Investigating serum extracellular vesicles in Cystic Fibrosis

Extracellular vesicles and the lung: from disease pathogenesis to biomarkers and treatments

Nanosized extracellular vesicles (EVs) are released by all cells to convey cell-to-cell communication. EVs, including exosomes and microvesicles, carry an array of bioactive molecules, such as proteins and RNAs, encapsulated by a membrane lipid bilayer. Epithelial cells, endothelial cells, and various immune cells in the lung contribute to the pool of EVs in the lung microenvironment and carry molecules reflecting their cellular origin. EVs can maintain lung health by regulating immune responses, inducing tissue repair, and maintaining lung homeostasis. They can be detected in lung tissues and biofluids such as bronchoalveolar lavage fluid and blood, offering information about disease processes, and can function as disease biomarkers. Here, we discuss the role of EVs in lung homeostasis and pulmonary diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, pulmonary fibrosis, and lung injury. The mechanistic involvement of EVs in pathogenesis and their potential as disease biomarkers are discussed. Finally, the pulmonary field benefits from EVs as clinical therapeutics in severe pulmonary inflammatory disease, as EVs from mesenchymal stem cells attenuate severe respiratory inflammation in multiple clinical trials. Further, EVs can be engineered to carry therapeutic molecules for enhanced and broadened therapeutic opportunities, such as the anti-inflammatory molecule CD24. Finally, we discuss the emerging opportunity of using different types of EVs for treating severe respiratory conditions.

Innate Immunity in Cystic Fibrosis: Varied Effects of CFTR Modulator Therapy on Cell-to-Cell Communication

Cystic Fibrosis (CF) is a life-shortening, multi-organ disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Prominent clinical features of CF take place in the lung, hallmarked by cycles of bacterial infection and a dysfunctional inflammatory airway response, leading to eventual respiratory failure. Bidirectional crosstalk between epithelial cells, leukocytes (e.g., neutrophils, macrophages) and bacteria via release of intra-cellular mediators is key to driving inflammation in CF airways. In recent years, a highly effective combination of therapeutics targeting the CFTR defect have revolutionized treatment in CF. Despite these advancements and due to the complexity of the immune response in the CF airway, the full impact of highly effective modulator therapy (HEMT) on airway inflammation is not fully determined. This review provides the evidence to date on crosstalk mechanisms between host epithelium, leukocytes and bacteria and examines the effect of HEMT on both soluble and membrane-derived immune mediators in clinical samples. The varied effects of HEMT on expression of key proteases, cytokines and extracellular vesicles (EVs) in relation to clinical parameters is assessed. Advances in treatment with HEMT have shown potential in dampening the chronic inflammatory response in CF airways. However, to fully quell inflammation and maximize lung tissue resilience, further interventions may be necessary. Exploring the effects of HEMT on key immune mediators paves the way for identifying new anti-inflammatory approaches targeting host immune cell interactions, such as EV-directed lung therapies.

Extracellular vesicles in sputum of children with cystic fibrosis pulmonary exacerbations

Background

The aim of this study was to quantify mediators of neutrophilic inflammation within airway extracellular vesicles (EVs) of children treated for a cystic fibrosis (CF) pulmonary exacerbation (PEx).

Methods

EVs were isolated from stored sputum samples collected before and after antibiotic therapy for PEx between 2011 and 2013, and characterised by nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). Western blot analysis of EV protein extracts was used for EV canonical protein markers CD63, CD9 and flotillin-1 (FLOT1), as well as neutrophil elastase (NE), myeloperoxidase (MPO) and interleukin-8. The EV content of NE and MPO were expressed as ratios of NE/FLOT1 and MPO/FLOT1 protein band densities.

Results

Sputum samples from 21 children aged 13.3 (range 8.0-17.0) years were analysed. NTA showed high concentrations of particles at the size of small EVs (50-200 nm), and typical EV morphology was confirmed by TEM. CD63, CD9 and FLOT1 were detectable in all samples. Median (interquartile range (IQR)) NE/FLOT1 increased from 2.46 (1.68-5.25) before to 6.83 (3.89-8.89, p<0.001) after PEx therapy, and median (IQR) MPO/FLOT1 increased from 2.30 (1.38-4.44) before to 5.76 (3.45-6.94, p<0.01) after, while EV size remained unchanged. Improvement in lung function (percent predicted forced expiratory volume in 1 s (ppFEV1)) with PEx therapy correlated with NE EV content (r=0.657, p=0.001).

