Immunohistology and remodeling in fatal pediatric and adolescent asthma

In utero exposure to experimental maternal asthma alters fetal airway development in sheep

The mechanisms linking maternal asthma (MA) exposure in utero and subsequent risk of asthma in childhood are not fully understood. Pathological airway remodelling, including reticular basement membrane thickening, has been reported in infants and children who go on to develop asthma later in childhood. This suggests altered airway development before birth as a mechanism underlying increased risk of asthma in children exposed in utero to MA. We hypothesised that in utero MA exposure would reduce airway diameter and increase airway-associated smooth muscle area and reticular basement membrane thickness in neonatal offspring. Experimental MA was induced by maternal sensitisation followed by airway challenges with house dust mite before and during pregnancy. Lambs from control (n = 16) or MA (n = 26) ewes were delivered at ∼140 days gestation (term = 150 days), ventilated for 45 min, then humanely killed. Left lungs were inflation-fixed, and cross-sections of generation 2-5 airways were collected. Airway sections were stained with Haematoxylin and Eosin, Masson's Trichrome and Gordon and Sweet's histological stains for morphological analysis. Lamb body and lung weights were similar between groups (P > 0.5 and P > 0.7, respectively). Lambs that were exposed to MA had narrower airway diameters (P = 0.019) and thinner reticular basement membrane (P = 0.016) but similar airway-associated smooth muscle area (P = 0.152) compared with unexposed control lambs. Our results demonstrate a potential mechanism for increased risk of asthma in children of mothers with asthma, independent of genetic risk or behavioural changes during pregnancy.

Interleukin-17 Genotypes in Egyptian Asthmatic Children at Zagazig University Hospitals

Bronchial asthma (BA) is increasing among Egyptian children. It is affected by multiple factors including genetic ones. In the current study, we assessed the relationship between interleukin-17 (IL-17) genotypes and the occurrence of BA among Egyptian children. This case-control study included 100 participants. Group I (the control group) comprised 50 healthy subjects. Group II (the asthmatic group) comprised 50 subjects diagnosed with atopic asthma according to the Global Initiative for Asthma. Measurement of serum Ig E and eosinophilic count was performed. Detection of single nucleotide polymorphism rs2275913 of IL-17 gene by restriction fragment length polymorphism-polymerase chain reaction was conducted. GA and AA genotypes were more frequent in the asthmatic group compared to the control group (P = 0.03 and 0.01, respectively). Subjects carrying GA and AA genotypes were more susceptible to have asthma [odds ratio (OR) = 2.21, 95% confidence interval (CI) = 1.14-9.94, P = 0.03; OR = 7.78, 95% CI = 1.59-38.3, P = 0.01, respectively]. The A allele was higher in the asthmatic group (33%) compared to the control group (10%). A allele carriers were more susceptible to have asthma (OR = 4.43, 95% CI = 2.04-9.82 and P < 0.001). Immunoglobulin E (IgE) levels and eosinophil percentages were higher among the carriers of GA and AA genotypes when compared with the GG genotype. All pulmonary function tests were significantly lower among carriers of AA genotype compared with GG genotype. An A allele carrier, AA genotype, increased IgE level, and eosinophil level were significant predictors for occurrence of asthma (P = 0.01, 0.02, 0.004, and 0.01). In conclusion, AA genotype carriers and A allele carriers of the IL-17 gene are more likely to have asthma compared with controls.

Current Approaches in the Multimodal Management of Asthma in Adolescents-From Pharmacology to Personalized Therapy

