Lung Microenvironments and Disease Progression in Fibrotic Hypersensitivity Pneumonitis.

Rationale: Fibrotic hypersensitivity pneumonitis (fHP) is an interstitial lung disease caused by sensitization to an inhaled allergen. Objectives: To identify the molecular determinants associated with progression of fibrosis. Methods: Nine fHP explant lungs and six unused donor lungs (as controls) were systematically sampled (4 samples/lung). According to microcomputed tomography measures, fHP cores were clustered into mild, moderate, and severe fibrosis groups. Gene expression profiles were assessed using weighted gene co-expression network analysis, xCell, gene ontology, and structure enrichment analysis. Gene expression of the prevailing molecular traits was also compared with idiopathic pulmonary fibrosis (IPF). The explant lung findings were evaluated in separate clinical fHP cohorts using tissue, BAL samples, and computed tomography scans. Measurements and Main Results: We found six molecular traits that associated with differential lung involvement. In fHP, extracellular matrix and antigen presentation/sensitization transcriptomic signatures characterized lung zones with only mild structural and histological changes, whereas signatures involved in honeycombing and B cells dominated the transcriptome in the most severely affected lung zones. With increasing disease severity, endothelial function was progressively lost, and progressive disruption in normal cellular homeostatic processes emerged. All six were also found in IPF, with largely similar associations with disease microenvironments. The molecular traits correlated with in vivo disease behavior in a separate clinical fHP cohort. Conclusions: We identified six molecular traits that characterize the morphological progression of fHP and associate with in vivo clinical behavior. Comparing IPF with fHP, the transcriptome landscape was determined considerably by local disease extent rather than by diagnosis alone.

Mucus Release and Airway Constriction by TMEM16A May Worsen Pathology in Inflammatory Lung Disease.

Activation of the Ca2+ activated Cl- channel TMEM16A is proposed as a treatment in inflammatory airway disease. It is assumed that activation of TMEM16A will induce electrolyte secretion, and thus reduce airway mucus plugging and improve mucociliary clearance. A benefit of activation of TMEM16A was shown in vitro and in studies in sheep, but others reported an increase in mucus production and airway contraction by activation of TMEM16A. We analyzed expression of TMEM16A in healthy and inflamed human and mouse airways and examined the consequences of activation or inhibition of TMEM16A in asthmatic mice. TMEM16A was found to be upregulated in the lungs of patients with asthma or cystic fibrosis, as well as in the airways of asthmatic mice. Activation or potentiation of TMEM16A by the compounds Eact or brevenal, respectively, induced acute mucus release from airway goblet cells and induced bronchoconstriction in mice in vivo. In contrast, niclosamide, an inhibitor of TMEM16A, blocked mucus production and mucus secretion in vivo and in vitro. Treatment of airway epithelial cells with niclosamide strongly inhibited expression of the essential transcription factor of Th2-dependent inflammation and goblet cell differentiation, SAM pointed domain-containing ETS-like factor (SPDEF). Activation of TMEM16A in people with inflammatory airway diseases is likely to induce mucus secretion along with airway constriction. In contrast, inhibitors of TMEM16A may suppress pulmonary Th2 inflammation, goblet cell metaplasia, mucus production, and bronchoconstriction, partially by inhibiting expression of SPDEF.

Normal Routine Spirometry Can Mask COPD/Emphysema in Symptomatic Smokers.

