LSC - 2021 - Effect of mTOR inhibition in a 3D in vitro model of alveolar epithelium and epithelial regeneration

Abstract

Background: Type 2 alveolar epithelial cells (AEC2) are stem cells of the lung alveoli. Impaired renewal capacity of AEC2, the persistence of extracellular matrix producing myofibroblasts and the highly dysregulated cross-talk between these two cell types are key drivers in idiopathic pulmonary fibrosis (IPF). The potent profibrotic mediator TGFß1 has been widely implicated in IPF pathogenesis. We have recently reported a key role for rapamycin-insensitive mTORC1 (mechanistic target of rapamycin complex 1) signalling in mediating TGFß1-induced collagen deposition in primary human lung fibroblasts (pHLF), providing evidence supporting ATP-competitive mTOR inhibition (mTORi) as an anti-fibrotic strategy.

Aims: To investigate the potential impact of mTORi on the alveolar epithelium and on epithelial regenerative capacity in the IPF lung.

Methods and Results: We used a 3D in vitro model in which human alveolospheres were co-cultured with pHLF. When AEC2 were seeded with pHLFs pre-treated with TGFß1 alone (p=0.0145), with the partial mTOR1 inhibitor rapamycin (100 nM) with (p

Repeated treatment of AEC2 and pHLF co-cultures with mTORi at days 1, 2.5, 5 and 10 post-seeding completely prevented alveolosphere formation at 1 µM and 300 nM, and significantly reduced their number at 100nM (p

Conclusions: These data suggest that fine modulation of TGFß1-mTOR inhibition may be required in order to reduce collagen deposition without negatively impacting the regenerative capacity of the alveolar epithelium in IPF.