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.

Mucosal immune alterations at the early onset of tissue destruction in chronic obstructive pulmonary disease

Rationale

COPD is characterized by chronic airway inflammation, small airways changes, with disappearance and obstruction, and also distal/alveolar destruction (emphysema). The chronology by which these three features evolve with altered mucosal immunity remains elusive. This study assessed the mucosal immune defense in human control and end-stage COPD lungs, by detailed microCT and RNA transcriptomic analysis of diversely affected zones.

Methods

In 11 control (non-used donors) and 11 COPD (end-stage) explant frozen lungs, 4 cylinders/cores were processed per lung for microCT and tissue transcriptomics. MicroCT was used to quantify tissue percentage and alveolar surface density to classify the COPD cores in mild, moderate and severe alveolar destruction groups, as well as to quantify terminal bronchioles in each group. Transcriptomics of each core assessed fold changes in innate and adaptive cells and pathway enrichment score between control and COPD cores. Immunostainings of immune cells were performed for validation.

Results

In mildly affected zones, decreased defensins and increased mucus production were observed, along CD8+ T cell accumulation and activation of the IgA pathway. In more severely affected zones, CD68+ myeloid antigen-presenting cells, CD4+ T cells and B cells, as well as MHCII and IgA pathway genes were upregulated. In contrast, terminal bronchioles were decreased in all COPD cores.

Conclusion

Spatial investigation of end-stage COPD lungs show that mucosal defense dysregulation with decreased defensins and increased mucus and IgA responses, start concomitantly with CD8+ T-cell accumulation in mild emphysema zones, where terminal bronchioles are already decreased. In contrast, adaptive Th and B cell activation is observed in areas with more advanced tissue destruction. This study suggests that in COPD innate immune alterations occur early in the tissue destruction process, which affects both the alveoli and the terminal bronchioles, before the onset of an adaptive immune response.

COVID-19 progression in hospitalized patients using follow-up in vivo CT and ex vivo microCT

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease-19 (COVID-19) which can lead to acute respiratory distress syndrome (ARDS) and evolve to pulmonary fibrosis. Computed tomography (CT) is used to study disease progression and describe radiological patterns in COVID-19 patients. This study aimed to assess disease progression regarding lung volume and density over time on follow-up in vivo chest CT and give a unique look at parenchymal and morphological airway changes in "end-stage" COVID-19 lungs using ex vivo microCT.

METHODS

Volumes and densities of the lung/lobes of three COVID-19 patients were assessed using follow-up in vivo CT and ex vivo whole lung microCT scans. Airways were quantified by airway segmentations on whole lung microCT and small-partition microCT. As controls, three discarded healthy donor lungs were used. Histology was performed in differently affected regions in the COVID-19 lungs.

RESULTS

In vivo, COVID-19 lung volumes decreased while density increased over time, mainly in lower lobes as previously shown. Ex vivo COVID-19 lung volumes decreased by 60% and all lobes were smaller compared to controls. Airways were more visible on ex vivo microCT in COVID-19, probably due to fibrosis and increased airway diameter. In addition, small-partition microCT showed more deformation of (small) airway morphology and fibrotic organization in severely affected regions with heterogeneous distributions within the same lung which was confirmed by histology.

CONCLUSIONS

COVID-19-ARDS and subsequent pulmonary fibrosis alters lung architecture and airway morphology which is described using in vivo CT, ex vivo microCT, and histology.

Aspergillus-Specific IgG Antibodies are Associated With Fungal-Related Complications and Chronic Lung Allograft Dysfunction After Lung Transplantation

Fungal exposure and sensitization negatively affect outcomes in various respiratory diseases, however, the effect of fungal sensitization in lung transplant (LTx) recipients is still unknown. We performed a retrospective cohort study of prospectively collected data on circulating fungal specific IgG/IgE antibodies, and their correlation with fungal isolation, chronic lung allograft dysfunction (CLAD) and overall survival after LTx. 311 patients transplanted between 2014 and 2019 were included. Patients with elevated Aspergillus fumigatus or Aspergillus flavus IgG (10%) had more mold and Aspergillus species isolation (p = 0.0068 and p = 0.0047). Aspergillus fumigatus IgG was specifically associated with Aspergillus fumigatus isolation in the previous or consecutive year (AUC 0.60, p = 0.004 and AUC 0.63, p = 0.022, respectively). Elevated Aspergillus fumigatus or Aspergillus flavus IgG was associated with CLAD (p = 0.0355), but not with death. Aspergillus fumigatus, Aspergillus flavus or Aspergillus niger IgE was elevated in 19.3% of patients, but not associated with fungal isolation, CLAD or death. Mold isolation and Aspergillus species isolation from respiratory cultures were associated with CLAD occurrence (p = 0.0011 and p = 0.0005, respectively), and Aspergillus species isolation was also associated with impaired survival (p = 0.0424). Fungus-specific IgG could be useful in long-term follow-up post-LTx, as a non-invasive marker for fungal exposure, and thus a diagnostic tool for identifying patients at risk for fungal-related complications and CLAD.