Asthma and adolescence are two sensitive points and are difficult to manage when they coexist. The first is a chronic respiratory condition, with frequent onset in early childhood (between 3 and 5 years), which can improve or worsen with age. Adolescence is the period between childhood and adulthood (12-19 years), marked by various internal and external conflicts and a limited capacity to understand and accept any aspect that is delimited by the pattern of the social circle (of the entourage) frequented by the individual. Therefore, the clinician is faced with multiple attempts regarding the management of asthma encountered during the adolescent period, starting from the individualization of the therapy to the control of compliance (which depends equally on the adverse reactions, quality of life offered and support of the close circle) and the social integration of the subject, communication probably having a more important role in the monitoring and evolution of the condition than the preference for a certain therapeutic scheme. Current statistics draw attention to the increase in morbidity and mortality among children with bronchial asthma, an aspect demonstrated by the numerous hospitalizations recorded, due either to an escalation in the severity of this pathology or to faulty management. The purpose of this article is to review the delicate aspects in terms of controlling symptoms and maintaining a high quality of life among teenagers.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

In vitro human cell-based models to study airway remodeling in asthma

Airway remodeling, as a predominant characteristic of asthma, refers to the structural changes that occurred both in the large and small airways. These pathological changes not only contribute to airway hyperresponsiveness and airway obstruction, but also predict poor outcomes of patients. In vitro models are the alternatives to animal models that facilitate airway remodeling research. Current approaches to mimic airway remodeling in vitro include mono cultures of cell lines and primary cells that are derived from the respiratory tract, and co-culture systems that consist of different cell subpopulations. Moreover, recent advances in microfluid chips and organoids show promise in simulating the complex architecture and functionality of native organs. According, they enable highly physiological-relevant investigations of human diseases in vitro. Here we aim to detail the current human cell-based models regarding their key pros and cons, and to discuss how they may be used to facilitate our understanding of airway remodeling in asthma.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

Research advances in airway remodeling in asthma: a narrative review

Background and Objective

Asthma is a common chronic disorder of the airway, and its disability and mortality rates continue to increase each year. Due to the lack of an ideal treatment, asthma control in China remains unsatisfactory. Airway remodeling is the pathological basis for the eventual development of the fixed airflow limitation in asthmatic patients. Early diagnosis and the prevention of airway remodeling has the potential to decrease disease severity, to improve control, and to prevent disease expression.

Methods

This article presents an overview. The literature was combed through via CNKi and PubMed according to the listed keywords. We considered Chinese and English original publications (basic science and clinical), reviews and abstracts of 21th Century.

Key Content and Findings

We review the pathological features and pathogenesis of, and the interventional treatment options for airway remodeling in asthmatic patients, emphasizing the importance of airway remodeling in asthma and providing novel insights into the prevention and control of asthma.

Conclusions

Thus, there have been research advances in airway remodeling, especially in the areas of slowing down or reversing airway remodeling. As growing studies showed, treating airway remodeling is a promising strategy in preventing the occurrence and progression of asthma. Breakthroughs in these difficulties airway remodeling still facing will open up new avenues in the research and treatment of asthma.

Peripheral airways involvement in children with asthma exacerbation

Objective

The literature provides some evidence of peripheral airways key role in the pathogenesis of asthma. However, the extent to which lung periphery including acinar zone contribute to asthma activity and control in pediatric population is unclear. Therefore, the aim of the study was to estimate peripheral airways involvement in children with asthma exacerbation and stable asthma simultaneously via different pulmonary function tests.

Methods

Children with asthma exacerbation (n = 20) and stable asthma (n = 22) performed spirometry, body plethysmography, exhaled nitric oxide, impulse oscillometry (IOS), and multiple‐breath washout (MBW).

Results

Peripheral airway's function indexes were increased in children with asthma, particularly in group with asthma exacerbation when compared with stable asthma group. The prevalence of abnormal results was significantly higher in asthma exacerbation. All children with asthma exacerbation had conductive ventilation inhomogeneity; 76% had acinar ventilation inhomogeneity. According to IOS measurements, resistance and reactance were within normal range, but other IOS parameters were significantly higher in children with asthma exacerbation compared with stable asthma group. The 36% of children with acute asthma had air trapping.

Conclusion

Significant involvement of peripheral airways was observed in children with asthma, particularly in asthma exacerbation, which determine lung periphery as important additional target for therapy and provide new insights into pathophysiological process of pediatric asthma.

E3 Ubiquitin Ligase March1 Facilitates OX40L Expression in Allergen-Stimulated Dendritic Cells Through Mediating the Ubiquitination of HDAC11

Background

It was demonstrated that membrane-associated RING-CH 1 (March 1) might play an important role in the pathogenesis of asthma.

Methods

The levels of mRNA and protein were measured by qRT-PCR and Western blot, respectively. Immunofluorescence assay was used to determine whether March1 co-locates with HDAC11. Co-immunoprecipitation was performed to examine the combination of proteins. Moreover, luciferase assay was used to measure the promoter activity of genes.

Results

The mRNA and protein levels of both March1 and OX40 ligand (OX40L) were increased in the dendritic cells (DCs) from asthmatic children and asthmatic animals. Histone deacetylase 11 (HDAC11) protein was decreased in the DCs from asthmatic children and asthmatic model. Increasing of March1 or decreasing of March1 only affect the expression of HDAC11 in protein level. Besides, increasing of HDAC11 could inhibit OX40L expression, and decreasing of HDAC11 promoted OX40L expression in house dust mites (HDMs)-treated DCs. Increasing of HDAC11 notably reversed the promotion of March1 to OX40L expression. Our data further proved that March1 reduced the protein level of HDAC11 through inducing ubiquitination and degradation. HDAC11 combined with krüppel-like factor 4 (KLF4) to decrease the activity of OX40L gene promoter, thus to downregulate the level of OX40L.

Conclusion

Overall, our data showed that HDAC11 promoted KLF4-dependent OX40L decreasing. However, March1 promoted OX40L expression through enhancing the ubiquitination and degradation of HDAC11 and subsequent blocking the inhibition of HDAC11 to OX40L.

Structure and function of small airways in asthma patients revisited

Small airways (<2 mm in diameter) are probably involved across almost all asthma severities and they show proportionally more structural and functional abnormalities with increasing asthma severity. The structural and functional alterations of the epithelium, extracellular matrix and airway smooth muscle in small airways of people with asthma have been described over many years using in vitro studies, animal models or imaging and modelling methods. The purpose of this review was to provide an overview of these observations and to outline several potential pathophysiological mechanisms regarding the role of small airways in asthma.

Blocking Notch3 Signaling Abolishes MUC5AC Production in Airway Epithelial Cells from Individuals with Asthma

In asthma, goblet cell numbers are increased within the airway epithelium, perpetuating the production of mucus that is more difficult to clear and results in airway mucus plugging. Notch1, Notch2, or Notch3, or a combination of these has been shown to influence the differentiation of airway epithelial cells. How the expression of specific Notch isoforms differs in fully differentiated adult asthmatic epithelium and whether Notch influences mucin production after differentiation is currently unknown. We aimed to quantify different Notch isoforms in the airway epithelium of individuals with severe asthma and to examine the impact of Notch signaling on mucin MUC5AC. Human lung sections and primary bronchial epithelial cells from individuals with and without asthma were used in this study. Primary bronchial epithelial cells were differentiated at the air-liquid interface for 28 days. Notch isoform expression was analyzed by Taqman quantitative PCR. Immunohistochemistry was used to localize and quantify Notch isoforms in human airway sections. Notch signaling was inhibited in vitro using dibenzazepine or Notch3-specific siRNA, followed by analysis of MUC5AC. NOTCH3 was highly expressed in asthmatic airway epithelium compared with nonasthmatic epithelium. Dibenzazepine significantly reduced MUC5AC production in air-liquid interface cultures of primary bronchial epithelial cells concomitantly with suppression of NOTCH3 intracellular domain protein. Specific knockdown using NOTCH3 siRNA recapitulated the dibenzazepine-induced reduction in MUC5AC. We demonstrate that NOTCH3 is a regulator of MUC5AC production. Increased NOTCH3 signaling in the asthmatic airway epithelium may therefore be an underlying driver of excess MUC5AC production.

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.

ZDHXB-101 (3',5-Diallyl-2, 4'-dihydroxy-[1,1'-biphen-yl]-3,5'-dicarbaldehyde) protects against airway remodeling and hyperresponsiveness via inhibiting both the activation of the mitogen-activated protein kinase and the signal transducer and activator of transcription-3 signaling pathways

Airway remodeling consists of the structural changes of airway walls, which is often considered the result of longstanding airway inflammation, but it may be present to an equivalent degree in the airways of children with asthma, raising the need for early and specific therapeutic interventions. The arachidonic acid cytochrome P-450 (CYP) pathway has thus far received relatively little attention in its relation to asthma. In this study, we studied the inhibition of soluble epoxide hydrolase (sEH) on airway remodeling and hyperresponsiveness (AHR) in a chronic asthmatic model which long-term exposure to antigen over a period of 12 weeks. The expression of sEH and CYP2J2, the level of 14, 15-epoxyeicosatrienoic acids (EETs), airway remodeling, hyperresponsiveness and inflammation were analyzed to determine the inhibition of sEH. The intragastric administration of 3 or 10 mg/kg ZDHXB-101, which is a structural derivative of natural product honokiol and a novel soluble epoxide hydrolase (sEH) inhibitor, daily for 9 weeks significantly increased the level of 14, 15-EETs by inhibiting the expression of sEH and increasing the expression of CYP2J2 in lung tissues. ZDHXB-101 reduced the expression of remodeling-related markers such as interleukin (IL)-13, IL-17, MMP-9 N-cadherin, α-smooth muscle actin, S100A4, Twist, goblet cell metaplasia, and collagen deposition in the lung tissue or in bronchoalveolar lavage fluid. Moreover, ZDHXB-101 alleviated AHR, which is an indicator that is used to evaluate the airway remodeling function. The inhibitory effects of ZDHXB-101 were demonstrated to be related to its direct inhibition of the extracellular signal-regulated kinase (Erk1/2) phosphorylation, as well as inhibition of c-Jun N-terminal kinases (JNK) and the signal transducer and activator of transcription-3 (STAT3) signal transduction. These findings first revealed the anti-remodeling potential of ZDHXB-101 lead in chronic airway disease.

Inhibition of soluble epoxide hydrolase attenuates airway remodeling in a chronic asthma model

Airway remodeling in asthma is difficult to treat because of its complex pathophysiology that involves proinflammatory cytokines, as well as the arachidonic acid cytochrome P-450 (CYP) pathway; however, it has received little attention. In this study, we assessed the efficacy of a soluble epoxide hydrolase (sEH) on airway remodeling in a mouse model of chronic asthma. The expression of sEH and CYP2J2 and the level of 14,15-epoxyeicosatrienoic acid (14,15-EET), airway remodeling and hyperresponsiveness (AHR) were analyzed to determine the level of sEH inhibition. AUDA, a sEH inhibitor, was given daily for 9 weeks orally, which significantly increased the level of 14,15-EET by inhibiting the expression of sEH and increasing the expression of CYP2J2 in lung tissues. The inhibition of sEH reduced the expression of remodeling-related molecular markers, such as interleukin (IL)-13, IL-17, matrix metalloproteinase 9, N-cadherin, α-smooth muscle actin (α-SMA), S100A4, Twist, epithelial goblet cell metaplasia, and collagen deposition in bronchoalveolar lavage fluid (BAL fluid) and lung tissues. Moreover, remodeling-related eosinophil accumulation in the BAL fluid and infiltration into the lung tissue were improved by AUDA. Finally, AUDA alleviated AHR, which is a functional indicator of airway remodeling. The effect of AUDA on airway remodeling was related to the downregulation of extracellular-regulated protein kinases (Erk1/2), c-Jun N-terminal kinases (JNK) and signal transducer and activator of transcription 3 (STAT3). To our knowledge, this is the first report to demonstrate that inhibition of sEH exerts significant protective effects on airway remodeling in asthma.

The anatomic substrate of irreversible airway obstruction and barotrauma in a case of hurricane-triggered fatal status asthmaticus during puerperium: Lessons from an autopsy

Non-fully reversible airway obstruction in fatal asthma is often seen in association with profound structural changes of the bronchial wall, termed airway remodeling. Evidence suggests that heavy precipitation events can trigger epidemics of severe asthma. We present a case of fatal asthma in a young woman with no prior near-fatal exacerbations and postulate that the patient's extensive airway remodeling and puerperal state (susceptibility factors), in combination with a massive allergen challenge during a hurricane landfall (triggering factor), played a central role in her death. The autopsy revealed diffuse obstruction of proximal and distal bronchi by mucous plugs together with transmural chronic inflammation, tissue eosinophilia, extensive goblet cell hyperplasia with MUC-5 expression and airway smooth muscle (ASM) thickening. The observed distribution of airway remodeling was heterogeneous with sparing of the lingula, which exhibited hyperinflation and expansion of perivascular spaces indicative of dissecting air. The massive stagnation of mucus and significant inter-airway structural heterogeneity created an anatomical substrate for unequal airflow distribution facilitating the development of barotrauma. Although not considered conventional risk factors for fatal asthma, we believe that in this case, the patient's puerperal state in conjunction with an extreme environmental event dispersing aeroallergens were major contributors to the development of a fatal asthma attack. Our autopsy findings suggest that effective strategies to evacuate stagnated mucus and induce relaxation of thickened ASM are crucial in the management of life-threatening asthma exacerbations.

Monocytes accumulate in the airways of children with fatal asthma

BACKGROUND

Activated T helper type 2 (Th2) cells are believed to play a pivotal role in allergic airway inflammation, but which cells attract and activate Th2 cells locally have not been fully determined. Recently, it was shown in an experimental human model of allergic rhinitis (AR) that activated monocytes rapidly accumulate in the nasal mucosa after local allergen challenge, where they promote recruitment of Th2 cells and eosinophils.

OBJECTIVE

To investigate whether monocytes are recruited to the lungs in paediatric asthma.

METHODS

Tissue samples obtained from children and adolescents with fatal asthma attack (n = 12), age-matched non-atopic controls (n = 9) and allergen-challenged AR patients (n = 8) were subjected to in situ immunostaining.

RESULTS

Monocytes, identified as CD68+S100A8/A9+ cells, were significantly increased in the lower airway mucosa and in the alveoli of fatal asthma patients compared with control individuals. Interestingly, cellular aggregates containing CD68+S100A8/A9+ monocytes obstructing the lumen of bronchioles were found in asthmatics (8 out of 12) but not in controls. Analysing tissue specimens from challenged AR patients, we confirmed that co-staining with CD68 and S100A8/A9 was a valid method to identify recently recruited monocytes. We also showed that the vast majority of accumulating monocytes both in the lungs and in the nasal mucosa expressed matrix metalloproteinase 10, suggesting that this protein may be involved in their migration within the tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

Monocytes accumulated in the lungs of children and adolescents with fatal asthma attack. This finding strongly suggests that monocytes are directly involved in the immunopathology of asthma and that these pro-inflammatory cells are potential targets for therapy.

Airways exudation of plasma macromolecules: Innate defense, epithelial regeneration, and asthma

