Characterization and functional assessment of lung epithelial cells derived from embryonic stem cells

Alveolar epithelial type II cells participate in a host of critical activities in the distal lung including surfactant secretion, transepithelial ion transport and bacterial clearance. Preterm infants, and infants diagnosed with pulmonary hypoplasia, are born with an insufficient quantity of these cells and suffer from complications such as respiratory distress and a high risk of mortality. Cell-based therapy is emerging as a promising avenue to treat lung disease, but remains relatively unstudied for treatment of preterm lung disorders. No current methods exist for obtaining a sufficient quantity of these cells from patient biopsies since in vitro expansion is limited. A viable alternative is to derive these cells from a pluripotent cell source. ^ Using mouse embryonic stem cells, we model differentiation of uncommitted cells to alveolar epithelial type II-like cells by recapitulating developmental cues responsible for their commitment in vivo. Still, differentiated cultures of embryonic stem cells can be highly heterogeneous and present a challenge for studying the cell type of interest. An ideal approach would be to purify a population of lung epithelial cells from a heterogeneous culture to ensure a high proportion of desirable cell types for investigation. Importantly, we must demonstrate that these ES-derived cells are similar to alveolar epithelial cells both in appearance and function.^ Here, I will argue the benefit of using embryonic stem-derived cells as a source of functional alveolar epithelial type II-like cells. I begin by explaining the potential use and benefits of cell-based therapy to treat lung disease, considering clinically useful cell sources and experimental models of pulmonary hypoplasia. Next, I describe the differentiation of mouse ES cells to definitive endoderm and lung epithelial cells using defined medium composition. I refine the procedure by incorporating synthetic small molecules in place of recombinant growth factors, and demonstrate their ability to prime mouse ES cells for lung epithelial differentiation. I show that heterogeneous cells can be enriched for markers of lung epithelial differentiation. Finally, I report on the progress in modifying a renal capsule allograft assay for the validation of ES-derived cells as functional lung epithelial cells.