Transient Transfection Induces Early Cytosolic Calcium Signaling in CHO-K1 Cells

2002 
For the controlled production of recombinant proteins in mammalian cells by using transient transfection methods, it may be desirable not only to manipulate, but also to early diagnose success and extent of expression. Here, we applied laser scanning confocal microscopy to on-line monitor second messenger Ca2+ signaling in Chinese hamster ovary (CHO-K1) cells during and after transfection. The calcium phosphate / DNA coprecipitation technique was our method of choice, because it is easily applicable for both mini and large scale transfection. In CHO cells we observed a strong Ca2+ response already a few minutes after addition of the transfecting solution. Virtually all CHO cells exhibited asynchronous cytosolic Ca2+ oscillations 3 hours after transfection onset. Somewhat surprisingly, we observed that the glycerol shock commonly used to enhance the productivity in CHO host cells at the same time “soothed” their Ca2+ signaling, reducing the oscillations. Time lapse studies revealed shock induced morphological changes in the endoplasmic reticulum of CHO cells. Our finding points to intracellular Ca2+ signaling as a possible early indicator of the transient transfection fate of CHO-K1 cells.
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