The relationship between inflammation and remodeling in childhood asthma: A systematic review

Impulse oscillometry bronchodilator response in preschool children

BACKGROUND

In preschoolers, performing an acceptable spirometry and measuring bronchodilator response (BDR) is challenging; in this context, impulse oscillometry (IOS) represents a valid alternative. However, more studies on the standardization of BDR for IOS in young children are required.

OBJECTIVE

The objective of the study was to identify optimal thresholds to define a positive BDR test with IOS in preschoolers with suspected asthma.

METHODS

Children aged 3-6 years with suspected asthma and their lung function investigated with both IOS and spirometry pre- and post-BDR were retrospectively analyzed. The spirometric BDR was defined as positive when the change of FEV1 was ≥12% or ≥200 mL. The oscillometric BDR was defined as positive in case of change of at least -40% in R5, +50% in X5, and -80% in AX.

RESULTS

Among 72 patients, 36 (age 5.2 ± 1 years; 64% boys) were selected for the subsequent analysis according to ATS/ERS quality criteria of measurements; specifically, 19 patients did not meet IOS and 36 did not meet spirometry criteria. The spirometric BDR was found positive in seven subjects (19.4%); conversely, a positive oscillometric BDR was identified in four patients (11.1%). No patient presented a positive BDR response with both methods. In IOS, the mean decrease in R5 and AX was 19.9% ± 10% and 44% ± 22.1%, and the mean increase in X5 was 23.3% ± 17.8%, respectively. A decrease in R5 of 25.7% (AUC 0.77, p = .03) and an increase in X5 of 25.7% (AUC 0.75, p = .04) showed the best combination of sensitivity and specificity to detect an increase of FEV1 ≥ 12% and/or ≥200 mL.

CONCLUSION

The IOS represents a valid alternative to spirometry to measure BDR in preschool children and should be the gold standard in this age group. We are considering a decrease of 26% in R5 and an increase of 26% in X5 as diagnostic threshold for BDR.

Functional analysis of airway remodeling is related with fibrotic mediators in asthmatic children

BACKGROUND

Asthmatic children present variable degrees of airway inflammation, remodeling, and resistance, which correlate with disease control and severity. The chronic inflammatory process of the airway triggers airway remodeling, which reflects the degree of airway resistance. Pro-inflammatory and pro-fibrotic mediators are centrally involved in this process.

OBJECTIVE

To investigate whether the levels of pulmonary and systemic pro-inflammatory and pro-fibrotic mediators present a correlation with the resistance of the respiratory system and of the proximal and distal airways.

METHODS

39 Asthmatic children (persistent mild and moderate) and 39 non-asthmatic children (both between 6 and 13 years old) were evaluated for anthropometric characteristics, lung function and mechanics, and pulmonary and systemic immune responses.

RESULTS

Asthmatic children showed an increased number of blood eosinophils (p < 0.04), basophils (p < 0.04), monocytes (p < 0.002) and lymphocytes (p < 0.03). In addition, asthmatic children showed impaired lung function, as demonstrated by FEV1 (p < 0.0005) and FEV1/FVC (p < 0.004), decreased total resistance of the respiratory system (R5Hz; p < 0.009), increased resistance of the proximal airways (R20Hz; p < 0.02), increased elastance (Z5Hz; p < 0.02) and increased reactance (X5Hz; p < 0.002) compared to non-asthmatic children. Moreover, the following inflammatory factors were significantly higher in asthmatic than non-asthmatic children: GM-CSF in the breath condensate (BC) (p < 0.0001) and in the serum (p < 0.0001); TGF-beta in the BC (p < 0.0001) and in the serum (p < 0.004); IL-5 in the BC (p < 0.02) and in the serum (p < 0.01); IL-4 in the serum (p < 0.0002).

CONCLUSIONS

Impulse oscillometry is a sensitive method to detect airway resistance in persistent mild and moderate asthmatic children, an event followed by increased levels of pro-inflammatory and pro-fibrotic mediators.

Research trends on airway remodeling: A bibliometrics analysis

Background

Airway remodeling is an essential pathological basis of respiratory diseases such as asthma and COPD, which is significantly related to pulmonary function and clinical symptoms. And pulmonary disease can be improved by regulating airway remodeling. This study aimed to establish a knowledge map of airway remodeling to clarify current research hotspots and future research trends.

Methods

A comprehensive search was performed to analyze all relevant articles on airway remodeling using the Web of Science Core Collection Database from January 01, 2004 to June 03, 2023.2 reviewers screened the retrieved literature. Besides, the CiteSpace (6.2. R3) and VOSviewer (1.6.19) were utilized to visualize the research focus and trend regarding the effect of airway remodeling.

Results

A total of 4077 articles about airway remodeling were retrieved. The United States is the country with the most published literature, underscoring the country's role in airway remodeling. In recent years, China has been the country with the fastest growth in the number of published literature, suggesting that China will play a more critical role in airway remodeling in the future. From the perspective of co-operation among countries, European co-operation was closer than Asian co-operation. The co-citation analysis showed that 98,313 citations were recorded in 3594 articles, and 25 clusters could be realized. In recent years, Burst detection shows that oxidative stress and epithelial-mesenchymal transition are hot words.

Conclusions

Based on the bibliometric analysis of airway remodeling studies in the past 20 years, a multi-level knowledge structure map was drawn, it mainly includes countries, institutions, research fields, authors, journals, keywords and so on. The research directions represented by obstructive airway disease, PDGF-BB treatment of airway smooth muscle, allergen-induced airway remodeling, extracellular matrix, and non-coding RNA are the research hotspots in the field of airway remodeling. While the risk factors for airway remodeling, the application of new noninvasively assessing tools, biomarkers as well as The molecular mechanism represented by EMT and autophagy had been frontiers in recent years.

