| Abstract: | Human placenta-conditioned medium (HPCM) has been reported to stimulate colony formation by human granulopoietic stem cells (CFU-C) in vitro. The present work was performed to further characterize this colony formation. The majority of HPCM batches tested stimulated colony growth equivalent to recombined human leukocyte feeder layers with optimal cellular composition. A broad plateau of the dose-response curve of HPCM was found. A linear correlation exists between the number of marrow cells plated and the number of colonies grown. Optimal duration of culture is between 9 and 11 days. Colonies are large and tend to be compact. Admixture of mature granulocytes does not affect the colony growth pattern under optimal culture conditions. These data document that HPCM is a suitable source of colony-stimulating activity for the routine assay of human CFU-C. Due to the constant colony stimulation, HPCM appears particularly valuable for longitudinal studies of human CFU-C. |
