Post-transplant obliterative bronchiolitis and other late lung sequelae in human heart-lung transplantation

The potassium channel KCa3.1 as new therapeutic target for the prevention of obliterative airway disease

BACKGROUND

The calcium-activated potassium channel KCa3.1 is critically involved in T-cell activation as well as in the proliferation of smooth muscle cells and fibroblasts. We sought to investigate whether KCa3.1 contributes to the pathogenesis of obliterative airway disease (OAD) and whether knockout or pharmacologic blockade would prevent the development of OAD.

METHODS

Tracheas from CBA donors were heterotopically transplanted into the omentum of C57Bl/6J wild-type or KCa3.1 mice. C57Bl/6J recipients were either left untreated or received the KCa3.1 blocker TRAM-34 (120 mg/kg/day). Histopathology and immunologic assays were performed on postoperative day 5 or 28.

RESULTS

Subepithelial T-cell and macrophage infiltration on postoperative day 5, as seen in untreated allografts, was significantly reduced in the KCa3.1 and TRAM-34 groups. Also, systemic Th1 activation was significantly and Th2 mildly reduced by KCa3.1 knockout or blockade. After 28 days, luminal obliteration of tracheal allografts was reduced from 89%±21% in untreated recipients to 53%±26% (P=0.010) and 59%±33% (P=0.032) in KCa3.1 and TRAM-34-treated animals, respectively. The airway epithelium was mostly preserved in syngeneic grafts, mostly destroyed in the KCa3.1 and TRAM-34 groups, and absent in untreated allografts. Allografts triggered an antibody response in untreated recipients, which was significantly reduced in KCa3.1 animals. KCa3.1 was detected in T cells, airway epithelial cells, and myofibroblasts. TRAM-34 dose-dependently suppressed proliferation of wild-type C57B/6J splenocytes but did not show any effect on KCa3.1 splenocytes.

CONCLUSIONS

Our findings suggest that KCa3.1 channels are involved in the pathogenesis of OAD and that KCa3.1 blockade holds promise to reduce OAD development.

Bronchiolitis Obliterans Syndrome and Chronic Lung Allograft Dysfunction: Evolving Concepts and Nomenclature

Bronchiolitis obliterans syndrome (BOS) eventually occurs in the majority of lung transplant recipients who survive beyond 1 year, can greatly impair quality of life, and is, directly or indirectly, the major cause of delayed allograft dysfunction and recipient death. A number of associated events or conditions are strongly associated with the risk for developing BOS; these include acute rejection, gastroesophageal reflux, infections, and autoimmune reactions that can occur in the setting of alloimmune responses to the lung allograft as recipients are given intense immunosuppression to prevent allograft rejection. The term chronic lung allograft dysfunction (CLAD) is being increasingly used to refer to recipients with late allograft dysfunction that meets the spirometric criteria for the diagnosis of BOS, but clinicians should recognize that such dysfunction can occur for a variety of reasons other than BOS. The recently identified entity of restrictive allograft syndrome, which is now recognized as a relatively distinct phenotype of CLAD, has features that differentiate it from classic obstructive BOS. A number of other entities that can also significantly affect allograft function must also be considered when significant allograft dysfunction is encountered following lung transplantation.

Cumulative exposure to CD8+ granzyme Bhi T cells is associated with reduced lung function early after lung transplantation

Outcomes following lung transplant remain suboptimal. This is attributable to variable posttransplant recovery of lung function, and inconsistent degrees of lung function loss after peak function is reached. Granzyme B is elevated in the blood and bronchoalveolar lavage (BAL) in acute rejection. We hypothesized that persistent exposure to T cells high in granzyme B would negatively correlate with lung function. We investigated cumulative exposure measured as the area-under-the-curve (AUC) of CD8+ T cell granzyme Bhi cells in the first year posttransplant in both BAL and blood in 24 transplant recipients. We assessed the correlation between cumulative 1-year exposure and FEV1 slope. There was a negative correlation between 1-year exposure and FEV1 slope within the first year (r=-0.63; P=.001). This relationship persisted even when adjusted for transplant type, gender, age, rejection, and indication for transplantation. In contrast, no relationship was seen with the 1-year AUC and lung function after 1 year posttransplant. In contrast to the BAL granzyme Bhi levels, granzyme Bhi levels from the blood showed no relationship with lung function. These findings suggest that CD8+ T-cell-driven factors are responsible for early improvements in lung function after transplantation.

Lung transplantation affects expression of the chemokine receptor type 4 on specific T cell subsets

Alloreactive T cells that infiltrate the graft after lung transplantation (LTx) play a role in chronic rejection. Chemokines such as thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC) and monocyte chemotactic protein-1 (MCP-1) are produced locally in the lung and attract T cells via chemokine receptor 4 (CCR4). In a TARC gradient, cells expressing CCR4(++) migrate more efficiently than CCR4(+) -expressing cells. In this study, we compared the CCR4 expression of T cells in blood from 20 lung transplant recipients to healthy controls. We then examined whether CCR4 expression is associated with the occurrence of chronic rejection. The CCR4(++) expression was decreased on CD4 T cells from LTx patients (P < 0·0001) when compared to healthy controls. The analysis of CD4 T cell subsets showed that this decrease was present on central memory, effector memory and terminally differentiated T cells (P = 0·0007, P < 0·0001 and P = 0·05, respectively), while a trend was found for naive CD4 T cells (P = 0·06). Also, the expression of CCR4(+) on regulatory T cells (T(regs) ) was decreased in LTx patients when compared to healthy controls (P = 0·02). Interestingly, the CCR4(++) expression on CD4 effector memory T cells was decreased in patients developing chronic rejection sometimes more than a year before the clinical diagnosis when compared to patients who did not (P = 0·04). The analysis of CD8 T cell subsets only showed the CCR4(+) expression to be increased significantly on effector memory and terminally differentiated CD8 T cells (P = 0·02, P = 0·03, respectively) in LTx patients, but no relation was found in chronic rejection. In conclusion, the expression of CCR4 on T cell subsets was altered after LTx and appears to be related to chronic rejection.

Bronchiolitis obliterans syndrome: the final frontier for lung transplantation

Bronchiolitis obliterans syndrome (BOS) is a form of chronic lung allograft dysfunction that affects a majority of lung transplant recipients and is the principal factor limiting long-term transplant survival. BOS is characterized by progressive airflow obstruction unexplained by acute rejection, infection, or other coexistent condition. Although BOS is a proven useful clinical syndrome that identifies patients at increased risk for death, its clinical course and underlying causative factors are now recognized to be increasingly heterogeneous. Regardless of the clinical history, the primary pathologic correlate of BOS is bronchiolitis obliterans, a condition of intraluminal airway fibrosis. This article highlights the body of developing research illustrating the mechanisms by which BOS is mediated, including alloimmune reactivity, the emerging roles of humoral and autoimmunity, activation of innate immune cells, and response to nonimmune-related allograft insults, such as infection and aspiration. In addition, we underscore emerging clinical implications and promising future translational research directions that have the potential to advance our knowledge and improve patient outcomes.

