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Hubalek S, Melke J, Pawlica P, Post MJ, Moutsatsou P. Non-ammoniagenic proliferation and differentiation media for cultivated adipose tissue. Front Bioeng Biotechnol 2023; 11:1202165. [PMID: 37555077 PMCID: PMC10405928 DOI: 10.3389/fbioe.2023.1202165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 07/10/2023] [Indexed: 08/10/2023] Open
Abstract
Ammonia (Amm), and its aqueous solved state, ammonium, which is produced from glutamine (Gln) metabolism, is a known inhibitor of stem cell proliferation in vitro. In the context of cultivated beef, primary bovine fibro-adipogenic progenitor cells (FAPs) need to be grown and differentiated for several weeks in vitro for the production of cultivated fat. In this study, the ammonium sensitivity of these cells was investigated by introducing ammonium chloride, which was found to inhibit their proliferation when above 5 mM and their adipogenic differentiation when above 2 mM. Novel serum-free proliferation and differentiation media were hence developed with the aim to suppress Amm production during expansion and adipogenesis. Glutamine substitutes, such as a-ketoglutarate (aKG), glutamate (Glt) and pyruvate (Pyr) were investigated. It was found that aKG based proliferation medium (PM) was the most effective in promoting and maintaining FAPs growth over several passages while the specific Amm production rate was reduced more than 5-fold. In terms of differentiation capacity, the substitution of glucose (Gluc) and Gln with galactose (Gal) and Pyr was shown to be the most effective in promoting FAPs differentiation into mature adipocytes, resulting in over 2-fold increase of fat volume per cell, while suppressing Amm production. Our findings suggest that FAPs do not require Gln as an essential nutrient but, on the contrary, possess all the necessary metabolic pathways to proliferate and subsequently differentiate in a Gln-free medium, resulting in decreased Amm production rates and seemingly synthesising glutamine de novo. These findings are important for prolonging the lifespan of culture medium, allowing for reduced costs and process interventions.
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Affiliation(s)
- S. Hubalek
- Mosa Meat BV, Maastricht, Netherlands
- Department of Physiology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
- CARIM, School of Cardiovascular Diseases, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
| | - J. Melke
- Mosa Meat BV, Maastricht, Netherlands
| | | | - M. J. Post
- Mosa Meat BV, Maastricht, Netherlands
- Department of Physiology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
- CARIM, School of Cardiovascular Diseases, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
| | - P. Moutsatsou
- Mosa Meat BV, Maastricht, Netherlands
- Department of Physiology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
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2
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Pérez-Fernández BA, Fernandez-de-Cossio-Diaz J, Boggiano T, León K, Mulet R. In-silico media optimization for continuous cultures using genome scale metabolic networks: The case of CHO-K1. Biotechnol Bioeng 2021; 118:1884-1897. [PMID: 33554345 DOI: 10.1002/bit.27704] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/18/2020] [Accepted: 01/21/2021] [Indexed: 01/12/2023]
Abstract
The cell culture is the central piece of a biotechnological industrial process. It includes upstream (e.g. media preparation, fixed costs, etc.) and downstream steps (e.g. product purification, waste disposal, etc.). In the continuous mode of cell culture, a constant flow of fresh media replaces culture fluid until the system reaches a steady state. This steady state is the standard operation mode which, under very general conditions, is a function of the ratio between the cell density and the dilution rate and depends on the media supplied to the culture. To optimize the production process it is widely accepted that the concentration of the metabolites in this media should be carefully tuned. A poor media may not provide enough nutrients to the culture, while a media too rich in nutrients may be a waste of resources because, either the cells do not use all of the available nutrients, or worse, they over-consume them producing toxic byproducts. In this study, we show how an in-silico study of a genome scale metabolic network coupled to the dynamics of a chemostat could guide the strategy to optimize the media to be used in a continuous process. Given a known media we model the concentrations of the cells in a chemostat as a function of the dilution rate. Then, we cast the problem of optimizing the production process within a linear programming framework in which the goal is to minimize the cost of the media keeping fixed the cell concentration for a given dilution rate in the chemostat. We evaluate our results in two metabolic models: first a simplified model of mammalian cell metabolism, and then in a realistic genome-scale metabolic network of mammalian cells, the Chinese hamster ovary cell line. We explore the latter in more detail given specific meaning to the predictions of the concentrations of several metabolites.
