RTK signalling promotes epithelial columnar cell shape and apical junction maintenance in human lung progenitor cells

Abstract

Multipotent epithelial progenitor cells can be expanded from human embryonic lungs as organoids. and maintained in a self-renewing state using a defined medium. The organoid cells are columnar, resembling the cell morphology of the developing lung tip epithelium in vivo. Cell shape dynamics and fate are tightly coordinated during development. We therefore used the organoid system to identify signalling pathways that maintain the columnar shape of human lung tip progenitors. We found that EGF, FGF7 and FGF10 have distinct functions in lung tip progenitors. FGF7 activates MAPK/ERK and PI3K/AKT signalling and is sufficient to promote columnar cell shape in primary tip progenitors. Inhibitor experiments show that MAPK/ERK and PI3K/AKT signalling are key downstream pathways, regulating cell proliferation, columnar cell shape and cell junctions. We identified integrin signalling as a key pathway downstream of MAPK/ERK in the tip progenitors; disrupting integrin alters polarity, cell adhesion and tight junction assembly. By contrast, stimulation with FGF10 or EGF alone is not sufficient to maintain organoid columnar cell shape. This study employs organoids to provide insight into the cellular mechanisms regulating human lung development.

Screening of factors inducing alveolar type 1 epithelial cells using human pluripotent stem cells

“…In the present study, treatment with LATS-IN-1 increased AT1 transcriptome broadly, but it alone did not thin the spheroids, consistent with recent in vivo reports that YAP/TAZ activation alone is insufficient for AT1 cell differentiation ( Penkala et al., 2021 ). PI3K/AKT inhibitors induced thinning of the cells in FD-AOs, which is consistent with the recent report that AKT inhibition shortened stem cell length in the developing lung, indicating that AKT affects cell morphology in alveolar epithelial cells and is one of the factors controlling thinning ( Liu et al., 2023 ). When dissociated AT2 cells were reseeded onto a 2D culture, the flattened morphology was achieved as well as increased AT1 cell markers ( Kanagaki et al., 2021 ).…”