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BACKGROUND: Airway mucus plugs in asthma are associated with exacerbation frequency, increased eosinophilia, and reduced lung function. The relationship between mucus plugs and spatially overlapping ventilation abnormalities observed at hyperpolarized gas MRI has not been assessed quantitatively. PURPOSE: To assess regional associations between CT mucus plugs scored by individual bronchopulmonary segment and corresponding measurements of segmental ventilation defect percentage (VDP) at hyperpolarized helium 3 ((3)He) MRI. MATERIALS AND METHODS: In this secondary analysis of a Health Insurance Portability and Accountability Act–compliant prospective observational cohort, participants in the Severe Asthma Research Program (SARP) III (NCT01760915) between December 2012 and August 2015 underwent hyperpolarized (3)He MRI to determine segmental VDP. Segmental mucus plugs at CT were scored by two readers, with segments scored as plugged only if both readers agreed independently. A linear mixed-effects model controlling for interpatient variability was then used to assess differences in VDP in plugged versus plug-free segments. RESULTS: Forty-four participants with asthma were assessed (mean age ± standard deviation, 47 years ± 15; 29 women): 19 with mild-to-moderate asthma and 25 with severe asthma. Mucus plugs were observed in 49 total bronchopulmonary segments across eight of 44 patients. Segments containing mucus plugs had a median segmental VDP of 25.9% (25th–75th percentile, 7.3%–38.3%) versus 1.4% (25th–75th percentile, 0.1%–5.2%; P < .001) in plug-free segments. Similarly, the model estimated a segmental VDP of 18.9% (95% CI: 15.7, 22.2) for mucus-plugged segments versus 5.1% (95% CI: 3.3, 7.0) for plug-free segments (P < .001). Participants with one or more mucus plugs had a median whole-lung VDP of 11.1% (25th–75th percentile, 7.1%–18.9%) versus 3.1% (25th–75th percentile, 1.1%–4.4%) in those without plugs (P < .001). CONCLUSION: Airway mucus plugging at CT was associated with reduced ventilation in the same bronchopulmonary segment at hyperpolarized helium 3 MRI, suggesting that mucus plugging may be an important cause of ventilation defects in asthma. © RSNA, 2021 Online supplemental material is available for this article.

Children with asthma are at risk for low lung function extending into adulthood, but understanding of clinical predictors is incomplete.We sought to determine phenotypic factors associated with FEVLung function was measured at baseline and annually. Multivariate linear mixed-effects models were constructed to assess the effect of baseline and time-varying predictors of prebronchodilator FEVA total of 862 spirometry assessments were performed for 188 participants. Factors associated with FEVIn children with severe and nonsevere asthma, several clinically relevant factors predict FEV

BACKGROUND: Hyperpolarized helium 3 magnetic resonance imaging ((3)He MRI) is useful for investigating pulmonary physiology of pediatric asthma, but a detailed assessment of the safety profile of this agent has not been performed in children. OBJECTIVE: To evaluate the safety of (3)He MRI in children and adolescents with asthma. MATERIALS AND METHODS: This was a retrospective observational study. (3)He MRI was performed in 66 pediatric patients (mean age 12.9 years, range 8–18 years, 38 male, 28 female) between 2007 and 2017. Fifty-five patients received a single repeated examination and five received two repeated examinations. We assessed a total of 127 (3)He MRI exams. Heart rate, respiratory rate and pulse oximetry measured oxygen saturation (SpO(2)) were recorded before, during (2 min and 5 min after gas inhalation) and 1 h after MRI. Blood pressure was obtained before and after MRI. Any subjective symptoms were also noted. Changes in vital signs were tested for significance during the exam and divided into three subject age groups (8–12 years, 13–15 years, 16–18 years) using linear mixed-effects models. RESULTS: There were no serious adverse events, but three minor adverse events (2.3%; headache, dizziness and mild hypoxia) were reported. We found statistically significant increases in heart rate and SpO(2) after (3)He MRI. The youngest age group (8–12 years) had an increased heart rate and a decreased respiratory rate at 2 min and 5 min after (3)H inhalation, and an increased SpO(2) post MRI. CONCLUSION: The use of (3)He MRI is safe in children and adolescents with asthma.

Asthma is a heterogeneous disease, with multiple underlying inflammatory pathways and structural airway abnormalities that impact disease persistence and severity. Recent progress has been made in developing targeted asthma therapeutics, especially for subjects with eosinophilic asthma. However, there is an unmet need for new approaches to treat patients with severe and exacerbation-prone asthma, who contribute disproportionately to disease burden. Extensive deep phenotyping has revealed the heterogeneous nature of severe asthma and identified distinct disease subtypes. Acurrent challenge in the field is to translate new and emerging knowledge about different pathobiologic mechanisms in asthma into patient-specific therapies, with the ultimate goal of modifying the natural history of disease. Here, we describe the Precision Interventions for Severe and/or Exacerbation-Prone Asthma (PrecISE) Network, a groundbreaking collaborative effort of asthma researchers and biostatisticians from around the United States. The PrecISE Network was designed to conduct phase II/proof-of-concept clinical trials of precision interventions in the population with severe asthma, and is supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health. Using an innovative adaptive platform trial design, the PrecISE Network will evaluate up to 6 interventions simultaneously in biomarker-defined subgroups of subjects. We review the development and organizational structure of the PrecISE Network, and choice of interventions being studied. We hope that the PrecISE Network will enhance our understanding of asthma subtypes and accelerate the development of therapeutics for severe asthma.

Clinical case series suggest beneficial effects of low-dose intermittent hypoxia in asthma. We tested cardiopulmonary effects of repetitive acute hypoxic preconditioning (RAHP) during allergic inflammation. Brown Norway rats were sensitized to house dust mites (HDM) and exposed to 4-week RAHP or normoxia (SHAM), concurrent with weekly HDM or saline (SAL) challenges. We assessed methacholine responses and lung HIF-1α expression at endpoint, and weekly blood pressure (BP). RAHP relative to SHAM: 1) in HDM-challenged rats, showed no protection against HDM-induced airway dysfunction and did not significantly impact BP (week 4 mean BP difference = 10.51 mmHg, p = 0.09) or HIF-1α expression; 2) in SAL-challenged rats, attenuated airway responses to methacholine, reduced BP (week 4 mean BP average difference = -8.72 mmHg, p = 0.04) and amplified HIF-1α expression (p = 0.0086). Four weeks of RAHP did not mitigate the allergen-induced lower airway dysfunction and may detrimentally affect BP. However, it elicited beneficial cardiopulmonary responses in SAL-challenged rats, concurrent with increased HIF-1α expression.

