No stimulative effect of adipocytes on hematopoiesis in long-term human bone marrow cultures.

Long-term cultures of human bone marrow were established for 5-13 wk to study the role of adipocytes in sustaining hematopoiesis. At weekly intervals, the numbers of nucleated cells and granulocyte-macrophage progenitor cells (GM-CFU) in culture were estimated in relation to the numbers of fat-containing cells present in the adherent stroma layer. In these quantifications, the numbers of GM-CFU trapped in the adherent cell layer were considered separately. It was found that the presence of adipocytes did not correlate with more active hematopoiesis. Fat cells appeared at late stages when successful cultures were being exhausted or early in cultures with poor activity. These observations suggest that human marrow continuous hematopoiesis in vitro, unlike hematopoiesis in the analogous murine bone marrow cultures, does not depend on the presence of adipocytes.