Question on Overgrown Cell Culture - (Jul/31/2006 )
I understand that proper cell culture requires passage when the cells are 70-80% confluent. If the cells are not passed at the appropriate time and become too confluent, is it necessary to start a new culture?
you probably dont need to. I pass them when my cells reach confluency or I do it twice a week with fixed passing ratios. In order to keep them below 70% all time, you'd do 3-4 passings/week.
I let my cultures grow 95% before I split them. They r fine. I have used them even after high passage numbers.
I disagree
It depends on your type of cells
I work with primary epidermal keratinocytes. if you let them become fully confluent, they will enter senescence shortly after...if you passage them, that passage will grow very slowly and will most likely not reach confluence, and will certainly not behave properly if you try to treat it
I would contact the manufacturer/supplier of your cells and see what they have to say? or, perhaps ATCC would be a good reference, if they carry your cell line?
It depends on the type of cell.
If it is primary cell line, split them when they are 80% confluent.
If it is cancer cell line, no problem when split them at 95% or even slightly overgown (not recommend).
The problem of spliting cell at 70% confluent may lead to more work, more medium use, more tissue culture flask, more passage of cell 
Not possible in my lab with limited budget......lack of funding...... 
I agree with aimikins and minnie that each cell type is different and have to b cultured accordingly.
I let my 293 cells to confluency and it works.
These are cancer cell lines that I'm refering to but I had heard that growing them too confluently leads to a change in overall cell behavior i.e. lower protein production, less proliferation, etc. I know that this is really important for cells with contact growth-inhibition but I don't think mine are because they do grow to confluency.
I had some bad experiences with some squamous cell carcinoma lines before. You have to pass them when these are not overgrown.
Hi,
It's a good cell culture practice not to overgrow your culture. Some cell lines change morphology and other characteristics if overgrown. For e.g. 3T3 cells get differentiated in to adipocytes if you overgrow them. Sf9 cells change their growth rate if overgrown repeatedly.
If you overgrow your cells 2 or 3 times, that's fine. But if it happens repeatedly, try to revive other vial.
Hope it helps.
Yea, I was basically just wondering if it happens 1 time, (or 2 or 3) do I need to start all over to ensure consistency with my experiments between different cultures. Thanks for all of your helpful information!!