Fig. 2.

CD44^high type II cells show higher cell proliferation compared with CD44^low type II cells. A and B: relative expression of CDC25C (A) and cyclin B1 (CCNB1; B) in sorted CD44^high and CD44^low type II cells was analyzed using qRT-PCR. Both genes showed significantly higher expression levels in CD44^high type II cells compared with CD44^low type II cells. Data are presented as Tukey box plots. *P < 0.05, **P < 0.01; n = 7 mice. C–G: BrdU-labeled type II cells in C57BL/6 mice. Lungs from BrdU-injected mice were subjected to immunohistological analysis, and cell proliferation rates of CD44^low or CD44^high type II cells were scored as BrdU⁺Sp-C⁺CD44^low cells vs. Sp-C⁺CD44^low cells or BrdU⁺Sp-C⁺CD44^high cells vs. Sp-C⁺CD44^high cells, respectively. C and D show the same section with a BrdU⁺Sp-C⁺CD44^high cell, and E and F show the same section with a BrdU⁺Sp-C⁺CD44^low cell. G: for each mouse, ~600 Sp-C⁺ cells were scored; n = 5 mice. Data are presented as Tukey box plot. ***P < 0.001.