Аннотация:We have previously reported prolonged in vitro maintenance of human bone marrow progenitor cells using a serum‐free (SF) liquid culture system. The present study was undertaken to determine recombinant growth factor (rGF) requirement of long‐term marrow culture (LTMC) in absence of exogenous serum, to avoid interference of any undefined components. Our data clearly show that the presence of serum is a major obstacle to the correct evaluation of rGF activity. However, in SF conditions the sequential analysis of these rGFs, alone or in combination, clearly showed a stimulating activity of interleukin 3 (IL3), granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) and erythropoietin (EPO) on granulopoiesis and erythropoiesis. Indeed, the cumulative number of progenitors recovered during an 8‐week period exceeded the initial input by a fractor of 1·7 for granulocyte‐macrophage (CFU‐GM), of 3 for erythroid blast‐forming units (BFU‐E) and of 5·45 for CFU‐E when EPO, GM‐CSF and IL3 were combined. This study has confirmed that the system is able to sustain haematopoiesis for 8 weeks in a way similar to that in serum‐dependant LTMC, despite diminished stromal adherent layer development which never covered more than 50% of the flask surface. We conclude that this defined SF‐LTMC system provides a reproducible technique for studying human haematopoiesis.
