Exploring fibroblast interactions on nanocrystalline surfaces in physiological environments through a phenomenological lens.

The cytological behaviour and functional dynamics (adhesion, spreading, synthesis of proteins) of fibroblasts when interacting with biomedical surfaces are intricately influenced by the inherent nature of surface (nanocrystalline or microcrystalline), where the nanocrystalline (NC) surface is preferred in relation to the microcrystalline (MC) surface. This preference is a direct consequence of the distinct differences in physical and chemical characteristics between NC and MC surfaces, which include crystal boundary bio-physical attributes, electron work function, surface energy, and charge carrier density. The observed variances in cytological behaviour at the interfaces of NC and MC bio-surfaces can be attributed to these fundamental differences, particularly accounting for the percentage and nature of crystal boundaries. Recognising and understanding these physical and chemical characteristics establish the groundwork for formulating precise guidelines crucial in the development of the forthcoming generation of biomedical devices.

The significance of nanoscale surface in favourably modulating the cellular functionality is described with the aim to provide the solution to the current day challenges in the biomedical arena. Furthermore, the perspective presented advances the nano-bio science forward by implying that the nanoscale structure induces chemical and physical changes that can be considered responsible for favourable modulation of cellular activity in the living organism.

ANKRD1 expression is aberrantly upregulated in the mdm mouse model of muscular dystrophy and induced by stretch through NFκB.

The muscular dystrophy with myositis (mdm) mouse model results in a severe muscular dystrophy due to an 83-amino-acid deletion in the N2A region of titin, an expanded sarcomeric protein that functions as a molecular spring which senses and modulates the response to mechanical forces in cardiac and skeletal muscles. ANKRD1 is one of the muscle ankyrin repeat domain proteins (MARPs) a family of titin-associated, stress-response molecules and putative transducers of stretch-induced signaling in skeletal muscle. The aberrant over-activation of Nuclear factor Kappa B (NF-κB) and the Ankyrin-repeat domain containing protein 1 (ANKRD1) occurs in several models of progressive muscle disease including Duchenne muscular dystrophy. We hypothesized that mechanical regulation of ANKRD1 is mediated by NF-κB activation in skeletal muscles and that this mechanism is perturbed by small deletion of the stretch-sensing titin N2A region in the mdm mouse. We applied static mechanical stretch of the mdm mouse diaphragm and cyclic mechanical stretch of C2C12 myotubes to examine the interaction between NF-κΒ and ANKRD1 expression utilizing Western blot and qRTPCR. As seen in skeletal muscles of other severe muscular dystrophies, an aberrant increased basal expression of NF-κB and ANKRD1 were observed in the diaphragm muscles of the mdm mice. Our data show that in the mdm diaphragm, basal levels of NF-κB are increased, and pharmacological inhibition of NF-κB does not alter basal levels of ANKRD1. Alternatively, NF-κB inhibition did alter stretch-induced ANKRD1 upregulation. These data show that NF-κB activity is at least partially responsible for the stretch-induced expression of ANKRD1.

Stretching muscle cells induces transcriptional and splicing transitions and changes in SR proteins.

Alternative splicing is an RNA processing mechanism involved in skeletal muscle development and pathology. Muscular diseases exhibit splicing alterations and changes in mechanobiology leading us to investigate the interconnection between mechanical forces and RNA processing. We performed deep RNA-sequencing after stretching muscle cells. First, we uncovered transcriptional changes in genes encoding proteins involved in muscle function and transcription. Second, we observed that numerous mechanosensitive genes were part of the MAPK pathway which was activated in response to stretching. Third, we revealed that stretching skeletal muscle cells increased the proportion of alternatively spliced cassette exons and their inclusion. Fourth, we demonstrated that the serine and arginine-rich proteins exhibited stronger transcriptional changes than other RNA-binding proteins and that SRSF4 phosphorylation is mechanosensitive. Identifying SRSF4 as a mechanosensitive RNA-binding protein that might contribute to crosstalk between mechanotransduction, transcription, and splicing could potentially reveal novel insights into muscular diseases, particularly those with unknown etiologies.

