MDCK is good morphology condtion in DMEM when passaged in our lab shows slightly different and bigger in DMEM prepared by us. Its difficult to find out why. We don't use CO2 during incubation and is it making this difference?
WE add DMEM one packet, 10ml vitamin soln, 10ml antibiotic- antimycotic soln, 2g sodium bicarbonate into 1 lit of HEPES solution and after filtration (0.2micro) we add FBS 10%.
WE add DMEM one packet, 10ml vitamin soln, 10ml antibiotic- antimycotic soln, 2g sodium bicarbonate into 1 lit of HEPES solution and after filtration (0.2micro) we add FBS 10%.
Yes this is been a problem for quite some time. Even the image that ATCC shows in their website are not a complete monolayer and looks like a population of more than one cell type. You can start finding gaps in the monolayer after few passages, which sometimes makes difficult for determination of virus titration. You can try with cells from old stock.
Since you do not use CO2/ bicarbonate buffered media, I assume you use Hepes. I have found from experience some cells do not grow well with this buffer. Also the comment on mycoplasma is pertinent and you should test for possible contamination.
MDCK cell line can go further into several passages and they are very strong cells compared with other types of cell culture like PHTBE cells .... If you do not use 5 % co2 you must add HEPES to the media (1/100 dilution) ..... also try to use DMEM gibco 500 ml bottle with addition of 5 ml pen/strept and 5 ml HEPES and 0.5 ml Amphotrocin B and 10% FBS ...... that is it ..... I did notice bigger size before when I used antibiotics several times to cells to retrieve them from bacterial contamination ... the cells were so weared take long time to grow and show bigger shape ... so either you do not have the correct media or have bacterial contamination or used too much antibiotics that is toxic to cells ....