Abstract
Lung alveolar structure and function are maintained by subsets of alveolar type II stem cells (AT2s), but there is a need for characterization of these subsets and their associated niches. Here, we report a CD44(high) subpopulation of AT2s characterized by increased expression of genes that regulate immune signaling even during steady-state homeostasis. Disruption of one of these immune regulatory transcription factor STAT1 impaired the stem cell function of AT2s. CD44(high) cells were preferentially located near macro- blood vessels and a supportive niche constituted by LYVE1(+) endothelial cells, adventitial fibroblasts, and accumulated hyaluronan. In this microenvironment, CD44(high) AT2 cells were more responsive to transformation by KRAS than general AT2 cells. Moreover, after bacterial lung injury, there was a significant increase of CD44(high) AT2s and niche components distributed throughout the lung parenchyma. Taken together, CD44(high) AT2 cells and their perivascular niche regulate tissue homeostasis and tumor formation.