1330

Stem cell transplantation is of critical importance in the treatment of leukemia. However, graft vs. host disease can limit the efficacy of this treatment modality. In this study, in order to visualize graft vs. host disease in real time, we used donor cells labeled with GFP to image the engraftment in various organs of chemotherapy-pretreated recipients. GFP transgenic C57/BL6 mice (GFP-Tgm) were used as donors and C57/BL6 x DBA F1 mice (BDF1) were used as recipients. Recipient mice were pretreated with fludarabine (Flu), 150 mg/kg/day x 6 days i.p., and cyclophosphamide (CPA), 150 mg/kg/day x 2 days i.p. On day 0, 107 GFP splenocytes (Group 1) and GFP bone marrow cells (Group 2) were injected in the tail vein. Whole body and intravital imaging were used to visualize the migration of GFP-Tgm cells into various organs including the brain, femur, intestine, liver, lung, ovary, pelvic bone, ribs, skin, skull, spine, spleen and uterus on days-7 and -14. The macro images were obtained with the Olympus OV100 Small Animal Imaging System. GFP-Tgm cell migration, particularly CD34+ cells in the various organs, was analyzed by flow cytometry (FACS) using APC-labeled anti-CD34 monoclonal antibodies. On day-7, the migration of donor GFP-Tgm cells in peripheral lymph nodes, intestine, lung, ovary, skin and uterus were detected in both groups. Migration of GFP-Tgm cells in the femur, pelvic bone, ribs and skull were clearly detected in Group 2, but not in Group 1. On day-14 GFP donor cells were imaged in the lung, ovary, skin and uterus both groups. However, GFP-Tgm cells were no longer imaged in the intestine in Group 2 except in Payer patches. In both groups the GFP-Tgm cells were strongly detected in the femur, pelvic bone, skull and spine on day-14. We also analyzed the migration of CD34+ GFP-Tgm cells by FACS analysis. On day-14, the percentage of GFP-Tgm cells in the bone marrow and spleen was, respectively, 14% and 53% in Group 1, and 10% and 13% in Group 2. The percentage of CD34+ GFP-Tgm cells among total CD34+ cells in the bone marrow was 10% in Group 1 and 14% in Group 2, and in the spleen was 24% and 19%, respectively. Those results suggested that in this model, donor bone marrow and spleen cells, but not purified CD34+ cells, have different engraftment kinetics in various organs including the intestine, which is a target organ for graft-versus host disease. These results demonstrate the power of GFP imaging to evaluate donor-cell engraftment kinetics and that results obtained by other methods may have to be re-evaluated.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA