Squirrels may improve organ donation

Professor talks about why squirrels are important for artificial hibernation study

by Kate Briquelet, of the Advance Titan

December 7, 2006

In 2002, Vaughan started the nation's only captive breeding colony of ground squirrels to study hibernation. Artificial hibernation is now being considered for medical treatments such as organ donation.

Q: Why did your squirrel study begin?

A: I first heard about ground squirrels in the 1980s during my PhD program studying the retina of the eye with the intention of improving prevention of, and treatment for, blinding diseases that affect rod and cone photoreceptors... There are some really prevalent diseases, such as macular degeneration, that kill off foveal cones. So you'd think vision research has focused on cones, but in fact it hasn't. That's because most diseases are modeled in rats or mice, which have only 1 percent cones; we just can't learn about cones from them. In contrast, ground squirrel retinas have 85 percent cones, so they are a much better model for cone-based diseases... I knew about them, but I didn't work on them because hardly anyone did at that time.

Shortly after I moved to UW Oshkosh in 1998...I looked up what papers had been published about hibernation and retina. Both (papers I found) suggested that ground squirrel cones degenerated partially during the winter, then regenerated fully in spring. It struck me that, if this degeneration-regeneration cycle was real, it was a remarkable example of self-repair, something medical doctors would like to foster in their patients' retinas, brains, and spinal cords.

Q: Why are squirrels important to your studies?

A: To be funded, biomedical research projects need to relate to the human condition; therefore, mammals are preferred for such studies. However, the projects also have to be feasible. You have to be able to obtain research animals without threatening wild populations and keep them in a lab environment without incurring dollar-wasting expenses or causing them undue stress. Ground squirrels are rat-like, so they are familiar and convenient and relatively inexpensive. If you want to study the medical possibilities of hibernation physiology, there is no better model animal than the ground squirrel because they undergo as deep a hibernation state as any mammal undergoes.

Q: What do you do with the squirrels?

A: We do two things. First, we breed them in captivity, which is unique. Everyone else working on squirrels has to capture them from the wild, which means they never know the degree of genetic relatedness of their animals, or their prior disease or nutritional status or even their ages... wild-caught animals are also frightened of people, so you sometimes end up studying stress on top of what you intended to study.

Second, we euthanize them and collect their tissues at different stages of hibernation and arousal, for multiple types of analysis... We don't just take the eyes, either. Labs at other campuses can use the brain, blood, heart, liver, kidney, and so on, so we collect those, too, and preserve them for later projects that maybe we haven't even thought of yet. I think we owe it to research animals to make their deaths count for as much scientific advancement as is humanly possible.

Q: During hibernation, a squirrel's metabolism slows to almost nothing and its heartbeat slows to fewer than 10 beats per minute. This state would kill many other animals. So, in the future, how would artificial hibernation work with humans?

A: We already know that young children who get lost in the snow or fall into icy water can survive severe hypothermia. That isn't quite hibernation, but (it) comes close. They may suffer frostbite, but their brains and internal organs seem unaffected. So that's evidence that it's possible. More directly, the genetic comparisons that have been done so far show that humans share the same genes that operate in squirrel hibernation. It's a matter of identifying the chemical trigger.

Q: How close are we to using artificial hibernation for medical treatments?

A: We are years away from an application, except maybe in the realm of organ transplantation. In squirrels at least, organs collected during hibernation seem to have a much longer shelf-life outside the donor's body, days instead of hours, and that alone would prevent donor organs from going "bad: due to transport delays. In this application, a brain-dead organ donor would be put into hibernation prior to collection of organs.

The other kinds of treatments people envision include rapid induction of hibernation to stabilize patients with severe heart attacks or brain injuries, including stroke, so that they can be more safely transported. Think of it as extending the "Golden Hour." The military is quite interested in that application because of all the head injuries now. Another intriguing study I read suggested that hibernation might improve the cancer-killing effects of chemotherapy.

Q: Have you guys named the squirrels?

A: In the first year or two, we had names for a few of them: Pooter, Madonna, and Mr. Nasty come to mind. Now we just have too many. One of our litters of 12 babies last year were incredibly friendly; they'd grab the mesh of their cage lids and hang upside down to sniff our fingers. We called them the "Monkey Babies" and we're keeping them for breeding stock because we want to select for the animals that are happiest in captivity.

Q: Anything else you'd like to add?

A: The best place to see these guys in the wild is in sunny areas of cemeteries during the month of May when they are having "breakfast" after the longs months of hibernation. For example, try Riverside Cemetery just north of campus on Algoma Boulevard. Look for them sitting up straight and absolutely still. You can sometimes get within 30 feet or so before they dive into a tunnel.

Copyright © Advance Titan, The Student Newspaper of the University of Wisconsin at Oshkosh

This article posted December 12, 2006.