Patients seeking stem cell therapies for achy joints or shoulder injuries no longer need to hop a plane to Mexico or China. More than 550 clinics around the U.S. offer unproved interventions for sports injuries and conditions including autism, multiple sclerosis and Alzheimer’s disease. In cities like Beverly Hills or New York a prospective patient may only need to drive some 20 or 30 minutes from the center of town to find such a treatment.

This vast stem cell market has boomed in recent years, particularly for orthopedic applications such as easing joint pain or for facelifts and other cosmetic procedures. In one frequently advertised regimen a patient might have adult stem cells harvested from his own fat tissue and injected at an injury site, purportedly to speed recovery. Professional athletes including football stars Peyton Manning and Chris Johnson have reportedly used stem cell injections to help them get back onto the field.

Yet there is a darker side to the promise of these treatments. There is little systematic data about patients’ long-term outcomes—positive or negative—and in most cases there is no scientific evidence that these costly procedures work. Many of these cellular therapies may not do much of anything but there is also the serious risk that recipients of cell injections could develop serious complications “including blood clots or dangerous immune reactions,” says Paul Knoepfler, a stem cell researcher at the University of California, Davis, School of Medicine and co-author of a new analysis, published Thursday in Cell Stem Cell.*

One U.S. patient traveled to China, Mexico and Argentina for stem cell therapies following a stroke and went on to develop a huge mass in his lower spine—replete with someone else’s cells, according to a recent account in The New England Journal of Medicine. Without clear evidence that these procedures are safe, effective and actually tap the type of cells they claim to use, they should be avoided, Knoepfler says. (Bone marrow stem cell therapies used for cancer and blood disorder treatments, however, are widely accepted medical procedures.)

Armed with new data about the proliferation of stem cell clinics, Knoepfler and co-author, University of Minnesota bioethicist Leigh Turner, are seeking to correct the widespread belief that such procedures only happen overseas: Patients wishing to engage in “stem cell tourism” need only drive minutes from metropolitan areas across the U.S., not to a foreign country, they note.

Click to enlarge. Source: "Selling Stem Cells in the USA: Accessing the Direct-to-Consumer Industry," by Leigh Turner and Paul Knoepfler in Cell Stem Cell, Vol. 19; August 4, 2016

Such clinics have often sidestepped heavy regulatory scrutiny, claiming they are eligible for a U.S. Food and Drug Administration exemption that applies to minimally manipulated cells. Some claim to extract a patient’s cells found in fat, bones or other tissues and inject them back into the same patient at a different site—such as a joint or a saggy chin—within the same operation, all without substantially altering the cells. But many of these clinics also offer myriad types of stem cell treatment that would suggest they “are not compliant with federal regulations,” the authors wrote.

Amid this stem cell therapy explosion, the FDA recently issued draft guidance that would clarify and tighten its regulation of this area. “The FDA is concerned that the hope patients have for treatments not yet proven to be safe and effective may leave them vulnerable to unscrupulous providers of stem cell treatments that are illegal and potentially harmful,” FDA spokesperson Andrea Fischer said in a statement. If the proposed guidelines are enacted, the FDA would likely bring more of these clinics under its purview and regulate offerings in the same way as biological drugs. Public interest in this contentious area is undeniable: The FDA is holding a delayed public hearing on stem cell regulation this fall, after it was overwhelmed by audience sign-ups for its scheduled hearing in April.

“This all should still be in the research phase without question,” says Peter Rubin, a stem cell researcher who chairs the Department of Plastic Surgery at the University of Pittsburgh Medical Center and runs a clinical trial to test the use of stem cells to repair severe facial wounds and limb injuries in soldiers. “We need to establish credible data around these therapies before bringing them to patients,” he adds. Rubin, who was not involved in Knoepfler and Turner’s latest research, plans to testify at the hearing this fall.

Currently, hundreds of U.S. clinics—61 percent of the businesses in the new analysis—market therapies that use fat stem cells. Although details vary between clinics, that often means the clinic gives a patient liposuction then chemically separates stem cells from the fat and centrifuges them before injecting them into an injury site to purportedly help a patient heal faster or to alleviate pain. “Fat is a structural tissue, and if you break down its biological properties so it can no longer provide padding or cushioning, then it has been manipulated,” Rubin says. Such procedures, he says, would likely require FDA regulation under the new proposed guidelines.

To get a new count showing exactly how widespread stem cell clinics have become, Knoepfler and Turner scoured the internet for Web sites marketing stem cell interventions. They found 351 U.S. businesses engaged in direct-to-consumer marketing of such services offered at 570 clinics. Most of the clinics were concentrated in California, Florida, Texas, Colorado, Arizona and New York, but most states had at least one. There were also certain “hot spot cities” with a dozen or more clinics such as Beverly Hills, New York, San Antonio and Los Angeles. The authors could not verify that the clinics truly offer what is advertised on their Web sites, the sources of their stem cells or their interactions with the FDA.

Yet what they did find, Knoepfler says, was “very concerning”—particularly because some of the ads targeted conditions that affect particularly vulnerable populations, including children. Nine clinics promoted stem cell treatments for autism and cerebral palsy and another 33 advertised therapies for muscular dystrophy, a disease that primarily afflicts kids. Alzheimer’s disease treatments were offered by 27 clinics. “These are the conditions that most concern me because there is the most striking gap between the marketing claims being made and the actual evidence that is available,” Turner says. “In effect [the patients] are participants in unapproved human-subjects research without even realizing it.”

*Editor's Note (7/11/16): This sentence was edited after posting to clarify information about the authorship of the study.