I have been sceptical about the power of miRNA analysis to help with ME/CFS. I mentioned this to my pain genetics colleagues who have an interest in long non-coding RNAs and they agreed. But I wonder if we should discuss miRNAs in a bit more detail on a thread.
I can see that endometriosis cells and nearby peritoneal cells might chuck out miRNAs of a particular pattern just through random leakage, in the way that prostate specific antigen leaks out of prostate cancer cells.
What I find odd is that they should need to study 109 miRNAs to show the pattern. For most diseases where biomarkers make use of combinations of molecules it is 2, 3 or maybe 4. Presumably the 109 just reflects throwing in anything that adds a little bit more discrimination but it remains puzzling.
My main puzzlement about miRNAs is that I find it hard to see how they could be much use as deliberate biological signals, perhaps passed from one cell to another in extracellular vesicles, as is claimed. If a cell threw out vesicles then why should they reach any other particular cell rather than just got gobbled up by spleen. On the other hand if these are non-specific danger signals or possibly specific signals for lack of something specific like insulin or blood flow then maybe that would not be a worry, if specific vesicle-grabbing cells in immune organs, liver or even brainstem got the message. But then maybe you wouldn't expect any very fancy pattern of miRNAs?
In ME/CFS we do not so far have any indication that any very unusual cells, like endometrial cells, are signalling. Which makes me still sceptical that they would ever be an miRNA signature. On the other hand maybe miRNA analysis might at least tell us about immune cell populations that at present we cannot track by blood tests but which are behaving badly in a way that is reflected in miRNA output. My memory is that there have been studies from Canada but I haven't heard more about that recently.
