Human iPSC-derived alveolar and airway epithelial cells can be cultured at air-liquid interface and express SARS-CoV-2 host factors

Authors: Abo et al.

Link to paper: https://doi.org/10.1101/2020.06.03.132639

Journal/ Pre-Print: bioRxiv

Tags: Cell Biology, Gut, Stem cells

Research Highlights

1. Comparison of RNA seq data of key alveolar epithelial type 2 (AT2) genes from primary human adult AT2s and induced pluripotent stem cell (iPSC) derived AT2 (iAT2s) with 150 lung cancer cell lines (including Calu-3, A549 and H1299) revealed key lung epithelial transcripts are missing in cancer cell lines previously used to study SARS-CoV-2 infection (e.g. NKX2-1)

2. iAT2 cells cultured in an air-liquid interface (ALI) culture maintained AT2 like identity (shown by scRNA seq)

3. iAT2s and iAT2s cultured in ALI express ACE2 and TMPRSS2 however in a reduced manner compared to primary AT2s

Summary 

The authors describe the development of human induced pluripotent stem cells (iPSCs) derived alveolar epithelial type 2 (iAT2) cells. These iAT2 cells were cultured in an air-liquid interface (ALI) culture and were shown to resemble primary AT2 cells on a transcriptional level. iAT2 cells cultured in ALI were compared to previously described iPSC-derived airway basal cells (iBCs) cultured in ALI and both expressed ACE2 and TMPRSS2, important factors for SARS-CoV-2 infection. The iAT2 and iBC organoid cultures therefore provide a useful tool in studying the infection biology of SARS-Cov-2 of the lung epithelium. 

Impact for SARS-CoV2/COVID19 research efforts

Understand the virology and/or cell biology of SARS-CoV2/COVID19

Develop a vaccine for SARS-CoV2/COVID19

Study Type

· In silico study / bioinformatics study

· In vitro study

Strengths and limitations of the paper

Novelty: The authors report an iPS- derived alveolar type 2 epithelial cells that could be cultured in a 2D air liquid interface.

Standing in the field: While the cell culture model and technique is novel, it does not provide new information about COVID-19 pathogenesis. Instead it provides contributing data towards existing literature, of using cell culture models as an essential tool to study COVID-19 pathogenesis

Appropriate statistics: How statistical analysis was performed is not stated in the methods

Viral model used: no virus was used

Translatability: iAST2 ALI culture could be used to model SARS-CoV-2 infection, however the differentiation of human iPSCs to iAST2 cells is time and labour intensive

Main limitations:

· Figure 1: colour coding of ethnicity, sex and source makes it hard to distinguish different samples

· Figure 3F: on which day of the culture were the iAT2 analysed?

· Figure 6B: more biological replicates would be needed to draw conclusions as only one primary human colon sample was used as ctrl, however authors state that these are preliminary results