Significance of in vitro cultures in myelodysplastic syndromes.

Bone marrow samples from 20 controls, 41 patients suffering from various types of myelodysplasia and 19 suffering from ANLL were investigated by in vitro cultures. The cultures were stimulated by various concentrations of leucocyte conditioned medium (LCM) and PHA-stimulated conditioned medium (PCM) and were examined after 7 and 14 d. We found that, in clinically stable MDS, growth patterns and dose-response to CM's were mostly within the normal range. With progressive blastic transformation, these features became abnormal with an increase in cluster growth. Clusters responding to a high dose of LCM, persisting after 14 d and enhanced by PCM may represent 'early' clonogenic cells. These clusters were found in progressive MDS with increased numbers of blast cells. Clusters formed by 'late' clonogenic cells were found in normal bone marrow and stable MDS. In ANLL the disturbance of proliferation and maturation seems to be much more pronounced than in progressive MDS with blastic transformation. We conclude that the interpretation of in vitro bone marrow culture data in terms of a disorderly arrangement of clonogenic cells in MDS and ANLL is facilitated by comparing different conditioned medium stimulations and by scoring after different time intervals.