Obliterative bronchiolitis after lung and heart-lung transplantation

An international collaborative pathologic study of surgical lung biopsies from mustard gas-exposed patients

BACKGROUND

Recent studies have shown strong evidence that bronchiolitis obliterans is the major long-term sequelae of exposure to sulfur mustard (SM). This study is the first to examine the histopathologic spectrum of changes in a large number of surgical lung biopsies from patients exposed to SM.

METHOD

Fifteen patients with chronic respiratory disease from mustard gas exposure were divided into severe (6 cases) and mild exposure (9 cases). All had surgical (open or thoracoscopic) lung biopsy, pulmonary function tests (PFTs) and chest high-resolution computed tomography scan (HRCT).

RESULT

The mean age of the cases was 43.8+/-9.6 (range 33-65). All patients had dyspnea and cough as the two main complaints. Only one patient was a smoker. Thirteen patients had normal PFTs, while one had obstruction and one had mild restriction. Six (66.6%) patients in the mild exposure and 3 (50%) in the severe exposure group showed evidence of more than 25% air trapping on chest HRCT. Among the mild group, 3 had features of constrictive bronchiolitis and another had features suggestive of this (bronchiolectasis and mucus stasis). The next most common finding was a mild-to-moderate chronic cellular bronchiolitis (3 patients). Two among the 6 in the severe group showed constrictive bronchiolitis and one showed features suggestive of constrictive bronchiolitis.

CONCLUSION

We conclude that about half of patients had diagnostic constrictive bronchiolitis, or bronchiolectasis and mucus stasis consistent with more proximal luminal compromise. The fact that there were no differences between the low- and high-dose groups suggests that effects of SM are not solely dependent on the severity of exposure. The results also indicate that the diagnosis of chronic lung disease due to SM may be difficult. Surgical lung biopsy may be helpful in difficult cases, as constrictive (obliterative) bronchiolitis can be present in symptomatic patients with normal PFTs and chest HRCT.

Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is a condition characterized by inflammation and fibrosis of the bronchiolar walls resulting in narrowing or obliteration of the bronchiolar lumen. The most common causes are childhood lower respiratory tract infection, hematopoietic stem cell or lung and heart-lung transplantation, and toxic fume inhalation. The most frequent clinical manifestations are progressive dyspnea and dry cough. Pulmonary function tests demonstrate airflow obstruction and air trapping. Radiographic manifestations include reduction of the peripheral vascular markings, increased lung lucency, and overinflation. The chest radiograph, however, is often normal. High-resolution CT is currently the imaging modality of choice in the assessment of patients with suspected or proven OB. The characteristic findings on high-resolution CT consist of areas of decreased attenuation and vascularity (mosaic perfusion pattern) on inspiratory scans and air trapping on expiratory scans. Other CT findings of OB include bronchiectasis and bronchiolectasis, bronchial wall thickening, small centrilobular nodules, and three-in-bud opacities. Recent studies suggest that hyperpolarized ³He-enhanced magnetic resonance imaging may allow earlier recognition of obstructive airway disease and therefore may be useful in the diagnosis and follow-up of patients with OB.

The value of D-dimer in lung transplant recipients with bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) following lung transplantation is common and potentially devastating. Its exact cause is undefined, but multiple immune and nonimmune processes contribute to its pathogenesis. The diagnosis of BOS syndrome is based on clinical presentation of progressive decline in the lung functions together with appropriate pathological findings. Severe acute rejection and recurrent acute rejection have been shown to confer the greatest risk for obliterative bronchiolitis, signifying the central importance of alloimmunity in the disease process. BOS is associated with activation of the coagulation system, and is a major cause of lung allograft loss. The aim of the study was to determine if there is an association between D-dimer levels and functional exercise capacity in lung transplant recipients with BOS. This prospective group comparison study was conducted at a tertiary-care, university-affiliated medical center. The sample included 46 patients (29%) who underwent lung transplantation between January 1997 and May 2006 and had positive findings on screening for BOS. Blood samples were collected for measurement of plasma D-dimer levels by the rapid MiniQuant assay. Correlational analysis was used to determine the association of D-dimer levels with demographic clinical data, pulmonary function, and functional exercise capacity parameters, including the 6-min walk test and cardiopulmonary exercise testing. D-dimer levels were associated with FEV1 (r=-0.43, p=0.001), 6-min walk test (r=-0.53, p=0.04), and VO2/kg/min (r=-0.36, p=0.04). No correlations were noted between D-dimer levels and total lung capacity, diffusion capacity, and oxygen saturation. On multivariate logistic regression, only FEV1 was a significant predictor of BOS (OR 0.885, CI: 0.812-0.965). We conclude that in lung transplant recipients with BOS, D-dimer levels are highly associated with functional exercise capacity and may serve as a useful marker for noninvasive monitoring. Further coagulation assays are needed to complete our observations.

Course of FEV(1) after onset of bronchiolitis obliterans syndrome in lung transplant recipients

RATIONALE

Bronchiolitis obliterans syndrome (BOS), defined by loss of lung function, develops in the majority of lung transplant recipients. However, there is a paucity of information on the subsequent course of lung function in these patients.

OBJECTIVES

To characterize the course of FEV(1) over time after development of BOS and to determine the predictors that influence the rate of functional decline of FEV(1).

METHODS

FEV(1)% predicted (FEV(1)%pred) trajectories were studied in 111 lung transplant recipients with BOS by multivariate, linear, mixed-effects statistical models.

MEASUREMENTS AND MAIN RESULTS

FEV(1)%pred varied over time after BOS onset, with the steepest decline typically seen in the first 6 months (12% decline; p < 0.0001). Bilateral lung transplant recipients had significantly higher FEV(1)%pred at BOS diagnosis (71 vs. 47%; p < 0.0001) and at 24 months after BOS onset (58 vs. 41%; p = 0.0001). Female gender and pretransplant diagnosis of idiopathic pulmonary fibrosis were associated with a steeper decline in FEV(1)%pred in the first 6 months after BOS diagnosis (p = 0.02 and 0.04, respectively). A fall in FEV(1) greater than 20% in the 6 months preceding BOS (termed "rapid onset") was associated with shorter time to BOS onset (p = 0.01), lower FEV(1)%pred at BOS onset (p < 0.0001), steeper decline in the first 6 months (p = 0.03), and lower FEV(1)%pred at 2 years after onset (p = 0.0002).

CONCLUSIONS

Rapid onset of BOS, female gender, pretransplant diagnosis of idiopathic pulmonary fibrosis, and single-lung transplantation are associated with worse pulmonary function after BOS onset.

Are heart-lung transplant recipients protected from developing bronchiolitis obliterans syndrome?

BACKGROUND

Heart-lung transplant recipients, when compared with heart transplant recipients, are relatively spared from allograft coronary artery disease. This study was undertaken to investigate whether heart-lung transplant recipients are also spared from experiencing bronchiolitis obliterans syndrome (BOS) when compared with double-lung transplant recipients. In addition, the risk factors for developing BOS after lung transplantation were analyzed.

METHODS

Heart-lung and bilateral sequential double-lung transplant recipients were reviewed retrospectively from 1990 to 2000 using the Stanford Transplant Database. The heart-lung transplant group consisted of 77 heart-lung transplant recipients and the double-lung transplant group consisted of 51 double-lung transplant recipients. The rates of BOS, survival, acute rejection, and cytomegalovirus infection at 1, 3, and 5 years were measured.

RESULTS

There were no significant differences in patient demographics between the two groups. Rates of survival and acute rejection were similar in the two transplant groups. The incidence of cytomegalovirus infection was significantly higher in heart-lung transplant recipients. Freedom from BOS was similar in the two transplant groups. Risk factors for the development of BOS in the heart-lung and double-lung transplant recipients included male donor, younger recipient age, a diagnosis other than cystic fibrosis, nonuse of cardiopulmonary bypass, and the use of OKT3 induction therapy.

