In vitro growth and hemopoietic differentiation of mouse bone marrow-derived adherent stromal cells in long-term culture: formation of spheroidal bodies mimicking hemopoietic anlagen.

A novel method is reported for in vitro growth and hemopoietic differentiation of mouse bone marrow-derived adherent stromal cells in long-term marrow cultures. The cultures were done in 50 ml conical tubes with cell suspension in 10 ml of growth medium. The first stage was to form a layer of adherent stromal cells to extend over the entire area of the tube bathed by the medium. The second stage was to develop small spheroidal bodies (1 to 3 mm in diameter) firmly anchored to the substratum of adherent stromal cells. The spheroidal bodies consisted of an outer layer of stromal (primitive mesenchymal) cells, and an inner core of mostly round and primitive hemopoietic cells. Some degree of differentiation into hemopoietic cell lines was also seen in the central core of some spheroidal bodies. These findings show similarities between the spheroidal body formation and the early events of hemopoiesis in human fetal bone marrow, and suggest that the bone marrow stroma cultured in vitro is multipotential and capable of modulation and transformation into stromal and hemopoietic precursor cells.