Cold-loving parasites could hold key to preserving human tissues

Yuriy Baglaenko
31 March 2014

Above: Image © istockphoto.com/ZernLiew

Have you ever thought about cryopreserving yourself like Han Solo in Star Wars or Fry in Futurama? In other words, being frozen and then brought back to life months or even years later? Well, thanks to the amazing abilities of the turtle leech, scientists may be one step closer to making that possible. From a more practical perspective, studying these slimy creatures may also make it easier to store and distribute human organs, tissues, and cells for transplantation.

A turtle leech. Stereoscopic micrograph of Ozobranchus jantseanus (dorsal view). Click image to enlarge (Suzuki et al./PLOS ONE)

Fast fact: The coldest temperature ever recorded on Earth was -93 degrees Celsius in Antarctica.With a maximum length of 15 millimetres, turtle leeches might seem insignificant. These small blood-sucking parasites spend their entire life cycle hooked onto Chinese and Japanese pond turtles. Luckily, researchers at Kyoto University took the time to isolate a couple of hundred turtle leeches and discovered a natural ability unlike any other.

Some species of turtle leech can be frozen in temperatures as low as -196 degrees Celsius and then successfully revived! The leeches in the study could even survive being frozen for up to 32 months at -90 degrees Celsius. Although the leeches could continue to swim around after freezing and thawing, the long-term effects on reproduction and feeding were not investigated.

Still, just imagine what could be learned by studying these turtle leeches. If researchers can figure out exactly how they manage to survive extremely cold temperatures, not to mention repeated cycles of freezing and thawing, it might become possible to freeze people, just like in the movies. Better yet, it might become possible to improve the cryopreservation of organs, tissues, blood, and stem cells, allowing them to be stored for later use.

A Chinese turtle. Click image to enlarge (Σ64)

Unfortunately, freezing tissues can cause irreversible damage, rendering them unusable for transplantation. The main problem with cryopreservation is the abundance of water in cells, organs, and tissues. When temperatures drop below freezing, water begins to form ice crystals that can pierce cells and tissues. This damages the structure of the cells and causes them to rupture, like a water balloon that freezes.

Fast fact: Ninety-five per cent of your blood plasma is composed of water.Current techniques for storing tissues and blood use slow freezing rates to help remove water through dehydration. They also rely on additives such as glycerol and dimethyl sulfoxide to serve as a sort of antifreeze and stop the formation of ice crystals. These techniques work, but they are not perfect.

The turtle leeches—with their unique ability to be rapidly frozen, stored for long periods without additives, and thawed without damage—might hold the keys to improving cryopreservation. There is something new and entirely different about their biology that scientists have yet to understand, but which might someday help improve tissue and cell transplantation. Sometimes the greatest discoveries can come from the strangest and smallest of creatures.

References

Maathuis MHJ, et al. 2007. Perspectives in Organ Preservation. Transplantation. 83:1289–1298. Sales AD, et al. 2013. Structure, function, and localization of aquaporins: their possible implications on gamete cryopreservation. Genetics and Molecular Research. 12(4):6718-6732. Suzuki D et al. 2014. A Leech Capable of Surviving Exposure to Extremely Low Temperatures. PLoS ONE 9(1):e86807.

Yuriy Baglaenko

I am a 4th year PhD student studying autoimmunity and lupus at the University of Toronto. I am an avid musician with an at-home amateur recording studio and a mediocre intramural volleyball player. To me, biology is an intricate and complex science puzzle which I long to unravel, one strand at a time. 


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