“I don’t even know what’s in the soup,” was the shocking quote from the founder of a chain of clinics highlighted in a recent Associated Press article about the increasing prevalence of clinics offering unproven stem cell therapies. The “soup” referred to the mixture of cells and fluid he extracted from a patient’s fat for re-injection into the same patient’s knees, one of many “stem cell” procedures being tried for more than 20 diseases and conditions.

Clinics that offer such “soup” and other so-called “stem cell treatments” that have not been rigorously tested have been the focus of considerable attention lately. In recent months, two highly-publicized scientific reports document the rapid, world-wide, growth of such clinics. In the U.S., the Food and Drug Administration (FDA) released draft guidance documents to clarify regulatory expectations, including that cells harvested from fat and introduced into a different part of the body are subject to FDA oversight, and held a public hearing in September to hear comments on the proposed guidance.

The FDA hearing was a chance for the ISSCR and others to reiterate the importance of regulating stem cell treatments, including those using one’s own cells. The reasons why unproven treatments are still available for sale is nuanced. However, the widespread scientific concerns that these unproven treatments continue to proliferate in the absence of rigorous scientific support are not.

A fundamental concern is the lack of characterization of these treatments. This begins with the use of the term “stem cells.” Cells should only be defined as stem cells if rigorous criteria are met: a demonstrated capacity to self-renew (to give rise to more stem cells) and to give rise to specialized cell types such as blood cells or muscle cells.

This issue is particularly concerning as it relates to the use of the term “mesenchymal stem cells” (MSCs) to describe the desired cells extracted from a patient’s fat. Not only is there considerable skepticism in the field about whether these MSCs manifest so-called “stemness” but there is no way to know how many MSCs are even in the “soup” extracted from fat.

The identification of MSCs requires the cells to be grown in a laboratory for days under special conditions or the use of specific MSC markers to identify and isolate them, although the reliability of these markers is still being debated. What this means for the patient is that the same-day treatments with the “soup” are likely to be a mixture of fat and other specialized cell types with no reliable information on whether MSCs are present and if so, how many are present.

Additionally, stem cells from different tissues have different functions and there is still debate about whether MSCs from all tissue sources (fat versus bone marrow, for example) have the same properties. Furthermore, research on other adult stem cells has shown that stem cells can decline in frequency and function as they age. How these and other biological factors might influence the effects of MSCs is unknown.

The lack of rigorous evaluation of the “soup” and similar “treatments” raises many questions that can only be addressed by rigorous scientific study and clinical trials. Authentic patient testimonials can highlight individual results, but they fail to capture all patients’ experiences, and thus fail to give a complete assessment of the therapy. This commercial marketing strategy is reminiscent of the infomercials where an enthusiastic user excitedly promotes the product’s benefits while the small print at the bottom of the screen reads, “results may not be typical.”

The increase of purported stem cell treatments with little to no evidence of clinical utility, and in some cases a disregard of the known cell- or tissue- biology, has led many scientific organizations to take action.  The ISSCR has released updated professional guidelines for its members and the stem cell community that contain explicit condemnation of “…unproven stem cell-based interventions outside of the context of clinical research…”  Other organizations, such as the American Thoracic Society, the Australasian College of Sports Physicians, among other groups, have released cautionary statements that speak to specific unproven treatments within their specialty areas.

The ISSCR has also developed an informational website, a CloserLookatStemCells.org, designed to help people understand the basics of stem cell science and more. It provides facts about the research and probative questions to consider when evaluating potential clinical trials or stem cell interventions.

Stem cells offer the potential to treat many intractable disease and injuries but there is still a lot to learn about their therapeutic potential. The clear path forward for this relies upon rigorous testing of the safety and effectiveness of the potential treatment in clinical trials and the sharing of experimental and clinical data to ensure that clinical applications are evidence-based.