Long-term follow-up of SIRT1^−/− mice reveals adequate mature blood cell production with normal frequencies of primitive HSCs in the BM. (A) Survival curves for the SIRT1^−/− (full line), SIRT1^+/− (dashed line), and SIRT1^+/+ (dotted line) mice that survived to weaning (left) and up to 7 months of age (right). (B) Quantitative analysis of hematocrit, WBCs, and platelets in the peripheral blood of SIRT1^−/− (gray) and SIRT1^+/+ (white) mice. Three age groups were analyzed: young (1-3 months) middle-aged (3-10 months) and old (10-20 months); n = 10-12 per group. Bars represent means ± SEMs. (C) FACS analysis of the primitive HSC compartment, identified by low expression of lineage markers (Lin), high expression of Sca-1, c-kit, and CD150 surface molecules, and specific Hoechst 33342 staining pattern. One representative sample for SIRT1^−/− and SIRT1^+/+ group is shown. (D) Absolute numbers (as per 4 limbs per mouse) of Lin-Sca-1⁺Kit⁺CD150⁺ (LSK SLAM), LSK SLAM SP, and LSK SLAM SP_low populations within the bone marrow of SIRT1^−/− (gray) and SIRT1^+/+ (white) mice in three age groups: 1- to 3-month old (young), 4- to 6-month old (middle-aged) and older than 12 months (old mice). Bars represent means ± SEM, n = 5-10 per group. No statistically significant differences observed.