Conclusions

Airways of children with CF contain EVs that carry NE and MPO as cargo. The lower NE and MPO content at the time of PEx, compared with after therapy, and the correlation with pulmonary function suggest both a functional role of EVs in CF airway inflammation and the potential of EVs as a biomarker to monitor CF lung disease.

Beyond insulin: Unraveling the complex interplay of ER stress, oxidative damage, and CFTR modulation in CFRD

CF-related diabetes (CFRD) is a prevalent comorbidity in people with Cystic Fibrosis (CF), significantly impacting morbidity and mortality rates. This review article critically evaluates the current understanding of CFRD molecular mechanisms, including the role of CFTR protein, oxidative stress, unfolded protein response (UPR) and intracellular communication. CFRD manifests from a complex interplay between exocrine pancreatic damage and intrinsic endocrine dysfunction, further complicated by the deleterious effects of misfolded CFTR protein on insulin secretion and action. Studies indicate that ER stress and subsequent UPR activation play critical roles in both exocrine and endocrine pancreatic cell dysfunction, contributing to β-cell loss and insulin insufficiency. Additionally, oxidative stress and altered calcium flux, exacerbated by CFTR dysfunction, impair β-cell survival and function, highlighting the significance of antioxidant pathways in CFRD pathogenesis. Emerging evidence underscores the importance of exosomal microRNAs (miRNAs) in mediating inflammatory and stress responses, offering novel insights into CFRD's molecular landscape. Despite insulin therapy remaining the cornerstone of CFRD management, the variability in response to CFTR modulators underscores the need for personalized treatment approaches. The review advocates for further research into non-CFTR therapeutic targets, emphasizing the need to address the multifaceted pathophysiology of CFRD. Understanding the intricate mechanisms underlying CFRD will pave the way for innovative treatments, moving beyond insulin therapy to target the disease's root causes and improve the quality of life for individuals with CF.

SFTPB in serum extracellular vesicles as a biomarker of progressive pulmonary fibrosis

Progressive pulmonary fibrosis (PPF), defined as the worsening of various interstitial lung diseases (ILDs), currently lacks useful biomarkers. To identify novel biomarkers for early detection of patients at risk of PPF, we performed a proteomic analysis of serum extracellular vesicles (EVs). Notably, the identified candidate biomarkers were enriched for lung-derived proteins participating in fibrosis-related pathways. Among them, pulmonary surfactant-associated protein B (SFTPB) in serum EVs could predict ILD progression better than the known biomarkers, serum KL-6 and SP-D, and it was identified as an independent prognostic factor from ILD-gender-age-physiology index. Subsequently, the utility of SFTPB for predicting ILD progression was evaluated further in 2 cohorts using serum EVs and serum, respectively, suggesting that SFTPB in serum EVs but not in serum was helpful. Among SFTPB forms, pro-SFTPB levels were increased in both serum EVs and lungs of patients with PPF compared with those of the control. Consistently, in a mouse model, the levels of pro-SFTPB, primarily originating from alveolar epithelial type 2 cells, were increased similarly in serum EVs and lungs, reflecting pro-fibrotic changes in the lungs, as supported by single-cell RNA sequencing. SFTPB, especially its pro-form, in serum EVs could serve as a biomarker for predicting ILD progression.

Laboratory Tools to Predict CFTR Modulator Therapy Effectiveness and to Monitor Disease Severity in Cystic Fibrosis

The implementation of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator drugs into clinical practice has been attaining remarkable therapeutic outcomes for CF, a life-threatening autosomal recessive genetic disease. However, there is elevated CFTR allelic heterogeneity, and various individuals carrying (ultra)rare CF genotypes remain without any approved modulator therapy. Novel translational model systems based on individuals' own cells/tissue are now available and can be used to interrogate in vitro CFTR modulator responses and establish correlations of these assessments with clinical features, aiming to provide prediction of therapeutic effectiveness. Furthermore, because CF is a progressive disease, assessment of biomarkers in routine care is fundamental in monitoring treatment effectiveness and disease severity. In the first part of this review, we aimed to focus on the utility of individual-derived in vitro models (such as bronchial/nasal epithelial cells and airway/intestinal organoids) to identify potential responders and expand personalized CF care. Thereafter, we discussed the usage of CF inflammatory biomarkers derived from blood, bronchoalveolar lavage fluid, and sputum to routinely monitor treatment effectiveness and disease progression. Finally, we summarized the progress in investigating extracellular vesicles as a robust and reliable source of biomarkers and the identification of microRNAs related to CFTR regulation and CF inflammation as novel biomarkers, which may provide valuable information for disease prognosis.