Wood frog freeze tolerance drives organ preservation research

August 29, 2026 at 09:15 PM2 min

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Researchers are studying the wood frog's ability to survive freezing to extend organ storage times for transplantation. The frog can survive with up to 70 percent of its body water frozen, and scientists have used a modified sugar to supercool human livers below zero. This approach kept a human liver viable for 27 hours, far beyond the current limit of about 12 hours.

Key Facts

Wood frogs can survive freezing of 65 to 70 percent of their total body water, with no heartbeat, breathing, or nerve activity.
Wood frogs from interior Alaska survive freezing at -16°C, 10 to 13 degrees colder than Ohio populations.
In the United States, more than 100,000 people are on the organ transplant waiting list, and about 13 die each day before an organ becomes available.
Researchers used 3-O-methyl-D-glucose and supercooling to keep a human liver viable for 27 hours, more than double the current storage limit.

Frog Freeze Survival

A wood frog in a Canadian January has no heartbeat, no breathing, and no measurable nerve activity, with close to two thirds of its body water frozen in extracellular spaces. Freezing begins on the skin and triggers the liver to flood the body with glucose, which acts as a natural antifreeze inside cells. Kenneth Storey of Carleton University reports that 65 to 70 percent of total body water turns to ice in extracellular masses, causing organs to visibly shrink. Frogs also stockpile urea, rebuild cell membranes, and raise antioxidant levels before the first hard frost, as documented by Kenneth and Janet Storey in Physiological Reviews. Northern populations push the system harder: wood frogs from interior Alaska survive freezing at -16°C, 10 to 13 degrees colder than their Ohio relatives, due to larger liver glycogen reserves that mobilize faster.

Organ Storage Limits

Standard organ preservation is static cold storage, which gives transplant teams only hours to move an organ from donor to recipient. Korkut Uygun, a chemical and systems engineer at Massachusetts General Hospital, states that packing an organ in ice and racing it to the recipient means counting hours, not days. In the United States, more than 100,000 people are on the transplant waiting list, and about 13 die each day before an organ reaches them. Extending storage from hours to days would transform transplantation from an emergency race into a logistics operation.

Antifreeze Sugar Application

Because glucose at frog concentrations would poison mammalian tissue, researchers used 3-O-methyl-D-glucose, a modified sugar that cells take up but cannot metabolize. Combined with supercooling, which chills tissue below zero without freezing, the approach produced a clinical-scale result in 2019. The method kept a human liver viable for 27 hours, more than double the current limit of about 12 hours.