Predicting COPD Progression in Current and Former Smokers Using a Joint Model for Forced Expiratory Volume in 1 Second and Forced Expiratory Volume in 1 Second to Forced Vital Capacity Ratio.

Understanding baseline characteristics that can predict the progression of lung disease such as chronic obstructive pulmonary disease (COPD) for current or former smokers may allow for therapeutic intervention, particularly for individuals at high risk of rapid disease progression or transition from non-COPD to COPD. Classic diagnostic criteria for COPD and disease severity such as the Global Initiative for Chronic Obstructive Lung Disease document are based on forced expiratory volume in 1 second (FEV1) and FEV1 to forced vital capacity (FVC) ratio. Modeling changes in these outcomes jointly is beneficial given that they are correlated, and they are both required for specific disease classifications. Here, linear mixed models were used to model changes in FEV1 and FEV1/FVC jointly for 5- and 10-year intervals, using important baseline predictors to better understand the factors that affect disease progression. Participants with predicted loss of FEV1 and/or FEV1/FVC of at least 5% tended to have more emphysema, higher functional residual capacity, higher airway wall thickness as measured by Pi10, lower FVC to total lung capacity ratio and a lower body mass index at baseline, all relative to overall cohort averages. The model developed can be used to predict progression for any potential COPD individual, based on demographic, symptom, computed tomography, and comorbidity variables.

A theoretical framework for mechanics of diaphragm.

A theoretical framework is developed for mechanics of the diaphragm. The diaphragm is modeled as an anisotropic elastic material surface with activation functionality. A constitutive function is formulated that relates the stresses in the diaphragm to the surface deformation gradient, the anisotropy vector, and the muscle activation parameter. The equilibrium equations for the diaphragm are derived to determine the deformed shape of the diaphragm in the process of respiration with the associated transdiaphragmatic pressures. A numerical solution is presented, that demonstrates the capability of the model to recover the experimental observations and to predict the shape and stresses of the diaphragm.

Mechanics of dystrophin deficient skeletal muscles in very young mice and effects of age.

The MDX mouse is an animal model of Duchenne muscular dystrophy, a human disease marked by an absence of the cytoskeletal protein, dystrophin. We hypothesized that 1) dystrophin serves a complex mechanical role in skeletal muscles by contributing to passive compliance, viscoelastic properties, and contractile force production and 2) age is a modulator of passive mechanics of skeletal muscles of the MDX mouse. Using an in vitro biaxial mechanical testing apparatus, we measured passive length-tension relationships in the muscle fiber direction as well as transverse to the fibers, viscoelastic stress-relaxation curves, and isometric contractile properties. To avoid confounding secondary effects of muscle necrosis, inflammation, and fibrosis, we used very young 3-wk-old mice whose muscles reflected the prefibrotic and prenecrotic state. Compared with controls, 1) muscle extensibility and compliance were greater in both along fiber direction and transverse to fiber direction in MDX mice and 2) the relaxed elastic modulus was greater in dystrophin-deficient diaphragms. Furthermore, isometric contractile muscle stress was reduced in the presence and absence of transverse fiber passive stress. We also examined the effect of age on the diaphragm length-tension relationships and found that diaphragm muscles from 9-mo-old MDX mice were significantly less compliant and less extensible than those of muscles from very young MDX mice. Our data suggest that the age of the MDX mouse is a determinant of the passive mechanics of the diaphragm; in the prefibrotic/prenecrotic stage, muscle extensibility and compliance, as well as viscoelasticity, and muscle contractility are altered by loss of dystrophin.

A Risk Prediction Model for Mortality Among Smokers in the COPDGene® Study.

