Search

The paranasal sinuses are a group of hollow spaces within the human skull, surrounding the nose. They are lined with an epithelium that contains mucus-producing cells and tiny hairlike active appendages called cilia. The cilia beat constantly to sweep mucus out of the sinus into the nasal cavity, thus maintaining a clean mucus layer within the sinuses. This process, called mucociliary clearance, is essential for a healthy nasal environment and disruption in mucus clearance leads to diseases such as chronic rhinosinusitis, specifically in the maxillary sinuses, which are the largest of the paranasal sinuses. We present here a continuum mathematical model of mucociliary clearance inside the human maxillary sinus. Using a combination of analysis and computations, we study the flow of a thin fluid film inside a fluid-producing cavity lined with an active surface: fluid is continuously produced by a wall-normal flux in the cavity and then is swept out, against gravity, due to an effective tangential flow induced by the cilia. We show that a steady layer of mucus develops over the cavity surface only when the rate of ciliary clearance exceeds a threshold, which itself depends on the rate of mucus production. We then use a scaling analysis, which highlights the competition between gravitational retention and cilia-driven drainage of mucus, to rationalise our computational results. We discuss the biological relevance of our findings, noting that measurements of mucus production and clearance rates in healthy sinuses fall within our predicted regime of steady-state mucus layer development., (© 2024. The Author(s).)

Objective: Primary ciliary dyskinesia (PCD) is a respiratory disorder that impairs mucociliary clearance, leading to decreased lung function. Conventional chest physiotherapy (CCP) is the traditional airway clearance technique (ACT) and is considered a standard treatment for PCD patients. This systematic review investigated whether device supported ACTs are better alternatives for improving lung function and/or quality of life in PCD, compared with CCP., Methods: The OVID Medline, PubMed, CINAHL, and Cochrane databases were searched. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed, and the Grading of Recommendations, Assessment, Development, and Evaluation approach was used to aggregate the data. This systematic review has been registered on the International Prospective Register of Systematic Reviews website., Results: Of the 389 citations that resulted from our literature search, 2 randomized crossover trials that included a total of 54 patients were analyzed. The certainty of the aggregated study evidence was very low. No difference was identified between device-supported ACTs and CCP in terms of forced vital capacity and forced expiratory volume in 1 second in PCD patients aged 6 to 20 years., Conclusion: Device-supported ACTs could be considered alternative treatment options to replace CCP. High quality research is required to confirm this result.

Objectives: Saccharin test (ST) is a convenient method to assess the efficiency of mucociliary clearance, the primary defense mechanism of the upper airways' tract. The study objectives are to: (1) substantiate its short- (3 days) and long-term (30 days) repeatability; (2) assess its tolerability; (3) conduct a systematic literature review and to compare our results with the existing evidence., Methods: Twenty-nine healthy subjects were enrolled in an observational prospective study to perform an ST on three separate visits (at baseline; at follow-up visits at day 3 and at day 30). Transit times were recorded and self-reported nasal and general symptoms noted. A systematic review of the literature was conducted to compare our results with the existing literature., Results: The mean values (±SD) of ST transit time (STTT) were 7.085 (±2.19), 7.788 (±2.11), and 7.790 (±2.06) minutes at baseline, day 3, and day 30, respectively. Significant linear regression analysis was observed between day 3 and baseline ( r = .193; P = .019) and day 30 and baseline ( r = .182 P = .024). Significant agreement for the intrasession repeatability was observed with an ICC = .354 ( P = .001). Outcomes' comparisons between baseline vs day 3 ( P = .197) and baseline vs day 30 ( P = .173) were not statistically significant. ST was well tolerated. Concordance with existing literature's data and high level of STTT repeatability were confirmed by the qualitative analysis., Conclusion: STTT reproducibility was good both in the short- and long-term. ST tolerability was very good. Our study data are consistent with the existing literature, indicating ST as a sound methodology for detection of early respiratory health changes and for specific regulatory application in respiratory research., Competing Interests: Conflict of interestSalvatore Ferlito and Salvatore Cocuzza are full-time employees of the University of Catania, Italy. Alessandro Gulino, Antonino Maniaci, and Rosalia Emma are fixed-term researcher at University of Catania, Italy. Francesca Benfatto is fixed-term researcher at Centro per la Prevenzione e Cura del Tabagismo, University of Catania. Jerome Lechien is an associate professor of Mons University; Angelo Ingrassia is an ENT specialist from Catania University. Riccardo Polosa was awarded an Investigator-Initiated Study award program established by Philip Morris International in 2017, but subsequently resigned from the role of Principal Investigator in 2018, before the trial began. Lecture fees from a number of European EC industry and trade associations (including Fédération Interprofessionnelle de la VAPE in France and Federazione Italiana Esercenti Svapo Elettronico in Italy) were directly donated to vaper advocacy no-profit organizations. RP is the Founder of the Center of Excellence for the acceleration of Harm Reduction at the University of Catania (CoEHAR), which has received a grant from Foundation for a Smoke Free World to develop and carry out eight research projects. RP is also currently involved in the following pro bono activities: scientific advisor for LIAF, Lega Italiana Anti Fumo (Italian acronym for Italian Anti-Smoking League), and Chair of the European Technical Committee for standardization on Requirements and test methods for emissions of electronic cigarettes (CEN/TC 437; WG4). Pasquale Caponnetto is paid by the University of Catania as an external part-time researcher and adjunct professor of clinical, addiction, and general psychology. He has been affiliated to the CoEHAR since December 2019 in a pro bono role. He is coauthor of a protocol paper supported by an Investigator-Initiated Study award program established by Philip Morris International in 2017. The other authors have no conflict of interests to declare