Unravelling the respiratory health path across the lifespan for survivors of preterm birth

Many survivors of preterm birth will have abnormal lung development, reduced peak lung function and, potentially, an increased rate of physiological lung function decline, each of which places them at increased risk of chronic obstructive pulmonary disease across the lifespan. Current rates of preterm birth indicate that by the year 2040, around 50 years since the introduction of surfactant therapy, more than 700 million individuals will have been born prematurely-a number that will continue to increase by about 15 million annually. In this Personal View, we describe current understanding of the impact of preterm birth on lung function through the life course, with the aim of putting this emerging health crisis on the radar for the respiratory community. We detail the potential underlying mechanisms of prematurity-associated lung disease and review current approaches to prevention and management. Furthermore, we propose a novel way of considering lung disease after preterm birth, using a multidimensional model to determine individual phenotypes of lung disease-a first step towards optimising management approaches for prematurity-associated lung disease.

Asthma Phenotypes in the Era of Personalized Medicine

Asthma is a widespread disease affecting approximately 300-million people globally. This condition leads to significant morbidity, mortality, and economic strain worldwide. Recent clinical and laboratory research advancements have illuminated the immunological factors contributing to asthma. As of now, asthma is understood to be a heterogeneous disease. Personalized medicine involves categorizing asthma by its endotypes, linking observable characteristics to specific immunological mechanisms. Identifying these endotypic mechanisms is paramount in accurately profiling patients and tailoring therapeutic approaches using innovative biological agents targeting distinct immune pathways. This article presents a synopsis of the key immunological mechanisms implicated in the pathogenesis and manifestation of the disease's phenotypic traits and individualized treatments for severe asthma subtypes.

Early Prediction of Asthma

The clinical manifestations of asthma in children are highly variable, are associated with different molecular and cellular mechanisms, and are characterized by common symptoms that may diversify in frequency and intensity throughout life. It is a disease that generally begins in the first five years of life, and it is essential to promptly identify patients at high risk of developing asthma by using different prediction models. The aim of this review regarding the early prediction of asthma is to summarize predictive factors for the course of asthma, including lung function, allergic comorbidity, and relevant data from the patient's medical history, among other factors. This review also highlights the epigenetic factors that are involved, such as DNA methylation and asthma risk, microRNA expression, and histone modification. The different tools that have been developed in recent years for use in asthma prediction, including machine learning approaches, are presented and compared. In this review, emphasis is placed on molecular mechanisms and biomarkers that can be used as predictors of asthma in children.

Severe pediatric asthma endotypes: current limits and future perspectives

INTRODUCTION

Although rare, pediatric severe therapy-resistant asthma (STRA) is a highly heterogeneous, resource-demanding disease that differs significantly from severe adult asthma and whose pathogenesis is still poorly understood.

AREAS COVERED

This review summarizes the latest 10 years of English-written studies defining pediatric STRA endotypes using lung-specific techniques such as bronchoalveolar lavage and endobronchial biopsy. Results of the studies and limits on the field are discussed, together with some future perspectives.

EXPERT OPINION

Over the years, it has become increasingly clear that 'one size does not fit all" in asthma. However, "Does an extremely tailored size fit more than one?'. Only using multicentric, longitudinal pediatric studies, will we be able to answer. Three issues could be particularly critical for future research. First, to provide, if existing, a distinction between prepuberal STRA and puberal STRA endotypes to understand the transition from pediatric to adult STRA and to design effective, tailored therapies in adolescents, usually suffering from poorer asthma control. Second, design early treatments for pediatric airway remodeling to preserve lifelong good lung function. Finally, to better characterize inflammation before and during biological therapies, to provide clues on whether to stop or change treatments.

ADP Ribosylation Factor 6 Relieves Airway Inflammation and Remodeling by Inhibiting Ovalbumin Induced-Epithelial Mesenchymal Transition in Experimental Asthma, Possibly by Regulating of E2F Transcription Factor 8

BACKGROUND

Childhood asthma is a major global health concern. ADP-ribosylation factor 6 (ARF6) is a low-molecular-weight GTPase; however, its role in childhood asthma remains unclear.

METHODS

Ovalbumin (OVA)-challenged neonatal mice and transforming growth factor-β1 (TGF-β1)-induced BEAS-2B cells were used as in vivo and in vitro models of childhood asthma, respectively.

RESULTS

Upon OVA stimulation, ARF6 expression was upregulated in the lung tissue. Neonatal mice administered SehinH3 (an ARF6 inhibitor) exhibited improved pulmonary pathological injury, along with reduced inflammatory cell infiltration in the lungs and cytokine release in bronchial alveolar lavage fluid and serum (interleukin [IL]-3, IL-5, IL-13, IgE, and OVA-specific IgE). SehinH3 treatment restrained epithelial - mesenchymal transition (EMT) in the lungs of asthmatic mice, as evidenced by increased E-cadherin and decreased N-cadherin and α-smooth muscle actin expression. Different TGF-β1 exposures to BEAS-2B cells induced a time- and dose-dependent increase in ARF6 expression in vitro. Upon TGF-β1 stimulation, ARF6 knockdown repressed EMT and SehinH3 treatment caused similar results in BEAS-2B cells. The transcription factor E2F8 is involved in diverse biological functions and its increased expression was confirmed in vivo and in vitro. Dual-luciferase assays confirmed that E2F8 binds to the ARF6 promoter and promotes its transcriptional activity. In vitro results revealed that E2F8 silencing suppressed EMT, whereas rescue experiments showed that ARF6 overexpression partly reversed these phenomena.

CONCLUSION

Our study showed that ARF6 is associated with childhood asthma progression and may be positively regulated by E2F8. These results provide insight into the pathogenesis and treatment of childhood asthma.

House Dust Mite and Cat Dander Extract Induce Asthma-Like Histopathology with an Increase of Mucosal Mast Cells in a Guinea Pig Model

Background

Asthma is a chronic inflammatory disease with structural changes in the lungs defined as airway remodelling. Mast cell responses are important in asthma as they, upon activation, release mediators inducing bronchoconstriction, inflammatory cell recruitment, and often remodelling of the airways. As guinea pigs exhibit anatomical, physiological, and pharmacological features resembling human airways, including mast cell distribution and mediator release, we evaluated the effect of extracts from two common allergens, house dust mite (HDM) and cat dander (CDE), on histopathological changes and the composition of tryptase- and chymase-positive mast cells in the guinea pig lungs.

