Physical and nutritional factors in gel culture of mammalian cells.

The growth of human glioma cells, cultured as spherical colonies in agarose gel, stopped after about 10 days for both large and small colonies apparently due to an increased osmolality in the gel. When osmolality was kept under control by addition of distilled water, growth continued. However, a continuous increase in the population-doubling period, similar for both large and small colonies, then was observed. The increase persisted although excess amounts of nutrition were added. When the cells were cultured in liquid suspension above a thin layer of agarose gel and most of the medium was repeatedly changed, the colonies continued to grow beyond the limits in gel cultured. HeLa and hamster embryonic lung cell colonies showed a growth pattern in agarose gel similar to the glioma cells. The results imply that the osmolality must be kept under precise control to prevent growth inhibition. However, it seems difficult to ascertain optimal growth in gel culture for more than about 2 weeks probably because of the accumulation of toxic products.