Hemopoietic support capacity of W/WV femurs and tibias

We evaluated the capacity of "stromal stem cells" of the bones of W/WV mice to effect regeneration of functional "stromal" tissue by implanting femurs and tibias from congenic W/WV and +/+ mice subcutaneously into congenic mice of normal hematologic phenotypes. Eight weeks after implantation, we assayed the hemopoietic progenitor cell contents of the bones. Pluriopotent hemopoietic stem cells (CFUs) were assayed by the spleen colony forming assay in lethally irradiated CAF1 mice. Granulocyte/macrophage progenitor cells (CFUGM) and early erythroid (BFUe) and late erythroid (CFUE) progenitor cells were assayed in agar and methylcellulose semi-solid culture systems, respectively. total cellularity was greater in implanted W/WV femurs and tibias than in +/+ femurs. Although there was substantial variation in the repopulation of W/WV femurs compared to that of +/+ femurs, on the whole, in the W/WV implanted femurs, the numbers of CFUs may have been slightly less and the numbers of maturer progenitor cells slightly greater than they were in the +/+ femurs. All of the progenitor cells assayed were more numerous in the implanted W/WV tibias than in the +/+ tibias. These findings suggest that "stromal stem cells" of W/WV marrow are not defective. In addition, the fact that there were more CFUs in th W/WV that in the +/+ tibias suggests that the CFUs which are native to the implanted bones are not needed to effect reconstitution of normal numbers of CFUs in the implants as all of the CFUs detected in W/WV femurs must have come from the host, for W/WV CFUs do not form surface spleen colonies and, therefore, would not have been counted.