Speaker
Description
The human bronchial epithelium is a dynamic barrier that forms the first line of defense against inhaled threats such as pollutants and respiratory pathogens. Its protective role mainly depends on two key cell types: i) goblet cells that secrete mucus, a viscoelastic fluid that traps foreign particles entering the human body and ii) ciliated cells, which have hair-like structures that beat in a synchronized way to generate mucus flow. This process is known as mucociliary clearance and ensures a continuous removing of dust and pathogens, supporting normal airway function.
In vitro models of human bronchial epithelium (HBE) are mainly provided by 2D culture on transwell inserts where cells are placed at the air–liquid interface to allow differentiation into ciliated and goblet cells and thus a functional bronchial epithelium. While HBE ALI cultures are traditionally considered as the gold standard, they have some limitations as a model: the 2D geometry and stiffness of the insert is not reflecting the HBE environment and the inserts hinder the imaging required to characterize accurately cells beating coordination.
Here, we engineered a 3D bronchus-like perfusable structure optimized for high-resolution live-cell imaging required for cilia beating and mucus flow analysis. The microfluidic chip contains a cylindrical lumen molded inside a chamber filled with collagen, connected to two reservoirs of culture medium. This geometry allows cells to grow at the air–liquid interface formed between the collagen hydrogel and the air inside the lumen, and the nutrients to diffuse from the reservoirs through the hydrogel. The lumen coating is chosen to grow either primary cells or induced pluripotent stem cells. The “mini-bronchus” can be alternatively be perfused with medium or air, and its diameter can be varied from 200 to 1000 microns, covering the size range for bronchioles.
This organ-on-a-chip model uniquely incorporates physiologically relevant features and will allow real-time visualization of key respiratory processes including ciliary motion, mucus transport, viral docking and entry, infection spread, and response to drug treatment within a biomechanically relevant airway environment. This platform will be used in the first place to test how exposition of the bronchial epithelial tissue to pollution can favor infection by respiratory viruses. The functionality of the tissue will be assessed thanks to the biophysical tools we previously developed to characterize cilia beating coordination, based on the tracking of cilia motion and mucus flow. On more fundamental aspects, we are investigating how the curvature of the tissue affect the cilia coordination and its typical length scales.