Background Despite advances in asthma care, disparities persist. Black patients are disproportionally affected by asthma and also have poorer outcomes compared with white patients. Objective We sought to determine associations between black and white patients and asthma-related health care use, accounting for complex relationships. Methods This study was completed as part of the National Heart, Lung, and Blood Institute's Severe Asthma Research Program, a prospective observational cohort. Between November 2012 and February 2015, it enrolled 579 participants 6 years and older with 1 year of observation time and complete data. Inverse probability of treatment weighting was used to balance racial groups with respect to community and family socioeconomic variables and environmental exposure variables. The primary outcome was emergency department (ED) use for asthma. Secondary outcomes included inhaled corticosteroid use, outpatient physician's office visits for asthma, and asthma–related hospitalization. Results Black patients had greater odds of ED use over 1 year (odds ratio, 2.19; 95% CI, 1.43-3.35) but also differed in the majority (>50%) of baseline variables measured. After statistical balancing of the racial groups, the difference between black and white patients with respect to ED use no longer reached the level of significance. Instead, in secondary analyses black patients were less likely to see an outpatient physician for asthma management (adjusted odds ratio, 0.57; 95% CI, 0.38-0.85). Conclusions The disparity in ED use was eliminated after consideration of multiple variables. Social and environmental policies and interventions tailored to black populations with a high burden of asthma are critical to reduction (or elimination) of these disparities.

Rationale: Corticosteroids (CSs) are the most effective asthma therapy, but responses are heterogeneous and systemic CSs lead to long-term side effects. Therefore, an improved understanding of the contributing factors in CS responses could enhance precision management. Although several factors have been associated with CS responsiveness, no integrated/cluster approach has yet been undertaken to identify differential CS responses. Objectives: To identify asthma subphenotypes with differential responses to CS treatment using an unsupervised multiview learning approach. Methods: Multiple-kernel k-means clustering was applied to 100 clinical, physiological, inflammatory, and demographic variables from 346 adult participants with asthma in the Severe Asthma Research Program with paired (before and 2-3 weeks after triamcinolone administration) sputum data. Machine-learning techniques were used to select the top baseline variables that predicted cluster assignment for a new patient. Measurements and Main Results: Multiple-kernel clustering revealed four clusters of individuals with asthma and different CS responses. Clusters 1 and 2 consisted of young, modestly CS-responsive individuals with allergic asthma and relatively normal lung function, separated by contrasting sputum neutrophil and macrophage percentages after CS treatment. The subjects in cluster 3 had late-onset asthma and low lung function, high baseline eosinophilia, and the greatest CS responsiveness. Cluster 4 consisted primarily of young, obese females with severe airflow limitation, little eosinophilic inflammation, and the least CS responsiveness. The top 12 baseline variables were identified, and the clusters were validated using an independent Severe Asthma Research Program test set. Conclusions: Our machine learning-based approaches provide new insights into the mechanisms of CS responsiveness in asthma, with the potential to improve disease treatment.

Rationale: It is unclear why select patients with moderate-to-severe asthma continue to lose lung function despite therapy. We hypothesized that participants with the smallest responses to parenteral corticosteroids have the greatest risk of undergoing a severe decline in lung function.Objectives: To evaluate corticosteroid-response phenotypes as longitudinal predictors of lung decline.Methods: Adults within the NHLBI SARP III (Severe Asthma Research Program III) who had undergone a course of intramuscular triamcinolone at baseline and at ≥2 annual follow-up visits were evaluated. Longitudinal slopes were calculated for each participant's post-bronchodilator FEV1% predicted. Categories of participant FEV1 slope were defined: severe decline, >2% loss/yr; mild decline, >0.5-2.0% loss/yr; no change, 0.5% loss/yr to

There is a growing motivation for imaging regional lung ventilation. Global measures of lung function such as spirometry are not able to distinguish patterns of obstruction and regional reversibility in response to intervention. Advantages of MRI for lung imaging include use of nonionizing radiation and flexibility for acquiring dynamic, multidimensional signal changes in response to changes in lung function. For these reasons, MRI is particularly attractive for longitudinal studies of chronic lung disease, especially in pediatric populations. There are two broad classes of ventilation imaging methods using MRI, which have matured over the past decade: proton-based methods and direct imaging of exogenous gases using multinuclear MRI and spectroscopy. This chapter will provide a review of the theory and rationale of ventilation imaging with MRI, results of clinical research in ventilation MRI, and emerging methods of ventilation imaging. Proton MRI ventilation imaging techniques covered in this chapter include deformable image registration, Fourier decomposition, and oxygen-enhanced methods. This chapter also covers ventilation techniques utilizing MRI of visible gas nuclei, including hyperpolarized gas MRI and perfluorinated gas MRI.

Background: Severe asthma has multiple phenotypes for which biomarkers are still being defined. Plasma P-selectin reports endothelial and/or platelet activation. Objective: To determine if P-selectin is associated with features of asthma in a longitudinal study. Methods: Plasmas from 70 adult patients enrolled in the Severe Asthma Research Program (SARP) III at the University of Wisconsin-Madison were analyzed for concentration of P-selectin at several points over the course of 3 years, namely, at baseline (BPS), after intramuscular triamcinolone acetonide (TA) injection, and at 36 months after baseline. Thirty-four participants also came in during acute exacerbation and 6 weeks after exacerbation. Results: BPS correlated inversely with forced expiratory volume in 1 s (FEV1) and with residual volume/total lung capacity, an indicator of air trapping. BPS was inversely associated with FEV1 change after TA, by regression analysis. FEV1 did not change significantly after TA if BPS was above the median, whereas patients with BPS below the median had significantly increased FEV1 after TA. BPS was higher in and predicted assignment to SARP phenotype cluster 5 (“severe fixed-airflow asthma”). P-selectin was modestly but significantly increased at exacerbation but returned to baseline within 3 years. Conclusions: High BPS is associated with airway obstruction, air trapping, the “severe fixed-airflow” cluster, and lack of FEV1 improvement in response to TA injection. P-selectin concentration, which is a stable trait with only modest elevation during exacerbation, may be a useful biomarker for a severe asthma pheno- or endotype characterized by low pulmonary function and lack of corticosteroid responsiveness.