This review discusses in vivo airway aspects of plasma exudation in relation to current views on epithelial permeability and epithelial regeneration in health and disease. Microvascular-epithelial exudation of bulk plasma proteins characteristically occurs in asthmatic patients, being especially pronounced in those with severe and exacerbating asthma. Healthy human and guinea pig airways challenged by noninjurious histamine-leukotriene–type autacoids also respond through prompt mucosal exudation of nonsieved plasma macromolecules. Contrary to current beliefs, epithelial permeability in the opposite direction (ie, absorption of inhaled molecules) has not been increased in patients with asthma and allergic rhinitis or in acutely exuding healthy airways. A slightly increased subepithelial hydrostatic pressure produces such unidirectional outward perviousness to macromolecules. Lack of increased absorption permeability in asthmatic patients can further be reconciled with occurrence of epithelial shedding, leaving small patches of denuded basement membrane. Counteracting escalating barrier breaks, plasma exudation promptly covers the denuded patches. Here it creates and sustains a biologically active barrier involving a neutrophil-rich, fibrin-fibronectin net. Furthermore, in the plasma-derived milieu, all epithelial cell types bordering the denuded patch dedifferentiate and migrate from all sides to cover the denuded basement membrane. However, this speedy epithelial regeneration can come at a cost. Guinea pig in vivo studies demonstrate that patches of epithelial denudation regeneration are exudation hot spots evoking asthma-like features, including recruitment/activation of granulocytes, proliferation of fibrocytes/smooth muscle cells, and basement membrane thickening. In conclusion, nonsieved plasma macromolecules can operate on the intact airway mucosa as potent components of first-line innate immunity responses. Exuded plasma also takes center stage in epithelial regeneration. When exaggerated, epithelial regeneration can contribute to the inception and development of asthma.

Airway remodeling in asthma: update on mechanisms and therapeutic approaches

PURPOSE OF REVIEW

The term 'airway remodeling' reflects changes in the type, quantity, and nature of airway wall components and their organization. The purpose of this review is to look at recent publications on airway remodeling in asthma.

RECENT FINDINGS

Animal models and in-vitro studies have confirmed the involvement of airway epithelium, airway smooth muscle (ASM), and extracellular matrix components in asthma-related airway remodeling. They report influences on proliferation of ASM cells, and how their orientation or morphology, in addition to the heterogeneity of ASM mass at different levels of airways could influence their effects. Clinical benefits have been observed following reduction of ASM following bronchial thermoplasty. Asthmatic epithelial cell transcriptome alterations were found to involve metabolism and epigenetics, beyond epithelial mesenchymal trophic unit driven by injury and repair in chronic inflammation. New ways to explore airway remodeling such as imaging or endoscopic techniques have been evaluated. Finally, new data support the role of eosinophils and mast cells in remodeling and show the influence of new asthma drugs on this process.

SUMMARY

As recently stated by an American Thoracic Society task force, we need more research on airway remodeling, its determinants and clinical relevance, and on the effects of asthma drugs on its various components.

Question 1: Why do children still die from asthma?

Asthma is one of the commonest chronic conditions in children and can occasionally be fatal. Little has changed regarding the risk factors for children dying from asthma in the last 30 years. The majority of deaths from asthma occur in children from socio-economically disadvantaged backgrounds. These should be preventable with better education of families, oversight of medication adherence and improved communication between health care professionals and families. More needs to be done to deliver basic messages more effectively about asthma management to the most vulnerable in communities around the world.

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

OBJECTIVES

We aimed to perform a systematic review of all studies with direct measurements of both airway inflammation and remodeling in the subgroup of children with repeated wheezing and/or persistent asthma severe enough to warrant bronchoscopy, to address whether airway inflammation precedes remodeling or is a parallel process, and also to assess the impact of remodeling on lung function.

METHODS

Four databases were searched up to June 2017. Two independent reviewers screened the literature and extracted relevant data.

RESULTS

We found 526 references, and 39 studies (2390 children under 18 years old) were included. Airway inflammation (eosinophilic/neutrophilic) and remodeling were not present in wheezers at a mean age of 12 months, but in older pre-school children (mean 2.5 years), remodeling (mainly increased reticular basement membrane [RBM] thickness and increased area of airway smooth muscle) and also airway eosinophilia was reported. This was worse in school-age children. RBM thickness was similar in atopic and non-atopic preschool wheezers. Airway remodeling was correlated with lung function in seven studies, with FeNO in three, and with HRCT-scan in one. Eosinophilic inflammation was not seen in patients without remodeling. There were no invasive longitudinal or intervention studies.

CONCLUSION

The relationship between inflammation and remodeling in children cannot be determined. Failure to demonstrate eosinophilic inflammation in the absence of remodeling is contrary to the hypothesis that inflammation causes these changes. We need reliable, non-invasive markers of remodeling in particular if this is to be addressed.