OBJECTIVETo evaluate the safety and efficacy of umbilical cord-derived mesenchymal stem cells (MSCs) infusion in patients with steroid-resistant severe acute graft-versus-host disease (aGVHD).

METHODSA total of 19 patients with steroid-resistant severe aGVHD received MSCs infusion treatment. The treatment response, transplantation-related mortality, events associated with infusion and relapse rate were analyzed.

RESULTSTwo patients with grade II, 5 patients with grade III and 12 patients with grade IV aGVHD received a total of 58 infusions of MSCs. The mean total dose of MSCs was 2.13 (range 0.60 - 7.20)×10(6) cells per kg bodyweight. Seven patients received one infusion, 2 patients received two infusions, and 10 patients received three or more infusions. Eleven patients had a complete response and 4 had a partial response and 4 had no response. No patients had side-effects during or immediately after infusions, and no MSCs related tumorigenesis was detected to date. Eleven patients survived and 8 died, 4 for aGVHD, 1 for infection and 2 for aGVHD with concomitant infection and 1 for underlying leukemia relapse. The cell viability of freshly prepared MSCs is 93% (92% - 95%) by trypan blue staining. The cell viability of programmatically frozen and thawed MSCs is 72% (70% - 74%).

CONCLUSIONInfusion of umbilical cord-derived MSCs expanded in vitro is an effective therapy for patients with steroid-resistant severe aGVHD without negative impact on relapse. Freshly prepared MSCs are superior to frozen and thawed cells in terms of cell viability.