BACKGROUND: Recent studies have emphasized the difficulty of early detection of chronic obstructive pulmonary disease (COPD) in symptomatic smokers with normal routine spirometry. This includes post-bronchodilator normal forced expiratory volume in 1 second (FEV1)(L)≥80% predicted, forced vital capacity (FVC)(L)≥80% predicted, and FEV1/FVC ≥70% or greater than age corrected lower limit of normal (LLN). However, in COPD the pathologic site of small airway obstruction and emphysema begins in the small peripheral airways ≤2 mm id which normally contribute <20% of total airway resistance. METHODS: Expiratory airflow at high and low lung volumes post-bronchodilator were measured and correlated with lung computed tomography (CT) and lung pathology (6 patients) in 16 symptomatic, treated smokers, and all with normal routine spirometry. RESULTS: Despite normal routine spirometry, all16 patients had isolated, abnormal forced expiratory flow at 75% of FVC (FEF75) using data from Knudson et al, Hankinson et al NHAMES III, and Quanjer et al and the Global Lung Function Initiative. This reflects isolated detection of small airways obstruction and/or emphysema. Measuring airflow at FEF50 detected only 8 of 16 patients, maximal expiratory flow at 25%-75% of FVC (MEF25-75) only 4 of 16, residual volume (RV) 4 of 16, and RV to total lung capacity ratio only 2 of 16. There was excellent correlation between limited lung pathology and lung CT for absence of emphysema. CONCLUSION: This study confirms our earlier observations that detection of small airways obstruction and/or emphysema, in symptomatic smokers with normal routine spirometry, requires analysis of expiratory airflow at low lung volumes, including FEF75. Dependence upon normal routine spirometry may result in clinical and physiologic delay in the diagnosis and treatment in symptomatic smokers with emphysema and small airways obstruction.

Beyond Bronchiolitis Obliterans: In-Depth Histopathologic Characterization of Bronchiolitis Obliterans Syndrome after Lung Transplantation.

Bronchiolitis obliterans syndrome (BOS) is considered an airway-centered disease, with bronchiolitis obliterans (BO) as pathologic hallmark. However, the histologic spectrum of pure clinical BOS remains poorly characterized. We provide the first in-depth histopathologic description of well-characterized BOS patients and patients without chronic lung allograft dysfunction (CLAD), defined according to the recent consensus guidelines. Explant lung tissue from 52 clinically-defined BOS and 26 non-CLAD patients (collected 1993-2018) was analyzed for histologic parameters, including but not limited to airway lesions, vasculopathy and fibrosis. In BOS, BO lesions were evident in 38 (73%) patients and varied from concentric sub-epithelial fibrotic BO to inflammatory BO, while 10/14 patients without BO displayed 'vanishing airways', defined by a discordance between arteries and airways. Chronic vascular abnormalities were detected in 22 (42%) patients. Ashcroft fibrosis scores revealed a median of 43% (IQR: 23-69) of normal lung parenchyma per patient; 26% (IQR: 18-37) of minimal alveolar fibrous thickening; and 11% (IQR: 4-18) of moderate alveolar thickening without architectural damage. Patchy areas of definite fibrotic damage to the lung structure (i.e., Ashcroft score ≥5) were present in 28 (54%) patients. Fibrosis was classified as bronchocentric (n = 21/28, 75%), paraseptal (n = 17/28, 61%) and subpleural (n = 15/28, 54%). In non-CLAD patients, BO lesions were absent, chronic vascular abnormalities present in 1 (4%) patient and mean Ashcroft scores were significantly lower compared to BOS (p = 0.0038) with 78% (IQR: 64-88) normally preserved lung parenchyma. BOS explant lungs revealed evidence of various histopathologic findings, including vasculopathy and fibrotic changes, which may contribute to the pathophysiology of BOS.

Histopathologic and radiologic assessment of nontransplanted donor lungs.

