Transient ammonia stress on Chinese hamster ovary (CHO) cells yield alterations to alanine metabolism and IgG glycosylation profiles

• Published in: Biotechnology journal 2021-07, Vol.16 (7), p.e2100098-n/a
• Main Authors: Synoground, Benjamin F., McGraw, Claire E., Elliott, Kathryn S., Leuze, Christina, Roth, Jada R., Harcum, Sarah W., Sandoval, Nicholas R.
• Format: Article
• Language: English
• Subjects: alanine metabolism; ambr250; ammonia stress; Chinese hamster ovary cells; ribosome genes
• ISSN: 1860-6768; 1860-7314
• DOI: 10.1002/biot.202100098

Background Ammonia concentrations typically increase during mammalian cell cultures, mainly due to glutamine and other amino acid consumption. An early ammonia stress indicator is a metabolic shift with respect to alanine. To determine the underlying mechanisms of this metabolic shift, a Chinese hamster ovary (CHO) cell line with two distinct ages (standard and young) was cultured in parallel fed‐batch bioreactors with 0 mM or 10 mM ammonia added at 12 h. Reduced viable cell densities were observed for the stressed cells, while viability was not significantly affected. The stressed cultures had higher alanine, lactate, and glutamate accumulation. Interestingly, the ammonia concentrations were similar by Day 8.5 for all cultures. We hypothesized the ammonia was converted to alanine as a coping mechanism. Interestingly, no significant differences were observed for metabolite profiles due to cell age. Glycosylation analysis showed the ammonia stress reduced galactosylation, sialylation, and fucosylation. Transcriptome analysis of the standard‐aged cultures indicated the ammonia stress had a limited impact on the transcriptome, where few of the significant changes were directly related metabolite or glycosylation reactions. These results indicate that mechanisms used to alleviate ammonia stress are most likely controlled post‐transcriptionally, and this is where future research should focus. Parallel CHO cell cultures with two different ages were treated with or without ammonia (10 mM). Standard‐aged, ammonia‐stressed cultures had significantly reduced growth due to ammonia. Further, amino acid consumption rates, gene expression, and glycosylation of the antibody product were altered by the ammonia. It was determined that the cultures used alanine‐related synthesis reactions (ALT and GDH) to counteract the negative effects of ammonia.