Priming airway epithelial cells with transforming growth factor-beta recapitulates the biophysical properties of asthmatic cells

Abstract

Rationale: We have previously showed that primary human bronchial epithelial (HBE) cells in air-liquid interface (ALI) culture undergo a transition from a fluid-like unjammed to a solid-like jammed state during maturation. This transition is delayed in HBE cells from asthmatic donors compared to cells from non-asthmatic donors. We tested the hypothesis that this delay is recapitulated by priming non-asthmatic cells with transforming growth factor-beta (TGF-β), a fibrotic mediator elevated in asthmatic airways. Methods: HBE cells were incubated with vehicle or TGF-β during expansion, then plated on transwells without further treatment. We quantified cell motions during maturation in ALI, and measured cell-substrate tractions and intercellular stresses exerted by these cells on soft polyacrylamide gels. We detected vimentin and E-cadherin proteins by western blot. Results: Control, unprimed HBE cells were highly mobile and unjammed at day 3 of ALI culture, but were immobile and jammed by day 7. However, TGF-β primed HBE cells remained unjammed until day 10. Compared to unprimed cells, primed cells exhibited significantly higher tractions and intercellular stresses by 1.7- and 1.5-fold, respectively. In TGF-β primed cells, the level of vimentin protein was substantially higher compared to control cells, but the level of E-cadherin protein was the same. Conclusion: Here we show that priming human airway epithelial cells with TGF-β causes a delay in the jamming transition during maturation in ALI, accompanied by increased monolayer physical forces. These findings suggest that TGF-β promotes a dysmature epithelial phenotype that delays HBE cell jamming in asthma.