Donor organ shortage results in significant waiting list mortality. Donor lung assessment is currently based on donors' history, gas exchange, chest X-ray, bronchoscopy findings, and ultimately in situ inspection but remains subjective. We correlated histopathology and radiology in nontransplanted donor lungs with the clinical indications to decline the offered organ. Sixty-two donor lungs, not used for transplantation (2010-2019), were procured, air-inflated, frozen, scanned with computed tomography, systematically sampled, and histologically and radiologically assessed. Thirty-nine (63%) lungs were declined for allograft-related reasons. In 13/39 (33%) lungs, histology could not confirm the reason for decline, in an additional 8/39 (21%) lungs, histologic abnormalities were only considered mild. In 16/39 (41%) lungs, radiology could not confirm the reason for decline. Twenty-three (37%) donor lungs were not transplanted due to extrapulmonary causes, of which three (13%) lungs displayed severe histologic abnormalities (pneumonia, n = 2; emphysema, n = 1), in addition to mild emphysema in 9 (39%) lungs and minor bronchopneumonia in 1 (4%). Radiology revealed ground-glass opacities in 8/23 (35%) and emphysema in 4/23 (17%) lungs. Histopathologic and radiologic assessment of nontransplanted donor lungs revealed substantial discrepancy with the clinical reason for decline. Optimization of donor lung assessment is necessary to improve current organ acceptance rates.

Total lymphoid irradiation in progressive bronchiolitis obliterans syndrome after lung transplantation: a single-center experience and review of literature.

Limited results about treatment with total lymphoid irradiation (TLI) in lung transplant (LTx) recipients suffering from progressive bronchiolitis obliterans syndrome (BOS) have been reported. We performed a retrospective analysis of all LTx recipients undergoing TLI for progressive BOS in our center, focusing on long-term outcomes regarding overall survival and lung allograft function. Treatment with TLI (2004-2017, n = 20, 1 BOS stage 1, 6 BOS stage 2, and 13 BOS stage 3) resulted in significant attenuation of the FEV1 -decline in the majority of patients, mainly in those with a rapid decline (P = 0.0005). This allowed bridging to redo-transplantation in five patients. However, three patients progressed from BOS to RAS following prior TLI. Overall patient survival was 44% at 2 years post-TLI and 38% after 17 years. Generally, TLI was well tolerated, with limited side effects and no serious adverse events. TLI may attenuate the decline in FEV1 of LTx recipients with rapid progressive BOS and could thus help to bridge selected patients to redo-transplantation.

Mortality after lung transplantation: a single-centre cohort analysis.

Detailed data on postoperative death in lung transplant (LTx) recipients are lacking. Therefore, we investigated all deaths after LTx in a large, single-centre, 25-year follow-up cohort. Prevalence, time, place and cause of death (COD) were retrospectively analysed for all patients undergoing primary LTx between July 1991 and December 2015 in our centre. Over subsequent years, postoperative survival significantly improved, with proportionally more patients surviving to 1-year post-LTx (P < 0.0001). A total of 347 (38.9%) LTx recipients died, of which 53.6% expired within 3 years post-LTx [median time to death 910 (236-2447) days]. Autopsy was performed in 34.8% of deaths. COD included CLAD in 27.1% (BOS 63.8% vs. RAS 36.2%); infection (26.5%); malignancy (15.6%); postoperative complication (11.2%); cardiovascular disease (4.6%) or other causes (6.9%). In 8.1%, no clear COD could be determined. COD significantly differed between the various LTx indications (P = 0.047). With longer follow-up, infection becomes a less prevalent COD, but CLAD and malignancies a more important COD. The majority of patients died on the intensive care unit (40.6%) or hospital ward (29.1%), but place of death varied depending on the underlying COD. The current study provides insights into the postoperative deaths of LTx recipients.

Granulomatous lung disease in two workers making light bulbs.

BACKGROUND: Associations between sarcoidosis or sarcoid-like granulomatous lung disease and exposure to silica and other inorganic agents have been suggested in several studies. CASES: We describe granulomatous lung disease in two workers of a small production unit making metal-halide lamps. Initially, both were diagnosed with sarcoidosis. However, in both men, birefringent particles were observed in the lung or mediastinal lymph node biopsies. Clipping of glass tubes led to moderate exposure to dust, consisting mainly of amorphous fused silica, with some cristobalite. After removal from exposure, both subjects improved clinically, radiologically, and functionally. CONCLUSION: The present cases support the hypothesis that silica might be a trigger for sarcoid-like granulomatous lung disease. Sarcoidosis should be considered a diagnosis of exclusion and clinicians should carefully collect occupational and environmental exposure histories to identify workplace triggers.

