OBJECTIVETo evaluate the efficacy and safety of bone marrow-derived mesenchymal stem cells (MSC) from a third party donor for secondary poor graft function (PGF) following allogeneic hematopoietic stem cell transplantation(allo-HSCT).

METHODSFive patients with secondary PGF were treated with MSC at a dose of 1 x 10(6)/kg body weight at a median of 47 days (35 to 61) after secondary PGF. MSC were derived from bone marrow (BM) of HLA-disparate third party donors, cultured in vitro and infused without HSC. If absolute neutrophil cell (ANC) and platelet counts (PLT) did not reach the standardization of > 1.5 x 10(9)/L and > 50.0 x 10(9)/L, respectively, within 28-30 days after the first MSC treatment, a second MSC treatment was required.

RESULTSMSC were infused once in one patient and twice in four patients with an interval of 28 to 30 days. All patients obtained ANC and PLT recovery at a median of 34 (25 to 49) days and 47 (26 to 54) days, respectively, without toxic side effects within follow-up periods of median 761 (204-1491) days. Three patients developed Epstein-Barr virus (EBV) reactivation at 42, 48, 108 days after MSC infusion, respectively and two of the three coverted to posttransplant lymphoproliferative disorders (PTLD).

CONCLUSIONMSC from a third party donor are effective to patients with secondary PGF following allo-HSCT, whether it might increase the risk of EBV reactivation and EBV-associated PTLD need further observation.