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September 17, 2010

What's in a label?

By Katie Moisse

Replacing dead or dying cells with new, healthy ones is the holy grail of regenerative medicine. Even sustaining damaged cells with toxin-mopping, growth-factor-spewing stem-cell-derived support cells would be a tremendous feat.  

But while clinical trials have hinted at stem cell therapy's tremendous potential to replace parts or at least aid in necessary maintenance, the details of how these cells work their therapeutic magic often fall through the methodological cracks.  

It's all very well to conclude that injecting stem cells into damaged organs does some good. But in order to understand whether these cells are homing to injury sites and setting up shop, or even surviving at all, they have to be traceable. 

Let’s look at the heart. A study assessing the acute and long-term effects of intracoronary stem cell transplantation in patients with chronic heart failure (the STAR-heart study), published in the July issue of the European Journal of Heart Failure but re-reported August 29 at the European Society of Cardiology annual meeting in Stockholm, Sweden, suggests the therapy improves ventricular performance, quality of life and survival. 

But the mechanism by which 6.6 x 107 bone marrow cells confer protection when injected into damaged hearts is not explained in the report. The researchers posit that the transplant “may overcome the possibly detrimental effects of ventricular remodeling,” but later add that “further studies are required which focus on cell based therapy.” 

Not knowing where these cells are going or what type of role they’re taking on not only makes it difficult to optimize the therapy, it also represents a missed opportunity to learn something about the diseases or conditions themselves.

Incorporating reporter genes, magnetic or radioactive labels could allow researchers to follow transplanted cells to their final destination using non-invasive imaging techniques like PET and MRI, offering clues to their newfound function. There are obvious obstacles to consider before applying such approaches widely in humans though, such as immunogenicity of integrated gene products, the possibility that patients might depend on medical devices (such as pacemakers) that preclude them from having MRIs, and radiation exposure.

However, until these marvelous but mysterious cells can be tracked -- even just identified in post-mortem tissue -- we simply won’t know for sure what they’re doing. This creates problems in the era of stem cell “clinics” selling phony medical miracles based on cell therapies. Clinical trials that show stem cells work but offer no explanation as to how continue to leave open the door for such abuse. 



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I agree that labeling transplanted cells is ideal and ultimately necessary, however I did not mean to suggest that trials designed to establish safety, tolerability and efficacy aren't useful. As a scientist, I understand that such trials are an important step in the process. What I meant to argue is that such trials do little to tell us how these wonderful cells are working to repair damage, sustain residual function and improve the quality of life for patients desperate to find ways to treat their diseases, which, in many cases, are progressive and fatal.

I did not mean to suggest that patients lured by the marketing campaigns of unvetted stem cell clinics are poor or uneducated. Rather, having spoken to some, I believe they too are excited by the promise of stem cell therapies and, with the limited number of clinical trials investigating such treatments for their particular conditions, see these clinics as one of few available options.

As I wrote in my post, there are still many barriers to overcome before stem cells destined for a human host can be safely labeled for follow-up studies that will clarify their role in what so far appears to be a positive effect. I do not mean to suggest that scientists aren't working around the clock to find ways to do this. I for one am excited to learn how these cells are delivering such success, and to see how the research community continues to find innovative ways to study them and use them to help patients live better.

You are correct that it would be ideal and ultimately it will be necessary to know what the exact pathways are. However another advantage of the studies being published (besides demonstrating a certain degree of effectiveness, though often in a small sample group), is that each of these studies serves as an affirmation of safety for certain autologous therapies.

IF it were to turn out that a therapy involving autologous (or any other) cells were shown to be safe and be clearly effective (even if only in a significant minority of patients), but where the mechanism wasn't yet understood, I find it surprising you would continue to see this as a binary issue and recommend a ban on the therapy (and even a ban on publishing!).

Not all patients are poor and un-educated. In fact IF safety does become demonstrated and IF therapeutic potential is demonstrated in a significant minority, the problematic issue will indeed be how to protect poor and un-educated customers from being mis-led. But this is a separate issue that involves all sorts of medical decisions. Poor and uneducated people are getting lousy medical advice all over the world; what's new?

I am concerned that your asessment of this industry and their patients is un-scientific and in fact quite speculative. If you have data to demonstrate that most patients going to these clinics are poor and relatively un-educated, or data to demonstrate that these clinics are preying on ignorance, then I would be grateful if you could point me to the studies you are referring to.

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