Methods

Guinea pigs were exposed intranasally to HDM or CDE for 4, 8, and 12 weeks, and airway histology was examined at each time point. Hematoxylin and eosin, Picro-Sirius Red, and Periodic Acid-Schiff staining were performed to evaluate airway inflammation, collagen deposition, and mucus-producing cells. In addition, Astra blue and immunostaining against tryptase and chymase were used to visualize mast cells.

Results

Repetitive administration of HDM or CDE led to the accumulation of inflammatory cells into the proximal and distal airways as well as increased airway smooth muscle mass. HDM exposure caused subepithelial collagen deposition and mucus cell hyperplasia at all three time points, whereas CDE exposure only caused these effects at 8 and 12 weeks. Both HDM and CDE induced a substantial increase in mast cells after 8 and 12 weeks of challenges. This increase was primarily due to mast cells expressing tryptase, but not chymase, thus indicating mucosal mast cells.

Conclusions

We here show that exposure to HDM and CDE elicits asthma-like histopathology in guinea pigs with infiltration of inflammatory cells, airway remodelling, and accumulation of primarily mucosal mast cells. The results together encourage the use of HDM and CDE allergens for the stimulation of a clinically relevant asthma model in guinea pigs.

From Beneath the Skin to the Airway Wall: Understanding the Pathological Role of Adipose Tissue in Comorbid Asthma-Obesity

This article provides a contemporary report on the role of adipose tissue in respiratory dysfunction. Adipose tissue is distributed throughout the body, accumulating beneath the skin (subcutaneous), around organs (visceral), and importantly in the context of respiratory disease, has recently been shown to accumulate within the airway wall: "airway-associated adipose tissue." Excessive adipose tissue deposition compromises respiratory function and increases the severity of diseases such as asthma. The mechanisms of respiratory impairment are inflammatory, structural, and mechanical in nature, vary depending on the anatomical site of deposition and adipose tissue subtype, and likely contribute to different phenotypes of comorbid asthma-obesity. An understanding of adipose tissue-driven pathophysiology provides an opportunity for diagnostic advancement and patient-specific treatment. As an exemplar, the potential impact of airway-associated adipose tissue is highlighted, and how this may change the management of a patient with asthma who is also obese. © 2023 American Physiological Society. Compr Physiol 13:4321-4353, 2023.

Symptom-driven inhaled corticosteroid/long-acting beta-agonist therapy for adult patients with asthma who are non-adherent to daily maintenance inhalers: a study protocol for a pragmatic randomized controlled trial

BACKGROUND

While inhaled corticosteroids (ICS) are considered the essential foundation of most asthma therapy, ICS inhaler nonadherence is a notoriously common problem and a significant cause of asthma-related morbidity. Partially acknowledging the problem of nonadherence, international organizations recently made paradigm-shifting recommendations that all patients with mild-to-moderate persistent asthma be considered for symptom-driven ICS-containing inhalers rather than relying on adherence to traditional maintenance ICS inhalers and symptom-driven short-acting beta-agonists (SABA). With this new approach, asthma patients are at least exposed to the important anti-inflammatory effects of ICS-containing inhalers when their symptom reliever inhaler is deployed due to acute symptoms.

METHODS

This study will (Part 1) complete a pragmatic randomized controlled trial to evaluate if an inhaler strategy that utilizes symptom-driven ICS inhalers is particularly beneficial in maintenance ICS inhaler non-adherent asthma patients, and (Part 2) use a dissemination and implementation (D&I) science conceptual framework to better understand patients' and providers' views of inhaler nonadherence. This study, which will have an option of taking place entirely remotely, will use a Food and Drug Administration (FDA)-approved electronic sensor (Hailie® sensor) to monitor inhaler adherence and includes semi-structured interviews guided by the Consolidated Framework for Implementation Research (CFIR).

DISCUSSION

This study is assessing the problem of nonadherence using a D&I implementation science research lens while testing a new inhaler approach to potentially ameliorate the detrimental consequences of maintenance inhaler nonadherence. We hypothesize that the use of a symptom-driven ICS/LABA management strategy, as compared to traditional maintenance ICS treatment and symptom-driven SABA, will lead to improved adherence to an asthma treatment strategy, decreased asthma-related morbidity, less cumulative ICS exposure, and greater patient satisfaction with an inhaler approach.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05111262. Registered on November 8, 2021.

ZEB1 recruit Brg1 to regulate airway remodeling epithelial-mesenchymal transition in asthma

What is the central question of this study? The aim was to investigate the function of Brg1 in airway remodeling epithelial-mesenchymal transition (EMT) of asthma and identify the transcription factor (TF) of Brg1 which bind to the protomer of E-cadherin. What is the main finding and its importance? This study highlighted an important molecular mechanism involving chromatin remodeling factor Brahma-related gene-1 (Brg1) that played a critical role in airway remodeling EMT of asthma and demonstrated ZEB1 was the key TF recruiting Brg1. This finding might offer new insights into gene-based therapy for asthma. ABSTRACT: Epithelial-mesenchymal transition (EMT) of airway remodeling happens in children with asthma. Reduction of epithelial marker E-cadherin is reported to be one of the initiating factors of EMT. Our previous study shows that chromatin remodeling factor Brahma-related gene-1 (Brg1) could regulate the expression of E-cadherin indirectly, but the transcription factor (TF) involved in the recruitment of Brg1 in asthma is unknown. Here, we studied the function of Brg1 in an ovalbumin (OVA)-induced asthma model (lung-specific conditional Brg1 (Brg1^-/- ) knockdown mice) and human bronchial epithelial 16HBE cells stably expressing Brg1 shRNA. Our results showed that Brg1 was involved in epithelial-mesenchymal transition in asthmatic mice by detecting the expression of EMT markers. Meanwhile, we identified that Brg1 participated in the TGF-β induced EMT of 16HBE cells. We observed that Zinc Finger E-Box Binding Homeobox 1 (ZEB1) and Brg1 colocalized in the EMT of TGF-β induced 16HBE cells. Further results revealed that ZEB1 recruited Brg1 and bound to the promoter region (+3563/3715) to regulate E-cadherin expression. Thus, ZEB1 might be the key TF to recruit Brg1 in airway remodeling EMT of asthma and might be a novel therapeutic target. This article is protected by copyright. All rights reserved.

