The effect of hyperosmotic pressure on antibody production and gene expression in the GS-NS0 cell line

It has been widely reported that metabolism, cell growth, cell density, product secretion and specific antibody productivity in mammalian cells are strongly affected by osmotic conditions. Previous studies have shown that hyper-osmotic pressure suppresses cell growth while enhancing the productivity of individual cells, but the effect of these two changes does not result in an increase in final product concentration in the culture. An improved understanding of the basic cellular processes of a GS-NSO mammalian cell culture system would assist in the design of a more efficient mammalian cell culture system and in further optimization of production processes. In this study, various properties of mammalian culture systems, such as productivity, cell viability, metabolism, ion balance and the genes regulated during the culture of the GS-NS0 system under osmotic pressure of iso- (290 mOsm/kg) and hyper- (450 mOsm/kg) osmolarity have been investigated, and we demonstrate that there is a decrease in the growth rate and an increase in specific production rate of hyperosmotic cultures as compared with isoosmotic cultures. Furthermore, differences between iso- and hyper-osmotic cultures have been identified in calcium accumulation and metabolism of NH₄⁺, glucose and lactate. Analysis of gene expression reveals regulation of over 600 genes that are implicated in processes known to be affected by changes in osmotic pressure, such as ion transport, accumulation of osmolytes, cell cycle distribution, proliferation, cytoskeletal organization and cell metabolism.