Marker expression on DKO SP cells flow sorted and cultured for 5 days. Lungs parenchyma, homogenized and digested with dispase, was incubated with Hoechst dye for 90 mins in a water bath at 37°C. After washing thrice with cold PBS, cells were flow sorted with FACS ARIA cell sorter from Becton Dickinson. The sorted Side Population cells gated from the typical arch formed in the scattergram by Hoechst positive cells were kept in ex vivo culture in ES medium with LIF and assessed for markers by FCM every day for 5 days. Percent positive cells for markers on SP cells sorted and cultured in mouse ES medium with LIF. FACsans and flow sorts were done in triplicate per sample. *P < 0.05 compared to control, averaged from three independent experiments. Abbreviations: WS, wildtype mice treated with saline; WB, wildtype mice treated with bleomycin d7; d1-5, days 1 to 5 in culture; DKOS, saline treated MMP12- gp91phox double knockout; DKOB, bleomycin-treated MMP12- gp91phox double knockout.