Rapid expansion of human epithelial stem cells suitable for airway tissue engineering

Rationale: Stem cell-based tracheal replacement represents an emerging therapeutic option for patients with otherwise untreatable airway diseases including long-segment congenital tracheal stenosis and upper airway tumors. Clinical experience suggests an urgent need to restore mucociliary function in the lungs following transplantation of tissue-engineered grafts, while pre-clinical studies show that seeding scaffolds with autologous mucosa improves regeneration. Recent data suggest that high epithelial cell seeding densities are required in regenerative medicine and existing techniques are inadequate to achieve coverage of clinically suitable grafts. Objectives: To define a scalable airway epithelial cell culture system to deliver airway epithelial cells to clinical grafts. Methods: Human respiratory epithelial cells derived from endobronchial biopsies were cultured using a combination of mitotically inactivated fibroblasts and Rho-kinase (ROCK) inhibition. Cells were analyzed using immunofluorescence, qPCR and flow cytometry to assess airway stem cell marker expression. Differentiation capacity and ciliary beat were assessed in air-liquid interface cultures. Karyotyping and an in vivo tracheal xenograft model were used to investigate the suitability of expanded cells for tracheal reconstruction. Measurements and Main Results: 3T3 feeder cells and ROCK inhibition allowed rapid expansion of airway basal stem cells. These cells were capable of multipotent airway differentiation in vitro, forming epithelia containing both ciliated and goblet lineages. Cilia were functional with normal beat frequency and pattern. Cultured cells repopulated a decellularized tracheal scaffold in a heterotopic tracheal transplantation xenograft model. Conclusions: Our method addresses the clinical need to generate large numbers of airway basal epithelial cells in the time window demanded by clinical transplantation. Matched donor human airway epithelial cells were cultured in BEGM or on a feeder layer of mitotically inactive 3T3-J2 fibroblasts with ROCK inhibition (5uM Y-27632) for one passage (7 days).