EFFECTS OF PERITRANSPLANT ADMINISTRATION OF HEMATOPOIETIC GROWTH FACTORS ON THE DEVELOPMENT OF CHRONIC REJECTION

Abstract

13 Purpose: Chronic allograft rejection remains as the major obstacle to successful organ transplantation. We have previously shown that persistent existence of donor hematolymphoid cells after transplantation participated in the resistance to chronic rejection, and hypothesize that augmentation of donor chimerism after transplantation is able to prevent chronic rejection. In this study, we examined effects of perioperative administration of hematopoietic growth factors on the development of chronic rejection using simultaneous heart and bone marrow transplantation model. Results were analyzed with the correlation to levels of chimerism. Methods: Female Brown Norway (BN, RT1n) rats received heterotopic heart allografts (Htx) and simultaneous bone marrow (BM, 2.5 × 108) infusion from male Lewis (LEW, RT11) donors. All recipients received tacrolimus (1.5 mg/kg/day) on days 0 to 13, 20, and 27. Hematopoietic growth factors of variable lineage specificity (table) were injected to recipients on days 0 to 6. All recipients were sacrificed on day 100 and tissues were analyzed for levels of chimerism by PCR and Southern blot hybridization using rat sex determining region-Y (Sry) specific oligonucleotide primers and 32P-labeled probe. Severity of chronic rejection in heart allografts was analyzed by histopathology and scored. Results: At day 100, male DNAs were more easily detected in recipient non-lymphoid organs (skin, native heart) than lymphoid organ (spleen, cervical lymph nodes) or blood. Donor BM infusion significantly augmented chimerism, and Flt-3 ligand and IL-6 were able to further significantly enhance chimerism levels. Histopathological analysis demonstrated the significant amelioration of overall inflammation and obliterative arteriopathy (OA) in recipients treated with BM infusion and GCSF or IL-6 treatment. In addition, a significant regression was found between the levels of overall inflammation and chimerism. Table P values vs Htx: a<0.05, b<0.01, c<0.001, d<0.0001, vs Htx+BM: c<0.05TableConclusions: This study demonstrates that simultaneous infusion of donor BM and the appropriate use of hematopoietic growth factors are effective in enhancing chimerism and improving histopathological abnormalities associated with chronic allograft rejection.