High-resolution computed tomography scan and airway remodeling in children with severe asthma

Machine learning-enhanced HRCT analysis for diagnosis and severity assessment in pediatric asthma

OBJECTIVES

Chest high-resolution computed tomography (HRCT) is conditionally recommended to rule out conditions that mimic or coexist with severe asthma in children. However, it may provide valuable insights into identifying structural airway changes in pediatric patients. This study aims to develop a machine learning-based chest HRCT image analysis model to aid pediatric pulmonologists in identifying features of severe asthma.

METHODS

This retrospective case-control study compared children with severe asthma (as defined by ERS/ATS guidelines) to age- and sex-matched controls without asthma, using chest HRCT scans for detailed imaging analysis. Statistical analysis included classification trees, random forests, and conventional ROC analysis to identify the most significant imaging features that mark severe asthma from controls.

RESULTS

Chest HRCT scans differentiated children with severe asthma from controls. Compared to controls (n = 21, mean age 11.4 years), children with severe asthma (n = 20, mean age 10.4 years) showed significantly greater bronchial thickening (BT) scores (p < 0.001), airway wall thickness percentage (AWT%, p < 0.001), bronchiectasis grading (BG) and bronchiectasis severity (BS) scores (p = 0.016), mucus plugging, and centrilobular emphysema (p = 0.009). Using AWT% as the predictor in conventional ROC analysis, an AWT% ≥ 38.6 emerged as the optimal classifier for discriminating severe asthmatics from controls, with 95% sensitivity, specificity, and overall accuracy.

CONCLUSION

Our study demonstrates the potential of machine learning-based analysis of chest HRCT scans to accurately identify features associated with severe asthma in children, enhancing diagnostic evaluation and contributing to the development of more targeted treatment approaches.

Children with severe asthma have substantial structural airway changes on computed tomography

Background

In adults with severe asthma (SA) bronchial wall thickening, bronchiectasis and low attenuation regions (LAR) have been described on chest computed tomography (CT) scans. The extent to which these structural abnormalities are present in children with SA is largely unknown. Our aim was to study the presence and extent of airway abnormalities on chest CT of children with SA.

Methods

161 inspiratory and expiratory CT scans, either spirometer-controlled or technician-controlled, obtained in 131 children with SA (mean±SD age 11.0±3.8 years) were collected retrospectively. Inspiratory scans were analysed manually using a semi-quantitative score and automatically using LungQ (v2.1.0.1; Thirona B.V., Nijmegen, the Netherlands). LungQ segments the bronchial tree, identifies the generation for each bronchus-artery (BA) pair and measures the following BA dimensions: outer bronchial wall diameter (Bout), adjacent artery diameter (A) and bronchial wall thickness (Bwt). Bronchiectasis was defined as Bout/A ≥1.1, bronchial wall thickening as Bwt/A ≥0.14. LAR, reflecting small airways disease (SAD), was measured automatically on inspiratory and expiratory scans and manually on expiratory scans. Functional SAD was defined as FEF25-75 and/or FEF75 z-scores <-1.645. Results are shown as median and interquartile range.

Results

Bronchiectasis was present on 95.8% and bronchial wall thickening on all CTs using the automated method. Bronchiectasis was present on 28% and bronchial wall thickening on 88.8% of the CTs using the manual semi-quantitative analysis. The percentage of BA pairs defined as bronchiectasis was 24.62% (12.7-39.3%) and bronchial wall thickening was 41.7% (24.0-79.8%) per CT using the automated method. LAR was observed on all CTs using the automatic analysis and on 82.9% using the manual semi-quantitative analysis. Patients with LAR or functional SAD had more thickened bronchi than patients without.

Conclusion

Despite a large discrepancy between the automated and the manual semi-quantitative analysis, bronchiectasis and bronchial wall thickening are present on most CT scans of children with SA. SAD is related to bronchial wall thickening.

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.

Significance of alveolar nitric oxide concentration in the airway of patients with organizing pneumonia after allogeneic hematopoietic stem cell transplantation

Organizing pneumonia (OP) is a complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and a manifestation of peripheral airway/alveolar inflammation. Recently, alveolar nitric oxide concentration (Calv) has been revealed as a noninvasive marker of peripheral airway inflammation; however, whether Calv levels are associated with OP and peripheral airway in patients after allo-HSCT remains unclear. Herein, we evaluated whether Calv levels could reflect the presence of OP and structural airway changes in patients after allo-HSCT. We measured the eNO levels of 38 patients (6 with OP and 32 without OP) who underwent allo-HSCT. Three-dimensional computed tomography (CT) analysis of the airway was performed in 19 patients. We found that in patients with OP, Calv levels were significantly higher than in those without OP (10.6 vs. 5.5 ppb, p < 0.01). Receiver-operating characteristic analyses revealed a Calv cut-off value for OP detection of 10.2 ppb. No significant differences in the patient characteristics, except for the presence of OP (p < 0.01), were noted between the two groups stratified by the Calv cut-off value. Three-dimensional CT images of the airway revealed gradually increasing positive correlations between Calv levels and airway wall area of the third-, fourth-, and fifth-generation bronchi (r = 0.20, 0.31, 0.38; p = 0.42, 0.19, 0.038, respectively), indicating that Calv levels are strongly correlated with the wall thickness of the distal bronchi. Our results suggest that the Calv level may be a useful noninvasive detectable marker for OP after an allo-HSCT.

[Lung imaging in severe asthma]

INTRODUCTION

Asthma is a common disease whose diagnosis does not typically rely on the results of imaging. However, chest CT has gained a key place over the last decade to support the management of patients with difficult to treat and severe asthma.

STATE OF THE ART

Bronchial wall thickening and mild dilatation or narrowing of bronchial lumen are frequently observed on chest CT in people with asthma. Bronchial wall thickening is correlated to the degree of obstruction and to bronchial wall remodeling and inflammation. Diverse conditions which can mimic asthma should be recognized on CT, including endobronchial tumours, interstitial pneumonias, bronchiectasis and bronchiolitis. Ground-glass opacities and consolidation may be related to transient eosinophilic infiltrates, infection or an associated disease (vasculitis, chronic eosinophilic pneumonia). Hyperdense mucous plugging is highly specific for allergic bronchopulmonary aspergillosis.

PERSPECTIVES

Airway morphometry, air trapping and quantitative analysis of ventilatory defects, with CT or MRI, can help to identify different morphological subgroups of patients with different functional or inflammatory characteristics. These imaging tools could emerge as new biomarkers for the evaluation of treatment response.

CONCLUSION

Chest CT is indicated in people with severe asthma to search for additional or alternative diagnoses. Quantitative imaging may contribute to phenotyping this patient group.

High-resolution CT pulmonary findings in children with severe asthma

OBJECTIVE

To compare quantitative CT parameters between children with severe asthma and healthy subjects, correlating to their clinical features.

METHODS

We retrospectively analyzed CT data from 19 school-aged children (5-17 years) with severe asthma and 19 control school-aged children with pectus excavatum. The following CT parameters were evaluated: total lung volume (TLV), mean lung density (MLD), CT air trapping index (AT%) (attenuation ≤856 HU), airway wall thickness (AWT), and percentage of airway wall thickness (AWT%). Multi-detector computed tomography (MDCT) data were correlated to the following clinical parameters: forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flow at 25-75% (FEF 25-75%), FEV1/FVC ratio, sputum and bronchoalveolar lavage analysis, serum IgE levels, and previous hospitalizations due to asthma.

RESULTS

Asthma patients presented higher mean values of AT% (23.8 ± 6.7% vs. controls, 9.7 ± 3.2%), AWT (1.46 ± 0.22 mm vs. controls, 0.47 ± -735 ± 28 HU vs. controls, -666 ± 19 HU). Mean AT% was 29.0 ± 4.7% in subjects with previous hospitalization against 19.2 ± 5.0% in those with no prior hospitalization (p < 0.001). AT% presented very strong negative correlations with FVC (r = -0.933, p < 0.001) and FEV1 (r = -0.841, p < 0.001) and a moderate correlation with FEF 25-75% (r = -0.608, p = 0.007). AT% correlation with FEV1/FVC ratio and serum IgE was weak (r = -0.184, p = 0.452, and r = -0.363, p = 0.202) CONCLUSION: Children with severe asthma present differences in quantitative chest CT scans compared to healthy controls with strong correlations with pulmonary function tests and previous hospitalizations due to asthma.

Status and prospects: personalized treatment and biomarker for airway remodeling in asthma

Airway remodeling, as a major characteristic of bronchial asthma, is critical to the progression of this disease, whereas it is of less importance in clinical management. Complying with the current stepwise treatment standard for asthma, the choice of intervention on the clinical status is primarily determined by the patient’s treatment response to airway inflammation. However, a considerable number of asthmatic patients, especially severe asthmatic subjects, remain uncontrolled though they have undergone fortified anti-inflammation treatment. In the past few years, a growing number of biologics specific to asthma phenotypes have emerged, bringing new hope for patients with refractory asthma and severe asthma. While at the same time, the effect of airway remodeling on asthma treatment has become progressively prominent. In the era of personalized treatment, it has become one of the development directions for asthma treatment to find reliable airway remodeling biomarkers to assist in asthma phenotypes classification, and to further combine multiple phenotypes to accurately treat patients. In the present study, the research status of airway remodeling in asthma is reviewed to show the basis for classifying and treating such disease. Besides, several selected airway remodeling biomarkers and possibility to use them in individual treatment are discussed as well. This study considers that continuously optimized mechanisms and emerging biomarkers for airway remodeling in the future may further support individual therapy for asthma patients.

Wearable Vital Signs Monitoring for Patients With Asthma: A Review

Worldwide,an estimated 461 000 people die from asthma attacks each year. While there remain treatments to alleviate asthma symptoms and reduce deaths, patient deterioration needs to be identified in sufficient time. To prevent asthma deterioration, patients need to be aware of personal and environmental triggers and monitor their asthma symptoms. The aim of this article is to provide a comprehensive review of the current state-of-the-art wearable sensors and devices that use vital signs for asthma patient monitoring and management. Among all vital signs, breathing rate and airflow sound are key indicators of asthmatic patients' health that can be measured directly using wearable sensors to provide continuous and constant patient monitoring or indirectly by estimations based on proven algorithms using electrocardiogram (ECG), photoplethysmogram (PPG), and chest movements. ECG and PPG signals are widely used in smart watches and chest bands, enabling easy integration of a more extensive body sensor framework for asthmatic exacerbation prediction. Other vital signs used in asthma patient monitoring include blood oxygen saturation, temperature, blood pressure, verbal sound, and pain responses. The use of wearable vital signs enabled a broad range of wearable sensor application scenarios for asthma monitoring and management.

High prevalence of bronchiectasis on chest CT in a selected cohort of children with severe Asthma

Background

Chest computed tomography (CT) scans have a recognised role in investigating adults with severe asthma to exclude alternative diagnoses, but its role in children is less clear. The objective of this study was to review the CT findings of our local cohort of children with severe asthma and to explore whether clinical or pathobiological parameters predicted CT changes.

Methods

Retrospective observational single centre study including all children attending the Leicester difficult asthma clinic (DAC) who underwent a chest CT from 2006 to 2011. Additionally, we recruited eight age-matched, non-asthmatic controls to compare differences in CT findings between asthmatic and non-asthmatic children. All CT images were independently scored by two radiologists.

The DAC patients were sub-divided into binary groups for each abnormality identified so that comparisons could be made against recorded clinical variables including age, lung function, serum total IgE levels, and sputum leukocyte differential cell counts.

Results

Thirty DAC patients (median 12 yrs., range 5–16) were included.

The most common abnormalities were bronchial wall thickening (BWT) and air trapping (AT), observed in 80 and 60% of DAC patients.

Bronchiectasis (BE) was identified in 27% of DAC patients. DAC patients with evidence of BE on CT images were older than those without BE (13.9 ± 0.67 vs 11.5 ± 0.61, p = 0.038). We also identified a positive correlation between increasing BE severity and extent with age (r = 0.400, p = 0.028).

Conclusion

Abnormal CT findings were highly prevalent in our cohort of children with severe asthma, with bronchiectasis identified in approximately one third of children. We found no alternative diagnoses that resulted in a change in clinical management.

Clinical features of three-dimensional computed tomography-based radiologic phenotypes of chronic obstructive pulmonary disease

Purpose

The diagnosis and severity of chronic obstructive pulmonary disease (COPD) are defined by airflow limitation using spirometry. However, COPD has diverse clinical features, and several phenotypes based on non-spirometric data have been investigated. To identify novel phenotypes of COPD using radiologic data obtained by three-dimensional computed tomography (3D-CT).

Patients and methods

The inner luminal area and wall thickness of third- to sixth-generation bronchi and the percentage of the low-attenuation area (less than −950 HU) of the lungs were measured using 3D-CT in patients with COPD. Using the radiologic data, hierarchical clustering was performed. Respiratory reactance and resistance were measured to evaluate functional differences among the clusters.

Results

Four clusters were identified among 167 patients with COPD: Cluster I, mild emphysema with severe airway changes, severe airflow limitation, and high exacerbation risk; Cluster II, mild emphysema with moderate airway changes, mild airflow limitation, and mild dyspnea; Cluster III, severe emphysema with moderate airway changes, severe airflow limitation, and increased dyspnea; and Cluster IV, moderate emphysema with mild airway changes, mild airflow limitation, low exacerbation risk, and mild dyspnea. Cluster I had the highest respiratory resistance among the four clusters. Clusters I and III had higher respiratory reactance than Clusters II and IV.

Conclusions

The 3D-CT-based radiologic phenotypes were associated with the clinical features of COPD. Measurement of respiratory resistance and reactance may help to identify phenotypic differences.

Paediatric and adult bronchiectasis: Specific management with coexisting asthma, COPD, rheumatological disease and inflammatory bowel disease

Bronchiectasis, conventionally defined as irreversible dilatation of the bronchial tree, is generally suspected on a clinical basis and confirmed by means of chest high-resolution computed tomography. Clinical manifestations, including chronic productive cough and endobronchial suppuration with persistent chest infection and inflammation, may deeply affect quality of life, both in children/adolescents and adults. Despite many cases being idiopathic or post-infectious, a number of specific aetiologies have been traditionally associated with bronchiectasis, such as cystic fibrosis (CF), primary ciliary dyskinesia or immunodeficiencies. Nevertheless, bronchiectasis may also develop in patients with bronchial asthma; chronic obstructive pulmonary disease; and, less commonly, rheumatological disorders and inflammatory bowel diseases. Available literature on the development of bronchiectasis in these conditions and on its management is limited, particularly in children. However, bronchiectasis may complicate the clinical course of the underlying condition at any age, and appropriate management requires an integration of multiple skills in a team of complementary experts to provide the most appropriate care to affected children and adolescents. The present review aims at summarizing the current knowledge and available evidence on the management of bronchiectasis in the other conditions mentioned and focuses on the new therapeutic strategies that are emerging as promising tools for improving patients' quality of life.

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.

Respiratory impedance is correlated with airway narrowing in asthma using three-dimensional computed tomography

BACKGROUND

Respiratory impedance comprises the resistance and reactance of the respiratory system and can provide detailed information on respiratory function. However, details of the relationship between impedance and morphological airway changes in asthma are unknown.

OBJECTIVE

We aimed to evaluate the correlation between imaging-based airway changes and respiratory impedance in patients with asthma.

METHODS

Respiratory impedance and spirometric data were evaluated in 72 patients with asthma and 29 reference subjects. We measured the intraluminal area (Ai) and wall thickness (WT) of third- to sixth-generation bronchi using three-dimensional computed tomographic analyses, and values were adjusted by body surface area (BSA, Ai/BSA, and WT/the square root (√) of BSA).

RESULTS

Asthma patients had significantly increased respiratory impedance, decreased Ai/BSA, and increased WT/√BSA, as was the case in those without airflow limitation as assessed by spirometry. Ai/BSA was inversely correlated with respiratory resistance at 5 Hz (R5) and 20 Hz (R20). R20 had a stronger correlation with Ai/BSA than did R5. Ai/BSA was positively correlated with forced expiratory volume in 1 second/forced vital capacity ratio, percentage predicted forced expiratory volume in 1 second, and percentage predicted mid-expiratory flow. WT/√BSA had no significant correlation with spirometry or respiratory impedance.

CONCLUSIONS & CLINICAL RELEVANCE

Respiratory resistance is associated with airway narrowing.

Relationship between fraction of exhaled nitric oxide and airway morphology assessed by three-dimensional CT analysis in asthma

Fraction of exhaled nitric oxide (FeNO) provides information about chronic inflammation in asthma. However, its relationship with structural changes in the airways is unknown. We aimed to evaluate the correlation between computer-based airway changes and FeNO in patients with asthma. The wall area (WA) and airway inner luminal area (Ai) of the third- to sixth-generation bronchi were measured using three-dimensional computed tomography in asthmatic patients. Each value was corrected by body surface area (BSA). Relationships between FeNO and WA/BSA and Ai/BSA were evaluated. Forty-one clinically stable patients with asthma were evaluated. FeNO was significantly correlated with WA/BSA of the third-, fourth-, fifth- and sixth-generation bronchi (Spearman correlation coefficient (ρ) = 0.326, p = 0.041; ρ = 0.356, p = 0.025; ρ = 0.496, p = 0.002; and ρ = 0.529, p < 0.001, respectively). The correlation with sixth-generation bronchi was significantly greater than with the third-generation bronchi (p = 0.047). Partial rank correlation analysis indicated FeNO was significantly correlated with WA/BSA of the sixth-generation bronchi, independent from confounding factors of Ai/BSA, age, duration of asthma, dose of inhaled corticosteroid, blood eosinophil percentage, and blood IgE (ρ = 0.360, p = 0.034). In contrast, there was no correlation between FeNO and Ai/BSA. FeNO correlates with bronchial wall thickening in asthma patients. Measurement of FeNO may be useful to detect airway remodeling in asthma.

Intraepithelial neutrophils in pediatric severe asthma are associated with better lung function

BACKGROUND

Neutrophils and IL-17A have been linked mechanistically in models of allergic airways disease and have been associated with asthma severity. However, their role in pediatric asthma is unknown.

OBJECTIVES

We sought to investigate the role of neutrophils and the IL-17A pathway in mediating pediatric severe therapy-resistant asthma (STRA).

METHODS

Children with STRA (n = 51; age, 12.6 years; range, 6-16.3 years) and controls without asthma (n = 15; age, 4.75 years; range, 1.6-16 years) underwent clinically indicated fiberoptic bronchoscopy, bronchoalveolar lavage (BAL), endobronchial brushings, and biopsy. Neutrophils, IL-17A, and IL-17RA-expressing cells and levels of IL-17A and IL-22 were quantified in BAL and biopsies and related to clinical features. Primary bronchial epithelial cells were stimulated with IL-17A and/or IL-22, with and without budesonide.

RESULTS

Children with STRA had increased intraepithelial neutrophils, which positively correlated with FEV1 %predicted (r = 0.43; P = .008). Neutrophilhigh patients also had better symptom control, despite lower dose maintenance inhaled steroids. Submucosal neutrophils were not increased in children with STRA. Submucosal and epithelial IL-17A-positive cells and BAL IL-17A and IL-22 levels were similar in children with STRA and controls. However, there were significantly more IL-17RA-positive cells in the submucosa and epithelium in children with STRA compared with controls (P = .001). Stimulation of primary bronchial epithelial cells with IL-17A enhanced mRNA expression of IL-17RA and increased release of IL-8, even in the presence of budesonide.

CONCLUSIONS

A proportion of children with STRA exhibit increased intraepithelial airway neutrophilia that correlated with better lung function. STRA was also characterized by increased airway IL-17RA expression. These data suggest a potential beneficial rather than adverse role for neutrophils in pediatric severe asthma pathophysiology.

Predicting asthma morbidity in children using proposed markers of Th2-type inflammation

BACKGROUND

Assessment of inflammation is becoming a common practice in the clinical work-up of children with persistent asthma. Biomarkers of Th2-mediated inflammation include blood eosinophils (B-Eos), exhaled nitric oxide (FeNO), total serum IgE (S-IgE), and serum periostin. The aim of this study was to investigate the associations between asthma morbidity and increased levels of these biomarkers in pediatric asthma.

METHODS

School-age children (n = 96) with various manifestations of persistent asthma were included in this nationwide Swedish study. The protocol included the asthma control test, Juniper's quality of life questionnaire (QoL), assessment of pulmonary function, bronchial hyperresponsiveness, height-adjusted FeNO, blood sampling for S-IgE, B-Eos, and periostin, and high-resolution computed tomography (HRCT) of the lungs.

RESULTS

Children with both high levels of height-adjusted FeNO and B-Eos were younger (p = 0.001), had more often severe asthma (p = 0.015), were more allergic (p < 0.001), had a reduced asthma control (p = 0.035), reduced QoL (p = 0.035), more exacerbations (p = 0.004), reduced FEV1/FVC (p = 0.001), and increased bronchial hyperresponsiveness (p < 0.001) as well as greater bronchial wall thickening on HRCT (p = 0.022) compared to those with low levels of both biomarkers. Grouping children according to high and low serum periostin levels did not relate to differences in clinical characteristics and biomarkers.

CONCLUSIONS

Assessment of both local and systemic Th2-mediated inflammation by the analysis of easily attainable biomarkers such as exhaled NO and blood eosinophils has a high predictive value for the identification of children with the highest asthma morbidity. Adjusting FeNO values according to the individual child's height increases the clinical usefulness of this biomarker.

Update on the current methods for the diagnosis and treatment of severe childhood asthma

The level of asthma control is the key outcome towards which asthma management is evaluated. The majority of children with asthma can obtain adequate control of symptoms through avoidance of triggering factors and/or with the help of low to moderate doses of current available medications. However, there is still a group of children with poor symptom control despite intensive treatment. The current review will provide an overview of a standardized approach to characterize this heterogeneous group of severely sick children. Factors that attenuate the effect of the prescribed treatment and make asthma difficult to treat are discussed. In addition, the usefulness of current methods of assessing asthma severity, pulmonary function, allergy and airway inflammation is also described. Finally, an overview of therapeutic options for children with severe asthma is provided.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Assessment of Small Airways with Computed Tomography: Mosaic Attenuation or Lung Density?

BACKGROUND

Computed tomography (CT) assessment of air trapping has been considered useful as a measure of small airway disease. Mean lung density (MLD) and the percentage of the lung field occupied by low attenuation area (LAA%) can be evaluated automatically, and their expiratory/inspiratory (E/I) ratios correlate with asthma severity and spirometry parameters. However, mosaic attenuation, another indicator of air trapping, has been assessed visually, and its functional relevance remains controversial.

OBJECTIVES

This retrospective study was conducted to correlate mosaic attenuation, which was assessed visually and automatically, and the E/I ratios of MLD and LAA% (defined as areas <-960 Hounsfield units) with clinical and physiological variables, including impulse oscillometry (IOS) indices.

MATERIAL AND METHODS

In 36 nonsmoking patients with stable asthma, the lungs were scanned at full inspiration and full expiration. Mosaic attenuation was measured visually and automatically, by counting areas with CT values higher than the surrounding areas. MLD and LAA% were measured using our validated method. Spirometry, IOS, exhaled NO and the sputum eosinophil count were evaluated.

RESULTS

The automatic results and visual scores of mosaic attenuation correlated well on expiratory scans (r = 0.894) and to a lesser degree on inspiratory scans (r = 0.629; p < 0.0001 for both). However, only the E/I ratios of MLD and LAA% correlated with forced expiratory volume in 1 s/forced vital capacity of spirometry and the IOS indices of resistance from 5 to 20 Hz and the integrated area of low-frequency reactance.