Significance statement: A 53-year-old man with left facial pain was referred to our hospital. Nasal endoscopy revealed a purulent discharge at the left middle meatus and bulging of the uncinate process. Computed tomography demonstrated that the dental implant was blocking the left maxillary ostium. Functional endoscopic sinus surgery was performed under general anesthesia. After removal of the uncinate process, a yellowish purulent discharge in the left maxillary sinus discharged from the maxillary sinus. The presence of the dental implant in the infundibulum shows the direction of mucociliary clearance from the nasal sinus. This case indicates how our sinus clears a foreign body, and the direction in which the foreign body is removed., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: Respiratory diseases such as chronic rhinosinusitis and asthma are observed at increased rates in active duty and veteran military members, and they are especially prevalent in individuals who have been deployed in Southwest Asia during Operation Iraqi Freedom and Operation Enduring Freedom. Particulate matter, specifically the fine-grain desert sand found in the Middle East, may be a key source of this pathology because of deleterious effects on mucociliary clearance., Materials and Methods: With IRB approval, human sinonasal tissue was grown at an air-liquid interface and cultures were exposed to different types and sizes of particulate matter, including sand from Afghanistan and Kuwait. Ciliary dynamic responses to mechanical stimulation and ATP application were assessed following particulate exposure., Results: Particle size of the commercial sand was substantially larger than that of the sand of Afghan or Kuwaiti origin. Following exposure to particulate matter, normal dynamic ciliary responses to mechanical stimulation and ATP application were significantly decreased (P < .01), with corresponding decreases in ATP-induced calcium flux (P < .05). These changes were partially reversible with apical washing after a 16-h period of exposure. After 36 h of exposure to Middle Eastern sand, ciliary responses to purinergic stimulation were completely abolished., Conclusions: There is a neutralization of the dynamic ciliary response following chronic particulate matter exposure, similar to ciliary pathologies observed in patients with chronic rhinosinusitis. Aerosolized particulate matter endured by military personnel in the Southwest Asia may cause dysfunctional mucociliary clearance; these data help to explain the increased prevalence of respiratory pathology in individuals who are or have been deployed in this region., (Published by Oxford University Press on behalf of the Association of Military Surgeons of the United States 2024. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: Mucociliary clearance (MCC) is critical to lung health and is impaired in many diseases. The path of MCC may have an important impact on clearance but has never been rigorously studied. The objective of this study is to assess the three-dimensional path of human tracheal MCC in disease and health., Methods: Tracheal MCC was imaged in 12 ex-smokers, 3 non-smokers (1 opportunistically imaged during acute influenza and repeated after recovery) and 5 individuals with primary ciliary dyskinesia (PCD). Radiolabelled macroaggregated albumin droplets were injected into the trachea via the cricothyroid membrane. Droplet movement was tracked via scintigraphy, the path of movement mapped and helical and axial models of tracheal MCC were compared., Measurements and Main Results: In 5/5 participants with PCD and 1 healthy participant with acute influenza, radiolabelled albumin coated the trachea and did not move. In all others (15/15), mucus coalesced into globules. Globule movement was negligible in 3 ex-smokers, but in all others (12/15) ascended the trachea in a helical path. Median cephalad tracheal MCC was 2.7 mm/min ex-smokers vs 8.4 mm/min non-smokers (p=0.02) and correlated strongly to helical angle (r=0.92 (p=0.00002); median 18 o ex-smokers, 47 o non-smokers (p=0.036)), but not to actual speed on helical path (r=0.26 (p=0.46); median 13.6 mm/min ex-smokers vs 13.9 mm/min non-smokers (p=1.0))., Conclusion: For the first time, we show that human tracheal MCC is helical, and impairment in ex-smokers is often caused by flattened helical transit, not slower movement. Our methodology provides a simple method to map tracheal MCC and speed in vivo., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To explore whether the different phases of the nasal cycle have a significant effect on nasal temperature, the nasal mucosal clearance rate, and levels of nasal nitric oxide (nNO) and to investigate the correlation between these nasal conditions., Methods: The study participants were divided into 2 groups: the control group and the rhinitis group. The participants' nasal temperature, cilia clearance rate, and nNO levels were measured during different phases of the nasal cycle (the congestion phase and decongestion phase) in the control group and before and after undergoing inferior turbinate ablation in the rhinitis group., Results: The temperature of the nasal cavity in the control group was significantly higher in the congestion phase than in the decongestion phase ( P = .0025), while in the rhinitis group, the temperature of the nasal cavity decreased significantly after inferior turbinate ablation ( P = .001). In the control group, the nasal mucosa clearance time was significantly shorter in the congestion phase than in the decongestion phase ( P = .001), and in the rhinitis group, the clearance time of the nasal mucosa was significantly shortened after the operation ( P = .0025). In the control group, the levels of nNO were significantly higher in the congestion phase than in the decongestion phase ( P = .025), while in the rhinitis group, nNO levels decreased significantly after the operation ( P = .005)., Conclusion: The function of the nasal cavity changes in different phases of the nasal cycle. Therefore, when evaluating the impact of various factors on nasal function, factors associated with the nasal cycle should also be considered. Inferior turbinate plasma ablation can improve the ciliary function of the nasal mucosa, reduce the temperature of the nasal cavity, and reduce nNO levels., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Airway ciliary cells are components of the mucociliary transport system and play an important role in sweeping out small particles, such as bacteria and viruses, towards the oropharynx by the action of beating cilia. Several lines of evidence have shown that the ciliary beat is under the regulation of the purinergic system; however, the subtype of receptor and the intracellular signaling pathways involved in the activation of ciliary movement remain to be elucidated. In addition, although the activity of ciliary movement comprises two parameters, the ciliary beat frequency (CBF) and ciliary bend angle (CBA), few reports have analyzed CBA. In this study, we examined the effects of ATP and other purinergic ligands on both CBF and CBA and demonstrated that the purinergic signaling requirements for CBF and CBA are different, with CBF mediated by P2Y 1 receptor activation and CBA mediated by the P2X4 receptor.

The article presents the results of a study that included 127 children aged 8 to 17 years with a diagnosis of turbinate hypertrophy. The children are divided into three groups depending on the chosen vasotomy method. The methods of vasotomy were determined, after which there was a faster restoration of mucociliary clearance of the mucous membrane of the lower nasal concha.

Despite the fact that turbinate surgery provides satisfactory results regarding nasal obstruction, most of these procedures are destructive, to some extent, for the respiratory epithelium. There are valid hypotheses suggesting either that turbinate surgery may improve mucociliary clearance (MCC) by improving rhinitis, as well hypotheses suggesting that these surgeries may impair it by damaging the nasal ciliated epithelia. This systematic review is designed with the objective of exploring the effect of turbinate surgery on MCC. Pubmed (Medline), the Cochrane Library, EMBASE, SciELO were analyzed. Four authors members of the YO-IFOS rhinology study group independently analyzed the articles. Extracted variables encompassed: sample size, age, indication for surgery, surgical technique, method used to measure mucociliary clearance, mucociliary transport time before and after surgery, and main outcome. 15 studies with a total population of 1936 participants (1618 patients excluding healthy controls) met the inclusion criteria. 9 studies could be combined in a metanalysis, wich revealed a non-statistically significant decrease of 3.86 min in MCTT after turbinate surgery (p = 0.06). The subgroup analysis of the 5 cohorts who underwent microdebrider turbinoplasty reached statistical significance under a random effect model, revealing a 7.02 min decrease in MCTT (p < 0.001). The laser turbinoplasty subgroup, composed of 4 cohorts, also reached significance, although the difference was lower than that for microdebrider turbinoplasty, 1.01 min (p < 0.001). This systematic review and meta-analysis suggests that turbinate surgery does not compromise mucociliary clearance. The available evidence also suggests that turbinate surgery with mucosa sparing techniques improves MCC, while with aggressive techniques it increases or remains the same. This beneficial effect is evident since the first to third month after surgery. However, for solid conclusions, a standard way to measure MCTT should be stablished, as well as a method to appropriately describe the extension of the surgery., (Copyright © 2023. Published by Elsevier España, S.L.U.)

Airway mucociliary clearance (MCC) is required for host defense and is often diminished in chronic lung diseases. Effective clearance depends upon coordinated actions of the airway epithelium and a mobile mucus layer. Dysregulation of the primary secreted airway mucin proteins, MUC5B and MUC5AC, is associated with a reduction in the rate of MCC; however, how other secreted proteins impact the integrity of the mucus layer and MCC remains unclear. We previously identified the gene Bpifb1/Lplunc1 as a regulator of airway MUC5B protein levels using genetic approaches. Here, we show that BPIFB1 is required for effective MCC in vivo using Bpifb1 knockout (KO) mice. Reduced MCC in Bpifb1 KO mice occurred in the absence of defects in epithelial ion transport or reduced ciliary beat frequency. Loss of BPIFB1 in vivo and in vitro altered biophysical and biochemical properties of mucus that have been previously linked to impaired MCC. Finally, we detected colocalization of BPIFB1 and MUC5B in secretory granules in mice and the protein mesh of secreted mucus in human airway epithelia cultures. Collectively, our findings demonstrate that BPIFB1 is an important component of the mucociliary apparatus in mice and a key component of the mucus protein network. NEW & NOTEWORTHY BPIFB1, also known as LPLUNC1, was found to regulate mucociliary clearance (MCC), a key aspect of host defense in the airway. Loss of this protein was also associated with altered biophysical and biochemical properties of mucus that have been previously linked to impaired MCC.

