Alterations in cell-type proportions associated with aging or adiposity. (A) Relative proportions of hematopoietic and nonhematopoietic cell types depicted in each sample and grouped by age. (B) Proportion of HSPCs does not differ with increasing age (P > .05); however, an increase in proportion of HSPC is observed upon normalization to cell density/mm² (2.57 ± 1.3 vs 4.66 ± 1.15 [P < .005] for ≤20 years vs 20 to 60 years; 4.66 ± 1.15 vs 3.34 ± 1.19 [P < .05] for 20 to 60 years vs >60 years; and 2.57 ± 1.3 vs 3.34 ± 1.19 [P < .05] for ≤20 years vs >60 years). Pairwise comparisons between age groups for specific cell types shows diminished proportions of myeloblasts (0.0079 ± 0.0053 vs 0.0038 ± 0.0026; P < .01) and proerythroblasts (0.0104 ± 0.0037 vs 0.0037 ± 0.0028; P < .001), between ≤20 years and >60 years BMs. Conversely, proportions of NHEs increased with aging (≤20 years and >60 years, 0.22 ± 0.052 vs 0.317 ± 0.09; P < .01). (C) Representative MxIF examples of ≤20 years (WCM66, top) and >60 years (WCM57, bottom) BM specimens show greater cellular density (top) and higher fat content (bottom), respectively. (D) Positive correlation between fat-to-cell ratio and increasing age (Spearman R = 0.424; P < .05). Fat-to-cell ratio as quantified by AI-based image analysis shows heterogeneity within age groups. Separation of the entire cohort at the median for fat-to-cell ratio reveals no significant difference in proportion of HSPCs (P > .05). Increasing marrow adiposity correlates with diminishing proportions of myeloblasts (trend, Spearman R = −0.349; P = .064) and significant diminution of promyelocytes (Spearman R = −0.591; P < .001) and proerythroblasts (Spearman R = −0.508; P < .005), irrespective of age. DAPI, 4′,6-diamidino-2-phenylindole; ns, not significant.