Study of Human Umbilical Cord-derived Mesenchymal Stem Cells for Treatment of Refractory Immune Thrombocytopenia

This is a single-arm study to evaluate the safety and efficacy of hUC-MSCs to treat refractory immune thrombocytopenia. 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.