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Affiliation(s)
- Bárbara A Pérez-Fernández
- Group of Complex Systems and Statistical Physics, Department of Theoretical Physics, Physics Faculty, University of Havana, Havana, Cuba
| | - Jorge Fernandez-de-Cossio-Diaz
- Group of Complex Systems and Statistical Physics, Department of Theoretical Physics, Physics Faculty, University of Havana, Havana, Cuba.,Systems Biology Department, Center of Molecular Immunology, Havana, Cuba
| | - Tammy Boggiano
- Systems Biology Department, Center of Molecular Immunology, Havana, Cuba
| | - Kalet León
- Systems Biology Department, Center of Molecular Immunology, Havana, Cuba
| | - Roberto Mulet
- Group of Complex Systems and Statistical Physics, Department of Theoretical Physics, Physics Faculty, University of Havana, Havana, Cuba
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3
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Maralingannavar V, Parmar D, Panchagnula V, Gadgil M. Superfluous glutamine synthetase activity in Chinese Hamster Ovary cells selected under glutamine limitation is growth limiting in glutamine-replete conditions and can be inhibited by serine. Biotechnol Prog 2019; 35:e2856. [PMID: 31148368 DOI: 10.1002/btpr.2856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 05/08/2019] [Accepted: 05/25/2019] [Indexed: 11/08/2022]
Abstract
Passaging and expansion of animal cells in lean maintenance medium could result in periods of limitation of some nutrients. Over time, such stresses could possibly result in selection of cells with metabolic changes and contribute to heterogeneity. Here, we investigate whether selection of Chinese Hamster Ovary (CHO) cells under glutamine limitation results in changes in growth under glutamine-replete conditions. In glutamine-limiting medium, compared to control cells passaged in glutamine-rich medium, the selected cells showed higher glutamine synthetase (GS) activity and attained a higher peak viable cell density (PVCD). Surprisingly, in glutamine-replete conditions, selected cells still showed a higher GS activity but a lower PVCD. We show that in glutamine-replete medium, PVCD of selected cells was restored on (a) inhibition of GS activity with methionine sulfoximine, (b) supplementation of aspartate-without affecting GS activity, and (c) supplementation of serine, which is reported to inhibit GS in vitro. Consistent with the reported effect of serine, inhibition of GS activity was observed upon serine supplementation along with reduced growth of cells under glutamine-limiting conditions. The latter observation is important for the design of glutamine-free culture medium and feed used for GS-CHO and GS-NS0. In summary, we show that CHO cells selected under glutamine limitation have superfluous GS activity in glutamine-replete medium, which negatively affects their PVCD. This may be due to its effect on availability of aspartate which was the limiting nutrient for the growth of selected cells in glutamine-replete conditions.
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Affiliation(s)
- Vishwanathgouda Maralingannavar
- Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Pune, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory Campus, Ghaziabad, Uttar Pradesh, India
| | - Dharmeshkumar Parmar
- Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Pune, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory Campus, Ghaziabad, Uttar Pradesh, India
| | - Venkateswarlu Panchagnula
- Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Pune, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory Campus, Ghaziabad, Uttar Pradesh, India
| | - Mugdha Gadgil
- Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Pune, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory Campus, Ghaziabad, Uttar Pradesh, India
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4
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Karengera E, Robotham A, Kelly J, Durocher Y, De Crescenzo G, Henry O. Concomitant reduction of lactate and ammonia accumulation in fed-batch cultures: Impact on glycoprotein production and quality. Biotechnol Prog 2018; 34:494-504. [DOI: 10.1002/btpr.2607] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 10/24/2017] [Indexed: 01/15/2023]
Affiliation(s)
- Eric Karengera
- Department of Chemical Engineering; École Polytechnique de Montréal, P.O. Box 6079, succ. Centre-Ville; Montréal Quebec H3C 3A7 Canada
| | - Anna Robotham
- Human Health Therapeutics Portfolio, National Research Council Canada; Ottawa Ontario Canada
| | - John Kelly
- Human Health Therapeutics Portfolio, National Research Council Canada; Ottawa Ontario Canada
| | - Yves Durocher
- Human Health Therapeutics Portfolio, National Research Council Canada; Montréal Quebec Canada
| | - Gregory De Crescenzo
- Department of Chemical Engineering; École Polytechnique de Montréal, P.O. Box 6079, succ. Centre-Ville; Montréal Quebec H3C 3A7 Canada
| | - Olivier Henry
- Department of Chemical Engineering; École Polytechnique de Montréal, P.O. Box 6079, succ. Centre-Ville; Montréal Quebec H3C 3A7 Canada
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5
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Impact of Adenovirus infection in host cell metabolism evaluated by (1)H-NMR spectroscopy. J Biotechnol 2016; 231:16-23. [PMID: 27215342 DOI: 10.1016/j.jbiotec.2016.05.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 05/12/2016] [Accepted: 05/19/2016] [Indexed: 12/22/2022]
Abstract
Adenovirus-based vectors are powerful vehicles for gene transfer applications in vaccination and gene therapy. Although highly exploited in the clinical setting, key aspects of the adenovirus biology are still not well understood, in particular the subversion of host cell metabolism during viral infection and replication. The aim of this work was to gain insights on the metabolism of two human cell lines (HEK293 and an amniocyte-derived cell line, 1G3) after infection with an adenovirus serotype 5 vector (AdV5). In order to profile metabolic alterations, we used (1)H-NMR spectroscopy, which allowed the quantification of 35 metabolites in cell culture supernatants with low sample preparation and in a relatively short time. Significant differences between both cell lines in non-infected cultures were identified, namely in glutamine and acetate metabolism, as well as by-product secretion. The main response to AdV5 infection was an increase in glucose consumption and lactate production rates. Moreover, cultures performed with or without glutamine supplementation confirmed the exhaustion of this amino acid as one of the main causes of lower AdV5 production at high cell densities (10- and 1.5-fold less specific yields in HEK293 and 1G3 cells, respectively), and highlighted different degrees of glutamine dependency of adenovirus replication in each cell line. The observed metabolic alterations associated with AdV5 infection and specificity of the host cell line can be useful for targeted bioprocess optimization.
