Disulfide disruption reverses mucus dysfunction in allergic airway disease.

Airway mucus is essential for lung defense, but excessive mucus in asthma obstructs airflow, leading to severe and potentially fatal outcomes. Current asthma treatments have minimal effects on mucus, and the lack of therapeutic options stems from a poor understanding of mucus function and dysfunction at a molecular level and in vivo. Biophysical properties of mucus are controlled by mucin glycoproteins that polymerize covalently via disulfide bonds. Once secreted, mucin glycopolymers can aggregate, form plugs, and block airflow. Here we show that reducing mucin disulfide bonds disrupts mucus in human asthmatics and reverses pathological effects of mucus hypersecretion in a mouse allergic asthma model. In mice, inhaled mucolytic treatment loosens mucus mesh, enhances mucociliary clearance, and abolishes airway hyperreactivity (AHR) to the bronchoprovocative agent methacholine. AHR reversal is directly related to reduced mucus plugging. These findings establish grounds for developing treatments to inhibit effects of mucus hypersecretion in asthma.

Validation of hyaluronic acid-agar-based hydrogels as vitreous humor mimetics for in vitro drug and particle migration evaluations.

Artificial vitreous humor holds immense potential for use in in vitro intravitreal drug delivery assays. In this study, we investigated rheological properties and drug or nanoparticle migration in hyaluronic acid (HA) - agar based hydrogels and compared these characteristics with bovine vitreous humor. Gel compositions identified in literature containing HA (0.7-5.0 mg/ml) and agar (0.95-4.0 mg/ml) were classified as either high (VH), medium (VM) or low (VL) polymer load. Viscoelastic behavior was evaluated using oscillatory rheology, and migration of differently sized and charged polystyrene nanoparticles (NPs) through the different gels was determined via multiple particle tracking. Comparable rheological behaviour was observed between VL and bovine vitreous. Tracking evaluations revealed that increasing particle size and gel viscosity slowed NP migration. Additionally, 100 nm anionic NPs migrated slower than neutral NPs in VL and VM, while cationic NPs were immobile in all gels. Finally, distribution and clearance of sodium fluorescein was used to model drug mobility through the gels using a custom-built eye model. Flow and angular movement only influenced drug migration in VL and VM, but not VH. Finally, VL and VM demonstrated to have the most similar sodium fluorescein clearance to that of bovine vitreous humor. Together, these evaluations demonstrate that low viscosity HA-agar gels can be used to approximate nanoparticle and drug migration through biological vitreous humor.

Adhesive and Cohesive Peel Force Measurement of Human Airway Mucus.

In health, the high-speed airflow associated with cough represents a vital backup mechanism for clearing accumulated mucus from our airways. However, alterations in the mucus layer in cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) leads to the mucus layer adhered to the airway surfaces, representing the nidus of chronic lung infection. To understand what is different about diseased mucus and why cough clearance is defective, there is a need for techniques to quantify the strength of the interactions limiting the ability of airflow to strip mucus from the airway surface (i.e., adhesive strength) or tear mucus apart (i.e., cohesive strength). To overcome the issues with measuring these properties in a soft (i.e., low elastic modulus) mucus layer, we present here novel peel-testing technologies capable of quantifying the mucus adhesive strength on cultured airway cells and cohesive strength of excised mucus samples. While this protocol focuses on measurements of airway mucus, this approach can easily be adapted to measuring adhesive/cohesive properties of other soft biological materials.

Nanoparticle diffusion in spontaneously expectorated sputum as a biophysical tool to probe disease severity in COPD.

Perturbations in airway mucus properties contribute to lung function decline in patients with chronic obstructive pulmonary disease (COPD). While alterations in bulk mucus rheology have been widely explored, microscopic mucus properties that directly impact on the dynamics of microorganisms and immune cells in the COPD lungs are yet to be investigated.We hypothesised that a tightened mesh structure of spontaneously expectorated mucus (i.e. sputum) would contribute to increased COPD disease severity. Here, we investigated whether the mesh size of COPD sputum, quantified by muco-inert nanoparticle (MIP) diffusion, correlated with sputum composition and lung function measurements.The microstructure of COPD sputum was assessed based on the mean squared displacement (MSD) of variously sized MIPs measured by multiple particle tracking. MSD values were correlated with sputum composition and spirometry. In total, 33 samples collected from COPD or non-COPD individuals were analysed.We found that 100 nm MIPs differentiated microstructural features of COPD sputum. The mobility of MIPs was more hindered in sputum samples from patients with severe COPD, suggesting a tighter mucus mesh size. Specifically, MSD values inversely correlated with lung function.These findings suggest that sputum microstructure may serve as a novel risk factor for COPD progression and severity.