The study of mechanisms by which animals tolerate environmental extremes may provide strategies for preservation of living mammalian materials. Animals employ a variety of compounds to enhance their survival, including production of
disaccharides,
glycerol, and antifreeze compounds. The cryoprotectant
glycerol was discovered before its role in amphibian survival. In the last decade,
trehalose has made an impact on freezing and drying methods for mammalian cells. Investigation of
disaccharides was stimulated by the variety of organisms that tolerate
dehydration stress by accumulation of
disaccharides. Several methods have been developed for the loading of
trehalose into mammalian cells, including inducing
membrane lipid-phase transitions, genetically engineered pores, endocytosis, and prolonged cell culture with
trehalose. In contrast, the many
antifreeze proteins (AFPs) identified in a variety of organisms have had little impact. The first AFPs to be discovered were found in cold water fish; their AFPs have not found a medical application. Insect AFPs function by similar mechanisms, but they are more active and recombinant AFPs may offer the best opportunity for success in medical applications. For example, in contrast to fish AFPs, transgenic organisms expressing insect AFPs exhibit reduced
ice nucleation. However, we must remember that nature's survival strategies may include production of AFPs, antifreeze
glycolipids,
ice nucleators, polyols,
disaccharides, depletion of
ice nucleators, and partial desiccation in synchrony with the onset of winter. We anticipate that it is only by combining several natural low temperature survival strategies that the full potential benefits for mammalian cell survival and medical applications can be achieved.