DEVELOPMENTAL HEMATOPOIESIS FROM PRENATAL TO YOUNG-ADULT LIFE IN THE MOUSE MODEL

Five measurements of hematopoietic function were made in the mouse fro m midfetal life to young adulthood. These included two in vivo (day-8 colony-forming unit-spleen [CFU-S8] and day-12 CRT-S [CFU-S12]) and tw o in vitro clonal measurements of hematopoietic stem and progenitor ce lls (high proliferative potential colony-forming cell [HPP-CFC] and CF C of low proliferative potential [LPP-CFC]) as well as an in vitro clo nal measurement of colony-forming unit-fibroblast (CFU-F). The appeara nce, increase, subsequent decrease, and later emergence and increase o f each of these parameters in the fetal-liver, newborn, growing-infant , and young-adult bone marrow were correlated and found to be in paral lel. Exceptions to this included the earlier appearance in the fetal l iver of CFU-F and the relatively differentiated hematopoietic LPP-CFC. The pattern of emergence of these progenitor cell subpopulations in t he fetal Liver may be related, in part to the timing of the hematopoie tic microenvironment development and the relative frequencies of proge nitor cell types in the circulation. This developmental study in the m ouse model describes additional correlations between in vivo and in vi tro colony-forming stem cells and fibroblastic stromal colony-forming cells, and it suggests the dependence of hematopoietic stem cells upon the stromal microenvironment for the necessary conditions for hematop oietic stem cell lodgment, growth, and maturation.