Breakthrough Finding on Hibernation

For the first time, scientists have induced a state of reversible metabolic hibernation in mice, an achievement they say may lead to new ways to treat cancer and prevent injury or death from insufficient blood supply to organs and tissues.

In this first demonstration of "hibernation on demand,” the scientists were able to induce a state of clinical torpor in mice for up to six hours before restoring metabolic function and activity. They did this by placing the mice in a chamber filled with normal room air laced with 80 parts per million of hydrogen sulfide, a chemical normally produced in humans and animals that is believed to help regulate body temperature and metabolic activity. Within minutes, the mice stopped moving and appeared to lose consciousness and their respiration dropped from the normal 120 breaths per minute to fewer than 10 breaths per minute, while their core temperature dropped from 37oC to as low as 11oC.

During a hibernation-like state, cellular activity slows to a near standstill, which dramatically reduces an organism's need for oxygen. If this kind of temporary metabolic inactivity could be replicated in humans, it might help buy time for critically ill patients on organ-transplant lists and in operating rooms and emergency departments.

"Manipulating this metabolic mechanism for clinical benefit potentially could revolutionize treatment for a host of human ills related to ischemia or damage to living tissue from lack of oxygen,” explained lead investigator Mark Roth, Ph.D., of Fred Hutchinson Cancer Research Center (Seattle, WA, USA), whose findings were published in the April 22, 2005, issue of Science.

Dozens of documented cases exist of people surviving prolonged hibernation-like states with no lingering physical or neurologic damage. Even people with no heartbeat and no respiration and with a drastic drop in body temperature for over an hour have later been resuscitated and have made good recovery.

Dr. Roth hypothesizes that temporarily eliminating oxygen dependence in health cells could make them a less-vulnerable target for radiation and chemotherapy and thereby spare normal tissue during high-dose cancer therapy. "Right now in most forms of cancer treatment, we're killing off the normal cells long before we're killing off the tumor cells. By inducing metabolic hibernation in healthy tissue, we'd at least level the playing field.”

In addition to mice, Dr. Roth and his colleagues have also demonstrated the ability to metabolically arrest and then re-animate such organisms as yeast, worms, and the embryos of fruit flies and zebrafish.