CONCLUSIONS

Our automatic method for analysis of mosaic attenuation is likely useful, but the results themselves may not be reflecting small airway involvement of asthma, unlike the E/I ratios of MLD and LAA%.

Distribution of airway smooth muscle remodelling in asthma: relation to airway inflammation

BACKGROUND AND OBJECTIVE

Pathological phenotypes of asthma have been based predominantly on inflammation, rather than airway wall remodelling. Differences in the distribution of airway smooth muscle (ASM) remodelling between large and small airways may affect clinical outcomes in asthma. The aim of this study was to examine the distribution of ASM remodelling and its relation to airway inflammation.

METHODS

Post-mortem cases of asthma (n = 68) were categorized by the distribution of increased thickness of the ASM layer (relative to nonasthmatic controls, n = 37), into 'large only' (LO, n = 15), 'small only' (SO, n = 4) 'large/small' (LS, n = 24) or no increase (NI, n = 25). Subject characteristics, ASM and airway wall dimensions and inflammatory cell numbers were compared between groups.

RESULTS

Apart from reduced clinical severity of asthma in NI cases (P = 0.002), subject characteristics did not distinguish asthma groups. Compared with control subjects, ASM cell number, reticular basement membrane thickness, airway wall thickness, percent muscle shortening and eosinophil number were increased (P < 0.05) in both large and small airways in LS cases and only the large airways in LO cases. Increased numbers of neutrophils were observed only in the small airways of LO cases.

CONCLUSIONS

Distinct distributions of ASM remodelling are seen in asthma. Pathology limited to the small airways was uncommon. Increased thickness of the ASM layer was associated with airway remodelling and eosinophilia, but not neutrophilia. These data support the presence of distinct pathological phenotypes based on the site of increased ASM.

[Targeted therapies in severe asthma: the discovery of new molecules]

The pathophysiological mechanisms involved in the chronicity and phenotypic heterogeneity of asthma offer the prospect of new therapeutic opportunities. A better clinical and biological characterisation of selected patients has led to the development of targeted therapies. Studies are under way to demonstrate their efficacy and tolerance and also their impact on the natural history of the disease. This revue aims to examine the therapies, developed during the last ten years, that are based on the immunological mechanisms involved in the pathophysiology of asthma, essentially in its severe form. The rapid expansion of human monoclonal antibodies has allowed testing of various immunological pathways. Anti-IgE, anti- IL-5, and anti-IL-13 strategies seem the most promising. Antagonists to TNF-alpha and I'IL-4 have not succeeded in reducing the events related to severe asthma in a convincing manner. Molecules targeted against thymic stromal lymphopoietin (TSLP) and I'IL-9 are under development. These approaches are involved in the development of therapeutic programmes adapted to the patient's phenotype, that is to say a personalised approach to care.

The chitinase-like protein YKL-40: a possible biomarker of inflammation and airway remodeling in severe pediatric asthma

BACKGROUND

Problematic severe childhood asthma includes a subgroup of patients who are resistant to therapy. The specific mechanisms involved are unknown, and novel biomarkers are required to facilitate treatment and diagnosis of therapy-resistant asthma. The chitinase-like protein YKL-40 has been related to asthma and airway remodeling.

OBJECTIVES

To compare serum YKL-40 levels in children with severe, therapy-resistant asthma (n = 34), children with controlled persistent asthma (n = 39), and healthy controls (n = 27), and to investigate correlations with biomarkers of inflammation and airway remodeling.

METHODS

The study protocol included questionnaires, measurement of exhaled nitric oxide in exhaled air, blood sampling for inflammatory biomarkers, and high-resolution computed tomography of the lungs to identify bronchial wall thickening (therapy-resistant only). Serum YKL-40 levels were measured by ELISA, and all asthmatic children were genotyped for a CHI3L1 promoter single nucleotide polymorphism (rs4950928).

RESULTS

Serum YKL-40 levels were significantly higher in children with therapy-resistant asthma than in healthy children (19.2 ng/mL vs 13.8 ng/mL, P = .03). Among children with severe, therapy-resistant asthma, YKL-40 levels correlated with fraction of exhaled nitric oxide in exhaled air (r = 0.48, P = .004), blood neutrophils (r = 0.63, P < .001), and bronchial wall thickening on high-resolution computed tomography (r = 0.45, P = .01). Following adjustment for CHI3L1 genotype, significantly greater levels of YKL-40 were found in children with therapy-resistant asthma than in children with controlled asthma.

CONCLUSIONS

YKL-40 levels are increased in children with severe, therapy-resistant asthma compared to healthy children, and also compared to children with controlled asthma following correction for genotype.

Imaging advances in asthma

INTRODUCTION

Asthma is a global burden, affecting 5% of the general adult population, with approximately 5 - 10% suffering from severe asthma. Severe asthma is a complex heterogeneous disease entity, with high morbidity and mortality. Recent years have seen the introduction of a vast array of new imaging technologies, which have provided the ability to comprehensively, non-invasively and functionally assess the lungs. These advances have resulted in a better understanding of the pathophysiology in severe asthma and have the unprecedented potential to unravel the structure-function relationship of severe asthma in the future.

AREAS COVERED

This review article chronologically describes the technological advances currently used and to be used in the future. The article covers pitfalls in imaging of the airways and lung parenchyma in asthma from chest x-rays, CT scans, MRI, confocal florescence endomicroscopy to computational fluid dynamics.

EXPERT OPINION

Novel qualitative and quantitative imaging techniques have enabled us to study the large airway architecture in detail, assess the small airway structure and perform functional or novel physiological evaluations. Despite spectacular advances in imaging techniques and the birth of new modalities, there is an urgent need for both proof-of-concept studies, large cross-sectional and longitudinal clinical trials in severe asthma to validate and clinically correlate imaging-derived measures. This will extend our current understanding of the pathophysiology of severe asthma, and unravel the structure-function relationship, with the potential to discover novel severe asthma phenotypes, predict mortality, morbidity and response to existing and novel pharmacological and non-pharmacological therapies.

Difficult childhood asthma: management and future

Diagnosis and management of severe asthma implies the definition of different entities, that is, difficult asthma and refractory severe asthma, but also the different phenotypes included in the term refractory severe asthma. A complete evaluation by a physician expert in asthma is necessary, adapted for each child. Identification of mechanisms involved in different phenotypes in refractory severe asthma may improve the therapeutic approach. The quality of care and monitoring of children with severe asthma is as important as the prescription drug, and is also crucial for differentiating between severe asthma and difficult asthma, whereby expertise is required.

Resistin-like molecule-β is induced following bronchoconstriction of asthmatic airways

BACKGROUND AND OBJECTIVE

Resistin-like molecule-β (RELM-β) is a necessary and sufficient stimulus for airway remodelling in animal models of asthma, but until recently, its role in human disease had not been investigated. The hypothesis that RELM-β expression would increase with increasing asthma severity and further increase following acute bronchoconstrictor challenges has been examined.

METHODS

Bronchial biopsies from healthy subjects and patients with mild and severe asthma were immunostained for RELM-β, as were airway biopsies obtained in mild asthmatics before and 4 days after repeated inhalation challenges with either allergen, methacholine or methacholine preceded by salbutamol as a control. Bronchial brushings were also evaluated for RELM-β mRNA.

RESULTS

RELM-β immunoreactivity, which co-localized to airway epithelial cells, increased with disease severity; healthy volunteers, median per cent epithelial area 1.98%, mild asthma 3.49% and severe asthma 5.89% (P < 0.001 between groups). RELM-β immunoreactivity significantly and inversely correlated in asthma with forced expiratory volume in 1 s % predicted (P = 0.005). Acute changes in immunoexpression were evident after repeated inhalation challenge with allergen (2.15 % to 4.35 % (P = 0.01)) and methacholine (4.21 % to 6.16 % (P = 0.01)) but did not change in the salbutamol/methacholine challenge group. These changes correlated with change in basement membrane thickness (r = 0.38, P = 0.02). Epithelial RELM-β gene expression was not altered in asthma.

