OBJECTIVETo explore the effect of mesenchymal stem cells (MSCs) on refractory acute graft-versus-host disease (GVHD) failed to second-line immunosuppressive therapy.

METHODSTwenty-two patients with refractory aGVHD received the treatment of first- and/or second-line immunosuppressive agents in combination with MSCs. The MSCs from bone marrow (BM) of HLA-unrelated third-party donors, were used at the median time of 19 (11 - 49) days after aGVHD onset, at a dose of 1×10(6)/kg once with an interval of 14 days. If the symptoms of aGVHD did not improve after continuous infusion four times, MSCs would be discontinued. Meanwhile the proportion of CD3(+)CD4(+), CD3(+)CD8(+) and CD4(+)CD25(+) was detected by flow cytometry (FCM) before and 4 weeks after the MSCs infusion.

RESULTSThe median dose of MSC was 4.8 (2.5 - 6.3)×10(6) cell×kg(-1) with a median infusion of 2.5 (1 - 7) times per case. Twelve patients achieved complete response (CR), four partial response (PR) after treatment. The total effective rate was 72.7% (16/22). With a median follow-up of 246.5 (36 - 1116) days post-transplantation, 11 patients survived and 11 died. The causes of death included GVHD(n = 6), infections (n = 3), leukemia relapse (n = 1) and post-transplant lymphoproliferative diseases (n = 1), respectively. The proportion of CD3(+)CD4(+)/CD3(+)CD8(+) was significantly higher at 4th week after MSCs infusion compared to before infusion (1.58 ± 0.54 vs 0.49 ± 0.19, \%t\% = 0.628, P = 0.04). The number of CD4(+)CD25(+) Treg cells had not changed much compared to before infusion (P = 0.606).

CONCLUSIONMSCs derived from the BM of a third-party donor are effective to treat aGVHD failed to second-line immunosuppressive therapy after allo-HSCT. MSCs might play a role in aGVHD by regulating the rate of CD3(+)CD4(+)/CD3(+)CD8(+).