Human lung BSC and AT2 populations have progenitor activity.

<p>(A) Representative images of colonies grown from lung epithelial subsets in a 3-D in vitro assay; a 64-y-old male current smoker. Black scale bar = 500 μm; white scale bar = 100 μm. (B) Representative immunofluorescence staining of keratin 5 (KRT5) (a 57-y-old male exsmoker) and pro-surfactant protein C (proSFTPC) (a 54-y-old female exsmoker) in BSC and AT2 colonies. <i>n</i> = 13 patients; 39–78 y old; current, ex-, and never smokers. Scale bar = 100 μm. (C) Colony-forming capacity of sorted lung epithelial cells; <i>n</i> = 24 patients for proximal lung samples and <i>n</i> = 27 patients for distal lung samples; 21–85 y old; male and female; never, ex-, and current smokers. Student’s <i>t</i> test. (D) Representative images of human BSC and AT2 cell colonies from an exsmoker patient (a 57-y-old male) compared to a never-smoker patient (a 71-y-old female). Scale bar = 500 μm. (E) Linear regression analysis of the number of human BSCs (r² = 0.2) or AT2 colonies (r² = 0.3) versus number of years of patient tobacco smoking. <i>n</i> = 21 patients for basal colonies and <i>n</i> = 23 patients for AT2 colonies, 21–83 y old, male and female. The underlying data for panels C and E can be found in the <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2000731#pbio.2000731.s009" target="_blank">S1 Data</a> file.