• Marrow stroma;
  • Long-term culture;
  • Microenvironment;
  • Umbilical cord blood


Utilizing long-term in vitro culture techniques, we characterized the cellular composition and functional attributes of the human in vitro bone marrow stromal micro-environment. Morphologic, specific cytochemical and immunologic methods demonstrated that the marrow stromal adherent layer (AL) reached confluency at two to three weeks, and was comprised of 60%–70% fibroblastic cells, 10%–20% endothelial cells, 10%–20% monocyte/macrophages and 5%–10% fat-laden adherent cells. These proportions of cell types persisted for at least three months concomitant with proliferation of CFU-gm and BFU-e. In contrast, umbilical cord blood cells did not form a stromal AL despite persistence of hemopoietic progenitor cell proliferation. These findings provide a basis for improved understanding of cellular interactions regulating hemopoiesis.