BACKGROUND: Risk factor identification is a proven strategy in advancing treatments and preventive therapy for many chronic conditions. Quantifying the impact of those risk factors on health outcomes can consolidate and focus efforts on individuals with specific high-risk profiles. Using multiple risk factors and longitudinal outcomes in 2 independent cohorts, we developed and validated a risk score model to predict mortality in current and former cigarette smokers. METHODS: We obtained extensive data on current and former smokers from the COPD Genetic Epidemiology (COPDGene®) study at enrollment. Based on physician input and model goodness-of-fit measures, a subset of variables was selected to fit final Weibull survival models separately for men and women. Coefficients and predictors were translated into a point system, allowing for easy computation of mortality risk scores and probabilities. We then used the SubPopulations and InteRmediate Outcome Measures In COPD Study (SPIROMICS) cohort for external validation of our model. RESULTS: Of 9867 COPDGene participants with standard baseline data, 17.6% died over 10 years of follow-up, and 9074 of these participants had the full set of baseline predictors (standard plus 6-minute walk distance and computed tomography variables) available for full model fits. The average age of participants in the cohort was 60 for both men and women, and the average predicted 10-year mortality risk was 18% for women and 25% for men. Model time-integrated area under the receiver operating characteristic curve statistics demonstrated good predictive model accuracy (0.797 average), validated in the external cohort (0.756 average). Risk of mortality was impacted most by 6-minute walk distance, forced expiratory volume in 1 second and age, for both men and women. CONCLUSIONS: Current and former smokers exhibited a wide range of mortality risk over a 10- year period. Our models can identify higher risk individuals who can be targeted for interventions to reduce risk of mortality, for participants with or without chronic obstructive pulmonary disease (COPD) using current Global initiative for obstructive Lung Disease (GOLD) criteria.

SIRT1 Regulation in Ageing and Obesity.

Ageing and obesity have common hallmarks: altered glucose and lipid metabolism, chronic inflammation and oxidative stress are some examples. The downstream effects of SIRT1 activity have been thoroughly explored, and their research is still in expanse. SIRT1 activation has been shown to regulate pathways with beneficiary effects on 1) ageing and obesity-associated metabolic disorders such as metabolic syndrome, insulin resistance and type-II diabetes with, 2) chronic inflammatory processes such as arthritis, atherosclerosis and emphysema, 3) DNA damage and oxidative stress with impact on neurodegenerative diseases, cardiovascular health and some cancers. This knowledge intensified the interest in uncovering the mechanisms regulating the expression and activity of SIRT1. This review focuses on the upstream regulatory mechanisms controlling SIRT1, and how this knowledge could potentially contribute to the development of therapeutic interventions.