The Induction of IgM and IgG Antibodies against HLA or MICA after Lung Transplantation

The production of IgG HLA antibodies after lung transplantation (LTx) is considered to be a major risk factor for the development of chronic rejection, represented by the bronchiolitis obliterans syndrome (BOS). It has recently been observed that elevated levels of IgM HLA antibodies also correlates with the development of chronic rejection in heart and kidney transplantation. This study investigates the relationship between IgM and IgG antibodies against HLA and MICA after lung transplantation. Serum was collected from 49 patients once prior to transplantation and monthly for up to 1 year after lung transplantation was analyzed by Luminex to detect IgM and IgG antibodies against HLA and MICA. The presence of either IgM or IgG HLA and/or MICA antibodies prior to or after transplantation was not related to survival, gender, primary disease, or the development of BOS. Additionally, the production of IgG alloantibodies was not preceded by an increase in levels of IgM, and IgM levels were not followed by an increase in IgG. Under current immune suppressive regimen, although the presence of IgM antibodies does not correlate with BOS after LTx, IgM ^high IgG ^low HLA class I antibody titers were observed more in patients with BOS compared to patients without BOS.

Histological examination of the relationship between respiratory disorders and repetitive microaspiration using a rat gastro-duodenal contents reflux model

Microaspiration due to gastroesophageal reflux (GER) has been suggested as a factor contributing to the development and exacerbation of several respiratory disorders. To explore the relationship between GER and respiratory disorders, we histologically examined the bilateral lungs of a rat gastroduodenal contents reflux model, which was previously used to investigate the histogenesis of Barrett's esophagus and esophageal carcinoma. GER was surgically induced in male Wistar rats. The bilateral lungs of the reflux rats were examined with hematoxylin and eosin (HE), PAS-Alcian blue, and Azan staining at 10 and 20 weeks after surgery. Immunohistochemical staining of CD68 and α-SMA was also performed. Aspiration pneumonia with severe peribronchiolar neutrophilic and lymphocytic infiltrates, goblet cell hyperplasia, prominence of blood vessels, and increased thickness of the smooth muscle layer were detected. Bronchiolitis obliterans (BO)-like lesions comprising granulation tissue with macrophages, spindle cells, and multinucleated giant cells in the lumen of respiratory bronchioles were observed in the bilateral lungs of the reflux animals. These findings suggest that the severe inflammation and the BO-like lesions may play a role in exacerbation of the forced expiratory volume in 1 second (FEV 1) in human cases. In conclusion, we speculate that repetitive microaspiration due to GER may contribute to the exacerbation of various respiratory diseases, particularly asthma and chronic obstructive pulmonary disease (COPD), and the development of BO syndrome following lung transplantation. The reflux model is a good tool for examining the causal relationships between GER and respiratory disorders.

Chronic allograft dysfunction

Chronic, progressive, and irreversible loss of lung function is the major medium-term and long-term complication after lung transplantation and the leading cause of death. Over the past decade, progress has been made in understanding the pathogenesis of bronchiolitis obliterans. Alloimmune factors and nonalloimmune factors may contribute to its development. Understanding the precise mechanism of each type of chronic allograft dysfunction may open up the field for new preventive and therapeutic interventions. This article reviews major new insights into the clinical aspects, pathophysiology, risk factors, diagnosis, and management of chronic allograft dysfunction after lung transplantation.

Loss of tolerance to self after transplant

Organ transplantation is the widely accepted treatment for end-stage organ failure. Since the first successful kidney transplant from an identical twin donor in 1954, researchers have been studying the effects of the immune system on transplantation outcomes. Although the surgery is technically successful, the majority of grafts from genetically disparate donors are rejected due to a number of factors that stimulate recipient immune responses, ultimately resulting in graft loss despite the chronic use of immunosuppressive (IS) drugs. Unfortunately, while short-term success has greatly improved with the development of novel IS drugs, the long-term graft survival of solid organs has not improved significantly over the last few decades. The problem of late graft loss is mainly attributed to development of chronic rejection. Therefore, understanding all of the immune mechanisms involved in transplant rejection is important to prevent graft dysfunction, and eventually, graft loss. In this review, we will give an overview of allograft rejection, the progression from acute to chronic rejection, and in addition, the recent discovery of a critical role for loss of self-tolerance and development of IL-17-dependent autoimmunity in chronic rejection.

Surgical correction of gastroesophageal reflux in lung transplant patients is associated with decreased effector CD8 cells in lung lavages: a case series

BACKGROUND

Lung transplantation is associated with a high incidence of gastroesophageal reflux disease (GERD). The presence of GERD is considered a risk factor for the subsequent development of obliterative bronchiolitis (OB), and surgical correction of GERD by gastric fundoplication (GF) may be associated with increased freedom from OB. The mechanisms underlying a protective effect from OB remain elusive. The objective of this study was to analyze the flow cytometric properties of BAL cells in patients who have undergone GF early after transplant.

METHODS

In a single-center lung transplant center, eight patients with GERD who were in the first transplant year underwent GF. Prior to and immediately following GF, BAL cells were analyzed by polychromatic flow cytometry. Spirometry was performed before and after GF.

RESULTS

GF was associated with a significant reduction in the frequency of BAL CD8 lymphocytes expressing the intracellular effector marker granzyme B, compared with the pre-GF levels. Twenty-six percent of CD8 cells were granzyme Bhi pre-GF compared with 12% of CD8 cells post-GF (range 8%-50% pre-GF, 2%-24% post-GF, P = .01). In contrast, GF was associated with a significant interval increase in the frequency of CD8 cells with an exhausted phenotype (granzyme Blo, CD127lo, PD1hi) from 12% of CD8 cells pre-GF to 24% post-GF (range 1.7%-24% pre-GF and 11%-47% post-GF, P = .05). No significant changes in spirometry were observed during the study interval.

CONCLUSIONS

Surgical correction of GF is associated with a decreased frequency of potentially injurious effector CD8 cells in the BAL of lung transplant recipients.

Survival after bronchiolitis obliterans syndrome among bilateral lung transplant recipients

RATIONALE

Despite the importance of bronchiolitis obliterans syndrome (BOS) in lung transplantation, little is known regarding the factors that influence survival after the onset of this condition, particularly among bilateral transplant recipients.

OBJECTIVES

To identify factors that influence survival after the onset of BOS among bilateral lung transplant recipients.

METHODS

The effect of demographic or clinical factors, occurring before BOS, upon survival after the onset of BOS was studied in 95 bilateral lung transplant recipient using Cox proportional hazards models.

