Figure 3. Accelerated spermatogenesis after irradiation-induced injury and abnormal spermatogenesis after deletion of Bmi1^High-positive cells.

(a) Experimental protocol of irradiation and tamoxifen administration to Bmi1^creER/+/Rosa26^Rbw/+ mice. The mice were irradiated at 1 Gy or 5 Gy and then injected with tamoxifen, and labeled cells were analyzed at indicated time points. A red arrow; tamoxifen administration. A green arrow; irradiation. Black arrows; time points of analyses of the testes. (b) Accelerated proliferation of Bmi1^High-positive stem cell-derived cells after irradiation. (upper and middle panels) Bmi1^creER/+/Rosa26^Rbw/+ mice were irradiated at 1 Gy or 5 Gy and were injected with tamoxifen, and labeled cells were analyzed up to the 14th day. (lower panel) Control mice without irradiation. Red, orange or blue arrowheads: red-, orange- or blue-color labeled cells derived from Bmi1^High-positive stem cells. (c) Typical findings observed by PAS-hematoxylin staining in each seminiferous epithelial stage. Roman numbers indicate seminiferous epithelial stages. (d) PAS-hematoxylin staining. Seminiferous epithelium with stage-mismatched area in the testes of Bmi1^creER/+/Rosa26^{loxp-stop-loxp-DTA/+} mice 4 weeks after tamoxifen administration. Magnified images of red squares in the left panel are shown in the right panels. In the area of stage VIII, PAS-positive acrosomes (yellow arrowheads) are observed. In the area of stage XII - I, no acrosome (black arrowheads) was observed but instead dividing spermatocytes were observed. Roman numbers indicate seminiferous epithelial stages. (e) Frequency of the seminiferous intratubular areas with stage-mismatches of tamoxifen-injected or untreated Bmi1^creER/+/Rosa26^{loxp-stop-loxp-DTA/+} (Bmi1^creER/+;Rosa26^dta/+) mice. Scale bars = 100 μm in (b and d) and 20 μm in (c).