Bronchial asthma is a heterogeneous respiratory condition characterized by chronic airway inflammation, airway hyperresponsiveness and airway structural changes (known as remodeling). The clinical symptoms can be evoked by (non)specific triggers, and their intensity varies over time. In the past, treatment was mainly focusing on symptoms' alleviation; in contrast modern treatment strategies target the underlying inflammation, even during asymptomatic periods. Components of airway remodeling include epithelial cell shedding and dysfunction, goblet cell hyperplasia, subepithelial matrix protein deposition, fibrosis, neoangiogenesis, airway smooth muscle cell hypertrophy and hyperplasia. Among the other important, and frequently forgotten aspects of airway remodeling, also loss of epithelial barrier integrity, immune defects in anti-infectious defence and mucociliary clearance (MCC) dysfunction should be pointed out. Mucociliary clearance represents one of the most important defence airway mechanisms. Several studies in asthmatics demonstrated various dysfunctions in MCC - e.g., ciliated cells displaying intracellular disorientation, abnormal cilia and cytoplasmic blebs. Moreover, excessive mucus production and persistent cough are one of the well-recognized features of severe asthma and are also associated with defects in MCC. Damaged airway epithelium and impaired function of the ciliary cells leads to MCC dysfunction resulting in higher susceptibility to infection and inflammation. Therefore, new strategies aimed on restoring the remodeling changes and MCC dysfunction could present a new therapeutic approach for the management of asthma and other chronic respiratory diseases., Competing Interests: Declaration of competing interest No conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Key Points: Our findings suggest that primary ciliary dyskinesia (PCD)-related chronic rhinosinusitis (CRS) has a more significant impact on quality of life than CRS without nasal polyps and cystic fibrosis (CF). PCD and CF have similar mucociliary clearance defects, yet sinonasal symptom severity varies between the two., (© 2023 ARS-AAOA, LLC.)

Background: MUC5 dysregulation is a hallmark of severe neutrophilic asthmatic patients. This study investigates the expression of MUC5AC and MUC5B at mRNA levels on asthma severity and airway wall thickness in severe neutrophilic asthmatic patients., Method: In this case-control clinical trial, twenty-five severe neutrophilic asthmatic patients and ten control subjects were enrolled. Subjects underwent ACT, pulmonary functions tests, and fractional exhaled nitric oxide (FENO). Also, induced sputum has been obtained to assess the expression of MUC5AC and MUC5B by the real-time PCR. In addition, the thickness of the airway wall was assessed by high-resolution computed tomography (HRCT), and bioinformatic analysis was implemented to approve the selection of the appropriate genes and for further investigations., Result: A significant difference was observed between the asthmatic and control in MUC5AC and MUC5B mRNA expression. Meanwhile, the expression of MUC5AC increased remarkably by asthma severity; also, it is associated with airway wall thickness (WT) (both P-value <0.05). The expression of MUC5B in asthmatic patients was lower than in control. There is no significant correlation between MUC5B mRNA level and WT and asthma severity. Notably, MUC5AC transcription level was correlated to sputum neutrophil percentage, while MUC5B transcription level had a positive correlation with sputum macrophages and a negative one with sputum neutrophils., Conclusion: In severe neutrophilic asthma, airway wall thickness increases with MUC5AC mRNA overexpression, which is probably related to asthma severity and the formation of mucus plugs. However, the expression of MUC5B was decreased, resulting in poor mucociliary clearance in the airways., Trial Registration: IR.IAU.MSHD.REC.1400.124., Competing Interests: Declaration of competing interest On behalf of all authors, the corresponding author states that there is no conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Purpose: Autosomal dominant polycystic kidney disease (ADPKD) is a renal disease with genetic transmisson. Mutations in the PKD1 and PKD2 genes, which encode integral membrane proteins of the cilia of primary renal tubule epithelial cells, are seen in ADPKD. The aim of this study was to evaluate the sinonasal epithelium, which is epithelium with cilia, by measuring the nasal mucociliary clearance time, and to investigate the effect of ADPKD on nasal mucociliary clearance., Methods: The study included 34 patients, selected from patients followed up in the Nephrology Clinic, and 34 age and gender-matched control group subjects. The nasal mucociliary clearance time (NMCT) was measured with the saccharin test., Results: The mean age of the study subjects was 47.15 ± 14.16 years in the patient group and 47.65 ± 13.85 years in the control group. The eGFR rate was determined as mean 72.06 ± 34.26 mL/min in the patient group and 99.79 ± 17.22 mL/min in the control group (p < 0.001). The NMCT was determined to be statistically significantly longer in the patient group (903.6 ± 487.8 s) than in the control group (580 ± 259 s) (p = 0.006)., Conclusions: The study results showed that the NMCT was statistically significantly longer in patients with ADPKD compared to the control group, but in the linear regression analysis results, no correlation was determined between eGFR and NMCT., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Mucociliary clearance is the first defense mechanism of the respiratory tract against inhaled particles. This mechanism is based on the collective beating motion of cilia at the surface of epithelial cells. Impaired clearance, either caused by malfunctioning or absent cilia, or mucus defects, is a symptom of many respiratory diseases. Here, by exploiting the lattice Boltzmann particle dynamics technique, we develop a model to simulate the dynamics of multiciliated cells in a two-layer fluid. First, we tuned our model to reproduce the characteristic length- and time-scales of the cilia beating. We then check for the emergence of the metachronal wave as a consequence of hydrodynamic mediated correlations between beating cilia. Finally, we tune the viscosity of the top fluid layer to simulate the mucus flow upon cilia beating, and evaluate the pushing efficiency of a carpet of cilia. With this work, we build a realistic framework that can be used to explore several important physiological aspects of mucociliary clearance.

The large airways are a critical component of the respiratory tree serving both an immunoprotective role and a physiological role for ventilation. The physiological role of the large airways is to move a large amount of air to and from the gas exchange surfaces of the alveoli. This air becomes divided along the respiratory tree as it moves from the large airways to smaller airways, bronchioles, and alveoli. The large airways are incredibly important from an immunoprotective role as the large airways are an early line of defense against inhaled particles, bacteria, and viruses. The key immunoprotective feature of the large airways is mucus production and mucociliary clearance mechanism. Each of these key features of the lung is important from both a basic physiology perspective and an engineering perspective for regenerative medicine. In this chapter, we will cover the large airways from an engineering perspective to highlight existing models of the large airways as well as future directions for modeling and repair., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Airway dehydration causes mucus stasis and bacterial overgrowth in cystic fibrosis (CF), resulting in recurrent respiratory infections and exacerbations. Strategies to rehydrate airway mucus including inhibition of the epithelial sodium channel (ENaC) have the potential to improve mucosal defense by enhancing mucociliary clearance (MCC) and reducing the risk of progressive decline in lung function. In the current work, we evaluated the effects of AZD5634, an ENaC inhibitor that shows extended lung retention and safety profile as compared with previously evaluated candidate drugs, in healthy and CF preclinical model systems. We found that AZD5634 elicited a potent inhibition of amiloride-sensitive current in non-CF airway cells and airway cells derived from F508del-homozygous individuals with CF that effectively increased airway surface liquid volume and improved mucociliary transport (MCT) rate. AZD5634 also demonstrated efficacious inhibition of ENaC in sheep bronchial epithelial cells, translating to dose-dependent improvement of mucus clearance in healthy sheep in vivo. Conversely, nebulization of AZD5634 did not notably improve airway hydration or MCT in CF rats that exhibit an MCC defect, consistent with findings from a first single-dose evaluation of AZD5634 on MCC in people with CF. Overall, these findings suggest that CF animal models demonstrating impaired mucus clearance translatable to the human situation may help to successfully predict and promote the successful translation of ENaC-directed therapies to the clinic.