Aspergillus fumigatus-Host Interactions Mediating Airway Wall Remodelling in Asthma

Asthma is a chronic heterogeneous respiratory condition that is mainly associated with sensitivity to airborne agents such as pollen, dust mite products and fungi. Key pathological features include increased airway inflammation and airway wall remodelling. In particular, goblet cell hyperplasia, combined with excess mucus secretion, impairs clearance of the inhaled foreign material. Furthermore, structural changes such as subepithelial fibrosis and increased smooth muscle hypertrophy collectively contribute to deteriorating airway function and possibility of exacerbations. Current pharmacological therapies focused on airway wall remodelling are limited, and as such, are an area of unmet clinical need. Sensitisation to the fungus, Aspergillus fumigatus, is associated with enhanced asthma severity, bronchiectasis, and hospitalisation. How Aspergillus fumigatus may drive airway structural changes is unclear, although recent evidence points to a central role of the airway epithelium. This review provides an overview of the airway pathology in patients with asthma and fungal sensitisation, summarises proposed airway epithelial cell-fungal interactions and discusses the initiation of a tissue remodelling response. Related findings from in vivo animal models are included given the limited analysis of airway pathology in patients. Lastly, an important role for Aspergillus fumigatus-derived proteases in triggering a cascade of damage-repair events through upregulation of airway epithelial-derived factors is proposed.

Airway Wall Remodeling in Childhood Asthma-A Personalized Perspective from Cell Type-Specific Biology

Airway wall remodeling is a pathology occurring in chronic inflammatory lung diseases including asthma, chronic obstructive pulmonary disease, and fibrosis. In 2017, the American Thoracic Society released a research statement highlighting the gaps in knowledge and understanding of airway wall remodeling. The four major challenges addressed in this statement were: (i) the lack of consensus to define “airway wall remodeling” in different diseases, (ii) methodologic limitations and inappropriate models, (iii) the lack of anti-remodeling therapies, and (iv) the difficulty to define endpoints and outcomes in relevant studies. This review focuses on the importance of cell-cell interaction, especially the bronchial epithelium, in asthma-associated airway wall remodeling. The pathology of “airway wall remodeling” summarizes all structural changes of the airway wall without differentiating between different pheno- or endo-types of asthma. Indicators of airway wall remodeling have been reported in childhood asthma in the absence of any sign of inflammation; thus, the initiation event remains unknown. Recent studies have implied that the interaction between the epithelium with immune cells and sub-epithelial mesenchymal cells is modified in asthma by a yet unknown epigenetic mechanism during early childhood.

The asthma predictive index as a surrogate diagnostic tool in preschoolers: Analysis of a longitudinal birth cohort

Diagnosing asthma in preschool children remains an unsolved challenge, at a time when early identification would allow for better education and treatment to prevent morbidity and lung function deterioration.

OBJECTIVE

To evaluate if the asthma predictive index (API) can be used as surrogate for asthma diagnosis in preschoolers.

METHODS

Birth cohort of 339 pregnant women enrolled at delivery and their offspring, who were followed for atopy, wheezing, and other respiratory illnesses through 30 months of age. The API was determined at 30 months of age by the researchers; and examined its association with physician-diagnosed asthma during the first 30 months, made independently by the primary care physician not involved in the study.

RESULTS

Among 307 offspring with complete follow-up, 44 (14.3%) were API+. Maternal body mass index, maternal education, past oral contraceptive use, birthweight, placenta weight, age of daycare at 12 m, gastroesophageal reflux disease at 12 m, acute otitis media at 18 m, bronchiolitis, croup and pneumonia, cord blood adiponectin were all associated with API+. In the multivariable analysis, API+ was associated with almost sixfold odds of asthma diagnosis (adjusted OR = 5.7, 95% CI [2.6-12.3]), after adjusting for the relevant covariates above including respiratory infections like bronchiolitis and pneumonia. The API sensitivity was 48%, specificity 92%, 61% PPV, 88% NPV, 6.4 LR+, 0.56 LR-, 0.84 diagnosis accuracy. The adjusted odds for asthma was 11.4.

CONCLUSIONS

This longitudinal birth cohort suggests, for first time, that API (a structured definition for asthma), could be used as a diagnostic tool, not only as a prognostic tool, in toddlers and preschoolers.

Fetal Growth Restriction and Asthma: Is the Damage Done?

Trajectories of airway remodeling and functional impairment in asthma are consistent with the notion that airway pathology precedes or coincides with the onset of asthma symptoms and may be present at birth. An association between intrauterine growth restriction (IUGR) and asthma development has also been established, and there is value in understanding the underlying mechanism. This review considers airway pathophysiology as a consequence of IUGR that increases susceptibility to asthma.

Pharmacological ablation of the airway smooth muscle layer-Mathematical predictions of functional improvement in asthma

Airway smooth muscle (ASM) plays a major role in acute airway narrowing and reducing ASM thickness is expected to attenuate airway hyper‐responsiveness and disease burden. There are two therapeutic approaches to reduce ASM thickness: (a) a direct approach, targeting specific airways, best exemplified by bronchial thermoplasty (BT), which delivers radiofrequency energy to the airway via bronchoscope; and (b) a pharmacological approach, targeting airways more broadly. An example of the less well‐established pharmacological approach is the calcium‐channel blocker gallopamil which in a clinical trial effectively reduced ASM thickness; other agents may act similarly. In view of established anti‐proliferative properties of the macrolide antibiotic azithromycin, we examined its effects in naive mice and report a reduction in ASM thickness of 29% (p < .01). We further considered the potential functional implications of this finding, if it were to extend to humans, by way of a mathematical model of lung function in asthmatic patients which has previously been used to understand the mechanistic action of BT. Predictions show that pharmacological reduction of ASM in all airways of this magnitude would reduce ventilation heterogeneity in asthma, and produce a therapeutic benefit similar to BT. Moreover there are differences in the expected response depending on disease severity, with the pharmacological approach exceeding the benefits provided by BT in more severe disease. Findings provide further proof of concept that pharmacological targeting of ASM thickness will be beneficial and may be facilitated by azithromycin, revealing a new mode of action of an existing agent in respiratory medicine.

