War is hell on the bones of warriors. And when the long bones of the arms or legs are so badly broken that they can’t heal on their own, amputation is sometimes the only option.

But University of Georgia researchers and colleagues from other universities have developed a jelly-like substance that may help catastrophic breaks knit together. Stem cells are the key ingredient in what the scientists call “bone putty.”

Catastrophic arm or leg injuries are the No. 1 reason why U.S. troops have extended hospital stays, says Steven Stice, director of the Regenerative Bioscience Center at UGA.  And it’s all too common for a service member with a so-called “non-union” break to lose the limb.

In 2008, the Defense Advanced Research Projects Agency issued a call to duty for scientists: come up with a bone-healing substance for service members.

Responding to the call were Stice and John Peroni, associate professor of large animal surgery at the UGA College of Veterinary Medicine, in partnership with Baylor College of Medicine and the University of Kansas School of Medicine.

The UGA scientists and their collaborators have since created fracture putty, hoping that it could potentially save an injured limb, or at least allow less of it to be amputated.

They engineered stem cells using the gene for a special bone-growing protein called BMP2, bone morphogenetic protein 2.

Recovery from severely broken bones is notoriously slow, and the patient has to avoid using the injured leg or arm for weeks or even months. But there is early evidence that the fracture putty could reduce healing time by a third or even half, says Stice.

A recipe for healing

The fracture putty has three essential ingredients, and each does something different.

The stem cells calm inflammation and attract the body’s own stem cells to the site of the break.  The BMP2 gene accelerates protein production to make more bone faster.  These are incorporated into hydrogel, a jelly-like substance that glues everything together so surgeons can apply the mix to broken bones.

The Stice and Peroni teams are currently testing the putty on sheep.  Bones are healing faster in these experiments, but much work remains before the product can be tested in people. For one thing, a different carrier might replace hydrogel in future experiments. Other changes are possible as well.

“As a product, fracture putty must go through safety and efficacy trials before being approved as a therapeutic for use in humans,” said Robin Webb, a postdoctoral fellow in the Stice lab.

Looking ahead, if the Food and Drug Administration approves fracture putty for humans, it could be a boon to elderly people as well as to much younger military personnel.

As people age, their production of BMP2 decreases, drastically reducing bone-healing capacity.  Breaking one of the long bones in the thigh or leg is often a devastating injury for older folks, whose overall condition deteriorates when they can’t walk.  Fracture putty could potentially speed healing and get them back in the game.

Stice explains that the product may also be used in spinal fusion procedures for people with back problems, and in periodontal surgeries such as dental implants.

Pre-clinical tests are encouraging, Stice says. “The most rewarding thing so far is showing that we can get something to work that is faster, better, and could help a lot of different people in the future.  We’re excited about the potential of who could benefit from this.”

What’s next?

All technology related to the fracture putty is under the UGA research umbrella.  Scistem, a company co-founded by Stice, has licensed the patent application for the putty to be approved.  If that is granted, UGA will be able to block competitors from formulating an identical compound, and there are similar products in the research pipeline elsewhere.

For an experimental medical treatment, the journey from lab to hospital is a long one. “[A] typical therapeutic drug today takes 15 to 20 years to go through that whole process, from the time that a promising drug is discovered to the point where it’s cleared for clinical trials,” says Stice.

But he’s not discouraged.

“You know, we’re in science, and we always have great hope that things will work out.”

Ansley Stewart is pursuing her master’s degree in journalism at the University of Georgia.  She is a freelance writer, musician, and also works full time at UGA.