Grafting of the recipient with bone marrow cell suspension provides only few stromal cells and no autologous environment for cooperation between hemopoetic and stromal cells. Vascularized bone marrow grafts provide the recipient with bone marrow hemopoetic and stromal cells in their natural spatial relationship. It is expected that such a graft will resume its function soon after transplantation and almost immediately repopulate bone marrow cavities of the irradiated recipient as well as supply the sites of cytopoiesis with the necessary growth factors. The aim of the study was to investigate the process of repopulation of bone marrow cavities and lymphoid organs of irradiated recipient by bone marrow cells from syngeneic hind limb transplant. Lewis rats received total body irradiaton of 8 Gy followed by orthotopic transplantation of syngeneic limb or i.v. infusion of equivalent amount of bone marrow cells. In control experiments the hind limb was shielded with lead plate during total body irradiation.Ten daysafter irradiation and hind limb transplantation the yield of nucleated cells from tibia was reaching values of normal animals. In rats receiving i.v. bone marrow cell infusion it was 40% of control values and in rats repopulated from shielded own hind limb it was 60% of controls. In allgroups a higher percentage of early and immediate normoblasts and a reduced pool of juvenile and segmented neutrophils was observed. Thirty days after irradiation and repopulation procedures all parameters were returning to normal levels in each group. The results indicate that bone marrow cell transplantation in hind limb graft is highlyeffective in lethally irradiated animals in reconstituting bone marrow.

Keywords: Bone Marrow, Stromal Cells, cellular repopulations, Transplantation