OBJECTIVETo explore immunoregulatory mechanism of mesenchymal stem cells (MSCs) in H-2 haploidentical bone marrow cells transplantation mice.

METHODSBALB/c female mice irradiated with 8Gy 60Co gamma-rays were divided into two groups: MSCs group, infused cm-DiI labeled MSCs from female CB6F1 mice and monocytes from the bone marrow and spleen of male CB6F1; Control group, only infused monocytes from the bone marrow and spleen of male CB6F1. T-lymphocyte subpopulation of peripheral blood cells, T and B cells proliferation stimulated by ConA and LPS, mixed lymphocyte reaction between donor and recipient and third part, the sry-gene chimerism of bone marrow, spleen and thymus of the recipient, the distribution of MSCs in the recipient, the incidence rate of GVHD and survival were observed.

RESULTSThe CD3 at +90 d the percent of CD3+ CD4+ cells, and CD4/CD8 at +30 d in the MSCs group were higher than that in control post-transplantation, respectively (P < 0.05). The proliferation activity of B cells recovered more rapidly and that of T cells recovered comparably in MSCs group as compared with that in control group. The result of MLR between donor and recipient was lower in MSCs group than that in the control; and that between recipient and the third part had no difference. The sry-gene chimerism of bone marrow and spleen of the recipient was higher in MSCs group than in control at +30 d. The MSCs mainly distributed in intestine, thymus, bone marrow, liver, heart of the recipient after transplantation. The incidence of acute GVHD was higher and the survival rate was lower in MSCs group than that in control group (P < 0.05). Chronic GVHD occurred in the control group at +90 d, while in the MSCs group at +120 d.

CONCLUSIONSMSCs might improve stem cell engraftment, promote lymphocyte and humoral immunity recovery, decrease incidence of GVHD and increase survival by inducing specific immunologic tolerance and repairing organs injuries.