BLAST COLONY-FORMING CELL-BINDING CAPACITY OF BONE-MARROW STROMA FROMMYELODYSPLASTIC PATIENTS

A specific stroma function can be quantitatively assessed by counting the stroma-adherent blast cell colonies (CFU-BL) that are formed from normal plastic nonadherent mononuclear bone marrow cells (PNAMNC) afte r a short-term coincubation (''panning'') with the preformed stromal l ayer, In order to obtain information of stroma function in myelodyspla sia (MDS), the ''CFU-BL-binding capacity'' of stroma from normal bone marrow and from patients with MDS were compared, Stromal cell cultures were established from mononuclear bone marrow cells in microplate cul tures cultured with or without 10(-6) M hydrocortisone, CFU-BL-binding capacity was studied by counting blast colonies seven days after pann ing, and the results were expressed as CFU-BL/10(3) PNAMNC, Normal mar row stromal layers bound CFU-BL only if they were cultured with hydroc ortisone, while RIDS stromal layers also bound CFU-BL in the absence o f hydrocortisone. For further studies of the function of RIDS stroma, the effect of growth factors (stem cell factor [SCF], G-CSF, interleuk in 3 [IL-3] and their combinations) on CFU-BL binding by normal or RID S stroma has also been compared, Twenty-hour incubation of the stromal layers with a standard dose (100 ng/ml) of various hemopoietic growth factors (IL-3 alone or in combination with SCF, G-CSF alone or in com bination with SCF) did not have any effect on CFU-BL binding by normal marrow stroma, but increased the CFU-BL binding by stromal layers fro m MDS bone marrow, These findings suggest that although stromal microe nvironment in RIDS is capable of supporting hemopoiesis, bone marrow s troma from RIDS patients differs in some characteristics from the norm al stroma.