A Bad MSC Meta-analysis Is a Great Way to Learn About Stem Cells

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dai metaanalysis systemic review mesenchymal stem cells knee osteoarthritis

Some orthopedic surgeons have a bizarre love-hate relationship going on with injection-based knee arthritis stem cell therapy while others have embraced it. Let’s dig into this phenomenon through a poorly accomplished meta-analysis published in a big orthopedic journal and learn quite a bit about the actual science of stem cells and knee arthritis in the process. Let’s jump in.

The Love-Hate Relationship with Stem Cells

Some orthopedic surgeons have a strange relationship with stem cells. The forward thinkers in the field have welcomed this major disruption of their world and begun to help patients avoid surgeries. Basically cannibalizing what they do because these less invasive procedures can be better for their patients. On the other hand, there are stalwarts who don’t like change and who view this whole concept as a scam.

You can’t blame the stalwarts because there’s a ton of fraud going on, which is a very real problem for their patients. However, if these procedures are as revolutionary as the legitimate players who publish research claim, then their entire ortho world is about to be turned upside down. No single document exemplifies this bizarre relationship better than a recently published meta-analysis in the orthopedic journal Arthroscopy.

What Is a Meta Analysis?

When there are many different studies published on a single treatment, there’s a technique called a meta-analysis where you can pool all of that data together from different studies and analyze it as one data set. So for example, if you have 4 studies about treatment A, of 50, 100, 75, and 50 patients, you can lump all of those patient results together to analyze data from 275 patients. The idea is that a research project with 275 patients is more powerful than any of the individual papers.

Hence a meta-analysis is a study of studies. As a result, these are often used to drive public policy. As I show you today and tomorrow, this new one published in a prestigious orthopedic journal isn’t worth the paper it’s written on.

The New Paper on Stem Cell Treatment for Knee Arthritis

The authors of the new paper have created a striking title: “Intra-articular Mesenchymal Stromal Cell Injections are no Different than Placebo in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials”. Hence, you don’t need to read that far to figure out that this meta-analysis concluded that stem cell therapy for knee arthritis didn’t work.

The authors took 13 different papers published using the term “stem cell” where knee arthritis was treated with injections (1). They then analyzed the data in several different ways. As the title telegraphs, ultimately, they concluded that the therapy was ineffective for knee arthritis.  However, digging deeper and looking under the hood shows that the study proved no such thing. In fact, it’s a huge mess.

Lumping Together Vastly Different Therapies

This field of regenerative medicine has always suffered from a severe naming problem. It’s because of that issue that many clinics can scam patients by delivering completely different treatments and then slapping the term “stem cells” on the therapy. However, it’s not just patients that confuse all of this, but physicians and researchers who should know better.

The main issue that causes this particular paper to fall apart in taters is simple. The authors called all of the therapies from the 13 papers “mesenchymal stem cell injections”. By doing that, they created a fiction that all of these treatments were the same, when in fact they couldn’t be more different.

As reviewed above, the hallmark of a meta-analysis is that it lumps all of the data together because the therapy is the same or very similar. However, this study grouped together the following therapies from 13 studies that have little to do with each other:

  • Cultured expanded bone marrow MSCs
  • Culture-expanded adipose MSCs
  • Stromal Vascular Fraction (SVF)
  • Culture expanded placental MSCs
  • Culture expanded umbilical cord MSCs
  • Bone Marrow Concentrate (BMC) with PPP

Just going over why these therapies are vastly different and can’t scientifically be aggregated will shine some light on a tremendous amount about stem cells. The differences can be broken down into three main categories:

  • Processed Cell Mixtures
  • Cultured Expanded and Isolated Cells
  • Different Cell Sources

Let’s now analyze why these treatments are HUGELY DIFFERENT.

Processed Cell Mixtures

Two of the therapies above contain mixtures of lots of cells where the minority of those cells are “mesenchymal stem cells”. These are SVF and BMC. These are both dramatically different in many ways.