COPDGene® 2019: Redefining the Diagnosis of Chronic Obstructive Pulmonary Disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) remains a major cause of morbidity and mortality. Present-day diagnostic criteria are largely based solely on spirometric criteria. Accumulating evidence has identified a substantial number of individuals without spirometric evidence of COPD who suffer from respiratory symptoms and/or increased morbidity and mortality. There is a clear need for an expanded definition of COPD that is linked to physiologic, structural (computed tomography [CT]) and clinical evidence of disease. Using data from the COPD Genetic Epidemiology study (COPDGene®), we hypothesized that an integrated approach that includes environmental exposure, clinical symptoms, chest CT imaging and spirometry better defines disease and captures the likelihood of progression of respiratory obstruction and mortality. METHODS: Four key disease characteristics - environmental exposure (cigarette smoking), clinical symptoms (dyspnea and/or chronic bronchitis), chest CT imaging abnormalities (emphysema, gas trapping and/or airway wall thickening), and abnormal spirometry - were evaluated in a group of 8784 current and former smokers who were participants in COPDGene® Phase 1. Using these 4 disease characteristics, 8 categories of participants were identified and evaluated for odds of spirometric disease progression (FEV1 > 350 ml loss over 5 years), and the hazard ratio for all-cause mortality was examined. RESULTS: Using smokers without symptoms, CT imaging abnormalities or airflow obstruction as the reference population, individuals were classified as Possible COPD, Probable COPD and Definite COPD. Current Global initiative for obstructive Lung Disease (GOLD) criteria would diagnose 4062 (46%) of the 8784 study participants with COPD. The proposed COPDGene® 2019 diagnostic criteria would add an additional 3144 participants. Under the new criteria, 82% of the 8784 study participants would be diagnosed with Possible, Probable or Definite COPD. These COPD groups showed increased risk of disease progression and mortality. Mortality increased in patients as the number of their COPD characteristics increased, with a maximum hazard ratio for all cause-mortality of 5.18 (95% confidence interval [CI]: 4.15-6.48) in those with all 4 disease characteristics. CONCLUSIONS: A substantial portion of smokers with respiratory symptoms and imaging abnormalities do not manifest spirometric obstruction as defined by population normals. These individuals are at significant risk of death and spirometric disease progression. We propose to redefine the diagnosis of COPD through an integrated approach using environmental exposure, clinical symptoms, CT imaging and spirometric criteria. These expanded criteria offer the potential to stimulate both current and future interventions that could slow or halt disease progression in patients before disability or irreversible lung structural changes develop.

Pectoralis muscle area and mortality in smokers without airflow obstruction.

BACKGROUND: Low muscle mass is associated with increased mortality in the general population but its prognostic value in at-risk smokers, those without expiratory airflow obstruction, is unknown. We aimed to test the hypothesis that reduced muscle mass is associated with increased mortality in at-risk smokers. METHODS: Measures of both pectoralis and paravertebral erector spinae muscle cross-sectional area (PMA and PVMA, respectively) as well as emphysema on chest computed tomography (CT) scans were performed in 3705 current and former at-risk smokers (≥10 pack-years) aged 45-80 years enrolled into the COPDGene Study between 2008 and 2013. Vital status was ascertained through death certificate. The association between low muscle mass and mortality was assessed using Cox regression analysis. RESULTS: During a median of 6.5 years of follow-up, 212 (5.7%) at-risk smokers died. At-risk smokers in the lowest (vs. highest) sex-specific quartile of PMA but not PVMA had 84% higher risk of death in adjusted models for demographics, smoking, dyspnea, comorbidities, exercise capacity, lung function, emphysema on CT, and coronary artery calcium content (hazard ratio [HR] 1.85 95% Confidence interval [1.14-3.00] P = 0.01). Results were consistent when the PMA index (PMA/height2) was used instead of quartiles. The association between PMA and death was modified by smoking status (P = 0.04). Current smokers had a significantly increased risk of death (lowest vs. highest PMA quartile, HR 2.25 [1.25-4.03] P = 0.007) while former smokers did not. CONCLUSIONS: Low muscle mass as measured on chest CT scans is associated with increased mortality in current smokers without airflow obstruction. TRIAL REGISTRATION: NCT00608764.

Examining the Effects of Age on Health Outcomes of Chronic Obstructive Pulmonary Disease: Results From the Genetic Epidemiology of Chronic Obstructive Pulmonary Disease Study and Evaluation of Chronic Obstructive Pulmonary Disease Longitudinally to Identify Predictive Surrogate Endpoints Cohorts.