Rationale and Objectives To determine lobar ventilation patterns in asthmatic lungs with hyperpolarized 3He magnetic resonance imaging (HP 3He MRI). Materials and Methods Eighty-two subjects (14 normal, 48 mild-to-moderate asthma, and 20 severe asthma) underwent HP 3He MRI, computed tomography (CT), and pulmonary function testing. After registering proton to 3He images, we segmented the lungs from proton MRI and further segmented the five lung lobes (right upper lobe [RUL], right middle lobe [RML], and right lower lobe [RLL]; left upper lobe and left lower lobe [LLL]) by referring to the lobar segmentation from CT. We classified the gas volume into four signal intensity levels as follows: ventilation defect percent (VDP), low ventilation percent, medium ventilation percent, and high ventilation percent. The local signal intensity variations in the ventilated volume were estimated using heterogeneity score (Hs). We compared each ventilation level and Hs measured in the whole lung and lobar regions across the three subject groups. Results In mild-to-moderate asthma, the RML and RUL showed significantly greater VDP than the two lower lobes (RLL and LLL) (P ≤ .047). In severe asthma, the pattern was more variable with the VDP in the RUL significantly greater than in the RLL (P = .026). In both asthma groups, the lower lobes (RLL and LLL) showed significantly higher high ventilation percent and Hs compared to the three upper lobes (all P ≤ .015). Conclusions In asthma, the RML and RUL showed greater ventilation abnormalities, and the RLL and LLL were more highly ventilated with greater local heterogeneity. These findings may facilitate guided bronchoscopic sampling and localized airway treatment in future studies.

Background There is an unmet need for an objective biomarker to predict asthma exacerbations. Objective Our aim was to assess the ventilation defect percent (VDP) on hyperpolarized helium-3 magnetic resonance imaging as a predictor of exacerbation frequency following imaging. Methods Subjects underwent hyperpolarized helium-3 and conventional clinical measurements, including pulmonary function tests, during a period of disease stability, and exacerbations were recorded prospectively over the following 2 years. We used a Poisson regression tree model to estimate an optimal VDP threshold for classifying subjects into high- versus low-exacerbation groups and then used statistical regression to compare this VDP threshold against conventional clinical measures as predictors of exacerbations. Results A total of 67 individuals with asthma (27 males and 40 females, 28 with mild-to-moderate asthma and 39 with severe asthma) had a median VDP of 3.75% (1.2% [first quartile]-7.9% [third quartile]). An optimal VDP threshold of 4.28% was selected on the basis of the maximum likelihood estimation of the regression tree model. Subjects with a VDP greater than 4.28% (n = 32) had a median of 1.5 exacerbations versus 0.0 for subjects with a VDP less than 4.28% (n = 35). In a stepwise multivariate regression model, a VDP greater than 4.28% was associated with an exacerbation incidence rate ratio of 2.5 (95% CI = 1.3-4.7) versus a VDP less than or equal to 4.28%. However, once individual medical history was included in the model, VDP was no longer significant. Nonetheless, VDP may provide an objective and complementary quantitative marker of individual exacerbation risk that is useful for monitoring individual change in disease status, selecting patients for therapy, and assessing treatment response. Conclusion VDP measured with magnetic resonance imaging shows promise as a biomarker of prospective asthma exacerbations.

RATIONALE: In practice, asthma control is assessed according to symptom burden and office spirometry. However spirometry poorly tests peripheral lung function, which may be abnormal in asthma. Impluse oscillometry (IOS) and multiple-breath washout (MBW) are novel methods which measure reactance (X5) and ventilation heterogeneity (VH) in the peripheral lung, but how well these tests reflect asthma control is poorly understood. OBJECTIVE: To compare the diagnostic accuracy of tests of large airways caliber (FEV¬1¬, FEV¬1-/FVC, R20), peripheral zone properties (X5, VH), and airways inflammation (FeNO) as predictors of poor control in asthmatic children (44 poorly-controlled/10 controlled). METHODS: 54 children enriched in severe asthma completed a symptom-based control scale (ACT/cACT) and lung function tests after overnight bronchodilator withhold. The accuracy of each variable to predict poor control was ranked by area under the receiver operating characteristic (ROC) curve, sensitivity, and specificity. RESULTS: Among measures of large airways caliber, the FEV¬1¬% had the highest ROC curve area, with low sensitivity but perfect specificity. Among measures of peripheral lung function, X5 and VH in the conducting zone had fair curve areas with higher sensitivity but lower specificity compared to the FEV¬1¬%. VH in the acinar zone and FeNO both had poor accuracy. CONCLUSION: Tests of large airway and peripheral zone lung function performed disparately as predictors of poor control in a sample of children enriched in severe asthma. Further studies in a larger sample with more diverse phenotypic features are necessary to validate this preliminary conclusion.

Background Tools for quantification of asthma severity are limited. Objective We sought to develop a continuous measure of asthma severity, the Asthma Severity Scoring System (ASSESS), for adolescents and adults, incorporating domains of asthma control, lung function, medications, and exacerbations. Methods Baseline and 36-month longitudinal data from participants in phase 3 of the Severe Asthma Research Program (NCT01606826) were used. Scale properties, responsiveness, and a minimally important difference were determined. External replication was performed in participants enrolled in the Severe Asthma Research Program phase 1/2. The utility of ASSESS for detecting treatment response was explored in participants undergoing corticosteroid responsiveness testing with intramuscular triamcinolone and participants receiving biologics. Results ASSESS scores ranged from 0 to 20 (8.78 ± 3.9; greater scores reflect worse severity) and differed among 5 phenotypic groups. Measurement properties were acceptable. ASSESS was responsive to changes in quality of life with a minimally important difference of 2, with good specificity for outcomes of asthma improvement and worsening but poor sensitivity. Replication analyses yielded similar results, with a 2-point decrease (improvement) associated with improvements in quality of life. Participants with a 2-point or greater decrease (improvement) in ASSESS scores also had greater improvement in lung function and asthma control after triamcinolone, but these differences were limited to phenotypic clusters 3, 4, and 5. Participants treated with biologics also had a 2-point or greater decrease (improvement) in ASSESS scores overall. Conclusions The ASSESS tool is an objective measure that might be useful in epidemiologic and clinical research studies for quantification of treatment response in individual patients and phenotypic groups. However, validation studies are warranted.

