The stem cell universe is populated by sometimes mysterious acronyms (see an image of a whole alphabet stem cell acronym soup), many of which refer to specific kinds of stem cells including one nebulous type called MUSE cells.
I’m not convinced that MUSE cells exist, but oddly there appear to be four clinical trials ongoing in Japan based on MUSE cells. So somebody believes in them. Is the clinical work using MUSE cells in Japan allowed because of the more permissive regenerative medicine regulatory framework there?
I found just over 50 papers with MUSE in the title on Pubmed. I found no registered trials on them on Clinicaltrials.gov.
MUSE stands for MUltilineage differentiating Stress Enduring cells. Right off the bat MUSE’s full name reminds me of the debunked STAP cells. The STAP acronym stands for Stimulus-Triggered Acquisition of Pluripotency. STAP cells were supposed pluripotent stem cells made by stressing non-stem cells out, most famously by dipping them in an acid bath. That was bogus.
MUSE cells are also supposed to be pluripotent stem cells, this time coming from adult tissues and apparently can deal with stress pretty well based on their name. Extreme stress is reported as a way to enrich for MUSE cells as it kills other cell types.
When I think of MUSE, another supposed stem cell type called very small embryonic stem cell-like (VSEL) cells comes to mind too. They are yet another member of the group of supposed adult pluripotent stem cell class. I don’t believe VSEL naturally exist and tend to think of them as the Sasquatch of the stem cell field.
It’s concerning that in each case only a few scientists apparently can find any of these mysterious cell types. So who does believe in MUSE? A few groups, but their main proponent is Professor Mari Dezawa.
She and her team recently had a massive paid ad (that looked like a regular Nature article) in Nature on MUSE that I called out for being a concerning hybrid ad-article that many readers might confuse as peer-reviewed science in Nature. After I raised my concerns, Nature pulled the MUSE ad-article. That situation didn’t exactly boost my confidence in MUSE.
Dezawa has gone so far as to assert in a paper that MUSE present in non-stem cell cultures such as of fibroblasts might explain the production of iPS cells rather than actual full reprogramming occurring, which is a controversial idea.
So could MUSE cells actually exist despite broad skepticism?
I tend to doubt it, but how can we be 100% sure either way? It may be difficult.
To get some opinions, in recent months I reached out to a handful of scholarly stem cell scientists and none believed in MUSE cells.
Below is a quote from a past article I did on MUSE that also provides more background. I’m just including it here again rather than restating it anew (note that the experts I mentioned in this quote are mostly different than the ones I asked more recently):
“However, I am not so convinced that MUSE cells exist as a normal, easy to isolate population of stem cells that have substantial utility. Other experts with whom I talked feel likewise.
An NBC News article in 2013 on MUSE quoted Martin Pera, who expressed caution as well:
“Both the [Dezawa] work and the current study are interesting but preliminary,” Martin Pera, program leader of Stem Cells Australia, and a professor at the University of Melbourne, said. “Evidence that MUSE cells can actually turn into a wide range of mature functional body cells is somewhat limited.”
One puzzle admitted even by the researchers is that the MUSE cells do not form teratoma, a type of tumor generally readily produced in the laboratory by true pluripotent stem cells. Other purported adult pluripotent stem cells have also failed to make teratoma, raising skepticism, although if these cells were truly pluripotent their lack of teratoma forming activity would be good from a safety perspective.”
Isn’t it extra risky to do clinical trials with cells that seem so dubious? Certainly the trials are using some kind of cells, but what are they exactly? The trials are run by “Life Science Institute Inc., the group company of Mitsubishi Chemical.”
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