surface gap junction cytoskeletal protein, in patients who develop BOS. However, the biochemical and molecular basis of the interactions and signaling cascades mediated by KAT Abs are yet to be defined. In this report, we investigated the biophysical basis of the epithelial cell membrane surface interaction between KAT and its specific Abs. Towards this, we analyzed the role of the lipid raft-domains in the membrane interactions which lead to cell signaling and ultimately increased growth factor expression. Normal human bronchial epithelial (NHBE) cells, upon specific ligation with Abs to KAT obtained either from the serum of BOS(+) patients or monoclonal KAT Abs, resulted in upregulation of growth factors VEGF, PDGF, and bFGF (6.4+/-1.1-, 3.2+/-0.9-, and 3.4+/-1.1-fold increase, respectively) all of which are important in the pathogenesis of BOS. To define the role for lipid raft in augmenting surface interactions, we analyzed the changes in the growth factor expression pattern upon depletion and enrichment with lipid raft following the ligation of the epithelial cell membranes with Abs specific for KAT. NHBE cells cultured in the presence of beta-methyl cyclodextran (betaMCD) had significantly reduced growth factor expression (1.3+/-0.3, vs betaMCD untreated being 6.4+/-1.1-fold increase) upon stimulation with KAT Abs. Depletion of cholesterol on NHBE cells upon treatment with betaMCD also resulted in decreased partitioning of caveolin in the membrane fraction indicating a decrease in raft-domains. In conclusion, our results demonstrate an important role for lipid raft-mediated ligation of Abs to KAT on the epithelial cell membrane, which results in the upregulation of growth factor cascades involved in the pathogenesis of BOS following human lung transplantation.

Obliterative airway remodelling in transplanted and non-transplanted lungs

Obliterative airway remodelling is a morphological sequence in a variety of pulmonary diseases. Notably, bronchiolitis obliterans represents one of the key complications of lung transplantation, induced by (immigrating) myofibroblasts. A comparative expression analysis of obliterative airway remodelling in transplanted and non-transplanted patients has not been reported so far. Obliterated and unremodelled airways from explanted lungs (n = 19) from patients suffering from chronic allograft dysfunction, infection, graft-versus-host disease and toxic exposure were isolated by laser-assisted microdissection. Airways from lung allografts harvested shortly before and after transplantation (n = 4) as well as fibroblastic foci from lungs with interstitial pulmonary fibrosis (n = 4) served as references. Pre-amplified cDNA was analysed by quantitative real-time RT-PCR for expression of fibrosis, inflammation and apoptosis-associated genes. Composition of infiltrating cells and protein expression were assessed by conventional histology and immunohistochemistry. Bronchiolitis obliterans in transplanted patients showed a significant increase of BMP-7 expression (p = 0.0141 compared with controls), while TGF-beta1 and FGF-2 as well as BMP-4 and BMP-7 were up-regulated in fibroblastic foci in interstitial pulmonary fibrosis (p < 0.0424 compared with controls). Regarding other fibrosis-associated genes (BMP-6, SMAD-3, CASP-3 and CASP-9, FASLG, NF-KB1, IL-1 and IL-2) as well as cellularity and cellular composition, no significant differences between obliterative airway remodelling in transplanted and non-transplanted patients could be shown. Obliterative airway remodelling in lung allografts and in non-transplanted patients share many morphological and genetic traits. BMPs, especially BMP-7, warrant further investigation as possible markers for the aggravation of airway remodelling.

Bronchiolitis obliterans syndrome after allogeneic hematopoietic stem cell transplantation-an increasingly recognized manifestation of chronic graft-versus-host disease

Bronchiolitis obliterans syndrome (BOS) is a progressive, insidious, and often fatal lung alloreaction that can occur following allogeneic hematopoietic stem cell transplantation (HSCT) or allogeneic lung transplantation. Current estimates in the literature suggest that approximately 2% to 3% of all allogeneic HSCT recipients and 6% of patients who develop chronic graft-versus-host disease (cGVHD) will develop this syndrome. However, based on newer data it is likely that the true incidence of BOS is higher. Unfortunately, the survival and treatment of patients with BOS after HSCT has not improved over the last 20 years. Attempts at clinical trials have been hindered by the lack of uniform diagnostic criteria and inability to detect the syndrome at a reversible stage in its natural history. Recently, the National Institutes of Health (NIH) consensus project for criteria in cGVHD has made recommendations regarding the diagnosis of BOS and monitoring of lung disease among long-term survivors. Although a rare and poorly understood manifestation of cGVHD, BOS occurs commonly after lung transplantation and is similar in pathology, clinical presentation, radiographic presentation, and presumed immunologic pathogenesis. This review describes the current understanding of the epidemiology and pathogenesis of BOS and presents information on evaluations and therapies for patients with BOS after HSCT.

