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.

Angiogenesis in Chronic Thromboembolic Pulmonary Hypertension: A Janus-Faced Player?

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare form of pulmonary hypertension characterized by the presence of organized thrombi that obstruct pulmonary arteries, ultimately leading to right heart failure and death. Among others, impaired angiogenesis and inflammatory thrombosis have been shown to contribute to the progression of CTEPH. In this review, we summarize the 2-faced nature of angiogenesis in both thrombus formation and resolution in the context of CTEPH and highlight the dual role of angiogenesis and neovascularization in resolving venous thrombi. Furthermore, we discuss relevant in vitro and in vivo models that support the benefits or drawbacks of angiogenesis in CTEPH progression. We discuss the key pathways involved in modulating angiogenesis, particularly the underexplored role of TGFß (transforming growth factor-beta) signaling in driving fibrosis as an integral element of CTEPH pathogenesis. We finally explore innovative treatment strategies that target angiogenic pathways. These strategies have the potential to pioneer preventive, inventive, or alternative therapeutic options for patients with CTEPH who may not qualify for surgical interventions. Moreover, they could be used synergistically with established treatments such as pulmonary endarterectomy or balloon pulmonary angioplasty. In summary, this review emphasizes the crucial role of angiogenesis in the development of in fibrothrombotic tissue, a major pathological characteristic of CTEPH.

Chronic oxytocin administration stimulates the oxytocinergic system in children with autism.

Clinical efficacy of intranasal administration of oxytocin is increasingly explored in autism spectrum disorder, but to date, the biological effects of chronic administration regimes on endogenous oxytocinergic function are largely unknown. Here exploratory biological assessments from a completed randomized, placebo-controlled trial showed that children with autism (n = 79, 16 females) receiving intranasal oxytocin for four weeks (12 IU, twice daily) displayed significantly higher salivary oxytocin levels 24 hours after the last oxytocin nasal spray administration, but no longer at a four-week follow up session. Regarding salivary oxytocin receptor gene (OXTR) epigenetics (DNA-methylation), oxytocin-induced reductions in OXTR DNA-methylation were observed, suggesting a facilitation of oxytocin receptor expression in the oxytocin compared to the placebo group. Notably, heightened oxytocin levels post-treatment were significantly associated with reduced OXTR DNA-methylation and improved feelings of secure attachment. These findings indicate that four weeks of chronic oxytocin administration stimulated the endogenous oxytocinergic system in children with autism.

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.

Endogenous oxytocin levels in children with autism: Associations with cortisol levels and oxytocin receptor gene methylation.

Alterations in the brain's oxytocinergic system have been suggested to play an important role in the pathophysiology of autism spectrum disorder (ASD), but insights from pediatric populations are sparse. Here, salivary oxytocin was examined in the morning (AM) and afternoon (PM) in school-aged children with (n = 80) and without (n = 40) ASD (boys/girls 4/1), and also characterizations of DNA methylation (DNAm) of the oxytocin receptor gene (OXTR) were obtained. Further, cortisol levels were assessed to examine links between the oxytocinergic system and hypothalamic-pituitary-adrenal (HPA) axis signaling. Children with ASD displayed altered (diminished) oxytocin levels in the morning, but not in the afternoon, after a mildly stress-inducing social interaction session. Notably, in the control group, higher oxytocin levels at AM were associated with lower stress-induced cortisol at PM, likely reflective of a protective stress-regulatory mechanism for buffering HPA stress activity. In children with ASD, on the other hand, a significant rise in oxytocin levels from the morning to the afternoon was associated with a higher stress-induced cortisol release in the afternoon, likely reflective of a more reactive stress regulatory release of oxytocin for reactively coping with heightened HPA activity. Regarding epigenetic modifications, no overall pattern of OXTR hypo- or hypermethylation was evident in ASD. In control children, a notable association between OXTR methylation and levels of cortisol at PM was evident, likely indicative of a compensatory downregulation of OXTR methylation (higher oxytocin receptor expression) in children with heightened HPA axis activity. Together, these observations bear important insights into altered oxytocinergic signaling in ASD, which may aid in establishing relevant biomarkers for diagnostic and/or treatment evaluation purposes targeting the oxytocinergic system in ASD.

