Cellular and transcriptomic analysis of NS0 cell response during exposure to hypoxia

Mammalian cells have the ability to alter their gene expression in order to survive or adapt to a variety of environment stresses including hypoxic stress. Maintaining oxygen supply has been accepted as essential for cell survival and growth. To determine the cellular and molecular changes which take place under oxygen deprivation, an NS0 cell line producing a human-mouse chimeric antibody was cultured under hypoxic conditions (<1%). Various cellular parameters such as viability, productivity, metabolism, apoptosis and cell cycle were studied and notable changes were shown to be accompanied by changes in metabolic rates. When the cells where exposed to hypoxia for 48 h, cell growth was suppressed and cell death was detected. To better understand and explore the mechanisms underpinning these biological alterations and to identify the genes involved in the genetic reprogramming, genome-wide analyses were performed using GeneChip Mouse Genome arrays. The gene expression profiling generated by the microarray technique revealed that hypoxia, even in the early stages (12 h), induces significant changes in gene expression in NS0 cells. The primary responses to hypoxia within the cells were: (1) the up-regulation of pathways such as glycolysis that ultimately lead to alternative routes of ATP generation and increased oxygen availability; and (2) the down-regulation of genes involved in purine/pyrimidine and one carbon pool metabolisms required for DNA and RNA synthesis. By combining gene expression and physiological changes under hypoxia, it was possible to explore the mechanisms of hypoxia-induced alterations in more depth.