PROPERTIES OF PRIMARY MURINE STROMA INDUCED BY MACROPHAGE-COLONY-STIMULATING FACTOR

The ability of purified human macrophage colony-stimulating factor (M- CSF) to accelerate the formation of stromal cells from murine bone mar row cells was investigated. The liquid culture of the marrow cells wit h M-CSF resulted in the formation of monolayers of macrophages on day 7. When the M-CSF was removed on that day and the residual adherent ce lls were cultured in the absence of M-CSF for an additional 7 days, ma ny colonies appeared with cells that were morphologically distinguisha ble from M-CSF-derived macrophages. The appearance of the colonies was dependent on the concentration of M-CSF used at the beginning of the culture. Each colony was isolated as a single clone and analyzed. All clones were negative for esterase staining. These cells did not expres s M-CSF receptor mRNA and did not show a mitogenic response to M-CSF. On the contrary, these cells could be stimulated to proliferate by fib roblast growth factor and platelet-derived growth factor. The polymera se chain reaction analysis of these cells demonstrated constitutive ex pression of mRNA for M-CSF, stem cell factor, and interleukin (IL)-1, but not IL-3. Some clones expressed mRNA for granulocyte/M-CSF and IL- 6. We also examined the ability of the cells to maintain murine bone m arrow high proliferative potential colony-forming cells (HPP-CFC) in a coculture system. Most of the clones showed a significant increase in total HPP-CFC numbers after 2 weeks of coculture, although the extent of stimulation differed among clones. These results suggested that th e colonies established by M-CSF were composed of functional stromal ce lls that were phenotypically different from macrophages. (C) 1997 Wile y-Liss, Inc.