INTRODUCTION: Composite tissue allografts such as hand transplants contain multiple tissues of different antigenicities. An extraperitoneal isolated vascularized bone marrow transplant (iVBMT) model was developed in the rat in order to study the contribution of the bone marrow component. We hypothesized that the iVBMT would be functional and cause graft-versus-host-disease (GVHD) in a fraction of the recipients. METHODS: Group A=male Lewis donor transplanted across a semiallogeneic barrier to a female Lewis-Brown-Norway (LBN) rat, n=25. Group B=control, male LBN to female LBN, n=10. No immunosuppression was used. The iVBMT model consisted of a left donor femur that was harvested with its nutrient vessels. The graft was anastomosed to the right femoral vessels of the recipient, and placed subcutaneously in the abdominal wall. The animals were sacrificed at various time points between 1 to 14 weeks. RESULTS: Both groups appeared healthy and gained weight. Graft vessels were patent at necropsy, and histology of the grafts demonstrated a viable marrow compartment. No animals exhibited GVHD at sacrifice. CONCLUSIONS: The immune cells derived from the bone marrow component did not cause GVHD in the iVBMT model, and may potentially induce immune tolerance. Further characterization of this issue is underway.
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