Neutrophil migration in the lung is altered by alveolar collapse and stretch

Heterogeneous alveolar collapse is prevalent in inflammatory lung conditions such as chronic obstructive pulmonary disease, acute respiratory distress syndrome, and pneumonia. Although neutrophil-released proteases contribute to the tissue remodeling that leads to alveolar collapse, how this altered mechanical environment in turn affects neutrophil migration remains largely unexplored.

In this study, we investigate how alveolar collapse and stretch influence neutrophil migration and identify the mechanical and biochemical factors that govern regional migration differences.

We developed a novel precision-cut lung slice platform that generates collapsed vs non-collapsed regions within the same slice. Neutrophils in both regions were longitudinally imaged for up to 5 hours to quantify motility behavior. Migration mechanisms were probed using migration-related inhibitors, collagenase, and cigarette smoke extract. A crystal ribcage system, which preserves intact alveolar shape and the air-liquid interface, was also used to assess the effects of ventilation on neutrophil migration.

Neutrophil migration was faster in the collapsed region compared to not-collapsed regions. This regional difference was eliminated by Rho-associated protein kinase (ROCK) inhibition, which selectively increased migration speed in the non-collapsed region. The regional difference persisted with the addition of collagenase and cigarette smoke extract, both of which significantly increased the migration speed in both regions. In the crystal ribcage, the preserved air-liquid interface and ventilation together enhanced neutrophil migration compared with a collapsed lung.

Alveolar collapse and stretch facilitate neutrophil migration, indicating the role of localized tissue remodeling in driving neutrophil activity and further disease progression.