Hibernation Provides Organ Transplant Clues.

• Position: SQUIRRELS

Researchers at the National Eye Institute have discovered cellular mechanisms that help the thirteen-lined ground squirrel survive hibernation. Their findings could be a step to extending storage of human donor tissues awaiting transplantation and protecting traumatic brain injury patients who undergo induced hypothermia.

During hibernation, the thirteen-lined ground squirrel endures near-freezing temperatures, dramatically slowing its heart rate and respiration. How its tissues adapt to the cold and metabolic stress has confounded researchers. A structure in cells known to be vulnerable to cold is the microtubule cytoskeleton. This network of small tubes within a cell provides structural support and acts as a kind of inner cellular railway system, transporting organelles and molecular complexes vital for a cell's survival.

In a series of experiments, the research team--led by Wei Li (senior investigator in the NEI Retinal Neurophysiology Section) and Jingxing Ou (postdoctoral scientist in Li's lab)--compared cells from nonhibernators to cells from the ground squirrel to determine differences in their response to cold. They found that, in ground squirrel neurons, the microtubule cytoskeleton remains intact while it deteriorates in the neurons of humans and other nonhibernating animals, including rats.

To investigate the biological factors supporting the squirrel's cold adaptation, researchers created "hibernation in a dish." They took cells from a newborn ground squirrel and reprogrammed them to...