Powder women's eggs for home storage
JUST add water and sperm – any romance should be provided separately. In future, women who want to safeguard their fertility may be able to store their eggs at home as a powder. To revive them for an attempt at having a baby, all they would need to do is empty the sachet, add water, fertilise with sperm and implant the embryo.
"You can keep the powder at room temperature forever – and just add water to bring it back to life," says Amir Arav of Core Dynamics in Ness Ziona, Israel, who developed the method. The technique was demonstrated with cow eggs last month at Cryo, a conference on cold-preservation techniques for eggs, sperm and embryos held in Berlin, Germany.
Arav claims that his company's process avoids the expense and complications of storage in liquid nitrogen. During such refrigeration, ice crystals can damage cellular membranes. To avoid this, Arav first soaks the cells in a solution containing substances that displace most of the water in the cells and which help to prevent cold damage to tissue. The protective ingredients include the sugar trehalose, which enables animals such as wood frogs and tardigrades to survive freezing or dehydration. Marinated in this cryoprotectant solution, the eggs are then converted into a glass-like solid state through a process called vitrification. This involves rapid freezing, so that any residual water has insufficient time to form ice crystals. "It takes a tenth of a second to reach -200 °C," says Arav.
Vitrification is used to process human eggs before storage in liquid nitrogen. Now Arav has added a final stage to freeze-dry and "powderise" the oocytes. Residual frozen water is converted directly into a gas by storing the vitrified cells at -55 °C for a day under low pressures, which allows the water to sublime away.
What remains is a powder that can potentially be stored indefinitely. "It must be under a vacuum, without air, oxygen, light, or anything that could damage the cells," says Arav.
Of the 30 cow eggs Arav prepared this way, 23 were confirmed to be viable using a staining test. Arav says the technique already works on red blood cells and on human mononuclear cells from umbilical cord blood (PLoS One, doi.org/d4326g).
"We need to know whether the oocytes can be fertilised after freeze-drying, whether they then form normal embryos, and if they do, the extent to which they implant in the womb and develop into healthy offspring," says Claus Andersen of the University Hospital of Copenhagen, Denmark. "Further, if the vision is for women to take their freeze-dried eggs home with them, will those eggs deteriorate over time or lose their reproductive potential?" he asks. "The freeze-drying needs to be shown to be as good as the conventional method of freezing under liquid nitrogen, and this could take some time."
This article appeared in print under the headline "Powder your eggs for home storage"
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