Impaired Wound Healing of Alveolar Lung Epithelial Cells in a Breathing Lung-On-A-Chip

TLDR

The alveolar region remodels in diseases such as IPF, where repetitive microinjuries and abnormal repair drive disease onset, yet the impact of physiological strain levels (5–12%) on this process remains unclear. The study investigates how mechanical strain affects wound healing in alveolar epithelial cells. Using a breathing lung‑on‑a‑chip, confluent alveolar epithelial cells were starved, scratched, and their 24‑hour wound healing measured under varying rhHGF doses and cyclic mechanical stretch. The assay showed that physiological cyclic stretch (10% strain) impairs alveolar epithelial wound healing, an effect partially rescued by rhHGF, demonstrating the chip’s utility for studying complex cellular interactions.

Abstract

The lung alveolar region experiences remodeling during several acute and chronic lung diseases, as for instance idiopathic pulmonary fibrosis (IPF), a fatal disease, whose onset is correlated with repetitive microinjuries to the lung alveolar epithelium and abnormal alveolar wound repair. Although a high degree of mechanical stress (>20% linear strain) is thought to induce IPF, the effect of lower, physiological levels of strain (5–12% linear strain) on IPF pathophysiology remains unknown. In this study, we examined the influence of mechanical strain on alveolar epithelial wound healing. For this purpose, we adopted the "organ-on-a-chip" approach, which provides the possibility of reproducing unique aspects of the in vivo cellular microenvironment, in particular its dynamic nature. Our results provide the first demonstration that a wound-healing assay can be performed on a breathing lung-on-a-chip equipped with an ultra-thin elastic membrane. We cultured lung alveolar epithelial cells to confluence, the cells were starved for 24 h, and then wounded by scratching with a standard micropipette tip. Wound healing was assessed after 24 h under different concentrations of recombinant human hepatic growth factor (rhHGF) and the application of cyclic mechanical stretch. Physiological cyclic mechanical stretch (10% linear strain, 0.2 Hz) significantly impaired the alveolar epithelial wound-healing process relative to culture in static conditions. This impairment could be partially ameliorated by administration of rhHGF. This proof-of-concept study provides a way to study of more complex interactions, such as a co-culture with fibroblasts, endothelial cells, or immune cells, as well as the study of wound healing at an air–liquid interface.