Why hibernation could save stroke victims
Hopes also high for treating cancer, heart attacks
A male brown bear wakes up after winter hibernation at Ranua Zoo in Ranua, Finland, in Lapland. After a short stroll he decided to continue a nap in a soft snow bank. Scientists have spent decades studying hibernating animals and their ability to slow their pulses and drop their body temperatures to the point of near-death for months on end – without damaging their brains and vital organs.
SCIENTISTS are racing to make human hibernation a reality – not to escape winter, but, for example, to help provide precious time for cancer treatment to work. And that’s not all.
As Mervyn Singer, a professor of intensive care and medicine at University College London Hospital, reveals, his team is trialling a drug that may soon be used to make vital human tissues such as hearts, brains and arteries go into a hibernatory sleep mode.
This could potentially save the lives of thousands of heart attack and stroke patients every year.
Singer believes it could protect these cells against lethal trauma that can occur during emergency resuscitation procedures. The trauma – called reperfusion injury – occurs when blood flow is suddenly restored to tissue that has had its supply blocked, such as heart and artery cells in heart attack and brain cells in stroke.
It seems common sense to restart heart attack and stroke patients’ circulations as soon as possible – for example, by inserting a wire-mesh tube (stent) to prop open blocked arteries.
But the shock of a sudden return of blood and oxygen can spark an inflammatory reaction that destroys vital artery, heart and brain tissues in up to a third of patients, and can prove lethal.
If Singer’s first human trial, scheduled for next year, shows the drug can protect patients from re-perfusion injury, it would provide the first workable hibernation treatment breakthrough in 20 years of global efforts.
Scientists have spent decades studying hibernating animals and their ability to slow their pulses and drop their body temperatures to the point of near-death for months on end – without damaging their brains and vital organs.
The hope is that such biological feats can be copied and used to create drug therapies for diseases including diabetes, Alzheimer’s and cancer.
Last month, researchers revealed that their studies show a biological trick performed by hibernating squirrels could prove key to developing a drug to protect stroke patients from brain damage.
Scientists from the US National Institute of Neurological Disorders and Stroke say that when squirrels hibernate, a protective process occurs in their cells that allows their brains to survive the reduced blood flow cutting vital supplies of oxygen and glucose.
“If we could turn on the process hibernators use, we could help protect the brain during a stroke,” says Joshua Bernstock, the neuroscientist who led the study.
Meanwhile, Italian scientists are exploring the possibility of putting cancer patients into a hibernation state in which their whole bodies could be cooled from a norm of 37°C to a deathly chilled 13°C.
Professor Marco Durante, a physicist at the Trento Institute for Fundamental Physics Applications, hopes this will bring bodily functions to a virtual standstill and give doctors more time to try to kill off tumours with radiation.
It is not yet technically possible to hibernate a human body in a way that could safeguard brains and vital organs from severe damage, but Durante believes this will be achieved within the next decade.
In February, at a conference for the American Association for the Advancement of Science, he said: “I’m confident we will be able to develop drugs that can induce this torpor safely.”
Hibernating animals have developed the ability to let their brains’ internal communications links – their synaptic networks – fall apart during their winter sleep.
But as the animals wake, the networks restore to full function.
These are massive challenges – but they could have huge benefits. In patients with Alzheimer’s disease, the brain’s synaptic connections fall apart, causing confusion and memory loss.
If investigators could learn the hibernators’ trick of rebuilding those connections, there is a possibility therapeutic hibernation could be used for preventing or treating Alzheimer’s disease.
Meanwhile, Singer is forging ahead with a world-first hibernatory drug trial for heart attack and stroke patients – by putting a targeted part of their body or brain into hibernation.
“If you have a heart attack, some of the tissue dies, but the surrounding cells shut down to protect themselves from the loss of blood supply,” he explains.
“This ‘myocardial hibernation’ has been known about for 20 years. A similar process happens in the kidneys after kidney failure, and in the brain after a stroke.
“The cells shut down in the hope the physical problem will repair itself, the organ’s function will return and the hibernating cells can re-awaken and recover.” – Daily Mail