At UC Davis, Whiskey was in the care of a team of vets who had been perfecting a new procedure to regrow damaged jawbone, work that drew on Urist’s research and other experimental and clinical treatments developed for humans. The team included Dr. Dan Huey, a biomedical engineer; Dr. Boaz Arzi, a veterinary surgeon; and Dr. Frank Verstraete, who heads the dentistry and oral surgery service at the veterinary teaching hospital. Their goal was to put biomedical approaches to bone replacement to use in veterinary practice. Once they had refined a technique that would work for dogs, they put out the word, and soon referrals from other vets were coming their way.
“It wasn’t an experimental study, just an innovative application of existing materials,” Verstraete says.
Over a two-year span, eight dogs have undergone the procedure, and to date, all are doing well, the vets say. Each dog spent three days at the teaching hospital for an exam, surgery and recovery, followed by three post-operative exams.
Whiskey, their sixth patient, had the largest lesion. There was no getting around it: he would lose much of his jaw. But with the help of a titanium plate, a sponge and some bone proteins donated by Pfizer, he would grow a new one in a matter of months.
The team’s first task was to decide how much bone to take in order to remove all of the cancer. That proved to be 2.5 inches, or about half of Whiskey’s lower left jawbone. Once the diseased bone was out, in went a titanium plate built by Dr. Arzi, which was screwed into place on the remaining bone.
But the titanium plate alone was not enough to hold the jaw together. The greatest risk was failure of the plate due to the large gap where the bone had been, Dr. Verstraete says. Over time, pressure on the plate would cause the surrounding bone to resorb.
Enter the scaffold: a stiff, sponge-like piece of material that was fitted into the space. It, too, was only part of the solution. The next step in building a new jaw would require Whiskey’s own stem cells, attracted to the bone proteins in which the scaffold had been soaked. Like a magnet, the bone proteins would draw stem cells from the dog’s surrounding bone and soft tissue to the scaffold, where they would attach and turn into bone cells, according to Dr. Huey. The new bone cells would eventually fill the entire void and integrate with native bone. On a molecular level, the new bone is the dog’s own, with a DNA makeup identical to other bones in his body.
There is no need to match the proteins to a particular dog, Verstraete says. “The BMP we use is synthetic, recombinant human (rhBMP-2). It doesn’t elicit any antibody response in experimental animals.”
Just as the vets borrowed from human medicine, their procedure for dogs will now find its way back into human medicine. Their success with the eight cases has given them material for a report on the work, which they plan to submit to a scientific journal.
What lies ahead for the promising surgery? The vets hope to be able to modify the technique for use with larger jawbone defects in animals. Also on the horizon: human arm and leg bones. There is more work to be done, however. “The technique that we used has not been done for weight-bearing bones yet,” Verstraete says.
Is the new method a cancer cure, or a quality-of-life issue?
“Both,” Verstraete says. “We only do the surgery for tumors that haven’t spread. Reconstruction greatly improves the quality of life compared to the previously used technique.”
Swierk knows there’s no guarantee that Whiskey will remain cancer-free. “The assumption is that it’s a cure, but the verdict is still out.” But based on Whiskey’s September checkup, it’s “so far, so good.”