CONCLUSIONS

Heart-lung transplant recipients exhibit BOS at a rate similar to double-lung transplant recipients. The immunoprotective effect the lung allograft presumably provides the heart is not reciprocated by the heart in preventing the development of BOS.

Heart and lung transplantation pathology: the Padua experience

Physicians caring for heart and lung transplantation patients utilize routine follow-up biopsies on a prearranged schedule unrelated to the suspicion of a clinical diagnosis of rejection. Of course biopsies are also performed outside the prearranged scheme at any time the clinician is puzzled by clinical suspicion of rejection or infections. Technical considerations are important in handling the biopsies; pathologists who are aware of bias produced by tissue processing are forced to serially section the samples to increase the sensitivity for detection of the pathological processes. During the 20 years since the first Italian cardiac transplantation was performed in our center, 600 patients have been transplanted and monitored with 12,386 endomyocardial biopsies. The overall 5-year mortality was 24.5% and 18.4% in pediatric populations; at 10 years, 34%, and at 19 years, 55%. There was a progressive decrease in mortality from 36.8% in 1985 to 1990 to 12% in the 1996 to 2000. During a decade of experience in lung transplantation from May 1995 to May 2005 (n = 129), all patients underwent surveillance bronchoscopy including transbronchial biopsy (n = 722) and bronchoalveolar lavage (n = 629). The ancillary techniques of immunohistochemistry and molecular analysis have allowed the pathologists to play a pivotal role in the pre- and posttransplant management of patients requiring thoracic organ transplantation.

Pirfenidone: anti-fibrotic agent with a potential therapeutic role in the management of transplantation patients

Pirfenidone has a simple chemical structure, but may have profound implications for transplantation management. One of the leading causes of allograft failure is chronic allograft dysfunction, manifested by chronic inflammation and chronic fibrosis [Estenne, M., Hertz, M.I., 2002. Bronchiolitis obliterans after human lung transplantation. AJRCCM. 166, 440-444.]. This review summarizes the literature to date on Pirfenidone in the setting of transplantation, and those studies pertinent to the mechanisms of organ rejection and possible use of Pirfenidone in transplantation patients.

Transcript signatures of lymphocytic bronchitis in lung allograft biopsy specimens

BACKGROUND

Rejection and obliterative bronchiolitis are barriers to sustained graft function in recipients of transplanted lungs. Early detection is hindered by inadequate tests and an incomplete understanding of the molecular events preceding or accompanying graft deterioration.

METHODS

Hypothesizing that genes involved in immune responses and tissue remodeling produce biomarkers of rejection, we measured the expression of 192 selected genes in 72 sets of biopsy specimens from human lung allografts. Gene transcripts were quantified using a 2-step, multiplex, real-time polymerase chain reaction approach in endobronchial and transbronchial biopsy specimens from transplant recipients without acute infections undergoing routine surveillance bronchoscopy.

RESULTS

Comparisons of histopathology in parallel biopsy specimens identified 6 genes correlating with rejection as manifested by lymphocytic bronchitis, a suspected harbinger of obliterative bronchiolitis. For example, beta2-defensin and collagenase transcripts in inflamed bronchi increased 37-fold and 163-fold, respectively. By contrast, these transcripts did not correlate with acute rejection in transbronchial specimens. Further, no correspondence was noted between histopathologic bronchitis and parenchymal rejection when endobronchial and transbronchial samples were obtained from the same patient.

CONCLUSIONS

Our highly sensitive method permits quantitation of many gene transcripts simultaneously in small, bronchoscopically acquired biopsy specimens of allografts. Transcript signatures obtained by this approach suggest that airway and alveolar responses to rejection differ and that endobronchial biopsy specimens assess lymphocytic bronchitis and chronic rejection but are not proxies for transbronchial biopsy specimens. Further, they reveal changes in airway expression of the specific genes involved in host defense and remodeling and suggest that the measurement of transcripts correlating with lymphocytic bronchitis may be diagnostic adjuncts to histopathology.

Long-Term Azithromycin Use for Treatment of Bronchiolitis Obliterans Syndrome in Lung Transplant Recipients

Short-term improvement in lung function was observed in 5 of 6 lung transplant recipients with bronchiolitis obliterans syndrome (BOS) who were treated with oral azithromycin. We assessed the long-term effect (mean duration 10 months) of treatment with oral azithromycin in 11 lung transplant recipients with BOS. Mean forced expiratory volume in 1 second (FEV1) was 40 +/- 9% at initiation of azithromycin treatment, 39 +/- 10% after 1 month, 39 +/- 12% after 4 months, 38 +/- 10% after 7 months and 38 +/- 10% after 10 months, respectively (statistically non-significant for all data). We conclude that long-term administration with oral azithromycin does not reverse BOS in lung transplant recipients, but may slow progression of the disease.

Bronchiolitis obliterans in children

Bronchiolitis obliterans (BO) in children is a relatively rare diagnosis. The increase in lung and bone marrow transplantation in children, however, has led to a heightened interest in BO, as this is one of the important complications of those procedures. This article will discuss BO as an entity that can follow any of several illnesses or toxic exposures, in addition to following allogeneic lung or bone marrow transplantation. The complex and incompletely understood pathology, pathogenesis, and molecular pathology involved in BO remain the subject of ongoing investigations. As the prognosis for BO is uncertain and treatment is often unsuccessful, the continued need for the recognition of surrogate markers for BO in patients at risk and the development of better forms of therapy are paramount. This review will describe our current understanding of BO, and will call attention to those research areas that require continuing efforts in order to prevent or treat this entity.

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.

Lung transplantation: A decade of experience

BACKGROUND

Over the past 3 decades, the field of lung transplantation has been refined. However, many barriers exist that limit long-term success. The purpose of this study was to review a single institution's long-term experience with single and double lung transplantation and to assess the effect of different immunosuppressive therapies on outcomes.

METHODS

Lung transplant recipients, both single and double, were reviewed, retrospectively. Patients were divided into five groups: group I, all lung transplants (n = 127); group II, single lung transplants (n = 73); group III, double lung transplants (n = 54); group IV, OKT3 induction therapy recipients (n = 27); and group V, RATG induction therapy recipients (n = 100). Rates of survival, rejection, bronchiolitis obliterans syndrome (BOS) and infection were analyzed at 1, 3, and 5 years.

RESULTS

There were no significant differences in survival, acute rejection rate, freedom from BOS, nor infection between single and double lung transplant recipients. Induction therapy with RATG (group V) was associated with significantly improved survival and freedom from acute rejection, BOS, and infection when compared to OKT3 induction therapy (group IV).

CONCLUSIONS

An earlier impression that RATG is superior to OKT3 induction therapy has borne true in terms of overall survival and incidence of BOS, acute rejection and infection rates. Lung transplantation, using RATG induction therapy, remains an important modality for end-stage pulmonary disease.

Overview of tacrolimus-based immunosuppression after heart or lung transplantation

Transplantation has evolved into an accepted treatment for end-stage heart or lung disease. Acute rejection, complications related to immunosuppressive protocols, and the development of chronic rejection continue to challenge the long-term success of heart and lung transplantations. Wide acceptance of tacrolimus as an important immunosuppressant in renal and hepatic transplantations has led subsequently to its investigation as primary immunosuppression in heart and lung transplant recipients, either combined with azathioprine or with the newer agents mycophenolate mofetil or rapamycin. Studies have shown that tacrolimus is an effective therapeutic alternative to cyclosporine for primary immunosuppression in heart or lung transplantation and demonstrates equivalent if not improved prophylaxis of acute rejection, and more recently demonstrates a potential influence on chronic rejection, particularly in lung transplant recipients. Of importance, the enhanced immunosuppressive activity of tacrolimus is achieved without increased risk of infection or malignancy. Differences in tolerability profiles and side effects between tacrolimus and cyclosporine may be used in selecting the optimal immunotherapy after thoracic transplantation. In particular, the lesser propensity of tacrolimus to cause hypertension and hyperlipidemia potentially offers decreased cardiovascular risk for heart and lung transplant recipients.

