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Baseball pitching motion. Wikipedia

With the Toronto Blue Jays* off to a terrible start, I was almost dissuaded from reading anything about baseball, until I happened upon the following article: “Stem-cell therapy is poised to disrupt the Tommy John epidemic in baseball.” First, I had to do my standard “fake news” check by triangulating the sources, readings, etc., but after a few minutes, it was clearly apparent that this was a legitimate thing…. Really? Yep.

Perhaps I’ve lived under a rock when it comes to baseball stories related to science, ever since my last foray – a delightful trip through Stephen Jay Gould’s Triumph and Tragedy in Mudville – but this was one that I couldn’t resist poring over. My world’s were colliding: sport and stem cells together at last – well, sort of, at least. The thing is that the more I read about this therapy, the less it became about stem cells.

First some background for non-sports fans. A Tommy John surgery is a very niche thing for people who regularly over-strain their arm (e.g., pitching baseballs at 90-100 mph every game). There is a great description on Wikipedia if you want to learn all the ins and outs, but the important point is that this surgery results in major downtime for some pretty high profile (and expensive!) players. The typical “recovery” time for a Tommy John surgery is about a year, meaning that anything that could potentially reduce this time or avoid it altogether is given serious consideration by professional baseball clubs. Enter “stem cell therapy” and this is where two major issues emerge.

  1. It hasn’t been proven to work and is unlikely to ever have a proper trial

Since this is such a niche injury and the stakes are so high (professional athletes are big $$$), you can virtually guarantee that nobody will ever undertake a sham injection or volunteer to be the untreated control. This presents an interesting conundrum: how can such experimental and specialist treatments actually be evaluated? Has anyone ever done rest and rehab for a full year without the surgery or cell therapy? How does it compare?

At the very least, the clinical information about the progress of these professional athletes should be assessed by an independent third party who can determine the relative performance of all athletes treated in this manner (e.g., how many make full recoveries? Are there any side effects?). There should be a reasonable set of data available for those electing to do a Tommy John surgery – is stem cell therapy truly better than a Tommy John surgery? Observe and let the numbers speak for themselves.

For Tommy John surgeries, some numbers do exist in previously published reports including a fairly rosy one and a somewhat more underwhelming one – both of which suggest that many pitchers return (75-85%), but a sizeable fraction do not last very long or do not return at all. Do any of the cell therapies improve on these numbers?

  1. The unfair optics of calling this a stem cell therapy

For the last two decades, the hype around stem cells has been incredible. Some of it warranted, some of it most certainly not. There has been some positive benefit to all of the marketing (e.g., remember Proposition 71 in California, which resulted in US$3 billion of funding for stem cell research?) and this further encourages promises of the revolutionary medical advances potentiated by stem cells. The scientific premise is real – stem cells are incredibly powerful cells that can make any cell in the body – but the hype is not, and these cells will certainly not cure every disease on the planet.

I am reminded of a 2011 article in the Walrus by Tim Caulfield where he said:

“We want to be wrinkle-free, and we know it’s a lost cause, but the term “stem cells” injects hope. Stem cells, after all, represent cutting-edge science. Who knows—perhaps this will be the cure that works.”

The sad reality is that this provides a spectacular opportunity to hijack the excitement of stem cells in order to sell the promise of cellular therapy success.  And this is exactly what the baseball stem cell therapy is doing: cashing in on the idea of stem cells. Even if something beneficial is occurring in these treatments, one thing is for certain in my mind – these therapies should not be called “stem cell therapies.” There is zero evidence that the stem cells themselves do anything at all in these patients and some of the providers are actually very open about this. Therefore, at the very least, doctors should be prohibited from cashing in on the sexy term “stem cell therapy,” which would lead to more skepticism and less blind hope.

At the end of the day, readers should seek reliable guidance from multiple sources. Two professional organizations of stem cell scientists (EuroStemCell and the International Society for Stem Cell Research) encourage patients to ask probing questions and demand evidence from the providers of any sort of cell therapy and particularly useful is the “Nine Things to Know About Stem Cell Treatments” by the ISSCR.

Professional athletes (and their managers, agents, and teams) should be asking a lot of really tough questions about the therapies being proposed. It is entirely possible that these very expensive therapies are doing absolutely nothing and could even be harming the patient. Demand the evidence that a cell therapy works and have it scrutinized by impartial third parties with expertise in stem cell medicine. Til then, let’s hope the Blue Jays turn around their season without the need for a revolutionary intervention!

*I may live in the UK now, but I still root for my childhood team!

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David Kent

David Kent

Principal Investigator at University of Cambridge
Dr. David Kent is a Principal Investigator at the University of Cambridge in the Cambridge Stem Cell Institute ( His laboratory's research focuses on fate choice in single blood stem cells and how changes in their regulation lead to cancers. David is currently the Stem Cell Institute’s Public Engagement Champion and has a long history of public engagement and outreach including the creation of The Black Hole in 2009. He has been writing for Signals since 2010.