CONCLUSIONS

RELM-β may play an important role not only in animal models of airway remodelling, but also in human airway pathology.

Asthma and lung structure on computed tomography: the Multi-Ethnic Study of Atherosclerosis Lung Study

BACKGROUND

The potential consequences of asthma in childhood and young adulthood on lung structure in older adults have not been studied in a large, population-based cohort.

OBJECTIVE

The authors hypothesized that a history of asthma onset in childhood (age 18 years or before) or young adulthood (age 19-45 years) was associated with altered lung structure on computed tomography in later life.

METHODS

The Multi-Ethnic Study of Atherosclerosis Lung Study recruited 3965 participants and assessed asthma history by using standardized questionnaires, guideline-based spirometry, and segmental airway dimensions and percentage of low attenuation area (%LAA) on computed tomographic scans.

RESULTS

Asthma with onset in childhood and young adulthood was associated with large decrements in FEV(1) among participants with a mean age of 66 years (-365 mL and -343 mL, respectively; P < .001). Asthma with onset in childhood and young adulthood was associated with increased mean airway wall thickness standardized to an internal perimeter of 10 mm (0.1 mm, P < .001 for both), predominantly from narrower segmental airway lumens (-0.39 mm and -0.34 mm, respectively; P < .001). Asthma with onset in childhood and young adulthood also was associated with a greater %LAA (1.69% and 4.30%, respectively; P < .001). Findings were similar among never smokers, except that differential %LAA in childhood-onset asthma were not seen in them.

CONCLUSION

Asthma with onset in childhood or young adulthood was associated with reduced lung function, narrower airways, and among asthmatic patients who smoked, greater %LAA in later life.

The investigation of severe asthma to define phenotypes

Severe asthmatics often exhibit poor control despite high doses of inhaled corticosteroids with or without systemic corticosteroids and suffer from persistent symptoms and/or recurrent exacerbations. Five to ten percentage of the asthmatic population falls within this category. Patients with severe asthma are a heterogeneous group and should be investigated to confirm the diagnosis, identify comorbidities, exclude alternative diagnoses, together with an evaluation of treatment adherence and side-effects from medications. Optimization of asthma medications and monitoring the control and pattern of asthma usually takes place over a period of 6 months. In patients with confirmed severe refractory asthma, further evaluation is needed in terms of detailed lung function, of airway and lung structure using high resolution computed tomographic scanning, and of airway inflammatory processes and biomarkers using induced sputum or bronchial biopsies. Patients with severe asthma are best investigated and managed with a multidisciplinary team. Severe asthma consists of different phenotypes that need defining. Investigation of severe asthma should bring into the open the various characteristics of the disease that could point to particular phenotype. Inclusion of investigations based on transcriptomics and proteomics should expand, improve classification and understanding of severe asthma, with the ultimate hope of finding more effective treatments and a step towards personalized medicine.

How to diagnose and phenotype asthma

Asthma has been described as a chronic disease of the airways characterized by variable airflow obstruction, airway hyperresponsiveness, and airway inflammation. This review discusses the diagnosis and phenotyping of asthma, with a special emphasis on phenotyping based on the nature of cellular inflammation and radiological imaging and how this could be used to direct the treatment of asthma and, in the future, to apply specifically directed therapies to specific phenotypes.

Diagnostic tools assessing airway remodelling in asthma

Asthma is an inflammatory disease of the lower airways characterised by the presence of airway inflammation, reversible airflow obstruction and airway hyperresponsiveness and alterations on the normal structure of the airways, known as remodelling. Remodelling is characterised by the presence of metaplasia of mucous glands, thickening of the lamina reticularis, increased angiogenesis, subepithelial fibrosis and smooth muscle hypertrophy/hyperplasia. Several techniques are being optimised at present to achieve a suitable diagnosis for remodelling. Diagnostic tools could be divided into two groups, namely invasive and non-invasive methods. Invasive techniques bring us information about bronchial structural alterations, obtaining this information directly from pathological tissue, and permit measure histological modification placed in bronchi layers as well as inflammatory and fibrotic cell infiltration. Non-invasive techniques were developed to reduce invasive methods disadvantages and measure airway remodelling-related markers such as cytokines, inflammatory mediators and others. An exhaustive review of diagnostic tools used to analyse airway remodelling in asthma, including the most useful and usually employed methods, as well as the principal advantages and disadvantages of each of them, bring us concrete and summarised information about all techniques used to evaluate alterations on the structure of the airways. A deep knowledge of these diagnostic tools will make an early diagnosis of airway remodelling possible and, probably, early diagnosis will play an important role in the near future of asthma.

Computed tomography scans in severe asthma: utility and clinical implications

PURPOSE OF REVIEW

Asthma is a global burden, affecting 5% of the general adult population, of whom approximately 5-10% suffer from severe asthma. Severe asthma is a complex heterogeneous disease entity, with high morbidity and mortality. Increasingly novel techniques in computed tomography (CT) are being used to understand the pathophysiology of severe asthma. The utility and clinical implications of these CT techniques are the focus of this review.

RECENT FINDINGS

Novel qualitative and quantitative CT imaging techniques have enabled us to study the large airway architecture in detail, assess the small airway structure, and perform functional analysis of regional ventilation.

SUMMARY

Despite advances in CT imaging techniques, there is an urgent need for both proof-of-concept studies and large cross-sectional and longitudinal clinical trials in severe asthma to validate and clinically correlate imaging derived measures. This will extend our current understanding of the pathophysiology of severe asthma, and unravel the structure-function relationship, with the potential to discover novel severe asthma phenotypes and predict mortality, morbidity, and response to existing and novel pharmacological and nonpharmacological therapies.

[Airway remodeling in asthma: clinical and functional correlates]

Asthma is a chronic inflammatory disorder of the airways associated with bronchial hyperresponsiveness and permanent structural changes. Asthma can cause progressive lung impairment with a progressive decline of lung function leading to partially reversible or irreversible airway obstruction. These structural changes are called airway remodelling including loss of epithelial integrity, thickening of basement membrane, subepithelial fibrosis, goblet cell and submucosal gland enlargement, increase smooth muscle mass, decreased cartilage integrity and increased airway vascularity. These remodelling changes contribute to thickening of airway walls and consequently lead to airway narrowing, bronchial hyperresponsiveness, airway oedema and mucous hypersecretion. Airway remodelling is associated with a poorer clinical outcome among patients with asthma. Early diagnosis and prevention has the potential to decrease disease severity, to improve control and to prevent disease expression.

Impaired Ca²⁺ regulation of CD4⁺CD25⁺ regulatory T cells from pediatric asthma

BACKGROUND

CD4(+)CD25(+) regulatory T (T(reg)) cells can control the allergic response to allergen, airway eosinophilia and airway hypersensitivity. We speculated that chronic inflammation persisting in asthma airways is dependent on abnormalities of these T(reg) cells. There are differences in the pathology of asthma in adults and children, and the airways of pediatric asthma are considered to be more naive than those of adults. Therefore, we analyzed the functionality of T(reg) cells in pediatric asthma and the relationship between T(reg) function and asthma symptoms.

METHODS

The anergic state, which is one of the defining properties of T(reg), was analyzed by measuring intracellular Ca(2+) influx following T cell receptor (TCR) stimulation. FOXP3-positive cells and FOXP3 mRNA expression were measured by flow analysis and real-time PCR with the SYBR method, respectively.

RESULTS

CD45RO(+) cells make up approximately 99% of CD4(+)CD25(high) T cells and 89% of CD4(+)CD25(low) T cells in human adult blood. The proportion of CD45RO(+) cells in CD4(+)CD25(+) (high + low) T cells from pediatric asthma was much smaller (about 56%). Interestingly, our data indicated that CD45RO(+) T(reg) cells from pediatric asthma aberrantly increased intracellular Ca(2+) concentrations following TCR activation compared with pediatric nonasthma controls.

