An alternative model of vascularized bone marrow transplant: partial femur transplantation.

The vascularized whole femur transplantation model is one of the commonly used vascularized bone marrow transplant models. It involves technical complexity and morbidities. To optimize this model, we took 2/3 femur as the carrier of bone marrow cells, and developed a vascularized partial femur model. Four experimental groups were carried out, namely, the syngeneic partial femur transplantation, allogeneic partial femur transplantation with or without cyclosporine A, and allogeneic whole femur transplantation with cyclosporine A. The results showed that the partial femur model was technically simpler and shortened the operative and ischemia time compared to the whole femur model. Gross and histologic appearance confirmed the viability of femur, and its bone marrow inside the bone could also maintain normal morphologically at 60-day posttransplant. Besides, donor multilineage chimerism could be continuously detected in immunosuppressed allogeneic partial femur recipients at 1-, 2-, 3-, 4-, and 8-week posttransplant, and it showed no significant differences when compared with whole femur transplantation. Meanwhile, long-term engraftment of donor-origin cells was also confirmed in recipients' bone marrow, lymph nodes, and spleen, but not in thymus. Therefore, the vascularized partial femur can serve as a continuous resource of bone morrow cells and may provide a useful tool for the study of immune tolerance in vascularized composite allotransplantation.