Abstract
The addition of nutrients and accumulation of metabolites in a fed-batch culture of Chinese hamster ovary (CHO) cells leads to an increase in extracellular osmolality in late stage culture. Herein, we explore the effect of osmolality on CHO cell growth, specific monoclonal antibody (mAb) productivity and glycosylation achieved with the addition of NaCl or the supplementation of a commercial feed. Although both methods lead to an increase in specific antibody productivity, they have different effects on cell growth and antibody production. Osmolality modulation using NaCl up to 470 mOsm kg−1 had a consistently positive effect on specific antibody productivity and titre. The addition of the commercial feed achieved variable results: specific mAb productivity was increased, yet cell growth rate was significantly compromised at high osmolality values. As a result, Feed C addition to 410 mOsm kg−1 was the only condition that achieved a significantly higher mAb titre compared to the control. Additionally, Feed C supplementation resulted in a significant reduction in galactosylated antibody structures. Cell volume was found to be positively correlated to osmolality; however, osmolality alone could not account for observed changes in average cell diameter without considering cell cycle variations. These results help delineate the overall effect of osmolality on titre and highlight the potentially negative effect of overfeeding on cell growth.
Highlights
Culture osmolality, cell cycle distribution and cell volume of Chinese hamster ovary (CHO) cells have all been shown to correlate with specific recombinant protein productivity, as well as with one another [1,2,3,4,5,6]
We first evaluated the effect of hyperosmolality on the specific cell growth rate and metabolic activity in cultures grown in flasks
Having explored the effect of hyperosmolality induced by feed and salt addition in the beginning of the CHO cell cultivation in flasks, we looked at a set of typical fedbatch CHO cell cultures in bioreactors
Summary
Cell cycle distribution and cell volume of Chinese hamster ovary (CHO) cells have all been shown to correlate with specific recombinant protein productivity, as well as with one another [1,2,3,4,5,6]. Other studies have reported that cell volume alone is not always sufficient to account for an increase in recombinant protein expression [14], and other factors such as cell culture phase and medium composition strongly affect specific productivity [15,16]. Cell size is determined by the rate of synthesis and uptake of molecules and their loss by secretion and degradation, which all together can vary with the level of growth factor signalling and gene expression [17,18]
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