Measuring the Contributions of Basal Laminar Deposit and Bruch's Membrane in Age-Related Macular Degeneration

Purpose

Basal laminar deposit (BLamD) is a consistent finding in age-related macular degeneration (AMD). We quantified BLamD thickness, appearance, and topography in eyes of aged donors with and without AMD and evaluated its relationship to other components of the retinal pigment epithelium-basal lamina/Bruch's membrane (RPE-BL-BrM) complex.

Methods

Donor eyes (n = 132) were classified as normal (n = 54), early to intermediate AMD (n = 24), geographic atrophy (GA; n = 13), and neovascular AMD (NV; n = 41). In high-resolution histology, we assessed RPE, BLamD, and BrM thicknesses and phenotypes at 3309 predefined locations in the central (foveal and perifovea) and superior (perifoveal) sections. Pre-mortem optical coherence tomography (OCT) imaging of a 90-year-old woman was compared to postmortem histopathology.

Results

In non-atrophic areas of AMD eyes, the RPE-BLamD is thick (normal = 13.7 µm, early-intermediate = 16.8 µm, GA = 17.4 µm, NV = 18.7 µm), because the BLamD is thick (normal = 0.3 µm, early-intermediate = 5.5 µm, GA = 4.1 µm, NV = 5.3 µm). RPE layer thickness is similar across these stages. Disease-associated variants of BLamD (thick, late, basal mounds) cluster subfoveally. A thick BLamD is visible on OCT as a hyporeflective split in the RPE-BL-BrM complex. BrM is thin (3.5 µm) in NV (normal = 4.2 µm, early to intermediate = 4.4 µm, and GA = 4.2 µm).

Conclusions

The RPE-BL-BrM complex is thick in AMD, driven by the accumulation and expansion of BLamD rather than expansion of either three-layer BrM, RPE-BL, or RPE. BLamD is clinically appreciable by OCT in some patients as a non-neovascular "split RPE-BL-BrM complex" or "double-layer sign." BLamD may contribute toward the formation and progression of high-risk drusen yet also exhibit protective properties.

Lost in transition: biomarkers of remodeling in patients with asthma

PURPOSE OF REVIEW

'Biomarkers of remodeling' represent a loose collection of features referring to several biological adaptations of the lung to cope with stressing factors. In addition, remodel-'ing' infers a dynamic process that would require a spatiotemporal resolution. This review focuses on different aspects of remodeling in pediatric and adult care.

RECENT FINDINGS

This review will cover aspects of pediatric remodeling, adult remodeling and techniques and procedures to adequately assess remodeling across different age spectra. In pediatrics, the onset and first features of remodeling are discussed and the continuation into adolescence is addressed. For adults, this review addresses predominant features of remodeling throughout the adult life span and whether there are currently interventions available to treat or reverse remodeling.

SUMMARY

The term 'remodeling' is often referred to via biomarkers that reflect the endstage of a process, although it rather reflects a continuous process starting in childhood and progressing to all age-levels in patients with asthma. Hence, only few biomarkers or surrogates are able to 'capture' its spatiotemporal component, and hardly any are ready for routine use in clinical practice. Given the clinical impact of the remodeling processes, new biomarkers are needed to adequately treat patients with asthma and objectively monitor treatment response beyond symptom control and lung function.

Blood eosinophils associate with reduced lung function growth in adolescent asthmatics

Background and Objective

Some children with asthma have low lung growth, putting them at increased risk for COPD later in life. However, it is currently not clear who will experience this adverse growth pattern. We therefore investigated the predictive role of blood eosinophils as a type 2 inflammation marker in lung growth, focusing on the presence and severity of asthma.

Methods

We investigated blood eosinophils and lung function growth (percentage of predicted values) using linear mixed models in children and adolescents from two longitudinal cohorts. One cohort was hospital‐based and consisted of asthmatic children at their first outpatient clinic visit after referral by the general practitioner (n = 133, mean age 9.8), while the second was a general population‐based birth cohort (PIAMA, asthma n = 52 and non‐asthma n = 433, mean age 8.1). The hospital‐based cohort had not been treated with inhaled corticosteroids (ICS) before referral.

Results

Subjects in the hospital‐based asthma cohort had more severe asthma compared with the asthmatic subjects in the population‐based cohort, defined by lower lung function levels and a higher prevalence of bronchial hyper‐responsiveness. In the asthma cohort, higher blood eosinophil numbers were associated with less growth in FEV₁ (estimated change in lung function per 1 unit increase in ln blood eosinophils (B): −0.66%/year (95% confidence interval (CI): −1.11 to −0.20, p < .01)) and FVC (B: −0.40%/year (95% CI: −0.75 to −0.05), p = .025)) during follow‐up in adolescence (min 7, max 17 years). These associations were not observed in the general population‐based birth cohort, regardless of asthma status during follow‐up (age 8–16).

Conclusions and Clinical Relevance

Blood eosinophil counts in children with asthma not treated with ICS at referral were predictive of lower growth in FEV₁ and FVC during follow‐up in adolescence. Our findings indicate that this association is dependent on the degree of asthma severity. Future studies should address whether anti‐eosinophilic treatments preserve lung function growth in children with asthma.

