Hundreds of American businesses offer stem cell treatments unregulated by the U.S. Food and Drug Administration. An ASU study has investigated such operations across the Southwest.

The research appears in the journal Stem Cell Reports.

The website-based review examined 170 stem cell businesses in six Southwestern states, including "hot-spot" cities Phoenix and Scottsdale.

It found most stem cell businesses specialize in certain ailments, such as orthopedic issues, and use adult stem cells from fat (adipose tissue) or bone marrow.

Orthopedic and inflammatory illnesses were the most common treatment targets, followed by pain relief, cosmetic effects and neurodegenerative conditions.

The FDA has begun drafting guidelines and taking legal action. But, as co-author David Brafman of ASU explained, the agency might struggle to strike the right balance.

"These clinics are highly diversified, highly fragmented, and so it's difficult to sort of regulate with one sweeping policy," he said.

For example, the FDA — and the Federal Trade Commission — might want to put a stop to businesses that make false claims, administer unproven treatments or lack trained personnel to oversee therapies.

"Should a clinic that has an orthopedic surgeon as their head, who's offering to do injections into joints, be regulated the same way as a plastic surgeon, who's now claiming that they can treat all manner of diseases that they weren't originally trained in?" Brafman said.

Researchers identified roughly one-third of stem cell businesses that shared an address with another medical or cosmetic clinic. Although most of them had separate websites and contact information, at least two-fifths shared care providers.

According to the paper, 20% of businesses studied were affiliated with one of three franchises: California-based Cell Surgical Network; Regenexx/Regenerative Sciences, now headquartered in Iowa; and Arizona company R3.

In 2014, the agency won a court case against Regenerative Sciences for violating manufacturing and labeling requirements. The FDA is currently seeking a permanent injunction against the Cell Surgical Network.