Azithromycin and early allograft function after lung transplantation: A randomized, controlled trial.

BACKGROUND: Chronic lung allograft dysfunction (CLAD) is the single most important factor limiting long-term survival after lung transplantation (LTx). Azithromycin has been shown to improve CLAD-free and long-term survival, yet the possible impact on early lung allograft function is unclear. METHODS: A prospective, randomized, double-blind, placebo-controlled trial of pre-transplant and prompt post-transplant azithromycin treatment was performed at the University Hospitals Leuven. In each arm, 34 patients, transplanted between October 2013 and October 2015, were included for analysis. Study drug was added to standard of care and was administered once before LTx (1,000 mg of azithromycin or placebo) and every other day from Day 1 until Day 31 after LTx (250 mg of azithromycin or placebo). Primary outcome was an anticipated 15% improvement of forced expiratory volume in 1 second (FEV1, percent predicted) during the first 3 months post-LTx. Secondary end-points included length of intubation, days on ventilator, duration of intensive care unit and hospital stay, prevalence and severity of primary graft dysfunction, acute rejection, infection, and CLAD-free and overall survival. RESULTS: FEV1 was not significantly different between the 2 groups (p = 0.41). Patients treated with azithromycin demonstrated less airway inflammation, with lower bronchoalveolar lavage (BAL) neutrophilia and BAL interleukin-8 protein levels at Day 30 (p = 0.09 and p = 0.04, respectively) and Day 90 (p = 0.002 and p = 0.08, respectively) after LTx. Other secondary outcomes were not significantly different between placebo and azithromycin groups. CONCLUSIONS: Pre-transplant and prompt post-transplant azithromycin treatment was not able to improve early lung allograft function. However, the known anti-inflammatory properties of azithromycin were confirmed (NCT01915082).

Montelukast in chronic lung allograft dysfunction after lung transplantation.

BACKGROUND: Chronic lung allograft dysfunction (CLAD) is a major cause of post‒lung transplant mortality, with limited medical treatment options. In this study we assessed the association of montelukast treatment with pulmonary function and outcome in lung transplant recipients with progressive CLAD. METHODS: We performed a retrospective study of all lung transplant recipients transplanted between July 1991 and December 2016 at our center and who were treated for at least 3 months with montelukast for progressive CLAD, despite at least 3 months of prior azithromycin therapy. Main outcome parameters included evolution of pulmonary function and progression-free and overall survival. RESULTS: A total of 153 patients with CLAD (115 with bronchiolitis obliterans syndrome and 38 with restrictive allograft syndrome) were included, of whom 46% had a forced expiratory volume in 1 second (FEV1) measure of between 66% and 80%, 31% an FEV1 between 51% and 65%, and 23% an FEV1 ≤50% of best post-operative FEV1 at start of montelukast. Montelukast was associated with attenuation in rate of FEV1 decline after 3 and 6 months, respectively (both p < 0.0001). Patients in whom FEV1 improved or stabilized after 3 months of montelukast (81%) had significantly better progression-free (p < 0.0001) and overall (p = 0.0002) survival after CLAD onset, as compared to those with further decline of FEV1 (hazard ratio [HR] 2.816, 95% confidence interval [CI] 1.450 to 5.467, p = 0.0022 for overall survival after CLAD onset in risk-adjusted multivariate analysis). CONCLUSIONS: Montelukast was associated with a significant attenuation in rate of FEV1 decline in a substantial proportion of patients with established CLAD, which correlated with better outcome. Further study is required regarding use of montelkast.

Validation of a post-transplant chronic lung allograft dysfunction classification system.