Asthma: Pharmacological degradation of the airway smooth muscle layer

Asthma: A disease characterised by excessive and variable airway narrowing, and pathologies of inflammation and remodelling, particularly thickening of the airway smooth muscle (ASM). Treatment approaches dilate narrowed airways and reduce inflammation; however, remodelling seems largely neglected. This review considers the evolution of remodelling in asthma and whether conventional hypotheses that inflammation causes ASM thickening has mislead the medical community into thinking that anti-inflammatories will remedy this ASM defect. There is instead reasonable evidence that ASM thickening occurs independently of inflammation, such that therapies should employ strategies to directly modify ASM growth. Lessons have been learned from the use of untargeted bronchial thermoplasty and there should also be consideration of pharmacological therapies to ablate ASM. We discuss several new approaches to target ASM remodelling in asthma. A major current obstacle is our inability to image the ASM layer and assess treatment response. In this regard, polarisation-sensitive optical coherence tomography offers future promise.

Airway hyperresponsiveness, remodeling and inflammation in infants with wheeze

BACKGROUND

The relationship of airway hyperresponsiveness to airway remodeling and inflammation in infants with wheeze is unclear.

OBJECTIVE

To investigate airway hyperresponsiveness, remodeling and inflammation in infants with wheeze and troublesome breathing.

METHODS

Inclusion criteria were as follows: full-term, 3-23 months of age; doctor -diagnosed wheeze and persistent recurrent troublesome breathing; without obvious structural defect, suspicion of ciliary dyskinesia, cystic fibrosis, immune deficiency or specified use of corticosteroids. Airway hyperresponsiveness (AHR) was evaluated by performing a methacholine bronchial challenge test combined with whole body plethysmography and rapid thoracoabdominal compression. Endobronchial biopsies were analysed for remodeling (thickness of reticular basement membrane and amount of airway smooth muscle) and for inflammation (numbers of inflammatory cells). Correlation analyses were performed.

RESULTS

Forty-nine infants fulfilled the inclusion criteria for the present study. Median age was 1.06 years (IQR 0.6; 1.5). Lung function was impaired in 39/49 (80%) children, at the median age of 1.1 years. Methacholine challenge was successfully performed in 38/49 children. Impaired baseline lung function was correlated with AHR (P = .047, Spearman). In children with the most sensitive quartile of AHR, the percentage of median bronchial airway smooth muscle % and the number of bronchial mast cells in airway smooth muscle were not significantly higher compared to others (P = .057 and 0.056, respectively). No association was found between AHR and thickness of reticular basement membrane or inflammatory cells. Only a small group of children with both atopy and AHR (the most reactive quartile) had thicker airway smooth muscle area than non-atopics with AHR (P = .031).

CONCLUSIONS AND CLINICAL RELEVANCE

These findings do not support the concept that AHR in very young children with wheeze is determined by eosinophilic inflammation or clear-cut remodeling although it is associated with impaired baseline lung function. The possible association of increased airway smooth muscle area among atopic children with AHR remains to be confirmed.

Immunologic and Non-Immunologic Mechanisms Leading to Airway Remodeling in Asthma

Asthma increases worldwide without any definite reason and patient numbers double every 10 years. Drugs used for asthma therapy relax the muscles and reduce inflammation, but none of them inhibited airway wall remodeling in clinical studies. Airway wall remodeling can either be induced through pro-inflammatory cytokines released by immune cells, or direct binding of IgE to smooth muscle cells, or non-immunological stimuli. Increasing evidence suggests that airway wall remodeling is initiated early in life by epigenetic events that lead to cell type specific pathologies, and modulate the interaction between epithelial and sub-epithelial cells. Animal models are only available for remodeling in allergic asthma, but none for non-allergic asthma. In human asthma, the mechanisms leading to airway wall remodeling are not well understood. In order to improve the understanding of this asthma pathology, the definition of “remodeling” needs to be better specified as it summarizes a wide range of tissue structural changes. Second, it needs to be assessed if specific remodeling patterns occur in specific asthma pheno- or endo-types. Third, the interaction of the immune cells with tissue forming cells needs to be assessed in both directions; e.g., do immune cells always stimulate tissue cells or are inflamed tissue cells calling immune cells to the rescue? This review aims to provide an overview on immunologic and non-immunologic mechanisms controlling airway wall remodeling in asthma.

IL-33 in Chronic Respiratory Disease: From Preclinical to Clinical Studies

IL-33 has been deorphanized as a member of the IL-1 family and has key roles as an alarmin and cytokine with potent capacity to drive type 2 inflammation. This has led to a plethora of studies surrounding its role in chronic diseases with a type 2 inflammatory component. Here, we review the roles of IL-33 in two chronic respiratory diseases, asthma and chronic obstructive pulmonary disease (COPD). We discuss the hallmark and paradigm-shifting studies that have contributed to our understanding of IL-33 biology. We cover animal studies that have elucidated the mechanisms of IL-33 and assessed the role of anti-IL-33 treatment and immunization against IL-33. We highlight key clinical evidence for the potential of targeting increased IL-33 in respiratory diseases including exacerbations, and we outline current clinical trials using an anti-IL-33 monoclonal antibody in asthma patients. Finally, we discuss some of the challenges that have arisen in IL-33 biology and highlight potential future directions in targeting this cytokine in chronic respiratory diseases.

Early Airway Pathological Changes in Children: New Insights into the Natural History of Wheezing

Asthma is a heterogeneous condition characterized by reversible airflow limitation, with different phenotypes and clinical expressions. Although it is known that asthma is influenced by age, gender, genetic background, and environmental exposure, the natural history of the disease is still incompletely understood. Our current knowledge of the factors determining the evolution from wheezing in early childhood to persistent asthma later in life originates mainly from epidemiological studies. The underlying pathophysiological mechanisms are still poorly understood. The aim of this review is to converge epidemiological and pathological evidence early in the natural history of asthma to gain insight into the mechanisms of disease and their clinical expression.

