| Summary: | Mammalian cell cultures are nowadays adopted as industrial platforms for monoclonal antibody (mAb) manufacture. Although improving product quality and expression stability becomes predominant these days, enhancement in mAb production still remains one of the greatest challenges facing the industrial biotechnology community. One of reasons behind this is the synthesis of mAb is restricted by the decline phase occurring in the mammalian cell cultures as a result of cell death. Prolongation of culture viability via suppression of cell death appears as a potential strategy to improve mAb production and productivity. Understanding of cell death in the mammalian cell cultures is, therefore, crucial to the improvement of the strategy toward mAb production and productivity enhancement. Apoptosis, or programmed cell death, is found to be the major cause of culture viability loss in the mammalian cell cultures. It is a highly-organised physiological process of cell death that can be triggered through activation of the genetic programme underlying a signal cascade that governs particular morphological and physiological changes in response to extracellular and intracellular stimuli. In order to devise strategies to optimise degrees of apoptosis in the mammalian cell cultures, understanding of apoptosis is inevitable. However, to establish the understanding of apoptosis is an extremely challenging task given the complexity arising from the dynamic nature of apoptosis and its association with internal and external milieu, including other cellular processes and environmental conditions. This thesis presents a combined experimental and modelling approach for a study of apoptosis in GS-NS0 cell cultures, aiming to identify relevant metabolic stresses, evaluate their impact on apoptosis induction, and investigate kinetics of apoptosis in response to the identified stresses. The novelty of this study is a systemic view of apoptosis where apoptosis is studied in accordance with dynamic changes in culturing conditions, as well as cell proliferation and metabolic activities. Batch culture experiments of GS-NS0 cell line demonstrate interplay between apoptosis and other cellular processes, including cell cycle progression and metabolism. In addition, the batch cultures allow evaluating impact of metabolic stresses and culture conditions on induction of apoptosis. Fed-batch culture experiments help validate links between apoptosis and metabolic stresses as suggested based on the batch cultures, and also shed some light on feeding strategies for a delay in apoptosis induction. The first-principles mathematical model for apoptosis in the GS-NS0 cell cultures demonstrates a good reproduction of the experimental data. Model analysis reveals model characteristics through global parameter sensitivities and helps guide further model modification toward development of a predictive apoptosis mathematical model.
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