Figure 5.

Both old HSCs and the old niche impaired reconstitution of the stem and progenitor cell compartment

(A) Schematic of HSC transplantation from young or old mice into young mice.

(A′) The total number of BM cells was similar in young recipient mice >16 weeks after transplantation of either young or old HSCs.

(A″) Old HSCs contributed to significantly lower donor-to-host chimerism of BM stem and progenitor cells in young recipient mice compared with young HSCs. Percent donor chimerism of HSPCs and erythromyeloid progenitors in the recipient BM of young or old HSCs >16 weeks posttransplant.

(A‴) Old HSCs generated fewer total stem and progenitor cells than young HSCs in young recipient mice. Quantification of total donor-derived classical HSPCs and erythromyeloid progenitors in the BM of recipients >16 weeks posttransplant.

(B) Schematic of HSC transplantation from young mice into separate cohorts of young or old mice.

(B′) The total number of BM cells was similar in young and old recipient mice >18 weeks after transplantation of young HSCs.

(B″) Old recipients displayed lower donor-to-host HSPC chimerism than young recipient mice transplanted with young HSCs. BM analysis of young or old mice transplanted with young HSCs. HSPCs were analyzed >18 weeks posttransplant and presented as donor chimerism.

(B‴) Transplanted young HSCs produced fewer total HSPCs in the BM of old compared with young recipient mice. Quantification of total donor-derived HSPC numbers in the BM of recipients >18 weeks posttransplant.

YY, Young HSCs transplanted into young recipients; OY, Old HSCs transplanted into young recipients; YO, Young HSCs transplanted into old recipients. Data are representative means ± SEM. PB analysis of the same recipient mice are presented in Figures 2A′ and 2A‴ and Figure 3B′ and 3B‴. p values were determined using unpaired two-tailed t test. ^∗p ≤ 0.05, ^∗∗p < 0.005, ^∗∗∗p < 0.0005, ^∗∗∗∗p < 0.0001.