Why Concentration Matters in Orthobiologics: My Recent TOBI Presentation

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Dose is a critical concept in medicine. In fact, a doctor who doesn’t know the dose of medication he injects into your body would lose a medical license. However, for far too long, we’ve allowed physicians practicing orthobiologic procedures to inject these products without knowing the dose. Our recent research and papers published by others show why this is not a good idea.

PRP and Dose

What if I told you that 99% of the clinics you could go to have no idea of the dose of Platelet Rich Plasma (PRP) or Bone Marrow Concentrate (BMC) they’re injecting into your body. Your first question may be, well is the dose important? The answer is that the existing research shows that it is important.

Let’s take PRP. That’s a product that’s made by concentrating platelets which are then injected. Hence, it would make common sense that knowing how concentrated those platelets are or aren’t is a critical piece of information. However, almost all of the bedside machines on the market have no ability to dial in the dose. In addition, some systems produce low-dose PRP and others mid-range dose PRP. Hence, which dose the patient gets is as random as which clinic they walked into and which machine that doctor happened to use.

Is PRP dose important? Our research into that topic began around 15 years ago when we looked at PRP dose versus mesenchymal stem cells in culture. For younger patients, the dose didn’t seem to matter. For older patients, it was critical. For example, placing the stem cells from a younger person into a culture with a low or high dose PRP made no difference in how the cells grew. However, in a patient that was older than say 40, the opposite was true. Now the more concentrated the PRP, the better the stem cells grew.

We formally performed that same lab experiment using tendon cells back in 2019 and published the results (1). We used tendon cells because tendinopathy is a common injection target for PRP. What we found was the same as what we saw with stem cells: young cells do fine with lower dose PRP while older cells are stimulated to grow more with higher concentrations of platelets. Hence, dose matters. 

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BMC and Dose

Another mainstay orthobiologics procedure is BMC or Bone Marrow Concentrate. Its name, like PRP, involves the concentration of the cells in a bone marrow aspirate. This has been used as a treatment for knee osteoarthritis. Does the concentration of BMC matter?

BMC suffers from the same simple bedside machine problem as PRP. For example, 99% of the time, when a doctor uses this injectate, there is no knowledge of the dose that comes out of the machine. Why could this be important? Let’s say a patient walks into the clinic and wants both knees injected. If the dose was important for the success of the procedure and the number of cells that this patient produced was too low, then treating one knee at a time would up the chance of a successful procedure outcome. On the other hand, treating both knees at the same time would doom the procedure to fail.

So does BMC dose matter? We did that study back in 2014 and published our results that the total number of cells injected did matter and was associated with a better outcome (2). That’s why, at all of our Regenexx sites, the dose of cells available is always measured and that information is used to inform treatment decisions.

Are we the only ones that have found that the dose of BMC matters for a good treatment result? Nope. The same thing has been seen in using BMC to inject low back discs and bone diseases like osteonecrosis (3,4). These two papers used another dose metric called CFU-f rather than the total cells in the sample.

What the Heck is a CFU-f?

While measuring the total cells in the sample can be done at the bedside and used to guide treatment decisions, for pure research purposes you can use a metric called CFU-f. That’s a rough measurement of the total number of stem cells in the sample. To get there you plate the BMC is a special flask and let the stem cells in the sample form colonies which are counted about a week to 10 days later.

The good news about this method is that you get an idea of the number of mesenchymal stem cells in the sample rather than just the total cells. The bad news is that this information takes about a week or more to get, so it won’t be available to change what the doctor does at the time of treatment. Hence, this is more of an academic exercise.

Since our research team had already looked at the effect of the total cells in a knee arthritis BMC treatment, we figured it was time to see if that relationship held up when using CFU-f. Meaning, does having more stem cells in the sample (higher CFU-f) relate to more successful treatment?

Our New Research

First, it’s important to note that no other research team on the planet is spending private funds to answer these critical orthobiologic questions. While some universities are beginning to publish in this area, this is usually using government or private endowment funds. At Regenexx, we do this research with proceeds generated by the business. Why? Because this research has to get done and on critical questions like this, nobody else is doing it.

Our new study wouldn’t have been able to be easily performed without our prior publication on using cryopreserved BMC to generate a CFU-f measurement (5). That 2019 paper clearly demonstrated that we could save research samples and then apply a conversion factor and compare those results to freshly performed CFU-f counts. That meant that we didn’t need to perform these CFU-f tests as the patients were treated, which makes this type of research less burdensome on lab staff.

What did we find? See the video above for my presentation on this data at a recent major orthobiologics conference for details, but we found that a higher CFU-f correlated to better outcomes. So again, we found that dose matters.

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Why This is Important?

I can’t emphasize enough, that DOSE MATTERS! It’s critical for success in PRP and BMC procedures, but again, despite this emerging research, 99% of the physicians out there using these products don’t know what dose they’re injecting. Again, at Regenexx, we’ve known this rule for years, which is why we require all of our PRP and BMC injections to be dosed.

If you’re a doctor, then how you draw bone marrow also matters. If you draw it in many low-volume aliquots you get more stem cells. If you perform a lazy draw and try to get the entire volume from a single site, you’re short-changing the patient by reducing the likelihood of successful treatment. Also, which system you use to concentrate the bone marrow matters. Low concentration systems that produce high volumes of BMC are less likely to be effective than systems that produce a low volume that’s highly concentrated.

The upshot? The dose is a critical concept in medicine and in orthobiologics. Our research and that of others clearly demonstrate this concept. Hence, make sure that the doctor who performs these procedures on you or a loved one knows the dose of the PRP or BMC that they inject, as that may just determine if the procedure you get is effective or fails.



(1) Berger DR, Centeno CJ, Steinmetz NJ. Platelet lysates from aged donors promote human tenocyte proliferation and migration in a concentration-dependent manner. Bone Joint Res. 2019 Feb 2;8(1):32-40. doi: 10.1302/2046-3758.81.BJR-2018-0164.R1. PMID: 30800297; PMCID: PMC6359887.

(2) Centeno CJ, Al-Sayegh H, Bashir J, Goodyear S, Freeman MD. A dose response analysis of a specific bone marrow concentrate treatment protocol for knee osteoarthritis. BMC Musculoskelet Disord. 2015 Sep 18;16:258. doi: 10.1186/s12891-015-0714-z. PMID: 26385099; PMCID: PMC4575428.

(3) Pettine KA, Murphy MB, Suzuki RK, Sand TT. Percutaneous injection of autologous bone marrow concentrate cells significantly reduces lumbar discogenic pain through 12 months. Stem Cells. 2015 Jan;33(1):146-56. doi: 10.1002/stem.1845. PMID: 25187512.

(4) Hernigou P, Beaujean F. Treatment of osteonecrosis with autologous bone marrow grafting. Clin Orthop Relat Res. 2002 Dec;(405):14-23. doi: 10.1097/00003086-200212000-00003. PMID: 12461352.

(5) Berger DR, Aune ET, Centeno CJ, Steinmetz NJ. Cryopreserved bone marrow aspirate concentrate as a cell source for the colony-forming unit fibroblast assay. Cytotherapy. 2020 Sep;22(9):486-493. doi: 10.1016/j.jcyt.2020.04.091. Epub 2020 Jun 19. PMID: 32565131.

Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications. View Profile

If you have questions or comments about this blog post, please email us at info@regenexx.com

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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