Stem-ish cells: what’s the real thing?

Ain’t nothing like the real thing…right?

No, by the ‘real thing’ I’m not talking about Coke versus Pepsi or Coke versus Diet Coke, but rather stem cells. (On a side note there’s still some people who apparently believe the stem cell myth that there are stem cells in Pepsi).

I get a regular stream of emails from patients and sometimes phone calls asking questions about stem cells and especially stem cell treatments, but at times I’m not sure the treatment in question really involves stem cells. There are also thousands of papers published on “stem cells.”

Maybe those doing research on the cells in question or selling the cells at a clinic or writing about the cells as a journalist all think that the cells are stem cells, but how do we know? Even things that are mostly really stem cells have some progenitor or differentiated cells in the mix too that spontaneously pop up.

Many things are called “stem cells” when they aren’t the real thing or when they are a mixture of cell types of which only one is really a stem cell. For example, there has been a whole debate about MSCs or mesenchymal stem cells. Some have proposed changing the meaning of the MSC acronym to no longer include “stem” because MSCs as typically purified and used may only contain a minority population of actual stem cells unless they are carefully sorted. As a result, other names such as “mesenchymal stromal cells” and even “medicinal signaling cells” have been used or proposed to replace the standard meaning of the MSC acronym. One other issue with the MSC name is that it is an umbrella term that is often applied to very different preparations of cells.

This “not the real thing” reality of some MSCs not being pure stem cells isn’t necessarily a bad thing depending on context and how they are portrayed, but it does make life complicated. Each type of MSCs should be thought about for what they actually are in terms of research and then in addition in marketing by for-profits. It’s important for patients to know that generally the clinics selling MSCs are not using pure populations of actual stem cells with wide potency to address health issues throughout the body related to diverse tissues generally unrelated to MSCs.

The bottom line is that “MSCs” are often not going to be pure stem cells. I’d say they are generally stem-ish cells with the important exception that some researchers do purify stem cells that are referred to as MSCs.

A product called platelet rich plasma (PRP) is often portrayed as being the basis of stem cell therapies too. While PRP is frequently combined with MSCs and so the combined product might have some actual stem cells in it, PRP is largely an acellular fluid product with molecules from platelets that might have some useful properties. For this reason, I’d say that PRP is not even stem-ish even though it is sometimes even alone called a stem cell therapy.

Then there is the whole “birth-related” stem cell arena that is very tricky. There are an increasing number of clinic firms injecting stuff that is marketed as “stem cells” into customers, when in fact there not only aren’t stem cells in it but also there are no living cells at all. It’s just an extract from placenta or amniotic membrane.

As I discussed before, the irony here is that many clinics know that their product isn’t living stem cells, but they market it that manner anyway to attract customers even though if regulators were to come knocking the firms would probably often point to the fact that they aren’t really using living stem cells since that changes how regulators handle biologic products (see, “Wanted both dead & alive: amniotic stem cell clinics sell zombie cells?“). I’m still not even sure that living amnion has many stem cells to start with in utero.

Finally, there’s the special case of fat-derived stromal vascular fraction or SVF, which is generally portrayed as “stem cells”. Actually SVF is often kind of a mystery product that I’d guess has a dozen or more cell types in it, only maybe one or two of which are stem cells. For instance, many of the MSCs in SVF may not be stem cells. I suppose SVF is stem-ish and it is probably a useful product for some narrow applications, but not some stem cell-centric panacea.

So when we read, hear, write, or say, “stem cells”, we should think about what is being referred to and perhaps ask yourself, “is that the real thing or just stem-ish cells?”