PLATELET-DERIVED GROWTH FACTOR, TRANSFORMING GROWTH FACTOR-β, AND CONNECTIVE TISSUE GROWTH FACTOR IN A PORCINE BRONCHIAL MODEL OF OBLITERATIVE BRONCHIOLITIS

The expression of platelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta, and connective tissue growth factor (CTGF) and the effect of imatinib, an agent inhibiting PDGF receptors, were assessed in a porcine bronchial transplantation model of obliterative bronchiolitis (OB). Up-regulation of PDGF-A, PDGF receptors alpha and beta, and TGF-beta expression occurred in allografts, whereas PDGF-B and CTGF expression was similar in allo- and autografts. Imatinib modified the inflammatory responses and expression patterns of PDGF-A and PDGF receptors. This study further confirms PDGF and TGF-beta as mediators of OB and supports the concept of the importance of the pathways signaled through PDGF receptors in post-transplant OB.

Airway epithelial versus immune cell Stat1 function for innate defense against respiratory viral infection

The epithelial surface is often proposed to actively participate in host defense, but evidence that this is the case remains circumstantial. Similarly, respiratory paramyxoviral infections are a leading cause of serious respiratory disease, but the basis for host defense against severe illness is uncertain. Here we use a common mouse paramyxovirus (Sendai virus) to show that a prominent early event in respiratory paramyxoviral infection is activation of the IFN-signaling protein Stat1 in airway epithelial cells. Furthermore, Stat1-/- mice developed illness that resembled severe paramyxoviral respiratory infection in humans and was characterized by increased viral replication and neutrophilic inflammation in concert with overproduction of TNF-alpha and neutrophil chemokine CXCL2. Poor control of viral replication as well as TNF-alpha and CXCL2 overproduction were both mimicked by infection of Stat1-/- airway epithelial cells in culture. TNF-alpha drives the CXCL2 response, because it can be reversed by TNF-alpha blockade in vitro and in vivo. These findings pointed to an epithelial defect in Stat1-/- mice. Indeed, we next demonstrated that Stat1-/- mice that were reconstituted with wild-type bone marrow were still susceptible to infection with Sendai virus, whereas wild-type mice that received Stat1-/- bone marrow retained resistance to infection. The susceptible epithelial Stat1-/- chimeric mice also exhibited increased viral replication as well as excessive neutrophils, CXCL2, and TNF-alpha in the airspace. These findings provide some of the most definitive evidence to date for the critical role of barrier epithelial cells in innate immunity to common pathogens, particularly in controlling viral replication.

Comparative efficacies of albendazole and the Chinese herbal medicine long-dan-xie-gan-tan, used alone or in combination, in the treatment of experimental eosinophilic meningitis induced by Angiostrongylus cantonensis

Angiostrongylus cantonensis, the rat lungworm, is the principal cause of human eosinophilic meningitis or meningoencephalitis world-wide. In the present study, the efficacies of early-stage treatment with the Chinese herbal medicine long-dan-xie-gan-tan (LDXGT) and albendazole, used alone or in combination, were evaluated in BALB/c mice with A. cantonensis-induced dysfunction of the blood-central-nervous-system barrier and eosinophilic meningo-encephalitis. Indicators of the therapeutic effect included worm recovery, histopathological scores for the meningitis, assays of tissue-type plasminogen activator (PA), urokinase-type PA and matrix metalloproteinase-9 (MMP-9) in the brain, the ratio between albumin concentrations in the cerebrospinal fluid (CSF) and serum, and counts of eosinophils in the CSF. Combined treatment with albendazole and LDXGT gave better results than monotherapy based on either drug, apparently inhibiting eosinophilic meningitis via antagonists of the PA/MMP-9 system. LDXGT may have a therapeutic role in reducing inflammatory reaction in the subarachnoid space. Monotherapy with such an anti-inflammatory drug may relieve the symptoms of mild infection and the host's immune responses to A. cantonensis larvae. In severe infection, however, co-therapy with an anthelmintic (to kill the larvae) and an anti-inflammatory agent (to provide symptomatic relief) is probably a better approach. The therapeutic strategy should be tailored to the severity of the illness and the numbers of eosinophils in the CSF.

Chronic aspiration of gastric fluid induces the development of obliterative bronchiolitis in rat lung transplants

Long-term survival of a pulmonary allograft is currently hampered by obliterative bronchiolitis (OB), a form of chronic rejection that is unique to lung transplantation. While tracheobronchial aspiration from gastroesophageal reflux disease (GERD) has clinically been associated with OB, no experimental model exists to investigate this problem. Using a WKY-to-F344 rat orthotopic left lung transplant model, the effects of chronic aspiration on pulmonary allograft were evaluated. Recipients received cyclosporine with or without 8 weekly aspirations of gastric fluid into the allograft. Six (66.7%) of 9 allografts with aspiration demonstrated bronchioles with surrounding monocytic infiltrates, fibrosis and loss of normal lumen anatomy, consistent with the development of OB. In contrast, none of the allografts without aspiration (n = 10) demonstrated these findings (p = 0.002). Of the grafts examined grossly, 83% of the allografts with chronic aspiration but only 20% without aspiration appeared consolidated (p = 0.013). Aspiration was associated with increased levels of IL-1 alpha, IL-1 beta, IL-6, IL-10, TNF-alpha and TGF-beta in BAL and of IL-1 alpha, IL-4 and GM-CSF in serum. This study provides experimental evidence linking chronic aspiration to the development of OB and suggests that strategies aimed at preventing aspiration-related injuries might improve outcomes in clinical lung transplantation.