RATIONALE: The prevalence of chronic obstructive pulmonary disease (COPD) and its associated comorbidities increase with age. However, little is understood about differences in the disease in patients over 65 years of age compared with younger patients. OBJECTIVES: To determine disease characteristics of COPD and its impact in older patients compared with younger patients. METHODS: We examined baseline characteristics of patients with COPD (global obstructive lung disease stage II-IV) in 2 large cohorts: Genetic Epidemiology of COPD Study (COPDGene) and Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE). We compared demographics, indices of disease severity, prevalence of comorbidities, exacerbation frequency, and quality of life scores in patients ≥65 years of age vs patients <65 years of age. We also tested for associations of age with disease characteristics and health outcomes. RESULTS: In the COPDGene cohort, older patients (n = 1663) had more severe disease as measured by forced expiratory volume in 1 second (1.22 vs 1.52 L, P < .001), use of long-term oxygen therapy (35% vs 22%, P < .001), 6-minute walk distance (355 vs 375 m, P < .001), and radiographic evidence of emphysema (14% vs 8%, P < .001) and air trapping (47% vs 36%, P < .001) and were more likely to have comorbidities compared with younger patients (n = 2027). Similarly, in the ECLIPSE cohort, older patients (n = 1030) had lower forced expiratory volume in 1 second (1.22 vs 1.34 L, P < .001), greater use of long-term oxygen therapy (7% vs 5%, P = .02), shorter 6- minute walk distance (360 vs 389 m, P < .001), and more radiographic evidence of emphysema (17% vs 14%, P = .009) than younger patients (n = 1131). In adjusted analyses of both cohorts, older age was associated with decreased frequency of exacerbations [odds ratio = 0.52, 95% confidence interval (CI) = 0.43-0.64 in COPDGene, odds ratio = 0.79, 95% CI = 0.64-0.99 in ECLIPSE] and a better quality of life (lower St. Georges respiratory questionnaire score) (ß = -8.7, 95% CI = -10.0 to -7.4 in COPDGene, ß = -4.4, 95% CI = -6.1 to -3.2 in ECLIPSE). CONCLUSIONS: Despite greater severity of illness, older patients with COPD had better quality of life and reported fewer exacerbations than younger patients. Although this observation needs to be explored further, it may be related to the fact that older patients change their expectations and learn to adapt to their disease.

Anisotropic mechanosensitive pathways in the diaphragm and their implications in muscular dystrophies.

The diaphragm is the "respiratory pump;" the muscle that generates pressure to allow ventilation. Diaphragm muscles play a vital function and thus are subjected to continuous mechanical loading. One of its peculiarities is the ability to generate distinct mechanical and biochemical responses depending on the direction through which the mechanical forces applied to it. Contractile forces originated from its contractile components are transmitted to other structural components of its muscle fibers and the surrounding connective tissue. The anisotropic mechanical properties of the diaphragm are translated into biochemical signals that are directionally mechanosensitive by mechanisms that appear to be unique to this muscle. Here, we reviewed the current state of knowledge on the biochemical pathways regulated by mechanical signals emphasizing their anisotropic behavior in the normal diaphragm and analyzed how they are affected in muscular dystrophies.

Obesity modulates diaphragm curvature in subjects with and without COPD.

Obesity is a common comorbidity of chronic obstructive pulmonary disease (COPD) and has been associated with worse outcomes. However, it is unknown whether the interaction between obesity and COPD modulates diaphragm shape and consequently its function. The body mass index (BMI) has been used as a correlate of obesity. We tested the hypothesis that the shape of the diaphragm muscle and size of the ring of its insertion in non-COPD and COPD subjects are modulated by BMI. We recruited 48 COPD patients with postbronchiodilator forced expiratory volume in 1 s (FEV1)-to-forced vital capacity (FVC) < 0.7 and 29 age-matched smoker/exsmoker control (non-COPD) subjects, who underwent chest computed tomography (CT) at lung volumes ranging from functional residual capacity (FRC) to total lung capacity (TLC). We then computed maximum principal diaphragm curvature in the midcostal region of the left hemidiaphragm at the end of inspiration during quiet breathing (EI) and at TLC. The radius of maximum curvature of diaphragm muscle increased with BMI in both COPD and non-COPD subjects. The size of diaphragm ring of insertion on the chest wall also increased significantly with increasing BMI. Surprisingly, COPD severity did not appear to cause significant alteration in diaphragm shape except in normal-weight subjects at TLC. Our data uncovered important factors such as BMI, the size of the diaphragm ring of insertion, and disease severity that modulate the structure of the ventilatory pump in non-COPD and COPD subjects.

