Human umbilical cord (hUC)-derived mesenchymal stem cells (MSCs) have been shown to have marked therapeutic effects in a number of inflammatory diseases and autoimmune diseases in humans based on their potential for immunosuppression and their low immunogenicity. Currently, no more data is available on the safety and effectiveness of hUC-MSCs to treat immune thrombocytopenia patients.~This is a single-arm study to evaluate the safety and efficacy of hUC-MSCs to treat refractory immune thrombocytopenia（ITP）. In addition, it is the objective of this study to observe the changes of immune function in refractory ITP patients after hUC-MSCs infusion, and to explore and reveal the mechanism of hUC-MSCs in treating ITP.~The investigator will assess the changes of the platelet counts after hUC-MSCs infusion from week 1 to week 28, and observe incidence of adverse events during and after hUC-MSCs infusion.The investigator will complete virus detection( including HBV, HCV, HIV, Syphilis, etc) at week 4 and week 16 after hUC-MSCs infusion.~The dose of hUC-MSCs will be successively divided into three increasing dose(group A: hUC-MSCs 0.5×10^6/kg, weekly for 4 weeks, 3 patients; group B: hUC-MSCs 1.0×10^6/kg, weekly for 4 weeks, 3 patients; hUC-MSCs 2.0×10^6/kg, weekly for 4 weeks, 3 patients) with 3 patients in each group according to the dose.~The principle of increasing dose will be carried out successively from low dose to high dose group. According to the results of the safety and efficacy data from these 9 patients, the investigator will determine one of the doses and expand the sample size to 6 cases.~The investigator will observe the concentration of hUC-MSCs in peripheral blood from female patients after the first hUC-MSCs infusion at 10 time points, including 30 minutes before hUC-MSCs infusion, 30 minutes, 60 minutes, 2 hours, 4 hours, 8 hours, 16 hours, 24 hours,48 hours and 96 hours after the first hUC-MSCs infusion.~The investigator will detect antibody production of hUC-MSCs in peripheral blood from the first 9 patients at 2 time points, including 30 minutes before the first hUC-MSCs infusion and 48 hours after the last hUC-MSCs infusion.~The investigator will observe the changes of immune function in refractory ITP patients after hUC-MSCs infusion at 7 time points, including one day before hUC-MSCs infusion, 2 weeks, 4 weeks, 8 weeks, 12 weeks, 16weeks and 28 weeks after hUC-MSCs infusion.
Primary Objective: To evaluate the safety and efficacy of human umbilical cord-derived mesenchymal stem cells（hUC-MSCs） to treat refractory immune thrombocytopenia（ITP）.~Secondary Objective: To observe the changes of immune function in refractory ITP patients with human umbilical cord-derived mesenchymal stem cells（hUC-MSCs） after infusion, and to explore and reveal the mechanism of hUC-MSCs in treating ITP.