Pulmonary hypertension in patients with bronchiolitis obliterans syndrome listed for retransplantation

Bronchiolitis Obliterans Syndrome (BOS) is a major cause of morbidity and mortality post-lung transplantation. Pulmonary hypertension (PH) may complicate the course of patients with advanced lung disease. We sought to characterize the prevalence of PH in patients with BOS. We performed a retrospective analysis of lung transplant recipients with BOS relisted for transplantation with the United Network for Organ Sharing (UNOS). Right heart catheterization (RHC) data were required for analysis. Eighty patients with BOS qualified for the analysis. PH was present in 32.5% of patients with an average mean pulmonary artery pressure (mPAP) of 32.3 mmHg (range: 26-63 mmHg). Of these, 42.3% had an elevated pulmonary capillary wedge pressure. There was no difference in PH prevalence between bilateral (26.5%) and single lung recipients (41.9%), nor did it differ by primary disease. There was no correlation between pulmonary function data and the presence or severity of PH. There was no difference in oxygen requirements or 6-min walk distance between patients with and without PH. This is the first report of PH in patients with BOS. Many of these cases occur in association with diastolic dysfunction. Although no impact on functional status or outcomes was discerned, further studies appear warranted.

Chronic aspiration of gastric fluid induces the development of obliterative bronchiolitis in rat lung transplants

Long-term survival of a pulmonary allograft is currently hampered by obliterative bronchiolitis (OB), a form of chronic rejection that is unique to lung transplantation. While tracheobronchial aspiration from gastroesophageal reflux disease (GERD) has clinically been associated with OB, no experimental model exists to investigate this problem. Using a WKY-to-F344 rat orthotopic left lung transplant model, the effects of chronic aspiration on pulmonary allograft were evaluated. Recipients received cyclosporine with or without 8 weekly aspirations of gastric fluid into the allograft. Six (66.7%) of 9 allografts with aspiration demonstrated bronchioles with surrounding monocytic infiltrates, fibrosis and loss of normal lumen anatomy, consistent with the development of OB. In contrast, none of the allografts without aspiration (n = 10) demonstrated these findings (p = 0.002). Of the grafts examined grossly, 83% of the allografts with chronic aspiration but only 20% without aspiration appeared consolidated (p = 0.013). Aspiration was associated with increased levels of IL-1 alpha, IL-1 beta, IL-6, IL-10, TNF-alpha and TGF-beta in BAL and of IL-1 alpha, IL-4 and GM-CSF in serum. This study provides experimental evidence linking chronic aspiration to the development of OB and suggests that strategies aimed at preventing aspiration-related injuries might improve outcomes in clinical lung transplantation.

De novo production of K-alpha1 tubulin-specific antibodies: role in chronic lung allograft rejection

Lung transplantation is the treatment option for a variety of end-stage pulmonary diseases. Posttransplant development of Abs against donor HLA and non-HLA Ags have been associated with acute and chronic rejection of transplanted organs. Development of bronchiolitis obliterans syndrome (BOS) following lung transplantation has been correlated with de novo production of anti-donor-HLA Abs. However, only a portion of the patients with BOS demonstrate detectable anti-donor-HLA Abs. Airway epithelium is considered as a major target for lung allograft rejection. In this study we demonstrate that many BOS(+) patients (12 of 36) develop Abs reactive to epithelial cell Ag that are distinct from HLA. Furthermore, de novo production of antiepithelial cell Ab precedes clinical onset of BOS. N-terminal sequencing and blastx analysis as well as blocking with K-alpha1 tubulin-specific Ab identified the epithelial Ag as K-alpha1 tubulin. Binding of the de novo-produced anti-K-alpha1 tubulin Abs to the airway epithelial cells resulted in the increased expression of transcription factors (TCF5 and c-Myc), leading to increased expression of fibrogenic growth factors, activation of cell cycle signaling, and fibroproliferation, the central events in immunopathogenesis of BOS following human lung transplantation.

Late treatment with angiotensin-converting enzyme inhibitors plus endothelin receptor antagonists ameliorates rat tracheal allograft rejection

Inhibition of the renin-angiotensin and endothelin (ET) systems prevents the development of obliterative airway disease (OAD) in rat tracheal allografts. In this study, we assessed whether these therapeutic approaches are effective even when the same were started after signs of OAD were already manifest. Rat tracheas were heterotopically transplanted from Brown-Norway donors into Brown-Norway or Lewis recipients. Allograft recipients received bosentan, ramipril, bosentan plus ramipril or vehicle from day 10 to 24. Untreated allografts and isografts were harvested at day 10 or 24. In tracheal grafts, morphometric studies together with molecular analysis by real-time PCR were performed. Fibroproliferative process in untreated tracheal allografts but not in isografts started already at day 10. Neither bosentan nor ramipril treatment alone as monotherapy could modify the development of OAD when administered only between day 10 and day 24. By contrast, the combination treatment of bosentan and ramipril ameliorated airway obstruction by day 24, which was accompanied by reduced mRNA expression of intragraft transforming growth factor-beta1 and platelet-derived growth factor-A and -B chains. Only the combined blockade with angiotensin-converting enzyme inhibitors and ET receptor antagonists can reduce the progression of OAD in this model if the treatment is initiated late in the disease course.