Pleiotropic microRNA-21 in pulmonary remodeling: novel insights for molecular mechanism and present advancements

MicroRNA-21 (miR-21), probably one of the most studied miRNAs to date, is found pleiotropic in various biological events. Its emerging role in pulmonary remodeling has attracted extensive attention. This review summarizes the genomic information of its primary transcript and various transcriptional regulations on its promoter. In addition, the role of miR-21 in pulmonary remodeling related signaling such as transforming growth factor β (TGF-β), bone morphogenetic protein (BMP), epidermal growth factor receptor (EGFR) and Notch signaling is discussed. Various validated miR-21 target genes participate in controlling of the overactive cell accumulation, smooth muscle contraction, inflammatory stress (trigger for lung epithelium damage), extracellular matrix deposition and hypoxia-induced disorders. Moreover, we focus on its particular implication in events including inflammatory stress-driven epithelium damage, epithelial-to-mesenchymal transition (EMT), transdifferentiation of fibroblasts into myofibroblasts, hypoxia stimuli and ROS response, as well as some other pulmonary remodeling related events such as overactive fibroblast (myofibroblast) accumulation, extracellular matrix deposition, and angiogenesis. Here, we summarize the strong potential of miR-21 in pulmonary remodeling and provide novel clues for further research in this area.

Biomarkers for Recurrent Wheezing and Asthma in Preschool Children

Wheezing is one of the characteristic symptoms of asthma, but all preschool children with wheezing are not diagnosed with asthma. Preschool children are not cooperative enough to participate in spirometry and invasive tests. Thus, there is no conventional method to diagnose asthma in preschool children. We reviewed studies on non-invasive biomarkers for assessing asthma in preschool children. Specimens that can be easily obtained by non-invasive methods are blood, exhaled breath and urine. Eosinophils, eosinophil cationic protein and eosinophil-derived neurotoxin (EDN) in blood are helpful in evaluating eosinophilic inflammation of the airways. Exhaled breath contains nitric oxide, volatile organic compounds, various cytokines and mediators as analytical components. Fraction of exhaled nitric oxide has been used to assess the degree of eosinophil inflammation and has been standardized in school-age children and adults, but not yet in preschool children. Exhaled breath condensate (EBC) pH and various cytokines/mediators that are detected in EBC seem to be promising biomarkers for assessing asthma, but need more standardization and validation. There are several biomarkers useful for assessing asthma, but none are ideal. Some biomarkers need standardized methods of obtaining samples from uncooperative preschool children for clinical use and require sufficient validation. Recently, another activated eosinophil marker, serum EDN, has shown promising results as a biomarker for recurrent wheezing and asthma in preschool children.

Cytokines and Chemokines as Biomarkers of Future Asthma

Antenatal and preschool factors are key in determining the progression to pre-school wheeze and eosinophilic school age asthma. The conventional view of eosinophilic asthma is that airway inflammation is the fundamental underlying abnormality, and airway inflammation and hyper-responsiveness are secondary; in fact, these three are parallel processes. Very early structural changes, independent of inflammation and infection, are associated with early airway hyper-responsiveness and later adverse respiratory outcomes. There is a bidirectional relationship between structural airway wall changes and airway inflammation, with airway contraction per se leading to the release of growth factors, and inflammatory pathways promoting airway remodeling. Early viral infection (and increasingly being appreciated, bacterial infection) is important in wheeze outcomes. There is evidence of abnormal immune function including cytokine release before the onset of viral infections. However, viral infections may also have prolonged effects on the host immune system, and the evidence for beneficial and adverse effects of viral infection is conflicting. In older children and adults, asthmatic epithelial cells show impaired interferon responses to viral infection, but only in the presence of uncontrolled type 2 inflammation, implying these are secondary phenomena. There are also compelling data relating the innate immune system to later asthma and atopy, and animal studies suggest that the effects of a high endotoxin, microbiologically diverse environment may be modulated via the epithelial alarmin IL-33. Whereas, previously only viral infection was thought to be important, early bacterial colonization of the upper airway is coming to the fore, associated with a mixed pattern of TH1/TH2/TH17 cytokine secretion, and adverse long term outcomes. Bacterial colonization is probably a marker of a subtle immune deficiency, rather than directly causal. The airway and gut microbiome critically impacts the development of Type 2 inflammatory responses. However, Type 2 inflammatory cytokines, which are critical both to progression from pre-school wheeze to eosinophilic asthma, and sustaining the eosinophilic asthmatic state, are not implicated in the very early development of the disease. Taken together, the evidence is that the earliest cytokine and chemokine signals will come from the study of bronchial epithelial cell function and their interactions with viruses and the microbiome.

Pathophysiological Mechanisms of Asthma

The recent Lancet commission has highlighted that "asthma" should be used to describe a clinical syndrome of wheeze, breathlessness, chest tightness, and sometimes cough. The next step is to deconstruct the airway into components of fixed and variable airflow obstruction, inflammation, infection and altered cough reflex, setting the airway disease in the context of extra-pulmonary co-morbidities and social and environmental factors. The emphasis is always on delineating treatable traits, including variable airflow obstruction caused by airway smooth muscle constriction (treated with short- and long-acting β-2 agonists), eosinophilic airway inflammation (treated with inhaled corticosteroids) and chronic bacterial infection (treated with antibiotics with benefit if it is driving the disease). It is also important not to over-treat the untreatable, such as fixed airflow obstruction. These can all be determined using simple, non-invasive tests such as spirometry before and after acute administration of a bronchodilator (reversible airflow obstruction); peripheral blood eosinophil count, induced sputum, exhaled nitric oxide (airway eosinophilia); and sputum or cough swab culture (bacterial infection). Additionally, the pathophysiology of risk domains must be considered: these are risk of an asthma attack, risk of poor airway growth, and in pre-school children, risk of progression to eosinophilic school age asthma. Phenotyping the airway will allow more precise diagnosis and targeted treatment, but it is important to move to endotypes, especially in the era of increasing numbers of biologicals. Advances in -omics technology allow delineation of pathways, which will be particularly important in TH2 low eosinophilic asthma, and also pauci-inflammatory disease. It is very important to appreciate the difficulties of cluster analysis; a patient may have eosinophilic airway disease because of a steroid resistant endotype, because of non-adherence to basic treatment, and a surge in environmental allergen burden. Sophisticated -omics approaches will be reviewed in this manuscript, but currently they are not being used in clinical practice. However, even while they are being evaluated, management of the asthmas can and should be improved by considering the pathophysiologies of the different airway diseases lumped under that umbrella term, using simple, non-invasive tests which are readily available, and treating accordingly.

