Isolation and characterization of basal cells from human upper respiratory epithelium

Cellular pathways of normal and reparative differentiation of upper airway epithelium are not well understood. Of the three main cell types, basal and secretory cells are known to divide, while ciliated cells are considered terminally differentiated. Several investigations support the role of the basal cell as a progenitor cell type, but others suggest that the secretory cell can regenerate a complete mucocilliary epithelium. Thus, lineage relationships within renewing adult epithelia are still unclear. Understanding the pathways involved in upper airway epithelial cell differentiation is critical for studying injury and repair mechanisms and for developing clinical strategies for tracheal reconstruction. We undertook the current studies to determine the integrin profile of isolated human upper airway basal cells. Respiratory epithelial cells (REC) were isolated by elastase digestion, stained with FITC-labeled Griffonia simplicifolia isolectin B4 (GSI-B4), and sorted by flow cytometry. Approximately 80% of the lectin-positive cells were basal cells, as determined by morphology and cytokeratin staining. These cells expressed integrins alpha 1, alpha 2, alpha 3, alpha 5, alpha v beta 5, beta 1, beta 3, and alpha 6 beta 4, by immunohistochemistry. This is the first report to identify the integrin profile of isolated human upper airway basal cells. These basal cells could be maintained on type I collagen for at least 7 days, where they became partially confluent and retained expression of cytokeratins 5 and 14. Availability of pure populations of basal cells should permit investigations of their role in both normal and maladaptive repair of adult upper airway epithelium.