Cell passage nomenclature - (Apr/12/2006 )
When we freeze down cells, are we supposed to consider it as an additional passage. Or are the cells considered to be at the same passage number as the last passage when they were frozen? I know it is common to increae passage number by 1 when we thaw cells but is it the same when we freeze down cells? EX: if cells are at passage 9 before we freeze, are you going to consider freezing as another passaging and therefore label the cryovials to be containing cells at passage 10 or 9? It is a common practice, I believe to consider thawing cells as a passage. Therefore if cells were frozen at passage 9, the thawed out cells would be considered to be at passage 10 and the passage history starts from there.
I always freeze at say passage 9 before the freeze then thaw and call it passage ten. To be honest with you though passage numbers are only VERY rough approximations anyway unless yo always grow to exactly the same density every passage and then perform an identical split i.e if on one of the passages you split 1:5 instead of the usual 1:10 then do you add half a passage number? If you really want to track your cells you should calculate population doublings but no one ever does.
To answer your question though it really doesn't matter as long as you keep it consistant.
Yep, it doesn't matter as long as you (and the people you share cells with) are consistent.
I use trypsinisation as my "passage" counter. So I'd freeze those cells as passage 10, and plate them as 10s after thawing.
Thanks to all for your input
i keep the splitting protocol same (ex; 1:5), then i consider trypsinization as my passage change.
assume i freeze i million cells when i plate them those r still one million or little less (coz of death). since the cell number is same before freezing n after freezing i would not consider it as a passage.