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Effect of Conditioned Medium Factors on Productivity and Cell Physiology in Trichoplusia ni Insect Cell Cultures

Authors

  • Karin Calles,

    1. Karo Bio AB, Huddinge, SE-141 57 Huddinge, Sweden
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    • Equal contribution to this work

  • Ulrika Eriksson,

    1. School of Biotechnology, Department of Bioprocess Technology, Royal Institute of Technology, SE-106 91 Stockholm, Sweden
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    • Equal contribution to this work

  • Lena Häggström

    Corresponding author
    1. School of Biotechnology, Department of Bioprocess Technology, Royal Institute of Technology, SE-106 91 Stockholm, Sweden
    • School of Biotechnology, Department of Bioprocess Technology, Royal Institute of Technology, SE-106 91 Stockholm, Sweden. Phone: +46-(0)8–5537 8308. Fax: +46-(0)8–5537 8323
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Abstract

The influence of conditioned medium (CM) on cell physiology and recombinant protein production in Trichoplusia ni insect cells (T. ni, BTI-Tn-5B1–4) has been investigated. Cell cycle analysis showed that a high proportion of the cell population (80–90%) was in G1 during the whole culture, indicating that the S and G2/M phases are short relative to the G1 phase. Directly after inoculation, a rapid decrease of the S-phase population occurred, which could be observed as a lag-phase. The following increase in the number of cells in S occurred after 7 h of culture for cells in fresh medium, whereas for cells with the addition of CM it occurred at an earlier time point (5 h) and these cells had therefore a shorter lag-phase. The initial changes in the S-phase population were also affected by the inoculum cell density, as higher seeding cell densities resulted in a more rapid increase in the S-phase population after inoculation. These changes in cell cycle distribution were reflected in the cell size, and the CM-cells were smaller than the cells in fresh medium. Recombinant protein production in T. ni cells was improved by the addition of CM. The specific productivity was increased by 30% compared to cells in fresh medium. This beneficial effect was seen between 20 and 72 h of culture. In contrast, the highest specific productivity was obtained already at 7 h for the cells in fresh medium and then decreased rapidly. The total product concentration was around 30% higher in the culture with CM compared to the culture in fresh medium, and the maximum product concentration was obtained on day 2 compared to day 3 for the cells in fresh medium. Our results indicate that the positive effect on productivity by CM is related to its growth-promoting effect, suggesting that the proliferation potential of the culture determines the productivity.

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