GCSF augments post-progenitor proliferation in serum-free cultures of myelodysplastic marrow while ATRA enhances maturation.

All-trans retinoic acid (ATRA) and granulocyte colony stimulating factor (GCSF) are potential inducers of myeloid progenitor cell growth and neutrophil differentiation in myelodysplasia (MDS). We have compared the effects of ATRA and GCSF on the colony growth of 10 MDS marrows, in semi-solid and liquid serum-free mononuclear cell (MNC) cultures, supplemented with a mixture of stem cell factor (SCF), interleukin 3 (IL-3) and granulocyte-monocyte colony stimulating factor (GmCSF) (SIGm mix), which is fully-supportive for myeloid and erythroid (with erythropoietin (EPO)) colony formation in normal marrow. Only 1/10 MDS patients produced normal granulocyte-macrophage colony-forming cell (GmCFC) numbers, under SIGm conditions and erythroid colonies (ECFC) were subnormal in all patients. ATRA (10(-7) M) increased GmCFC numbers (P=0.05) in semi-solid cultures of normal, but not MDS marrow MNC and decreased erythroid colonies in cultures of marrow from either source (P=0.008 and P=0.0001 for normal and MDS, respectively). ATRA enhanced neutrophilic maturation in liquid cultures of both normal and myelodysplastic CD34 + ve cells, as detected by conventional morphology and acquisition of CD15. In contrast to ATRA, GCSF increased Gm colony size but not numbers in semi-solid cultures of normal marrow MNC, which suggests the cytokine augments post-progenitor amplification. This would explain why GCSF increased cell yields in liquid cultures of normal and MDS MNC while GmCFC accumulation remained unchanged. GCSF, though, increased Gm colony numbers in semi-solid cultures of MDS marrow MNC (P=0.014) so that 4/10 patients now grew colonies within the normal range. This was again probably due to increasing clone size, so that some clusters, the numbers of which may be elevated in MDS, were now scored as colonies. Overall, these data indicate that ATRA can enhance the maturation of the progeny of MDS GmCFC whilst GCSF can augment their amplification.