Donor-derived marrow mesenchymal stromal cell co-transplantation following a haploidentical hematopoietic stem cell transplantation trail to treat severe aplastic anemia in children.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is associated with an increased risk of graft failure and severe graft-versus-host disease (GVHD). Recent studies have shown that mesenchymal stromal cells (MSCs) display potent immunosuppressive effects and can support normal hematopoiesis. In a multi-center trial, we co-transplanted culture-expanded donor-derived bone marrow MSCs (BM-MSCs) into 35 children with severe aplastic anemia (SAA) undergoing haplo-HSCT. All 35 patients (100%) achieved hematopoietic reconstitution and showed sustained full donor chimerism. The median time for myeloid engraftment was 14 days (range 10-22 days), while that for platelet engraftment was 18 days (range 9-36 days). The incidence of grade II-IV acute GVHD and chronic GVHD was 25.71 and 22.86%, respectively. The overall survival rate was 85.71% with a median of 22 months (range 3.5-37 months). The combined transplantation of haploidentical HSCs and BM-MSCs into children with SAA without an HLA-identical sibling donor is relatively safe and may represent an effective new therapy to improve survival rates and reduce the risk of graft failure.