CM-DiI Labeled Mesenchymal stem cells homed to thymus inducing immune recovery of mice after haploidentical bone marrow transplantation

The results of haploidentical hematopoietic stem cell transplantation (HSCT) have been disappointing due to the high incidence of severe graft-versus-host disease (GVHD) and infectious complications. It is well known that mesenchymal stem cells (MSCs) can prevent severe acute GVHD in HSCT. However, there is a controversy concerning whether MSC-mediated suppression of T cell functions is accompanied by inducing T cells maturation effects after HSCT. The CB6F1(H-2bd) female mice irradiated with 8Gy 60Co γ-rays were divided into two groups: mice in the MSCs group were infused with MSCs labeled with cm-DiI and mononuclear cells from the bone marrow and spleen of BALB/c(H-2d) mice; the control group was infused with only the mononuclear cells of BALB/c(H-2d) mice. After transplantation, chimerisms of donor MSCs were observed in the recipients. The recovery of the T-lymphocyte subpopulation, the proliferative activity of T-cells after stimulation with ConA, the mixed lymphocytes' reaction between donor and recipient and three parts, and the number of apoptosis thymus cells were compared in two groups. The results showed that MSCs preferentially homed to the thymus and grew there, a more rapid recovery of T-cells in the peripheral blood, and decreased the apoptosis of the thymocytes. Thus MSCs may affect the thymus in order to improve T-cells maturation and immune system recovery. ► MSCs homed to the thymus of mice after bone marrow transplantation. ► MSCs reduced thymus cells apoptosis. ► MSCs induced the CD4 and CD3 lymphocytes of recipient recovery. ► MSCs induce immune reconstitution by homing to the thymus after HSCT.