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6
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Effect of glutamine substitution by TCA cycle intermediates on the production and sialylation of Fc-fusion protein in Chinese hamster ovary cell culture. J Biotechnol 2014; 180:23-9. [DOI: 10.1016/j.jbiotec.2014.04.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 11/16/2022]
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7
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Marin-Valencia I, Yang C, Mashimo T, Cho S, Baek H, Yang XL, Rajagopalan KN, Maddie M, Vemireddy V, Zhao Z, Cai L, Good L, Tu BP, Hatanpaa KJ, Mickey BE, Matés JM, Pascual JM, Maher EA, Malloy CR, Deberardinis RJ, Bachoo RM. Analysis of tumor metabolism reveals mitochondrial glucose oxidation in genetically diverse human glioblastomas in the mouse brain in vivo. Cell Metab 2012; 15:827-37. [PMID: 22682223 PMCID: PMC3372870 DOI: 10.1016/j.cmet.2012.05.001] [Citation(s) in RCA: 409] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 02/26/2012] [Accepted: 05/01/2012] [Indexed: 12/21/2022]
Abstract
Dysregulated metabolism is a hallmark of cancer cell lines, but little is known about the fate of glucose and other nutrients in tumors growing in their native microenvironment. To study tumor metabolism in vivo, we used an orthotopic mouse model of primary human glioblastoma (GBM). We infused (13)C-labeled nutrients into mice bearing three independent GBM lines, each with a distinct set of mutations. All three lines displayed glycolysis, as expected for aggressive tumors. They also displayed unexpected metabolic complexity, oxidizing glucose via pyruvate dehydrogenase and the citric acid cycle, and using glucose to supply anaplerosis and other biosynthetic activities. Comparing the tumors to surrounding brain revealed obvious metabolic differences, notably the accumulation of a large glutamine pool within the tumors. Many of these same activities were conserved in cells cultured ex vivo from the tumors. Thus GBM cells utilize mitochondrial glucose oxidation during aggressive tumor growth in vivo.
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Affiliation(s)
- Isaac Marin-Valencia
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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8
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Janke R, Genzel Y, Händel N, Wahl A, Reichl U. Metabolic adaptation of MDCK cells to different growth conditions: effects on catalytic activities of central metabolic enzymes. Biotechnol Bioeng 2011; 108:2691-704. [PMID: 21618469 DOI: 10.1002/bit.23215] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 04/18/2011] [Accepted: 05/10/2011] [Indexed: 01/01/2023]
Abstract
Lactate and ammonia are the most important waste products of central carbon metabolism in mammalian cell cultures. In particular during batch and fed-batch cultivations these toxic by-products are excreted into the medium in large amounts, and not only affect cell viability and productivity but often also prevent growth to high cell densities. The most promising approach to overcome such a metabolic imbalance is the replacement of one or several components in the culture medium. It has been previously shown that pyruvate can be substituted for glutamine in cultures of adherent Madin-Darby canine kidney (MDCK) cells. As a consequence, the cells not only released no ammonia but glucose consumption and lactate production were also reduced significantly. In this work, the impact of media changes on glucose and glutamine metabolism was further elucidated by using a high-throughput platform for enzyme activity measurements of mammalian cells. Adherent MDCK cells were grown to stationary and exponential phase in six-well plates in serum-containing GMEM supplemented with glutamine or pyruvate. A total number of 28 key metabolic enzyme activities of cell extracts were analyzed. The overall activity of the pentose phosphate pathway was up-regulated during exponential cell growth in pyruvate-containing medium suggesting that more glucose-6-phosphate was channeled into the oxidative branch. Furthermore, the anaplerotic enzymes pyruvate carboxylase and pyruvate dehydrogenase showed higher cell specific activities with pyruvate. An increase in cell specific activity was also found for NAD(+)-dependent isocitrate dehydrogenase, glutamate dehydrogenase, and glutamine synthetase in MDCK cells grown with pyruvate. It can be assumed that the increase in enzyme activities was required to compensate for the energy demand and to replenish the glutamine pool. On the other hand, the activities of glutaminolytic enzymes (e.g., alanine and aspartate transaminase) were decreased in cells grown with pyruvate, which seems to be related to a decreased glutamine metabolism.
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Affiliation(s)
- R Janke
- Max Planck Institute for Dynamics of Complex Technical Systems, Bioprocess Engineering Group, Sandtorstraße 1, 39106 Magdeburg, Germany.
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9
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Nilsang S, Nehru V, Plieva FM, Nandakumar KS, Rakshit SK, Holmdahl R, Mattiasson B, Kumar A. Three-dimensional culture for monoclonal antibody production by hybridoma cells immobilized in macroporous gel particles. Biotechnol Prog 2009; 24:1122-31. [PMID: 19194922 DOI: 10.1002/btpr.28] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cell proliferation and long-term production of monoclonal antibody IgG(2b) by M2139 hybridoma cells immobilized in macroporous gel particles (MGPs) in packed-bed reactor were studied for a period of 60 days. The MGPs were made of supermacroporous gels produced in frozen conditions from crosslinked polyacrylamide and modified with gelatin which were housed in special plastic carriers (7 x 9 mm(2)). Cells were trapped in the interior part of MGPs by attaching to the void space of the gel matrix as three-dimensional (3D) cultivation using gelatin as a substrate layer. Optimizing productivity by hybridoma cell relies on understanding regulation of antibody production. In this study, the behavior of M2139 cells in two-dimensional cultures on multiwell plate surfaces was also investigated. The effect of three different medium such as basal medium Dulbecco's modified Eagle's medium (D-MEM) containing L-glutamine or L-glutamine + 2 mM alpha-ketoglutarate or L-alanyl-glutamine (GlutaMAXtrade mark) was studied prior to its use in 3D cultivation. The kinetics of cell growth in basal medium containing L-glutamine + alpha-ketoglutarate was similar to cells grown on GlutaMAX containing medium, whereas D-MEM containing L-glutamine showed lower productivity. With the maximal viable cell density (6.85 x 10(6) cells mL(-1)) and highest specific mAb production rate (3.9 mug mL(-1) 10(-4) viable cell day(-1)), D-MEM-GlutaMAX was further selected for 3D cultivation. Cells in MGPs were able to grow and secrete antibody for 30 days in packed-bed batch reactor, before a fresh medium reservoir was replaced. After being supplied with fresh medium, cells again showed continuous growth for another 30 days with mAb production efficiency of 50%. These results demonstrate that MGPs can be used efficiently as supporting carrier for long-term monoclonal antibody production.
