Effect of extracellular ice formation and electrolyte concentration on injury of slowly frozen cells

The mechanism of cell injury during slow freezing of cell suspension was examined by conducting two different kinds of experiments with PC-3 human prostate adenocarcinoma cells. One was a freezing experiment and the other was a pseudo-freezing experiment that exposed cells to a change in NaCl concentration with a synchronized change in the temperature, which mimicked the change in the environment of cells during freezing process. The results indicated that the mechanical stress from extracellular ice crystals played an important role in damaging cells during freezing at relatively higher freezing temperatures, while the solution effect that indicates the effect of increase in the solute concentration became more significant at lower freezing temperatures. A non-monotonous effect of temperature on cell injury due to the solution effect was also found, suggesting that the experimental results at the temperatures above 0°C could not be extrapolated to predict cell survival at sub-zero temperatures.