MEASUREMENTS AND MAIN RESULTS

Although many factors, including prior acute rejection or rejection treatments, were not associated with survival after BOS, BOS onset within 2 years of transplantation (early-onset BOS), or BOS onset grade of 2 or 3 (high-grade onset) were predictive of significantly worse survival (early onset P = 0.04; hazard ratio, 1.84; 95% confidence interval, 1.03-3.29; high-grade onset P = 0.003; hazard ratio, 2.40; 95% confidence interval, 1.34-4.32). The effects of both early onset and high-grade onset on survival persisted in multivariable analysis and after adjustment for concurrent treatments. Results suggested an interaction might exist between early onset and high-grade onset. In particular, high-grade onset of BOS, regardless of its timing after transplant, is associated with a very poor prognosis.

CONCLUSIONS

The course of BOS after bilateral lung transplantation is variable. Distinct patterns of survival after BOS are evident and related to timing or severity of onset. Further characterization of these subgroups should provide a more rational basis from which to design, stratify, and assess response in future BOS treatment trials.

Bronchiolar disorders: a clinical-radiological diagnostic algorithm

Bronchiolar disorders are generally difficult to diagnose because most patients present with nonspecific respiratory symptoms of variable duration and severity. A detailed clinical history may point toward a specific diagnosis. Pertinent clinical questions include history of smoking, collagen vascular disease, inhalational injury, medication usage, and organ transplant. It is important also to evaluate possible systemic and pulmonary signs of infection, evidence of air trapping, and high-pitched expiratory wheezing, which may suggest small airways involvement. In this context, pulmonary function tests and plain chest radiographs may demonstrate abnormalities; however, they rarely prove sufficiently specific to obviate bronchoscopic or surgical biopsy. Given these limitations, in our experience, high-resolution CT (HRCT) scanning of the chest often proves to be the most important diagnostic tool to guide diagnosis in these difficult cases, because different subtypes of bronchiolar disorders may present with characteristic image findings. Three distinct HRCT patterns in particular are of value in assisting differential diagnosis. A tree-in-bud pattern of well-defined nodules is seen primarily as a result of infectious processes. Ill-defined centrilobular ground-glass nodules point toward respiratory bronchiolitis when localized in upper lobes in smokers or subacute hypersensitivity pneumonitis when more diffuse. Finally, a pattern of mosaic attenuation, especially when seen on expiratory images, is consistent with air-trapping characteristic of bronchiolitis obliterans or constrictive bronchiolitis. Based on an appreciation of the critical role played by HRCT scanning, this article provides clinicians with a practical algorithmic approach to the diagnosis of bronchiolar disorders.

Reflux-induced collagen type v sensitization: potential mediator of bronchiolitis obliterans syndrome

BACKGROUND

Lung transplantation continues to have poor long-term survival partly because of the high incidence of bronchiolitis obliterans syndrome (BOS). Gastroesophageal reflux disease (GERD) has been implicated in BOS pathogenesis. We investigated the role of collagen type V [col(V)] sensitization in this process.

METHODS

Only primary lung transplant recipients were included. Reflux status was assessed with pH monitoring, impedance plethysmography, and esophagogastroduodenoscopy. Sensitivity to col(V) was determined with trans vivo delayed-type hypersensitivity reaction (DTH). Kaplan-Meier analyses were performed.

RESULTS

Of the 54 recipients, 26 had proven GERD. There were no significant between-group differences in diagnosis; donor and recipient age; sex; ischemic time; single vs bilateral; human leukocyte antigen A, B, and DR matching cytomegalovirus status; acute rejections; or mean follow-up period. The mean DTH response in the GERD group was 25.7 x 10(-4) inches vs 18.3 x 10(-4) inches in the non-GERD group (P = .023). There was a significant reduction in BOS-free survival in the GERD group for both BOS-I (GERD+, 28.3%; GERD-, 86.6%; P = .0001) and BOS-II/III (GERD+, 66.2%; GERD-, 91.7%; P = .0374). A second cohort of 53 patients awaiting lung transplantation also was assayed. The mean DTH response in the GERD group was 24.0 x 10(-4) inches vs 13.1 x 10(-4) inches in the non-GERD group (P = .003). There were no differences in age or sex.

CONCLUSIONS

GERD is strongly associated with the development of BOS after primary lung transplantation. Col(V) sensitization is associated with reflux and BOS and may play an intermediary role in the pathogenesis of BOS. Trials using col(V) reactivity to assess the impact of antireflux procedures in patients with lung transplantation and idiopathic pulmonary fibrosis are warranted.

The orthotopic left lung transplantation in rats: a valuable experimental model without using cuff technique

Advances in the field of clinical lung transplantation must rely on observations made in animal models. In this study, we introduced a new procedure in the rat, orthotopic left lung transplantation without using the cuff technique, in which the donor pulmonary artery, pulmonary vein, and membranous parts of the bronchus were anastomosed continuously in the lumen using a mattress suture under a surgical microscope; meanwhile, a second, low-pressure perfusion through the pulmonary artery and turnover of the vascular stump were made, which also made the vessel anastomosis easy. Transplantations were completed in 68 rats (89.5%), the mean time used for suturing the left lung hilar structure was 23.5 +/- 4.6 min. All lung grafts had good life-sustaining function because of there being no cuff-induced granulation tissue in bronchial anastomotic stoma, and three out of 12 allografts were observed with active bronchiolitis obliterans lesions at 8 weeks after transplantation. This model is a simple, valuable experimental model for studying lung transplantation and new therapies for preventing acute or chronic rejection.

Serum thymus and activation regulated chemokine levels post-lung transplantation as a predictor for the bronchiolitis obliterans syndrome

The main reason for mortality after lung transplantation is the bronchiolitis obliterans syndrome (BOS), which represents chronic rejection. As soluble CD30, which is produced mainly by activated T helper 2 (Th2) cells, was shown to be related to development of BOS, we aimed to investigate the relation between development of BOS and Th2 chemoattractant thymus and activation regulated chemokine (TARC/CCL17). In 54 patients we measured serum TARC levels prior to transplantation by enzyme-linked immunosorbent assay, and in 44 of these patients sera were analysed at months 1, 2 and 3 after lung transplantation. In addition, longitudinal measurements were performed in sera from eight healthy controls and 14 patients, the latter taken over a period of 2 years post-transplantation from seven patients developing BOS plus seven clinically matched BOS-free patients. Median serum TARC levels post-transplantation of patients who developed BOS were significantly lower than those of the matched BOS-free patients (P = 0.05). A receiver operating characteristics analysis (area under the curve 0.77), together with a Kaplan-Meyer analysis, showed that serum TARC levels below 325 pg/ml in the first month post-transplantation can predict development of BOS post-transplantation (P = 0.001). In contrast, pretransplant serum TARC levels were not significantly different between patients developing BOS, BOS-free patients or healthy controls. In conclusion, pretransplantation serum TARC levels do not predict the development of BOS post-transplantation, but measurement of the serum TARC levels in the first month directly after transplantation can provide us with a tool to identify the group at risk of developing BOS.