The purpose of this work was to quantify the redistribution of ventilation-weighted signal in the lungs of asthmatic subjects during a breath-hold using high temporal-spatial resolution hyperpolarized (HP) He-3 MRI. HP He-3 MRI was used to obtain time-resolved, volumetric images of lung ventilation during breath-hold in 39 human subjects classified as either healthy/nondiseased ( n = 14), mild-to-moderate asthmatic ( n = 17), or severely asthmatic ( n = 8). Signals were normalized to a standard lung volume, so that voxels within the lung from all 39 subjects could be analyzed as a group to increase statistical power and enable semiautomated classification of voxels into 1 of 5 ventilation level categories (ranging from defect to hyperintense). End-inspiratory ventilation distribution and temporal rates of mean signal change for each of the five ventilation categories were compared using ANOVA. Time rates of signal change were hypothesized to represent underlying gas redistribution processes, potentially influenced by disease. We found that mild-to-moderate asthmatic subjects showed the greatest rate of signal change, even though those with severe asthma had the greatest end-inspiration ventilation heterogeneity. The observed results support the existence of local differences in airway resistances associated with the different obstructive patterns in the lungs for severe vs. mild-to-moderate asthmatic subjects.

Background The effect of age on asthma severity is poorly understood. Objectives The objective of this study was to compare the baseline features of severe and nonsevere asthma in the Severe Asthma Research Program (SARP) III cohort, and examine in cross section the effects of age on those features. Methods SARP III is a National Institutes of Health/National Heart Lung Blood Institute multisite 3-year cohort study conducted to investigate mechanisms of severe asthma. The sample included 188 children (111 severe, 77 nonsevere) and 526 adults (313 severe, 213 nonsevere) characterized for demographic features, symptoms, health care utilization, lung function, and inflammatory markers compared by age and severity. Results Compared with children with nonsevere asthma, children with severe asthma had more symptoms and more historical exacerbations, but no difference in body weight, post-bronchodilator lung function, or inflammatory markers. After childhood, and increasing with age, the cohort had a higher proportion of women, less allergen sensitization, and overall fewer blood eosinophils. Enrollment of participants with severe asthma was highest in middle-aged adults, who were older, more obese, with greater airflow limitation and higher blood eosinophils, but less allergen sensitization than adults with nonsevere asthma. Conclusions The phenotypic features of asthma differ by severity and with advancing age. With advancing age, patients with severe asthma are more obese, have greater airflow limitation, less allergen sensitization, and variable type 2 inflammation. Novel mechanisms besides type 2 inflammatory pathways may inform the severe asthma phenotype with advancing age.

Background Sex influences the risk of wheezing illnesses and the prevalence of asthma throughout childhood. Objective To better understand the mechanisms of these effects, we analyzed longitudinal relationships between sex, lung physiology, and asthma in the Childhood Origins of ASThma birth cohort study. Methods Childhood Origins of ASThma birth cohort study children were followed prospectively from birth and assessed annually. Results of spirometry, fractional exhaled nitric oxide (Feno), mannitol provocation testing, and 3 He gas magnetic resonance imaging were assessed by sex using multivariate models including age, asthma diagnosis, and wheezing histories. Results Girls had higher prebronchodilator forced expiratory volume in 0.5 seconds/forced vital capacity values than did boys (mean difference, 0.017; 95% CI, 0.000-0.034; P = .05) of equivalent age. Postbronchodilator findings were more pronounced, with boys demonstrating reduced forced expiratory volume in 0.5 seconds/forced vital capacity values than did girls of equivalent age (mean difference, 0.032; 95% CI, 0.014-0.049; P = .0005). Conversely, girls were noted to have higher ventilation defects on 3 He magnetic resonance imaging than did boys ( P = .01). No differences were noted in the rate of positive responses to mannitol provocation or Feno measurements. Conclusions Lower airflow values are present by spirometry for prepubertal boys than for age-matched girls; however, greater 3 He ventilation defects were noted in girls. This could represent a greater degree of subclinical air trapping in prepubertal girls because residual volumes are not detected on standard spirometric readings. No differences were noted between the 2 sexes with airway hyperresponsiveness (mannitol provocation testing) or inflammation (Feno). Prospective peripubertal follow-up will determine whether these differences persist or change with the de novo expression and remission of asthma based on sex and age.

RationalePhenotypic distinctions between severe asthma (SA) and nonsevere asthma (NONSA) may be confounded by differential adherence or incorrect use of corticosteroids.ObjectivesTo determine if there are persistent phenotypic distinctions between SA (as defined by 2014 American Thoracic Society/European Respiratory Society guidelines) and NONSA after intramuscular triamcinolone acetonide (TA), and to identify predictors of a corticosteroid response in these populations.MethodsA total of 526 adults age 18 years and older (315 SA) and 188 children age 6 to less than 18 years (107 SA) in the NHLBI Severe Asthma Research Program III were characterized before and 3 weeks after TA. The primary outcome for corticosteroid response was defined as greater than or equal to 10-point improvement in percent predicted FEV1.Measurements and main resultsAdult asthma groups exhibited a small but significant mean FEV1% predicted improvement after TA (SA group mean difference, 3.4%; 95% confidence interval, 2.2-4.7%; P = 0.001), whereas children did not. Adult SA continued to manifest lower FEV1 and worse asthma control as compared with NONSA after TA. In children, after TA only prebronchodilator FEV1 distinguished SA from NONSA. A total of 21% of adults with SA and 20% of children with SA achieved greater than or equal to 10% improvement after TA. Baseline bronchodilator response and fractional exhaled nitric oxide had good sensitivity and specificity for predicting response in all groups except children with NONSA.ConclusionsOne in five patients with SA exhibit greater than or equal to 10% improvement in FEV1 with parenteral corticosteroid. Those likely to respond had greater bronchodilator responsiveness and fractional exhaled nitric oxide levels. In adults, differences in airflow obstruction and symptoms between SA and NONSA persist after parenteral corticosteroids, suggesting a component of corticosteroid nonresponsive pathobiology in adults with SA that may differ in children. Clinical trial registered with www.clinicaltrials.gov (NCT 01606826).