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Affiliation(s)
- Suthasinee Nilsang
- Dept of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden
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10
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Slivac I, Gaurina Srcek V, Radosević K, Porobić I, Bilić K, Fumić K, Kniewald Z. Growth characteristics of channel catfish ovary cells-influence of glucose and glutamine. Cytotechnology 2008; 57:273-8. [PMID: 19003184 DOI: 10.1007/s10616-008-9171-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 09/18/2008] [Indexed: 11/24/2022] Open
Abstract
The growth characteristics and influence of glucose and glutamine on the growth and maintenance of channel catfish ovary (CCO) cells were investigated. Besides glutamine, amino acids threonine, arginine, methionine and serine were found to be essential for CCO cell growth. In the glucose-free medium, glutamine is utilized as energy source and no cell growth limitation was observed. However, the lack of glutamine in culture medium did not stimulate CCO cells to efficient glucose consumption. When both glucose and glutamine were deficient, cell growth was also observed suggesting no rigorous nutritional requirements. Obtained results are useful for further understanding of culture processes using CCO cells.
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Affiliation(s)
- Igor Slivac
- Laboratory of Cell Culture Technology, Application and Biotransformation, Faculty of Food Technology and Biotechnology, University of Zagreb, 6 Pierotti St., 10000, Zagreb, Croatia
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11
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Wahl A, Sidorenko Y, Dauner M, Genzel Y, Reichl U. Metabolic flux model for an anchorage-dependent MDCK cell line: characteristic growth phases and minimum substrate consumption flux distribution. Biotechnol Bioeng 2008; 101:135-52. [PMID: 18646224 DOI: 10.1002/bit.21873] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Up to now cell-culture based vaccine production processes only reach low productivities. The reasons are: (i) slow cell growth and (ii) low cell concentrations. To address these shortcomings, a quantitative analysis of the process conditions, especially the cell growth and the metabolic capabilities of the host cell line is required. For this purpose a MDCK cell based influenza vaccine production process was investigated. With a segregated growth model four distinct cell growth phases are distinguished in the batch process. In the first phase the cells attach to the surface of the microcarriers and show low metabolic activity. The second phase is characterized by exponential cell growth. In the third phase, preceded by a change in oxygen consumption, contact inhibition leads to a decrease in cell growth. Finally, the last phase before infection shows no further increase in cell numbers. To gain insight into the metabolic activity during these phases, a detailed metabolic model of MDCK cell was developed based on genome information and experimental analysis. The MDCK model was also used to calculate a theoretical flux distribution representing an optimized cell that only consumes a minimum of carbon sources. Comparing this minimum substrate consumption flux distribution to the fluxes estimated from experiments unveiled high overflow metabolism under the applied process conditions.
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Affiliation(s)
- Aljoscha Wahl
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany.
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12
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Genzel Y, Ritter JB, König S, Alt R, Reichl U. Substitution of Glutamine by Pyruvate To Reduce Ammonia Formation and Growth Inhibition of Mammalian Cells. Biotechnol Prog 2008; 21:58-69. [PMID: 15903241 DOI: 10.1021/bp049827d] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In mammalian cell culture technology glutamine is required for biomass synthesis and as a major energy source together with glucose. Different pathways for glutamine metabolism are possible, resulting in different energy output and ammonia release. The accumulation of ammonia in the medium can limit cell growth and product formation. Therefore, numerous ideas to reduce ammonia concentration in cultivation broths have been developed. Here we present new aspects on the energy metabolism of mammalian cells. The replacement of glutamine (2 mM) by pyruvate (10 mM) supported cell growth without adaptation for at least 19 passages without reduction in growth rate of different adherent commercial cell lines (MDCK, BHK21, CHO-K1) in serum-containing and serum-free media. The changes in metabolism of MDCK cells due to pyruvate uptake instead of glutamine were investigated in detail (on the amino acid level) for an influenza vaccine production process in large-scale microcarrier culture. In addition, metabolite profiles from variations of this new medium formulation (1-10 mM pyruvate) were compared for MDCK cell growth in roller bottles. Even at very low levels of pyruvate (1 mM) MDCK cells grew to confluency without glutamine and accumulation of ammonia. Also glucose uptake was reduced, which resulted in lower lactate production. However, pyruvate and glutamine were both metabolized when present together. Amino acid profiles from the cell growth phase for pyruvate medium showed a reduced uptake of serine, cysteine, and methionine, an increased uptake of leucine and isoleucine and a higher release of glycine compared to glutamine medium. After virus infection completely different profiles were found for essential and nonessential amino acids.
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Affiliation(s)
- Yvonne Genzel
- Max-Planck-Institute for Dynamics of Complex Technical Systems, Magdeburg, Sandtorstr. 1, 39106 Magdeburg, Germany.
