Hematopoietic progenitors from aged mice exhibit an impaired metabolic response to LPS treatment. (A) Schematic of the experiment. Young (8-12 weeks) and aged (18-24 months) C57Bl/6 mice were treated with 0.5 mg/kg LPS or vehicle control. After 16 hours, they were killed and their BM isolated. (B) Flow cytometry gating strategy and for LSK, LS-K, MPP, and HSC (Lin^–, Sca1⁺, cKit⁺, CD150⁺, CD48^–) populations in aged mice. (C) LSK, LS-K, and MPP cell counts per 100 000 BM cells in young and aged mice after LPS treatment compared with control mice. (D) Example of TMRM^hi and low cell populations in young (blue) and aged (red) mice and frequencies of TMRM^hi LSKs. (E) Frequencies of TMRM^hi LSKs, LS-Ks, and MPPs after LPS treatment in young and aged mice. (F) Changes in OCR compared with extracellular acidification rate (ECAR) in LKs isolated from aged and young mice after LPS treatment. (G) Changes in basal and maximal respiration after LPS treatment in LKs from young and aged mice. (H) Results from the Biolog analysis showing the metabolic utilization of glycolytic and TCA cycle substrates by LKs isolated from young and aged mice treated with LPS compared with control mice. Not detected (ND) levels are labeled, and 1 represents no change. ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, ∗∗∗∗P < .0001 using the Mann-Whitney U test or two-way analysis of variance. Con, vehicle control; FSC, forward scatter; SCC, side scatter; ns, not significant.