Viral illness with wheezing during infancy is associated with the inception of childhood asthma. Small airway dysfunction is a component of childhood asthma, but little is known about how viral illness at an early age may affect the structure and function of small airways. We used a well-characterized rat model of postbronchiolitis chronic airway dysfunction to address how postinfectious small airway lesions affect airway physiological function and if the structure/function correlates persist into maturity. Brown Norway rats were sham- or virus inoculated at 3 to 4 weeks of age and allowed to recover from the acute illness. At 3 to 14 months of age, physiology (respiratory system resistance, Newtonian resistance, tissue damping, and static lung volumes) was assessed in anesthetized, intubated rats. Serial lung sections revealed lesions in the terminal bronchioles that reduced luminal area and interrupted further branching, affecting 26% (range, 13–39%) of the small airways at 3 months of age and 22% (range, 6–40%) at 12 to 14 months of age. At 3 months of age (n = 29 virus; n = 7 sham), small airway lesions correlated with tissue damping (rs = 0.69) but not with Newtonian resistance (rs = 0.23), and Newtonian resistance was not elevated compared with control rats, indicating that distal airways were primarily responsible for the airflow obstruction. Older rats (n = 7 virus; n = 6 sham) had persistent small airway dysfunction and significantly increased Newtonian resistance in the postbronchiolitis group. We conclude that viral airway injury at an early age may induce small airway lesions that are associated quantitatively with small airway physiological dysfunction early on and that these defects persist into maturity.

Purpose To investigate the utility of hyperpolarized He-3 MRI for detecting regional lung ventilated volume (VV) changes in response to exercise challenge and leukotriene inhibitor montelukast, human subjects were recruited with Exercise Induced Bronchoconstriction (EIB), a condition described by airway constriction following exercise leading to reduced Forced Expiratory Volume in 1 second (FEV1) coinciding with ventilation defects on hyperpolarized He-3 MRI.

Reducing asthma exacerbation frequency is an important criterion for approval of asthma therapies, but the clinical features of exacerbation-prone asthma (EPA) remain incompletely defined.To describe the clinical, physiologic, inflammatory, and comorbidity factors associated with EPA.Baseline data from the NHLBI Severe Asthma Research Program (SARP)-3 were analyzed. An exacerbation was defined as a burst of systemic corticosteroids lasting 3 days or more. Patients were classified by their number of exacerbations in the past year: none, few (one to two), or exacerbation prone (≥3). Replication of a multivariable model was performed with data from the SARP-1 + 2 cohort.Of 709 subjects in the SARP-3 cohort, 294 (41%) had no exacerbations and 173 (24%) were exacerbation prone in the prior year. Several factors normally associated with severity (asthma duration, age, sex, race, and socioeconomic status) did not associate with exacerbation frequency in SARP-3; bronchodilator responsiveness also discriminated exacerbation proneness from asthma severity. In the SARP-3 multivariable model, blood eosinophils, body mass index, and bronchodilator responsiveness were positively associated with exacerbation frequency (rate ratios [95% confidence interval], 1.6 [1.2-2.1] for every log unit of eosinophils, 1.3 [1.1-1.4] for every 10 body mass index units, and 1.2 [1.1-1.4] for every 10% increase in bronchodilatory responsiveness). Chronic sinusitis and gastroesophageal reflux were also associated with exacerbation frequency (1.7 [1.4-2.1] and 1.6 [1.3-2.0]), even after adjustment for multiple factors. These effects were replicated in the SARP-1 + 2 multivariable model.EPA may be a distinct susceptibility phenotype with implications for the targeting of exacerbation prevention strategies. Clinical trial registered with www.clinicaltrials.gov (NCT 01760915).

Interstitial pulmonary fibrosis is caused by the excess production of extracellular matrix (ECM) by Fb in response to TGF-β1. Here, we show that the peptidyl-prolyl isomerase Pin1 modulates the production of many pro- and antifibrogenic cytokines and ECM. After acute, bleomycin injury, Pin1−/− mice showed reduced, pulmonary expression of collagens, tissue inhibitors of metalloproteinases, and fibrogenic cytokines but increased matrix metalloproteinases, compared with WT mice, despite similar levels of inflammation. In primary fibroblasts, Pin1 was required for TGF-β-induced phosphorylation, nuclear translocation, and transcriptional activity of Smad3. In Pin1−/− cells, inhibitory Smad6 was found in the cytoplasm rather than nucleus. Smad6 knockdown in Pin1−/− fibroblasts restored TGF-β-induced Smad3 activation, translocation, and target gene expression. Therefore, Pin1 is essential for normal Smad6 function and ECM production in response to injury or TGF-β and thus may be an attractive therapeutic target to prevent excess scarring in diverse lung diseases. Background: Interstitial pulmonary fibrosis is caused by the excess production of extracellular matrix (ECM) by Fb in response to TGF-β1. Results: The peptidyl-prolyl isomerase Pin1 modulates the production of many pro- and antifibrogenic cytokines and ECM after bleomycin injury. Conclusion: Pin1 controls Smad6 function. Significance: Pin1 may be a therapeutic target to prevent pathologic lung scarring.

The National Heart, Lung, and Blood Institute Severe Asthma Research Program (SARP) has characterized over the past 10 years 1,644 patients with asthma, including 583 individuals with severe asthma. SARP collaboration has led to a rapid recruitment of subjects and efficient sharing of samples among participating sites to conduct independent mechanistic investigations of severe asthma. Enrolled SARP subjects underwent detailed clinical, physiologic, genomic, and radiological evaluations. In addition, SARP investigators developed safe procedures for bronchoscopy in participants with asthma, including those with severe disease. SARP studies revealed that severe asthma is a heterogeneous disease with varying molecular, biochemical, and cellular inflammatory features and unique structure–function abnormalities. Priorities for future studies include recruitment of a larger number of subjects with severe asthma, including children, to allow further characterization of anatomic, physiologic, biochemical, and genetic factors related to severe disease in a longitudinal assessment to identify factors that modulate the natural history of severe asthma and provide mechanistic rationale for management strategies.

This article from the February 2014 issue of the European Respiratory Journal was originally published with errors in the criteria used to define severe asthma on page 350 and in table 3. At both aforementioned points in the article, the “poor symptom control” criterion for severe asthma should have been defined as: Asthma Control Questionnaire (ACQ) consistently 1.5 or Asthma Control Test (ACT) 1.5 or ACT 3 days each) in the previous year.

