How to Interpret Flow Cytometry Reports from Amniotic "Stem Cell" Vendors
POSTED ON 3/22/2018 IN Regenerative Medicine Education BY Christopher Centeno
If you are a regenerative medicine physician, you are likely being bombarded by vendors pushing amniotic and cord tissue products, claiming they contain stem cells. They're also likely shoving numerous reports under your nose, attempting to prove their claims. If you're a patient, a doctor who was convinced by one of these reports may have provided it to you. But be honest with yourself—do you really understand what's in those reports? I ask because I have yet to see a single report that shows that these products have live and functional stem cells. Let's look at one in particular: the flow cytometry report.
What is a Flow Cytometry Report?
Flow cytometry simply involves using lasers to find the presence or absence of certain cell surface markers. Based on what is expressed (+) or isn't expressed (-) on the surface of the cell, this how the cell is identified. For mesenchymal stem cells, these markers are well known. Because it can identify cells, the flow cytometry report is frequently used to provide street cred. So what exactly are these amniotic and cord tissue vendors really identifying in these flow cytometry reports they are providing, and how do you interpret these reports on your own (meaning without the vendor asserting what the report shows)?
How to Interpret Amniotic Products Flow Cytometry Reports
Before I get into how to interpret the flow cytometry data on your own, let's address the why. If the vendor explains it, why should you also have to be able to interpret it? As I mentioned before, I have yet to see a report that shows living and functioning stem cells in amniotic and cord products, yet I've had plenty of vendors showing me reports that they claim as proof. If you don't know how to interpret the report and you take the vendor's word, you may end up treating your patients with a product that contains dead stem cells or no stem cells. It is imperative that you know what is really in a product before you purchase it. First, be sure to watch my short video above (it intentionally has no sound) to see images of the flow cytometry data along with a step-by-step process of reading through and interpreting the data. I'm going to highlight a few things from the video below. Identifying Mesenchymal Stem Cells and Hematopoietic Stem Cells To understand the flow cytometry, you have to know how to identify the surface markers for mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs). What do you need to identify a mesenchymal stem cell? The following surface markers must be expressed on mesenchymal stem cells: CD73, CD105, and CD90. MSCs must also lack expression of the following surface markers; CD34, CD45, CD11b or CD14, CD19 or CD79alpha, as well as HLA-DR. So an MSC has CD90, CD73, and CD105—and doesn't have a whole bunch of others. Hematopoietic stem cells are identified by the cell surface marker CD34+ and can also have some others. In the example of the vendor's flow cytometry provided in the video, we have the following surface markers and their percentages:
**Stem cells Markers
In the example in the video, 2.8% of cells had the cell surface marker CD90, but we see no CD105 or CD73, which according to the ISCT standards these MUST be present on the same cell to identify mesenchymal stem cells. CD90 is common on many other cell types, so without the other two markers, we aren't identifying at MSCs here. The example also showed CD34-CD45 at 0.2%. So 0.2% of cells didn't have CD34 (CD34-) and did have CD45. Hematopoietic stem cells require the CD34+ marker, but only the absence (CD34-) not the presence (+) of the marker was tested here. CD45, which we see is at 60.5%, is not an MSC surface marker, so it is not identifying stem cells on this flow cytometry report. Why is it important to know how to interpret amniotic product flow cytometry reports? To identify MSCs or HSCs, you also can't have HLA-DR (showing 4.5%) or CD14 (showing 23.3%). So despite the "**Stem cells Markers" claim printed right on the report, the interpretation shows no MSC or HSC stem cells!
What Does a Flow Cytometry Look Like That Does Identify Stem Cells?
So what would a flow cytometry test identifying a significant number of mesenchymal stem cells look like? Again, be sure to watch the video to see an example, but to summarize the report, you would see a percentage showing expression of the CD105+/CD73+/CD90+ surface markers and a lack of expression of the following markers: CD45-/CD34-/CD14-/CD19-/HLA-DR- . The upshot? It takes a little knowledge to understand flow cytometry reports. However, all of them out there that have been offered by amniotic and cord blood vendors that I have seen DO NOT show the presence of stem cells. This is despite what's written on the report and the assertions of sales reps who wouldn't know what the report actually shows if their life depended on it. So educate yourself!
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