HLA-specific antibodies are risk factors for lymphocytic bronchiolitis and chronic lung allograft dysfunction

Bronchiolitis obliterans syndrome (BOS) represents a major limitation in lung transplantation. While acute rejection is widely considered the most important risk factor for BOS, the impact of HLA-specific antibodies is less understood. Of 51 lung recipients who were prospectively tested during a 4.2 +/- 1.6-year period, 14 patients developed HLA-specific antibodies. A multi-factorial analysis was performed to correlate the prevalence of BOS with HLA antibodies, persistent-recurrent acute rejection (ACR-PR), lymphocytic bronchiolitis, and HLA-A, -B, and -DR mismatches. HLA-specific antibodies were associated with ACR-PR (10/14 vs. 11/37 with no antibodies, p < 0.05), lymphocytic bronchiolitis (8/14 vs. 10/37, p < 0.05), and BOS (10/14, vs. 9/37, p < 0.005). Other risk factors for BOS were: lymphocytic bronchiolitis (13/18 vs. 6/33 with no lymphocytic bronchiolitis, p < 0.0001), ACR-PR (12/21 vs. 7/30 with no ACR-PR, p < 0.05), and the number of HLA-DR mismatches (1.7 +/- 0.48 in BOS vs. 1.2 +/- 0.63 without BOS, p < 0.05). The presence of antibodies exhibited a cumulative effect on BOS when it was associated with either lymphocytic bronchiolitis or ACR-PR. The complex relationship between the development of HLA antibodies and acute and chronic lung allograft rejection determines the importance of post-transplant screening for HLA-specific antibodies as a prognostic element for lung allograft outcome.

Accuracy of exhaled nitric oxide measurements for the diagnosis of bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

Exhaled nitric oxide (eNO) is increased in patients with bronchiolitis obliterans syndrome (BOS) after lung transplantation. However, the accuracy of eNO measurements in diagnosing BOS is unknown.

METHODS

Thirty-two lung-transplant patients were included. Their immunosuppressive regimen consisted of cyclosporin A (tacrolimus), azathioprine (mycophenolate mofetil), and oral but no inhaled steroids. eNO levels and spirometry were prospectively followed until 2 years after transplantation or until the patient developed BOS.

RESULTS

Thirteen patients (group A) developed BOS (607 +/- 158 days after transplantation). Their mean eNO level at that time was 24.3 +/- 13.2 parts per billion (ppb), whereas the eNO value in the stable patients at 2 years (group B) was 11.4 +/- 4.9 ppb, P=0.0054. All group A patients had an eNO of 15 or greater ppb. Seven patients of group B also had an eNO of 15 or greater ppb, resulting in a test accuracy for the diagnosis of BOS of 0.78. However, considering only those patients who had two consecutive measurements (3-6 weeks apart) of eNO 15 or greater ppb during the months preceding the diagnosis of BOS or in the whole 2-year evaluation period, only 3 of 19 patients in group B (false-positives) but 12 of 13 in group A (1 false-negative) now fulfilled that criteria, which became positive at a mean of 263 +/- 169 days before the diagnosis of BOS was met, based on the forced expiratory volume in 1 second criteria. This increased the accuracy to 0.88.

CONCLUSION

Measurements of eNO appear to be an accurate test for the early diagnosis of BOS.

Anti-allergic agent tranilast decreases development of obliterative airway disease in rat model of heterotopic tracheal transplantation

BACKGROUND

Tranilast is an anti-allergic agent known to inhibit the release of histamine, interleukin-1beta, transforming growth factor beta1, and platelet-derived growth factor from various cells and currently is used to treat allergic diseases, keloids, and hypertrophic scars. We evaluated the ability of tranilast to inhibit the development of obliterative airway disease (OAD) in a rat model of heterotopic tracheal transplantation.

METHODS

We transplanted tracheal segments from donor rats (Brown Norway) into subcutaneous pouches in major histocompatibility complex-incompatible recipient rats (Lewis). At Days 21 and 28 after transplantation, we histologically assessed the harvested allografts scored the degree of OAD, on a scale from zero to 4 as previously described, caused by fibroproliferative tissue.

RESULTS

Recipient animals treated orally with 400 mg/kg/day tranilast throughout the experiment showed significantly decreased OAD compared with control animals, with a histologic score of 1.1 +/- 0.4 vs 3.0 +/- 1.3, respectively (mean +/- SD, p=0.007), at Day 21 after transplantation and 2.0 +/- 1.4 vs 3.9 +/- 0.4, respectively (mean +/- SD, p=0.017), at Day 28 after transplantation.

CONCLUSION

These results showed that treatment with tranilast significantly decreased fibroproliferative airway changes associated with allograft rejection in a rat model of tracheal transplantation, suggesting that tranilast may be useful in preventing bronchiolitis obliterans after lung transplantation.

The effects of pretreatment with donor antigen and immunosuppressive agents on fully allogenic tracheal graft

BACKGROUND

Obliterative bronchiolitis is a major clinical problem in cases involving a transplanted lung. We examined drug-induced tolerance to a fully allogenic tracheal graft in a murine heterotopic transplantation model.

MATERIALS AND METHODS

Recipient mice (C57BL/6) were primed iv with 1 x 10(8) splenocytes of donor mice (BALB/c). Day 0 was the day of the splenocyte injection. Cyclophosphamide and Busulfan were injected intraperitoneally on day 2. On day 3, 1 x 10(7) donor bone marrow cells were intravenously injected. On day 28, a donor tracheal graft was implanted into a subcutaneous pocket. Grafts were harvested at 3-week intervals, and the degree of obstruction of the inner cavity, the condition of epithelium, and the viability of chondrocytes were examined.

RESULTS

All of the isograft controls (BALB/c) and grafts implanted in the T cell-free recipients (BALB/c-nu) showed patent, lined epithelium and viable chondrocytes. All allografts tested showed total luminal occlusion by granulative tissue and inflammatory cells, and the epithelium was totally absent. Five of 11 drug-treated grafts were completely patent, although the epithelium was almost absent and the chondrocytes were substantially destroyed. However, when the chimerism was analyzed by flow cytometry analysis of the recipient T cells, approximately 90% of the donor cells were recognized.

CONCLUSIONS

Even by this pre-treatment-induced chimerism, a transplanted allogenic trachea was not completely preserved. The present results suggest that a non-allogenic response might have contributed to the rejection.

Cyclooxygenase-2 expression in experimental post-transplant obliterative bronchiolitis

Epithelial cell injury, inflammation, progressive fibrosis, and airway obliteration are histological features of post-transplant obliterative bronchiolitis (OB). Cyclooxygenase (COX)-2 is expressed in acute and chronic inflammatory responses. Our aim was to elucidate the possible role of COX-2 in post-transplant OB by using a heterotopic bronchial porcine model. Bronchial allografts from non-related donors were transplanted subcutaneously into 24 random-bred domestic pigs, each weighing about 20 kg. Groups studied had grafts, non-treated allografts, allografts given cyclosporine A (CsA), methylprednisolone (MP), and azathioprine (Aza), and allografts given CsA, MP, and everolimus. Grafts were serially harvested during a follow-up period of 21 days for histology (H&E) and immunohistochemistry. Immunostaining was performed with monoclonal IgG against human COX-2 peptide, and histological alterations and immunohistochemical positivity were graded on a scale from 0 to 5. Epithelial COX-2 index was calculated by multiplying the percentage of positive cells by grade of epithelial COX-2 intensity. Ischaemic epithelial loss, evident in all implants, recovered rapidly in autografts, and bronchi remained patent. Epithelial loss in non-treated allografts preceded fibroblast proliferation, resulting in total luminal obliteration. In CsA-, MP-, and Aza-treated allografts epithelial destruction and luminal obliteration were delayed, and these were prevented in CsA-, MP-, and everolimus-treated allografts. COX-2 expression due to operative ischaemia was evident in all implants on day 2. Thereafter, the epithelial COX-2 index preceded epithelial injury and obliteration. During the inflammatory response and fibroblast proliferation, COX-2 expression occurred in macrophages and fibroblasts. In conclusion, in the early stage of OB development, COX-2 induction occurred in airway epithelial cells prior to luminal obliteration. In addition, the observation that COX-2 expression in macrophages and fibroblasts paralleled the onset of inflammation and fibroblast proliferation indicates a role in OB development, but the causal relationships need further study.