Ventilation defect percent (VDP) measured in asthmatics with hyperpolarized helium-3 MRI was more strongly associated with ED visits and hospitalizations due to asthma exacerbation than were conventional biomarkers of lung function and inflammation.

The purpose of this work is to detect dynamic gas trapping in three dimensions during forced exhalation at isotropic high spatial resolution and high temporal resolution using hyperpolarized helium-3 MRI. Ten subjects underwent hyperpolarized helium-3 MRI and multidetector CT. MRI was performed throughout inspiration, breath-hold, and forced expiration. A multiecho three-dimensional projection acquisition was used to improve data collection efficiency and an iterative constrained reconstruction was implemented to improve signal to noise ratio (SNR) and increase robustness to motion. Two radiologists evaluated the dynamic MRI and breath-held multidetector CT data for gas and air trapping, respectively. Phantom studies showed the proposed technique significantly improved depiction of moving objects compared to view-sharing methods. Gas trapping was detected using MRI in five of the six asthmatic subjects who displayed air trapping with multidetector CT. Locations in disagreement were found to represent small to moderate regions of air trapping. The proposed technique provides whole-lung three-dimensional imaging of respiration dynamics at high spatial and temporal resolution and compares well to the current standard, multidetector CT. While multidetector CT can provide information about static regional air trapping, it is unable to depict dynamics in a setting more comparable to a spirometry maneuver and explore the longitudinal time evolution of the trapped regions.

Sensitivity to the fungus Alternaria is associated with asthma persistence and severity. Current therapeutic options for treating Alternaria-induced airway inflammation are limited. In this study, Brown Norway rats are used to study the effectiveness of a DNA-based vaccine delivered to the airway in attenuating the response to a major Alternaria allergen, rAlt a 2. Compared to untreated sensitized animals, or animals receiving an "out-of-frame" DNA-based vaccine, animals treated with "in-frame" DNA vaccine showed an attenuation in specific IgE antibody titers to rAlt a 2, an increase in IgG(2b) (a Th1 response), a reduction in spontaneous IL-13 release by peribronchial lymph node cell suspensions, and an attenuation in the decrease in total lung capacity 72 h post-allergen challenge. Further, histopathologic examination of the lung tissues revealed reduced pulmonary inflammation post-allergen challenge in the DNA-vaccine-treated compared to sensitized, untreated animals. We conclude that a DNA-based vaccine delivered to the airway significantly influences the immunologic, pulmonary physiologic, and histological alterations induced by challenge with a major Alternaria allergen, rAlt a 2, in sensitized animals.

Summary A unique multi-center consortium of research centers, the severe asthma research program (SARP), is working to define asthma phenotypes, with a particular focus on severe asthma due to the higher prevalence of exacerbations and hospital visits in these patients. The consortium includes comprehensive studies of physiology, genotype, and inflammatory biomakers in addition to a lung imaging substudy in nearly 400 subjects. The imaging substudy is comparing quantitative computed tomography (CT) measures of airway morphology and parenchymal density to asthma severity and other makers of asthma. Results show increased wall thickness and increased regional air trapping in severe versus non-severe asthma. Image-guided bronchoscopic assessment using either CT or hyperpolarized gas magnetic resonance imaging (MRI) shows that highly diseased airways have increased wall thickness on histology and greater inflammatory cell numbers. Large scale imaging studies such as SARP may provide a means to better understand and guide effective treatment of severe asthma.

Rationale and Objectives Although multiple detector computed tomography (MDCT) and hyperpolarized gas magnetic resonance imaging (HP MRI) have demonstrated ability to detect structural and ventilation abnormalities in asthma, few studies have sought to exploit or cross-validate the regional information provided by these techniques. The purpose of this work is to assess regional disease in asthma by evaluating the association of sites of ventilation defect on HP MRI with other regional markers of airway disease, including air trapping on MDCT and inflammatory markers on bronchoscopy. Materials and Methods Both HP MRI using helium-3 and MDCT were acquired in the same patients. Supervised segmentation of the lung lobes on MRI and MDCT facilitated regional comparisons of ventilation abnormalities in the lung parenchyma. The percentage of spatial overlap was evaluated between regions of ventilation defect on HP MRI and hyperlucency on MDCT to determine associations between obstruction and likely regions of gas trapping. Similarly, lung lobes with high defect volume were compared to lobes with low defect volume for differences in inflammatory cell number and percentage using bronchoscopic assessment. Results There was significant overlap between sites of ventilation defect on HP MRI and hyperlucency on MDCT suggesting that sites of airway obstruction and air trapping are associated in asthma. The percent (r = 0.68; P = .0039) and absolute (r = 0.61; P = .0125) number of neutrophils on bronchoalveolar lavage for the sampled lung lobe also directly correlated with increased defect volume. Conclusions These results show promise for using image guidance to assess specific regions of ventilation defect or air trapping in heterogeneous obstructive lung diseases such as asthma.

Five to ten percent of asthma cases are poorly controlled chronically and refractory to treatment, and these severe cases account for disproportionate asthma-associated morbidity, mortality, and health care utilization. While persons with severe asthma tend to have more airway obstruction, it is not known whether they represent the severe tail of a unimodal asthma population, or a severe asthma phenotype. We hypothesized that severe asthma has a characteristic physiology of airway obstruction, and we evaluated spirometry, lung volumes, and reversibility during a stable interval in 287 severe and 382 nonsevere asthma subjects from the National Heart, Lung, and Blood Institute Severe Asthma Research Program. We partitioned airway obstruction into components of air trapping [indicated by forced vital capacity (FVC)] and airflow limitation [indicated by forced expiratory volume in 1 s (FEV1)/FVC]. Severe asthma had prominent air trapping, evident as reduced FVC over the entire range of FEV1/FVC. This pattern was confirmed with measures of residual lung volume/total lung capacity (TLC) in a subgroup. In contrast, nonsevere asthma did not exhibit prominent air trapping, even at FEV1/FVC 1 reversed similarly from baseline in severe and nonsevere asthma, but the severe asthma classification was an independent predictor of residual reduction in FEV1 after maximal bronchodilation. An increase in FVC accounted for most of the reversal of FEV1 when baseline FEV1 was

