On the Origin of Hematopoietic Stem Cells after Local Marrow Extirpation

The early hematopoietic regeneration in a depopulated segment of femur shaft is compared in +/+ and W/Wv mice and in W/Wv mice previously treated with +/+ marrow. Since the W/Wv mouse has an intrinsic CFU deficiency on spleen colony assay and since immigrant cells play a negligible role in the onset of regeneration after marrow extirpation, the W/Wv(+/+) chimera provides a model for evaluation of the contribution of residual cells to the regenerative program. There was little difference in the relative recovery of CFU in +/+, W/Wv, and W/Wv-(+/+), Moreover, +/+ derived CFU were responsible for nearly all of the CFU repopulation in chimeric mice. Thus, recovery of hemic cellularity must be due to residual stem cells rather than to stem cells derived by transformation of more primitive mesenchymal elements. The residual CFU are probably intimately associated with bone, most likely within the endosteum and haversian system.