MicroRNA-434-3p regulates age-related apoptosis through eIF5A1 in the skeletal muscle.

Increased activation of catabolic pathways, including apoptosis causes sarcopenia. However, the precise molecular mechanism that initiates apoptosis during aging is not well understood. Here, we report that aging alters miRNA expression profile in mouse skeletal muscle as evidenced by miRNA microarray and real-time PCR. We identified miR-434-3p as a highly downregulated miRNA in the skeletal muscle of aging mice. Myocytes transfected with miR-434-3p mimic prevents apoptosis induced by various apoptotic stimuli, and co-transfection of miR-434-3p antagomir abolishes the inhibitory role of miR-434-3p. We found that miR-434-3p inhibits apoptosis by targeting the eukaryotic translation initiation factor 5A1 (eIF5A1). Overexpression of miR-434-3p in myocytes reduces the loss of mitochondrial transmembrane potential, and activation of caspases-3, -8 and -9 by suppressing eIF5A1 in response to various apoptotic stimuli whereas inhibition of miR-434-3p reversed this scenario. Skeletal muscles from aging mice exhibit low levels of miR-434-3p and high levels of eIF5A1, suggesting a possible role for miR-434-3p in the initiation of apoptosis in aging muscle. Overall, our data identified for the first time that miR-434-3p is an anti-apoptotic miRNA that may be therapeutically useful for treating muscle atrophy in various pathophysiological conditions, including sarcopenia.

Regional diaphragm volume displacement is heterogeneous in dogs.

Muscle shortening and volume displacement (VD) are critical determinants of the pressure-generating capacity of the diaphragm. The present study was designed to test the hypothesis that diaphragm VD is heterogeneous and that distribution of VD is dependent on regional muscle shortening, posture, and the level of muscle activation. Radioopaque markers were sutured along muscle bundles of the peritoneal surface of the crural, dorsal costal, midcostal, and ventral costal regions of the left hemidiaphragm in four dogs. The markers were followed by biplanar video fluoroscopy during quiet spontaneous breathing, passive inflation to total lung capacity (TLC), and inspiratory efforts against an occluded airway at three lung volumes spanning the vital capacity [functional residual capacity, functional residual capacity + ½ inspiratory capacity, and TLC in both the prone and supine postures]. Our data show the ventral costal diaphragm had the largest VD and contributed nearly two times to the total diaphragm VD compared with the dorsal costal portion. In addition, the ventral costal diaphragm contributed nearly half of the total VD in the prone position, whereas it only contributed a quarter of the total VD in the supine postition. During efforts against an occluded airway and during passive inflation to TLC in the supine position, the crural diaphragm displaced volume equivalent to that of the midcostal portion. Regional muscle shortening closely matched regional VD. We conclude that the primary force generator of the diaphragm is primarily dominated by the contribution of the ventral costal region to its VD.

Obesity Is Associated With Increased Morbidity in Moderate to Severe COPD.