Bronchiolitis obliterans syndrome (BOS), bronchiolitis obliterans organizing pneumonia (BOOP), and other late-onset noninfectious pulmonary complications following allogeneic hematopoietic stem cell transplantation

Pulmonary dysfunction is a significant complication following allogeneic hematopoietic stem cell transplantation (HSCT), and is associated with significant morbidity and mortality. Effective antimicrobial prophylaxis and treatment strategies have increased the incidence of noninfectious lung injury, which can occur in the early posttransplant period or in the months and years that follow. Late-onset noninfectious pulmonary complications are frequently encountered, but diagnostic criteria and terminology for these disorders can be confusing and therapeutic approaches are suboptimal. As a consequence, inaccurate diagnosis of these conditions may hamper the appropriate data collection, enrollment into clinical trials, and appropriate patient care. The purpose of this review is to clarify the pathogenesis and diagnostic criteria of representative conditions, such as bronchiolitis obliterans syndrome and bronchiolitis obliterans organizing pneumonia, and to discuss the appropriate diagnostic strategies and treatment options.

Early growth response gene-1 promotes airway allograft rejection

Chronic airway rejection, characterized by lymphocytic bronchitis, epithelial cell damage, and obliterative bronchiolitis (OB), limits long-term survival after lung transplantation. The transcription factor early growth response gene-1 (Egr-1) induces diverse inflammatory mediators, some involved in OB pathogenesis. An orthotopic mouse tracheal transplant model was used to determine whether Egr-1 promotes development of airway allograft rejection. Significantly higher Egr-1 mRNA levels were seen in allografts (3.2-fold increase vs. isografts, P = 0.012). Allografts revealed thickening of epithelial and subepithelial airway layers (51 +/- 4% luminal encroachment for allografts vs. 20 +/- 3% for isografts, P < 0.0001) marked by significant lymphocytic infiltration. Absence of the Egr-1 gene in donor (but not recipient) tissue resulted in significant reduction in luminal narrowing (34 +/- 4%, P = 0.0001) with corresponding diminution of T cell infiltration. Egr-1 null allografts exhibited a striking reduction in inducible nitric oxide synthase (iNOS) expression. Effector cytokines previously implicated in OB pathogenesis with known Egr-1 promoter motifs (IL-1beta and JE/monocyte chemoattractant protein-1) were reduced in Egr-1 null allografts. These data suggest a paradigm wherein local induction of Egr-1 in tracheal allografts drives expression of inflammatory mediators responsible for lymphocyte recruitment and tissue destruction characteristic of airway rejection.

Sequential gene expression profiling in lung transplant recipients with chronic rejection

STUDY OBJECTIVES

Chronic allograft rejection is the leading cause of morbidity and mortality for long-term survivors of lung transplantation. Previous studies have implicated only isolated genes in the development of chronic rejection and have not examined multiple pathways in an individual concurrently. Using microarray technology, we identified and compared gene expression profiling in lung transplant recipients with and without chronic rejection, and follow sequential expression of genes differentially expressed between the two groups.

DESIGN

Prospective, cohort study.

SETTING

Single lung transplant center.

PATIENTS OR PARTICIPANTS

Eleven transplant recipients with chronic rejection were matched with 9 control transplant recipients.

INTERVENTIONS

All recipients underwent surveillance bronchoscopies at predetermined times to rule out infection and/or acute rejection. Gene expression profiling was obtained from hybridizing BAL fluid cell RNA to a 96-gene microarray.

MEASUREMENTS AND RESULTS

Fifteen genes were found to be significantly differentially expressed between the two patient groups, and they are involved in inflammatory, fibrotic, and apoptotic pathways. Temporal expression of the significant genes demonstrated a change in their levels at the onset of chronic rejection, with normalization to prerejection levels as rejection continued.

CONCLUSIONS

We conclude that microarray technology is valuable in studying the mechanism of chronic lung rejection, and the expression of genes in multiple pathways is elevated in patients with chronic lung rejection.

Obligatory role for interleukin-13 in obstructive lesion development in airway allografts

The pathogenesis of bronchiolitis obliterans (BO), a common and devastating obliterative disorder of small airways following lung transplantation, remains poorly understood. Lesions are characterized in their early stages by lymphocyte influx that evolves into dense fibrotic infiltrates. Airway specimens taken from patients with histological BO revealed infiltrating myofibroblasts, which strongly expressed the signaling chain of the high affinity interleukin-13 (IL-13) receptor IL-13Ralpha1. Because IL-13 has proinflammatory and profibrotic actions, a contributory role for IL-13 in BO development was examined using murine models of orthotopic and heterotopic tracheal transplantation. Compared with airway isografts, allografts exhibited a significant increase in relative IL-13 mRNA and protein levels. Allogeneic tracheas transplanted into IL-13-deficient mice were protected from BO in both transplant models. Flow cytometric analysis of orthotopic transplant tissue digests revealed markedly fewer infiltrating mononuclear phagocytes and CD3(+) T lymphocytes in IL-13-deficient recipients. Furthermore, protection from luminal obliteration, collagen deposition, and myofibroblast infiltration was observed in heterotopic airways transplanted into the IL-13(-/-) recipients. Transforming growth factor-beta1 expression was significantly decreased in tracheal allografts into IL-13(-/-) recipients, compared to wild-type counterparts. These human and murine data implicate IL-13 as a critical effector cytokine driving cellular recruitment and subsequent fibrosis in clinical and ex-perimental BO.