BACKGROUND: Long-term survival after lung transplantation (LTx) is hampered by chronic lung allograft dysfunction (CLAD). Our study evaluated the prevalence and prognostic importance of obstructive and restrictive CLAD phenotypes, with or without an identifiable underlying cause, to validate the recently proposed classification system for CLAD. METHODS: Data for patients who underwent LTx between 2004 and 2015 with a minimal survival of 180 days post-LTx were retrospectively collected. Double LTx patients with CLAD (defined as a persistent forced expiratory volume in 1 second decline of ≥ 20% compared with baseline) were subsequently classified according to obstructive (forced expiratory volume in 1 second /forced vital capacity [FVC] < 70%, total lung capacity > 90%, and FVC > 80%) or restrictive (total lung capacity ≤ 90% or FVC ≤ 80%) pulmonary function and to the presence of an unknown (bronchiolitis obliterans syndrome [BOS]/restrictive allograft syndrome [RAS]) or known (non-BOS/non-RAS) underlying cause. RESULTS: After a median of 3.2 years, CLAD developed in 39% of double LTx patients (n = 219), of which 20% (n = 43) had an identifiable cause. Survival was worse in patients with restrictive CLAD (26%) compared with obstructive CLAD (64%; p < 0.0001). Non-BOS patients suffered from inferior survival compared with BOS patients (p = 0.0016), whereas there was no significant difference in survival between RAS and non-RAS (p = 0.17). Patients who evolved from an obstructive (BOS) to a restrictive (RAS) phenotype (10%) experienced better survival than RAS patients and a worse outcome compared with BOS patients (p < 0.0001). CONCLUSIONS: Given the differences in outcome, accurate diagnosis of CLAD phenotypes is important, because this helps to inform patients about their prognosis, to reveal underlying pathogenesis, to identify homogenous patient populations for clinical trials, and to guide future therapeutic approaches.

Effects of Corticosteroid Treatment and Antigen Avoidance in a Large Hypersensitivity Pneumonitis Cohort: A Single-Centre Cohort Study.

BACKGROUND: Although the third most frequent interstitial lung disease, hypersensitivity pneumonitis (HP) remains an enigmatic disease without clear diagnostic and therapeutic guidelines. We assessed the effect of the commonly used therapeutic interventions (i.e. exposure avoidance and corticosteroid treatment) in an HP cohort. METHODS: We collected clinical data of all HP patients followed at our centre between January 1, 2005, and December 31, 2016. HP patients were stratified according to the presence of fibrosis on chest CT. Survival was analysed using the multivariate Cox proportional hazards model. Forced vital capacity (percent predicted, FVC%) and diffusing capacity of the lung for carbon monoxide (percent predicted, DLCO%) evolution were analysed using linear mixed-effect models. RESULTS: Two hundred and two HP patients were identified: 93 non-fibrotic HP (nfHP) and 109 fibrotic HP (fHP), experiencing a monthly FVC% decline before treatment of 0.93% and 0.56%, respectively. While nfHP had an excellent survival, fHP patients experienced a median survival of 9.2 years. Corticosteroid treatment and exposure avoidance did not result in survival differences. Although nfHP patients showed FVC% and DLCO% increase after corticosteroid initiation, no therapeutic effect was seen in fHP patients. FVC% and DLCO% increased in nfHP patients after exposure avoidance, while a positive numerical trend was seen for FVC% after exposure avoidance in fHP patients (p = 0.15). CONCLUSIONS: nfHP patients experienced an excellent survival with good therapeutic effect on pulmonary function tests with both corticosteroid initiation as well as antigen avoidance. In contrast, fHP patients experienced a dismal prognosis (median survival of 9.2 years) without any therapeutic effect of corticosteroid treatment. Whether antigen avoidance is useful in fHP patients is still unclear.

Pirfenidone in restrictive allograft syndrome after lung transplantation: A case series.