Obstructive sleep apnoea and nocturnal gastroesophageal reflux are common in lung transplant patients

BACKGROUND AND OBJECTIVE

Gastroesophageal reflux (GOR) has been implicated in the pathogenesis of bronchiolitis obliterans syndrome (BOS), possibly due to pulmonary aspiration of refluxed acid. Risk of aspiration of gastric contents is increased during sleep due to decreased oesophageal clearance mechanisms and may be further increased by the presence of OSA. This study investigated the relationship between nocturnal GOR, OSA and BOS in a group of lung transplant patients.

METHODS

Fourteen lung transplant patients underwent overnight polysomnography with simultaneous dual oesophageal pH monitoring.

RESULTS

Patients had an FEV(1) of 84 +/- 15% of their best post-transplant FEV(1). Six of the 14 patients were in various stages of BOS. The average proportion of time spent overnight with a pH of <4 was 1.7 +/- 3.1%. Increased GOR was evident in 8/14 patients during the postprandial period and/or overnight in the distal and/or proximal oesophagus. All patients had OSA (AHI >5 events per hour). There were no relationships between severity of OSA or GOR and severity of BOS.

CONCLUSION

Both nocturnal GOR and OSA were common in this group of patients but their occurrences were not related. Neither was there any relationship between the presence of nocturnal GOR or OSA and severity of BOS.

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.

Activation of Tissue Remodeling Precedes Obliterative Bronchiolitis in Lung Transplant Recipients

Obliterative bronchiolitis (OB) and Bronchiolitis Obliterans Syndrome (BOS) are frequent complications in the lung transplant recipient, and are the leading cause of mortality after transplantation. The mechanisms responsible for OB remain elusive, but inflammatory and tissue remodeling responses are implicated. We hypothesized that alterations in markers of tissue remodeling in BALF of lung transplant recipients could predict development of OB. To test this, we identified 13 lung transplant recipients who developed both BOS and histologic OB (OB group) at median post-operative day (POD) 485 (range 73–2070). Bronchoalveolar lavage fluid (BALF) was obtained at median POD 387 (range 45–2205), which preceded the onset of OB and BOS by a median of 140 days (range 60–365). As a control, BALF was also obtained from a group of 21 stable recipients without OB (non-OB group) at median POD 335 (range 270–395). BALF was examined for gelatinolytic activity, fibronectin gene transcription, and transforming growth factor-β1 (TGF-β1) expression. Gelatin zymography of BALF from the OB group showed increased matrix metalloproteinase-9 (MMP-9) activity over that of the non-OB group (p < 0.005). Similarly, BALF from the OB group induced greater fibronectin expression in fibroblasts compared to the non-OB group (p < 0.03). The induction of fibronectin also correlated with the amount of TGF-β1 protein in BALF (r = 0.71) from the OB group. We conclude that activation of tissue remodeling precedes the onset of OB, and analysis of gelatinolytic and/or fibronectin-inducing activity in BALF can serve as an early, pre-clinical marker for OB.

Assessment of mean transit time in the engrafted lung with 133Xe lung ventilation scintigraphy improves diagnosis of bronchiolitis obliterans syndrome in living-donor lobar lung transplant recipients

OBJECTIVE

Staging of bronchiolitis obliterans syndrome (BOS) following lung transplantation is based on declines in forced expiratory volume in 1 s (FEV(1)). The aim of this study was to evaluate the usefulness of (133)Xe ventilation scintigraphy in the early detection of BOS following living-donor lobar lung transplantation (LDLLT), to compare (133)Xe washout imaging with computed tomography (CT) findings for early detection of BOS following LDLLT, and to evaluate (133)Xe washout imaging by quantitative analyses.

METHODS

Subjects comprised 30 double-lung recipients and 1 single-lung recipient, who had undergone LDLLT at our institution and survived more than 1 year. Clinically diagnosed BOS developed in six recipients. Declines in graft function were evaluated using a combination of three methods, namely, dynamic spirometry, high-resolution CT (HRCT), and (133)Xe ventilation scintigraphy. Findings for all transplanted lungs were compared between CT and (133)Xe washout imaging. (133)Xe washout imaging was assessed using mean transit time (MTT) of bi-and unilateral lungs. Correlations between MTT of bilateral lungs and FEV(1)% were evaluated. Differences in MTT between BOS and non-BOS lungs, and between non-BOS and donor lungs were also evaluated on unilateral lungs. Appropriate cut-off values of MTT of unilateral lungs were set for the diagnosis of BOS.

RESULTS

In all six BOS cases, prolonged-washout images of engrafted lungs revealed early-phase BOS with declines from baseline FEV(1), whereas only one BOS case could be detected using early CT findings of BO (bronchodilatation, decrease in number and size of pulmonary vessels, thickening of septal lines, and volume reduction). A significant correlation was identified between MTT and FEV(1)% (r = -0.346, P < 0.0001). MTT of unilateral lungs was significantly longer in BOS lungs than in non-BOS lungs (P < 0.0001). The cut-off MTT of unilateral lungs for the diagnosis of BOS was set at 64.77 s.

CONCLUSIONS

Our data show that (133)Xe washout imaging offers excellent potential for early detection of BOS compared with early CT findings. Using (133)Xe washout imaging and MTT with radioactive tracer offers a noninvasive indication of selective ventilatory function in engrafted lungs following LDLLT. MTT appears useful for identifying BOS following LDLLT and allows quantitative evaluation of graft function in unilateral lungs.

IL-17-dependent cellular immunity to collagen type V predisposes to obliterative bronchiolitis in human lung transplants

Bronchiolitis obliterans syndrome (BOS), a process of fibro-obliterative occlusion of the small airways in the transplanted lung, is the most common cause of lung transplant failure. We tested the role of cell-mediated immunity to collagen type V [col(V)] in this process. PBMC responses to col(II) and col(V) were monitored prospectively over a 7-year period. PBMCs from lung transplant recipients, but not from healthy controls or col(IV)-reactive Goodpasture's syndrome patients after renal transplant, were frequently col(V) reactive. Col(V)-specific responses were dependent on both CD4+ T cells and monocytes and required both IL-17 and the monokines TNF-alpha and IL-1beta. Strong col(V)-specific responses were associated with substantially increased incidence and severity of BOS. Incidences of acute rejection, HLA-DR mismatched transplants, and induction of HLA-specific antibodies in the transplant recipient were not as strongly associated with a risk of BOS. These data suggest that while alloimmunity initiates lung transplant rejection, de novo autoimmunity mediated by col(V)-specific Th17 cells and monocyte/macrophage accessory cells ultimately causes progressive airway obliteration.