Introduction FEF25-75 is one of the standard results provided in spirometry reports; however, in adult asthmatics there is limited information on how this physiological measure relates to clinical or biological outcomes independently of the FEV1 or the FEV1/FVC ratio. Purpose To determine the association between Hankinson’s percent-predicted FEF25-75 (FEF25-75%) levels with changes in healthcare utilization, respiratory symptom frequency, and biomarkers of distal airway inflammation. Methods In participants enrolled in the Severe Asthma Research Program 1–2, we compared outcomes across FEF25-75% quartiles. Multivariable analyses were done to avoid confounding by demographic characteristics, FEV1, and the FEV1/FVC ratio. In a sensitivity analysis, we also compared outcomes across participants with FEF25-75% below the lower limit of normal (LLN) and FEV1/FVC above LLN. Results Subjects in the lowest FEF25-75% quartile had greater rates of healthcare utilization and higher exhaled nitric oxide and sputum eosinophils. In multivariable analysis, being in the lowest FEF25-75% quartile remained significantly associated with nocturnal symptoms (OR 3.0 [95%CI 1.3–6.9]), persistent symptoms (OR 3.3 [95%CI 1–11], ICU admission for asthma (3.7 [1.3–10.8]) and blood eosinophil % (0.18 [0.07, 0.29]). In the sensitivity analysis, those with FEF25-75%

Viral infections are closely linked to wheezing in infancy, and those children with recurrent virus-induced wheezing episodes are at great risk for chronic childhood asthma. Infancy is a time of increased susceptibility to viral infections, and this stage is also characterized by pulmonary alveolar multiplication and extensive remodeling of the airways to accommodate growth. This coincidence, together with the observation that children with asthma can have structural lung changes and functional deficits at an early age, suggests that viral infections could adversely affect lung development. Inflammatory mediators induced by viral infection are known to have effects on the remodeling process, suggesting a plausible mechanism to support this theory. Furthermore, animal models of viral infection during lung growth and development suggest that developmental factors are important in determining the consequences of infection on long-term lung function. Greater understanding of the effects of viral infections on lung development and growth in early childhood might lead to the discovery of additional strategies for the prevention of recurrent wheezing and chronic asthma.

Magnetic resonance (MR) and positron emission tomography (PET) imaging techniques were coregistered to demonstrate regional ventilation and inflammation in the lung for in vivo, noninvasive evaluation of regional lung function associated with allergic inflammation. Four Brown Norway rats were imaged pre- and post segmental allergen challenge using respiratory-gated He-3 magnetic resonance imaging (MRI) to visualize ventilation, T1-weighted proton MRI to depict inflammatory infiltrate, and [F-18]fluorodeoxyglucose-PET to detect regional glucose metabolism by inflammatory cells. Segmental allergen challenges were delivered and the pre- and postchallenge lung as well as the contralateral lung were compared. Coregistration of the imaging results demonstrated that regions of ventilation defects, inflammatory infiltrate, and increased glucose metabolism correlated well with the site of allergen challenge delivery and inflammatory cell recruitment, as confirmed by histology. This method demonstrates that fusion of functional and anatomic PET and MRI image data may be useful to elucidate the functional correlates of inflammatory processes in the lungs. Magn Reson Med 53:1243–1250, 2005. © 2005 Wiley-Liss, Inc.

We describe a reversed-phase assay of hydroxyproline in rat lung tissue using sarcosine for the internal standard and pre-injection reaction with both o-phthalaldehyde (OPA) and 9-fluorenylmethylchloroformate (FMOC). Intra-assay variability in the concentration range of 25-500 microM hydroxyproline was less than 1%. Normal rat (left) lung was found to have a hydroxyproline content of 1.08+/-0.18 mg/lung. This ability to measure minute amounts of hydroxyproline is being applied to the measure of collagen and pathological fibrosis.

Viral respiratory infections cause acute bronchiolitis and physiologic dysfunction in human infants and in animals. It is possible that the pulmonary dysfunction is a consequence of the inflammatory cells that are recruited during viral illness. We hypothesized that blockade of intercellular adhesion molecule-1 (ICAM-1), a major cell adhesion molecule, would impede the ingress of leukocytes during viral infection and attenuate virus-induced pulmonary dysfunction. Adult male rats were inoculated with parainfluenza type 1 (Sendai) virus or sterile vehicle, and treated with blocking or nonblocking MAb specific for rat ICAM-1. Respiratory system resistance, oxygenation (PaO2), methacholine responsiveness, and bronchoalveolar lavage (BAL) leukocyte counts were measured in anesthetized, paralyzed, ventilated rats. Treatment with the blocking ICAM-1 antibody reduced virus-induced increases in BAL neutrophils and lymphocytes by 70% (p < 0.001), but did not affect BAL monocytes/macrophages. Peripheral blood leukocyte counts were elevated in anti-ICAM-1 blocking antibody-treated rats (p = 0.0003). Although virus-induced increases in resistance and decreases in PaO2 were not affected by anti-ICAM-1 treatment, there was a small but significant attenuation of virus-induced methacholine hyperresponsiveness (p = 0.02). We conclude that ICAM-1 has an important role in neutrophil and lymphocyte infiltration during respiratory viral illness, and that virus-induced changes in pulmonary physiology are not related directly to the numbers of neutrophils and lymphocytes that migrate to the air spaces during infection.

Bronchoalveolar lavage (BAL) is a well-characterized technique for analysis of cellular constituents of the airways and air spaces, but whole lung lavage requires that the animal be euthanized. We describe a technique of segmental BAL in rats that allows serial measurements of inflammation. A tracheal tube was placed, under direct visualization, in lightly anesthetized animals, and a catheter was passed through the tracheal tube and advanced to a wedge position. Five 0.1-ml volumes of buffer solution were instilled and then withdrawn with gentle suction. In normal rats, the percentages of neutrophils, eosinophils, and mononuclear cells had a high level of agreement in the segmental samples compared with those obtained subsequently by whole lung lavage. In rats with acute pulmonary inflammation, the differential leukocyte counts from segmental samples exhibited patterns of change that differed from those of whole lung lavage; however, most segmental samples were obtained from the left lung base so that regional variability could be minimized in serial studies. Lung mechanics and airway inflammation were not affected by repeated segmental BALs done 2 wk apart.

