Bone marrow reconstitution of lethally irradiated canines using autologous bone marrow fractions obtained by counterflow centrifugation-elutriation.

Canine bone marrow fractionated by counterflow centrifugation-elutriation results in three areas of nucleated cell recovery. Fraction 1 accounts for 50% of the total nucleated cells and 25-40% of the total recovered CFU-GM activity. Fraction 2 contains less than 2% of the total nucleated cells and less than 0.2% of the CFU-GM activity. Fraction 3 accounts for approximately 50% of the total nucleated cell recovery and 60-75% of the total recovered CFU-GM activity. Animal survival was not directly correlated with the levels of CFU-GM activity in the transfused fractions. Autologous infusion of these fractions into irradiated canines (9 Gy, 0.1 Gy/min) resulted in distinct survival profiles. Canines receiving autologous fraction-2 cells showed no haematological reconstitution, with death occurring on days 10-11 post-irradiation. Canines receiving autologous fraction-3 cells showed limited myeloid repopulation of both the bone marrow and peripheral blood with a mean survival time for 24 d. Canines receiving autologous fraction-1 cells showed complete haematological reconstitution after 48 d and long-term survival. The data may indicate a separation or enrichment of pluripotential stem cells (fraction 1) from committed myeloid progenitor cells (fraction 3).