Abstract： The multi-potent differentiation capability of mesenchymal stem cells (MSCs) implies potential to achieve patient-specific regenerative therapy for myocardial infarction. However, it is evident that transplanted stem cells do not survive well in the harsh ischemic microenvironment. Erythropoietin (EPO) has been shown to be a potent inhibitor of neuronal and myocardial apoptosis. Here, we investigate the cell viability and the change of erythropoietin signal pathway of MSCs challenged by hypoxia treatment.Methods MSCs were derived from the bone marrow of 2-week-old Wistar rats and expanded. Hypoxia treatment of cells was performed using a ProOx-C-chamber with the oxygen concentration set to 0.5% for the times required.Results The rate of trypan blue staining was 3.5% ± 0.4% in control group, and 3.9% ± 0.2%, 5.0% ±0.5%, 7.1% ± 0.5% in the groups treated with hypoxia for 24, 48, 72, 96 hours. Western blot analysis suggested the expression of EPO in MSCs was significantly upregulated after 48-hour treatment with hypoxia, which was further confirmed by immunofluorescence staining. There was higher and earlier expression of EPOR. And the expression level of total ERK remained constant during the hypoxic treatment. However, the expression of HIF-1α phosphorylated ERK was significantly upregulated after 24-hour treatment with hypoxia and peaked at 72 hours.Conclusions MSCs is not sensitive to hypoxia insult alone. The components in EPO signal pathway (e. g.EPO, EPOR and P-ERK) is upregulated in MSCs after hypoxic treatment, which suggests that EPO signal pathway plays an important role in the hypoxia-tolerance and paracrine protecting capability of MSCs.