Objective:To investigate whether Angiotensin Ⅱprotects mesenchymal stem cells (MSCs) from hypoxic injury. Methods:The MSCs were isolated and cultured,and their purities were identified with the spindle-fibroblastic morphology characterization by microphotograph,and the phenotypes were tested by flow cytometry with anti-CD29 and anti-CD11b/c antibodies. Before preconditioned by AngⅡ,the MSCs were treated with or without angiotensin 1(AT1) receptor antagonist losartan,angiotensin 2(AT2) receptor antagonist PD123319. Then the cells were suffered from hypoxia and serum deprivation for 24 hours. The cell viability and apoptosis were determined by trypan blue staining,MTT,CCK-8 assay and Annexin V-FITC staining. Results:① MSCs expressed CD29,but not the CD11b/c. The purity of MSCs employed in this study was up to 97%;② AngⅡpreconditioning (PC) markedly protected MSCs from hypoxic injury. However,these effects were abolished by prior treatment with losartan rather than PD123319. Conclusion:These results suggest that AngⅡpreconditioning protects MSCs from hypoxic injury through AT1 receptor.