Role of platelet-derived growth factor and vascular endothelial growth factor in obliterative airway disease

RATIONALE

Platelet-derived growth factor (PDGF) is an important smooth muscle cell mitogen, and vascular endothelial growth factor (VEGF) is a known angiogenic and proinflammatory growth factor. We hypothesized that specific therapy aimed at these growth factors might inhibit the development of experimental obliterative airway disease (OAD).

METHODS

In fully mismatched rat tracheal allografts, we used imatinib and PTK/ZK, either alone or in combination, to block PDGF and VEGF receptor protein tyrosine kinase (RTK) action, respectively. Prophylaxis was initiated at the time of transplantation. Early treatment was commenced on Day 7 during the inflammatory phase and late treatment on Day 14 during the fibroproliferative phase of OAD. No immunosuppression was administered.

MEASUREMENTS AND MAIN RESULTS

Prophylaxis with either PTK/ZK or imatinib alone significantly reduced OAD, and combined prophylaxis completely prevented its development. Early treatment with PTK/ZK and imatinib also effectively reduced the development of OAD. Late treatment failed to show significant efficacy. Blocking VEGF RTK action with PTK/ZK reduced the activation of allograft blood vessels and the number of lymph vessels in the allograft airway wall, and significantly diminished allograft inflammation, whereas PDGF blockade with imatinib inhibited the growth of smooth muscle cells in the proliferating lesion.

CONCLUSIONS

Combined prophylactic PDGF and VEGF RTK blockade completely prevents the development of OAD. Also, when early treatment with PTK/ZK and imatinib is commenced during the inflammatory phase of OAD development, it significantly attenuates the development of tracheal occlusion, suggesting that these drugs could potentially be used to treat bronchiolitis obliterans syndrome in its early phase.

Immune Cell Infiltration and Broncovascular Remodeling After Nitric Acid Nasal Instillation in a Mouse Bronchiolitis Obliterans Model

Immune cell airway infiltration and the bronchovascular remodeling process have shown to be promising in the understanding of bronchiolitis obliterans (BO) pathogenesis. In this study we sought to validate the importance of immune cells, whether diffusely distributed or forming lymphoid follicles, collagen density, and vascular factors. Eight weeks after a single nitric acid (NA) nasal instillation, lung changes were characterized by lumen distortion, epithelial layer folding, reduction or total obliteration of terminal bronchiole (TB) lumen, and wall thickness increase. The morphologic changes in the TB and TA (terminal artery) lumen coincide with the measurement difference in the three groups. The TB diameter and lumen were significantly decreased in BO when compared with non-BO lungs (0.76 +/- 0.05 microm vs. 0.81 +/- 0.05 microm and 12,286.13 +/- 378.83 microm vs. 18,182.27 +/- 5,593.98 microm, p = 0.05 and p = 0.01, respectively). Equally significant was the increase in TB thickness in BO when compared with the non-BO group (201.72 +/- 35.75 microm vs. 149.75 +/- 40.61 microm, p = 0.007). The morphologic changes in immune cells seen in TB, TA, and bronchus-associated lymphoid tissue (BALT) also coincide with the quantification differences observed in the three groups. We concluded that immune cell infiltration and collagen/vascular remodeling are related to the spectrum of histologic changes in a BO nasal-induced model in mice and may be an appropriate target for prospective studies of human bronchiolitis.

Integrity of airway epithelium is essential against obliterative airway disease in transplanted rat tracheas

BACKGROUND

The pathogenesis of obliterative bronchiolitis after lung transplantation requires further elucidation. In this study we used rat trachea transplantation to examine the role of epithelium in the progression of obliterative airway disease.

METHODS

Normal and denuded (i.e., epithelium removed) trachea grafts from Lewis (LEW) and Brown Norway (BN) rats were transplanted sub-cutaneously into LEW rats. Viable trachea epithelial cells (to recover epithelium) were seeded into the lumen of some of the denuded tracheas. Grafts were removed at different time-points between 2 days and 8 weeks after transplantation. Histologic analysis was performed to evaluate cellular infiltration of inflammatory cells, loss of epithelium, and obliteration of trachea lumen.

RESULTS

Obliteration was found to occur in trachea transplants after loss of epithelium, caused by rejection in allografts or by enzymatic denudation in isografts. In these situations, fibroblasts started to proliferate and migrate into the lumen in the second week after transplantation. Obliteration could be prevented when epithelial integrity was restored by seeding epithelial cells; no obliteration occurred when denuded trachea isografts were seeded with epithelial cells, whereas non-seeded denuded tracheas were obliterated at Day 6 after transplantation.