Respiratory viral infections have been associated with airway obstruction and hyperresponsiveness, and exacerbations of asthma. Although virus-induced asthma is thought to be precipitated by airway inflammation, the clinical efficacy and rationale for using antiinflammatory treatment during such exacerbations remains controversial. The purpose of this study was to use a well characterized animal model of respiratory viral illness to test the hypothesis that the inflammatory response to viral infection is responsible for the development of airway dysfunction. Adult rats were inoculated with either Sendai virus or sterile vehicle and treated with daily injections of dexamethasone or saline. At postinoculation d 4, 5, or 6, rats were evaluated for airway obstruction, hyperresponsivenes, inflammation, and lung viral titers. Saline-treated infected rats had significant airway obstruction (increased resistance, decreased dynamic compliance), hyperresponsiveness (i.v. methacholine), and inflammation (increased bronchoalveolar lavage leukocytes) compared with noninfected controls. In contrast, dexamethasone-treated infected rats had no increase in bronchoalveolar lavage leukocytes and significantly smaller changes in airway physiology, but had increased lung viral titers compared with saline-treated infected rats. We conclude that glucocorticoid suppression of the inflammatory response to respiratory viral infection largely prevents virus-associated airway dysfunction.

Rationale: Air trapping and ventilation defects on imaging are characteristics of asthma. Airway wall thickening occurs in asthma and is associated with increased bronchial vascularity and vascular permeability. Vascular endothelial cell products have not been explored as a surrogate to mark structural airway changes in asthma. Objectives: Determine whether reporters of vascular endothelial cell perturbation correlate with airway imaging metrics in patients with asthma of varying severity. Methods: Plasma from Severe Asthma Research Program subjects was analyzed by ELISAs for soluble von Willebrand factor mature protein (VWF:Ag) and propeptide (VWFpp), P-selectin, and platelet factor 4. Additional subjects were analyzed over 48 hours after whole-lung antigen challenge. We calculated ventilation defect volume by hyperpolarized helium-3 magnetic resonance imaging and areas of low signal density by multidetector computed tomography (less than −856 Hounsfield units [HU] at functional residual capacity and −950 HU at total lung capacity [TLC]). Measurements and Main Results: VWFpp and VWFpp/Ag ratio correlated with and predicted greater percentage defect volume on hyperpolarized helium-3 magnetic resonance imaging. P-selectin correlated with and predicted greater area of low density on chest multidetector computed tomography less than −950 HU at TLC. Platelet factor 4 did not correlate. Following whole-lung antigen challenge, variation in VWFpp, VWFpp/Ag, and P-selectin among time-points was less than that among subjects, indicating stability and repeatability of the measurements. Conclusions: Plasma VWFpp and P-selectin may be useful as surrogates of functional and structural defects that are evident on imaging. The results raise important questions about why VWFpp and P-selectin are associated specifically with different imaging abnormalities.

Respiratory viral infections have been associated with exacerbations of asthma in humans, and are known to produce airway obstruction and hyperresponsiveness in rats. Virus-induced airway dysfunction may result in part from inflammatory cells and their products, and agents that target these mechanisms might therefore attenuate viral airway injury. The 21-aminosteroid class of drugs has been reported to attenuate tissue injury in a variety of models, and we hypothesized that U-83836E, an orally-active aminosteroid, would prevent the development of airway dysfunction during acute viral illness. Adult rats were inoculated with either parainfluenza type 1 (Sendai) virus or sterile vehicle, treated with either U-83836E 20 mg/kg or water by oral gavage twice daily, and studied on postinoculation day 5, 6 or 7. Anesthetized, paralysed, mechanically ventilated rats were placed in a body plethysmograph for measurements of airway obstruction (resistance, dynamic compliance, eucapneic PaO2), and responsiveness to i.v. methacholine; lungs were lavaged to obtain inflammatory cells. The water-treated virus group was significantly different from the non-infected controls for all variables. Virus-induced hyperresponsiveness was attenuated (P = 0.027) by aminosteroid treatment, although airway obstruction and inflammation were not improved by the treatment. We conclude that 21-aminosteroids may protect airways from virus-induced hyperresponsiveness.

Studies with isolated cells are important to the understanding of mechanisms by which eosinophils participate in allergic inflammation. Due to species variability, isolation techniques and cell biology need to be defined for each source. We developed methods to obtain rat eosinophils with purity and viability exceeding 90%, characterized the superoxide anion production of these cells in response to standard activators, and compared these results with those previously obtained in our laboratories with the use of human eosinophils. Rat eosinophils responded vigorously to phorbol myristate acetate and poorly to platelet-activating factor and to N-formyl-methionyl-leucyl-phenylalanine, parallel to the responses of human eosinophils. In contrast, rat eosinophils responded unlike human eosinophils to other activators, having a larger response to calcium ionophore A23187, a smaller response to serum-treated or serum-opsonized zymosan, and a negative rather than positive modulatory effect of cytochalasin B. We conclude that rat eosinophils can be obtained in high purity and with intact responsiveness to a number of different activators.

Background Coagulation Factor XIII (FXIII) plays an important role in wound healing by stabilizing fibrin clots and cross-linking extracellular matrix proteins. FXIII is expressed in cells of the monocyte/macrophage and dendritic cell lineages in response to type 2 cytokines. Objective We sought to determine the association between FXIII and asthma pathobiology. Methods We analyzed the expression of FXIII mRNA and protein levels in bronchoalveolar lavage samples obtained before and after segmental allergen challenge from patients with mild asthma and in induced sputum samples collected from patients with mild-to-moderate and severe asthma. Results FXIII mRNA and protein levels were highly upregulated in bronchoalveolar cells and fluid after allergen challenge and mRNA levels correlated with protein levels. In sputum of asthmatic patients, FXIII expression was positively correlated with type 2 immune response and dendritic cell markers (CD209 and CD207). FXIII expression was also associated with increased airflow limitation (FEV 1 /forced vital capacity and residual volume/total lung capacity ratios) and greater reversibility to β-agonists. Conclusions FXIII expression was upregulated in the airways of asthmatic patients after allergen exposure. Expression in the sputum of asthmatic patients correlated with the type 2 immune response and airflow limitation. Excessive activity of FXIII could contribute to the pathophysiology of airway obstruction in asthmatic patients.