Intracellular ice formation is affected by cell interactions

Cell-to-cell and cell-to-surface interactions are important to the structur e and function of tissues. These interactions are also important determinan ts of low-temperature responses in tissues. Four in vitro models using hams ter fibroblast cells in tissue culture were used to investigate the influen ce of cell-cell and cell-surface interactions on intracellular ice formatio n in these systems. The four models were: (a) single cells in suspension; ( b) cells individually attached to glass with only cell-to-surface adhesion; (c) colonies of cells attached to glass with both cell-cell and cell-surfa ce interactions; and (d) multicellular spheroids with extensive cell-cell c ontacts. Cryomicroscopy was used to monitor the prevalence and kinetics of intracellular ice formation after ice nucleation in the extracellular solut ion. The temperature for intracellular freezing in 50% of the cells was sig nificantly affected by both cell-cell and cell-surface interactions. There was also evidence of intercellular nucleation through cell-cell interaction s. The results indicate that cell-cell and cell-surface interactions play a significant role in the low-temperature response of tissue systems. (C) 19 99 Academic Press.