Quantification of basal stem cell elongation and stress fiber accumulation in the pseudostratified airway epithelium during the unjamming transition

Regulation of epithelial cell jamming transition by cytoskeleton and cell-cell interactions

Multicellular systems, such as epithelial cell collectives, undergo transitions similar to those in inert physical systems like sand piles and foams. To remodel or maintain tissue organization during development or disease, these collectives transition between fluid-like and solid-like states, undergoing jamming or unjamming transitions. While these transitions share principles with physical systems, understanding their regulation and implications in cell biology is challenging. Although cell jamming and unjamming follow physics principles described by the jamming diagram, they are fundamentally biological processes. In this review, we explore how cellular processes and interactions regulate jamming and unjamming transitions. We begin with an overview of how these transitions control tissue remodeling in epithelial model systems and describe recent findings of the physical principles governing tissue solidification and fluidization. We then explore the mechanistic pathways that modulate the jamming phase diagram axes, focusing on the regulation of cell fluctuations and geometric compatibility. Drawing upon seminal works in cell biology, we discuss the roles of cytoskeleton and cell-cell adhesion in controlling cell motility and geometry. This comprehensive view illustrates the molecular control of cell jamming and unjamming, crucial for tissue remodeling in various biological contexts.

A gel-coated air-liquid-interface culture system with tunable substrate stiffness matching healthy and diseased lung tissues

Since its invention in the late 1980s, the air-liquid-interface (ALI) culture system has been the standard in vitro model for studying human airway biology and pulmonary diseases. However, in a conventional ALI system, cells are cultured on a porous plastic membrane that is much stiffer than human airway tissues. Here, we develop a gel-ALI culture system by simply coating the plastic membrane with a thin layer of hydrogel with tunable stiffness matching that of healthy and fibrotic airway tissues. We determine the optimum gel thickness that does not impair the transport of nutrients and biomolecules essential to cell growth. We show that the gel-ALI system allows human bronchial epithelial cells (HBECs) to proliferate and differentiate into pseudostratified epithelium. Furthermore, we discover that HBECs migrate significantly faster on hydrogel substrates with stiffness matching that of fibrotic lung tissues, highlighting the importance of mechanical cues in human airway remodeling. The developed gel-ALI system provides a facile approach to studying the effects of mechanical cues in human airway biology and in modeling pulmonary diseases.NEW & NOTEWORTHY In a conventional ALI system, cells are cultured on a plastic membrane that is much stiffer than human airway tissues. We develop a gel-ALI system by coating the plastic membrane with a thin layer of hydrogel with tunable stiffness matching that of healthy and fibrotic airway tissues. We discover that human bronchial epithelial cells migrate significantly faster on hydrogel substrates with pathological stiffness, highlighting the importance of mechanical cues in human airway remodeling.

Pulling the strings on solid-to-liquid phase transitions in cell collectives

Cell collectives must dynamically adapt to different biological contexts. For instance, in homeostatic conditions, epithelia must establish a barrier between body compartments and resist external stresses, while during development, wound healing or cancer invasion, these tissues undergo extensive remodeling. Using analogies from inert, passive materials, changes in cellular density, shape, rearrangements and/or migration were shown to result in collective transitions between solid and fluid states. However, what biological mechanisms govern these transitions remains an open question. In particular, the upstream signaling pathways and molecular effectors controlling the key physical axes determining tissue rheology and dynamics remain poorly understood. In this perspective, we focus on emerging evidence identifying the first biological signals determining the collective state of living tissues, with an emphasis on how these mechanisms are exploited for functionality across biological contexts.

Catalase: A Potential Pharmacologic Target for Hydrogen Peroxide in the Treatment of COVID-19

BACKGROUND

Acute respiratory distress syndrome in the elderly with COVID-19 complicated by airway obstruction with sputum and mucus, and cases of asphyxia with blood, serous fluid, pus, or meconium in newborns and people of different ages can sometimes cause hypoxemia and death from hypoxic damage to brain cells, because the medical standard does not include intrapulmonary injections of oxygen-producing solutions. The physical-chemical repurposing of hydrogen peroxide from an antiseptic to an oxygen-producing antihypoxant offers hope for the development of new drugs.

METHODS

This manuscript is a meta-analysis performed according to PRISMA guidelines.

RESULTS

It is shown that replacement of the traditional acidic activity of hydrogen peroxide solutions by alkaline activity with pH 8.4 and heating the solutions to the temperature of +37 - +42 °C allows to repurpose hydrogen peroxide from antiseptics into inhalation and intrapulmonary mucolytics, pyolytics and antihypoxants releasing oxygen. The fact is that warm alkaline hydrogen peroxide solution (WAHPS) in local interaction with sputum, mucus, pus, blood and meconium provides optimal conditions for the metabolism of hydrogen peroxide to oxygen gas under the action of the enzyme catalase, always present in these tissues. It was established that WAHPS liquefies these biological masses due to alkaline saponification of lipid and protein-lipid complexes and simultaneously transforms dense masses into soft oxygen foam due to active enzymatic metabolism of hydrogen peroxide to oxygen gas, the rapidly appearing bubbles of which are formed by the type of "cold boiling" and literally explode these masses. The results of the first experiments showed that inhalation and intrapulmonary injections of WAHPS can significantly optimize the treatment of suffocation and hypoxemia.

DISCUSSION

The results showed that catalase, which is found in sputum, mucus, pus, and blood, may be a target for localized WAHPS because this enzyme provides an intensive metabolism of hydrogen peroxide to oxygen gas up to the formation of the cold boiling process.

CONCLUSION

These data provide a new perspective way for intrapulmonary drugs and new technologies for the emergency increase of blood oxygenation through the lungs in asphyxia with thick sputum, mucus, pus, meconium and blood.