CONCLUSIONS

We conclude that integrity of airway epithelium is essential for rat trachea transplants to be safeguarded from obliterative airway disease. For clinical lung transplantation the results of our study suggest that protection of the integrity of airway epithelium may be important in preventing the development of obliterative bronchiolitis.

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.

Impact of TGFβ1 Gene Polymorphisms on Acute and Chronic Rejection in Pediatric Heart Transplant Allografts

BACKGROUND

The aim of this study was to assess the influence of IL-10 and TGFbeta1 gene polymorphisms on the development of acute rejection and coronary disease in pediatric heart transplant recipients.

METHODS

Patients were classified as either Rejectors or Nonrejectors. Coronary artery disease (CAD) was diagnosed by angiography or on macroscopic examination. Genotyping PCR-SSP were performed for IL-10 and TGFbeta1 (codon 10 and 25) in 111 patients. Thirty-nine were Rejectors and 31 developed CAD.

RESULTS

The proportion of IL-10 low-producers was higher in Rejectors than in Nonrejectors (respectively 46% versus 22%, P=0.009). IL-10 gene polymorphism was not associated with CAD. TGFbeta1-codon10-25 high-producers were 92.3% in Rejectors and 75% in Nonrejectors (P=0.026), 93.5% in patients with CAD and 76.2% in patients free from CAD (P=0.037). TGFbeta1-codon25 high-production separately analyzed correlated with CAD (31/31 high-producers in CAD=100% versus 69/80 in noCAD patients=86.2%, P=0.03). TGFbeta1-codon10 gene polymorphisms were not associated with CAD.

CONCLUSION

IL-10 low-producers have an increased risk of acute rejection. High-expressors of TGFbeta1-codon10-25 have an increased risk of acute rejection and CAD, while TGFbeta1-codon25 high-production is associated with coronary disease. Genetic polymorphism may reveal patients at high-risk in whom therapies and monitoring should be adjusted.

Biologics in the treatment of transplant rejection and ischemia/reperfusion injury: new applications for TNFalpha inhibitors?

Tumor necrosis factor (TNF)-alpha inhibitors have proven efficacy in various autoimmune diseases such as Crohn disease, rheumatoid arthritis, psoriasis, and ankylosing spondylitis. Indeed, some TNFalpha inhibitors have already been approved for the management of the inflammatory manifestations associated with Crohn disease and rheumatoid arthritis. These agents are increasingly used for treatment of corticosteroid-resistant graft-versus-host disease after bone marrow transplantation, and case reports have documented their efficacy in treating corticosteroid- and muromonab-resistant rejection after intestinal transplantation. Thus, the potential role of TNFalpha inhibitors in transplantation of other vascularized solid organs is worthy of investigation. Experimental evidence indicates that TNFalpha plays a key role in mediating ischemia/reperfusion (IR) injury after liver, kidney, intestine, heart, lung, and pancreas transplantation. TNFalpha was also identified as a marker cytokine during organ rejection. Single-center studies evaluating the role of TNFalpha inhibitors in kidney transplantation have been initiated but the results are not yet available. TNFalpha is known to be a contributing factor in kidney allograft rejection, and may have value in predicting the onset of steroid-resistant acute rejection after liver transplantation. Experimental and preliminary clinical data have shown that circulating levels of TNFalpha are increased during cardiac graft rejection, and indicate that TNFalpha plays a role in the pathogenesis of acute cardiac allograft rejection. Anti-TNFalpha therapy was shown to prolong cardiac allograft survival when used alone or in combination with other drugs. TNFalpha genotype has been strongly associated with mortality in humans due to acute cell-mediated heart transplant rejection. In addition, there is evidence for a genetic predisposition toward acute rejection after kidney and simultaneous kidney-pancreas transplantation. TNFalpha inhibition has been used successfully as part of an induction therapy for pancreatic islet cell transplantation. Apart from IR injury and acute rejection after lung transplantation, TNFalpha was also found to be involved in the pathoimmunology of obliterative bronchiolitis. In conclusion, a substantial body of experimental evidence and preliminary clinical data suggest that TNFalpha inhibitors may play an important role in solid-organ transplantation, both in the amelioration of IR injury and in the treatment and prevention of acute rejection. Pharmacodynamic monitoring and pharmacogenetic screening may help to identify patients most likely to benefit from TNFalpha blockade. Randomized controlled trials in patients undergoing solid-organ transplantation are needed to further elucidate the clinical value of TNFalpha inhibition.

Chronic aspiration of gastric fluid accelerates pulmonary allograft dysfunction in a rat model of lung transplantation

OBJECTIVE

Emerging clinical evidence suggests that gastroesophageal reflux disease is associated with pulmonary allograft dysfunction. In this study, we used a model of rat lung transplantation to test the hypothesis that chronic aspiration of gastric contents accelerates pulmonary allograft dysfunction.

