Mixed haematopoietic colony formation via immature blast cell clusters on foetal mesenchymal cell layers distinguishes stem cells from peripheral blood, cord blood, bone marrow and blood stem cells mobilized by granulocyte‐macrophage colony‐stimulating factor

Abstract: Multilineage colony formation was evaluated from healthy donors' bone marrow (BM), peripheral blood (PB) and cord blood (CB) and compared with blood stem cell (BSC) harvests of sarcoma patients mobilized with granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). The test was a modified CFU‐blast assay performed with and without an irradiated foetal mesenchymal cell layer (HFFF). These non‐transformed mesenchymal cells served as a good source of haematopoietically active stroma cells in that cytokine expression patterns (interleukin (IL)‐6, granulocyte (G)‐CSF, GM‐CSF) and adhesion molecules on HFFF cells were qualitatively identical to BM‐derived fibroblasts, but the expression density of adhesion receptors was significantly higher. This HFFF layer stimulated blood stem cells of GM‐CSF‐treated patients significantly more than a cocktail of exogenous growth factors with IL‐1, IL‐6, and stem cell factor (SCF). The reverse was true for multilineage colonies from healthy donors' PB, BM, and CB. According to these results, stem cells of GM‐CSF‐treated patients are functionally distinct due to their dependence on stroma‐derived factors and/or matrix‐adhesion interactions and can be reproducibly evaluated on these mesenchymal cells.