Airways mechanical damage as profound mechanism of asthma
Movie S1. Unprimed bronchioles mildly respond to MCH treatment. Ex vivo lung slice from a healthy control mouse treated with 0.5 g/mL MCH and imaged live by brightfield for 15 minutes, with arrowheads marking extruding cells.
Movie S2. HDM priming airways results in pathological crowding and extrusion. Lung slice from HDM B primed mouse was imaged live for 15 min of a 0.5 g/mL MCH challenge.
Movie S3. OVA priming airways results in pathological crowding and extrusion. Lung slice from OVA A primed mouse was treated with 0.5 g/mL MCH and imaged live for 30 min.
Movie S4. Epithelial extrusions seen in larger HDM primed airways treated with MCH. Large airway from a HDM primed mouse treated with 0.5 g/mL MCH for 15 min (red arrowheads highlighting epithelial cells extruding above the monolayer).
Movie S5. Unjamming of epithelia following bronchoconstriction. Large airway from a HDM primed mouse treated with 0.5 g/mL MCH for 15 min, where epithelial cells in the top bronchiole move together in a sheet, an occasional occurrence.
Movie S6. Albuterol does not reverse epithelial cell extrusion during an attack. A medium size airway from a five-week HDM-primed mouse treated with MCH for 15 min, then MCH with albuterol (ALB) for an additional 15 min. Red arrowheads highlight sites where epithelial sheet detaches from the underlying airway smooth muscle.
Movie S7. Gadolinium protects airway epithelium even after an attack begins. Airways from a five-week HDM-primed mouse treated with MCH for 15 min and then with MCH+ALB+Gd3+ for another 15 min. Red arrowheads pointing to areas of epithelial detachment, then Gd3+-induced reattachment by the end of the treatment, shown with blue arrowheads.
Movie S8. Gadolinium protects airway epithelium even after an attack begins. The uncropped Supplemental Movie 7 & Fig. 2H.
Movie S9. Gadolinium does not appear to negatively impact mouse behavior. Mice acutely treated with gadolinium on day 1 demonstrate normal grooming and social behavior. 13
Movie S10. Gadolinium does not appear to negatively impact mouse behavior. Mice acutely treated with gadolinium for 5 consecutive days demonstrate normal grooming and social behavior.
Movie S11. Mechanically-induced mucus secretion in ex vivo slices by live WGA-350 imaging. Inset of a bronchiole from a three-week HDM-primed lung pre-treated with 10 μg/mL WGA before imaging for 15 min with 0.5 g/mL MCH, showing mucus (as indicated by blue WGA) secreted from the epithelium in response to bronchoconstriction.
Movie S12. Mechanically-induced mucus secretion in ex vivo slices by live WGA-350 imaging. A bronchiole from a three-week HDM-primed lung was pre-treated with 10 μg/mL WGA before imaging for 15 min with 0.5 g/mL MCH, demonstrating mucus (blue WGA) secreted from the epithelium in response to bronchoconstriction.
Movie S13. Gadolinium pretreatment prevents mechanically induced mucus secretion. Ex vivo lung slices from three-week HDM-primed mice were pretreated with WGA and Gd3+ (10 min) then given 0.5 g/mL MCH (t=00:00) and imaged live for 15 min, demonstrating that most mucus is retained in the epithelium during bronchoconstriction.
Abstract
Asthma is deemed an inflammatory disease, yet the defining diagnostic feature is mechanical bronchoconstriction. We previously discovered a conserved process called cell extrusion that drives homeostatic epithelial cell death when cells become too crowded. In this work, we show that the pathological crowding of a bronchoconstrictive attack causes so much epithelial cell extrusion that it damages the airways, resulting in inflammation and mucus secretion in both mice and humans. Although relaxing the airways with the rescue treatment albuterol did not affect these responses, inhibiting live cell extrusion signaling during bronchoconstriction prevented all these features. Our findings show that bronchoconstriction causes epithelial damage and inflammation by excess crowding-induced cell extrusion and suggest that blocking epithelial extrusion, instead of the ensuing downstream inflammation, could prevent the feed-forward asthma inflammatory cycle.
Dustin C. Bagley et al. Bronchoconstriction damages airway epithelia by crowding-induced excess cell extrusion. Science 384, 66 (2024)
DOI: 10.1126/science.adk2758