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How Live Frozen Frogs Can Help Preserve Human Organs

Ann Thompson
These frogs inside an incubator at Mt. St. Joseph University are in a kind of frozen state. Cryoprotectants are key and researchers are trying to translate the concept into human organs.

Under a leafy litter, native wood and tree frogs are sleeping in a kind of frozen hibernation. Researchers hope chemicals in their blood that permit this suspended state can translate into a longer shelf life for transplantable human organs.


A local scientist has been studying wood and tree frogs for more than a decade to see what makes them resistant to cold weather. Mt. St. Joseph University Biology Professor Clara do Amaral and colleagues at the University of Dayton and Wright State University discovered the frogs accumulate chemicals in their blood called cryoprotectants.

"These chemicals kind of work like an antifreeze so they help to protect the frog from the ice that forms on the animal," she explains. "So ice still forms but it's less damaging because of these cryoprotectants."

Cryoprotectants are also used in sperm and egg preservation.

Here's what protects the frogs:

  • Glucose-blood sugar
  • Urea-waste product
  • Glycerol-sugar alcohol

At the beginning of February, when the weather warmed and the frogs woke up, do Amaral was able to collect a few and bring them back to her lab. She gently lowered their body temperature and the frogs went back to sleep in the university's incubator.
"These animals are freeze-tolerant but you can't put them in liquid nitrogen or dry ice. That's way too cold, she says. "They can survive up to -5 °C, (about 23° Fahrenheit). However, the soil temperature is warmer, so even if the outside temperature dips below 23 degrees the frogs will survive." Alaskan frogs can withstand even lower temperatures.

Do Amaral is also looking at the frog's DNA to understand how it responds to low temperatures by turning genes on and off.

Credit Ann Thompson / WVXU
Dr. Clara do Amaral checks a circulating bath that gently lowers the body temperature of frogs whose bodies can freeze without any internal damage.

Adapting these antifreeze-like cryoprotectants to humans could mean a longer shelf life for organs. Human organs outside the body don't last very long - for a heart, it's six hours max; for a liver and pancreas, it's 12.

Do Amaral will stick to studying frogs, but other researchers are working to extend the life of human organs using information they have learned from scientists like do Amaral. A variety of methods are being used to study the preservation of organs, including a glass-like substance. Futurism.com reports a California company is using helium to preserve organs and says it will be ready for human trials next year.

With more than 30 years of journalism experience in the Greater Cincinnati market, Ann Thompson brings a wealth of knowledge and expertise to her reporting. She has reported for WKRC, WCKY, WHIO-TV, Metro Networks and CBS/ABC Radio. Her work has been recognized by the Associated Press and the Society of Professional Journalists. In 2019 and 2011 A-P named her “Best Reporter” for large market radio in Ohio. She has won awards from the Association of Women in Communications and the Alliance for Women in Media. Ann reports regularly on science and technology in Focus on Technology.