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13
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Nilsang S, Kumar A, Rakshit SK. Effect of alpha-ketoglutarate on monoclonal antibody production of hybridoma cell lines in serum-free and serum-containing medium. Appl Biochem Biotechnol 2008; 151:489-501. [PMID: 18696264 DOI: 10.1007/s12010-008-8225-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 03/10/2008] [Indexed: 12/20/2022]
Abstract
Process development and optimization for increase population growth and protein productivity in mammalian cell culture have been studied for many years. In this study, the behavior of hybridoma cells was investigated using six-well micro-titer plate systems with a working volume of 4 ml. Mouse hybridoma cell lines D2 and 2C83G2 were seeded in serum-free and serum-containing media and cultured for 8 days. alpha-Ketoglutarate is an integral component of the tricarboxylic acid (TCA) cycle and is produced from glutamine via glutamate. To study its effect on cell growth, metabolism, and monoclonal antibody (mAb) production, 2 mM alpha-ketoglutarate (pH 7.2) was added in both media at the beginning of the cultivation and in another set after 72 h. High cell density was observed in D2 cell culturing in serum-free medium, while 2C83G2 cell line showed high cell density in serum-containing medium. However, both cell lines cultured in serum-free medium gave viability above 70% when grown for 8 days. The supplement of 2 mM alpha-ketoglutarate supported cell growth and mAb production of both hybridoma cell lines in serum-free and serum-containing medium. The addition of alpha-ketoglutarate at the beginning of the batch cultivation gave better result in cell growth and mAb production as compared to alpha-ketoglutarate supplementation after 72 h. However, addition after 72 h was better than no addition at all. This indicates that alpha-ketoglutarate have a positive effect on production and release of antibody.
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Affiliation(s)
- Suthasinee Nilsang
- Department of Food Engineering and Bioprocess Technology, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani, Thailand
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15
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Doepel L, Lessard M, Gagnon N, Lobley GE, Bernier JF, Dubreuil P, Lapierre H. Effect of Postruminal Glutamine Supplementation on Immune Response and Milk Production in Dairy Cows. J Dairy Sci 2006; 89:3107-21. [PMID: 16840628 DOI: 10.3168/jds.s0022-0302(06)72585-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Seventeen multiparous Holstein cows were used to examine the effect of an increased duodenal supply of Gln on immune function and production. Cows received continuous abomasal infusions of water (control: n = 8) or 300 g/d of Gln (n = 9) for 21 d starting within 48 h of calving. There were nonsignificant increases in milk and milk protein yields in response to Gln supplementation. Glutamine treatment had no effect on plasma glucose, nonesterified fatty acids (NEFA), or beta-hydroxybutyrate (BHBA) concentrations but did tend to increase plasma urea N concentration. The Gln treatment resulted in an increase of 108 microM in the plasma Gln concentration. Total essential AA concentrations decreased with the Gln treatment, whereas total nonessential AA concentrations were unaffected. T Lymphocyte proliferation did not differ between the control and Gln-treated cows. Treatment had no effect on the relative abundance of CD8 T cells but did increase the abundance of CD4 T cells. Cytokine production, as measured by IFN-gamma concentration determined in vitro in concanavalin-A-stimulated peripheral blood mononuclear cells, was similar between the treatments. Over the first 3 wk following calving, Gln supplementation had limited effects on milk production, metabolic parameters, and immune function.
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Affiliation(s)
- L Doepel
- Département des Sciences Animales, Université Laval, Ste-Foy, Quebec, Canada, G1K 7P4
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16
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Maranga L, Goochee CF. Metabolism of PER.C6 cells cultivated under fed-batch conditions at low glucose and glutamine levels. Biotechnol Bioeng 2006; 94:139-50. [PMID: 16523524 DOI: 10.1002/bit.20890] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This is the first study to examine PER.C6 cell glucose/energy and glutamine metabolism with fed-batch cultures at controlled low glutamine, low glucose, and simultaneous low glucose and low glutamine levels. PER.C6(TM) cell metabolism was investigated in serum-free suspension bioreactors at two-liter scale. Control of glucose and/or glutamine concentrations had a significant effect on cellular metabolism leading to an increased efficiency of nutrient utilization, altered byproduct synthesis, while having no effect on cell growth rate. Cultivating cells at a controlled glutamine concentration of 0.25 mM reduced q(Gln) and q(NH(4)(+)) by approximately 30%, q(Ala) 85%, and q(NEAA) 50%. The fed-batch control of glutamine also reduced the overall accumulation of ammonium ion by approximately 50% by minimizing the spontaneous chemical degradation of glutamine. No major impact upon glucose/energy metabolism was observed. Cultivating cells at a glucose concentration of 0.5 mM reduced q(Glc) about 50% and eliminated lactate accumulation. Cells exhibited a fully oxidative metabolism with Y(O(2)/Glc) of approximately 6 mol/mol. However, despite no increase in q(Gln), an increased ammonium ion accumulation and Y(NH(4)(+)/Gln) were also observed. Effective control of lactate and ammonium ion accumulation by PER.C6 cells was achieved using fed-batch with simultaneously controlled glucose and glutamine. A fully oxidative glucose metabolism and a complete elimination of lactate production were obtained. The q(Gln) value was again reduced and, despite an increased q(NH(4)(+)) compared with batch culture, ammonium ion levels were typically lower than corresponding ones in batch cultures, and the accumulation of non-essential amino acids (NEAA) was reduced about 50%. In conclusion, this study shows that PER.C6 cell metabolism can be confined to a state with improved efficiencies of nutrient utilization by cultivating cells in fed-batch at millimolar controlled levels of glucose and glutamine. In addition, PER.C6 cells fall into a minority category of mammalian cell lines for which glutamine plays a minor role in energy metabolism.
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Affiliation(s)
- Luis Maranga
- Fermentation and Cell Culture, Bioprocess R&D, Merck Research Laboratories, Merck & Co., Inc., 770 Sumneytown Pike, WP17-201 P.O. Box 4, West Point, Pennsylvania 19486, USA.
