REGULATION OF PROLIFERATION AND MOVEMENT OF HUMAN GLIA-LIKE CELLS IN CULTURE

The control of DNA synthesis and locomotion have been investigated in vitro in serially propagated astrocyte-like lines from normal adult human brain. DNA synthesis was measured autoradiographically as the percentage of cells showing uptake of tritiated thymidine during a 24 h period. In the period after subcultivation when the cell number increased rapidly, about 40-80% of the cells participated in DNA synthesis. After 10-15 days when the number of cells had stabilized at a level of about 60,000/cm2, the percentage of labeled cells dropped to 1% or less, indicating strict control of DNA synthesis in a complete monolayer. Addition of fresh medium caused a slight temporary increase of DNA synthesis in stationary layers. Analysis of the length of the cell cycle periods gave the following values: T, 22 h, G1, 8.5 h, S, 8 h, G2, 4.5 h, M, 1 h. There was no evidence for division by amitosis. Cell locomotion was analysed by time-lapse cinematography. Glia cells were mobile in a sparse culture, but had a tendency to form adhesions along areas of mutual contact. These were not always sufficiently strong to prevent cytoplasmic and even nuclear overlapping. When a complete monolayer had formed, the cells were essentially immobile and no ruffled membranes were seen. The results indicate that adult human glia cells have unusually well developed growth control mechanisms in vitro and should lend themselves well to the experimental study of such controls. © 1969.