MUC5B mobilizes and MUC5AC spatially aligns mucociliary transport on human airway epithelium

Foreign Mucins Alter the Properties of Reconstituted Gastric Mucus

During the course of evolution, distinct mucin subtypes have evolved, that predominantly occur in specific mucus variants of the body. A loss of this clear regional assignment is often associated with pathophysiological conditions such as asthma or gastric cancer. We here reconstitute mucus from different mucin subtypes to elucidate the influence of MUC5B/MUC2 contaminations on physiologically relevant properties of acidic MUC5AC gels as found in the stomach. Our findings indicate that these properties may be critically altered by the presence of an atypical mucin species. A weak integration of a contaminating mucin subtype into the host network yields weak viscoelastic gels with increased barrier capabilities. Unravelling the complex properties of mucosal barriers under disease conditions is crucial for the understanding of mucosal disease progression and for developing drug-carriers to traverse this biological barrier. Here, our results provide useful insights into mechanistic principles governing the physical properties of gastro-intestinal mucus.

Mucus Physically Restricts Influenza A Viral Particle Access to the Epithelium

Prior work suggests influenza A virus (IAV) crosses the airway mucus barrier in a sialic acid-dependent manner through the actions of the viral envelope proteins, hemagglutinin, and neuraminidase. However, host and viral factors that influence how efficiently mucus traps IAV remain poorly defined. In this work, how the physicochemical properties of mucus influence its ability to effectively capture IAV is assessed using fluorescence video microscopy and multiple particle tracking. Our studies suggest an airway mucus gel layer must be produced with virus-sized pores to physically constrain IAV. While sialic acid binding by IAV may improve mucus trapping efficiency, sialic acid binding preference is found to have little impact on IAV mobility and the fraction of viral particles expected to penetrate the mucus barrier. Further, synthetic polymeric hydrogels engineered with mucus-like architecture are similarly protective against IAV infection despite their lack of sialic acid decoy receptors. Together, this work provides new insights on mucus barrier function toward IAV with important implications on innate host defense and transmission of respiratory viruses.

AAV-mediated MUC5AC siRNA delivery to prevent mucociliary dysfunction in asthma

The main structural components of mucus produced in the lung are mucin 5B (MUC5B) and mucin 5AC (MUC5AC) where a relatively higher expression of MUC5B is typical in health. In the lungs of individuals with asthma, there is a shift from MUC5B to MUC5AC as the predominantly secreted mucin which has been shown to impair mucociliary clearance (MCC) and increase mucus plug formation in the airways. Given its role in asthmatic lung disease, MUC5AC represents a potential therapeutic target where a gene delivery approach could be leveraged to modulate its expression. For these purposes, we explored adeno-associated virus serotype 6 (AAV6), as a lung-tropic viral gene vector to target airway epithelial cells and reduce MUC5AC expression via siRNA delivery. We confirmed that AAV6 was able to transduce epithelial cells in the airways of healthy mice with high transgene expression in mucus-secreting goblet cells. Using multiple particle tracking analysis, we observed that AAV6 was capable of penetrating both normal and MUC5AC-enriched mucus barriers. Successful transduction with AAV6 was also achieved in IL-13 stimulated human airway epithelial (HAE) cells differentiated at air-liquid interface (ALI). AAV6 expressing MUC5AC-targeting siRNA was evaluated as a prophylactic treatment in HAE cell cultures before IL-13 challenge. IL-13 stimulated HAE cultures treated with AAV6-MUC5AC siRNA had significantly reduced MUC5AC mRNA and protein expression compared to untreated controls. Mucociliary transport in IL-13 stimulated HAE cultures was also maintained and comparable to healthy controls following AAV6-MUC5AC siRNA treatment. Together, these findings support that AAV6 may be used as an inhaled gene therapy to suppress MUC5AC overexpression and restore normal airway clearance function in asthma.

