Kinetic analysis of cell population growth during cultivation in vitro

XL-2 cells (Xenopus laevis) were used for kinetic analysis of cell population growth. The dependence of the time of cell duplication on the percentage of cells in the G0 phase of the cell cycle was studied and described by a mathematical expression. Possible causes of the changes in the ratio between the percentage of cells in the cell cycle and that in the G0 phase were analyzed. These are the decrease in the percentage of cells in the G0 phase due to the increase in the number of dividing cells, their position in the cell islets, the number of nuclei, the relative position of cells in the G0 phase. It was shown that the loss of the free edge by cells during their transition to the second layer of the cell islets without any changes in spreading led to a significant increase in the percentage of cells in the G0 phase. The percentage of cells in the G0 phase increased about five times for multinuclear cells. Analysis of the position of cells in the G0 phase showed that these cells were mostly in groups of two, three or four. Studies of a real cell culture in the logarithmic phase of growth (48-120 h of cultivation) showed that the percentage of cells in the G0 phase did not virtually change and all processes were equalized by one another. We propose a new method to determine the cell cycle duration under conditions from the time of cell culture duplication and the data on the percentage of cells in the G0 phase. This method can be used when traditional approaches using BrdU or [3H]]thymidine are difficult to implement or are unacceptable.