Alveolar type 2 (AT2) cells are heterogeneous cells; where specialised AT2 subpopulations within this lineage exhibit stem cell properties. However, the existence of quiescent, immature cells within the AT2 lineage, which are activated during lung regeneration, is unknown.Sftpc(CreERT2/+); tdTomato(flox/flox) mice were used for the labelling of AT2 cells and labeled subpopulations were analysed by flow cytometry, qPCR, ATAC-seq, gene arrays, pneumonectomy, and culture of precision-cut lung slides. ScRNA-seq data from human lungs were analysed.In mice, we detected two distinct AT2 subpopulations with low tdTomato level (Tom(Low)) and high tdTomato level (Tom(High)). Tom(Low) express lower level of AT2 differentiation markers, Fgfr2b and Etv5, while Tom(High), as bona fide mature AT2 cells, show higher levels of Sftpc, Sftpb, Sftpa1, Fgfr2b and Etv5 expression. ATAC-seq analysis indicates that Tom(Low) and Tom(High) constitute two distinct cell populations with specific silencing of Sftpc, Rosa26 and cell cycle gene loci in Tom(Low) Upon pneumonectomy, the number of Tom(Low) but not Tom(High) cells increases and Tom(Low) upregulate the expression of Fgfr2b, Etv5, Sftpc, Ccnd1 and Ccnd2 compared to sham. Tom(Low) cells overexpress PD-L1, an immune inhibitory membrane receptor ligand, which is used by flow cytometry to differentially isolate these two sub-populations. In the human lung, data mining of a recent scRNA-seq AT2 dataset demonstrates the existence of a PD-L1 (Pos) population. Therefore, we have identified a novel population of AT2 quiescent, immature progenitor cells in mouse that expand upon pneumonectomy and provided evidence for the existence of such cells in human.
- Ahmadvand, N.
- Khosravi, F.
- Lingampally, A.
- Wasnick, R.
- Vazquez-Armendariz, I.
- Carraro, G.
- Heiner, M.
- Rivetti, S.
- Lv, Y.
- Wilhelm, J.
- Gunther, A.
- Herold, S.
- Al Alam, D.
- Chen, C.
- Minoo, P.
- Zhang, J. S.
- Bellusci, S.