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.

Pirfenidone inhibits obliterative airway disease in a murine heterotopic tracheal transplant model

BACKGROUND

Chronic lung allograft rejection in the form of bronchiolitis obliterans syndrome and its histopathologic correlate, obliterative bronchiolitis (OB), are a major source of morbidity and mortality after lung transplantation. Murine heterotopic tracheal transplants into fully allogeneic mismatched recipients develop obliterative airway disease (OAD), which is a suitable model of OB. Using this murine heterotopic tracheal allograft model, we evaluated the effect of pirfenidone, a novel antifibrotic agent, on the development of OAD.

METHODS

Mice transplanted with complete MHC-mismatched tracheal allografts received pirfenidone (0.5%) in pulverized food according to different schedules: daily for the first 14 days after transplantation or daily for the duration of the study beginning on posttransplantation days 0, 5, or 10.

RESULTS

Mice on a continuous daily regimen of pirfenidone failed to develop evidence of chronic allograft rejection at the termination of the study (60 days). Mice receiving pirfenidone limited to the early posttransplantation period had delayed onset of OAD to 60 days. Forty percent (2/5) of mice receiving a continuous regimen of pirfenidone beginning on day 5 after transplantation had no evidence of OAD at 28 days. However, when the drug was started on day 10, all mice developed OAD by 28 days.

CONCLUSIONS

Our results demonstrate a delay of onset or abrogation of OAD when pirfenidone is administered in the early posttransplantation period. These findings suggest that pirfenidone is a candidate drug to be evaluated for prevention of the fibrotic changes seen in OB in human recipients of lung transplants.

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.

Increased matrix metalloproteinase-2 and membrane type 1 matrix metalloproteinase activity and expression in heterotopically transplanted murine tracheas

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the most common long-term cause of morbidity and mortality after heart-lung or lung transplantation. One pathologic feature of BOS is infiltration of fibroblasts and connective tissue products into the airway lumen, which form a fibrous, collagen-rich occlusion. Heterotopically transplanted allogeneic murine tracheal stenosis resemble BOS in the development of obliterans airway disease. Matrix metalloproteinases (MMPs) are key enzymes involved in tissue remodeling and, clinically, have several roles in pulmonary diseases. Among the MMP family, type IV collagenases, MMP-2 and MMP-9, have high gelatinolytic activity and are thought to play a role in several pulmonary diseases. Membrane type 1 MMP (MT1-MMP) activates the zymogen of MMP-2 (proMMP-2, 72 kd), and activated MMP-2 (active MMP-2, 62 kd) degrades type IV collagen and plays an important role in clinical pulmonary disease. In this study, we examine the expression of MMP-2, its activator MT1-MMP and MMP-9 in BOS using murine trachea transplantation models.

METHODS

Rats were divided into 5 experimental groups (n = 10 in each group). Group I was a control group with intact tracheas. Animals with tracheal grafts underwent heterotopically syngeneic (Groups II and III) or allogeneic (Groups IV and V) transplantation. The recipient rats were killed 7 days (Groups II and IV) or 28 days (Groups III and V) after transplantation. The harvested tracheal grafts were examined histologically. MMP activity was assessed using gelatin zymography analysis, and MMP-2 and MT1-MMP gene expression was examined by quantitative real-time polymerase chain reaction analysis. Distribution of gelatinolytic activity was studied using in situ zymography.

RESULTS

There was little histologic change in the intact trachea (Group I) and in all isografts (Groups II and III). Fibrotic tissues in Group V significantly occluded the tracheal lumen, and there was severe lymphocyte infiltration in Group IV. According to gelatin zymography, proMMP-9 was faint at 7 days, but activated MMP-9 was not present in all groups. The MMP-2 gelatinolytic bands were predominant; the activation in Group V was significantly greater than that in Group IV, and in Group III it was significantly greater than that in Group II. Gene expression of both MMP-2 and MT1-MMP were significantly higher in Group V than in the other groups (p < 0.01), and MMP-2 was clearly activated. Gelatinolytic activity was localized in the fibrotic tissues or lymphocytes of thickening lumen after destruction of the epithelium by stenosis.

CONCLUSIONS

These results demonstrate that MMP-2, together with its activator MT1-MMP, may have an important role in the development of BOS, which is associated with destruction of the tracheal epithelium, leading to fibrosis.

Reduction of recipient macrophages by gadolinium chloride prevents development of obliterative airway disease in a rat model of heterotopic tracheal transplantation

BACKGROUND

Recent studies have shown the possible role of growth factors and the involvement of macrophages as a source of them in the pathogenesis of bronchiolitis obliterans (BO) after lung transplantation.

OBJECTIVE

The authors intended to determine whether depletion of recipient macrophages by gadolinium chloride (GdCl3) resulted in decreased obliterative airway disease (OAD) in a rat model of heterotopic tracheal transplantation.

METHODS

A tracheal segment of donor rats (Brown Norway) was transplanted into a subcutaneous pouch of fully major histocompatibility complex-incompatible recipient rats (Lewis). Recipients were injected intravenously with 80 mg/kg of GdCl3.6H2O or saline on days 0, 7, and 14 posttransplant. Allografts were harvested on days 7, 14, 17, and 21 and the degree of OAD resulting from fibroproliferative tissue was pathologically scored on a scale of 0 to 4. A portion of allografts was submitted to reverse-transcriptase polymerase chain reaction analysis to examine mRNA expression for platelet-derived growth factor (PDGF), basic fibroblast growth factor, and transforming growth factor-beta1.

RESULTS

Immunohistochemical studies confirmed reduction in the number of ED2+ macrophages in tracheal allografts by GdCl3 injection. GdCl3 treatment significantly decreased OAD of allografts, with the histologic score of 1.4+/-0.3 in the treated animals compared with 3.0+/-0.5 in the controls (mean+/-SE, P=0.02) at day 21 posttransplant, and this was accompanied by decreased PDGF-A and PDGF-B gene expression in the GdCl3 group at day 17 posttransplant.

CONCLUSIONS

Macrophage reduction by GdCl3 resulted in significantly decreased OAD development and reduced PDGF mRNA expression in allografts. This suggests a potential effectiveness of therapies targeting recipient macrophages in preventing BO after lung transplantation.