BACKGROUND: Obesity is prevalent in the United States; however, the impact of obesity on COPD morbidity is unclear. We hypothesized that obesity is associated with worse outcomes in COPD. METHODS: We examined 3,631 participants from the multicenter prospective cohort study Genetic Epidemiology of COPD (COPDGene) who had spirometry-confirmed COPD, a postbronchodilator FEV1 < 80% predicted, and a BMI ≥ 18.5 kg/m2. We conducted logistic and linear regression analyses to determine the association between COPD outcomes and obesity class, adjusting for relevant confounders. The referent for obesity classes included normal/overweight individuals (BMI range, 18.5-29.9 kg/m2). RESULTS: Overall, 35% of participants were obese, with 21% class I (BMI range, 30-34.9 kg/m2), 9% class II (BMI range, 35-39.9 kg/m2), and 5% class III (BMI ≥ 40 kg/m2). The number of comorbidities increased with increasing obesity class (P < .001). Increasing obesity class was independently associated with worse respiratory-specific and general quality of life (QOL) (St. George's Respiratory Questionnaire score and Short Form-36 score version 2, respectively), reduced 6-min walk distance (6MWD), increased dyspnea (Modified Medical Research Council score ≥ 2), and greater odds of severe acute exacerbation of COPD (AECOPD). The associations between obesity and worse outcomes were independent of the presence of comorbidities, except in the case of SF-36 and severe exacerbations. CONCLUSIONS: Obesity is prevalent among individuals with COPD and associated with worse COPD-related outcomes, ranging from QOL and dyspnea to 6MWD and severe AECOPD. These associations were strengthened when obesity was analyzed as a dose-dependent response. Obesity in patients with COPD may contribute to a worse COPD-related course.

Persistent and Newly Developed Chronic Bronchitis Are Associated with Worse Outcomes in Chronic Obstructive Pulmonary Disease.

RATIONALE: Chronic bronchitis is, by definition, a chronic condition, but the development and remission of this condition in cigarette smokers with or without chronic obstructive pulmonary disease (COPD) are poorly understood. Also, it is unclear how the persistence or new development of chronic bronchitis affects symptoms and outcomes. OBJECTIVES: To ascertain the relationship between smoking status and the presence or absence of chronic bronchitis and the subsequent effects on symptoms and outcomes. METHODS: We analyzed 1,775 current or ex-smokers with GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage 0-IV COPD in phase 2 of the Genetic Epidemiology of COPD (COPDGene) Study, which included subjects after 5 years of follow-up from phase 1. We asked subjects at enrollment and at 5 years of follow-up about symptoms consistent with chronic bronchitis. We divided subjects into four groups: persistent chronic bronchitis- (negative at phase 1/negative at phase 2), resolved chronic bronchitis (positive/negative), new chronic bronchitis (negative/positive), and persistent chronic bronchitis+ (positive/positive). We analyzed respiratory symptoms, health-related quality of life, lung function, exacerbation frequency, and 6-minute walk distance. MEASUREMENTS AND MAIN RESULTS: Compared with the persistent chronic bronchitis- group, members of the persistent chronic bronchitis+ group were more likely to have continued smoking (53.4%). Subjects with new chronic bronchitis were more likely to have resumed (6.6%) or continued smoking (45.6%), whereas subjects with resolved chronic bronchitis were more likely to have quit smoking (23.5%). Compared with the persistent chronic bronchitis- group, the other groups had a shorter 6-minute walk distance, worse lung function, greater exacerbation frequency, and worse respiratory symptoms. Modified Medical Research Council dyspnea and St. George's Respiratory Questionnaire scores worsened between phase 1 and phase 2 in subjects with new chronic bronchitis but improved in the resolved chronic bronchitis group. On multinomial logistic regression, quitting smoking conferred an odds ratio (OR) of 4.289 (95% confidence interval [CI], 2.689-6.842) for resolved chronic bronchitis, whereas resuming smoking had an OR of 4.585 (95% CI, 2.008-10.471) for new chronic bronchitis. Persistent smoking had an OR of 2.621 (95% CI, 1.677-4.096) and 5.767 (95% CI, 3.702-8.983) for subjects with new chronic bronchitis and subjects with persistent chronic bronchitis, respectively. CONCLUSIONS: Persistent and newly developed chronic bronchitis are associated with continued or resumed smoking, greater respiratory symptoms, worse health-related quality of life, worse lung function, and greater exacerbation frequency. These findings stress the importance of repeatedly assessing chronic cough and sputum production in smokers to identify those at risk for poor outcomes.

Association between Functional Small Airway Disease and FEV1 Decline in Chronic Obstructive Pulmonary Disease.

