Does Highly Concentrated PRP Hurt Tendons?

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Injecting platelet rich plasma (PRP) into chronically injured or damaged tendons has revolutionized the care of tedinopathy. However, these last few years, alarm bells have been raised in the PRP injection community that injecting higher concentrations of PRP can have a negative effect on tendons. So is this a real thing, or should doctors and patients not be concerned?

Why You Should Care?

Regenerative orthopedics right now is in its infancy, with few standards. Just about anyone with a heartbeat and a driver’s license can buy a PRP machine and begin injecting tendons, ligaments, and joints. Given that medical schools and residency programs have yet to catch up with this new technology, almost everything a physician learns about PRP is outside of traditional medical education channels. Anytime that happens in a new field, misinformation abounds. Given that most of the education in this field is financially sponsored by the manufacturer of one machine or another, it’s not hard to see how information can get confused.

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What Is PRP and How Can that Help Tendon Problems?

PRP stands for platelet rich plasma, a mix of concentrated platelets made from whole blood. There are now several studies, including high-level research, that show that PRP injections can help chronically damaged or injured tendons heal. They do this by releasing growth factors that act like espresso shots for local cells that can help healing.

What’s the Deal with Concentrated PRP and Tendons?

Last year a paper came across my desk that surprised me. Given that we have extensive experience with PRP and stem cells, this new research seemed to go opposite to what we had observed. While our in-vitro research had shown that higher PRP concentrations helped stem cells grow better (this effect is even bigger with older stem cells), this new paper seemed to show that higher PRP concentrations hurt tendon cells (tenocytes). Huh? After I did some more research, I found at least one other paper that reached a similar conclusion and sent the papers to our advanced research team. A few weeks later, during our weekly research meeting, our team relayed that they had found some serious flaws in the research I had sent them.

The problem that our team uncovered was that as the platelet concentrations increased in these studies, the authors ended up neglecting to adjust the amount of cellular food (called MEM for minimal essential media). Hence, as PRP concentrations climbed, the amount of food declined. So what the papers reported was likely an artifact of inadvertently starving the cells. To make sure, our team repeated the experiment using stem cells in our lab:

best PRP concentration

These graphs show higher bars as cells grow better and lower bars as they aren’t growing. The graph on the left increases the platelet concentration as the food supplies (in this case alpha-MEM) are kept constant. Note that increasing platelet concentration helps the stem cells grow better, up to 7X (seven times more concentrated than baseline), and then the effect levels off. On the right, the graph shows what happens when you increase platelet concentrations as you decrease food supplies (like the two papers mentioned above). In that case the stem cells starve and can’t grow.

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How Do You Explain Something Complex That Physicians Missed?

When our research team presented this new data above in the context of another project, I got an idea on how to present this to physicians and patients alike. After all, when I first told some physicians about this, since it involved complex cell-culture principles that even the scientists who authored these papers had missed, I saw their eyes glaze over. The above video is my attempt to coalesce all of this into a three-minute format!

The upshot? There is no credible research showing that injecting tendons with high concentrations of PRP is a problem! In fact, based on other data we’ve collected through the years, older cells may really do much better with much higher concentrations. So concentrate that PRP when injecting tendons and leave the fear behind!

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NOTE: This blog post provides general information to help the reader better understand regenerative medicine, musculoskeletal health, and related subjects. All content provided in this blog, website, or any linked materials, including text, graphics, images, patient profiles, outcomes, and information, are not intended and should not be considered or used as a substitute for medical advice, diagnosis, or treatment. Please always consult with a professional and certified healthcare provider to discuss if a treatment is right for you.

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