Structure and function relationships of mucociliary clearance in human and rat airways

Mucociliary clearance is a vital defense mechanism of the human airways, protecting against harmful particles and infections. When this process fails, it contributes to respiratory diseases like chronic obstructive pulmonary disease (COPD) and asthma. While advances in single-cell transcriptomics have revealed the complexity of airway composition, much of what we know about how airway structure impacts clearance relies on animal studies. This limits our ability to create accurate human-based models of airway diseases. Here we show that the airways in female rats and in humans exhibit species-specific differences in the distribution of ciliated and secretory cells as well as in ciliary beat, resulting in significantly higher clearance effectiveness in humans. We further reveal that standard lab-grown cultures exhibit lower clearance effectiveness compared to human airways, and we identify the underlying structural differences. By combining diverse experiments and physics-based modeling, we establish universal benchmarks to assess human airway function, interpret preclinical models, and better understand disease-specific impairments in mucociliary clearance.

MUC5AC filaments illuminate the structural diversification of respiratory and intestinal mucins

Secreted mucins are multimegadalton glycoprotein polymers that share the function of protecting mucosal tissues but diversified for activities in different organs of the body. Structural studies of secreted mucins are complicated by the enormous sizes, flexibility, and complex supramolecular assembly modes of these glycoproteins. The two major respiratory mucins are MUC5AC and MUC5B. Here, we present structures of a large amino-terminal segment of MUC5AC in the form of helical filaments. These filaments differ from filamentous and tubular structures observed previously for the intestinal mucin MUC2 and the partial mucin homolog VWF. Nevertheless, the MUC5AC helical filaments support the proposed mechanism, based on MUC2 and VWF, for how noncovalent interactions between mucin monomers guide disulfide crosslinking to form polymers. The high-resolution MUC5AC structures show how local and limited changes in amino acid sequence can profoundly affect higher-order assembly while preserving the overall folds and polymerization activity of mucin glycoproteins. Differences in supramolecular assembly are likely to be functionally significant considering the divergence of mechanical properties and physiological requirements between respiratory and intestinal mucins. Determining the high-resolution structures of respiratory mucins provides a foundation for understanding the mechanisms by which they clean and protect the lungs. Moreover, the MUC5AC structure enables visualization of the sites of human amino acid sequence variation and disease-associated mutations.

Differential Responses of Pediatric and Adult Primary Epithelial Cells to Human Metapneumovirus and Respiratory Syncytial Virus Infection

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are pneumoviruses causing lower respiratory tract infections, primarily in infants and children rather than in healthy adults. Human bronchial epithelial cells serve as a viral replication target and source of the innate immune response to these viruses. To better understand the immune responses induced by RSV and HMPV in the pediatric airway epithelium, we comparatively studied pediatric and adult epithelial responses. We used normal human bronchial epithelial (NHBE) cells cultured in an air-liquid interface culture system (ALI), which helps to mimic the architecture of the human lower respiratory tract epithelium. Our results demonstrate differential viral replication patterns and reduced interferons; and inflammatory cytokines' expression in pediatric cells compared to adult cells. However, pediatric epithelial cells expressed an increased mucus response and induced a stronger pro-inflammatory response in monocyte-derived dendritic cells. These findings reveal age-dependent immune epithelial responses that may contribute to more severe infections by HMPV and RSV.

Structure and Function Relationships of Mucociliary Clearance in Human and Rat Airways

Mucociliary clearance is a vital defense mechanism of the human airways, protecting against harmful particles and infections. When this process fails, it contributes to respiratory diseases like chronic obstructive pulmonary disease (COPD) and asthma. While advances in single-cell transcriptomics have revealed the complexity of airway composition, much of what we know about how airway structure impacts clearance relies on animal studies. This limits our ability to create accurate human-based models of airway diseases. Here we show that the airways in female rats and in humans exhibit species-specific differences in the distribution of ciliated and secretory cells as well as in ciliary beat, resulting in significantly higher clearance effectiveness in humans. We further reveal that standard lab-grown cultures exhibit lower clearance effectiveness compared to human airways, and we identify the underlying structural differences. By combining diverse experiments and physics-based modeling, we establish universal benchmarks to assess human airway function, interpret preclinical models, and better understand disease-specific impairments in mucociliary clearance.

Correlations of mucin 5B gene polymorphisms and expression levels with the risk of onset of coal workers' pneumoconiosis

This study investigates the correlations of mucin 5B (MUC5B) rs2672794, rs2075854, and rs868903 polymorphisms and MUC5B expression level with the risk of the onset of coal workers' pneumoconiosis (CWP). Overall, 506 Han Chinese men were included in this study. Among them, 143 were healthy individuals, 132 were dust-exposed workers who underwent health monitoring periodically, and 231 were patients with CWP. The participants were categorized into the following groups based on health status: healthy, exposure, CWP stage I, and CWP stage II groups. Genotyping was performed using the MassARRAY platform, and gene expression levels were measured via real-time fluorescence quantitative polymerase chain reaction. Subsequently, the correlations of 3 single-nucleotide polymorphisms (rs2672794, rs2075854, and rs868903) and MUC5B gene expression with the risk of CWP onset were analyzed. Distributions of the rs2672794 (P = .82) and rs2075854 (P = .72) genotypes were not significantly different among the various groups. Frequencies of the CC and CT genotypes of single-nucleotide polymorphism rs868903 and the C allele of MUC5B were higher in patients with CWP than in the healthy group (P = .04). The MUC5B expression level of patients with CWP was significantly lower than those of the exposure and healthy groups (P < .001). Receiver operating characteristic curve analysis revealed that MUC5B in blood cells was a sensitive biomarker for CWP diagnosis. Significant differences were observed in MUC5B gene expression levels among different genotypes of rs868903 (P < .001), with individuals carrying the CC and CT genotypes exhibiting lower MUC5B gene expression levels than those with the TT genotype. The rs868903 polymorphism in the MUC5B gene could be associated with the susceptibility to CWP, and early monitoring would aid in identifying individuals at high risk. MUC5B might serve as a valuable early screening biomarker for CWP.

The forecasting power of the mucin-microbiome interplay in livestock respiratory diseases

Complex respiratory diseases are a significant challenge for the livestock industry worldwide. These diseases considerably impact animal health and welfare and cause severe economic losses. One of the first lines of pathogen defense combines the respiratory tract mucus, a highly viscous material primarily composed of mucins, and a thriving multi-kingdom microbial ecosystem. The microbiome-mucin interplay protects from unwanted substances and organisms, but its dysfunction may enable pathogenic infections and the onset of respiratory disease. Emerging evidence also shows that noncoding regulatory RNAs might modulate the structure and function of the microbiome-mucin relationship. This opinion paper unearths the current understanding of the triangular relationship between mucins, the microbiome, and noncoding RNAs in the context of respiratory infections in animals of veterinary interest. There is a need to look at these molecular underpinnings that dictate distinct health and disease outcomes to implement effective prevention, surveillance, and timely intervention strategies tailored to the different epidemiological contexts.

CFTR expression decreases with age in several airway cell types

The mucociliary clearance (MC) system is a vital host defense against infection in the lung. MC system function is dependent on ciliary density, structure, and function and airway surface liquid (ASL) composition and hydration. Animal and human studies indicate that MC rate decreases with age which may contribute to the increased rates of pulmonary infection experienced by older people. The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene encodes an anion channel on epithelial surfaces that plays a key role in maintaining ASL hydration. Failure or dysfunction of CFTR could result in the dehydration of airway mucus, depressing MC. Here we use two available databases including bulk (GTEx) and single-cell (CELLxGENE) sequencing data from the lung to determine if CFTR expression decreases with age. Bulk expression data and single-cell expression data from goblet, club, and respiratory basal cells all demonstrated patterns of decreasing CFTR expression with age. Ciliated airway cells did not. Secretory cells (including club and goblet cells) and basal cells are the largest source of CFTR expression in the airway. This indicates that changes in CFTR expression and ASL dehydration may contribute to the decreasing MC associated with aging.

Study on the complications after implantation of different types of metal stents in rabbit trachea

OBJECTIVE

To observe the complications and inflammatory responses caused by the different types of metal stents in the trachea of rabbits.

METHOD

79 rabbits were randomly divided into 4 groups and were implanted with the customized nickel-titanium alloy metal stents(fully covered metal stent: group A, bare metal stent: group B, segmented covered metal stent: group C and control group: group D). The complications (tracheal deformation, granulation tissue hyperplasia, scar hyperplasia and secretion retention) of different types of metal stents were compared by observing the anatomical and pathological specimens of dead rabbits; And the expression of inflammatory factors of different types of metal stents were compared by detecting the tissue of tracheas of dead rabbits.

RESULTS

(1)There were significant differences in the above four complications among groups A, B and C(p < 0.01). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group A were significantly higher than that in group B(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group A was significantly lower than that in group B(p < 0.0167). The incidence of scar hyperplasia in group A was significantly lower than that in group C(p < 0.0167) and there were no significant differences in other complications between these two groups(p > 0.0167). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group B were significantly lower than that in group C(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group B was significantly higher than that in group C(p < 0.0167). (2)The concentration of IL-1β in group A was higher than that in group B (p < 0.05 and foldchange>1.2).

CONCLUSION

(1)There are significant differences in complications between the fully covered metal stent, bare metal stent and segmented covered metal stent; the incidences of complications between the segmented covered metal stent and fully covered metal stent are similar. (2)Changes in different inflammatory factors can be observed between the fully covered and bare metal stent.

Scalable Extraction of Airway Mucins from Porcine Trachea

Mucins are a major component of the innate defense system in the airways and their biological functions are important to consider in pulmonary disease research. However, the available mucus models for basic research relevant to the lung can be difficult to acquire in sufficient quantity to conduct such studies. Here, we present a new strategy to isolate airway mucins from pig trachea at the milligram to gram scale for use in pulmonary disease research. Using this protocol, we were able to isolate mucins with minimal DNA contamination consisting of ~70% by weight protein. Compared to porcine gastric mucins extracted with the same procedure, the porcine tracheal extract possessed significantly greater O-linked glycoprotein (mucin) content. Particle tracking microrheology was used to evaluate the biophysical properties of porcine trachea mucins. We found porcine tracheal mucins formed a much tighter mesh network and possessed a significantly greater microviscosity compared to lab extracted porcine gastric mucins. In comparison to mucus harvested from human airway tissue cultures, we found porcine tracheal mucins also possessed a greater microviscosity suggesting these mucins can form into a gel-like material at physiological total solids concentrations. These studies establish an accessible means to isolate airway mucins from porcine trachea at large scale for use in pulmonary disease research.

The Modulation of Respiratory Epithelial Cell Differentiation by the Thickness of an Electrospun Poly-ε-Carprolactone Mesh Mimicking the Basement Membrane

The topology of the basement membrane (BM) affects cell physiology and pathology, and BM thickening is associated with various chronic lung diseases. In addition, the topology of commercially available poly (ethylene terephthalate) (PET) membranes, which are used in preclinical in vitro models, differs from that of the human BM, which has a fibrous and elastic structure. In this study, we verified the effect of BM thickness on the differentiation of normal human bronchial epithelial (NHBE) cells. To evaluate whether the thickness of poly-ε-carprolactone (PCL) mesh affects the differentiation of NHBE cells, cells were grown on thin- (6-layer) and thick-layer (80-layer) meshes consisting of electrospun PCL nanofibers using an air-liquid interface (ALI) cell culture system. It was found that the NHBE cells formed a normal pseudostratified epithelium composed of ciliated, goblet, and basal cells on the thin-layer PCL mesh; however, goblet cell hyperplasia was observed on the thick-layer PCL mesh. Differentiated NHBE cells cultured on the thick-layer PCL mesh also demonstrated increased epithelial-mesenchymal transition (EMT) compared to those cultured on the thin-layer PCL mesh. In addition, expression of Sox9, nuclear factor (NF)-κB, and oxidative stress-related markers, which are also associated with goblet cell hyperplasia, was increased in the differentiated NHBE cells cultured on the thick-layer PCL mesh. Thus, the use of thick electrospun PCL mesh led to NHBE cells differentiating into hyperplastic goblet cells via EMT and the oxidative stress-related signaling pathway. Therefore, the topology of the BM, for example, thickness, may affect the differentiation direction of human bronchial epithelial cells.

Dissecting the MUC5AC/ANXA2 signaling axis: implications for brain metastasis in lung adenocarcinoma

Non-small cell lung carcinoma (NSCLC) exhibits a heightened propensity for brain metastasis, posing a significant clinical challenge. Mucin 5ac (MUC5AC) plays a pivotal role in the development of lung adenocarcinoma (LUAD); however, its role in causing brain metastases remains unknown. In this study, we aimed to investigate the contribution of MUC5AC to brain metastasis in patients with LUAD utilizing various brain metastasis models. Our findings revealed a substantial increase in the MUC5AC level in LUAD brain metastases (LUAD-BrM) samples and brain-tropic cell lines compared to primary samples or parental control cell lines. Intriguingly, depletion of MUC5AC in brain-tropic cells led to significant reductions in intracranial metastasis and tumor growth, and improved survival following intracardiac injection, in contrast to the observations in the control groups. Proteomic analysis revealed that mechanistically, MUC5AC depletion resulted in decreased expression of metastasis-associated molecules. There were increases in epithelial-to-mesenchymal transition, tumor invasiveness, and metastasis phenotypes in tumors with high MUC5AC expression. Furthermore, immunoprecipitation and proteomic analysis revealed a novel interaction of MUC5AC with Annexin A2 (ANXA2), which activated downstream matrix metalloproteases and facilitated extracellular matrix degradation to promote metastasis. Disrupting MUC5AC-ANXA2 signaling with a peptide inhibitor effectively abrogated the metastatic process. Additionally, treatment of tumor cells with an astrocyte-conditioned medium or the chemokine CCL2 resulted in upregulation of MUC5AC expression and enhanced brain colonization. In summary, our study demonstrates that the MUC5AC/ANXA2 signaling axis promotes brain metastasis, suggesting a potential therapeutic paradigm for LUAD patients with high MUC5AC expression.

Mucus physically restricts influenza A viral particle access to the epithelium

Prior work suggests influenza A virus (IAV) crosses the airway mucus barrier in a sialic acid-dependent manner through the actions of the viral envelope proteins, hemagglutinin and neuraminidase. However, host and viral factors that influence how efficiently mucus traps IAV remain poorly defined. In this work, we assessed how the physicochemical properties of mucus influence its ability to effectively capture IAV with altered sialic acid preference using fluorescence video microscopy and multiple particle tracking. We found an airway mucus gel layer must be produced with pores on the order of size of the virus to physically constrain IAV. Sialic acid binding by IAV also improves mucus trapping efficiency, but interestingly, sialic acid preferences had little impact on the fraction of IAV particles expected to penetrate the mucus barrier. Together, this work provides new insights on mucus barrier function toward IAV with important implications on innate host defense and interspecies transmission.

STRUCTURE-FUNCTION RELATIONSHIPS OF MUCOCILIARY CLEARANCE IN HUMAN AIRWAYS

Our study focuses on the intricate connection between tissue-level organization and ciliated organ function in humans, particularly in understanding the morphological organization of airways and their role in mucociliary clearance. Mucociliary clearance is a key mechanical defense mechanism of human airways, and clearance failure is associated with many respiratory diseases, including chronic obstructive pulmonary disease (COPD) and asthma. While single-cell transcriptomics have unveiled the cellular complexity of the human airway epithelium, our understanding of the mechanics that link epithelial structure to clearance function mainly stem from animal models. This reliance on animal data limits crucial insights into human airway barrier function and hampers the human-relevant in vitro modeling of airway diseases. This study, for the first time, maps the distribution of ciliated and secretory cell types along the airway tree in both rats and humans, noting species-specific differences in ciliary function and elucidates structural parameters of airway epithelia that predict clearance function in both native and in vitro tissues alike. By uncovering how tissue organization influences ciliary function, we can better understand disruptions in mucociliary clearance, which could have implications for various ciliated organs beyond the airways.

Active nanoparticle targeting of MUC5AC ameliorates therapeutic outcome in experimental colitis

Inflammatory bowel diseases (IBDs), which include Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory diseases of the gastrointestinal tract and are characterized by chronic recurrent ulceration of the bowels. Colon-targeted drug delivery systems (DDS) have received significant attention for their potential to treat IBD by improving the inflamed tissue selectivity. Herein, antiMUC5AC-decorated drug loaded nanoparticles (NP) are suggested for active epithelial targeting and selective adhesion to the inflamed tissue in experimental colitis. NPs conjugated with antiMUC5AC (anti-MUC5) were tested for their degree of bioadhesion with HT29-MTX cells by comparison with non-targeted BSA-NP conjugates. In vivo, the selectivity of bioadhesion and the influence of ligand density in bioadhesion efficiency as well as the therapeutic benefit for glucocorticoid loaded anti-MUC5-NP were studied in a murine colitis model. Quantitative adhesion analyses showed that anti-MUC5-conjugated NP exhibited a much higher binding and selectivity to inflamed tissue compared to PNA-, IgG1- and BSA-NP conjugates used as controls. This bioadhesion efficiency was found to be dependent on the ligand density, present at the NP surface. The binding specificity between anti-MUC5 ligand and inflamed tissues was confirmed by fluorescence imaging. Both anti-MUC5-NP and all other glucocorticoid containing formulations led to a significant mitigation of the experimental colitis, as became evident from the substantial reduction of myeloperoxidase activity and pro-inflammatory cytokine concentrations (TNF-α, IL-1β). Targeted NP by using anti-MUC5 appears to be a very promising tool in future treatment of various types of local disorders affecting the gastro-intestinal tract but not limited to colitis.

Combination treatment to improve mucociliary transport of Pseudomonas aeruginosa biofilms

People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory infections that are difficult to treat due in part to the accumulation of hyperconcentrated mucus within the airway. Mucus accumulation and obstruction promote chronic inflammation and infection and reduce therapeutic efficacy. Bacterial aggregates in the form of biofilms exhibit increased resistance to mechanical stressors from the immune response (e.g., phagocytosis) and chemical treatments including antibiotics. Herein, combination treatments designed to disrupt the mechanical properties of biofilms and potentiate antibiotic efficacy are investigated against mucus-grown Pseudomonas aeruginosa biofilms and optimized to 1) alter biofilm viscoelastic properties, 2) increase mucociliary transport rates, and 3) reduce bacterial viability. A disulfide bond reducing agent (tris(2-carboxyethyl)phosphine, TCEP), a surfactant (NP40), a biopolymer (hyaluronic acid, HA), a DNA degradation enzyme (DNase), and an antibiotic (tobramycin) are tested in various combinations to maximize biofilm disruption. The viscoelastic properties of biofilms are quantified with particle tracking microrheology and transport rates are quantified in a mucociliary transport device comprised of fully differentiated primary human bronchial epithelial cells. The combination of the NP40 with hyaluronic acid and tobramycin was the most effective at increasing mucociliary transport rates, decreasing the viscoelastic properties of mucus, and reducing bacterial viability. Multimechanistic targeting of biofilm infections may ultimately result in improved clinical outcomes, and the results of this study may be translated into future in vivo infection models.

