New approach for frozen preservation of tissues, organs

Scientists have discovered a new approach to ice-free cryopreservation that could allow a much wider use of extreme cold to preserve tissues and even whole organs for later use.
"This could be an important step toward the preservation of more complex tissues and structures," said Adam Higgins, an associate professor in the Oregon State University School of Chemical, Biological and Environmental Engineering in US.
Cryopreservation has already found widespread use preserving semen, blood, embryos, plant seeds and some other biological applications.
However, it is often constrained by the crystallisation that occurs when water freezes, which can damage or destroy tissues and cells, Higgins said.

This is similar to what happens to some food products when they are stored in a freezer, and lose much of their texture when thawed.
To address this, researchers have used various types of cryoprotectants that help reduce cell damage during the freezing process - among them is ethylene glycol, the compound often used in automobile radiators to prevent freezing.

One problem is that many of these cryoprotectants are toxic, and can damage or kill the very cells they are trying to protect from the forces of extreme cold, Higgins said.
Scientists developed a mathematical model to simulate the freezing process in the presence of cryoprotectants, and identified a way to minimise damage.

They found that if cells are initially exposed to a low concentration of cryoprotectant and time is allowed for the cells to swell, then the sample can be vitrified (ice-free cryopreservation) after rapidly adding a high concentration of cryoprotectants. The end result is much less overall toxicity, Higgins said.
The research showed that healthy cell survival following vitrification rose from about 10 per cent with a conventional approach to more than 80 per cent with the new optimised procedure.
"The biggest single problem and limiting factor in vitrification is cryoprotectant toxicity, and this helps to address that," Higgins said.
"The model should also help us identify less toxic cryoprotectants, and ultimately open the door to vitrification of more complex tissues and perhaps complete organs," he said.

This would make many more applications of vitrification feasible, especially as future progress is made in the rapidly advancing field of tissue regeneration, in which stem cells can be used to grow new tissues or even organs.
Tissues could be made in small amounts and then stored until needed for transplantation. Organs being used for transplants could be routinely preserved until a precise immunological match was found for their use.
Conceptually, a person could even grow a spare heart or liver from their own stem cells and preserve it through vitrification in case it was ever needed, Higgins said.
The study was published in the journal PLOS ONE.