Abstract: Objective To investigate the effects of hypoxia on the cell proliferation, apoptosis and secretion of rabbit urine derived stem cells (rUSCs)；Methods rUSCs were isolated and cultured with oxygen concentration at 20 % and 3 %, respectively. To observe the morphological changes of rUSCs in different culture conditions continuously; The growth curves under different culture conditions were drawn respectively；Antibody detection of factor secretion was performed；The cell cycle and the apoptosis were analyzed by flow cytometry. Results Single, small, compact “rice-grain” like cells were observed on day 6, after cultured in different oxygen concentration，the cells in normoxia group appeared like "spindle", the cells in hypoxia group changed into " pebble" like; The growth curves of two groups showed a "S" shape, but the cells in hypoxia group had a faster growth speed compared with normoxia group (P <0.01 resp.); Compared with normoxia group, the paracrine effect in hypoxia group had an increased expression level , and an increased variety ; Less cells were arrested at G0/G1 phase under hypoxia as compared with that in normoxia group(71.82%±8.86% and 91.73%±1.35%, resp.) (P<0.05), while the cell numbers at S phase increased in hypoxia group are comparied with that of normoxia group(18.77%±3.87% and 3.48%±0.73%, resp.) (P<0.01); The apoptosis rate of normoxia group(3.24%±0.38% ) was significantly higher than that of hypoxia group by flow cytometry (0.43%±0.05%) (P<0.001); and the apoptosis rate of normoxia group(4.27%± 0.48% ) was significantly higher than that of hypoxia group by Hoechst（1.37%± 0.33%）（P<0.01）. Conclusion It is demonstrated that culture at 3% O2 could enhance cell proliferation and reduce apoptosis of rUSCs.

Key words: rabbit urine derived stem cells, hypoxia, cell proliferation, cell apoptosis