RATIONALE: The small conducting airways are the major site of airflow obstruction in chronic obstructive pulmonary disease and may precede emphysema development. OBJECTIVES: We hypothesized a novel computed tomography (CT) biomarker of small airway disease predicts FEV1 decline. METHODS: We analyzed 1,508 current and former smokers from COPDGene with linear regression to assess predictors of change in FEV1 (ml/yr) over 5 years. Separate models for subjects without and with airflow obstruction were generated using baseline clinical and physiologic predictors in addition to two novel CT metrics created by parametric response mapping (PRM), a technique pairing inspiratory and expiratory CT images to define emphysema (PRM(emph)) and functional small airways disease (PRM(fSAD)), a measure of nonemphysematous air trapping. MEASUREMENTS AND MAIN RESULTS: Mean (SD) rate of FEV1 decline in ml/yr for GOLD (Global Initiative for Chronic Obstructive Lung Disease) 0-4 was as follows: 41.8 (47.7), 53.8 (57.1), 45.6 (61.1), 31.6 (43.6), and 5.1 (35.8), respectively (trend test for grades 1-4; P < 0.001). In multivariable linear regression, for participants without airflow obstruction, PRM(fSAD) but not PRM(emph) was associated with FEV1 decline (P < 0.001). In GOLD 1-4 participants, both PRM(fSAD) and PRM(emph) were associated with FEV1 decline (P < 0.001 and P = 0.001, respectively). Based on the model, the proportional contribution of the two CT metrics to FEV1 decline, relative to each other, was 87% versus 13% and 68% versus 32% for PRM(fSAD) and PRM(emph) in GOLD 1/2 and 3/4, respectively. CONCLUSIONS: CT-assessed functional small airway disease and emphysema are associated with FEV1 decline, but the association with functional small airway disease has greatest importance in mild-to-moderate stage chronic obstructive pulmonary disease where the rate of FEV1 decline is the greatest. Clinical trial registered with www.clinicaltrials.gov (NCT 00608764).

Genome-wide Mechanosensitive MicroRNA (MechanomiR) Screen Uncovers Dysregulation of Their Regulatory Networks in the mdm Mouse Model of Muscular Dystrophy.

Muscular dystrophies (MDs) are a heterogeneous group of genetic and neuromuscular disorders, which result in severe loss of motor ability and skeletal muscle mass and function. Aberrant mechanotransduction and dysregulated-microRNA pathways are often associated with the progression of MD. Here, we hypothesized that dysregulation of mechanosensitive microRNAs (mechanomiRs) in dystrophic skeletal muscle plays a major role in the progression of MD. To test our hypothesis, we performed a genome-wide expression profile of anisotropically regulated mechanomiRs and bioinformatically analyzed their target gene networks. We assessed their functional roles in the advancement of MD using diaphragm muscles from mdm (MD with myositis) mice, an animal model of human tibial MD (titinopathy), and their wild-type littermates. We were able to show that ex vivo anisotropic mechanical stretch significantly alters the miRNA expression profile in diaphragm muscles from WT and mdm mice; as a result, some of the genes associated with MDs are dysregulated in mdm mice due to differential regulation of a distinct set of mechanomiRs. Interestingly, we found a contrasting expression pattern of the highly expressed let-7 family mechanomiRs, let-7e-5p and miR-98-5p, and their target genes associated with the extracellular matrix and TGF-ß pathways, respectively, between WT and mdm mice. Gain- and loss-of-function analysis of let-7e-5p in myocytes isolated from the diaphragms of WT and mdm mice confirmed Col1a1, Col1a2, Col3a1, Col24a1, Col27a1, Itga1, Itga4, Scd1, and Thbs1 as target genes of let-7e-5p. Furthermore, we found that miR-98 negatively regulates myoblast differentiation. Our study therefore introduces additional biological players in the regulation of skeletal muscle structure and myogenesis that may contribute to unexplained disorders of MD.