Cell proliferation and survival in TIMP-1^−/− SP^KLS HSCs. (A) Representative flow cytometric plots of cell-cycle analysis performed with PyroninY/Hoechst 33324 staining on WT or TIMP-1^−/− SP^KLS LT-HSCs. (B) Cell-cycle analysis of SP^KLS HSCs and percentage distribution in the phases G₀, G₁, and S-G₂M. The percentages of SP^KLS in the G₀ phase of the cell cycle were considerably decreased in TIMP-1^−/− mice than in compared with the control (P < .05), whereas a 2.6-fold increase in the percentage of HSCs in the G₁ phase was accordingly recorded (P < .05). (C) Percentages of Ki-67⁺ cells in WT and TIMP-1^−/− SP^KLS cells. (D) Cell survival analysis performed by annexin V staining on HSCs immediately after isolation. We observed that the percentage of Annexin V⁺ SP^KLS cells was essentially the same in the 2 groups. (E) Expression levels of cell-cycle inhibitors in SP^KLS cells was assessed by real-time PCR. Values are the average of duplicate experimental replicates. For each group, SP^KLS cells from 3 different animals were pooled together for RNA extraction. *P < .05 and **P < .01.