The role of the beta chemokines in experimental obliterative bronchiolitis

Beta chemokines have been implicated in cardiac and renal allograft rejection. This study determined if antibody antagonization of beta chemokines conferred protection against the development of experimental obliterative bronchiolitis (OB) in a heterotopic rat tracheal allograft model. Rat tracheas were transplanted from Brown-Norway or Lewis donors into Lewis recipients. Rats received 200 microg/day of either anti-RANTES or anti-MCP-1 antibody for 14 days. Luminal obstruction and epithelial loss were calculated. Northern blots for MCP-1 and RANTES mRNA expression were performed, and immunohistochemistry for chemokine protein localization. There was a significant increase in airway obstruction in allografts compared to isografts (P < 0.001). Antibody-treated allografts demonstrated an amelioration of airway obstruction from 58% (vehicle allografts) to 26% (anti-RANTES) and 12% (anti-MCP-1), both of which were significant (P < 0.001). Epithelial preservation was increased in both antibody-treated groups (P < 0.001), and increased expression of MCP-1 and RANTES mRNA was present in tracheal allografts by Day 2 and maximal by Day 6. Beta chemokines are expressed during the development of experimental OB, as MCP-1 and RANTES mRNA expression increased with time from transplantation. Both MCP-1 and RANTES are functional in the formation of the fibroproliferative response that characterizes OB in this model, and their antagonization conferred protection against airway obstruction and epithelial loss.

Enhanced peroxynitrite decomposition protects against experimental obliterative bronchiolitis

Obliterative bronchiolitis (OB) affects over half of all survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular tissue causing airway occlusion characterize the lesion. While peroxynitrite is known to participate in other models of acute lung injury, its role in the evolution of OB is unclear. Using a rat model of experimental OB, tracheas from Brown-Norway or Lewis rats were transplanted into Lewis recipients. Treated animals received FP-15, a peroxynitrite decomposition catalyst, at 1 mg/kg/day intraperitoneal for 14 days. Luminal obstruction, epithelial loss, and inflammatory infiltrate were examined, as was nitrotyrosine staining by immunohistochemistry in explanted tracheas. By postoperative day 14, control allografts demonstrated marked peribronchial inflammation, near complete loss of respiratory epithelium and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 83% reduction in airway cross-sectional area. Allograft recipients treated with FP-15 showed reduced nitrotyrosine formation, preservation of respiratory epithelium, limited peribronchial inflammation, and only 14% (P <.001) reduction in airway cross-sectional area. Peroxynitrite therefore appears to play a role in the development of obliterative bronchiolitis in rats. The peroxynitrite decomposition catalyst, FP-15, is protective when administered daily and warrants investigation into its potential clinical utility.

Bronchiolitis obliterans syndrome

BOS remains a difficult problem to control following lung transplantation, largely because of uncertainties regarding the underlying mechanisms that are responsible for it. Continued work on the pathogenesis of BOS is essential. The progressive nature and poor outlook when BOS stage 3 is reached indicates that current strategies should be focused on prevention and early intervention. There is a great need for randomized, controlled trials on intervention if the international transplant community is to make progress in this area.

Maintenance azithromycin therapy for bronchiolitis obliterans syndrome: results of a pilot study

Bronchiolitis obliterans syndrome remains the leading cause of morbidity and mortality in the pulmonary transplant population. Previous studies show that macrolide antibiotics may be efficacious in the treatment of panbronchiolitis and cystic fibrosis. In the latter, azithromycin decreases the number of respiratory exacerbations, improves FEV1, and improves quality of life. We hypothesized that oral azithromycin therapy may improve lung function in patients with bronchiolitis obliterans syndrome. To test this hypothesis, we conducted an open-label pilot trial using maintenance azithromycin therapy in six lung transplant recipients (250 mg orally three times per week for a mean of 13.7 weeks). In this study, five of these six individuals demonstrated significant improvement in pulmonary function, as assessed by FEV1, as compared with their baseline values at the start of azithromycin therapy. The mean increase in the percentage of predicted FEV1 values in these individuals was 17.1% (p </= 0.05). In addition, the absolute FEV1 increased by 0.50 L (range -0.18 to 1.36 L). These data suggest a potential role for maintenance macrolide therapy in the treatment of bronchiolitis obliterans syndrome in lung transplant recipients.

Broad-spectrum chemokine inhibition ameliorates experimental obliterative bronchiolitis

BACKGROUND

Obliterative bronchiolitis (OB) affects over half of all long-term survivors after lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular connective tissue causing airway occlusion characterize this lesion. Several chemokines participate in experimental OB, and singular blockade is only partially effective. We hypothesized that a broad-spectrum chemokine inhibitor would be an effective intervention in preventing the progression of OB in an established heterotopic tracheal transplantation model.

METHODS

Tracheas from Brown-Norway or Lewis rats were transplanted subcutaneously into Lewis recipients. Treated, allogeneic recipients received either a broad-spectrum chemokine inhibitor in its active (NR58.3.14.3) or inactive (NR58.3.14.4) form at a dose of 30 mg/kg daily. Luminal obstruction, epithelial loss, leukocytic infiltrates, and inflammatory cytokine mRNA levels were assessed in explanted tracheal samples 14 days after transplantation.

RESULTS

After 14 days, allografts receiving the inactive chemokine inhibitor demonstrated marked peribronchial inflammation, near complete loss of respiratory epithelium, and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 84% +/- 5% reduction in airway lumen cross-sectional area. Isografts showed limited inflammation, with minimal loss of epithelium and luminal occlusion. Allogeneic recipients treated with the active chemokine inhibitor showed a significant preservation of respiratory epithelium, minimal peribronchial inflammation, and a marked decrease in the loss of airway cross-sectional area (23% +/- 1%) (p < 0.001).

CONCLUSIONS

These findings further characterize the participation of chemokines in OB, and suggest that broad-spectrum chemokine inhibition may potentially be a useful therapeutic tool in slowing the progression of this disease.

Pirfenidone: A novel anti-fibrotic agent and progressive chronic allograft rejection

In our established model of heterotopic tracheal transplantation, at day 28 following transplantation, obliteration of the lumen is observed, which is histologically similar to that seen in Obliterative Bronchiolitis (OB). Pirfenidone (Pir) is a novel anti-fibrotic agent that causes no immunosuppression, but does downregulate the production of TGF-beta and collagen in vitro. We hypothesized that when used in this in vivo model, that Pir may alter the observed luminal fibrosis and obliteration.

METHODS

The treatment groups were: CSA, Pir and CSA, Pir only (n=6 each). Luminal supernatants and tissue were obtained from these groups at day 28. H&E staining was completed, as well as MTS proliferation assays, and TGF-beta ELISA on the fluids.

RESULTS

The CSA-Pir combined treatment group was the least fibrogenic in vitro (p<0.001). The TGF-beta levels were elevated in all groups (range 203-372 pg/ml). The H&E staining revealed that the luminal obliteration was less organized in the combined CSA-Pir group.

CONCLUSIONS

Our study shows that the combination of CSA-Pir results in a less fibrogenic luminal fluid and a less dense fibrous luminal plug. Pir should be further studied in obliterative airways disease (OAD).

Respiratory failure and sepsis are the major causes of ICU admissions and mortality in survivors of lung transplants

STUDY OBJECTIVE

To identify outcome predictors and prognostic factors in long-term survivors (> 30 days post-transplant) of single-lung and double-lung transplants on readmission to the medical ICU (MICU).

DESIGN

Retrospective study.

SETTING

MICU of the Cleveland Clinic Foundation, a lung transplantation center.

PATIENTS

As of August 2000, 210 lung transplantations have been performed at our institution. The records of 33 lung transplant recipients who required readmission to the MICU after the initial 30-day post-transplant period over a 4-year period from August 16, 1996 to August 15, 2000 were reviewed.

RESULTS

Thirty-three patients had a total of 46 MICU readmissions. Twenty-seven MICU admissions (59%) were due to respiratory deterioration with mechanical ventilation (10 deaths), and 16 MICU admissions (35%) were due to the systemic inflammatory response syndrome (SIRS; 8 deaths). The MICU mortality rate was 37% per admission in our group of patients. A preadmission diagnosis of bronchiolitis obliterans syndrome was observed in 7 of 14 nonsurvivors (50%) and in 5 of 25 patients (20%) surviving to hospital discharge.