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Marchesi C, Dall'Asta V, Rotoli BM, Bianchi MG, Maggini C, Gazzola GC, Bussolati O. Chlorpromazine, clozapine and olanzapine inhibit anionic amino acid transport in cultured human fibroblasts. Amino Acids 2006; 31:93-9. [PMID: 16699818 DOI: 10.1007/s00726-006-0312-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Accepted: 01/09/2006] [Indexed: 12/22/2022]
Abstract
We report here that chlorpromazine, a first generation antipsychotic drug, inhibits anionic amino acid transport mediated by system X(-) (AG) (EAAT transporters) in cultured human fibroblasts. With 30 microM chlorpromazine, transport inhibition is detectable after 3 h of treatment, maximal after 48 h (>60%), and referable to a decrease in V(max). Chlorpromazine effect is not dependent upon changes of membrane potential and is selective for system X(-) (AG) since transport systems A and y(+) are not affected. Among antipsychotic drugs, the inhibitory effect of chlorpromazine is shared by two dibenzodiazepines, clozapine and olanzapine, while other compounds, such as risperidon, zuclopentixol, sertindol and haloperidol, are not effective. Transport inhibition by clozapine and olanzapine, but not by chlorpromazine, is reversible, suggesting that the mechanisms involved are distinct. These results indicate that a subset of antipsychotic drugs inhibits EAAT transporters in non-nervous tissues and prompt further investigation on possible alterations of glutamate transport in peripheral tissues of schizophrenic patients.
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Affiliation(s)
- C Marchesi
- Unit of Psychiatry, Department of Neurosciences, University of Parma, Parma, Italy
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18
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Chen J, Sun X, Zhang Y. Growth and metabolism of marine fish Chinook salmon embryo cells: response to lack of glucose and glutamine. Biotechnol Lett 2005; 27:395-401. [PMID: 15834804 DOI: 10.1007/s10529-005-1774-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2004] [Accepted: 01/25/2005] [Indexed: 11/30/2022]
Abstract
A peculiar phenomenon, differing from the response of mammalian cells, occurred when Chinook salmon embryo (CHSE) cells were passaged in the medium lacking of both glucose and glutamine. To elucidate metabolic mechanism of CHSE cells, the metabolism parameters, key metabolic enzymes, and ATP levels were measured at different glucose and glutamine concentrations. In the glutamine-free culture, hexokinase activity kept constant, and lactate dehydrogenase (LDH) activity decreased. This indicated that lack of glutamine did not expedite glucose consumption but made it shift to lower lactate production and more efficient energy metabolism. The results coincided with the experimental results of unaltered specific glucose consumption rate and decreased yield coefficients of lactate to glucose. In the glucose-free culture, simultaneous increase of glutaminase activity and of specific ammonia production rate suggested an increased flux into the glutaminolysis pathway, and increases of both glutamate dehydrogenase activity and yield coefficient of ammonia to glutamine showed an increased flux into deamination pathway. However, when glucose and glutamine were both lacking, the specific consumption rates of most of amino acids increased markedly, together with decrease of LDH activity, indicating that pyruvate derived from amino acids, away from lactate production, remedied energy deficiency. When both glucose and glutamine were absent, intracellular ATP contents and the energy charge remained virtually unaltered.
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Affiliation(s)
- Juxing Chen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
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19
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Genzel Y, Behrendt I, König S, Sann H, Reichl U. Metabolism of MDCK cells during cell growth and influenza virus production in large-scale microcarrier culture. Vaccine 2004; 22:2202-8. [PMID: 15149778 DOI: 10.1016/j.vaccine.2003.11.041] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 11/05/2003] [Accepted: 11/20/2003] [Indexed: 11/28/2022]
Abstract
The production of equine influenza in Madin-Darby canine kidney (MDCK) cells in large-scale microcarrier culture is described with detailed on- and off-line analytical data during cell growth and virus replication. Metabolite concentration profiles for glucose, glutamine, lactate and ammonium are shown. Lactate and ammonium concentrations were always below inhibiting levels. Concentration profiles for essential and non-essential amino acids of the cell culture medium are discussed. During cell growth proline was released into the medium with a significant rate while two amino acids, serine and methionine were almost depleted. After infection, virus titer increased after a delay of 10-16 h whereas first changes in amino acid metabolism could be observed within 4h post-infection. Here, glutamate and aspartate increase correlated to virus release kinetics, indicating cell disruption and apoptosis. Starting with a moi of 0.025 resulted in a maximum virus yield of 2.4 log HA/100 microl at 44 h post-infection.
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Affiliation(s)
- Y Genzel
- Max-Planck-Institute for Dynamics of Complex Technical Systems, Magdeburg, Sandtorstr. 1, 39106 Magdeburg, Germany.
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Nadeau I, Sabatié J, Koehl M, Perrier M, Kamen A. Human 293 cell metabolism in low glutamine-supplied culture: interpretation of metabolic changes through metabolic flux analysis. Metab Eng 2000; 2:277-92. [PMID: 11120640 DOI: 10.1006/mben.2000.0152] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Metabolic flux analysis is a useful tool to analyze cell metabolism. In this study, we report the use of a metabolic model with 34 fluxes to study the 293 cell, in order to improve its growth capacity in a DMEM/F12 medium. A batch, fed-batch with glutamine feeding, fed-batch with essential amino acids, and finally a fed-batch experiment with both essential and nonessential amino acids were compared. The fed-batch with glutamine led to a maximum cell density of 2.4x10(6) cells/ml compared to 1.8x10(6) cells/ml achieved in a batch mode. In this fed-batch with glutamine, it was also found that 2.5 mM ammonia was produced compared to the batch which had a final ammonia concentration of 1 mM. Ammonia was found to be growth inhibiting for this cell line at a concentration starting at 1 mM. During the fed-batch with glutamine, the flux analysis shows that a majority of amino acid fluxes and Kreb's cycle fluxes, except for glutamine flux, are decreased. This observation led to the conclusion that the main nutrient used is glutamine and that during the batch there is an overflow in the Kreb's cycle. Thus, a fed-batch with glutamine permits a better utilization of this nutrient. A fed-batch with essential amino acid without glutamine was also assayed in order to reduce ammonia production. The maximum cell density was increased further to 3x10(6) cells/ml and ammonia production was reduced below 1 mM. Flux analysis shows that the cells could adapt to a medium with low glutamine by increasing the amino acid fluxes toward the Kreb's cycle. Adding nonessential amino acids during this feeding strategy did not improve growth further and the nonessential amino acids accumulated in the medium.
