Figure 2. Radiation induces proliferation and villus differentiation in a subset of Paneth cells.

(A) Experimental scheme showing lineage labeling of adult Lyz1^CreER; R26R-tdT mice by tamoxifen injection, followed by radiation and tissue analyses (3 mice for each time point).

(B-E) Non-irradiated (N.R.) tdT⁺ Paneth cells do not express PCNA, however after irradiation tdT⁺ cells became positive for PCNA on day 3 and 5 (yellow arrowheads). Scale bar, 10 μm.

(F) Radiated Lyz1^CreER; R26R-tdT mice showed red epithelial stripes (a representative image of day 7 was shown).

(G-J) Some irradiated tdT⁺ Paneth cells co-expressed Olfm4 (yellow arrowheads in G) in the crypts, while some villus tdT⁺ cells co-expressed SI (H), or Muc2 (I). or ChgA (J). Scale bar, 10 μm.

(K) Some irradiated tdT⁺ cells retained Paneth cell marker (Mmp7, left panel), while villus tdT⁺ cells lost Paneth cell marker (right panel). Scale bar, 10 μm.

(L) CD24⁺EpCAM⁺CD45⁻ and CD24⁻EpCAM⁺CD45⁻ cells were FACS-sorted from non-irradiated (N.R.) and irradiated mice.

(M) qPCR showed that CD24⁻EpCAM⁺CD45⁻ cells sorted from irradiated mice (green box in L) expressed the cell lineage marker tdT (green bar). CD24⁻EpCAM⁺CD45⁻ cells from N.R. mice (blue box in L) did not express tdT (blue bar).

(N) ImageStream analysis of FACS-sorted single tdT⁺ cells from irradiated mice showed 2 distinct cell populations: CD24⁺ (top) and CD24⁻ (bottom). Scale bar, 10 μm.