Abnormalities of adherent layers grown from bone marrow of patients with myelodysplasia.

Myelodysplastic syndromes (MDS) are characterized by a clonal disorder of haemopoiesis with defective growth in vitro. The long-term culture system was used to examine aspects of stromal function in MDS patients. Primary long-term cultures of MDS bone marrow showed poor myelopoiesis with progenitors being detected for a median 3.5 weeks (n = 12) compared with 18 weeks in cultures of normal marrow (n = 10; P < 0.0001). The haemopoietic function of adherent layers was assessed in secondary co-cultures seeded with 5 x 10(6) cord blood mononuclear cells on irradiated normal (n = 27; aged 38-82 years) or MDS (n = 32; aged 41-86 years) adherent layers (> 60% confluent). The median myeloid progenitor number/cord blood co-culture was 135 in 5-week-old cultures with normal adherent layers and 22 in those with MDS layers (P < 0.0001). Myeloid colonies were detectable for a median 11 weeks with normal adherent layers and 6 weeks with MDS adherent layers (P < 0.0001); erythroid colonies were detectable for 7 weeks (normal) compared with 5 weeks (MDS) (P < 0.01). The differences in granulocyte-macrophage colony forming unit (CFU-GM) generation were not related to patient age. Cells from adherent layers of at least half of the primary normal (n = 48) and MDS (n = 26) long-term cultures expressed cytokines [interleukin (IL)-3, IL-1 beta, thrombopoietin (Tpo) and erythropoietin (Epo)] and receptors for retinoic acid (RAR alpha) [IL-2, IL-3, macrophage colony stimulating factor (M-CSF) (Fms) and Tpo (Mpl)]. Only IL-1 beta expression was reduced in week-5 MDS cultures compared with those from normal marrows (P < 0.05). There was also a highly significant decline in IL-1 beta expression in normal (but not MDS) adherent layers between week 5 and week 10. Thus, the adherent layers in cultures grown from MDS patients were haemopoietically defective and showed abnormal IL-1 beta expression.

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.