CONCLUSION

These impaired CD45RO(+) T(reg) cell functions were correlated with asthma symptoms. The correlation was observed in the group with a highly expressed atopic phenotype and longer duration of asthma. We suggest that chronic inflammation in pediatric asthma airways may be the result of impaired regulatory functions of CD45RO(+) T(reg) cells.

Management of severe asthma in children

Children who are referred to specialist care with asthma that does not respond to treatment (problematic severe asthma) are a heterogeneous group, with substantial morbidity. The evidence base for management is sparse, and is mostly based on data from studies in children with mild and moderate asthma and on extrapolation of data from studies in adults with severe asthma. In many children with severe asthma, the diagnosis is wrong or adherence to treatment is poor. The first step is a detailed diagnostic assessment to exclude an alternative diagnosis ("not asthma at all"), followed by a multidisciplinary approach to exclude comorbidities ("asthma plus") and to assess whether the child has difficult asthma (improves when the basic management needs, such as adherence and inhaler technique, are corrected) or true, therapy-resistant asthma (still symptomatic even when the basic management needs are resolved). In particular, environmental causes of secondary steroid resistance should be identified. An individualised treatment plan should be devised depending on the clinical and pathophysiological characterisation. Licensed therapeutic approaches include high-dose inhaled steroids, the Symbicort maintenance and reliever (SMART) regimen (with budesonide and formoterol fumarate), and anti-IgE therapy. Unlicensed treatments include methotrexate, azathioprine, ciclosporin, and subcutaneous terbutaline infusions. Paediatric data are needed on cytokine-specific monoclonal antibody therapies and bronchial thermoplasty. However, despite the interest in innovative approaches, getting the basics right in children with apparently severe asthma will remain the foundation of management for the foreseeable future.

Lung growth in infants and toddlers assessed by multi-slice computed tomography

RATIONALE AND OBJECTIVES

Postnatal lung growth and development have primarily been evaluated from a very limited number of autopsied lungs, but it remains unclear whether alveolarization of the lung is complete during infancy and whether the conducting airways grow proportionately. The purpose of this study was to evaluate lung growth and development in vivo in infants and toddlers using multislice computed tomography.

MATERIALS AND METHODS

Thirty-eight subjects (14 male, 24 female) aged 17 to 142 weeks underwent low-dose volumetric high-resolution computed tomographic imaging at an inflation pressure of 20 cm H(2)O during an induced respiratory pause. Lung volume and weight were determined, as well as airway dimensions (inner and outer area and wall area) for the trachea and the next three to four generations.

RESULTS

Lung volume, air volume, and tissue volume increased linearly with body length. The air and tissue components of the lung parenchyma increased at a constant rate with each other. In addition, airway caliber decreased with increasing generation from the trachea into each lobe. Airway caliber was also correlated with body length; however, there was no interaction effect between airway generation and body length on transformed airway size.

CONCLUSIONS

In vivo assessment suggests that the growth of the lung parenchyma in infants and toddlers occurred with a constant relationship between air volume and lung tissue, which is consistent with lung growth occurring primarily by the addition of alveoli rather than the expansion of alveoli. In addition, the central conducting airways grow proportionately in infants and toddlers. This information may be important for evaluating subjects with arrested lung development.

Airflow limitation and airway dimensions assessed per bronchial generation in older asthmatics

BACKGROUND

Computed tomography (CT) has been used for non-invasive quantitative assessment of airway dimensions, potentially showing airway remodeling, in asthma. However, most studies have examined either only one airway or only airways in anatomically unidentified cross-sections. Using software capable of precisely identifying the generation of airways and measuring airway dimensions perpendicular to the long axis of airways, we examined, in older patients with stable asthma, how inter-subject variation in airway dimensions correlated among the 3rd to 6th generation of airways, and then examined relationships between airway dimensions of each generation and indices of airflow limitation.

METHODS

Subjects aged ≥55 years old comprised 59 asthmatic patients who underwent CT and pulmonary function tests on the same day. We measured airway wall area (WA%) and inner luminal area (Ai) from the 3rd to the 6th generation of eight bronchi in the right lung.

RESULTS

Excellent correlations were identified for both WA% and Ai among the generations (r = 0.744-0.930 for WA%) when we took the average of all measured bronchi per generation as a personal representative value. Significant correlations of airflow limitation indices with both WA% and Ai/BSA were found at each of the 3rd to 6th generations with similar correlation coefficients (WA% for FEV(1) %predicted, r = -0.410 to -0.556).

CONCLUSIONS

In older patients with stable asthma, airway wall thickening and narrowing might occur in a parallel manner through 3rd to 6th generation airways. Airway dimensions at these areas of airways may thus have significant and similar correlations with indices of airflow limitation.

Endobronchial and transbronchial biopsies in children

The aim of this review is to describe the indications, techniques and side effects of bronchial biopsies in children. At present, two different types of bronchial biopsies are currently used: endobronchial biopsies (EBBs) and transbronchial biopsies (TBBs). These procedures are becoming more diffuse thanks to the extensive use of pediatric fiber optic bronchoscopes (FOBs). EBBs can be used to obtain specimens from the bronchial wall and from endobronchial masses, while TBBs permit collection of samples from peripheral lung parenchyma. The use of FOBs with a working channel of more than 2 mm in diameter allows the utilization of adequate forceps to obtain good specimens, even in children less than 2 years of age. This amplifies the research field of persistent lung diseases, such as cystic fibrosis and bronchial asthma. The main contraindication to perform bronchial biopsies is bleeding disorders. For research purposes, it is mandatory to obtain the approval of the Institutional Ethical Committee, the signed consent of the parents and the age-appropriate assent of the child.

Matrix metalloproteinase-12 is a therapeutic target for asthma in children and young adults

BACKGROUND

Matrix metalloproteinase (MMP)-12-mediated pathologic degradation of the extracellular matrix and the subsequent repair cycles influence the airway changes in patients with asthma and chronic obstructive pulmonary disease (COPD). The common serine variant at codon 357 of the MMP12 gene (rs652438) is associated with clinical manifestations consistent with more aggressive matrix degradation in other tissues.

OBJECTIVE

We sought to explore the hypothesis that MMP12 represents a novel therapeutic target in asthma.

METHODS

The role of the rs652438 variant on clinical phenotype was explored in young asthmatic patients and patients with COPD. Candidate MMP-12 inhibitors were identified on the basis of potency and selectivity against a panel of other MMPs. The role of MMP-12-specific inhibition was tested in vitro, as well as in animal models of allergic airway inflammation.

RESULTS

The odds ratio for having greater asthma severity was 2.00 (95% CI, 1.24-3.24; P = .004) when comparing asthmatic patients with at least 1 copy of the serine variant with those with none. The carrier frequency for the variant increased in line with asthma treatment step (P = .000). The presence of the variant nearly doubled the odds in favor of asthmatic exacerbations (odds ratio, 1.90; 95% CI, 1.19-3.04; P = .008) over the previous 6 months. The serine variant was also associated with increased disease severity in patients with COPD (P = .016). Prior administration of an MMP-12-specific inhibitor attenuated the early airway response and completely blocked the late airway response with subsequent Ascaris suum challenge in sheep.

CONCLUSION

Studies on human participants with asthma and COPD show that the risk MMP12 gene variant is associated with disease severity. In allergen-sensitized sheep pharmacologic inhibition of MMP12 downregulates both early and late airway responses in response to allergic stimuli.

Asma infantil y del lactante

El asma es la enfermedad crónica más frecuente de la infancia. El diagnóstico suele ser fácil cuando se producen episodios de disnea espiratoria con sibilancias reversibles de forma espontánea o mediante el uso de broncodilatadores. Las radiografías de tórax, la exploración funcional respiratoria y el estudio alérgico constituyen el aspecto fundamental de las pruebas complementarias necesarias. El tratamiento de la crisis consiste en el uso de β2-adrenérgicos inhalados y, si es necesario, corticoides orales. El tratamiento de fondo tiene como objetivo limitar al máximo los síntomas y restaurar o mantener las funciones pulmonares normales. Se debe adaptar a la gravedad y al control de la enfermedad y los corticoides inhalados tienen un papel de elección.