Animal models for bronchiolitis obliterans syndrome following human lung transplantation

Lung transplantation is the only viable treatment option that can improve survival and enhance the quality of life of patients with end-stage lung diseases such as emphysema, cystic fibrosis, idiopathic pulmonary fibrosis, and primary pulmonary hypertension. However, the long-term survival of lung allografts is still limited by the development of bronchiolitis obliterans syndrome (BOS), an irreversible condition unresponsive to therapy. BOS is the most significant cause of long-term morbidity and mortality after lung transplantation. Over the past decade, several animal models have been developed to investigate BOS. These are valuable to elucidate the immunologic and pathologic mechanisms that lead to BOS and to test treatment options for BOS. In this review, we discuss the advantages and disadvantages of different animal models and highlight work that has been done with each model.

Identification and Validation of Proteinase 3 and Latent Matrix-Metalloproteinase 9 as Potential Biomarkers for Chronic Lung Transplant Rejection

Introduction

This study examined potential biomarkers for the diagnosis and early detection of chronic allograft rejection after lung transplantation.

Methods

Protein ratios in pooled samples of bronchoalveolar lavage fluid (BALF) from lung transplant recipients at different stages of pre- and postchronic rejection were determined by iTRAQ labeling and mass spectrometry. The potential biomarkers were validated using enzyme-linked immunosorbent assay (ELISA) assay.

Results

Two hundred sixty-five proteins were identified, about two thirds of which showed more than a twofold difference between a pooled control sample (individuals who did not develop chronic rejection in 100 months) and a pooled sample from those with chronic rejection. Proteinase 3 (PR-3) and matrix metalloproteinase 9 (MMP-9) were validated by ELISA assay of 124 individual samples. PR-3 and the latent form of MMP-9 (proMMP9) both demonstrated a specificity of 92% with sensitivities of 76% and 82%, respectively, for disease diagnosis; both were also predictors of developing chronic rejection up to 15 months before diagnosis. While immunoglobulin M (IgM) was upregulated in the pooled samples, individual sample analysis revealed that this arose from outlier values.

Conclusions

iTRAQ can be used to detect a large number of proteins in pooled samples for the discovery of potential biomarkers, but the findings must be validated with technology capable of distinguishing broadly based changes from outcomes as a result of a few extreme cases. The proteins identified in this study expanded the panel of potential biomarkers for the diagnosis and prediction of chronic rejection and provided additional insight into the mechanism of the disease.

Techniques for experimental heterotopic and orthotopic tracheal transplantations — When to use which model?

BACKGROUND

Different animal models have been developed to study the pathogenesis and treatment of obliterative airway disease (OAD). Here we describe the techniques of heterotopic and orthotopic tracheal transplantations in the rat, comparing the kinetics of systemic host immune response and of histopathologic OAD development.

METHODS

Heterotopic and orthotopic tracheal transplantations were performed in both allogeneic (Brown Norway-to-Lewis) and syngeneic (Lewis-to-Lewis) models. Grafts were harvested after 7, 30, and 60 days post-transplant for histologic evaluation and analysis of host cellular and humoral response.

RESULTS

Syngeneic tracheal grafts did not develop luminal obliteration and were morphologically indistinguishable from native tracheas. In heterotopic allografts, airway epithelium was rapidly destroyed and OAD progressed with complete luminal occlusion by 30 days. Orthotopic allografts showed enhanced early infiltration (1298+/-45 vs. 674+/-75 cells/high power field, p<0.001) with concomitant greater day 7 luminal narrowing (45+/-6% vs. 14+/-3%, p<0.001). In this model, donor-type BN epithelium (62+/-17%, 21+/-19%, and 1+/-1% on days 7, 30, and 60) was gradually replaced by recipient-type epithelial cells (2+/-4%, 70+/-22%, and 98+/-2%). OAD developed with circular orientation of cells and connective tissue fibers to 45+/-6% obliteration by day 60. Cellular host response, as determined by IFN-gamma-ELISPOT assay (548+/-132 vs. 402+/-197 spots, p=0.046) and anti-donor alloreactive IgM antibody production (2827+/-148 vs. 1565+/-393 mean channel fluorescence, p<0.001) were significantly stronger in rats bearing orthotopic vs. heterotopic allografts.

CONCLUSIONS

The orthotopic tracheal transplantation model may be more representative of OAD found in human lung transplant recipients and we therefore encourage the wider use of this model.

Bronchiolitis obliterans following lung transplantation

Bronchiolitis obliterans syndrome (BOS) is the main and late chronic complication after lung transplantation. It remains a major impediment to long-term outcome. Unfortunately, the survival rate of lung transplant recipients lags behind that of other organ transplant recipients, and BOS accounts for more than 30% of all mortality after the third year following lung transplantation. Most recent studies suggest that immune injury is the main pathogenic event in small airway obliteration and the development of BOS. Early detection of BOS is possible as well as essential because prompt initiation of treatment may halt the progress of the disease and the development of chronic graft failure. Current treatment of BOS is disappointing despite advances in surgical techniques and improvements in immunosuppressive therapies. Therefore, a clear understanding of the pathogenesis of BOS plays a major role in the search for new and effective therapeutic strategies for better long-term survival and quality of life after lung transplantation.

Prevalence of gastroesophageal reflux in end-stage lung disease candidates for lung transplant

BACKGROUND

Aspiration secondary to gastroesophageal reflux has been postulated to be a contributing factor in bronchiolitis obliterans after lung transplantation. It is not clear whether gastroesophageal reflux is a preexisting condition or secondary to intraoperative vagal injury or drug-induced prolonged gastric emptying.

METHODS

The prevalence of gastroesophageal reflux was examined in 78 consecutive end-stage lung disease patients assessed for lung transplantation: emphysema, 21; cystic fibrosis, 5; idiopathic pulmonary fibrosis, 26; scleroderma, 10; and miscellaneous diseases, 16. All underwent esophageal manometry. Two-channel esophageal 24-hour pH testing was completed in 76 patients. Gastric emptying studies were conducted in 36 patients.

RESULTS

Typical gastroesophageal reflux symptoms were documented in 63% of patients. The lower esophageal sphincter was hypotensive in 72% of patients, and 33% had esophageal body dysmotility. Prolonged gastric emptying was documented in 44%, and 38% had abnormal pH testing. The overall DeMeester score was above normal in 32% of patients, and 20% had abnormal proximal pH probe readings.

CONCLUSIONS

Gastroesophageal reflux is highly prevalent in end-stage lung disease patients who are candidates for lung transplantation. Further investigation is needed to study the prevalence of gastroesophageal reflux after lung transplantation and its contribution to chronic allograft dysfunction.

