Reversible removal and hydrodynamic phenomena in CHO microcarrier cultures

Abstract

Recent studies have been published regarding hydrodynamic phenomena in microcarrier cultures of FS-4I4 and BEK cells . 5 , 6 A frequent question regarding these results concerns their translation to other cell lines. The results for a particular cell line may depend on several factors, such as the strength and nature of the attachment between the cells and microcarriers. FS-4 cells are human diploid fibroblasts and are fully anchorage dependent. They attach very strongly to microcarriers at normal pH levels7 except during the later stage of a culture when they migrate together and form spheroids. Hydrodynamic studies with FS-4 cells were performed during the growth stage prior to spheroid formation.’-4 The results indicate that FS-4 cells are irreversibly removed from Cytodex 1 microcarriers by excessive hydrodynamic force^.^ All of the cells which remain on the microcarriers are viable and grow at a rate independent of the level of agitation. The cells in suspension are nonviable and incapable of attachment. Hydrodynamic removal of an FS-4 cell appears to leave a “footprint” which precludes secondary growth over that position. For the purposes of comparison, a short set of hydrodynamic studies was also performed with recombinant Chinese hamster ovary (CHO) cells engineered to produce gamma interferon. These CHO cells are aneuploid and, although not fully anchorage-dependent, are difficult to grow in suspension.839 CHO cells were chosen not only because they have different attachment properties than FS-4 cells, but also because of their common use in recombinant protein production. The results of the experiments with the CHO cells are reported here.