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Using them as was done for Perry is “quite experimental and it’s quite controversial because there isn’t good evidence yet, at least in the medical literature, that fat cells work better or even work at all in repairing bones,” Muschler said. “It’s out there, a little past the edge of what mainstream medicine would generally accept.”

The Cleveland Clinic has three patents on cell-related technologies Muschler developed, and he has consulted for Medtronic Inc. and the federal Food and Drug Administration.

Dr. Thomas Einhorn, orthopedics chairman at Boston University, has tested some experimental stem cell therapies himself. He said one concern is that Perry’s cells were grown in a lab dish with other ingredients where there is more of a risk they will transform into cancer and any breach in sterility could lead to an infection once they were put into a vein.

He also took issue with infusing the cells into Perry’s bloodstream. “I can’t think of any reason to do that. I wouldn’t want to cause a blood clot.”

It also enters a gray area with the FDA, which does not regulate how doctors practice medicine but does oversee medical products. Growing the cells in culture and possibly mixing them with other substances may make these modified cells a product. The FDA got an injunction barring a Colorado company from growing marrow-derived stem cells in this way; lawsuits over that are pending.

FDA spokeswoman Shelly Burgess said that the agency could not comment on Perry’s treatment and that each case must be evaluated individually.

Besides safety concerns, little is known about whether such cell therapies work.

Patients may believe cells helped them, but there’s no way to know they did unless a study is done comparing those who did and did not receive such treatment, said Dr. Scott Rodeo, an orthopedic surgeon at the Hospital for Special Surgery in New York. He was a physician to the USA Olympics Teams in 2004 and 2008 and is associate team physician for the New York Giants football team.

Perry still wears a back brace sometimes now on the campaign trail, but he wasn’t available for an interview Thursday. On July 12, less than two weeks after his surgery, he told an AP reporter: “Every day has been better. Not quite ready to go run a marathon in July but I feel great, wear a little brace and good to go. Everything is awesome.”


Associated Press writers April Castro in Austin, Texas, and Steve Peoples in Dover, N.H., contributed to this report.


Marilynn Marchione can be followed at