Advancing lung science with primary adult alveolar organoids: Regeneration, disease modeling, and lung macrophage-epithelial interactions

Respiratory diseases rank as the third leading global cause of death, and their prevalence is on the rise. Despite marked differences in lung biology between humans and mice, much of the fundamental research in the respiratory field relies on murine models. In recent years, organoids have emerged as a promising in vitro model closely resembling human physiology. While induced pluripotent stem cell- and airway-derived organoids have been in use for some time, the development of primary alveolar organoids has presented a more significant challenge. In this study, we introduce an optimized primary adult feeder-free alveolar organoid model, cultured under defined serum-free conditions. These organoids can be expanded long-term and differentiated to alveolar type 1 and type 2 cells. Additionally, we can harness next-generation CRISPR/Cas9-technology to genetically engineer and clonally expand the organoids. This allows us to model chronic lung diseases with isogenic human organoid lines. Moreover, our platform enables us to explore the impact of the inflammatory milieu often associated with chronic lung disease through the introduction of cytokines. We can also study the interactions between lung macrophages and epithelial cells in both healthy and disease states. Altogether, this model provides an invaluable framework for investigating diverse facets of human lung regeneration and lung diseases in a fully defined, physiologically relevant in vitro setting.