Objective:To establish murine hematopoietic stem cell aging model in vivo and identify it with various biologic research and to provide a research platform for delaying senescence of hematopoietic stem cells(HSCs).Methods:Sca-1+ HSCs isolated and purified from male donor mice(C57BL/6)by magnetic activated cell sorting(MACS)were analyzed by flow cytometry and immunofluorescence for cell cycle and Sca-1 expression.Serial transplantations were carried out using C57BL/6 female recipients which were conditioned(4.5×2 Gy total body irradiation

with 3 h interval)

and then to assay the Sry gene of Y Chromosome from recipient mice to identify whether HSCs were from male donor mice.HSCs aging biological characters were analyzed by culturing of CFU-Mix

cell cycle assay and senescence associated β-Galactosidase(SA-β-Gal)staining.Recipient mouse HSCs aging and hematopoiesis reconstruction were observed and evaluated through the count of CFU-S after transplantation

the determination of spleen index and thymus index

and the examination of peripheral blood indexes(WBC

RBC

PLT and HCT).Results:The purity of Sca-1+ HSCs isolated from experimental mice through MACS could be achieved 87.2%.Sry gene(342 bp)could be detected by the method of PCR in Y chromosome analysis

which confirmed that the female recipient mouse Sca-1+ HSCs totally originated from male donor mice.Spleen index

thymus index

ability of CFU-S forming and peripheral blood indexes(WBC

RBC

PLT and HCT)were dramatically declined.The number of CFU-Mix and the cells which formed CFU-Mix were significantly reduced.HSCs isolated from recipient mice and originated from donor mice were blocked in phase G1

and the ratio of G0+G1 was significantly higher

nevertheless

cells of phase S were reduced.The percentage of positive cells after the staining of SA-β-Gal was obviously higher with the increased number of transplantation.Conclusion:Serial tail vein transplantations of Sca-1+ HSCs can preliminarily establish the murine hematopoietic stem cell replicative aging model in vivo.