Regulatory T cell-mediated transplantation tolerance

The existence of naturally occurring regulatory T cells in normal hosts and their pivotal role in maintaining both auto- and allo-tolerance have direct implications on the therapy of autoimmune disorders and for achieving immunosuppression-free allotransplantation. Among the various forms of regulatory T cells described, CD4(+)CD25(+) T cells have emerged as one of the most potent tolerogenic subsets. In this review, we discuss the molecular basis of development and function of these regulatory T cells and their potential role in the context of chronic lung allograft rejection.

Upper lobe fibrosis: a novel manifestation of chronic allograft dysfunction in lung transplantation

BACKGROUND

Lung transplantation is an established treatment modality for a number of chronic lung diseases. Long-term survival after lung transplantation is limited by chronic allograft dysfunction, usually manifested by bronchiolitis obliterans syndrome. We describe a case series with upper lobe fibrosis, a novel presentation of chronic allograft dysfunction.

METHODS

We reviewed lung transplants at the Toronto General Hospital and Duke University Hospital from 1990 to 2002 and identified patients with upper lobe fibrosis.

RESULTS

Thirteen of 686 patients (6 women) developed upper lobe fibrosis (Toronto, 9; Duke, 4); 12 of 13 had bilateral transplants. The median age at diagnosis was 42 years (range, 19-70). Primary diagnoses were cystic fibrosis, 6; emphysema, 4; sarcoidosis, 1; and pulmonary fibrosis, 2 patients. Radiographic diagnosis was made at a median of 700 days post-transplant (range, 150-2,920). Pulmonary function tests demonstrated predominantly a progressively worsening restrictive pattern. Open lung biopsy specimens revealed dense interstitial fibrosis, with occasional features of obliterative bronchitis, bronchiolitis obliterans obstructive pneumonia, and aspiration. Nine patients died at a median follow-up of 2,310 days (range, 266-3,740), 8 due to respiratory failure.

CONCLUSION

Upper lobe fibrosis is a novel presentation of chronic allograft dysfunction in lung transplant recipients and is differentiated from bronchiolitis obliterans syndrome on the basis of physiologic and radiologic findings.

Pathologic correlates of bronchiolitis obliterans syndrome in pulmonary retransplant recipients

RATIONALE

The main hindrance to long-term success of lung transplantation is bronchiolitis obliterans syndrome (BOS), generally thought to be a manifestation of chronic allograft rejection. BOS is associated histologically with epithelial injury, bronchocentric mononuclear inflammation, and fibrosis of small airways known as bronchiolitis obliterans (BO). Few studies have directly compared clinical, radiographic, and histologic findings of BOS and BO, particularly in the era of improved immunosuppression and infection prophylaxis. Patients undergoing pulmonary retransplantation for BOS provide a unique opportunity to investigate these relationships.

METHODS

All patients who underwent pulmonary retransplantation for BOS from 1992 to 2004 at Duke University Medical Center were reviewed. Pathology findings in explanted lung allografts were compared with clinical, radiographic, and transbronchial biopsy data.

RESULTS

Over the 12-year study period, 12 patients underwent pulmonary retransplantation for BOS. The median time to BOS was 517 days (intraquartile range, 396 to 819.8 days). BOS scores prior to retransplantation were 2 in 2 patients and 3 in 10 patients. We developed a semiquantitative scoring system for epithelial, inflammatory, and fibrotic changes in affected airways to permit better comparison between BO and BOS. Somewhat surprisingly, only 50% (6 of 12 patients) had severe fibrotic changes, although all had some degree of epithelial injury, fibrosis, or inflammation centered around the bronchi and bronchioles. Furthermore, pathology findings other than BO were present in most explanted allografts and included cholesterol clefts (n = 4), focal invasive aspergillosis (n = 1), interstitial fibrosis (n = 2), and chronic vascular rejection (n = 1).

CONCLUSIONS

In this series of patients with advanced BOS undergoing retransplantation, at least some degree of BO was present in all explanted allografts. However, the degree of epithelial changes, fibrosis, and inflammation present among affected bronchi varied considerably. Furthermore, a wide range of pathologic processes of potential clinical significance were evident in half of the patients. We conclude that significant histologic heterogeneity exists among patients undergoing retransplantation for BOS, potentially contributing to the variability of patient responses to treatment.

Allograft Rejection After Lung Transplantation

Lung transplantation has become an accepted therapy for selected patients with advanced lung disease. One of the main limitations to successful lung transplantation is rejection of the transplanted organ. This article discusses the clinical presentation, treatment, and prevention of hyperacute, acute, and chronic rejection in the lung transplant recipient.

Lung transplantation: opportunities for research and clinical advancement

Lung transplantation is the only definitive therapy for many forms of end-stage lung diseases. However, the success of lung transplantation is limited by many factors: (1) Too few lungs available for transplantation due to limited donors or injury to the donor lung; (2) current methods of preservation of excised lungs do not allow extended periods of time between procurement and implantation; (3) acute graft failure is more common with lungs than other solid organs, thus contributing to poorer short-term survival after lung transplant compared with that for recipients of other organs; (4) lung transplant recipients are particularly vulnerable to pulmonary infections; and (5) chronic allograft dysfunction, manifest by bronchiolitis obliterans syndrome, is frequent and limits long-term survival. Scientific advances may provide significant improvements in the outcome of lung transplantation. The National Heart, Lung, and Blood Institute convened a working group of investigators on June 14-15, 2004, in Bethesda, Maryland, to identify opportunities for scientific advancement in lung transplantation, including basic and clinical research. This workshop provides a framework to identify critical issues related to clinical lung transplantation, and to delineate important areas for productive scientific investigation.

Bile acid aspiration and the development of bronchiolitis obliterans after lung transplantation

BACKGROUND

Aspiration of gastroesophageal refluxate may contribute to lung transplant bronchiolitis obliterans syndrome (BOS). We investigated bile acids in bronchoalveolar lavage fluid (BALF) and studied its role in BOS.

MATERIALS AND METHODS

Surveillance pulmonary function tests and BALF were evaluated in 120 lung recipients. BOS-(0p-3) was diagnosed after 6 months' survival. BOS was defined as "early" if diagnosed within 12 months after a transplant. BALF was assayed for differential cell count, bile acids, and interleukins 8 and 15. Bile acids were considered elevated if greater than normal serum levels ( or =8 micromol/L).

RESULTS

Elevated BALF bile acids were measured in 20 (17%) of 120 patients. BOS was diagnosed in 36 (34%) of 107 patients and judged "early" in 21 (57%) of 36. Median BALF bile acid values were 1.6 micromol/L (range, 0-32 micromol/L) in BOS patients and 0.3 micromol/L (range, 0-16 micromol/L) in non-BOS patients ( P = .002); 2.6 micromol/L (range, 0-32 micromol/L) in early BOS patients and 0.8 micromol/L (range, 0-4.6 micromol/L) in late BOS patients, ( P = .02). Bile acids correlated with BALF IL-8 and alveolar neutrophilia (r = 0.3, P = .0004, and r = 0.3, P = .004, respectively), but not with IL-15. Freedom from BOS was significantly shortened in patients with elevated BALF bile acids (Cox-Mantel test, P = .0001).

