Figure 4
Abdominal FLASH irradiation alters the proliferation kinetics in crypt cell regeneration compared to CONV irradiation in non-tumor bearing mice. Cross sections of small intestines were analyzed for BrdU incorporation and crypt cell proliferation kinetics by BrdU IHC. (a) Representative images of BrdU stained jejunum cross sections at 10 × magnification at the indicated time points after sublethal 14 Gy TAI. Scale bar shows 100 μm. (b) 40 × magnified crypt images of the jejunum showing BrdU + crypt cells/CBCs at the indicated time points in CONV and FLASH irradiated animals. Scale bar shows 25 μm. Blue dotted lines outline the crypt structure. Black asterisks at the base of the crypt indicate the BrdU + proliferating CBCs in the stem cell zone. The rest of the brown nuclei within the crypt indicate BrdU + cells in the TA zone. (c) Quantification of the average number of BrdU + cells per crypt (includes BrdU + cells in both TA zone and stem cell zone). (d) BrdU + CBCs per crypt at 4, 24, 48, 72 and 96 h in unirradiated controls and after 14 Gy TAI, demonstrating relative early sparing of proliferating CBCs and more robust regeneration after FLASH vs. CONV irradiation. CBC cells were identified based on location at the + 1 to + 3 position wedged between Paneth cells and BrdU + CBCs indicated by black asterisks in the stem cell zone. Fifty crypts per circumference were quantified for BrdU + crypt cells and BrdU + CBCs. Three circumferences per mouse were analyzed (n = 4 mice per group). *p < 0.05, **p < 0.01, ****p < 0.0001; Comparisons by ordinary one-way ANOVA followed by Sidak’s multiple comparisons test. Error bars represent standard deviation of the mean.
