Age-dependent remodeling of human HSPCs compartment, stem cell frequency and functional output across distinct age cohorts. (A–H) Frequencies of distinct HSPCs subpopulations within CD34⁺LIN⁻ compartment in healthy donors from different ages in the Italian cohort (P = Pediatric <18 years, n = 9; Y = young 18–35 years, n = 12; M = middle-aged 40–60 years, n = 20; O = old >65 years, n = 31) and in the North American (Canada) cohort (Y: n = 3; M: n = 4; O: n = 6). Statistical test: Mann–Whitney; HSCs Italy: P vs. O, P = 0.0004; Y vs. O, P = 0.0007. MPP Italy: P vs. O, P = 0.0008; Y vs. M, P = 0.0392; Y vs. O, P < 0.0001. MLP Canada: Y vs. O, P = 0.0476; M vs. O, P = 0.019. ETP Italy: P vs. M, P = 0.0186; P vs. O, P = 0.0303. PreB/NK Italy: P vs. Y, P = 0.0073; P vs. M, P = 0.0002; P vs. O, P < 0.0001; Y vs. O, P = 0.0009. CMP Italy: P vs. M, P = 0.0016; P vs. O, P = 0.0027. GMP Italy: P vs. O, P = 0.0146. MEP Italy: P vs. M, P = 0.0211; Y vs. M, P = 0.0157; MEP Canada: Y vs. O, P = 0.024. (I) Frequencies of CD49f⁺-primitive HSCs (defined as CD34⁺CD19⁻CD38⁻CD45RA-CD90⁺CD49f⁺ cells) within CD34⁺LIN⁻ compartment in healthy donors from different ages in the Italian (Y: n = 6; M: n = 7; O: n = 16) and in the North American (Canada) cohort (Y: n = 3; M: n = 4; O: n = 6). (J and K) Tables showing the confidence intervals for 1/stem cell frequency and P values from pairwise test for differences in the stem cell frequencies for the indicated sample groups as calculated by ELDA. Referring to Fig. 2. (L and M) Box plots showing human CD19⁺ and CD33⁺ cell frequencies in the murine BM of mice transplanted with 60,000 cells for CB and BM samples at 4–12 and 20 wk. Statistical test: Mann–Whitney; B cells, 4 wk: CB vs. Y, P = 0.0287; CB vs. M, P = 0.0001; CB vs. O, P = 0.0001. 12 wk: CB vs. M, P = 0.0002. 20 wk: M vs. O, P = 0.0338. Myeloid cells, 4 wk: CB vs. Y, P = 0.007; CB vs. M, P = 0.0065; CB vs. O, P < 0.0001; 12 wk: CB vs. Y, P = 0.007; CB vs. M, P = 0.0065. (N) Box plot showing different human subpopulations frequencies in the murine BM in secondary recipients at 12 wk. * < 0.05; ** < 0.01; *** < 0.001; **** < 0.0001.