SVF is created by digesting fat tissue to break down the structural collagen and then centrifuging out the cells. What you get is a mixture of different white blood cells, red blood cells, macrophages, hematopoietic stem cells, other cells, and some mesenchymal stem cells (2).

Bone marrow concentrate is created by taking bone marrow aspirate (the liquid portion of the bone marrow) and centrifuging it to isolate the buffy coat. That contains a mixture of different white blood cells, red blood cells, macrophages, hematopoietic stem cells, other stem cells, progenitor cells, and some mesenchymal stem cells (5).

First, the percentage of mesenchymal stem cells differs between these two. While fat has more of these, the MSCs in the bone marrow are more efficient at cartilage repair (6-18). Second, there are vast differences in the non stem cell components of these mixtures. For example, while SVF is poor in hematopoietic stem cells (HSCs), bone marrow is rich in these cells. So in the end, these cell mixtures are as different as two different drugs (19,20).

In addition, if we just took one of these mixtures and tried to compare just that type across different bedside machines there would also be vast differences. For example, a study I performed with a Stanford researcher several years back found huge differences between different BMC mixes used in clinical practice (5).

Cultured Expanded and Isolated Cells

If the above therapies are a mix of different cells, this category is the opposite. Here, the above products of tissue digestion and centrifugation are then plated in tissue culture to isolate only the adherent MSCs. This is then repeated multiple times until you get a “pureish” mixture of cells that are called MSCs.

We still have the same problems as above, as the adipose MSCs will perform differently than the bone marrow cells which will perform differently than the placental cells which will perform differently than the umbilical cord cells (3, 4, 21-23). In fact, how you grow these cells will also change their final properties on the body. For example, were they grown in a culture media that’s from a different animal? (24) The same animal? The same patient or a different patient? With exogenous growth factors or not? All of these choices produce different cell lines (25, 26).

Different Cell Sources

As I alluded to above, we have four different cell sources here:

  • Adipose
  • Bone marrow
  • Placenta
  • Umbilical cord

At best these MSCs are distant kissing cousins rather than identical twins. For example, if we take the ability of these cells to suppress inflammation, they are all massively different. There are also other cell properties that make these cells for all intents and purposes, different therapeutics (27-32).

A Meta-Analysis of Different Therapies?

Pooling data on a specific therapy from different studies obviously requires that the therapy is the same. Given that these authors looked at 13 studies that used six very different therapies, the paper falls far short with just a basic critique. Meaning that it isn’t a meta-analysis and the data can’t be pooled or even compared head to head.

How Did this Paper Get Published?

Arthroscopy is a high impact orthopedic journal. Did the reviewers not understand that these were VERY different therapies? Could they be that oblivious to what’s published in the literature?

This brings me back to my initial thoughts. The publication of research is often very political. Does one side of an issue or another want the message driven home by the study to get out there and are they willing to overlook a few nasty warts to get it published? In this case, this paper fails at being able to support its most basic structural concepts, yet somehow it got greenlighted in a major journal.

The upshot? This paper is a mess of gargantuan proportions. I’ve covered only one issue here, but tomorrow I’ll uncover many more. Hence, this article doesn’t actually show that these therapies are ineffective. In fact, tomorrow, I’ll show you how the paper actually shows the opposite.

_________________________________

References

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(2) Brown JC, Shang H, Li Y, Yang N, Patel N, Katz AJ. Isolation of Adipose-Derived Stromal Vascular Fraction Cells Using a Novel Point-of-Care Device: Cell Characterization and Review of the Literature. Tissue Eng Part C Methods. 2017 Mar;23(3):125-135. doi: 10.1089/ten.TEC.2016.0377. PMID: 28177263.

(3) Wu C, Chen L, Huang YZ, Huang Y, Parolini O, Zhong Q, Tian X, Deng L. Comparison of the Proliferation and Differentiation Potential of Human Urine-, Placenta Decidua Basalis-, and Bone Marrow-Derived Stem Cells. Stem Cells Int. 2018 Dec 13;2018:7131532. doi: 10.1155/2018/7131532. Erratum in: Stem Cells Int. 2019 Mar 10;2019:1651506. PMID: 30651734; PMCID: PMC6311712.

