DIFFERENT ROUTES OF DONOR DERIVED HEMATOPOIETIC STEM CELLS TRANSPLANTATION FOR DONOR SPECIFIC CHIMERISM INDUCTION ACROSS MHC BARRIER

Abstract

P940 Aims: Transplantation of donor–derived stem cells can improve organ allograft survival in animal models. This study was designed to investigate the effect of different routes of stem cell transplantation (SCT) on donor specific tolerance induction across MHC barrier under short-term CsA monotherapy and αβTCR/CsA treatment protocols. Methods: Forty-eight SCT were performed between BN (RT1n) donors and Lewis (RT1l) recipients. Intraosseous and intravenous SCT was studied in 6 groups of 8 animals each receiving 35x106 (n=4) and 70x106 (n=4) SCT. Groups I and II served as controls and received SCT but no treatment. Groups III and IV received CsA monotherapy for 7-days, Groups V and VI were under αβTCR/CsA protocol for 7-day. Flow cytometry analysis was used for evaluation of immunodepletion of T-lymphocytes and multilineage donor specific chimerism for MHC class-I (RT1n) for RT1n/CD4, RT1n/CD8 and RT1n/CD45RA antigens in peripheral blood of recipients at post-transplant days 7, 21, 35 and 63. Results: All animals survived without sign of graft versus host disease. At day 63 non-treatment groups receiving 70x106 SCT developed 4.3% of multilineage donor-specific chimerism following intraosseous transplantation and 1.0% following intravenous transplantation. At day 7 under CsA monotherapy and 70x106 SCT, chimerism level for 1.5% RT1n/CD4 was induced in intraosseous and 10.5% in intravenous transplanted groups. At day 63 following intraosseous transplantation chimerism for RT1n/CD4 was stable, but following intravenous transplantation significantly declined to 0.8%. Under αβTCR/CsA protocol T-lymphocyte subpopulation was significantly depleted at day 7 and repopulated to pre-transplant level at day 63. After intraosseous transplantation of 70x106 SCT at day 7 chimerism was 5.7% for RT1n/CD4, and increased up to 6.5% at day 63. In contrast in intravenously transplanted groups at day 7 chimerism was higher and showed 23.7% for RT1n/CD4 antigens, however declined to 0.9% at day 63. Multilineage chimerism was 75% higher in intraosseous (9.9%) when compared with intravenous (3.4%) transplant groups receiving 70x106 SCT at day 63. Following intraosseous SCT under αβTCR/CsA protocol, multilineage chimerism was 50% higher in group receiving 70x106 stem cells (9.9%) compared to 35x106 stem cells (4.9%). Conclusions: Stem cell transplantation under αβTCR/CsA protocol showed better engraftment of donor cells following intraosseous delivery leading to development of higher level (75%) of multilineage donor-specific chimerism when compared with intravenous transplantation. High level of chimerism in intravenously transplanted groups was transient, whereas intraosseous transplantation induced stable chimerism, which was maintained up to 63 days post-transplantation. This strategy of intraosseous stem cell transplantation under αβTCR/CsA protocol could be applied for chimerism and tolerance induction during transplantation of composite and solid organ allografts.