CONCLUSIONS

Respiratory failure and SIRS are the predominant causes of MICU readmissions and are frequent causes of death. APACHE (acute physiology and chronic health evaluation) III scores, nonpulmonary organ system dysfunction, initial serum albumin level, and duration of mechanical ventilation are important prognostic factors.

Regulatory role of IL-10 in experimental obliterative bronchiolitis in rats

Obliterative bronchiolitis (OB) affects over half of all chronic human survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular connective tissue causing airway occlusion characterize this lesion. Using a rat model of experimental OB, tracheas and mainstem bronchi from Brown-Norway or Lewis (LEW) rats were transplanted subcutaneously into LEW recipients. At 7 days, airway lumens of allografts showed minimal luminal obstruction but significant respiratory epithelial loss. By 14 days, allografts demonstrated marked peribronchial inflammation, nearly complete loss of respiratory epithelium, and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 58% reduction in airway cross-sectional diameter. However, isografts showed only limited peribronchial inflammation and no loss of airway lumen. When recipients of allotransplants were treated with anti-IL-10, OB developed more rapidly. As early as 7 days, there was marked histologic evidence of OB and a 43% reduction in mean cross-sectional area. Allograft animals that received 5 microg/day of recombinant IL-10 as a constant infusion on day 14 showed almost complete preservation of respiratory epithelium and only mild peribronchial inflammation with only a 15% reduction in airway cross-sectional area. These findings suggest that endogenous IL-10 plays a regulatory role in the development of experimental OB.

Non-immune acute graft injury after lung transplantation and the risk of subsequent bronchiolitis obliterans syndrome (BOS)

BACKGROUND

Primary graft dysfunction remains a major cause of early morbidity and mortality after lung transplantation. Evidence from animal models shows acute non-immune lung injury increases organ immunogenicity by enhancing MHC Class II expression. We hypothesized that acute non-immune injury in the lung allograft may impact, not only on early survival, but also on longer term survival by increasing the incidence of bronchiolitis obliterans syndrome (BOS).

METHODS

A single-center, retrospective, observational study in a population of over 320 lung transplant recipients was undertaken. The histologic diagnosis of diffuse alveolar damage (DAD) in an early graft biopsy was used to define those recipients at risk. Serial measurements of forced expiratory volume in 1 second (FEV(1)) in long-term follow-up defined the incidence of BOS.

RESULTS

Early graft biopsy was available in 291 of the recipients following transplantation. DAD was confirmed in 55 (19%); their 30-day survival (62.5%) was significantly worse than in recipients without DAD (87.5%; p < 0.0001, chi-square test). When 30-day deaths were excluded, however, there was no difference in survival between recipients with and without DAD (hazards ratio 0.69 [0.37 to 1.3]; p = 0.25, Wilcoxon's survival analysis). The incidence of subsequent BOS over the follow-up period was not significantly different in those with and without DAD on early biopsy at 46% and 59%, respectively (hazards ratio 0.88 [0.48 to 1.62]; p = 0.22, chi-square test). BOS did not occur any earlier in the DAD group (median 953 days, range 152 to 1,393) days compared with the non-DAD group (median 665 days, range 52 to 4,299) (p = 0.48, Fisher's exact test).

CONCLUSIONS

The development of severe non-immune acute graft injury after lung transplantation has a poor early prognosis. However, recipients with non-immune acute graft injury who survive >30 days show no significant difference in long-term survival or BOS-free time compared with recipients without early injury.

Is transplant operation important in determining posttransplant risk of bronchiolitis obliterans syndrome in lung transplant recipients?

STUDY OBJECTIVES

Lung transplantation continues to be limited by the development of chronic allograft dysfunction in the form of bronchiolitis obliterans syndrome (BOS). The effect of a transplant operation on patients with BOS has not been well-studied, but patients who undergo double-lung transplantation have better long-term survival. We hypothesized that double-lung transplantation leads to decreased rates of BOS.

METHODS

A retrospective review of all lung transplant recipients at our institution, surviving for > 6 months after undergoing their transplant operation. Demographic data, information on other factors leading to the development of BOS, survival information, and data on the presence and timing of BOS were collected.

RESULTS

BOS occurred in 41.3% of the recipients (93 of 225 patients) at a median time of 4.2 years. Single-lung transplantation was associated with increased rates of BOS compared to double-lung transplantation (49.3% vs 31.7%, respectively; p = 0.007), at the time of the analysis. Single-lung and double-lung transplant recipients had different baseline characteristics, but after controlling for these factors the type of transplant remained a significant predictor of the length of time to the onset of BOS in a multivariable proportional hazard model.

CONCLUSIONS

Double-lung transplantation is associated with a reduced risk for BOS in our study population. A multicenter study with complete BOS information on all patients with a single pretransplant diagnosis would be useful to confirm the above findings. Further research is needed to determine how the type of transplant contributes to the risk for BOS.

Epithelial kinetics in mouse heterotopic tracheal allografts

Obliterative bronchiolitis (OB) is the most important cause of graft dysfunction post-lung transplantation. It is likely that the small airway epithelium is a target of the alloimmune response, and that epithelial integrity is a crucial determinant of airway patency. Our goals are to elucidate epithelial cell kinetics in the heterotopic mouse trachea model and to determine potential mechanisms of cell death in allografts. Allografts and isografts were obtained by transplanting BALB/c tracheas into C57BL/6 and BALB/c immunosuppressed and non-immunosuppressed hosts, respectively and harvested from day 3-20. Morphometry, BrdU and TUNEL labeling, and EM studies were performed. Columnar epithelium in isografts and allografts sloughs during day 0-3, but regenerates in both sets of grafts by day 10. Subsequently, allografts become inflamed and denuded, while isografts retain an intact epithelium. Prior to airway denudation, allografts exhibited significantly increased epithelial cell density, BrdU labeling index (LI), and TUNEL positive cells. Epithelial apoptosis was confirmed by electron microscopy. Allograft percent ciliated columnar epithelium and lumenal circumference were significantly decreased. Cyclosporin delayed airway fibrosis but did not alter the progression of the allograft through the phases of early ischemic injury, airway epithelial cell regeneration, and eventual cell death. These studies quantitatively demonstrate that the allograft epithelium actively regenerates in the alloimmune environment, but succumbs to increased apoptotic cell death, underscoring the importance of the airway epithelium as a self-renewing source of alloantigen.

Induction therapy in lung transplantation: a prospective, controlled clinical trial comparing OKT3, anti-thymocyte globulin, and daclizumab

BACKGROUND

Because acute rejection is associated with inferior outcomes in lung transplantation, we have routinely employed OKT3, anti-thymocyte globulin (ATG), or daclizumab as adjuncts to reduce rejection.

METHOD

We performed a 4-year prospective, controlled clinical trial of these 3 therapies to determine differences in post-operative infection, rejection, survival, and bronchiolitis obliterans syndrome (BOS). Eighty-seven consecutive lung transplant patients received OKT3 (n = 30), ATG (n = 34), and daclizumab (n = 23) as induction agents. The groups had similar demographics and immunosuppression protocols differing only in induction agents used.

RESULTS

No differences were observed in immediate post-operative outcomes such as length of hospitalization, ICU stay, or time on ventilators. Twelve months post-transplant, OKT3 had more infections per patient than the other agents, a difference that only became significant 2 months post-operatively (p = 0.009). The most common infection was bacterial and OKT3 had more bacterial infections than any other agent. Daclizumab had more patients remain infection free in the first year (p = 0.02), having no fungal infections and a low rate of viral infections. No patient receiving daclizumab developed drug specific side-effects. Only those patients with episodes of acute rejection developed BOS. There were no significant differences in the freedom from acute rejection or BOS between the groups. The 2-year survival for the entire cohort was 68%, with no differences observed in patient survival.

CONCLUSIONS

This study again reveals the importance of acute rejection in the subsequent development of BOS. Although daclizumab offers a low risk of post-transplant infection and drug specific side-effects, no drug is superior in delaying rejection or BOS or in prolonging long-term survival.

Collagens I and III in a porcine bronchial model of obliterative bronchiolitis

The main extracellular matrix components of the lung, type I and III collagens, were studied in chronic allograft rejection developing in a porcine heterotopic bronchial transplantation model. Specific porcine complementary DNA probes were constructed for detection of the expression of type I and III procollagen messenger RNAs in the bronchial wall structures and in the obliterative plug by in situ hybridization. In autografts, and in allografts immunosuppressed with 40-O-(2-hydroxyethyl)-rapamycin, cyclosporine A, and methylprednisolone, no histological changes of obliterative bronchiolitis (OB) developed, and the number of fibroblast-like cells expressing type I and III procollagen mRNA remained low. In nontreated allografts obliterating within 21 d, a preponderance of fibroblast-like cells showing positivity for type III procollagen mRNA existed in the obliterative plug and bronchial wall. This study shows for the first time the temporal and spatial activation of type I and III procollagen genes during the course of obliterative bronchiolitis. The number of cells expressing procollagen III mRNA increased parallel to developing obliteration and fibrosis in nontreated allografts, whereas autografts and immunosuppressed allografts exhibited no such trend. This finding suggests a positive association between type III collagen mRNA expression in fibroblast-like cells and development of obliterative bronchiolitis.

The role of neutrophils in the pathogenesis of obliterative bronchiolitis after lung transplantation

Obliterative bronchiolitis (OB) represents the most important long-term complication after lung transplantation. Elevated numbers of neutrophils within the airways are a hallmark of OB. It is unclear what causes the recruitment and activation of neutrophils in the airways of patients with OB: the process of chronic rejection itself or infection, which may (especially in latent virus infection) often be overlooked by the currently applied diagnostic procedures. It is well known that besides their physiologic functions in the clearance of invading micro-organisms, activated neutrophils have a remarkable potential to cause damage to lung tissue. This is attributable to their capability to generate reactive oxygen species and to release potentially toxic proteases. It has been shown that the increased numbers of neutrophils in bronchoalveolar lavage fluid of patients with bronchiolitis obliterans syndrome (BOS) after lung transplantation are associated with elevated levels of interleukin-8, the predominant neutrophil chemotactic factor in the lung. As evidence for the impact of neutrophils on the pathogenesis of BOS, there is significant oxidative stress within the airways of patients with BOS. In addition, the milieu within the airways is characterized by an imbalance between neutrophil elastase (NE) and molecules that inhibit NE as a result of an increased burden of NE released by neutrophils. A defective antiprotease shield due to the loss of secretory leukoprotease inhibitor could be demonstrated in BOS. These mechanisms may provide possible targets to develop new therapeutic strategies that either prevent neutrophil sequestration and activation, or inhibit neutrophil products in order to prevent or attenuate airway damage.

Prolonged inhibition of obliterative airway disease in murine tracheal allografts by brief treatment with anti-leukocyte function-associated antigen-1 (CD11a) monoclonal antibody

BACKGROUND

We have previously shown that anti-leukocyte function-associated antigen (LFA)-1 (CD11a) monoclonal antibody (mAb) prevents acute rejection and produces donor-specific unresponsiveness in murine recipients of heterotopic heart allografts. Here, we investigate the ability of this mAb to prevent the development of obliterative airway disease (OAD) in murine recipients of tracheal allografts.

METHODS AND RESULTS

BALB/c tracheae were heterotopically transplanted into C3H mice. OAD developed by day 28 after transplantation and was characterized histologically by a loss of epithelial cell coverage and luminal obliteration of the tracheal allograft with a proliferation of fibrogenic mesenchymal cells, which is a lesion comparable to obliterative bronchiolitis in human lung transplant recipients. Monotherapy with anti-LFA-1 mAb preserved graft epithelium, prevented the development of OAD, and maintained unresponsiveness to donor antigen for more than 42 days after the final mAb administration.

CONCLUSION

These findings suggest the potential for anti-LFA-1 mAb therapy to suppress both acute and chronic rejection in clinical lung transplantation.

Azathioprine withdrawal in stable lung and heart/lung recipients receiving cyclosporine-based immunosuppression

BACKGROUND

Chronic rejection is the leading cause of graft failure after (heart-) lung transplantation. Therefore, many centers maintain a triple immunosuppressive cyclosporine-based regimen including azathioprine (AZA) during the long-term course after lung transplantation. However, an increased risk of malignancies has been attributed to prolonged immunosuppression, and there is evidence that less intensive immunosuppressive regimens are feasible in the long-term course after other solid organ transplantation. Therefore, we investigated the effects of AZA withdrawal in stable lung transplant recipients.

METHODS

A prospective study was performed to assess the effects of AZA withdrawal in patients who received a lung transplant more than 4 years ago with stable graft function defined by absence of rejection episodes for at least 2 years and no evidence of bronchiolitis obliterans.

RESULTS

A total of 24 patients qualified for the study and 7 discontinued AZA. Despite the small number of patients, termination of the study became necessary after 12 months because significantly more grafts showed deteriorating function after withdrawing AZA (4 of 7) compared to recipients continuing a triple therapy (1 of 17; P<0.05). In recipients with deteriorating graft function conventional treatment with high-dose corticosteroids and reinstitution of AZA failed to stop the development of obliterative bronchiolitis.

CONCLUSIONS

Our data reinforce the importance of a potent immunosuppressive regimen for the maintenance of stable graft function after lung transplantation.

Early bronchiolitis obliterans following lung transplantation: accuracy of expiratory thin-section CT for diagnosis

PURPOSE

To evaluate the accuracy of thin-section computed tomography (CT) with expiratory scans in diagnosing early bronchiolitis obliterans after lung transplantation.

MATERIALS AND METHODS

Thin-section CT scans were reviewed by two observers blinded to the diagnoses in seven consecutive lung transplant recipients with histopathologically proved bronchiolitis obliterans (group A) and 21 with normal biopsy findings (group B). All patients had normal biopsy and stable pulmonary function test (PFT) results 2-36 weeks prior to CT. Patients with normal biopsy results were placed into subgroups based on abnormal (group B1) or stable (group B2) PFT results. Air-trapping extent on expiratory scans was scored on a 24-point scale.

RESULTS

The mean air-trapping score in group A (6.6) was not significantly different from that in group B (4.5, P =. 17). The air-trapping score was significantly higher in groups A and B1 than in group B2 (6.2 and 2.6, respectively; P =.03). The frequency of an air-trapping score of 3 or more in groups A and B1 was significantly higher than that in group B2 (P =.03). By using a score of 3 or more to indicate air trapping, the sensitivity of expiratory CT was 74%, specificity was 67%, and accuracy was 71%.

CONCLUSION

Thin-section CT, including expiratory scans, is of limited accuracy in diagnosing early bronchiolitis obliterans after lung transplantation.

Elevated levels of interleukin-8 and transforming growth factor-beta in bronchoalveolar lavage fluid from patients with bronchiolitis obliterans syndrome: proinflammatory role of bronchial epithelial cells. Munich Lung Transplant Group

BACKGROUND

Obliterative bronchiolitis (OB), the most important long-term complication after lung transplantation, is thought to be a manifestation of chronic rejection within the airways, with the hallmarks inflammation and fibroproliferation.

METHODS

To characterize the inflammatory process in the context of OB we quantified tumor necrosis factor-alpha, interleukin (IL)-8, IL-10, and transforming growth factor (TGF)-beta on the protein and mRNA level in bronchoalveolar lavage fluid samples obtained from patients with bronchiolitis obliterans syndrome (BOS) and without BOS. In addition, bronchial cells sampled by bronchial brushing were analyzed for mRNA expression.