Mucociliary epithelia are composed of multiciliated, secretory, and stem cells and line various organs in vertebrates such as the respiratory tract. By means of mucociliary clearance, those epithelia provide a first line of defense against inhaled particles and pathogens. Mucociliary clearance relies on the correct composition of cell types, that is, the proper balance of ciliated and secretory cells. A failure to generate and to maintain correct cell type composition and function results in impaired clearance and high risk to infections, such as in congenital diseases (e.g., ciliopathies) as well as in acquired diseases, including asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). While it remains incompletely resolved how precisely cell types are specified and maintained in development and disease, many studies have revealed important mechanisms regarding the signaling control in mucociliary cell types in various species. Those studies not only provided insights into the signaling contribution to organ development and regeneration but also highlighted the remarkable plasticity of cell identity encountered in mucociliary maintenance, including frequent trans-differentiation events during homeostasis and specifically in disease. This review will summarize major findings and provide perspectives regarding the future of mucociliary research and the treatment of chronic airway diseases associated with tissue remodeling., (© 2021 S. Karger AG, Basel.)

Airborne pollution has become a leading cause of global death in industrialized cities and the exposure to environmental pollutants has been demonstrated to have adverse effects on human health. Among the pollutants, particulate matter (PM) is one of the most toxic and although its exposure has been more commonly correlated with respiratory diseases, gastrointestinal (GI) complications have also been reported as a consequence to PM exposure. Due to its composition, PM is able to exert on intestinal mucosa both direct damaging effects, (by reaching it either via direct ingestion of contaminated food and water or indirect inhalation and consequent macrophagic mucociliary clearance) and indirect ones via generation of systemic inflammation. The relationship between respiratory and GI conditions is well described by the lung-gut axis and more recently, has become even clearer during coronavirus disease 2019 (COVID-19) pandemic, when respiratory symptoms were associated with gastrointestinal conditions. This review aims at pointing out the mechanisms and the models used to evaluate PM induced GI tract damage., (© 2021 International Union of Biochemistry and Molecular Biology.)

Background: The mucociliary clearance system driven by beating cilia protects the airways from inhaled microbes and particles. Large particles are cleared by mucus bundles made in submucosal glands by parallel linear polymers of the MUC5B mucins. However, the structural organization and function of the mucus generated in surface goblet cells are poorly understood., Methods: The origin and characteristics of different mucus structures were studied on live tissue explants from newborn wild-type (WT), cystic fibrosis transmembrane conductance regulator (CFTR) deficient (CF) piglets and weaned pig airways using video microscopy, Airyscan imaging and electron microscopy. Bronchoscopy was performed in juvenile pigs in vivo., Results: We have identified a distinct mucus formation secreted from the surface goblet cells with a diameter less than two micrometer. This type of mucus was named mucus threads. With time mucus threads gathered into larger mucus assemblies, efficiently collecting particles. The previously observed Alcian blue stained mucus bundles were around 10 times thicker than the threads. Together the mucus bundles, mucus assemblies and mucus threads cleared the pig trachea from particles., Conclusions: These results demonstrate that normal airway mucus is more complex and has a more variable structural organization and function than was previously understood. These observations emphasize the importance of studying young objects to understand the function of a non-compromised lung., (© 2021. The Author(s).)

Background: The effect of Covid-19 infection on nasal mucociliary clearance (MCC) is unknown., Aims/objectives: The aim of this study is to investigate the relationship between Covid-19 and nasal MCC in terms of smoking, Covid-19 symptoms and treatment., Methods: Thirty-six patients who were hospitalized in the pandemic ward due to Covid-19 and 36 volunteers (Covid-19 negative test result) who presented to the otolaryngology outpatient clinic with non-nasal symptoms were included in this study. The Saccharin test was performed in both groups to evaluate nasal MCC., Results: The patients and control groups were not significantly different in terms of age and gender. The nasal MCC time was significantly higher in the patient group compared to the control group (19.18 ± 10.84 min and 13.78 ± 8.18 min, p  = .003)., Conclusions and Significance: In this study, we found that Covid-19 prolonged nasal MCC time regardless of age. We suggest that corticosteroids should be included in the treatment of Covid-19, both with its symptom reduction and its positive effect on MCC duration.

Background: Cough characteristics vary between patients, and this can impact clinical diagnosis and care. The purpose of part two of this state-of-the-art review is to update the American College of Chest Physicians (CHEST) 2006 guideline on global physiology and pathophysiology of cough., Study Design and Methods: A review of the literature was conducted using PubMed and MEDLINE databases from 1951 to 2019 using prespecified search terms., Results: We describe the demographics of typical patients with cough in the clinical setting, including how cough characteristics change across age. We summarize the effect of common clinical conditions impacting cough mechanics and the physical properties of mucus on airway clearance., Interpretation: This is the second of a two-part update to the 2006 CHEST cough guideline; it complements part one on basic phenomenology of cough by providing an extended clinical picture of cough along with the factors that alter cough mechanics and efficiency in patients. A greater understanding of the physiology and pathophysiology of cough will improve clinical management., (Copyright © 2021. Published by Elsevier Inc.)

Understanding how SARS-CoV-2 spreads within the respiratory tract is important to define the parameters controlling the severity of COVID-19. Here we examine the functional and structural consequences of SARS-CoV-2 infection in a reconstructed human bronchial epithelium model. SARS-CoV-2 replication causes a transient decrease in epithelial barrier function and disruption of tight junctions, though viral particle crossing remains limited. Rather, SARS-CoV-2 replication leads to a rapid loss of the ciliary layer, characterized at the ultrastructural level by axoneme loss and misorientation of remaining basal bodies. Downregulation of the master regulator of ciliogenesis Foxj1 occurs prior to extensive cilia loss, implicating this transcription factor in the dedifferentiation of ciliated cells. Motile cilia function is compromised by SARS-CoV-2 infection, as measured in a mucociliary clearance assay. Epithelial defense mechanisms, including basal cell mobilization and interferon-lambda induction, ramp up only after the initiation of cilia damage. Analysis of SARS-CoV-2 infection in Syrian hamsters further demonstrates the loss of motile cilia in vivo. This study identifies cilia damage as a pathogenic mechanism that could facilitate SARS-CoV-2 spread to the deeper lung parenchyma., (© 2021. The Author(s).)

