Characterization of dynamic regulation in Chinese hamster ovary (CHO) cell cultures in the late exponential phase

[Display omitted] •A dynamic shift of transcriptome was found in the exponential phase of CHO cell culture.•The dynamic regulation was assessed at anti-oxidant, TCA and N-glycosylation pathways.•The gene expression is coincident with lactate shift from its accumulation to consumption.•In-culture transcriptomic changes indicate a regulation to oxidative stress.•The gene expressions suggest a homeostasis behavior to high nutrient at growth phase. Chinese hamster ovary (CHO) cells are the most commonly used host cells to produce biologics in the biopharmaceutical industry. In a batch or fed-batch process, cells grow at a relatively constant rate at the exponential growth phase, a period that is commonly assumed as a “metabolically quasi steady-state”. However, the cell culture environment, such as medium composition, does not maintain the same during this time; instead, the medium composition changes with nutrient decrease, cell density increase, and byproduct accumulation. Therefore, cellular microenvironment may respond to such process changes. This study examined the transcriptome across the late exponential growth phase of three CHO cell lines to illuminate the dynamic regulation at glycolysis, tricarboxylic acid (TCA) cycle, glycosylation, and antioxidant pathways. We found that the expression of a series of genes has a concurrent shift around 91 h, coincident with lactate shift from its accumulation to consumption. The gene expressions altogether suggest a homeostasis behavior before the 91 h, presumably a response to the high abundance of nutrients at the exponential growth phase.