Comparison of induced sputum and bronchoalveolar lavage in lung transplant recipients

Ventilatory capacity in CLAD is driven by dysfunctional airway structure

BACKGROUND

Chronic lung allograft dysfunction (CLAD) encompasses three main phenotypes: bronchiolitis obliterans syndrome (BOS), restrictive allograft syndrome (RAS) and a Mixed phenotype combining both pathologies. How the airway structure in its entirety is affected in these phenotypes is still poorly understood.

METHODS

A detailed analysis of airway morphometry was applied to gain insights on the effects of airway remodelling on the distribution of alveolar ventilation in end-stage CLAD. Ex vivo whole lung μCT and tissue-core μCT scanning of six control, six BOS, three RAS and three Mixed explant lung grafts (9 male, 9 female, 2014-2021, Leuven, Belgium) were used for digital airway reconstruction and calculation of airway dimensions in relation to luminal obstructions.

FINDINGS

BOS and Mixed explants demonstrated airway obstructions of proximal bronchioles (starting at generation five), while RAS explants particularly had airway obstructions in the most distal bronchioles (generation >12). In BOS and Mixed explants 76% and 84% of bronchioles were obstructed, respectively, while this was 22% in RAS. Bronchiolar obstructions were mainly caused by lymphocytic inflammation of the airway wall or fibrotic remodelling, i.e. constrictive bronchiolitis. Proximal bronchiolectasis and imbalance in distal lung ventilation were present in all CLAD phenotypes and explain poor lung function and deterioration of specific lung function parameters.

INTERPRETATION

Alterations in the structure of conducting bronchioles revealed CLAD to affect alveolar ventilatory distribution in a regional fashion. The significance of various obstructions, particularly those associated with mucus, is highlighted.

FUNDING

This research was funded with the National research fund Flanders (G060322N), received by R.V.

Relation of sputum neutrophilia to the development of chronic lung allograft dysfunction after lung transplantation

Chronic lung allograft dysfunction (CLAD) is a serious complication after lung transplantation (LuTx) and is associated with elevated proportions of neutrophils in bronchoalveolar lavage (BAL). Induced sputum is a less-invasive sampling method than BAL and assesses markers of inflammation on the surfaces of large central airways. We wanted to examine whether % neutrophil levels in induced sputum were elevated prior to CLAD diagnosis among LuTx recipients, and whether sputum markers of inflammation can be used as a tool for predicting the development of CLAD. Induced sputum samples were collected at 1, 3, 6, 12, and 24 months post-LuTx in 36 patients with a history of COPD or pulmonary fibrosis, and of these, 16 developed CLAD either during or after the sputum surveillance period. At 2 years, median (IQR) % neutrophils in induced sputum were significantly higher among patients with CLAD compared with those without CLAD [73 (52-80) % vs 59 (41-76) %, p = .01]. Interestingly, we found a significant increase in the rate of change in % neutrophils beginning at 90 days preceding the diagnosis of CLAD. This suggests using sputum neutrophil percentage as a surveillance modality for monitoring lung allograft function after LuTx.

Application of nitric oxide measurements in clinical conditions beyond asthma

Fractional exhaled nitric oxide (FeNO) is a convenient, non-invasive method for the assessment of active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid diagnosis and monitoring in several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory, infectious, and/or immunological conditions. In this short review, we provide an overview of several clinical studies and discuss the status of potential applications of NO measurements in clinical conditions beyond asthma.

Bronchoalveolar lavage as a tool to predict, diagnose and understand bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS), a condition of irreversible small airway fibrosis, is the principal factor limiting long-term survival after lung transplantation. Bronchoscopy and bronchoalveolar lavage (BAL), techniques central to lung transplant clinical practice, provide a unique opportunity to interrogate the lung allograft during BOS development and identify potential disease mechanisms or biomarkers. Over the past 20 years, numerous studies have evaluated the BAL cellular composition, cytokine profiles and protein constituents in lung transplant recipients with BOS. To date, however, no summative evaluation of this literature has been reported. We developed and applied objective criteria to qualitatively rank the strength of associations between BAL parameters and BOS in order to provide a comprehensive and systematic assessment of the literature. Our analysis indicates that several BAL parameters, including neutrophil count, interleukin-8, alpha defensins and MMP-9, demonstrate highly replicable associations with BOS. Additionally, we suggest that considerable opportunity exists to increase the knowledge gained from BAL analyses in BOS through increased sample sizes, covariant adjustment and standardization of the BAL technique. Further efforts to leverage analysis of BAL constituents in BOS may offer great potential to provide additional in-depth and mechanistic insights into the pathogenesis of this complex disease.

High extracellular induced sputum haem oxygenase-1 in sarcoidosis and chronic beryllium disease

BACKGROUND

Sarcoidosis and chronic beryllium disease (CBD) are inflammatory conditions in which oxidative stress state may be crucial for disease outcome. This study compares haem oxygenase-1 (HO-1) extracellular activity for the first time in patients with sarcoidosis or CBD and in healthy controls.

MATERIALS AND METHODS

Induced sputum was recovered using a standard protocol. Pulmonary function tests (PFT) were performed by conventional methods. T lymphocyte subsets (CD4 and CD8) were measured by flow activated cell shorter (FACS). The HO-1 and nitrite levels were measured by a bilirubin-biliverdin reductase-dependent reaction and Greiss reaction respectively. Ferritin and iron levels were measured by enzymatic reaction and chemiluminometric immunoassay respectively.

RESULTS

The mean percentage of lymphocytes was significantly higher in the 36 sarcoid patients compared with that in the 17 controls (P=0.001). The mean CD4/CD8 ratio was significantly higher in the sarcoid and the 10 CBD patients compared to that in controls (P=0.000 and 0.002 respectively), as was the mean HO-1 activity (P=0.045 and 0.041 respectively). The HO-1 activity did not differ with the sarcoidosis stage. The HO-1 level and PFT parameters were negatively correlated. The differences in mean nitrite, ferritin and iron levels were non-significant between the three groups. The HO-1 and ferritin levels were correlated (P=0.008).

CONCLUSIONS

We succeeded in non-invasively measuring the activity of HO-1 from cells of airways in spite of its being an intracellular enzyme. The HO-1 levels in sarcoidosis and CBD were abnormally elevated.

T regulatory cells in stable posttransplant bronchiolitis obliterans syndrome

BACKGROUND

Obliterative bronchiolitis (OB), mainly mediated by T cells, remains the major cause of morbidity and death in long-term lung transplant. Acute rejection (AR), also a T-cell mediated process, is strongly linked to OB. For unknown reasons, several patients with OB halt their pulmonary function decline and stabilize their obstructive defect for a long period. Our aim was to assess the T-cell activation in blood, induced sputum, and broncho-alveolar lavage during AR, stable OB (sOB), and evolving OB (eOB).

METHODS

T-cell phenotype and cytokine production were assessed by flow cytometry in these three compartments. Interleukin-4, interferon-gamma and transforming growth factor (TGF)-beta levels were measured by enzyme-linked immunosorbent assay in blood cell culture supernatants. Results were compared between healthy lung transplant recipients and AR (n=7), sOB (n=7), and eOB (n=13).

RESULTS

Stable and evolutive OB were characterized by a Treg, Th1, and Th2 activation, but compared to eOB, Treg and Th2 cells predominated in sOB. A clear Th1 activation was observed in AR. TGF-beta was increased in AR and evolving OB.

CONCLUSION

These preliminary results indicate a contrasted T-cell activation profile depending on the clinical conditions. We speculate that Treg cells could counterbalance the Th0 activation seen in evolving OB and participate in stabilization of airway obstruction.