Background: Lung clearance index (LCI) is a promising lung function outcome in individuals with primary ciliary dyskinesia (PCD). The impact of events clinically important for individuals with PCD, such as pulmonary exacerbations, on LCI is unknown., Methods: We conducted an international, multicentre, observational cohort study to assess the association of LCI and risk of pulmonary exacerbation, specific changes in LCI during pulmonary exacerbation and global variability of LCI across four visits every 4 months. Ninety individuals with PCD, aged 3-41 years, underwent nitrogen multiple-breath washout (MBW) and spirometry measurements. The association of LCI and pulmonary exacerbations was assessed by Cox proportional hazards and random-effects regression models., Results: We obtained 430 MBW and 427 spirometry measurements. In total, 379 person-years at risk contributed to the analysis. Per one unit increase (deterioration) in LCI, the risk of future pulmonary exacerbation increased by 13%: HR (95% CI), 1.13 (1.04 to 1.23). If LCI changed from a range of values considered normal to abnormal, the risk of future pulmonary exacerbations increased by 87%: 1.87 (1.08 to 3.23). During pulmonary exacerbations, LCI increased by 1.22 units (14.5%). After pulmonary exacerbations, LCI tended to decline. Estimates of variability in LCI suggested lower variation within individuals compared with variation between individuals. Findings were comparable for forced expiratory volume in 1 s., Conclusion: On a visit-to-visit basis, LCI measurement may add to the prediction of pulmonary exacerbations, the assessment of lung function decline and the potential lung function response to treatment of pulmonary exacerbations., Competing Interests: Competing interests: Relevant financial activities for this work: AS reports grant from Ruhr-University Bochum, payment to institution. MB reports postdoctoral grant KOOR from UZLeuven, payment to institution. Relevant financial activities outside the work: FS has grants/grants pending from LungenLiga Bern, CFCH, and payment for lectures from Vertex, Novartis. MB is a member of the European Reference Network for Rare Respiratory Diseases (ERN-LUNG) Project ID No 739546. She has grants/grants pending from Horizon 2020, MyCyFAPP., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Airway epithelial purinergic receptors control key components of the mucociliary clearance (MCC), the dominant component of pulmonary host defense. In healthy airways, the periciliary liquid (PCL) is optimally hydrated, thus acting as an efficient lubricant layer over which the mucus layer moves by ciliary force. When the hydration of the airway surface decreases, the mucus becomes hyperconcentrated, the PCL collapses, and the "thickened" mucus layer adheres to cell surfaces, causing plaque/plug formation. Mucus accumulation is a major contributing factor to the progression of chronic obstructive lung diseases such as cystic fibrosis (CF) and chronic bronchitis (CB). Mucus hydration is regulated by finely tuned mechanisms of luminal Cl - secretion and Na + absorption with concomitant osmotically driven water flow. These activities are regulated by airway surface liquid (ASL) concentrations of adenosine and ATP, acting on airway epithelial A 2B and P2Y 2 receptors, respectively. The goal of this article is to provide an overview of our understanding of the role of purinergic receptors in the regulation of airway epithelial ion/fluid transport and the mechanisms of nucleotide release and metabolic activities that contribute to airway surface hydration in healthy and chronically obstructed airways., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: People with neuromuscular disorders may have a weak, ineffective cough predisposing them to respiratory complications. Cough augmentation techniques aim to improve cough effectiveness and mucous clearance, reduce the frequency and duration of respiratory infections requiring hospital admission, and improve quality of life., Objectives: To determine the efficacy and safety of cough augmentation techniques in adults and children with chronic neuromuscular disorders., Search Methods: On 13 April 2020, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL, and ClinicalTrials.gov for randomised controlled trials (RCTs), quasi-RCTs, and randomised cross-over trials., Selection Criteria: We included trials of cough augmentation techniques compared to no treatment, alternative techniques, or combinations thereof, in adults and children with chronic neuromuscular disorders., Data Collection and Analysis: Two review authors independently assessed trial eligibility, extracted data, and assessed risk of bias. The primary outcomes were the number and duration of unscheduled hospitalisations for acute respiratory exacerbations. We assessed the certainty of evidence using GRADE., Main Results: The review included 11 studies involving 287 adults and children, aged three to 73 years. Inadequately reported cross-over studies and the limited additional information provided by authors severely restricted the number of analyses that could be performed. Studies compared manually assisted cough, mechanical insufflation, manual and mechanical breathstacking, mechanical insufflation-exsufflation, glossopharyngeal breathing, and combination techniques to unassisted cough and alternative or sham interventions. None of the included studies reported on the primary outcomes of this review (number and duration of unscheduled hospital admissions) or listed 'adverse events' as primary or secondary outcome measures. The evidence suggests that a range of cough augmentation techniques may increase peak cough flow compared to unassisted cough (199 participants, 8 RCTs), but the evidence is very uncertain. There may be little to no difference in peak cough flow outcomes between alternative cough augmentation techniques (216 participants, 9 RCTs). There was insufficient evidence to determine the effect of interventions on measures of gaseous exchange, pulmonary function, quality of life, general function, or participant preference and satisfaction., Authors' Conclusions: We are very uncertain about the safety and efficacy of cough augmentation techniques in adults and children with chronic neuromuscular disorders and further studies are needed., (Copyright © 2021 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.)

Mucociliary transport in the respiratory epithelium depends on beating of cilia to move a mucus layer containing trapped inhaled particles toward the mouth. Little is known about the relationship between cilia beat frequency (CBF) and mucus transport velocity (MTV) in vivo under normal physiological conditions and when inspired air is dry or not fully humidified. This study was designed to use video-microscopy to simultaneously measure CBF and MTV in the tracheal epithelium through an implanted optical window in mechanically ventilated lambs. The inspired air in 6 animals was heated to body temperature and fully saturated with water for 4 hours as a baseline. In another series of experiments, 5 lambs were ventilated with air at different temperatures and humidities and the mucosal surface temperature was monitored with infrared macro-imaging. In the baseline experiments, during ventilation with fully humidified air at body temperature, CBF remained constant, mean 13.9 ± 1.6 Hz but MTV varied considerably between 0.1 and 26.1 mm/min with mean 11.0 ± 3.9 mm/min, resulting in a maximum mucus displacement of 34.2 µm/cilia beat. Fully humidified air at body temperature prevented fluctuations in the surface temperature during breathing indicating a thermodynamic balance in the airways. When lambs were ventilated with dryer air, the mucosal surface temperature and MTV dropped without a significant change in CBF. When inspired air was dry, mainly latent heat (92%) was transferred to air in the trachea, reducing the surface temperature by 5 °C. Reduced humidity of the inspired air lowered the surface temperature and reduced MTV in the epithelium during ventilation.

In this study, we aimed to investigate the effects of chronic sleep deprivation on mucociliary clearance, which is the primary defence mechanism of the upper airway tract and nasal mucosal histology. Forty-two Wistar Albino rats (250-300 g), 8 or 12 weeks old, were randomly assigned into three groups as follows. The first sleep-deprivation group consisted of 14 rats (A), another 14 of them were assigned to platform group (B), and the remaining 14 were included to the home cage control group (C). For the two deprivation groups (A and B), the modified multiple platform method (MMPM) was used to induce sleep deprivation for 21 days. Tc-99m MAA rhinoscintigraphy was performed to assess mucociliary clearance and the nasal histopathological changes of the sacrificed rats were also examined. Mucociliary clearance was significantly higher in sleep deprivation (A) and deprivation control (B) groups than the control group (C) (p = .037). The ratio of columnar ciliary was significantly higher in group A and B than in the control group (p = .003). The transitional epithelial ratio in groups A and B was also significantly increased compared with group C (p = .04). The control group's squamous epithelial ratio was increased compared to the sleep-deprived groups (p = .003). There was a significantly increased inflammatory response in the ciliated columnar epithelium in groups A and B compared to group C (p = .02). For the first time in the literature, we demonstrated that chronic sleep deprivation has caused a significant increase in mucociliary clearance speed and in the number of ciliary cells., (© 2020 European Sleep Research Society.)

The tracheobronchial tree is lined by a mucociliary epithelium containing millions of multiciliated cells. Their integrated oscillatory activity continuously propels an overlying pollution-protecting mucus layer in cranial direction, leading to mucociliary clearance - the primary defence mechanism of the airways. Mucociliary transport is commonly thought to co-emerge with the collective ciliary motion pattern under appropriate geometrical and rheological conditions. Proper ciliary alignment is therefore considered essential to establish mucociliary clearance in the respiratory system. Here, we used volume electron microscopy in combination with high-speed reflection contrast microscopy in order to examine ciliary orientation and its spatial organization, as well as to measure the propagation direction of metachronal waves and the direction of mucociliary transport on bovine tracheal epithelia with reference to the tracheal long axis (TLA). Ciliary orientation is measured in terms of the basal body orientation (BBO) and the axonemal orientation (AO), which are commonly considered to coincide, both equivalently indicating the effective stroke as well as the mucociliary transport direction. Our results, however, reveal that only the AO is in line with the mucociliary transport, which was found to run along a left-handed helical trajectory, whereas the BBO was found to be aligned with the TLA. Furthermore, we show that even if ciliary orientation remains consistent between adjacent cells, ciliary orientation exhibits a gradual shift within individual cells. Together with the symplectic beating geometry, this intracellular orientational pattern could provide for the propulsion of highly viscous mucus and likely constitutes a compromise between efficiency and robustness., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: Chronic rhinosinusitis is associated with altered mucociliary clearance and olfaction. The study aimed to analyse the reversibility of impairment and endoscopic factors predicting changes in mucociliary clearance and olfactory parameters., Methods: This prospective study included patients undergoing functional endoscopic sinus surgery for medically refractory chronic rhinosinusitis. Pre- and post-operative measurements of mucociliary clearance, olfactory thresholds, and identification scores were recorded., Results: Of the 96 patients, 65.6 per cent had polyposis and 80.2 per cent underwent primary surgery. Improvements in mucociliary clearance and olfaction scores were seen in all patients, with greater reversibility of impairment in patients with polyposis and in those who underwent revision surgery. The presence of polyps correlated significantly with changes in mucociliary clearance and olfaction., Conclusion: The study highlights improvements in mucociliary clearance, olfactory thresholds and identification scores after functional endoscopic sinus surgery in chronic rhinosinusitis with or without nasal polyposis, as well as for primary and revision surgeries. Adequate post-operative care and prevention of polyps recurrence help to improve mucociliary clearance and olfaction scores.

Introduction: The aim of this study was to investigate the relationship between nasal mucociliary clearance time (NMCT), degree of smoking dependence, cumulative smoking burden and OSAS severity in smokers., Material and Methods: 123 patients (Group 1) with OSAS and 92 healthy controls (Group 2) were included in the study. Group 1 was divided into smokers (Group 1a) and non-smokers (Group 1b). In Group 1a, cumulative smoking burden and Fagerström nicotine dependence test (FNDT) were questioned. Saccharin test was applied to Groups 1 and 2. Student-t, Mann-Whitney-U, Anova, Kruskal-Wallis tests were used to compare the means., Results: NMCT was higher in Group 1 than Group 2 (p = 0.005). The duration of NMCT was higher in Group 1A than Group 1B (p = 0.002). In Group 1a, NMCT values of mild and moderate OSAS patients were longer than in Group 1b (p = 0.02, p = 0.01, respectively). NMCT values of patients with mild dependence were shorter than those with moderate or severe dependence (p = 0.032, p < 0.001, respectively)., Conclusion: Mucociliary clearance time was higher in smokers with OSAS than non-smokers. While OSAS has a negative effect on mucociliary clearance, smoking also exacerbates the condition.

Respiratory motile cilia, specialized organelles of the cell, line the apical surface of epithelial cells lining the respiratory tract. By beating in a metachronal, synchronal fashion, these multiple, motile, actin-based organelles generate a cephalad fluid flow clearing the respiratory tract of inhaled pollutants and pathogens. With increasing environmental pollution, novel viral pathogens and emerging multi-drug resistant bacteria, cilia generated mucociliary clearance (MCC) is essential for maintaining lung health. MCC is also depressed in multiple congenital disorders like primary ciliary dyskinesia, cystic fibrosis as well as acquired disorders like chronic obstructive pulmonary disease. All these disorders have established, in some case multiple, mouse models. In this publication, we detail a method using a small amount of radioactivity and dual-modality SPECT/CT imaging to accurately and reproducibly measure MCC in mice in vivo. The method allows for recovery of mice after imaging, making serial measurements possible, and testing potential therapeutics longitudinally over time. The data in wild-type mice demonstrates the reproducibility of the MCC measurement as long as adequate attention to detail is paid, and the protocol strictly adhered to.

Background: Mucociliary clearance (MCC) rate from the lung has been shown to be reduced in chronic obstructive pulmonary disease (COPD). This study investigates the value of regional clearance measurements in assessing MCC in mild-to-moderate disease. Methods: Measurement of lung MCC using planar gamma camera imaging was performed in three groups: (i) healthy nonsmoking controls (NSCs) ( n  = 9), (ii) smoking controls (SCs) who were current smokers with normal lung function ( n  = 10), and (iii) current smokers with mild-to-moderate COPD and bronchitis ( n  = 15). The mean (±standard deviation) forced expiratory volumes at 1 second (FEV1) for the three groups were 109 (± 18), 94 (± 5), and 78 (± 12), respectively. After inhalation of a technetium-99m labeled aerosol, planar imaging was performed over 4 hours and then at 24 hours. Both lung clearance and tracheobronchial clearance (TBC) (normalized to 24 hours clearance) were calculated for inner and outer lung zones. Inner zone clearance was corrected for input from the outer zone. A novel parameter, the bronchial airways clearance index (BACI), which combined clearance data from both zones, was also evaluated. Regional results were compared with whole lung clearance in the same subjects. Results: Corrected inner zone clearance at 3 hours was not reduced compared with NSC in either SCs or COPD. Outer zone clearance was higher in COPD than in the other groups. Corrected inner zone TBC showed significant reductions in SC and COPD compared with NSC. BACI was significantly reduced in COPD compared with NSC and also correlated with FEV1. The mean BACI for SC was also reduced compared with NSC, but the distribution of results was bimodal, with a significant proportion of subjects having values in the NSC range. Conclusions: Regional MCC demonstrated differences between NSCs, SCs, and subjects with mild-to-moderate COPD, which were not apparent with whole lung measurements.

Introduction: The efficacy of inhaled hypertonic saline for bronchiectasis remains controversial. We conduct a systematic review and meta-analysis to explore the influence of inhaled hypertonic saline versus 0.9% isotonic saline for the treatment of bronchiectasis., Methods: We have searched PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through April 2020 for randomized controlled trials (RCTs) assessing the efficacy of inhaled hypertonic saline versus 0.9% isotonic saline for the treatment of bronchiectasis. This meta-analysis was performed using the random-effect model., Results: Four RCTs were included in the meta-analysis. Overall, compared with control group for bronchiectasis, inhaled hypertonic saline had no obvious influence on forced expiratory volume in 1 s (FEV1, SMD = 0.12; 95% CI = -0.06 to 0.30; P = .18), forced vital capacity (FVC, SMD = 0.10; 95% CI = -0.09 to 0.28; P = .30), sputum expectorated (SMD = -0.03; 95% CI = -2.73 to 2.68; P = .99) or Leicester Cough Questionnaire (LCQ) score (SMD = -0.15; 95% CI = -0.89 to 0.58; P = .68)., Conclusions: Inhaled hypertonic saline and 0.9% isotonic saline show similar efficacy for bronchiectasis., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2020. Published by Elsevier Inc.)

Background: Viral respiratory tract infections, such as influenza A virus (IAV), are common and life-threatening illnesses worldwide. The mechanisms by which viruses are removed from the respiratory tract are indispensable for airway host defense. Mucociliary clearance is an airway defense mechanism that removes pathogens from the respiratory tract. The coordination and modulation of the ciliary beating of airway epithelial cells play key roles in maintaining effective mucociliary clearance. However, the impact of respiratory virus infection on ciliary activity and mucociliary clearance remains unclear., Methods: Tracheal samples were taken from wild-type (WT) and Toll-like receptor 3 (TLR3)-knockout (KO) mice. Transient organ culture of murine trachea was performed in the presence or absence of IAV, polyI:C, a synthetic TLR3 ligand, and/or reagents. Subsequently, cilia-driven flow and ciliary motility were analyzed. To evaluate cilia-driven flow, red fluorescent beads were loaded into culture media and movements of the beads onto the tracheal surface were observed using a fluorescence microscope. To evaluate ciliary motility, cilia tips were labeled with Indian ink diluted with culture medium. The motility of ink-labeled cilia tips was recorded by high-speed cameras., Results: Short-term IAV infection significantly increased cilia-driven flow and ciliary beat frequency (CBF) compared with the control level in WT culture. Whereas IAV infection did not elicit any increases of cilia-driven flow and CBF in TLR3-KO culture, indicating that TLR3 was essential to elicit an increase of cilia-driven flow and CBF in response to IAV infection. TLR3 activation by polyI:C readily induced adenosine triphosphate (ATP) release from the trachea and increases of cilia-driven flow and CBF in WT culture, but not in TLR3-KO culture. Moreover, blockade of purinergic P2 receptors (P2Rs) signaling using P2R antagonist, suramin, suppressed polyI:C-mediated increases of cilia-driven flow and CBF, indicating that TLR3-mediated ciliary activation depended on released extracellular ATP and the autocrine ATP-P2R loop., Conclusions: IAV infection readily increases ciliary activity and cilia-driven flow via TLR3 activation in the airway epithelium, thereby hastening mucociliary clearance and "sweeping" viruses from the airway as an initial host defense response. Mechanically, extracellular ATP release in response to TLR3 activation promotes ciliary activity through autocrine ATP-P2R loop.