RESULTS

In respiratory epithelial lining fluid (ELF) from BOS patients the protein levels of IL-8 (52.4+/-22.2 vs. 4.4+/-0.9 pg/ml ELF, P<0.005) and TGF-beta (5.6+/-1.9 vs. 0.9+/-0.2 ng/ml ELF, P<0.005) were significantly elevated. In addition, bronchoalveolar lavage fluid cells of BOS patients showed increased expression of TGF-beta (1.13+/-0.44 vs. 0.45+/-0.16, optical density [O.D.]/O.D. glyceraldehyde-3-phosphate dehydrogenase [GAPDH], P=0.11) and IL-8 (0.25+/-0.13 vs. 0.09+/-0.03 O.D/O.D. GAPDH, P=0.53) without the differences reaching statistical significance. In contrast, IL-8 mRNA expression of bronchial cells was significantly higher in the BOS group (0.85+/-0.40 vs. 0.22+/-0.10 O.D./O.D. GAPDH, P<0.05).

CONCLUSIONS

We assume that IL-8 and TGF-beta may act as key mediators for airway inflammation and fibroproliferation in the pathogenesis of OB, with bronchial epithelial cells serving as a relevant source of IL-8.

Up-regulation of inducible nitric oxide synthase in fibroblasts parallels the onset and progression of fibrosis in an experimental model of post-transplant obliterative airway disease

The main cause of mortality following lung transplantation is chronic rejection, manifesting morphologically as obliterative bronchiolitis (OB). It has been suggested that damage to the respiratory epithelium initiates proliferation of mesenchymal cells, leading to dense collagenous scarring in small airways. Inducible nitric oxide synthase (iNOS) is strongly expressed in the damaged epithelium in human OB, along with high levels of peroxynitrite, suggesting that endogenous NO mediates the epithelial destruction. To examine further the role of iNOS in this process, heterotopic airway implants were studied in rats, an acknowledged disease model. Specimens of iso- or allografted trachea, collected 3-60 days after implantation, were processed for histology and immunocytochemistry for iNOS and, as a marker of peroxynitrite formation, nitrotyrosine. In both iso- and allografts at the earliest stage (day 3), ischaemia was associated with severe epithelial damage or loss. These changes progressed until day 7 and were accompanied by strong expression of iNOS and nitrotyrosine in epithelial cells. In isografts, epithelial recovery was seen, with abundant iNOS immunoreactivity but little nitrotyrosine. In contrast, the epithelium in allografts did not regenerate and progressive inflammation and fibroproliferation occurred until complete obliteration of the tracheal lumen at day 60. The fibroproliferation was associated with changes in morphology of fibroblasts that were accompanied by alterations in their iNOS expression. iNOS immunoreactivity was dense in the plump fibroblasts of early lesions, in some cases as early as post-operative day 5, but very weak in elongated fibroblasts in totally occluded grafts. The intensity of immunoreactivity for nitrotyrosine corresponded to that of iNOS. These results indicate a dual role for NO in the airway obliteration that follows transplantation, through destruction of epithelium and stimulation of fibroblast activity.

Does human leukocyte antigen matching influence the outcome of lung transplantation? An analysis of 3,549 lung transplantations

BACKGROUND AND OBJECTIVE

Human leukocyte antigen (HLA) compatibility has been shown to improve the outcome of renal and cardiac transplantation. However, its impact on outcome following lung transplantation is not clear, with several single-center studies reporting inconsistent results. We studied the influence of HLA matching on survival and the development of rejection and obliterative bronchiolitis after lung transplantation, using data from the United Network for Organ Sharing/International Society for Heart and Lung Transplantation registry.

METHODS

The study population included adult patients who received cadaveric lung transplants between October 1987 and June 1997 for whom HLA data were available. Two cohorts were examined, depending on the era of transplantation: (1) October 1987 to June 1997 (n = 3,549): Differences in actuarial survival as stratified by either the total number of HLA mismatches or the number of mismatches at each HLA locus were determined using a log-rank test. Multivariate logistic regression models were developed to determine independent predictors of survival at 1, 3, and 5 years following lung transplantation. (2) April 1994 to June 1997 (n = 1,796): The association of HLA mismatching with acute rejection and obliterative bronchiolitis was determined using a chi-squared analysis.

RESULTS

Only 164 patients (4.6%) received lung grafts with 2 or fewer HLA mismatches. Univariate analyses demonstrated a significant difference in post-transplant survival by mismatch level, with the total number of HLA mismatches (p = 0.0008) and mismatching at the HLA-A locus (p = 0.002) associated with worse survival. Multivariate logistic regression demonstrated that the number of mismatches at the HLA-A and HLA-DR loci predicted 1-year mortality (incremental odds ratios 1.18, p = 0.01, and 1.15, p = 0. 03, respectively). The total number of HLA mismatches predicted 3- and 5-year mortality (incremental odds ratios 1.13 at 3 years, p = 0. 0004, and 1.14 at 5 years, p = 0.0002). However, other covariates such as repeat transplantation, transplantation for congenital heart disease, advanced recipient age, and an early era of transplantation were stronger predictors of mortality. We found no significant association between HLA mismatching and the development of obliterative bronchiolitis, although there was an association between mismatching at the HLA-A locus and acute rejection episodes requiring hospital admission (p = 0.008). We also found no association between mismatching at the HLA-B locus and rejection episodes requiring either hospitalization or the alteration of anti-rejection medications (p = 0.034).

CONCLUSION

Although the number of HLA mismatches at the HLA-A and HLA-DR loci predicted 1-year mortality and the total number of mismatches predicted 3- and 5-year mortality following lung transplantation, the effect of each covariate was small in this multicenter study of 3,549 patients. Further close follow-up of registry patients is necessary to determine the effect of HLA matching on long-term survival and freedom from obliterative bronchiolitis and rejection following lung transplantation. A prospective study of HLA matching for lung transplantation should not yet be considered in view of the small number of grafts with 2 or fewer mismatches and the modest effect of HLA matching on outcome.

Blocking the CD28-B7 T-cell costimulatory pathway abrogates the development of obliterative bronchiolitis in a murine heterotopic airway model

BACKGROUND

CTLA4IgG that binds to B7 effectively inhibits the signaling of CD28/B7 pathway and induces antigen-specific T-cell unresponsiveness in vitro and in vivo. We examined whether the development of obliterative bronchiolitis in a murine heterotopic airway transplantation model is T cell dependent and whether CTLA4IgG abrogates the development of obliterative bronchiolitis.

METHODS

Tracheae with main bronchi from C3H/He (H2k), BALB/C (H2d), or C57BL/6 (H2b) mice were transplanted heterotopically into subcutaneous pockets on the backs of BALB/C or BALB/C nu/nu mice on day 0. Recipient mice were untreated or intraperitoneally treated with either CTLA4IgG or human IgG with different time and dose schedules.

RESULTS

The development of obliterative bronchiolitis, which leads to luminal obliteration by fibrous tissue in a murine heterotopic airway transplantation model, was T cell dependent and the development of obliterative bronchiolitis was significantly abrogated by the CTLA4IgG treatment. However, the normal ciliated columnar respiratory epithelial cells in allografts were lost and replaced by flattened attenuated epithelial cells even after the CTLA4IgG treatment. We further demonstrated that CTLA4IgG treatment did not result in the induction of donor-specific unresponsiveness.

CONCLUSIONS

We demonstrated that the development of obliterative bronchiolitis in a murine heterotopic airway model involves both CD28/B7-dependent and -independent processes. The luminal obliteration by fibrous tissue is clearly CD28/B7 dependent and can be inhibited by CTLA4IgG. The luminal obliteration of allografted trachea by fibrous tissues and the loss of ciliated columnar respiratory epithelial cells represent distinct disease processes.