Principles of Genetics and Breeding

9.1.2 Risks associated with cryopreservation

The phenomena that can cause damage to cells during cryopreservation are mainly occurring during the freezing stage, and include, solution effects, extracellular ice formation, dehydration and intracellular ice formation.

Many of these effects can be reduced by cryoprotectants. When the frozen stage is reached, the preserved material is relatively safe from further damage. However, estimates based on the accumulation of radiation-induced DNA damage during cryogenic storage have suggested a maximum storage period of 1000 years.

Solution effects

As ice crystals grow in freezing water solutes are excluded, causing them to become concentrated in the remaining liquid water. High concentrations of some solutes can be very damaging.

Extracellular ice formation

When tissues are cooled slowly, water migrates out of cells and ice forms in the extracellular space. Too much extracellular ice can cause mechanical damage to the cell membrane due to crushing.

Dehydration

The migration of water causing extracellular ice formation can also cause cellular dehydration.The associated stresses on the cell can cause damage directly.

Intracellular ice formation

While some organisms and tissues can tolerate some extracellular ice, any appreciable intracellular ice is almost always fatal to cells.