Culture conditions differentially regulate the inflammatory niche and cellular phenotype of tracheobronchial basal stem cells.

Bronchial epithelial cells derived from the tracheobronchial regions of human airways (HBECs) provide a valuable in vitro model for studying pathological mechanisms and evaluating therapeutics. This cell population comprises a mixed population of basal cells (BCs), the predominant stem cell in airways capable of both self-renewal and functional differentiation. Despite their potential for regenerative medicine, BCs exhibit significant phenotypic variability in culture. To investigate how culture conditions influence BC phenotype and function, we expanded three independent BC isolates in three media: airway epithelial cell growth medium (AECGM), dual-SMAD inhibitor (DSI)-enriched AECGM, and PneumaCult Ex plus (PEx+). Analysis through RNA sequencing, immune assays, and impedance measurements revealed that PEx+ media significantly drove cell proliferation and a broad proinflammatory phenotype in BCs. In contrast, BCs expanded in AECGM and displayed increased expression of structural and extracellular matrix components at higher passage. AECGM increased expression of some cytokines at high passage, whereas DSI suppressed inflammation implicating the involvement TGF-β in BC inflammatory processes. Differentiation capacity of BCs declined with time in culture irrespective of expansion media. This was associated with an increase in PLUNC expressing secretory cells in AECGM and PEx+ media consistent with the known immune modulatory role of PLUNC in the airways. These findings highlight the profound impact of media conditions on inflammatory niche established by, and function of, in vitro expanded BCs. The broad proinflammatory phenotype driven by PEx+ media, in particular, should be considered in the development of cell-based models for airway diseases and therapeutic applications.