Freeze-dried eggs may stall biological clock
Technique could one day let women preserve, rehydrate ova
Those striving to help women put their biological clocks on hold have come up with the next audacious step in hightech baby making: freeze-dried eggs that could be preserved for years.
In what could be the newest frontier in assisted reproduction, scientists are working on a technique that may one day allow a woman to store her freeze-dried eggs at home and rehydrate them when she’s ready to have a baby.
Once resurrected, the eggs would be fertilized with sperm and any resulting embryo transferred back into the woman.
In one experiment, researchers “powderized” 30 cow eggs, 23 of which were successfully revived, according to a report in New Scientist magazine.
The technique has already been used to freeze dry stem cells and red blood cells. “Now, the next step is eggs,” Amir Arav, the technology’s developer, told Postmedia News in an interview from Tel Aviv, Israel. Arav, of Core Dynamics, a biotechnology company focused on advanced cell and tissue preservation, says freezedrying could be a safer alternative to today’s more conventional method of egg freezing, where eggs are flash frozen and then stored in tanks of liquid nitrogen at fertility clinics.
With liquid nitrogen, the eggs can become contaminated or the cells can become damaged if the temperature isn’t perfectly controlled. Home storage would also be far cheaper and more convenient, Arav said.
The new technique involves using an ultrafast cooling technique called vitrification that allows no time for cell-destroying ice crystals to form in the eggs. Instead, the eggs are cooled into a glasslike solid state.
Fertility clinics across Canada are already using vitrification to cryopreserve eggs.
Arav says his approach involves using a small volume of a “secret” solution and rapid cooling using a liquid-nitrogen “slush.”
Next, the vitrified eggs are placed in a low-pressure chamber under low temperature for 24 hours for full drying. The glass water changes from a solid to a gas in a process called desorption. The result: lyophilized — or freeze-dried — eggs that could remain in a dry state at room temperature for years, Arav says.
The eggs would need to be stored in vacuum-sealed packs and protected from light, he added. Arav is working with collaborators from Yale University and the University of Teramo in Italy. In experiments with cow eggs, fluorescent staining showed the rehydrated eggs were alive, as well as the cluster of nourishing cells called the cumulus oophorus that surround the egg.
“Of course, we need to show that they can be fertilized and produce a normal embryo and a normal pregnancy,” Arav said. “This is just the beginning.”
About one-third of Canada’s fertility clinics are now using vitrification to freeze and bank eggs for fertility preservation, effectively allowing women to put their biological clocks on hold. In experienced labs, 80 to 90 per cent of eggs survive the freeze-thaw process and, as the technology advances, pregnancy rates are increasing.
In October, the American Society for Reproductive Medicine decreed the technique no longer “experimental,” saying that, in young patients, egg freezing has been shown to produce pregnancy rates comparable to IVF cycles using fresh eggs.
Still, the U.S. group stopped short of endorsing widespread use of egg freezing simply to defer pregnancy.
Canadian reproductive biologist Dr. Roger Pierson says some “serious testing” needs to be done in animals before experiments with freeze-dried eggs move into humans.
“This is an intriguing idea that bears our deep consideration, but there is a lot of work to be done.”