Intracellular ice formation (IIF) is usually lethal. The main concern of the first four years of this grant was to determine details of IIF in oocytes of mice and Xenopus and in yeast. The details included the temperatures at which IIF occurred and the effect of cryoprotectant (CPA) type and concentration on those temperatures. From these studies, we have found that in 1 to 1.5 M EG or glycerol, nucleation occurs near -400C, the homogeneous nucleation temperature of water. But in lower concentration, it occurs by heterogeneous nucleation, with a high probability that external ice is the nucleator. (See papers 139-140, 142-143, 145-147, 149-150, 153 by Mazur, Seki, and Kleinhans in the Progress Report Publication List). In the past three years under the current renewal grant, we have shifted the emphasis to determining physical events during vitrification and recrystallization of internal ice, and their effects on survival. The most important finding has been that under certain conditions, the formation of intracellular ice is not lethal;what is lethal is the growth of those crystals during warming by recrystallization. This translates to the fact that the warming rate plays the dominant role in determining survival of """"""""vitrified"""""""" mouse oocytes-and not the cooling rate. (Papers 157, 154, and 160). The current renewal application builds directly on the items in the above paragraph. Up to now, we have based """"""""survivals"""""""" on the retention of osmotic properties by thawed cells and by the morphological normality of cell membranes and cytoplasm. The argument was that those sets of conditions that yielded low """"""""survivals"""""""" based on these criteria, would almost certainly exhibit very low or zero functional survival. We found, however, that a number of conditions yielded osmotic/morphological survivals of 80 to 90% if the warming rates were very high;the cooling rate had less or no effect. Now we intend to determine the functional survival of oocytes treated in this way. Another finding has been that if the oocytes are warmed >100,0000C/min, some 80% survive osmotically, morphologically, and in their ability to develop to 2-cell embryos even if the vitrification medium is diluted in half. Possibly, even faster warming would permit the use of even more dilute vitrifying solutions. We propose to test this hypothesis by using a special laser to achieve warming rates that are 100- times higher. Most believe that the efficacy of vitrification solutions depends on the very high solute concentrations in them. Another possibility is that their efficacy depends more on the degree to which they osmotically dehydrate the cells prior to initiating cooling to -1960C, We propose to test that hypothesis in a quantitative manner.
The ability to preserve cells at very low temperatures has important implications and applications in such aspects of clinical medicine as assisted reproduction, tissue transplantation, and engineered tissue constructs;in improving agricultural productivity;and in the cost-effective maintenance of the germplasm of genetically important laboratory animals.
|Seki, Shinsuke; Mazur, Peter (2012) Ultra-rapid warming yields high survival of mouse oocytes cooled to -196°c in dilutions of a standard vitrification solution. PLoS One 7:e36058|
|Peckys, Diana; Mazur, Peter (2012) Regulatory volume decrease in COS-7 cells at 22 °C and its influence on the Boyle van't Hoff relation and the determination of the osmotically inactive volume. Cryobiology 65:74-8|
|Peckys, Diana B; Kleinhans, F W; Mazur, Peter (2011) Rectification of the water permeability in COS-7 cells at 22, 10 and 0ýýC. PLoS One 6:e23643|
|Seki, Shinsuke; Mazur, Peter (2011) Stability of mouse oocytes at -80?°C: the role of the recrystallization of intracellular ice. Reproduction 141:407-15|
|Mazur, Peter; Seki, Shinsuke (2011) Survival of mouse oocytes after being cooled in a vitrification solution to -196ýýC at 95ýý to 70,000ýýC/min and warmed at 610ýý to 118,000ýýC/min: A new paradigm for cryopreservation by vitrification. Cryobiology 62:1-7|
|Seki, Shinsuke; Edashige, Keisuke; Wada, Sakiko et al. (2011) Effect of the expression of aquaporins 1 and 3 in mouse oocytes and compacted eight-cell embryos on the nucleation temperature for intracellular ice formation. Reproduction 142:505-15|
|Peckys, Diana B; Mazur, Peter; Gould, Kathleen L et al. (2011) Fully hydrated yeast cells imaged with electron microscopy. Biophys J 100:2522-9|
|Peckys, Diana B; de Jonge, Niels (2011) Visualizing gold nanoparticle uptake in live cells with liquid scanning transmission electron microscopy. Nano Lett 11:1733-8|
|Seki, Shinsuke; Mazur, Peter (2010) Comparison between the temperatures of intracellular ice formation in fresh mouse oocytes and embryos and those previously subjected to a vitrification procedure. Cryobiology 61:155-7|
|Mazur, Peter (2010) A biologist's view of the relevance of thermodynamics and physical chemistry to cryobiology. Cryobiology 60:4-10|
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