Impairment of Angiogenesis-Driven Clot Resolution Is a Key Event in the Progression to Chronic Thromboembolic Pulmonary Hypertension: Validation in a Novel Rabbit Model.

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening condition and rare complication of acute pulmonary embolism. Mechanisms underlying impaired clot resolution and in sustained fibrothrombotic obstruction of the pulmonary arterial bed remain poorly understood. Since defective angiogenesis correlated to defective clot resolution based on observations in surgical material from patients with CTEPH, we aimed to validate its crucial pathogenic role by intrathrombus inhibition of angiogenesis in a novel CTEPH rabbit model. METHODS: We aimed to compare whether intrathrombus administration of an antifibrinolytic agent, tranexamic acid, or an inhibitor of angiogenesis, SU5416, would contribute to CTEPH progression. Both products were administered on a weekly basis by autologous clot embolization in rabbits. Right ventricular pressure was monitored by telemetry, right ventricular function by transthoracic echocardiography, and a complete pulmonary hemodynamic evaluation was obtained through right heart catheterization. Markers of inflammation, endothelial dysfunction, heart failure, and fibrinolysis were measured in plasma. Pulmonary vessel remodeling was analyzed by immunohistochemistry. RESULTS: Impairing intrathrombus angiogenesis by repeatedly embolizing autologous blood clots containing SU5416 resulted in elevated mean pulmonary arterial pressure (38 mm Hg), increased indexed pulmonary vascular resistance, and enhanced right ventricular hypertrophy (80%, 1.9-fold, 36%, respectively, compared with rabbits embolized with clots containing an antifibrinolytic agent). This was caused by both obstruction of large pulmonary arteries with fibrothrombotic material and muscularization of pulmonary microvessels, and accompanied by inflammatory cell infiltration and increased circulating endothelin-1. CONCLUSIONS: The key role of angiogenesis-driven clot resolution was validated in a reliable small-animal model reproducing the major pathophysiological hallmarks of CTEPH.

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.

Pulmonary graft-versus-host disease and chronic lung allograft dysfunction: two sides of the same coin?

Allogeneic haematopoietic stem-cell transplantation (HSCT) and lung transplantation are both established life-saving treatment options for carefully selected patients with various haematological disorders or end-stage lung diseases, respectively. However, long-term survival after allogeneic HSCT is severely limited by chronic graft-versus-host disease (cGVHD)-of which pulmonary cGVHD in particular has a very poor prognosis-and long-term survival after lung transplantation is hampered by chronic lung allograft dysfunction (CLAD). Both pulmonary cGVHD and CLAD are characterised by similar underlying immunopathology, which results in transplant-related pulmonary fibrosis and structural lung remodelling, leading to respiratory dysfunction. Accurate clinical identification and appropriate management is of utmost importance to allow for timely diagnosis, to further optimise current preventive and treatment strategies of pulmonary cGVHD and CLAD, and to ameliorate quality of life and long-term outcomes after allogeneic HSCT and lung transplantation. In this Review, we provide a unique state-of-the-art perspective of both entities for respiratory care practitioners.

A Focused Review on Primary Graft Dysfunction after Clinical Lung Transplantation: A Multilevel Syndrome.

Primary graft dysfunction (PGD) is the clinical syndrome of acute lung injury after lung transplantation (LTx). However, PGD is an umbrella term that encompasses the ongoing pathophysiological and -biological mechanisms occurring in the lung grafts. Therefore, we aim to provide a focused review on the clinical, physiological, radiological, histological and cellular level of PGD. PGD is graded based on hypoxemia and chest X-ray (CXR) infiltrates. High-grade PGD is associated with inferior outcome after LTx. Lung edema is the main characteristic of PGD and alters pulmonary compliance, gas exchange and circulation. A conventional CXR provides a rough estimate of lung edema, while a chest computed tomography (CT) results in a more in-depth analysis. Macroscopically, interstitial and alveolar edema can be distinguished below the visceral lung surface. On the histological level, PGD correlates to a pattern of diffuse alveolar damage (DAD). At the cellular level, ischemia-reperfusion injury (IRI) is the main trigger for the disruption of the endothelial-epithelial alveolar barrier and inflammatory cascade. The multilevel approach integrating all PGD-related aspects results in a better understanding of acute lung failure after LTx, providing novel insights for future therapies.