Passaging cells - (Jul/31/2012 )
I'm currently in debate with another member of my lab.
We've all been told that passaging cell lines too many times is not good for them and should be limited, but what does this mean?
1. Does this apply only to adherent cells? My colleague believes it cannot apply to suspension cells because all you are doing is transferring the cells to another flask with some more medium, which is hardly going to have any detrimental effect on them
2. On an equally important note, how exactly does one pronounce passage. Is it like massage or like sausage? There is someone else in my lab who says it is a silent p and should be pronounced assage.
Many thanks for your help!
Too many passages can result in the genetic and phenotypic changes of cell lines. (I saw formerly a work report where two cultures of the same cell line had different passage numbers, and the culture with higher passage number lost the described characteristics (phenotype) of the cell line, but the culture with the lower passage number retained them.)
Hi Marton, thanks for the reply
But did this report you mention apply to adherent cells or suspension cells? And how do you pronounce the word passage?
It was an adherent cell line (perhaps Caco-2). Potential genetic changes apply to both adherent and suspension cells.
The distinction between the treatment of adherent and suspension cultures probably derives from another general rule: The adherent cell lines must not culture for long time in confluent form, because they can lose their contact inhibition (Adherent cells usually stop dividing when cells reach the confluent state.) Obviously, this rule concerns only adherent cells.
I am not a native speaker, but I think it should be pronounced with 'p'. (Dictionaries usually contain the pronunciations.)
Silent "p"? Wonder where they got that from? That's a new one!
You most definitely pronounce the "p". And, in my opinion, the correct pronunciation is the same as massage, although you will find much conjecture about this- and it really doesn't matter, people will know what you mean.
(I've honestly never heard anyone pronounce it the other way though)
To passage your cells is to sub-culture or "split" them, and yes it applies to suspension cells too. Your colleague was wrong to say it doesn't. Each time you take some of your suspension cells and sub culture them into fresh media, this is a passage.
With suspension cells, you would let them grow until just before they reach maximum density (when they are still in the range that is optimal for growth), and you would sub them into new media- this would be a passage. Of course this will have an effect on the cells, growing and dividing continuously is going to have some effect on cells no matter how you are growing them.
Not sure where my colleague got the silent p from, but she is adamant she is correct and is continuing to pronounce it as "assage". Hopefully others can confirm that you are right.
Your comments were very useful, much appreciated.
Good to hear from you. My European colleague is very interested in cell passage. He is also a book reviewer but that's irrelevant. He told me that cell passage is pronounced 'assage' with a silent p so I beg to differ with leelee.
Either way I wish you all the best with your cell splitting- it sounds like you are giving it a lot of thought and that's the main thing!
Best wishes from the Middle East
Your European colleague may be French, they like omitting the letters. (For instance, they do not pronounce the first h and last e of a word. )
Agree with doles. French people have a habit of omitting words. Try and learn pronounciation from an english person YMCA
Thanks for all the comments, much appreciated. i feel that going with the p is the way to go, but YMCA's European colleague and my the girl in my lab have certainly provided an alternative point of view that must be considered.
By the way YMCA, it's interesting that your colleague is a book reviewer, since my lab colleague is considering writing a book on cell culture. She was initially interested in primary cells, but has now spent a significant amount of time studying all permutations related to the growth cycle of cell lines (in particular K562). She really is very passionate about cell proliferation kinetics, although has yet to find an exact definition of what this means.
Thanks again everyone! Any more thoughts on pronunciation will be gratefully received!