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Affiliation(s)
- I Nadeau
- Institut de Recherche en Biotechnologie, CNRC, 6100 avenue Royalmount, Montréal, Québec, H4P 2R2, Canada
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22
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23
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Schneider M, Alaoui ME, Stockar UV, Marison IW. Batch cultures of a hybridoma cell line performed with in situ ammonia removal. Enzyme Microb Technol 1997. [DOI: 10.1016/s0141-0229(96)00122-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Franchi-Gazzola R, Visigalli R, Bussolati O, Gazzola GC. Involvement of protein kinase Cepsilon in the stimulation of anionic amino acid transport in cultured human fibroblasts. J Biol Chem 1996; 271:26124-30. [PMID: 8824256 DOI: 10.1074/jbc.271.42.26124] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Protein kinase C (PKC) activation stimulates transport system X-AG for anionic amino acids in cultured human fibroblasts (Franchi-Gazzola, R., Visigalli, R., Bussolati, O., and Gazzola, G. C. (1994) FEBS Lett. 352, 109-112). To identify which PKC isoform is responsible for this effect, aspartate transport through system X-AG, PKC activity, and the subcellular distribution of PKC isoforms have been studied before and after treatment with phorbol 12, 13-dibutyrate (PDBu) in fibroblasts maintained at low serum for 1 (control cells) or 7 days (quiescent cells). In control cells aspartate transport and PKC activity in the particulate fraction were stimulated by short term PDBu treatment; both stimulatory effects were down-regulated by a prolonged exposure to the phorbol. In contrast, in quiescent cells aspartate transport and particulate PKC activity were higher than control under basal conditions, unaffected by a short term PDBu treatment, and lowered by a prolonged incubation with the phorbol. In both control and quiescent cells a short term PDBu treatment modified PKCalpha distribution, increasing its membrane-associated fraction. PKCdelta was mostly in the soluble fraction and scarcely sensitive to PDBu. A brief exposure to PDBu increased membrane-associated PKCepsilon in control but not in quiescent cells. In these cells epsilon isoform was found exclusively in the particulate fraction even in PDBu-untreated cells. A prolonged PDBu treatment caused a partial down-regulation of membrane-associated PKCepsilon in control cells and its marked decrease in quiescent cells. It is concluded that PKC-dependent changes in system X-AG activity parallel the behavior of PKCepsilon, thus suggesting a specific role for this isoform in system X-AG regulation.
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Affiliation(s)
- R Franchi-Gazzola
- Istituto di Patologia Generale, Università degli Studi di Parma, I-43100 Parma, Italy
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25
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Bell SL, Bebbington C, Scott MF, Wardell JN, Spier RE, Bushell ME, Sanders PG. Genetic engineering of hybridoma glutamine metabolism. Enzyme Microb Technol 1995; 17:98-106. [PMID: 7766007 DOI: 10.1016/0141-0229(94)00056-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The murine hybridoma PQXB1/2 cannot be adapted to grow in culture media containing < 0.5 mM glutamine. Transformants selected following electroporation of PQXB1/2 cells with vectors containing a Chinese hamster glutamine synthetase (GS) cDNA under the control of the SV40 early promoter also failed to grow in the absence of glutamine in the culture medium. PQXB1/2 cells have, however, been transformed to glutamine independence following electroporation with a vector containing this glutamine synthetase cDNA under the control of the human cytomegalovirus immediate early promoter. In these cells, sufficient active glutamine synthetase was expressed from one vector per cell to enable growth in glutamine-free media. The specific activity of glutamine synthetase in two transformed cell lines producing parental levels of antibody was increased by 128 and 152%, respectively (0.57 and 0.63 mumol min-1 per 10(6) cells in transformants compared with parental levels of 0.25 mumol min-1 per 10(6) cells). This reprogramming of glutamine synthetase expression and glutamine metabolism is important for developing strategies to deal with ammonia toxicity and the production of cell lines with improved metabolic processes.
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Affiliation(s)
- S L Bell
- School of Biological Sciences, University of Surrey, Guildford, England
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Christie A, Butler M. Glutamine-based dipeptides are utilized in mammalian cell culture by extracellular hydrolysis catalyzed by a specific peptidase. J Biotechnol 1994; 37:277-90. [PMID: 7765576 DOI: 10.1016/0168-1656(94)90134-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A murine hybridoma (CC9C10) was grown in media containing alanyl-glutamine (ala-gln) or glycyl-glutamine (gly-gln) as a substitute for glutamine. High cell yields were obtained in the presence of 6 mM ala-gln or 20 mM gly-gln. The final cell yield in gly-gln was 14% higher than in gln. Monoclonal antibody productivity was comparable in gln, ala-gln or gly-gln. Substrate utilisation and metabolism was affected by the presence of the dipeptides, particularly with gly-gln. The specific consumption rates of glucose and six amino acids were reduced. Also the accumulation of ammonia and lactate was significantly lower. The higher concentration of gly-gln was necessary for cell growth because of the presence of a peptidase with a lower affinity for gly-gln. The peptidase activity of the basal medium and serum was low. However, a substantial peptidase activity was found in the cytosolic fraction of the cells with an apparent Km of 1.2 mM with respect to ala-gln and 14 mM with respect to gly-gln. It is proposed that the mechanism of dipeptide utilisation involves extracellular hydrolysis by this peptidase following its release into the culture medium.
