Recapitulating idiopathic pulmonary fibrosis related alveolar epithelial dysfunction in a human iPSC‐derived air‐liquid interface model

Abstract

Idiopathic pulmonary fibrosis (IPF) is a fatal disease of unknown cause that is characterized by progressive fibrotic lung remodeling. An abnormal emergence of airway epithelial‐like cells within the alveolar compartments of the lung, herein termed bronchiolization, is often observed in IPF. However, the origin of this dysfunctional distal lung epithelium remains unknown due to a lack of suitable human model systems. In this study, we established a human induced pluripotent stem cell (iPSC)‐derived air‐liquid interface (ALI) model of alveolar epithelial type II (ATII)‐like cell differentiation that allows us to investigate alveolar epithelial progenitor cell differentiation in vitro. We treated this system with an IPF‐relevant cocktail (IPF‐RC) to mimic the pro‐fibrotic cytokine milieu present in IPF lungs. Stimulation with IPF‐RC during differentiation increases secretion of IPF biomarkers and RNA sequencing (RNA‐seq) of these cultures reveals significant overlap with human IPF patient data. IPF‐RC treatment further impairs ATII differentiation by driving a shift toward an airway epithelial‐like expression signature, providing evidence that a pro‐fibrotic cytokine environment can influence the proximo‐distal differentiation pattern of human lung epithelial cells. In conclusion, we show for the first time, the establishment of a human model system that recapitulates aspects of IPF‐associated bronchiolization of the lung epithelium in vitro.

Human-Based Advanced in vitro Approaches to Investigate Lung Fibrosis and Pulmonary Effects of COVID-19

“…While multicellular organoids closely capture the minute details of cell-cell and cell-ECM interactions and physiological cellular organization they lack vasculature and air-liquid interface (ALI) [( 206); Figure 2]. Recently, it has been shown that ALI promotes differentiation of human pluripotent stem cell (hPSC)-derived alveolar epithelial progenitor cells into ATII-like cells and reduces their transdifferentiation into ATI cells, which occurs in submerged cultures (207). Stimulation with a pro-fibrotic cocktail results in the loss of SPC + ATII cells paralleled by an increase in MUC5B + goblet-like cells mimicking the bronchialization process occurring in the alveoli of IPF patients (207).…”

“…Recently, it has been shown that ALI promotes differentiation of human pluripotent stem cell (hPSC)-derived alveolar epithelial progenitor cells into ATII-like cells and reduces their transdifferentiation into ATI cells, which occurs in submerged cultures (207). Stimulation with a pro-fibrotic cocktail results in the loss of SPC + ATII cells paralleled by an increase in MUC5B + goblet-like cells mimicking the bronchialization process occurring in the alveoli of IPF patients (207). However, these models still lack biomechanical stimulation (Figure 2).…”

“…Despite accurate recapitulation of the disease phenotype and a gene expression signature of early fibrosis, the fibrotic organoids lack some major hallmarks of IPF such as activation of TGF-β signaling. Transcriptomic and histologic alterations of IPF have recently been modeled in hPSC-derived ATII-like cell cultures maintained in ALI (207). Given that alveolar epithelial progenitors, an essential contributor of aberrant wound healing, are enriched in hPSCderived models they have been suggested as suitable model to study pulmonary fibrosis (207).…”

New Perspectives on the Aberrant Alveolar Repair of Idiopathic Pulmonary Fibrosis

“…For instance, FGF-10 is essential for the survival and proliferation of epithelial stem cell like DASCs (Zuo et al, 2015;Shi et al, 2019), and it can also promote alveologenesis after lung injury (Yuan et al, 2019), while the level of FGF-10 is declined in progressive IPF patients (Chanda et al, 2016). A recent study showed that treatment with IPF-relevant cytokine cocktail (including IL-1β, TGF-β1, TNF-α, IL-8, IL-33, IL-13, IL-4, TSLP, and MCP-1) altered the differentiation direction of alveolar and small airway epithelial stem cells (Schruf et al, 2020). These evidences indicate that the lower engagement of non-AEC2 progenitor/stem cells in alveolar regeneration may also attribute to the unfavorable microenvironment in IPF lungs.…”

Development of novelin vitrohuman alveolar epithelial cell models to study distal lung biology and disease

“…When suspended in Matrigel, these cells generated structures similar to purified human AT2 cells under organotypic culture (Barkauskas et al, 2013;Zacharias et al, 2018). This morphologic property has allowed for modeling of numerous alveolar pathologies (Hiemstra et al, 2018;Heo et al, 2019;Shafa et al, 2018;Korogi et al, 2019;Leibel et al, 2019;Porotto et al, 2019;Schruf et al, 2020). However, the time and experience required to differentiate iPSCs properly towards a distal lung lineage are not trivial.…”