Intracellular Lactate Modulation Alters Histone Modifications and CHO Cell Performance in Fed-Batch Culture

Lactate is a major byproduct of Chinese hamster ovary (CHO) cell metabolism, typically accumulating during the exponential growth phase and being consumed later during the production phase. Although commonly viewed as a waste product, recent studies suggest that lactate may play a broader role in cellular regulation. To investigate this, we developed a system to modulate intracellular lactate levels by co-expressing lactate oxidase (LOX) and catalase (CAT) in specific cellular compartments, including the cytosol, nucleus, and mitochondria. Using CHO cells secreting a bispecific antibody, this approach enabled assessment of how compartment-specific reduction of intracellular lactate influences cell performance. Reduction of nuclear lactate levels resulted in the most pronounced improvements, including approximately 40% higher viable cell density, 35%-40% increased protein titer, and reduced oxidative stress in fed-batch cultures. In contrast, reduction of mitochondrial lactate levels had minimal impact, indicating that the functional role of lactate is highly dependent on its subcellular localization. Further analysis demonstrated that intracellular lactate reduction was associated with decreased histone acetylation and histone lactylation, a recently described epigenetic modification linked to lactate metabolism. These epigenetic changes correlated with reduced markers of DNA damage and repair activity, suggesting improved genome stability. Overall, our findings indicate that lactate functions as more than a metabolic byproduct and may act as a regulatory metabolite influencing epigenetic state and cellular performance. Targeted modulation of intracellular lactate therefore represents a promising strategy to enhance productivity in CHO cell cultures.