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Affiliation(s)
- A Christie
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
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27
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Bols NC, Ganassin RC, Tom DJ, Lee LE. Growth of fish cell lines in glutamine-free media. Cytotechnology 1994; 16:159-66. [PMID: 7766144 DOI: 10.1007/bf00749903] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The glutamine requirement for the in vitro proliferation of fish cells was investigated with cell lines from four different species and three tissues: goldfish skin (GFSk-S1), Chinook salmon embryo (CHSE-214), and rainbow trout liver (RTL-W1) and spleen (RTSp-W1). With a supplement of fetal bovine serum, the basal medium, Leibovitz's L-15, without glutamine supported the proliferation of all four cell lines as well, or nearly as well, as L-15 with 2 mM glutamine. This was true over short term assays of two to four weeks and for continuous propagation. CHSE-214 also grew as well with or without 2 mM glutamine in Minimum Essential Medium with fetal bovine serum. However, when the supplement was dialyzed fetal bovine serum, CHSE-214 grew much better in L-15 without glutamine. Therefore, glutamine was not required for growth in L-15, and in fact, was inhibitory in the absence of the dialyzable fraction of serum. By contrast, glutamine appeared to be important for growth in Minimum Essential Medium. When the supplement was dialyzed fetal bovine serum, CHSE-214 grew much better in Minimum Essential Medium with 2 mM glutamine. These results suggest that the glutamine requirement for the in vitro proliferation of fish cells is conditional and depends on the basal medium and serum supplement.
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Affiliation(s)
- N C Bols
- Department of Biology, University of Waterloo, ON, Canada
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28
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Abstract
Although glutamine is used as a major substrate for the growth of mammalian cells in culture, it suffers from some disadvantages. Glutamine is deaminated through storage or by cellular metabolism, leading to the formation of ammonia which can result in growth inhibition. Non-ammoniagenic alternatives to glutamine have been investigated in an attempt to develop strategies for obtaining improved cell yields for ammonia sensitive cell lines. Glutamate is a suitable substitute for glutamine in some culture systems. A period of adaptation to glutamate is required during which the activity of glutamine synthetase and the rate of transport of glutamate both increase. The cell yield increases when the ammonia accumulation is decreased following culture supplementation with glutamate rather than glutamine. However some cell lines fail to adapt to growth in glutamate and this may be due to a low efficiency transport system. The glutamine-based dipeptides, ala-gln and gly-gln can substitute for glutamine in cultures of antibody-secreting hybridomas. The accumulation of ammonia in these cultures is less and cell yields in dipeptide-based media may be improved compared to glutamine-based controls. In murine hybridomas, a higher concentration of gly-gln is required to obtain comparable cell growth to ala-gln or gln-based cultures. This is attributed to a requirement for dipeptide hydrolysis catalyzed by an enzyme with higher affinity for ala-gln than gly-gln.
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Affiliation(s)
- M Butler
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
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Fitzpatrick L, Jenkins HA, Butler M. Glucose and glutamine metabolism of a murine B-lymphocyte hybridoma grown in batch culture. Appl Biochem Biotechnol 1993; 43:93-116. [PMID: 8267405 DOI: 10.1007/bf02916435] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The energy metabolism of a mammalian cell line grown in vitro was analyzed by substrate consumption rates and metabolic flux measurements. The data allowed the determination of the relative importance of the pathways of glucose and glutamine metabolism to the energy requirements of the cell. Changes in the substrate concentrations during culture contributed to the changing catalytic activities of key enzymes, which were determined. 1. A murine B-lymphocyte hybridoma (PQXB1/2) was grown in batch culture to a maximum cell density of 1-2 x 10(6) cells/mL in 3-4 d. The intracellular protein content showed a maximum value during the exponential growth phase of 0.55 mg/10(6) cells. Glutamine was completely depleted, but glucose only partially depleted to 50% of its original concentration when the cells reached a stationary phase following exponential growth. 2. The specific rates of glutamine and glucose utilization varied during culture and showed maximal values at the midexponential phase of 2.4 nmol/min/10(6) cells and 4.3 nmol/min/10(6) cells, respectively. 3. A high proportion of glucose (96%) was metabolized by glycolysis, but only limited amounts by the pentose phosphate pathway (3.3%) and TCA cycle (0.21%). 4. The maximum catalytic activity of hexokinase approximates to the measured flux of glycolysis and is suggested as a rate-limiting step. In the stationary phase, the hexokinase activity reduced to 11% of its original value and may explain the reduced glucose utilization at this stage. 5. The maximal activities of two TCA cycle enzymes were well above the measured metabolic flux and are unlikely to pose regulatory barriers. However, the activity of pyruvate dehydrogenase was undetectable by spectrophotometric assay and explains the low level of flux of glycolytic metabolites into the TCA cycle. 6. A significant proportion of the glutamine (36%) utilized by the cells was completely oxidized to CO2. 7. The measured rate of glutamine transport into the cells approximated to the metabolic flux and is suggested as a rate-limiting step. 8. Glutamine metabolism is likely to occur via glutaminase and amino transaminase, which have significantly higher activities than glutamate dehydrogenase. 9. The calculated potential ATP production suggests that, overall, glutamine is the major contributor of cellular energy. However, at the midexponential phase, the energy contribution from the catabolism of the two substrates was finely balanced--glutamine (55%) and glucose (45%).
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Affiliation(s)
- L Fitzpatrick
- Department of Biological Sciences, Manchester Metropolitan University, UK
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