| Abstract: | DNA synthesis and cell division were measured in serum-free cultures of human normal diploid glial cells maintained in MCDB 105 medium. In growth factor-free cultures the cells remained viable but the cell number was essentially constant. Supplementation with 10 ng of epidermal growth factor or platelet-derived growth factor per ml significantly stimulated DNA synthesis and cell multiplication. Growth occurred both when cells were allowed to settle in serum-containing medium and when cells were plated in serum-free medium. In the latter type of cultures, the cell yield was improved bu incubating the cells in collagen-coated dishes. The use of a miniclone technique allowed the analysis of cell multiplication induced by platelet-derived growth factor at the clonal level and demonstrated that the growth factor induced several cell cycle rounds in a large fraction of clones. The results show that normal cells grown in a recently developed synthetic medium (MCDB 105) supplemented with pure growth factors may multiply without the addition of plasma-derived factors ("progression factors"). It is suggested that the need fo progression factors may simply depend on the composition of the synthetic nutrient medium. |
