Effect of 5637-conditioned medium on peripheral blood granulocyte-macrophage progenitors in normal subjects and patients with the myelodysplastic syndrome

Control of pH in human long-term bone marrow cultures with low-glucose medium containing zwitterion buffer lengthens the period of haemopoietic activity

Primary long-term bone marrow cultures grown in 40 mM HEPES-buffered McCoy's 5A medium produced granulocyte-macrophage colony-forming units (CFU-GM) for a median of 9 weeks compared with 7 weeks with CO2/bicarbonate-buffered cultures. Reducing the medium glucose concentration (from 12.5 to 2.75 mM) extended the culture longevity to 17 weeks. The median period of erythroid colony detection increased from 6 to 8 weeks. Secondary cultures (5 x 106 cord blood mononuclear cells seeded on irradiated stroma) showed statistically similar myeloid and erythroid longevity to primary cultures. Improved control of medium pH significantly improved the capacity of long-term stromal layers to maintain stem cells in vitro.

Growth response to cytokines of circulating myeloid progenitors from myelodysplastic patients at diagnosis and more than 600 days after diagnosis

Myeloid colony growth from the peripheral blood of myelodysplastic (MDS) patients was assessed for abnormal in vitro response to haemopoietic growth factors (granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 (IL-1), interleukin-3 (IL-3)). Abnormal colony growth, increased or reduced, was observed with each of the factors. No specific growth pattern was related to any of the French-American-British classification (FAB) types of disease. MDS patients who had survived greater than 600 days after diagnosis (n = 34) showed significantly fewer abnormalities than patients assayed at the time of diagnosis (n = 37), the major difference being less frequent stimulation of colony growth. These findings indicate that the time of sampling relative to diagnosis needs to be considered when interpreting the in vitro response to growth factors of myeloid colonies from MDS patients.

Colony-cluster ratio and cluster number in cultures of circulating myeloid progenitors as indicators of high-risk myelodysplasia

Circulating myeloid progenitors were assayed in 172 normal subjects and 147 patients with myelodysplastic syndrome (MDS). Patients whose cultures had colony/cluster ratios (CCR) less than 0.3 had significantly shorter survival periods than comparable patients with CCR greater than 0.3. A second prognostic indicator, which complemented CCR, was identified in patients with less than 5% blasts. Median survival was significantly reduced in patients with greater than 15 clusters/ml blood despite colony and cluster numbers being predominantly within the normal range. Characteristic differences were found in three FAB groups large enough to allow statistical analysis. Survival amongst patients with refractory anaemia with excess of blasts (RAEB) was related to CCR and was independent of cluster number. Amongst sideroblastic patients (SA) survival related only to cluster number. Refractory anaemia (RA) patients included individuals in both high-risk groups with only three patients out of 64 showing both features. Amongst all the MDS patients, those with CCR greater than 0.3 and less than 15 clusters/ml blood formed a low-risk group (n = 60) with a relatively good prognosis of whom 85% survived the study period (median duration 938 d) including 94% of those in this group with less than 5% marrow blast cells.

Stimulation of myeloid colony growth from peripheral blood by medium with an initially low osmolality

The clonal growth of myeloid colonies from peripheral blood was maximal when cultures were established with an initial osmolality of 220 mosmol/kg which increased during incubation as a result of partial drying. When osmolality was stabilized by secondary humidification, the optimum osmolality was 270 mosmol/kg, but growth was always two- to fivefold less than similar cultures established at low osmolality and incubated on an open shelf. Cultures established at 270 mosmol/kg or above were statistically similar whether or not drying was eliminated. Maximum colonies were apparent after 14 days incubation under both conditions; addition of conditioned medium did not alter the pattern of growth. The greater sensitivity of cultures established at 220 mosmol/kg is advantageous when assaying circulating progenitors in pathological conditions where a low number of granulocyte/macrophage colony-forming units is common.

Clonal growth of haemopoietic progenitor cells from myelodysplastic marrow in response to recombinant haemopoietins

The growth factor requirements of granulocyte-macrophage (GM) and erythroid marrow progenitor cells from 12 myelodysplastic (MDS) patients have been analysed. GM progenitors from two of six patients who grew normal numbers of colonies in response to conditioned medium + erythropoietin (5637CM + Epo) showed defective responses to either GMCSF and/or IL-3. Of all the recombinant factors tested (IL-3, IL-1, GCSF, GMCSF, MCSF), GMCSF was the strongest stimulator of myeloid clonal growth, inducing normal numbers of GM colonies from marrow of six patients (two of whom were neutropenic). Erythroid colonies were low in 5637CM + Epo-supplemented cultures of marrow from all but one patient and remained poor in the presence of any of the haemopoietins. tested. Supraoptimal doses (for normal marrow) of these haemopoietins improved colony growth in only one patient (GM colonies in response to IL-3). Combinations of factors were also largely ineffective at raising myeloid or erythroid colony numbers. These data indicate that the defective response of MDS progenitor cells to growth factors is not amenable to experimental manipulation of recombinant factor levels or combinations. Clonal assays might suggest a role for GMCSF therapy in a subpopulation of neutropenic MDS patients but their potential now needs to be evaluated in association with clinical trials.