Allogeneic Hematopoietic Stem Cell Transplantation After Prior Lung Transplantation for Hereditary Pulmonary Alveolar Proteinosis: A Case Report

Pulmonary alveolar proteinosis (PAP) is a rare, diffuse lung disorder characterized by surfactant accumulation in the small airways due to defective clearance by alveolar macrophages, resulting in impaired gas exchange. Whole lung lavage is the current standard of care treatment for PAP. Lung transplantation is an accepted treatment option when whole lung lavage or other experimental treatment options are ineffective, or in case of extensive pulmonary fibrosis secondary to PAP. A disadvantage of lung transplantation is recurrence of PAP in the transplanted lungs, especially in hereditary PAP. The hereditary form of PAP is an ultra-rare condition caused by genetic mutations in genes encoding for the granulocyte macrophage-colony stimulating factor (GM-CSF) receptor, and intrinsically affects bone marrow derived-monocytes, which differentiate into macrophages in the lung. Consequently, these macrophages typically display disrupted GM-CSF receptor-signaling, causing defective surfactant clearance. Bone marrow/hematopoietic stem cell transplantation may potentially reverse the lung disease in hereditary PAP. In patients with hereditary PAP undergoing lung transplantation, post-lung transplant recurrence of PAP may theoretically be averted by subsequent hematopoietic stem cell transplantation, which results in a graft-versus-disease (PAP) effect, and thus could improve long-term outcome. We describe the successful long-term post-transplant outcome of a unique case of end-stage respiratory failure due to hereditary PAP-induced pulmonary fibrosis, successfully treated by bilateral lung transplantation and subsequent allogeneic hematopoietic stem cell transplantation. Our report supports treatment with serial lung and hematopoietic stem cell transplantation to improve quality of life and prolong survival, without PAP recurrence, in selected patients with end-stage hereditary PAP.

Outcome of the Glenn procedure as definitive palliation in single ventricle patients

OBJECTIVES

In selected single ventricle patients, a Glenn procedure (SV-Glenn) may be considered as definitive palliation. Either the patient is unsuited to progress to a Fontan circulation or a SV-Glenn circulation is preferred. This study aimed at describing the clinical course, and long-term mortality/morbidity of SV-Glenn patients.

METHODS

All SV-Glenn patients followed at the University Hospitals Leuven before May 2018 were included. Patients who underwent, or were awaiting, TCPC completion and those who underwent a Glenn in the setting of a biventricular circulation one-and-a-half repair (OAHR), were excluded.

RESULTS

Of 65 Glenn-only patients identified, 21 (32%) had OAHR, whereas 44 (68%) were SV-Glenn patients. Of SV-Glenn patients, 19 died within 6 months after the Glenn procedure. Of 25 SV-Glenn survivors, median age at Glenn was 6.3 (IQR 1.2-29.7) years. Eight were unsuited for TCPC completion; in 17 SV-Glenn was preferred over TCPC completion. Over a median follow-up time of 11 (IQR 3-18) years after the Glenn procedure, 5 (20%) patients died. At latest follow-up 10 (40%) had heart failure, 5 (20%) had atrial and 4 (16%) ventricular arrhythmias, 2 (8%) a thromboembolic event, 7 (28%) required pacemaker implantation, and 2 (8%) had infective endocarditis but none developed cirrhosis or protein-losing enteropathy. Mean saturation at latest follow-up was 87 ± 7%.

CONCLUSION

SV-Glenn patients represent a unique and heterogeneous patient population. Outcome was reasonable, although comorbidities, such as heart failure and arrhythmias were not uncommon. In SV-Glenn patients, 'classic' complications related to Fontan physiology, such as cirrhosis and protein-losing enteropathy, were absent.

[A practical example of the application of the "Belgian geriatric evaluation and management program" within a general hospital]

A concrete realisation of the "Geriatric assessment and management program" as described in the arrêté royal within a general hospital: definition of the geriatric patient, his detection, his follow-up and the transmission of patient information. The analysis of the first results indicates the importance of the biographic and socio-economics factors. The optimisation of an early screening and the communication between caregivers are key aspects to enhance the care of this patients.