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(13) Mehlhorn AT, Niemeyer P, Kaiser S, Finkenzeller G, Stark GB, Südkamp NP, Schmal H. Differential expression pattern of extracellular matrix molecules during chondrogenesis of mesenchymal stem cells from bone marrow and adipose tissue. Tissue Eng. 2006 Oct;12(10):2853-62. doi: 10.1089/ten.2006.12.2853. PMID: 17518654.

(14) Hennig T, Lorenz H, Thiel A, Goetzke K, Dickhut A, Geiger F, Richter W. Reduced chondrogenic potential of adipose tissue derived stromal cells correlates with an altered TGFbeta receptor and BMP profile and is overcome by BMP-6. J Cell Physiol. 2007 Jun;211(3):682-91. doi: 10.1002/jcp.20977. PMID: 17238135.

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(17) Xie X, Wang Y, Zhao C, Guo S, Liu S, Jia W, Tuan RS, Zhang C. Comparative evaluation of MSCs from bone marrow and adipose tissue seeded in PRP-derived scaffold for cartilage regeneration. Biomaterials. 2012 Oct;33(29):7008-18. doi: 10.1016/j.biomaterials.2012.06.058. Epub 2012 Jul 19. PMID: 22818985.

(18) Reich CM, Raabe O, Wenisch S, Bridger PS, Kramer M, Arnhold S. Isolation, culture and chondrogenic differentiation of canine adipose tissue- and bone marrow-derived mesenchymal stem cells–a comparative study. Vet Res Commun. 2012 Jun;36(2):139-48. doi: 10.1007/s11259-012-9523-0. Epub 2012 Mar 4. PMID: 22392598.

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(23) Wegmeyer H, Bröske AM, Leddin M, Kuentzer K, Nisslbeck AK, Hupfeld J, Wiechmann K, Kuhlen J, von Schwerin C, Stein C, Knothe S, Funk J, Huss R, Neubauer M. Mesenchymal stromal cell characteristics vary depending on their origin. Stem Cells Dev. 2013 Oct 1;22(19):2606-18. doi: 10.1089/scd.2013.0016. Epub 2013 Jun 22. PMID: 23676112; PMCID: PMC3780294.

(24) Joswig AJ, Mitchell A, Cummings KJ, Levine GJ, Gregory CA, Smith R 3rd, Watts AE. Repeated intra-articular injection of allogeneic mesenchymal stem cells causes an adverse response compared to autologous cells in the equine model. Stem Cell Res Ther. 2017 Feb 28;8(1):42. doi: 10.1186/s13287-017-0503-8. PMID: 28241885; PMCID: PMC5329965.

(25) Seo JP, Tsuzuki N, Haneda S, Yamada K, Furuoka H, Tabata Y, Sasaki N. Comparison of allogeneic platelet lysate and fetal bovine serum for in vitro expansion of equine bone marrow-derived mesenchymal stem cells. Res Vet Sci. 2013 Oct;95(2):693-8. doi: 10.1016/j.rvsc.2013.04.024. Epub 2013 May 16. PMID: 23683731.

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(30) Ma J, Wu J, Han L, Jiang X, Yan L, Hao J, Wang H. Comparative analysis of mesenchymal stem cells derived from amniotic membrane, umbilical cord, and chorionic plate under serum-free condition. Stem Cell Res Ther. 2019 Jan 11;10(1):19. doi: 10.1186/s13287-018-1104-x. PMID: 30635045; PMCID: PMC6330472.

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(32) Ibrahim AM, Elgharabawi NM, Makhlouf MM, Ibrahim OY. Chondrogenic differentiation of human umbilical cord blood-derived mesenchymal stem cells in vitro. Microsc Res Tech. 2015 Aug;78(8):667-75. doi: 10.1002/jemt.22520. Epub 2015 Jun 12. PMID: 26096638.

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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