Respiratory cilia are the driving force of the mucociliary escalator, working in conjunction with secreted airway mucus to clear inhaled debris and pathogens from the conducting airways. Respiratory cilia are also one of the first contact points between host and inhaled pathogens. Impaired ciliary function is a common pathological feature in patients with chronic airway diseases, increasing susceptibility to respiratory infections. Common respiratory pathogens, including viruses, bacteria, and fungi, have been shown to target cilia and/or ciliated airway epithelial cells, resulting in a disruption of mucociliary clearance that may facilitate host infection. Despite being an integral component of airway innate immunity, the role of respiratory cilia and their clinical significance during airway infections are still poorly understood. This review examines the expression, structure, and function of respiratory cilia during pathogenic infection of the airways. This review also discusses specific known points of interaction of bacteria, fungi, and viruses with respiratory cilia function. The emerging biological functions of motile cilia relating to intracellular signaling and their potential immunoregulatory roles during infection will also be discussed.

New Findings: What is the central question of this study? What is the impact of airway cholinergic history on the properties of airway mucus secretion in a cystic fibrosis-like environment? What is the main finding and its importance? Prior cholinergic challenge slightly modifies the characteristics of mucus secretion in response to a second cholinergic challenge in a diminished bicarbonate and chloride transport environment. Such modifications might lead to retention of mucus on the airway surface, thereby potentiating exacerbations of airway disease., Abstract: Viral infections precipitate exacerbations in many airway diseases, including asthma and cystic fibrosis. Although viral infections increase cholinergic transmission, few studies have examined how cholinergic history modifies subsequent cholinergic responses in the airway. In our previous work, we found that airway resistance in response to a second cholinergic challenge was increased in young pigs with a history of airway cholinergic stimulation. Given that mucus secretion is regulated by the cholinergic nervous system and that abnormal airway mucus contributes to exacerbations of airway disease, we hypothesized that prior cholinergic challenge would also modify subsequent mucus responses to a secondary cholinergic challenge. Using our established cholinergic challenge-rechallenge model in pigs, we atomized the cholinergic agonist bethanechol or saline control to pig airways. Forty-eight hours later, we removed tracheas and measured mucus secretion properties in response to a second cholinergic stimulation. The second cholinergic stimulation was conducted in conditions of diminished chloride and bicarbonate transport to mimic a cystic fibrosis-like environment. In pigs previously challenged with bethanechol, a second cholinergic stimulation produced a mild increase in sheet-like mucus films; these films were scarcely observed in animals originally challenged with saline control. The subtle increase in mucus films was not associated with changes in mucociliary transport. These data suggest that prior cholinergic history might modify mucus secretion characteristics with subsequent stimulation in certain environmental conditions or disease states. Such modifications and/or more repetitive stimulation might lead to retention of mucus on the airway surface, thereby potentiating exacerbations of airway disease., (© 2020 The Authors. Experimental Physiology © 2020 The Physiological Society.)

Bronchial diseases are characterised by the weak efficiency of mucus transport through the lower airways, leading in some cases to the muco-obstruction of bronchi. It has been hypothesised that this loss of clearance results from alterations in the mucus rheology, which are reflected in sputum samples collected from patients, making sputum rheology a possible biophysical marker of these diseases and their evolution. However, previous rheological studies have focused on quasi-static viscoelastic (linear storage and loss moduli) properties only, which are not representative of the mucus mobilisation within the respiratory tract. In this paper, we extend this approach further, by analysing both quasi-static and some dynamic (flow point) properties, to assess their usability and relative performance in characterising several chronic bronchial diseases (asthma, chronic obstructive pulmonary disease, and cystic fibrosis) and distinguishing them from healthy subjects. We demonstrate that pathologies influence substantially the linear and flow properties. Linear moduli are weakly condition-specific and even though the corresponding ranges overlap, distinct levels can be identified. This directly relates to the specific mucus structure in each case. In contrast, the flow point is found to strongly increase in muco-obstructive diseases, which may reflect the complete failure of mucociliary clearance causing episodic obstructions. These results suggest that the analysis of quasi-static and dynamic regimes in sputum rheology is in fact useful as these regimes provide complementary markers of chronic bronchial diseases.

Airway mucociliary clearance (MCC) is the main mechanism of lung defense keeping airways free of infection and mucus obstruction. Airway surface liquid volume, ciliary beating, and mucus are central for proper MCC and critically regulated by sodium absorption and anion secretion. Impaired MCC is a key feature of muco-obstructive diseases. The calcium-activated potassium channel KCa.3.1, encoded by Kcnn4, participates in ion secretion, and studies showed that its activation increases Na+ absorption in airway epithelia, suggesting that KCa3.1-induced hyperpolarization was sufficient to drive Na+ absorption. However, its role in airway epithelium is not fully understood. We aimed to elucidate the role of KCa3.1 in MCC using a genetically engineered mouse. KCa3.1 inhibition reduced Na+ absorption in mouse and human airway epithelium. Furthermore, the genetic deletion of Kcnn4 enhanced cilia beating frequency and MCC ex vivo and in vivo. Kcnn4 silencing in the Scnn1b-transgenic mouse (Scnn1btg/+), a model of muco-obstructive lung disease triggered by increased epithelial Na+ absorption, improved MCC, reduced Na+ absorption, and did not change the amount of mucus but did reduce mucus adhesion, neutrophil infiltration, and emphysema. Our data support that KCa3.1 inhibition attenuated muco-obstructive disease in the Scnn1btg/+ mice. K+ channel modulation may be a therapeutic strategy to treat muco-obstructive lung diseases.

Objectives/hypothesis: Reversibility of nasal airflow after decongestion measured by rhinomanometry is associated with the severity of allergic inflammation. Peak nasal flow is a simpler alternative method for assessing nasal patency. The aim of this study was to evaluate the correlation between changes in peak nasal expiratory and inspiratory flows (PNEFs and PNIFs) after decongestion and nasal mucociliary clearance times (NMCCTs)., Study Design: Single-center, prospective cross-sectional study., Methods: One hundred one allergic rhinitis patients were enrolled. Nasal symptoms and NMCCTs were assessed. PNEF and PNIF were performed before and after decongestion. Correlations between changes in PNEF and PNIF after decongestion and NMCCTs were analyzed. One-half the standard deviation of baseline peak nasal flows was used to estimate the minimal clinically important differences (MCIDs) and discriminate between patients with reversible mucosa and with irreversible mucosa., Results: PNEF showed more peak flow improvements after decongestion compared to PNIF. Changes in PNEF had better negative correlations with NMCCTs than PNIF (ρ = -0.49, P < .001 and ρ = -0.34, P < .001, respectively). The MCID values of the PNEF and PNIF were 27.93 and 19.74, respectively. In comparisons of NMCCTs between patients with or without MCID of peak nasal flow after decongestion, PNEF had better discrimination ability compared to PNIF (P = .003 and P = .026, respectively)., Conclusions: The limitation of reversibility as measured by peak nasal flows could indirectly point to the affection of mucosal inflammation as indicated by NMCCTs. PNEF is more sensitive to assess peak flow changes after decongestion than PNIF., Level of Evidence: 2 Laryngoscope, 130:1372-1376, 2020., (© 2019 The American Laryngological, Rhinological and Otological Society, Inc.)

In the lung, the airway surface is protected by mucus, whose transport and evacuation is ensured through active ciliary beating. The mechanisms governing the long-range directional organization of ciliary beats, required for effective mucus transport, are much debated. Here, we experimentally show on human bronchial epithelium reconstituted in-vitro that the dynamics of ciliary-beat orientation is closely connected to hydrodynamic effects. To examine the fundamental mechanisms of this self-organization process, we build a two-dimensional model in which the hydrodynamic coupling between cilia is provided by a streamwise-alignment rule governing the local orientation of the ciliary forcing. The model reproduces the emergence of the mucus swirls observed in the experiments. The predicted swirl sizes, which scale with the ciliary density and mucus viscosity, are in agreement with in-vitro measurements. A transition from the swirly regime to a long-range unidirectional mucus flow allowing effective clearance occurs at high ciliary density and high mucus viscosity. In the latter case, the mucus flow tends to spontaneously align with the bronchus axis due to hydrodynamic effects.

Primary human bronchial epithelial cell (HBEC) cultures are a useful model for studies of lung health and major airway diseases. However, mechanistic studies have been limited by our ability to selectively disrupt specific genes in these cells. Here we optimize methods for gene targeting in HBECs by direct delivery of single guide RNA (sgRNA) and rCas9 (recombinant Cas9) complexes by electroporation, without a requirement for plasmids, viruses, or antibiotic selection. Variations in the method of delivery, sgRNA and rCas9 concentrations, and sgRNA sequences all had effects on targeting efficiency, allowing for predictable control of the extent of gene targeting and for near-complete disruption of gene expression. To demonstrate the value of this system, we targeted SPDEF , which encodes a transcription factor previously shown to be essential for the differentiation of MUC5AC-producing goblet cells in mouse models of asthma. Targeting SPDEF led to proportional decreases in MUC5AC expression in HBECs stimulated with IL-13, a central mediator of allergic asthma. Near-complete targeting of SPDEF abolished IL-13-induced MUC5AC expression and goblet cell differentiation. In addition, targeting of SPDEF prevented IL-13-induced impairment of mucociliary clearance, which is likely to be an important contributor to airway obstruction, morbidity, and mortality in asthma. We conclude that direct delivery of sgRNA and rCas9 complexes allows for predictable and efficient gene targeting and enables mechanistic studies of disease-relevant pathways in primary HBECs.

Objectives: The aim of the present study was to measure nasal mucociliary clearance (NMC) time in the patients with MS and to compare the findings with healthy population., Methods: Totally 97 individuals including 47 patients with relapsing-remitting multiple sclerosis and 50 healthy volunteers were enrolled into the study. Saccharin clearance test was performed on both groups and NMC time was measured. Data analysis was performed by SPSS version 24.0 statistics program (SPSS Inc., Chicago, Illinois, USA). Statistical tests were interpreted at p < 0.05 significance level., Results: The NMC time averages in MS patients and healthy control group were 12.43 ± 4.05 min and 8.14 ± 2.87 min, respectively; the difference between the groups was significant (p < 0.001). There was a statistically strong association between NMC time values and Expanded Disability Status Scale (EDSS) values in MS patients (r = 0.817, p < 0.001)., Conclusion: We found nasal mucociliary transport time longer in MS patients than healthy population in the present study. To the best of our knowledge, there is not any study conducted about this topic in the literature. We believe that our findings would shed a light on further studies.

The observed spatiotemporal ciliary beat patterns leading to proper mucociliary clearance on multiciliated epithelia are suspected to be the result of self-organizing processes on various levels. Here, we present a simplified pluricellular epithelium model, which intends to make the self-organization of ciliary beating patterns as well as of the associated fluid transport across the airway epithelium plausible. The model is based on a two-dimensional array of locally interacting oscillating ciliated cells. Ciliated cells are represented by Boolean actuators, and abstracted hydrodynamic mucociliary interactions are formulated in terms of logical update rules (Boolean functions). In the course of a simulation, initial random conformations of an array of actuators self-organize toward metachronally coordinated states exhibiting efficient transport of mucus. Within the framework of Boolean networks ciliated cells represent the nodes of the network and as the mucus establishes the local interactions among nodes, its distribution (together with the formulated local interactions) determines the topology of the network. Consequently, we propose to consider the dynamics on multiciliated epithelia in the context of adaptive (Boolean) networks. Furthermore, we would like to present insights gained from conducted comprehensive parameter studies. In particular, the dynamical response of the network with respect to variations of the boundary conditions, updating schemes (representing intercellular signaling mechanisms) and the proportion of ciliated cells is presented.

Purpose: The aim of this study is to investigate the effect of wood dust on nasal mucociliary clearance time in wood industry workers. Moreover, the correlation between duration of exposure to wood dust and nasal mucociliary clearance time will be evaluated., Methods: A total of 50 male subjects were included in the study. All of the subjects were non-smokers. Nasal mucociliary clearance time of 25 wood industry workers was measured with saccharine method and compared with the results of 25 age-matched control group. Also, the correlation between nasal mucociliary clearance time and duration of exposure to wood dust in woodworkers was evaluated., Results: The mean mucociliary clearance time in control group and wood industry workers was 12.28 ± 1.98 and 16.72 ± 2.71, respectively. The mean mucociliary clearance time in wood industry workers was significantly longer than control group (p < 0.0001). Also,there was positive correlation between duration of exposure to wood dust and nasal mucociliary clearance time in wood industry workers (r = 0.879, p < 0.0001)., Conclusion: The clinicians must remember that mucociliary clearance time in wood industry workers is prolonged. So the wood industry workers must be followed up more closely for sinonasal infections and respiratory tract diseases.

The airways of the human respiratory system are covered by a protective layer, which is known as airway surface liquid (ASL). This layer consists of two relatively distinct sub-layers; a mucus layer (ML), and a periciliary liquid layer (PCL). In addition, the airways are lined with a dense mat of hair-like structures, called cilia, which beat back and forth in a co-ordinated manner and mainly propel the mucus layer. Such interaction between the cilia and mucus is called 'muco-ciliary clearance' (MCC) which is essential to clear the respiratory airways from the inhaled toxic particles deposited on the mucus. The complex nature of lung clearance mechanisms limit the ability to conduct experiments to investigate micro-scale physiological phenomena. As such, modelling techniques are commonly implemented to investigate the effects of biological parameters on the lung muco-ciliary clearance. In the present work, modelling techniques of cilia-ASL interactions - including continuum cilia modelling and discrete cilia modelling - are reviewed and the numerical procedures and level of complexity related to each technique are explained. This is followed by a detailed analysis of the airway surface liquid modelling approaches. In addition, findings of numerical investigations related to the effects of various parameters such as ciliary beat frequency (CBF), mucus rheology, metachronal waves of cilia, surface tension at the PCL-mucus interface, ciliary length, ciliary density, and airway surface liquid depth on the bronchial and tracheal ASL transport are reviewed. This review also explains how these biological parameters can alter the internal power required to perform ciliary beating. Lastly, the main limitations of current numerical works are discussed and significant research directions are brought forward that may be considered in future models to better understand this complex human biological system and its vital clearance mechanism., (Copyright © 2019 Elsevier Ltd. All rights reserved.)