A new look at the pathogenesis of asthma

Asthma is an inflammatory disorder of the conducting airways that has strong association with allergic sensitization. The disease is characterized by a polarized Th-2 (T-helper-2)-type T-cell response, but in general targeting this component of the disease with selective therapies has been disappointing and most therapy still relies on bronchodilators and corticosteroids rather than treating underlying disease mechanisms. With the disappointing outcomes of targeting individual Th-2 cytokines or manipulating T-cells, the time has come to re-evaluate the direction of research in this disease. A case is made that asthma has its origins in the airways themselves involving defective structural and functional behaviour of the epithelium in relation to environmental insults. Specifically, a defect in barrier function and an impaired innate immune response to viral infection may provide the substrate upon which allergic sensitization takes place. Once sensitized, the repeated allergen exposure will lead to disease persistence. These mechanisms could also be used to explain airway wall remodelling and the susceptibility of the asthmatic lung to exacerbations provoked by respiratory viruses, air pollution episodes and exposure to biologically active allergens. Variable activation of this epithelial-mesenchymal trophic unit could also lead to the emergence of different asthma phenotypes and a more targeted approach to the treatment of these. It also raises the possibility of developing treatments that increase the lung's resistance to the inhaled environment rather than concentrating all efforts on trying to suppress inflammation once it has become established.

Bronchial measurements in patients with asthma: comparison of quantitative thin-section CT findings with those in healthy subjects and correlation with pathologic findings

PURPOSE

To analyze and compare computed tomographic (CT) bronchial measurements in patients with asthma and healthy subjects and to correlate bronchial morphometric parameters with functional data and immunohistologic markers of airway remodeling and inflammation.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board; patient informed consent was not required. CT and pulmonary function tests were performed in 27 patients separated into two groups: 15 patients with asthma (three men; mean age, 43.1 years +/- 5.3 [standard error of mean]) and 12 healthy subjects (10 men; mean age, 45.0 years +/- 5.4). Endobronchial biopsies were performed in 11 subjects. Bronchial cross-sectional wall area (WA) and lumen area (LA) were measured by using validated software, and wall thickness (WT), total area (TA), WA/LA ratio, and WA/TA ratio were computed. Slope and maximal local slope of each parameter along bronchial generations were calculated.

RESULTS

Patients with asthma demonstrated significantly lower LA, TA, and WA and higher WA/LA and WA/TA ratios than healthy subjects downward from the fourth bronchial generation. Correlations existed between slope and maximal local slope of WA/LA and/or WA/TA ratios and functional data reflecting bronchial obstruction (r = 0.46-0.58, P = .001-.025), subepithelial membrane thickness (r = 0.67-0.69, P = .019-.023), smooth muscle layer area (r = 0.75, P = .007), subepithelial layer area (r = 0.81, P = .002), and infiltration of the bronchial wall by inflammatory cells (r = 0.67-0.86, P = .049-.003).

CONCLUSION

Axial reconstructions with orthogonal measurements along the airways enabled by three-dimensional segmentation methods are able to demonstrate significant changes in bronchial morphometry, predicting airflow limitation in asthma, and may have a role in the noninvasive measurement of airway remodeling.

[Follow up of asthmatic children: definition and measurement tools]

The guidelines for the management of asthma currently emphasise the concept of monitoring that reflects the activity of the disease over a period of several weeks. This principle is valid whatever the severity of the asthma. The monitoring tools are essentially clinical and functional. The clinical parameters (daytime and/or nocturnal symptoms, discomfort on exercise, beta-2 agonist usage) should be evaluated systematically at each consultation just as at the onset of exacerbations. A number of questionnaires have been developed (ATAQ, ACT...). At the functional level every asthmatic child should have the benefit of a respiratory function assessment, the frequency of which depends on the therapeutic management programme. Among the non-invasive measurements of airway inflammation the measurement of expired nitric oxide (NO) is the best established. The measurement of expired NO could improve some paraclinical parameters that are not monitored routinely.

Partitioned exhaled nitric oxide to non-invasively assess asthma

Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperresponsiveness. Chronic repetitive bouts of acute inflammation lead to airway wall remodeling and possibly the sequelae of fixed airflow obstruction. Nitric oxide (NO) is a reactive molecule synthesized by NO synthases (NOS). NOS are expressed by cells within the airway wall and functionally, two NOS isoforms exist: constitutive and inducible. In asthma, the inducible isoform is over expressed, leading to increased production of NO, which diffuses into the airway lumen, where it can be detected in the exhaled breath. The exhaled NO signal can be partitioned into airway and alveolar components by measuring exhaled NO at multiple flows and applying mathematical models of pulmonary NO dynamics. The airway NO flux and alveolar NO concentration can be elevated in adults and children with asthma and have been correlated with markers of airway inflammation and airflow obstruction in cross-sectional studies. Longitudinal studies which specifically address the clinical potential of partitioning exhaled NO for diagnosis, managing therapy, and predicting exacerbation are needed.

Airway remodeling measured by multidetector CT is increased in severe asthma and correlates with pathology

BACKGROUND

To prospectively apply an automated, quantitative three-dimensional approach to imaging and airway analysis to assess airway remodeling in asthma patients.

METHODS

Using quantitative software (Pulmonary Workstation, version 0.139; VIDA Diagnostics; Iowa City, IA) that enables quantitative airway segment measurements of low-dose, thin-section (0.625 to 1.25 mm), multidetector-row CT (MDCT) scans, we compared airway wall thickness (WT) and wall area (WA) in 123 subjects participating in a prospective multicenter cohort study, the National Institutes of Health Severe Asthma Research Program (patients with severe asthma, n = 63; patients with mild-to-moderate asthma, n = 35); and healthy subjects, n = 25). A subset of these subjects underwent fiberoptic bronchoscopy and endobronchial biopsies (n = 32). WT and WA measurements were corrected for total airway diameter and area: WT and WA, respectively.

RESULTS

Subjects with severe asthma had a significantly greater WT% than patients with mild-to-moderate asthma and healthy subjects (17.2 +/- 1.5 vs 16.5 +/- 1.6 [p = 0.014] and 16.3 +/- 1.2 [p = 0.031], respectively) and a greater WA percentage (WA%) compared to patients with mild-to-moderate asthma and healthy subjects (56.6 +/- 2.9 vs 54.7 +/- 3.3 [p = 0.005] and 54.6 +/- 2.4 [p = 0.003], respectively). Both WT% and WA% were inversely correlated with baseline FEV(1) percent predicted (r = -0.39, p < 0.0001 and r = -0.40, p < 0.0001, respectively) and positively correlated with response to a bronchodilator (r = 0.28, p = 0.002 and r = 0.35, p < 0.0001, respectively). The airway epithelial thickness measure on the biopsy sample correlated with WT% (r = 0.47; p = 0.007) and WA% (r = 0.52; p = 0.003). In the same individual, there is considerable regional heterogeneity in airway WT.

CONCLUSION

Patients with severe asthma have thicker airway walls as measured on MDCT scan than do patients with mild asthma or healthy subjects, which correlates with pathologic measures of remodeling and the degree of airflow obstruction. MDCT scanning may be a useful technique for assessing airway remodeling in asthma patients, but overlap among the groups limits the diagnostic value in individual subjects.

[What methods can we use to measure inflammation in the asthmatic child?]

Pulmonary function tests remain the best method to assess underlying bronchial inflammation, particularly distal airway flow. However, these tests are limited in their ability to differentiate treatment-reversible small airway obstruction from definitive remodeling related to a viral infection. The increased availability of the exhaled fraction of nitric oxide (FeNO) measurement means that this method is accessible and attractive. In spite of a number of studies, mainly in adults, its use in the management of asthma needs more investigation. Threshold values that permit optimum management are poorly defined, and strategies based on variations of FeNO do not result in reduction of the number of exacerbations, although they do permit better control of drug use and better control of inflammation. Sputum eosinophil counts are of interest for the prevention of exacerbations, although while not well validated they may be useful in some asthmatic children. Also, they require an experienced cytology laboratory. Finally, recent data on bronchial biopsies in children with difficult-to-treat asthma will be summarized.