Airway remodeling disease: primary human structural cells and phenotypic and pathway assays to identify targets with potential to prevent or reverse remodeling

Airway remodeling is a characteristic of many chronic respiratory diseases and occurs when there are significant changes to the architecture of the small and large airways leading to progressive loss of lung function. Some common features include airway smooth muscle and goblet cell hyperplasia, basement membrane thickening and subepithelial fibrosis. To explore the mechanisms driving airway remodeling and identify novel targets to treat this aspect of respiratory disease, appropriate models must be used that will accurately predict the pathology of disease. Phenotypic assays can be used in primary human lung cells to measure changes in cell behavior that are associated with particular disease pathology. This is becoming increasingly popular when targeting chronic pathologies such as airway remodeling, where phenotypic assays are likely to model disease in vitro more accurately than traditional second messenger assays. Here we review the use of primary human lung structural cells in a range of disease-relevant chronic phenotypic assays, and how they may be used in target identification/validation and drug discovery.

Fibroblast gene expression following asthmatic bronchial epithelial cell conditioning correlates with epithelial donor lung function and exacerbation history

Airway remodeling may contribute to decreased lung function in asthmatic children. Bronchial epithelial cells (BECs) may regulate fibroblast expression of extracellular matrix (ECM) constituents and fibroblast-to-myofibroblast transition (FMT). Our objective was to determine if human lung fibroblast (HLF) expression of collagen I (COL1A1), hyaluronan synthase 2 (HAS2), and the FMT marker alpha-smooth muscle actin (α-SMA) by HLFs conditioned by BECs from asthmatic and healthy children correlate with lung function measures and exacerbation history among BEC donors. BECs from asthmatic (n = 23) and healthy children (n = 15) were differentiated at an air-liquid interface (ALI) and then co-cultured with HLFs for 96 hours. Expression of COL1A1, HAS2, and α-SMA by HLFs was determined by quantitative polymerase chain reaction (qPCR). FMT was quantified by measuring HLF cytoskeletal α-SMA by flow cytometry. Pro-collagen Iα1, hyaluronan (HA), and PGE₂ were measured in BEC-HLF supernatant. Correlations between lung function measures of BEC donors, and COL1A1, HAS2, and α-SMA gene expression, as well as supernatant concentrations of HA, pro-collagen Iα1, hyaluronan (HA), and PGE₂ were assessed. We observed that expression of α-SMA and COL1A1 by HLFs co-cultured with asthmatic BECs was negatively correlated with BEC donor lung function. BEC-HLF supernatant concentrations of pro-collagen Iα1 were negatively correlated, and PGE₂ concentrations positively correlated, with asthmatic BEC donor lung function. Expression of HAS2, but not α-SMA or COL1A1, was greater by HLFs co-cultured with asthmatic BECs from donors with a history of severe exacerbations than by HLFs co-cultured with BECs from donors who lacked a history of severe exacerbations. In conclusion, α-SMA and COL1A1 expression by HLFs co-cultured with BECs from asthmatic children were negatively correlated with lung function measures, supporting our hypothesis that epithelial regulation of HLFs and airway deposition of ECM constituents by HLFs contributes to lung function deficits among asthmatic children. Furthermore, epithelial regulation of airway HAS2 may influence the susceptibility of children with asthma to experience severe exacerbations. Finally, epithelial-derived PGE₂ is a potential regulator of airway FMT and HLF production of collagen I that should be investigated further in future studies.

Phosphodiesterase-4 Inhibitors for the Treatment of Inflammatory Diseases

Phosphodiesterase-4 (PDE4), mainly present in immune cells, epithelial cells, and brain cells, manifests as an intracellular non-receptor enzyme that modulates inflammation and epithelial integrity. Inhibition of PDE4 is predicted to have diverse effects via the elevation of the level of cyclic adenosine monophosphate (cAMP) and the subsequent regulation of a wide array of genes and proteins. It has been identified that PDE4 is a promising therapeutic target for the treatment of diverse pulmonary, dermatological, and severe neurological diseases. Over the past decades, numerous PDE4 inhibitors have been designed and synthesized, among which roflumilast, apremilast, and crisaborole were approved for the treatment of inflammatory airway diseases, psoriatic arthritis, and atopic dermatitis, respectively. It is regrettable that the dramatic efficacies of a drug are often accompanied by adverse effects, such as nausea, emesis, and gastrointestinal reactions. However, substantial advances have been made to mitigate the adverse effects and obtain better benefit-to-risk ratio. This review highlights the dialectical role of PDE4 in drug discovery and the disquisitive details of certain PDE4 inhibitors to provide an overview of the topics that still need to be addressed in the future.

Measuring Airway Obstruction in Severe Asthma in Children

Lung function is an important tool in the diagnosis and monitoring of patients with asthma at all ages. Airway obstruction is a typical feature of asthma and it can be assessed with several lung function techniques. Spirometry, respiratory resistance and reactance, and lung volumes are available to measure it at different ages and in children. The assessment of a bronchodilator response is always recommended to show the reversibility of the obstruction. Poor lung function is a predictor of poor asthma outcome and a low Forced Expiratory Volume in the first second of expiration percent predicted measured with spirometry, has been shown to be associated with a higher risk of having an exacerbation during the following year independently of the presence of asthma symptoms. In severe asthma lung function assessment is used to distinguish different phenotypes, children with severe asthma have worse airflow limitation prior to administration of a bronchodilator than children with non severe asthma. Airway resistance and reactance are indirect measurements of airway obstruction and they can be measured with the forced oscillation technique, which is feasible also in non-collaborative children. This technique can be more informative in discriminating patients with asthma from healthy controls and is able to indicate a more peripheral involvement of the airways. The role of this technique in severe asthma is still debated. In conclusion lung function is useful in the clinical management of children with severe asthma.