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Rotator Cuff Stem Cells More Likely to Become Fat than Muscle?

POSTED ON IN Shoulder BY Chris Centeno

Some patients with rotator cuff tears have a problem that most don’t know exists. Their rotator cuff muscle begins to atrophy and when this happens, surgical repairs are less likely to be successful. So what causes this issue is a big deal. Now, new research shows that the problem may lie more in the cells that make up the rotator cuff. Let me explain.

Understanding Rotator Cuff Tears

The rotator cuff is made up of a variety of muscle and tendon subparts that form into a single muscle unit in the shoulder. The shallow ball-and-socket shoulder joint has the greatest range of motion of any joint in the body, and a healthy rotator cuff supports all of the joint’s complex motions and keeps the entire structure nice and stable.

As with most muscles, the rotator cuff can become injured when the shoulder is overstressed. For example, when lifting a heavier load overhead than the muscle can comfortably support, the rotator cuff can tear. Tears, however, aren’t just the result of overloading the joint; they also happen as we age due to normal wear and tear. It’s important to understand that normal-wear rotator cuff tears may or may not result in shoulder pain, so when these are found on MRI, it shouldn’t be assumed that they are the cause of the pain.

Why the Rotator Cuff Isn’t the Best Self-Healer

It’s well known that the rotator cuff isn’t very good at healing itself. First, we know that as we age, the blood supply to the rotator cuff lessens. Second, I also shared a study that found that there may be fewer stem cells in the shoulder area when there are rotator cuff tears. What does this mean exactly? Our stem cells are the body’s repair cells, and when an area is stem-cell deficient, it can’t properly repair those small injuries that occur over time. In the shoulder, this failure to heal the small things may eventually lead to rotator cuff tears with aging.

Finally, there may also be a genetic connection to why the rotator cuff isn’t a very good self-healer. Another study found that specific gene expressions in rotator cuff tear patients were responsible for cells making proteins that would then break down tissue and not for making new tendon cells that would be necessary for helping to heal the tear. In any of these cases, add rotator cuff surgery to the mix, and it makes sense that operating on this already weakened tissue that has limited ability to self-heal may make things worse.

Now, there’s a new study that expands more on the rotator cuff and what really happens with those stem cells when repair is needed.

Rotator Cuff Stem Cells May Be More Likely to Become Fat than Muscle

The new study compared stem cell differentiation in both the rotator cuff muscle in the shoulder and the gastrocnemius muscle in the leg. In this animal model, they used the resident muscle stem cell known as a satellite cell. Stem cells affect healing by moving into the damaged area and typically differentiating into, or becoming, the specialized cell type necessary to repair the tissue (for further explanation on differentiation, watch my brief video to the right).

The results in this case? The rotator cuff satellite cells differentiated into 23% fewer muscle cells than those from the gastrocnemius. In addition, there was a four-fold increase in adipogenesis (fat production) by the rotator cuff satellite cells.

In addition, researchers also found hundreds of differences in gene expression in the two muscles with the rotator cuff showing heavy expressions in those involved in lipid metabolism and adipogenesis, causing them to suggest both cellular and gene expression links to the adipogenesis in the rotator cuff. They also suggested transplanting satellite cells from other muscles into the rotator cuff to improve the chances of muscle tissue rather than fat.

Getting the Right Stem Cells to the Rotator Cuff

This study may explain why fat atrophy (those fatty deposits that cause muscle weakness) is a problem associated with poor rotator cuff surgery outcomes; as the body attempts to self-heal, those rotator cuff stem cells may differentiate into fat cells rather than muscle cells. So how do we get the right kind of stem cells to the rotator cuff to facilitate healing?

One way to do this may be focusing on the bone marrow cells. One of those cell types, hematopoietic stem cells, are found in muscles of animals that are excessively exercised. This and other studies (study 1, study 2) has led researchers to conclude that bone marrow stem cells participate in natural mechanisms of muscle repair. Hence, does it makes sense to directly inject these cells into these damaged muscles? One easy way of doing that would be injecting bone marrow concentrate into torn rotator cuff muscles. However, does this help real patients? For example, one recent study concluded that performing a rotator cuff repair and then injecting bone marrow stem cells during the surgery reduced re-tear rates.

Do you always need the surgery? In our experience and based on what we are finding in our own rotator cuff tear randomized controlled trial (RCT), in select patients, most of these same results can be had by skipping the surgery. In these cases, we replenish bone marrow stem cells through precise injections. Learn more about this RCT by watching my video below:



The upshot? This problem with rotator cuff muscle stem cells wanting to become fat may be the reason why we see fat atrophy in this injured structure. In the meantime, we now have research that suggests that adding in bone marrow stem cells to the tear, which can replace the function of muscle satellite cells, is likely a good idea to promote healing.






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    Edith(Edy)Johnson says

    Thanks for the information. Had MRI on Shoulder. I am making the decision as to stem cell with you or surgery.
    Need to know if this is Caymen Island trip?
    Approximate Cost....
    Am not taking Nexium
    Smiles to you,


    Regenexx Team says

    Hi Edy,
    We'd need more information through a Candidacy review to see what type of treatment is needed, which would affect cost. We'd be the first to tell you if surgery was needed! Please give us a call at 303 429 6488 and the team can set that up, or if you prefer, they can contact you.


    Steve says

    I have a full thickness tear 1.5 cm/surgeon says it won’t heal with stem cells and says atrophy will be the I a candidate for this treatment?


    Regenexx Team says

    Hi Steve,
    That's not a surprise. There is process to determine Candidacy for a Regenexx procedure. To do that please use the "Get Started" button here: Once the doctor has reviewed all your MRI images, taken a full medical history and has had an opportunity to speak with you in depth about your shoulder in this process, we'll be able to answer your question.


    Riyaz says

    I m having arthritis problem in knee can i go for stem cell therapy


    Regenexx Team says

    Hi Riyaz,
    We treat knee arthritis regularly. Please call 855 622 7838 for assistance in setting up a Candidacy review.


    Larry kaplan says

    My doctor is ordering an MRI for my shoulder that has major torn rotator cuff & major arthritis per XRay. Are there any specific instructions that my doctor might be overlooking, or is an MRI simply an MRI ?


    Regenexx Team says

    Hi Larry,
    Just a regular MRI at least 1.5T or greater. The 1.5T refers to the strength of the magnet, which determines the clarity of the images. The higher the number, the clearer the images.


    Carol Hall says

    I had a full rotator cuff tear. Surgery was recommended. I couldn’t face 6 weeks minimum of total inability to use my dominant hand and resulting dependency. Luckily, I found Regenexx and got stem cell treatment from Dr Bashir at the Adventura, FL , Ocyon Regenexx center. I have regained 90% of my arm usage afterr stem cell treatment and physical therapy. It took some time and money, but I am very satisfied with my results.


    Regenexx Team says

    Hi Carol,
    Thanks for sharing your great news!


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    About the Author

    Chris Centeno

    Christopher J. Centeno, M.D. is an international expert and specialist in regenerative medicine and the clinical use of mesenchymal stem cells in orthopedics. He is board certified in physical medicine as well as rehabilitation and in pain management through The American Board of Physical Medicine and Rehabilitation.…

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