Enhanced growth of myelodysplastic colonies in hypoxic conditions

Objective To determine the response of bone marrow progenitor cells from patients with myelodysplastic syndromes (MDS) to culture in physiologic oxygen tension. Methods Methylcellulose progenitor assays using both unfractionated bone marrow mononuclear cells (MNCs) and purified CD34+ progenitors were performed in atmospheric oxygen (18.6% O2) or one of two levels of hypoxia (1% and 3% O2). Assays were performed using normal donor marrow, MDS patient marrow, acute myelogenous leukemia marrow or peripheral blood blasts, chronic phase chronic myelogenous leukemia (CML) marrow MNCs, and blast crisis CML peripheral blood. Results The majority of MDS samples showed decreased colony-forming units (CFU) in 18.6% O2 compared to normal controls, as expected. However, in either 1% or 3% O2, 9 of 13 MDS samples demonstrated augmentation of CFUs beyond that observed in normal controls, with 6 of 13 demonstrating a greater than ninefold augmentation. This effect is cell autonomous, as it persisted after purification of CD34+ progenitor cells. Additionally, the augmented response to physiologic oxygen tension is specific to MDS, as it was not observed in either acute or chronic myelogenous leukemia samples. Conclusion These results suggest that the reported decrease in MDS CFUs reflects greater sensitivity of MDS progenitors or their progeny to the nonphysiologic oxygen tensions routinely used in vitro, rather than a true decrease in progenitor frequency. Importantly, these experiments for the first time describe an experimental system that can be used to study the growth of primary cells from patients with MDS.