METHODS

We evaluated the effects of chronic aspiration on pulmonary isografts (strain F344) and pulmonary allografts (strain WKY to strain F344). Chronic aspiration consisted of 0.5 mL/kg of filtered gastric contents injected weekly into the left lung for 4 to 8 weeks beginning 1 week after transplantation. Seven days after the last aspiration, animals were killed, and grafts were evaluated grossly and by histologic and immunochemical analyses, including Masson trichrome staining for collagen and immunostaining for CD68+ and CD8+ cells. Serum cytokine concentrations were determined by bead-based immunoassays or enzyme-linked immunosorbent assay.

RESULTS

Allografts without aspiration (n = 12) demonstrated a relatively normal architecture with diffuse International Society for Heart and Lung Transplantation grade 3 acute rejection; occasional grade 4 rejection was noted. In contrast, allografts with chronic aspiration (n = 7) demonstrated severe grade 4 acute rejection with significant monocyte infiltration, fibrosis, and loss of normal alveolar anatomy. Grossly, 8 (67%) of 12 allografts without aspiration seemed to inflate and perfuse normally, whereas all allografts exposed to chronic aspiration were firm and shrunken, without the ability to ventilate (P = .013; Fisher exact test). Aspiration was associated with increases in graft-infiltrating macrophages and CD8+ T cells and higher levels of serum transforming growth factor beta.

CONCLUSIONS

Chronic aspiration of gastric contents promotes accelerated allograft failure and may promote a profibrotic environment.

Combined donor specific transfusion and anti-CD154 therapy achieves airway allograft tolerance

BACKGROUND

The state of tolerance allows long term graft survival without immunosuppressants. Lung transplantation tolerance has not been consistently achieved in either small or large animal models.

METHODS

The mechanisms and effectiveness of a tolerance induction protocol consisting of donor specific transfusion (DST; day 0) and a short course of co-stimulatory blockade (anti-CD154 antibody; days -7, -4, 0 and +4) were studied in the mouse heterotopic tracheal transplant model of chronic lung rejection. C57BL/6 mice received BALB/c tracheal grafts (day 0) and were treated with DST alone, anti-CD154 alone, the combination (DST/anti-CD154), or no treatment. No non-specific immunosuppressants were used.

RESULTS

DST/anti-CD154 in combination, but neither treatment alone, markedly prolonged the lumen patency and survival (>100 days) of fully histo-incompatible allografts (p<0.05 versus control allografts at every time point studied up to 16 weeks) without immunosuppression. This protocol was donor antigen specific as third party grafts (C3H) were promptly rejected. In addition, DST/anti-CD154 did not result in mixed chimerism but induced transplantation tolerance via a peripheral mechanism(s), which included significantly reduced cytotoxic T cell activity (p<0.001) and a significantly increased percentage of CD4+CD25+ cells (p = 0.03).

CONCLUSIONS

The DST/anti-CD154 protocol successfully induced and maintained long term, donor specific tolerance in the mouse heterotopic airway graft model of chronic lung rejection. This finding may lead us closer to successful tolerance induction in lung transplantation.

Transplant-related bronchiolitis obliterans (BOS) demonstrates unique cytokine profiles compared to toxicant-induced BOS

Bronchiolitis obliterans (BOS - bronchiolitis obliterans syndrome - clinical diagnosis; CBO-histopathologic diagnosis), is a chronic disease process of fibrosis and cellular deposition in airways, complicating long term survival following lung transplantation. BOS is also the result of sporadic toxicant exposure, with airway signs, symptoms, and histology indistinguishable from allograft rejection. This study establishes a transplant BOS model in MHC-mismatched rats and compares their cytokine profiles and histopathology to that of our established toxicant-induced BOS model. Both models result in lung histopathology similar to human disease. Cytokines and inflammation markers that are elevated in human transplant BOS (TGFbeta, iNOS, IFNgamma) were also elevated significantly in both models. Anti-nuclear antibody was absent from all sera in transplant or toxicant models exhibiting advanced airway pathology. The cytokine osteopontin was highly elevated in BAL early in toxicant-induced BOS, but increased late in the transplant-induced BOS model. The data show that BOS is a disease of a pathologic endpoint that is induced by different triggers and processes. The highly elevated BAL osteopontin early in the toxicant-induced BOS model suggests a need for evaluation in the diagnostic setting.

Pluripotent allospecific CD8+ effector T cells traffic to lung in murine obliterative airway disease

Long-term success in lung transplantation is limited by obliterative bronchiolitis, whereas T cell effector mechanisms in this process remain incompletely understood. Using the mouse heterotopic allogeneic airway transplant model, we studied T cell effector responses during obliterative airways disease (OAD). Allospecific CD8+ IFN-gamma+ T cells were detected in airway allografts, with significant coexpression of TNF-alpha and granzyme B. Therefore, using IFN-gamma as a surrogate marker, we assessed the distribution and kinetics of extragraft allo-specific T cells during OAD. Robust allospecific IFN-gamma was produced by draining the lymph nodes, spleen, and lung mononuclear cells from allograft, but not isograft recipients by Day 14, and significantly decreased by Day 28. Although the majority of allospecific T cells were CD8+, allospecific CD4+ T cells were also detected in these compartments, with each employing distinct allorecognition pathways. An influx of pluripotent CD8+ effector cells with a memory phenotype were detected in the lung during OAD similar to those seen in the allografts and secondary lymphoid tissue. Antibody depletion of CD8+ T cells markedly reduced airway lumen obliteration and fibrosis at Day 28. Together, these data demonstrate that allospecific CD8+ effector T cells play an important role in OAD and traffic to the lung after heterotopic airway transplant, suggesting that the lung is an important immunologic site, and perhaps a reservoir, for effector cells during the rejection process.

