Figure 4. Old mice exhibit increased proportion of Sox9-EGFPLow IESC and Sox9-EGFPHigh cells in S-phase as assessed by flow cytometry and histology. (A and B) Relative abundance of Sox9-EGFP expressing populations that have incorporated EdU was measured by flow cytometry. n=6 animals per group, *p<0.05 Young vs. Old, unpaired t test. (C) Representative images of crypt sections from young and old Sox9-EGFP mice stained with EGFP, S-phase marker EdU and nuclear marker DAPI. Closed arrows indicate Sox9-EGFPLow IESC in S-phase. (D) Number of total crypt cells incorporating EdU per Sox9-EGFP crypt section. n=6 animals per group. (E) Number of Sox9-EGFPLow IESC incorporating EdU per crypt section. n=6 animals per group, *p<0.05 Young vs. Old, unpaired t test.