Pirfenidone may attenuate the decline of pulmonary function in restrictive allograft syndrome (RAS) after lung transplantation. We retrospectively assessed all lung transplant recipients with RAS who were treated with pirfenidone for at least 3 months (n = 11) in our lung transplant center and report on their long-term outcomes following initiation of pirfenidone. Main outcome parameters included evolution of pulmonary function and overall survival. Pirfenidone appears to attenuate the decline in forced vital capacity and forced expiratory volume in 1 second. Notably, 3 patients were bridged to redo-transplantation with pirfenidone for 11 (5-12) months and are currently alive, while 3 other patients demonstrate long-term stabilization of pulmonary function after 26.6 (range 18.4-46.6) months of treatment. Median overall 3-year survival after RAS diagnosis was 54.5%. Subjective intolerance, mainly anorexia and nausea, necessitating pirfenidone dose de-escalation in 55% of patients, as well as calcineurin dose increase requirements with about 20% are important complications during pirfenidone treatment after lung transplantation. Our findings provide further evidence that pirfenidone appears to be safe and may attenuate the rate of decline in lung function in patients with RAS, but the actual clinical benefit cannot be assessed in the context of this study design and requires further investigation in a larger randomized trial.

Clinical behaviour of patients exposed to organic dust and diagnosed with idiopathic pulmonary fibrosis.

BACKGROUND AND OBJECTIVE: Although idiopathic pulmonary fibrosis (IPF) patients experience a worse survival compared with chronic hypersensitivity pneumonitis (CHP), organic dust exposure is a known risk factor for both IPF and CHP. METHODS: We divided patients diagnosed with IPF, based on their exposure to moulds/birds (absent: group A; present: group B). We retrospectively compared pulmonary function and survival between groups A and B, and a separate CHP cohort (group C). RESULTS: A total of 293 patients were included (group A: n = 171, group B: n = 73, group C: n = 49). Demographics and baseline pulmonary function did not differ between groups A and B, but significant differences were seen between groups B and C. Median survival of group B was 84 months, which was longer than group A (43 months, P = 0.002), but lower than group C (157 months, P = 0.04), in both univariate and multivariate analyses. Antifibrotic treatment resulted in a better outcome in group A (hazard ratio (HR): 0.44) and group B (HR: 0.12) without interaction between exposure and antifibrotic use (P = 0.20). Forced vital capacity (FVC) decline was not associated with mould/bird exposure in this cohort. CONCLUSION: Group B patients experienced a better outcome compared with (non-exposed) IPF patients, although worse compared with CHP patients. Antifibrotic treatment in group B resulted in a similar beneficial effect compared with group A. Further research is needed to ascertain the diagnostic designation in this exposed usual interstitial pneumonia (UIP) patient group without other CHP features.

Diagnostic Ability of a Dynamic Multidisciplinary Discussion in Interstitial Lung Diseases: A Retrospective Observational Study of 938 Cases.

BACKGROUND: The advice of a dynamic multidisciplinary discussion (MDD) is believed to be important in the diagnosis of interstitial lung diseases (ILDs). However, to what extent MDD diagnoses differ from the preliminary diagnoses before formal workup and MDD (preMDD diagnoses) is still insufficiently studied. METHODS: We compared preMDD and MDD diagnoses in patients discussed at the Leuven University Hospitals MDDs between January 2005 and December 2015. RESULTS: Of 938 consecutive patients discussed in an MDD, 755 (80.5%) received a specific diagnosis. From the 183 patients with unclassifiable ILD, 150 patients (16.0%) received suggestions concerning further investigations to establish a definite diagnosis. In 191 patients (41.9% of patients with a preMDD diagnosis), the MDD changed the diagnosis. In 384 patients (79.5% of patients without preMDD diagnosis), MDD provided a diagnosis when the referring physician did not. MDD diagnosis showed a trend toward better prognostic discrimination between idiopathic pulmonary fibrosis and other ILDs compared with preMDD diagnosis (Harrell C-index, 0.666 vs 0.631; P = .08), which was particularly clear in patients with discordant MDD and preMDD diagnoses (hazard ratio, 2.68 vs 0.84; P = .012 vs .768). CONCLUSIONS: The MDD provided a definite diagnosis in 80.5% of presented cases, suggesting further investigations in almost all others. Given the high number of patients without preMDD diagnosis, the rate of change in preMDD diagnoses (41.9% of patients with a preMDD diagnosis) probably is an underestimation. The better prognostic discrimination among ILDs by using MDD indicates the added value of MDD in ILD.

