Chicago ? Meet Zoey Walsh, a teenage stem-cell recipient who is pushing the frontier of medical science.

He’s a dog.

Unable to alleviate his pain with drugs and unwilling to risk another hip surgery on a dog so old, Zoey’s owners turned to a treatment that involved injecting stem cells, which had been extracted from Zoey’s fat, back into the animal. The stem cells stimulate repairs.

The therapy is gaining momentum as a treatment option for pets. But it also holds promise for humans, researchers and companies involved say.

“It did wonders,” Zoey’s owner, Raymond Walsh of Palos Heights, Ill., said of his 14-year-old American Eskimo’s first injection six months ago. “He is having another round. But had we not given the first shot back in August, we might have had to put him under.”

Such treatments aren’t cheap. An injection and anesthesia to sedate a dog before and after stem-cell extraction and injection can cost between $2,500 and $3,500. A follow-up treatment usually costs less than half that because stem cells from the original extraction often are left over.