Successful treatment of bronchiolitis obliterans in a bone marrow transplant patient with tumor necrosis factor-alpha blockade

Bronchiolitis obliterans (BO) in children is a rare, inflammatory/fibrosing process involving the small airways that often results in progressive, irreversible obstructive pulmonary disease. Because treatment has focused mainly on supportive care and generally unsuccessful immunosuppression, children with BO experience significant morbidity and mortality. We report a case of biopsy-proven BO after bone marrow transplantation in a child who, after failed corticosteroid therapy, was treated with infliximab, a monoclonal antibody with binding specificity for human tumor necrosis factor-alpha. With initiation of treatment, her pulmonary symptoms and radiographic and spirometric evidence of BO resolved. Nine months later, she remains asymptomatic and shows no evidence of pulmonary decompensation. This case illustrates a successful treatment of BO with selective tumor necrosis factor-alpha blockade.

Improvement of refractory rheumatoid arthritis-associated constrictive bronchiolitis with etanercept

Rheumatoid arthritis (RA)-associated constrictive bronchiolitis is a severe condition with no established efficient treatment. A 55-year-old woman with seropositive RA developed rapidly progressive constrictive bronchiolitis confirmed by lung biopsy. Her clinical condition worsened despite steroids and azathioprine. Treatment with etanercept-a tumor necrosis factor (TNF)-alpha inhibitor-combined with methotrexate, resulted in a marked improvement of both her clinical condition and pulmonary function tests. Treatment with TNF-alpha inhibitors and methotrexate may be proposed in RA-associated constrictive bronchiolitis, a severe condition hitherto not amenable to improvement.

Inhibition of obliterative airway disease development in murine tracheal allografts by matrix metalloproteinase-9 deficiency

This study was designed to define the roles of matrix metalloproteinase (MMP)-2 and MMP-9 in obliterative airway disease (OAD) in heterotopic murine tracheal allografts, considered a suitable animal model for chronic lung allograft rejection. BALB/c tracheal allografts were transplanted into MMP-2-deficient (-/-) and MMP-9-/- mice. Also, wild-type recipients were treated with doxycycline, a nonspecific MMP inhibitor. After 10, 20 and 30 days, allografts were analyzed for OAD development, intragraft levels of MMP-2 and MMP-9 and the frequency and cytokine/chemokine production profile of alloreactive T cells. Allografts transplanted into wild-type mice developed OAD lesions within 30 days. These allografts revealed significant upregulation of both MMP-2 and MMP-9. Allografts transplanted into MMP-9-/- and doxycycline-treated recipients did not develop OAD. In contrast, allografts transplanted into MMP-2-/- mice developed OAD lesions with normal kinetics. Interestingly, MMP-9-/- recipients showed an enhanced T cell alloreactivity associated with an abnormal profile of cytokine/chemokine production. The enhanced T cell alloreactivity in MMP-9-/- mice was mediated by enhanced dendritic cell stimulatory capacity as well as enhanced T cell responsive capacity. These results suggest that MMP-9 plays an important role in the pathogenesis of OAD and may represent a target for the therapeutic intervention of chronic lung allograft rejection.

Obliterative airway disease in rat tracheal allografts requires tumor necrosis factor alpha

Obliterative bronchiolitis is the major complication affecting long-term lung transplant survivors. Tumor necrosis factor-alpha (TNF-alpha) promotes inflammation and fibrosis in chronic lung injury models. These experiments defined the role of TNF-alpha in an established model of obliterative airway disease (OAD). Rat tracheas were transplanted from Brown-Norway donors into Lewis recipients, and explanted on days 7 and 14. Treated groups received either anti-TNF-alpha antibodies or a novel TNF-alpha translational inhibitor, RDP-58, beginning either immediately or on post-transplant day 7. Morphometry assessed epithelial loss and luminal obliteration, while separate tracheas were processed for TNF-alpha mRNA expression by RQRT-PCR or protein localization/expression by immunohistochemistry. EMSAs evaluated NFkappaB activation. 14-day control allografts averaged 58% occlusion and 98% epithelial loss. These parameters were significantly improved with TNF-alpha inhibition, averaging 32% luminal obliteration and 37% epithelial preservation. TNF-alpha mRNA expression increased at 14-days relative to native tracheas, and was unchanged by RDP-58 treatment. However, TNF-alpha protein expression, localized to the mucosa/submucosa, was markedly reduced with RDP-58, and resulted in diminished global NFkappaB activation in allografts. Delayed RDP treatment reduced disease progression during the second week, as luminal occlusion increased from 26% to only 35%, while respiratory epithelium persisted at 21%. TNF-alpha promotes the development of OAD in tracheal allografts via an NFkappaB-dependent mechanism, and its inhibition may prove beneficial clinically.