An unusual presentation of a more common disease entity.

Beware unusual presentations of more common disease entities, as in this interactive case report http://ow.ly/qj7f30eVFsp.

Multiple Solid Organ Transplantation in Telomeropathy: Case Series and Literature Review.

BACKGROUND: Solid organ transplantation is a valid treatment option for selected patients with organ failure due to an underlying telomeropathy; however, the feasibility of multiple-organ transplantation if several organs are compromised is unclear. METHODS: We describe 2 patients with telomeropathy due to heterozygous telomerase RNA component or telomerase reverse transcriptase mutation, who successfully underwent serial or combined liver and lung transplantation for concurrent liver fibrosis/cirrhosis and pulmonary fibrosis. RESULTS: Despite a challenging posttransplant course, long-term outcomes were favorable, with both patients doing fine now, respectively, 12/20 and 24 months after multiple-organ transplantation. CONCLUSIONS: To our knowledge, this is the first report of multiple solid organ transplantation in documented telomeropathy. These cases highlight current difficulties of timely diagnosis, therapeutic approach, and postoperative complications in telomeropathy patients in whom several organs are affected.

Epithelial grafting of a decellularized whole-tracheal segment: an in vivo experimental model.

OBJECTIVES: Prerequisites for successful trachea transplantation include the use of a biocompatible construct, submucosal vascularization and an epithelial covering. Implantation of non-epithelialized tracheal scaffolds may lead to stenosis. However, epithelial grafting or seeding can only be attempted onto a well-vascularized submucosal bed. Our aim was to investigate a method to prevent stenosis during prelamination of non-epithelialized, gently decellularized rabbit tracheae and to evaluate whether grafting of revascularized constructs with buccal mucosa is feasible. METHODS: Allotracheae underwent two 48-h cycles of detergent-enzymatic decellularization using sodium deoxycholate and DNAse. In the first series, 12 circular scaffolds were implanted bilaterally in lateral thoracic artery flaps (n = 6 rabbits). Right-sided transplants were covered internally with Integra™. In the second series, 10 decellularized tracheae covered with Integra were prelaminated in flaps (n = 10 rabbits). Twenty-one days after implantation, revascularized tracheae were grafted with buccal mucosa. A macroscopic, histological analysis and immunohistochemistry were performed on explants. RESULTS: In the first series, tracheae without Integra covering developed significantly greater intraluminal (P = 0.032) and subepithelial narrowing (P = 0.0345) compared with tracheae with Integra covering. All tracheae exhibited insufficient submucosal revascularization. In the second series, submucosal revascularization was incomplete in the first 2 constructs, which were implanted circularly. These tracheae only showed marginal buccal graft ingrowth. To accelerate revascularization, the subsequent 8 transplants were opened longitudinally before implantation. Compared to circularly implanted tracheae, submucosal revascularization of these transplants was superior (P = 0.0008). Graft adherence was complete in 6 opened constructs. Mild lymphocytic infiltration within the buccal graft was detected in 5 specimens. CONCLUSIONS: We observed satisfactory host integration of opened tracheae that were temporarily covered with Integra during revascularization and subsequently grafted with buccal mucosa. Integra successfully prevented stenosis during revascularization. This model may provide an example of an immunosuppressive-free approach in the treatment of long-segment tracheal lesions. With the aid of further refinements such as a respiratory epithelial lining, an orthotopically transplantable construct could be created.