Tridimensional imaging reveals continuity and transition of remodelled epithelial structures in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterised by a heterogeneous remodelling of the lung parenchyma. The structure and composition of remodelled epithelial structures remain partially elusive. Two subsets of alveolar-basal intermediate cells (ABI1 and ABI2) were characterised in vitro and observed in IPF explants. However, their presence and distribution within the tissue are unclear in the early stage of the disease. This study aims to explore the distribution of ABI, leverage 3D imaging to unravel the architecture of remodelled epithelium and identify if aberrant epithelial cells are associated with IPF severity. IPF biopsies and explants were stained to perform neighbourhood analysis and evaluate the cellular environment of ABI1 and ABI2 cells. Lightsheet fluorescence microscopy was performed to study the tridimensional architecture of epithelial remodelling in IPF lungs. ABI were observed in remodelled areas, with ABI1 closely associated with type 2 alveolar cells (AEC2), and ABI2 with basal cells. Higher number of ABI2 in biopsies was associated with lung function decline. Lightsheet microscopy demonstrated that so-called “AEC2 cysts” and bronchiolised areas form in fact a continuous network. We demonstrated the presence of intermediate cells within remodelled parenchyma in IPF as well as a continuity between AEC2 clusters and bronchiolised areas. Our findings highlight the complexity of epithelial remodelling in IPF.