Abstract: Objective To explore the underlying mechanism that Oxidation low density lipoprotein(ox-LDL) induced aging of hematopoietic stem cells (HSCs) in vitro. Methods Mouse HSCs were isolated by magnetic cell sorting and was cultured with ox-LDL. Cell cycles were detected by flow cytometry and identify aging HSC. CFU-Mix cultivation was used to evaluate the potency of differentiation in HSCs. The production of reactive oxygen specie (ROS )in HSCs was evaluated by flow cytometry analysis and laser scanning confocal microscope assess, respectively. The activities of superoxide dismutase (SOD )and glutathione peroxidase (GSH-Px) and the levels of malondialdehyde（MDA）in supernatant that HSC cultured IMDM were detected by chemical colorimetric method. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to detect aging HSCs. Southern blotting and TRAP-PCR were used to evaluated the length of telomere and the activity of telomerase in HSCs, respectively. Results Exogenous ox-LDL induced HSC aging was compared to HSC without ox-LDL treatment group. Biological feature of aged HSC as follows:1）The percentage of SA-β-Gal positive cells was significantly increased; the ratio of G0/G1 stages was strikingly increased , while the ratio S stage was decreased; the number of CFU-Mix was also notably decreased. 2) The length of telomere was remarkedly Shortening in aged HSC, and the activity of telomerase of aged HSC was also reduced. 3) The content of ROS was increased significantly and the vitality of SOD and GSH-Px was decreased in aged HSC, while the content of MDA in supernatant that aged HSC cultured IMDM was increased . Conclusions ox-LDL could induce mice HSC aging by oxidative stress, which maybe partly ascribed to the length shorter and the activity of telomerase slower.

Key words: Aging, Hematopoietic stem cells, Oxidation low density lipoprotein, Oxidative Stress