Vitrification

  • In the fertility world, vitrification is used for cryopreservation of eggs, embryos, and sperm. Generally speaking, vitrification is a method of transforming something into a glass-like substance. It comes from the Latin root vitreum, which means glass. Vitrification technology is used to transform sand into glass, to give ceramic pots their glossy finished look, and to stabilize nuclear waste for safer disposal.
  • Vitrification has improved the success of cryopreservation. The old methods involved a slow freeze, while vitrification is extremely quick.
  • How quick? During the vitrification, an embryo or egg is cooled off by thousands of degrees per minute.

What Is Vitrification?  How Does It Work?

  • Until recently, the only method for freezing oocytes (or unfertilized eggs) was a slow-freezing method. This worked okay for freezing sperm or embryos. However, for eggs, the slow freeze process had many problems.
  • Ice crystals were a major issue. Eggs contain a lot of water, compared to sperm and even embryos. Freezing eggs led to crystal formation. These crystals broke down the egg.
  • To help minimize the number of ice crystals, scientists would remove some of the water. But it's impossible to remove all the water.
  • When the eggs were thawed, they were damaged and frequently unusable. Fertilization and pregnancy rates for these slow-frozen eggs were low.
  • With vitrification, the freezing process is so fast that ice crystals don’t have a chance to form. Vitrification has made egg freezing a much more viable option for women.
  • Vitrification is also being used for embryo and sperm cryopreservation. Research is ongoing, but so far, pregnancy rates seem higher with vitrification, according to a 2014 study.

How Does   Vitrification of Eggs Work?

  • Vitrification of eggs requires high concentrations of cryopreservants, or an anti-freeze substance. Because anti-freeze is potentially toxic to the egg, the technique requires special care.
  • The oocyte is first placed in a bath with a lower concentration anti-freeze. The solution also contains some sucrose, or sugar, to help draw water out of the egg. Next, the egg is placed in a highly concentrated bath of anti-freeze for less than one minute, while being instantaneously frozen.
  • The eggs can then be stored in special cryogenic freezers, made for this purpose. The eggs are held in tiny straws.
  • When it's time to thaw the egg, the oocyte must be warmed quickly and removed from the solution immediately.
  • Once thawed, the egg can be fertilized using IVF with ICSI. ICSI involves taking a single sperm and injecting it directing into the egg. Regular IVF isn’t possible because the freezing process hardens the eggs outer membrane.