scRNA-seq of hematopoietic and nonhematopoietic fractions of the BM from young and MA mice. (A-B) Cell surface marker definitions (top) and cell frequency (bottom) in the BM of young (2 months; n = 5) and MA (14 months, n = 9) female C57BL/6J mice. (C) Representative flow cytometry gating for isolation of cell populations from young and MA mice (top) and ratio at which sorted populations were mixed for scRNA-seq (bottom). (D) UMAP projection of pooled data from a subset of young (n = 4; 22 328 cells) and MA (n = 4; 23 093 cells) mice with annotated cell populations denoted by different colors. (E) Frequency and variance of hematopoietic stem and progenitor cell populations in young and MA mice identified by cluster annotation. (F) Frequency and variance of mature hematopoietic cell populations in young and MA mice identified by cluster annotation. (G) Frequency and variance of endothelial cell populations in young and MA mice identified by cluster annotation. (H) Frequency and variance of mesenchymal cell populations in young and MA mice identified by cluster annotation. (E-H) Dots represent individual mice. P values were calculated by unpaired t test and F test to compare variances. ∗P < .01; ∗∗P < .001; ∗∗∗P < .0001.