S1P regulates progenitor cell mobilization and SDF-1 secretion by Nestin⁺ stromal stem and progenitor cells via ROS signaling. (A) The percentages of ROS^high/SKL cells in the BM (bars) and ROS^high/MNC in the PB (dots) of WT and Sphk1 KO mice are shown. (B-C) Mice were injected with PBS or administered with glucose in the drinking water (control), injected with FTY720 (single intraperitoneal injection 24 hours before sacrifice) or administered with DOP (together with glucose for 3 days in the drinking water). Fold change of mean fluorescence intensity of ROS/SKL (B) or the percentage of CD34⁻/SKL (C) cells in the BM are shown. (D) Mean fluorescence intensity of ROS^high in SKL cells of WT and Sphk1 KO mice that were injected with PBS (control) or G-CSF (5 consecutive subcutaneous injections and evaluation 3-5 hours after the last injection) is shown. (E) Immunofluorescence staining of total BM cells from Nestin-GFP mice for SDF-1 expression on stimulation with 1mM BSO (ROS inducer)/vehicle for 2 hours. (F) Immunofluorescence staining of total BM cells from Nestin-GFP mice for SDF-1 expression on stimulation with 1μM S1P alone or together with 2mM NAC for 1 hour. Indicated values are presented as mean ± SE in 3 independent experiments, a total of 4-6 mice in each group (*P < .05, **P < .01).