CONCLUSIONS

Aspiration of duodenogastroesophageal refluxate is prevalent after lung transplantation and is associated with the development of BOS. Elevated BALF bile acids may promote early BOS development via an inflammatory process, possibly mediated by IL-8 and alveolar neutrophilia.

Detection of chronic rejection by quantitative ventilation scintigrams in lung-transplanted patients: a pilot study

The suspicion of chronic rejection [bronchiolithis obliterans syndrome (BOS)] is usually based on deteriorating forced expired volume in 1 s. It is however, desirable to develop more sensitive methods as increased anti-inflammatory therapy is thought to stop progression of the rejection. The aim of the present study was to develop quantitative tools based on ventilation scintigrams, to diagnose BOS. Sixteen double-lung-transplanted patients participated, six developing BOS and 10 who did not develop BOS. They were investigated with planar posterior-anterior (99m)Tc-Technegas (Tetley Manufacturing Ltd, Sydney, Australia) ventilation scintigraphy at baseline, 6 months to 1 year post-transplantation, and at a follow-up examination 3-4-year post-transplant or in the BOS patients close to the time of the diagnosis. An automatic region of interest (ROI) was drawn on each lung in the scintigraphic image at baseline and also applied to the follow-up investigation. The area inside the ROI was subdivided into stripes 10.8 mm high and squares 10.8 x 10.8 mm wide. Corresponding stripes and squares in baseline and follow-up were analysed regarding differences in relative retention. The results show that the square analysis is superior. Applying chosen cut-off values for square element differences, 6/6 right and 5/6 left BOS lungs were identified and one left and one right lung of patients not developing BOS were misclassified. We conclude that the square element difference appears to be a promising method to diagnose BOS.

Lung Transplantation Biopsy Specimens With Bronchiolitis Obliterans or Bronchiolitis Obliterans Organizing Pneumonia Due to Aspiration

Context.—Bronchiolitis obliterans (BO) is generally thought to be a marker of chronic airway rejection in patients who have undergone lung transplantation. Bronchoscopic biopsy specimens, by virtue of their small size, may sample only BO and not a lesion of bronchiolitis obliterans organizing pneumonia (BOOP). A role for ongoing chronic infection or aspiration has also been suggested, and the distinction of these etiologies may be difficult clinically and pathologically.

Objective.—To investigate the etiology of BO and BOOP in lung transplantation patients who had chronic aspiration.

Design.—This is a clinicopathologic study of 7 patients who had undergone lung transplantation in which biopsy findings suggested the possibility of chronic airway rejection but in which aspiration was subsequently proven as a cause of the bronchiolar disease.

Results.—All patients were men, who ranged in age from 19 to 57 years. A clinical diagnosis of aspiration was considered based on history, acid reflux testing, and radiographic findings in all 7 patients. Three patients had BO and 4 patients had BOOP. Histiocytic giant cells or foreign material was absent. The interval from transplantation to BO ascribed to aspiration ranged from 2.5 months to 7 years. The patients were treated aggressively with medication for gastroesophageal reflux disease. Their respiratory function and chest radiography results improved.

Conclusion.—Although BO may be a manifestation of rejection, it may also be a manifestation of aspiration. Because the latter is potentially correctable, aspiration should be considered etiologically in lung transplantation patients with either BO or BOOP. Reliable distinction between aspiration-related or rejection-related BO and BOOP cannot be made on morphologic grounds alone. Clinical and radiologic correlations are indicated to establish the distinction.

A novel model for post-transplant obliterative airway disease reveals angiogenesis from the pulmonary circulation

We present a novel animal model for post-transplant obliterative airway disease in which the donor trachea is implanted into the recipient's lung parenchyma. Although this procedure is technically more challenging than the heterotopic model of implantation into a subcutaneous pouch, it has several important advantages some of which are the appropriate local environment and the possibility of local immunosuppressive therapy after transtracheal gene, cell or drug delivery. This model has revealed new insights into angiogenic potential of the pulmonary circulation.

Bronchiolitis Obliterans Syndrome

Post-transplantation bronchiolitis obliterans syndrome (BOS) is a clinicopathological syndrome characterised histologically by obliterative bronchiolitis (OB) and physiologically by airflow limitation. It affects long-term survival with no consistently effective treatment strategy.An updated review of risk factors for OB/BOS, and approaches to prevention and treatment was performed through a systematic review of relevant studies between January 1990 and February 2005. The initial search identified 853 publications, with 56 articles reviewed after exclusions. Early acute rejection is the most significant risk factor, with late rejection (> or =3 months) also significant. Lymphocytic bronchitis/bronchiolitis is relevant, with later onset associated with greater risk. Viral infections are identified as significant risk factors. Human leukocyte antigen matching and OB/BOS development is a weaker association, but is stronger with acute rejection. Recipient and donor characteristics have a minor role. There is limited evidence that altering immunosuppression is effective in reducing the rate of decline in lung function. BOS reflects an allo-immunological injury, possibly triggered by cytomegalovirus and respiratory viral infections, or noninfectious injury. Immunological susceptibility may be reflected by more frequent acute rejection episodes. Preventative and therapeutic modifications in immunosuppression remain important. Identifying markers of immunological susceptibility and, hence, risk stratification requires further research.

Donor brain death aggravates chronic rejection after lung transplantation in rats

BACKGROUND

Many recipients of lung transplants from brain-dead donors develop bronchiolitis obliterans, a manifestation of chronic rejection. It has been shown that brain death increases inflammatory mediators and accelerates acute rejection in kidney, liver, and heart transplants. In this study, the authors investigated the hypothesis that brain death increases inflammatory mediators in the donor lung and subsequently aggravates chronic rejection of the lungs after transplantation in rats.

METHODS

Brain death was induced in F344 rats by inflation of a subdurally placed balloon catheter. After 6 hr, donor lungs were assessed for influx of leukocytes, expression of cell adhesion molecules, and cytokine mRNA expression. For assessment of the lung after transplantation, lungs from brain-dead F344 rats were transplanted into WKY rats. Lung function after transplantation was monitored by chest radiographs during an observation period of 100 days. At the end of this period, the lungs were histologically examined; also, cytokine mRNA expression was measured. Lungs from ventilated living donors and living donors served as controls.

RESULTS

After 6 hr of brain death, influx of polymorphonuclear cells and macrophages and expression of vascular cell adhesion molecule-1 in the donor lungs was increased. After transplantation at postoperative day 100, the lung function was significantly decreased compared with allografts from living donors. In the lung allografts from brain-dead donors, histologic symptoms of chronic rejection were obvious, including severe intimal hyperplasia but without bronchiolitis obliterans. Interleukin-2 mRNA was significantly increased in allografts from brain-dead donors compared with living donors.

