(AP) -- The experimental stem cell procedure that Texas Gov. Rick Perry underwent this summer could be restricted or even blocked under new rules being considered Friday by the state's Medical Board.

Some top scientists are questioning the safety and wisdom of the procedure, and doctors say it may run up against federal rules. It also carries potential , ranging from blood clots to increased .

The Republican presidential candidate had stem cells taken from fat in his own body, which were then grown in a lab. They were injected into his back and his bloodstream during an operation in July to fuse part of his spine.

have long been used to treat leukemia, lymphoma and other cancers. While the cells are being studied to treat other ailments, from heart disease to diabetes, experts say it's too soon to know if the approaches are safe or effective. The hasn't approved using adult stem cells to help people heal from surgery - but experimentation is common.

Perry opposes greater oversight in Texas, and he sent a letter to the board urging members to recognize the "revolutionary potential" of adult and therapies.

"Texas is a leader in innovation in many fields," Perry wrote after his surgery. "It is critical that we continue to foster an environment that encourages technological advancement in the health care arena."

Adult is different from using , a controversial technology that Perry opposes.

The medical board will meet Friday to discuss rules that would require an accredited body to review any procedures involving stem cells before they're carried out, to access research trials and ensure patient safety. The rules also would require that such therapies be done by physicians and in adherence to Texas and federal laws.

The 19 volunteer board members - all appointed by Perry, including a dozen physicians - could approve the proposed rules, make or seek changes, or scrap them altogether, board spokeswoman Leigh Hopper said.

If the board vote goes against him, the matter could become a campaign issue as Perry struggles to reinvigorate his White House bid. His polling numbers have tumbled in recent weeks. Perry has worn a back brace but maintained his work schedule since the surgery.

Some orthopedic surgeons are experimenting with stem cells to help bones heal, with the cells being taken from bone marrow and injected or implanted in the trouble spot. The theory is that such "master cells" will follow cues from cells around them and form bone or cartilage, though researchers worry they also might spur unwanted growth and cancer.

Perry's treatment, which involved using from fat, was even more experimental.

Perry said in his letter that he understood the need to protect patients, but added, "we need to ensure that physicians in this state can continue to pursue new technologies and treatments that will benefit all Texans."