How early do airway inflammation and remodeling occur?

Eosinophilic airway inflammation and structural airway changes are present in school age asthmatics. When these changes occur, and their relationship, are controversial. Some structural airway changes, up-regulation of collagens 1 and 111, and increased distance between alveolar tethering points, may be antenatal, and independent of inflammation. We have established that there is no eosinophilic inflammation or reticular basement membrane thickening in wheezing infants median age one year; but by age three years, both are present. This accords with cohort studies, showing that children who become persistent wheezers have a drop in lung function in the pre-school years. Thereafter, lung function tracks into middle age, so the preschool years represent window during which an intervention might have long term benefit. Supportive are measurements in blood and bronchoalveolar lavage fluid, implicating the neutrophil as the key inflammatory cell in early wheeze. Models of the pathophysiology of asthma include (1) that eosinophilic inflammation is the primary event, and leads to remodelling as a secondary event, which itself results in progressive airflow obstruction (the least likely model); (2) eosinophilic inflammation is the primary event, but remodelling is protective, preventing worsening AHR. It should be noted that these first two are not mutually exclusive; rbm thickening may be protective, but other components of remodeling, for example increased ASM, may have adverse effects; (3) eosinophilic inflammation and airway remodelling are parallel processes, driven by some underlying 'asthma factor'; and (4) the primary abnormality is not airway inflammation, but some form of disordered airway repair.

TGFB1 promoter polymorphism C-509T and pathophysiology of asthma

BACKGROUND

TGF-beta1 can modulate airway inflammation and exaggerate airway remodeling. A polymorphism of a promoter region of TGFB1, C-509T, might be associated with the development of asthma, but its pathophysiologic relevance remains poorly understood.

OBJECTIVE

We investigated relations of the C-509T polymorphism to airflow obstruction, sputum eosinophilia, and airway wall thickening, as assessed by means of computed tomography, in 85 patients with stable asthma.

METHODS

The CC, CT, and TT genotypes were examined by means of PCR and restriction enzyme fragment length polymorphism. At a selected bronchus, 3 indices of airway wall thickness were measured with an automatic method.

RESULTS

The CC, CT, and TT genotypes were found in 22, 46, and 17 patients, respectively. Serum TGF-beta1 levels were significantly associated with the polymorphism and were increased in the CT/TT genotypes. FEV(1) and sputum eosinophil percentages were also significantly associated with the polymorphism and were both decreased in the CT/TT genotypes. The polymorphism was unrelated to airway wall thickness.

CONCLUSION

In addition to increased serum TGF-beta1 levels, the T allele of the C-509T polymorphism is related to increased airflow obstruction but attenuated eosinophilic inflammation. The former relation is not attributed to thickening of the central airway walls. The latter relation might reflect the anti-inflammatory effect of TGF-beta1. The C-509T polymorphism has a complex role in asthma pathophysiology, presumably because of the diverse functions of TGF-beta1 and its various interactions with cells and humoral factors in vivo.

Basement membrane thickening and clinical features of children with asthma

BACKGROUND

Asthma is a chronic inflammatory disease, characterized by airway inflammation, bronchial hyper-responsiveness, and airway obstruction. Although asthma induces partially reversible airway obstruction, obstruction can sometimes become irreversible. This may be a consequence of airway remodeling, which includes a number of structural changes, such as epithelial detachment, basement membrane (BM) thickening, smooth muscle hypertrophy, and new vessel formation. This study evaluated children with asthma for the presence of BM thickening.

METHODS

Eighteen children with asthma and 24 control subjects underwent flexible bronchoscopy with endobronchial biopsy. Light microscopy was used to measure BM thickness in paraffin-embedded biopsy sections. The association between BM thickening and age, sex, duration of asthma, asthma severity, FEV(1), FEV(1)/FVC, FEF(25-75%), methacholine PC(20), eosinophil count, and presence of atopy was examined.

RESULTS

Basement membrane thickness was greater in subjects with asthma (8.3 +/- 1.4 microM) than in control subjects (6.8 +/- 1.3 microM, P = 0.0008). Multiple regression analysis revealed that sex, FEV(1)/FVC, total IgE, and atopy (IgE for Dermatophagoides pteronyssinus >0.34 kUA/l) were significant predictive factors for BM thickness. There was no significant association between BM thickness and age, duration of asthma, FEV(1), FEF(25-75%), methacholine PC(20), eosinophil count, or asthma severity.

CONCLUSIONS

Basement membrane thickening has been known to be present in children with asthma. In addition, we report an association between BM thickness and sex, FEV(1)/FVC, total IgE, and the presence of IgE specific to D. pteronyssinus.

Airway remodelling in children: when does it start?

PURPOSE OF REVIEW

The review characterizes airway remodelling in childhood asthma and describes how early in life it is possible to detect, and possibly cure, the cellular and biochemical changes that characterize this event. This topic is timely and relevant since a variety of clinical and epidemiologic studies strongly suggest that in asthma, remodelling may start very early in life and that current prevention and treatment measures, including early avoidance measures and pharmaceutical interventions, are relatively ineffective in preventing the development of irreversible airway changes or in reverting them, once established.

RECENT FINDINGS

Recent findings show that structural changes characterizing remodelling, such as subepithelial basement membrane thickening, epithelial cell disruption, protease/antiprotease imbalance and neoangiogenesis, are detectable in children with asthma and even in children with respiratory symptoms or with atopy, before a clear clinical diagnosis of bronchial asthma is made.

SUMMARY

Identification of the early structural changes that may precede the development of asthma and of factors leading to permanent loss of lung function appear central to future asthma management.

The use of imaging techniques for assessing severe childhood asthma

Computed tomography (CT) scans are usually performed in children with asthma to exclude alternative diagnoses. Technical improvements of high-resolution CT (HRCT) scans have increased the spatial resolution sufficiently for the theoretical quantification of bronchial wall thickening of the proximal airways and the assessment of small airway disease by the extent and degree of low attenuation areas, which are believed to represent air trapping. In contrast with adults, very few studies have been performed in children. The results suggest that the HRCT scan might be useful as a noninvasive technique for airway inflammation and airway remodeling. In the future, the potential use of HRCT scans for determining optimal treatment should be evaluated. However, several issues remain to be resolved, including the validity of algorithm reconstruction, the imaging parameters to be used, and the application of this technique to young children. Furthermore, because of its cost and the irradiation involved, this examination is highly unlikely to be used routinely for the management and follow-up of all children with asthma but will likely be restricted to patients with severe asthma.

Understanding the pathophysiology of severe asthma to generate new therapeutic opportunities

Although asthma is defined in terms of reversibility of airflow obstruction, as the disease becomes more severe and chronic, it adopts different characteristics, including a degree of fixed airflow obstruction and corticosteroid refractoriness. Underlying these phenotypes is evidence of airway wall remodeling, which should be distinguished from the increase in smooth muscle linked to airways hyperresponsiveness. Aberrant epithelial-mesenchymal communication leads to a chronic wound scenario, which is characterized by activation of the epithelial-mesenchymal trophic unit, epithelial damage, the laying down of new matrix, and greater involvement of neutrophils in the inflammatory response. In allergic asthmatic patients who remain symptomatic despite high-dose corticosteroid therapy, blockade of IgE with omalizumab confers appreciable clinical benefit. Chronic severe asthma is also accompanied by a marked increase in TNF-alpha production that might contribute to corticosteroid refractoriness. Based on this, TNF blockade with the soluble fusion protein entanercept produces improvement in asthma symptoms, lung function, and quality of life paralleled by a marked reduction in airways hyperresponsiveness. Identification of novel susceptibility genes, such as a disintegrin and metalloprotease 33 (ADAM33), will provide further targets against which to direct novel therapies for asthma, especially at the more severe end of the disease spectrum.