A method of generating alveolar organoids using human pluripotent stem cells.

The lung consists of branched structures that are anatomically, developmentally and functionally divided into airway and alveolar regions. Each region contributes to lung-specific functions involving a defense system and gas exchange, and their dysfunction can cause fatal lung diseases. In the alveolar region, the cuboidal alveolar type 2 (AT2) cells account for 90% of the alveolar epithelial cells and serve as the tissue stem cells secreting pulmonary surfactant, and flattened alveolar type I (AT1) cells cover most of the alveolar surface directly contributing to gas exchange adjacent to capillary vessels. It has been difficult to culture alveolar epithelial cells in vitro, as the lineage-specific features of those cells are rapidly lost in a conventional two-dimensional culture setting. The culture of alveolar organoids (AOs) is an emerging technique that can help maintain the features of alveolar epithelial cells in vitro, and their application to human disease modeling is eagerly awaited. We herein describe our method of generating and culturing alveolar epithelial cells and AOs derived from human induced pluripotent stem cells (iPSCs). iPSCs derived from lung disease patients, including those with rare genetic diseases, will make help elucidate the disease mechanism and hopefully identify therapeutic targets.