Stem cell quality following irradiation: Comparison of 125IUdR uptake in the spleen and number and size of splenic colonies in bone marrow transfused, fatally irradiated mice.

In order to study radiation induced residual injury in hemopoietic stem cells the number and size of spleen colonies were compared to the incorporation of 125I-labeled iododeoxyuridine (125IUdR) in the spleen after transfusion of irradiated bone marrow cells in the lethally irradiated mouse. Bone marrow cells from non-irradiated or from mice that had been given 3,000 rad in daily 50 rad increments 5 days per week were used 3 months after termination of irradiation. Marrow cells from donor mice given 50 rad immediately prior to the experiment were comparably used to study acute radiation effect. The splenic proliferation factor (PF) (ratio of 5th to 3rd day-125IUdR incorporation) of 7.3 ± 0.2 for the 3,000 rad irradiated bone marrow is 44.2% of the control value (16.5 ± 0.9). Spleen colonies produced by stem cells from 3,000 rad mice are 40-50% of the size of colonies produced by nonirradiated stem cells. An acute dose of 50 rad reduced the PF from 20.7 ± 0.9 for controls to 8.0 ± 0.7 for the irradiated bone marrow. This reduction is compatible with the reduction in size and number of the spleen colonies. The cytological appearance of spleen colonies formed from the 3,000 rad and 50 rad irradiated bone marrow was different. The colonies produced by bone marrow from mice given 50 rad immediately before preparing the BM showed extensive karyorrhexis, so called apoptosis, not seen in the colonies produced by BM cells taken from mice 3 months after receiving 3,000 rad in 50 rad increments 5 days per week for 12 weeks.

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