Impact of mucus modulation by N-acetylcysteine on nanoparticle toxicity

Human respiratory mucus is a biological hydrogel that forms a protective barrier for the underlying epithelium. Modulation of the mucus layer has been employed as a strategy to enhance transmucosal drug carrier transport. However, a drawback of this strategy is a potential reduction of the mucus barrier properties, in particular in situations with an increased exposure to particles. In this study, we investigated the impact of mucus modulation on its protective role. In vitro mucus was produced by Calu-3 cells, cultivated at the air-liquid interface for 21 days and used for further testing as formed on top of the cells. Analysis of confocal 3D imaging data revealed that after 21 days Calu-3 cells secrete a mucus layer with a thickness of 24 ± 6 μm. Mucus appeared to restrict penetration of 500 nm carboxyl-modified polystyrene particles to the upper 5-10 μm of the layer. Furthermore, a mucus modulation protocol using aerosolized N-acetylcysteine (NAC) was developed. This treatment enhanced the penetration of particles through the mucus down to deeper layers by means of the mucolytic action of NAC. These findings were supported by cytotoxicity data, indicating that intact mucus protects the underlying epithelium from particle-induced effects on membrane integrity. The impact of NAC treatment on the protective properties of mucus was probed by using 50 and 100 nm amine-modified and 50 nm carboxyl-modified polystyrene nanoparticles, respectively. Cytotoxicity was only induced by the amine-modified particles in combination with NAC treatment, implying a reduced protective function of modulated mucus. Overall, our data emphasize the importance of integrating an assessment of the protective function of mucus into the development of therapy approaches involving mucus modulation.

Combination Treatment to Improve Mucociliary Transport of Pseudomonas aeruginosa Biofilms

People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory infections that are difficult to treat due in part to the accumulation of hyperconcentrated mucus within the airway. Mucus accumulation and obstruction promote chronic inflammation and infection and reduce therapeutic efficacy. Bacterial aggregates in the form of biofilms exhibit increased resistance to mechanical stressors from the immune response (e.g., phagocytosis) and chemical treatments including antibiotics. Herein, combination treatments designed to disrupt the mechanical properties of biofilms and potentiate antibiotic efficacy are investigated against mucus-grown Pseudomonas aeruginosa biofilms and optimized to 1) alter biofilm viscoelastic properties, 2) increase mucociliary transport rates, and 3) reduce bacterial viability. A disulfide bond reducing agent (tris(2-carboxyethyl)phosphine, TCEP), a surfactant (NP40), a biopolymer (hyaluronic acid, HA), a DNA degradation enzyme (DNase), and an antibiotic (tobramycin) are tested in various combinations to maximize biofilm disruption. The viscoelastic properties of biofilms are quantified with particle tracking microrheology and transport rates are quantified in a mucociliary transport device comprised of fully differentiated primary human bronchial epithelial cells. The combination of the NP40 with hyaluronic acid and tobramycin was the most effective at increasing mucociliary transport rates, decreasing the viscoelastic properties of mucus, and reducing bacterial viability. Multimechanistic targeting of biofilm infections may ultimately result in improved clinical outcomes, and the results of this study may be translated into future in vivo infection models.

Mucus Hypersecretion in Chronic Obstructive Pulmonary Disease and Its Treatment

Most patients diagnosed with chronic obstructive pulmonary disease (COPD) present with hallmark features of airway mucus hypersecretion, including cough and expectoration. Airway mucus function as a native immune system of the lung that severs to trap particulate matter and pathogens and allows them to clear from the lung via cough and ciliary transport. Chronic mucus hypersecretion (CMH) is the main factor contributing to the increased risk of morbidity and mortality in specific subsets of COPD patients. It is, therefore, primarily important to develop medications that suppress mucus hypersecretions in these patients. Although there have been some advances in COPD treatment, more work remains to be done to better understand the mechanism underlying airway mucus hypersecretion and seek more effective treatments. This review article discusses the structure and significance of mucus in the lungs focusing on gel-forming mucins and the impacts of CMH in the lungs. Furthermore, we summarize the article with pharmacological and nonpharmacological treatments as well as novel and interventional procedures to control CMH in COPD patients.