CONCLUSIONS

This study shows that brain death induces an inflammatory response in the donor lung and subsequently aggravates chronic rejection after transplantation. This may explain the clinical difference in long-term function between lungs from cadaveric donors and living donors.

Bronchiolitis obliterans

Bronchiolitis obliterans (BO) is a disease of small airways that results in progressive dyspnea and airflow limitation. It is a common sequela of bone marrow, lung, and heart-lung transplantation, but can also occur as a complication of certain pulmonary infections, adverse drug reaction, toxic inhalation, and autoimmune disorders. Non-transplant-related BO is rare and can mimic asthma and chronic obstructive pulmonary disease (COPD). In transplant-related BO, the diagnosis can be suggested by obstructive changes in serial pulmonary function testings, while open lung biopsy is usually required in non-transplant cases. High-resolution computerized tomography (HRCT) is also a helpful tool to diagnose and assess the severity of BO. The treatment of BO, regarding of the cause, is usually disappointing. Systemic corticosteroid immunosuppression and retransplantation have been described with variable success.

Bronchiolitis obliterans

PURPOSE OF REVIEW

Bronchiolitis obliterans (BO) occurs in both post-lung transplant and nontransplant-related individuals, and is characterized by mainly irreversible airflow obstruction that is often ultimately progressive.

RECENT FINDINGS

While post-lung transplant BO is a major cause of lung allograft dysfunction, and hence is better characterized than nontransplant-related BO, it is likely that many similarities in pathogenesis and treatment apply to both categories.

SUMMARY

Optimal management for BO remains to be established, and the role of retransplantation in this disease requires further consensus. Minimization of risk factors for BO and earlier detection in the form of methacholine challenge testing and HRCT scans of the chest amongst other forms of detection, may help in the stabilization and possible resolution of early BO.

Role of CMV pneumonia in the development of obliterative bronchiolitis in heart-lung and double-lung transplant recipients

Obliterative bronchiolitis (OB) is the main cause of late mortality after lung transplantation. Cytomegalovirus infection has been associated with late graft failure. The aim of this study was to determine whether the development of OB was related to CMV pretransplant serological status and to CMV infections. The study group comprised 36 lung transplant recipients (27 HLT and 9 DLT) who survived more than 4 months, of whom 47% developed OB (defined by the persistence of an unexplained obstructive disease: FEV1/VC < 0.7). OB occurred more frequently: (1) in seronegative recipients with seropositive donors (8/9) than in seropositive recipients (7/19) or seronegative well-matched recipients (2/8); and (2) in patients who experienced CMV pneumonia (11/16) and CMV recurrence (11/16). Since matching seronegative recipients is the best way to prevent CMV infection, we believe that seronegative grafts must be reserved for seronegative recipients.

CTLA4Ig-gene transfection inhibits obliterative airway disease in rats

BACKGROUND

Obliterative airway disease (OAD) is a major cause of long-term morbidity following lung transplantation. Its pathologic characteristics are small-airway inflammation and occlusion by fibrous tissue. However, the pathogenesis is uncertain and therapy is ineffective. This study presents the effects of CTLA4Ig-gene therapy on OAD in heterotopically transplanted rat tracheal allografts.

METHODS

Dark Agouti (DA, RT1a) allografts and Lewis (LEW, RT1l) isografts were transplanted into Lewis recipients. The tracheal graft was transplanted heterotopically into the subcutaneous pocket into the back. Adenoviral vectors (1.0x10(9) pfu) containing the CTLA4Ig-gene (AdCTLA4Ig) or the LacZ-gene (AdLacZ) were injected into the tail vein immediately after grafting. Grafts were harvested and examined after more than 35 days for mononuclear cell infiltration development and lumen occlusion with fibrosis.

RESULTS

Fully allogenic DA tracheas, treated with AdCTLA4Ig had significantly lower pathologic scores and infiltrating scores than the control allografts. The pathologic findings of the grafts, treated with AdCTLA4Ig, were very similar to those of the syngeneic grafts. The animals experienced no adverse events during follow-up. No evidence of vector-mediated tissue damage was seen in any graft.

CONCLUSIONS

Adenoviral vectors containing the CTLA4Ig-gene markedly inhibited the obliteration of the airway lumen. OAD may be associated with T-cell responses against graft tissue and alloimmune injury.

Bronchiolitis obliterans syndrome in lung transplant recipients: correlation of computed tomography findings with bronchiolitis obliterans syndrome stage

The purpose of this study was to correlate the extent of computed tomographic (CT) findings with the severity of respiratory dysfunction in lung transplant recipients with bronchiolitis obliterans syndrome (BOS). Eighty-nine conventional and 61 thin-section CT scans performed in 44 transplant recipients (17 bilateral, 27 single) with BOS were reviewed for mosaic attenuation, degree of bronchial dilation, bronchial thickening, central and peripheral bronchiectasis, mucus plugging, and air trapping. Findings on conventional and thin-section CT scans were correlated with BOS stage for bilateral and single-lung transplant recipients. In bilateral-lung recipients, a significant correlation existed, although weak, between BOS stage and findings of degree of bronchial dilation (P < 0.01), bronchial wall thickening (P = 0.01), peripheral bronchiectasis (P = 0.01), and mosaic attenuation (P = 0.01) on conventional CT; and bronchial wall thickening (P = 0.01) and mosaic attenuation (P = 0.03) on thin-section CT. In single-lung recipients, BOS stage correlated only with the finding of central bronchiectasis (P = 0.02) on conventional CT scans. No correlation was found between the extent of air trapping and BOS stage in either single- or bilateral-lung transplant recipients. CT findings are relatively poor indices of airflow obstruction in lung transplant recipients with BOS, particularly in those with single-lung transplants for emphysema.

PG490-88, a derivative of triptolide, attenuates obliterative airway disease in a mouse heterotopic tracheal allograft model

The current treatment of obliterative bronchiolitis in lung transplant recipients is sub-optimal. Triptolide is a novel immunosuppressant that has a mechanism of action distinct from currently available immunosuppressants, including induction of T-cell apoptosis, blockade of fibroblast proliferation/maturation and inhibition of transforming growth factor-beta (TGF-beta) mRNA production. We hypothesized that triptolide may be helpful in blocking obliterative airway disease in lung transplant recipients. We investigated the effect of PG490-88, a water-soluble derivative of triptolide, in a mouse heterotopic tracheal allograft model of obliterative airway disease. We show that PG490-88 attenuates airway obliteration in this model and inhibits accumulation of inflammatory cells, and therefore may have preventive or therapeutic benefits for patients with obliterative airway disease (OAD) following lung transplantation.