I need to evaluate the level of microRNAs in human blood, but I'm not sure which one is more credible, the plasma or serum. I would be very grateful if some one helps me? besides, as you know serum preparing process is much more easier than plasma process but which one is better?
There's no single right answer to this question. Plasma is the physiological fluid of circulating blood, serum is not, so in that sense, plasma is better. However, if all cells including anucleate platelets are not removed from plasma, most of the miRNA you detect will be in platelets. Also, if the plasma is heparinized, heparin must be removed, or it will interfere with qPCR. Some sources recommend avoiding other anticoagulants...citrate formulations are most widely recommended. Serum, as you say, is easier to prepare. On the other hand, there will be slightly more extracellular vesicles in serum that are released from platelets during clotting. If your miRNA of interest is platelet-enriched, it might (or might not) be slightly enriched in serum vs plasma. Keep in mind, though, that most extracellular RNAs in blood are not found in vesicles, so this should apply to only a subset of miRNAs.
Hi Aref,
There is no major differences between two fluids apart from clotting factor of blood- fibrinogen. You can find details in following website-
http://medimoon.com/2012/07/difference-between-plasma-and-serum/
If plasma is used, EDTA will be the better choice to isolate plasma from whole blood and heparin should be avoided because it may inhibit PCR amplification. Serum can also be used as starting material for circulating miRNA study, however complete removal of cellular component is mandatory for both plasma and serum since it could impair accurate miRNA quantification in the fluid.
Dear Dr. Kenneth W Witwer and Dear Dr. Md. Mahmodul Hasan Sohel
as I find out, it seems that plasma and serum both they are similar.
If you Don't mind, I would like to ask two more questions. Is it right to say that the most credible choice depends on target miRNA and where they are coming from?
also, in my previous experience, I had used EDTA. I just want to know that dose EDTA interference with further analysis processes or not? I'm afraid of agents deactivation in RNA extraction step. of course I had no problem but i'm afraid of tolerance in RNA concentration in different samples.
thank you for your kindly answers
best regards
Hello Aref,
There is no absolute black and white answer for this. We did a lot of expression assays after the extraction of miRNAs from plasma and blood, but it all boils down to the question that you have in mind. Sometimes, tissues are the best examples, though.
However, our concept of miRNA and its role in diseases took a major turn when we found that alien miRNAs can also survive in our system. If you have the time kindly read the attached manuscript. It will interest you.
Warm regards,
Venk
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