LOCAL CLONAL ANALYSIS OF THE HEMATOPOIETIC SYSTEM SHOWS THAT MULTIPLESMALL SHORT-LIVING CLONES MAINTAIN LIFELONG HEMATOPOIESIS IN RECONSTITUTED MICE

We describe here a technique to study the clonal contribution of primi tive stem cells that account for long-term hematopoiesis in the same m ouse over a 14-month period. Specifically, irradiated recipient female mice were transplanted with retrovirally marked male hematopoietic pr ogenitors. Bone marrow was then collected repeatedly from local sites from the same mice throughout a 14-month period and injected into seco ndary irradiated recipients for analysis of donor retrovirally marked day-ii colony-forming unit-spleen (CFU-S-11). We have tracked the temp oral in vivo fate of 194 individual CFU-S-derived cell clones in 38 mi ce reconstituted with such retrovirally marked bone marrow cells. Our data show that long-term hematopoiesis is maintained by a large number of simultaneously functioning small, short-lived (1 to 3 months) clon es that usually grow locally with little or no dispersion between diff erent regions of the hematopoietic system, Furthermore, the clones tha t disappeared were never detected again. The data suggest that normal hematopoiesis is supported by the sequential recruitment of marrow rep opulating cells into a differentiation mode. (C) 1996 by The American Society of Hematology.