Use of Magnetic Nanoparticles as In Situ Mucus Property Probe

Magnetic nanoparticles (MNPs) are unique in their abilities to penetrate and interact with a wide range of liquid media. Because of their magnetic properties, MNPs can be directed to any area of interest, and interact with core structures deep inside the medium which is normally inaccessible. In this report, we investigate the behavior of MNPs in a specific biological fluid, namely in a mucus layer of air–liquid interface cultured primary normal human tracheobronchial epithelial cells. Using Fokker–Planck algorithm simulations and observing the behavior of MNPs from prior experiments, we found MNPs that are initially less than 100 nm in size, to aggregate into sizes of ~50 μm and to deviate from the expected Fokker–Planck distribution due to the mucus structure. Based on our analysis, human tracheobronchial epithelial (NHTE) cell mucus viscosity ranges from 15 Pa·s to 150 Pa·s. The results not only confirm the possible use of MNPs as a means for medical drug delivery but also underline important consequences of MNP surface modifications.

Quantifying and engineering mucus adhesion of probiotics

ABSTRACTMucus in the gastrointestinal (GI) tract is the primary point-of-interaction between humans and their gut microbiota. This not only intimates that mucus ensures protection against endogenous and ex-ogenous opportunists but provision for the human microbiota to reside and flourish. With the emergence of living therapeutics, engineered microbes can deliver and produce increasingly complex medicine, and controlling the mucoadhesive properties of different microbial chassis can dictate dose-response in a patient. Here we present a redesigned, in vitro, plate-based assay to measure the mucus adhesion of various probiotics. Cell-mucus interactions were isolated by immobilizing mucus to the plate surface. Binding parameters were derived for each probiotic strain by measuring cell adhesion over a wide range of cell concentrations, providing dose-dependent adhesion metrics. Surface proteins and cell components known to influence mucoadhesion were then heterologously expressed or altered in Lactococcus lactis MG1363 and E. coli Nissle 1917 to control mucus-binding capacity, avidity, and cooperativity.

Paneth cell extrusion and release of antimicrobial products is directly controlled by immune cell–derived IFN-γ

Paneth cells (PCs) are terminally differentiated, highly specialized secretory cells located at the base of the crypts of Lieberkühn in the small intestine. Besides their antimicrobial function, PCs serve as a component of the intestinal stem cell niche. By secreting granules containing bactericidal proteins like defensins/cryptdins and lysozyme, PCs regulate the microbiome of the gut. Here we study the control of PC degranulation in primary epithelial organoids in culture. We show that PC degranulation does not directly occur upon stimulation with microbial antigens or bacteria. In contrast, the pro-inflammatory cytokine Interferon gamma (IFN-γ) induces rapid and complete loss of granules. Using live cell imaging, we show that degranulation is coupled to luminal extrusion and death of PCs. Transfer of supernatants from in vitro stimulated iNKT cells recapitulates degranulation in an IFN-γ-dependent manner. Furthermore, endogenous IFN-γ secretion induced by anti-CD3 antibody injection causes Paneth loss and release of goblet cell mucus. The identification of IFN-γ as a trigger for degranulation and extrusion of PCs establishes a novel effector mechanism by which immune responses may regulate epithelial status and the gut microbiome.