Chinese hamster ovary cell performance enhanced by a rational divide-and-conquer strategy for chemically defined medium development

Advances in serum-free media for CHO cells: From traditional serum substitutes to microbial-derived substances

The Chinese hamster ovary (CHO) cell is an epithelial-like cell that produces proteins with post-translational modifications similar to human glycosylation. It is widely used in the production of recombinant therapeutic proteins and monoclonal antibodies. Culturing CHO cells typically requires the addition of a certain proportion of fetal bovine serum (FBS) to maintain cell proliferation and passaging. However, serum is characterized by its complex composition, batch-to-batch variability, high cost, and potential risk of exogenous contaminants such as mycoplasma and viruses, which impact the purity and safety of the synthesized proteins. Therefore, search for serum alternatives and development of serum-free media for CHO-based protein biomanufacturing are of great significance. This review systematically summarizes the application advantages of CHO cells and strategies for high-density expression. It highlights the developmental trends of serum substitutes from human platelet lysates to animal-free extracts and microbial-derived substances and elucidates the mechanisms by which these substitutes enhance CHO cell culture performance and recombinant protein production, aiming to provide theoretical guidance for exploring novel serum alternatives and developing serum-free media for CHO cells.

Optimization of medium with perfusion microbioreactors for high density CHO cell cultures at very low renewal rate aided by design of experiments

A novel approach of design of experiment (DoE) is developed for the optimization of key substrates of the culture medium, amino acids, and sugars, by utilizing perfusion microbioreactors with 2 mL working volume, operated in high cell density continuous mode, to explore the design space. A mixture DoE based on a simplex-centroid is proposed to test multiple medium blends in parallel perfusion runs, where the amino acids concentrations are selected based on the culture behavior in presence of different amino acid mixtures, and using targeted specific consumption rates. An optimized medium is identified with models predicting the culture parameters and product quality attributes (G0 and G1 level N-glycans) as a function of the medium composition. It is then validated in runs performed in perfusion microbioreactor in comparison with stirred-tank bioreactors equipped with alternating tangential flow filtration (ATF) or with tangential flow filtration (TFF) for cell separation, showing overall a similar process performance and N-glycosylation profile of the produced antibody. These results demonstrate that the present development strategy generates a perfusion medium with optimized performance for stable Chinese hamster ovary (CHO) cell cultures operated with very high cell densities of 60 × 106 and 120 × 106  cells/mL and a low cell-specific perfusion rate of 17 pL/cell/day, which is among the lowest reported and is in line with the framework recently published by the industry.

Spent media analysis suggests cultivated meat media will require species and cell type optimization

Cell culture media design is perhaps the most significant hurdle currently facing the commercialization of cultivated meat as an alternative source of dietary protein. Since media optimization for a specific culture system requires a significant amount of effort and investment, a major question remaining is whether media formulations can be easily shared across multiple production schemes for cells of different species and lineages. Here, we perform spent medium analysis to compare the specific nutrient utilization of primary embryonic chicken muscle precursor cells and fibroblasts to the murine C2C12 myoblast cell line. We demonstrate that these related cell types have significantly different nutrient utilization patterns collectively and on a per-cell basis, and that many components of conventional media do not appear to be depleted by the cells. Namely, glucose was not consumed as rapidly nor as completely by the chicken muscle precursors compared to other cells overall, and there were significant differences in specific consumption rates for several other key nutrients over the first day of culture. Ultimately, our results indicate that no one medium is likely ideal and cost effective to culture multiple cell types and that novel methods to streamline media optimization efforts will be important for the industry to develop.

Combination of sodium butyrate and decitabine promotes transgene expression in CHO cells via apoptosis inhibition

Chinese hamster ovary (CHO) cells are currently the most widely used host cells for production of recombinant therapeutic proteins (RTPs). Small-molecule additives related to cell cycle apoptosis and autophagy regulation have been used to promote RTP production. By combining two small-molecule additives, positive synergistic effects on transgene expression were observed in CHO cells. In the present study, six small-molecule additives were used, including hydrocinnamic acid (HCA), sodium butyrate (NaB), lithium acetate (LiAc), sodium succinate dibasic hexahydrate (SDH), decitabine (DAC), and sodium propionate (SP). Experiments to test the effects of their pairwise combinations on two different recombinant CHO cell lines (rCHO) were designed using Design-Expert 12.0. Different effects of various pairs of small molecules on apoptosis- and autophagy-related protein expression were observed in the rCHOs. The results showed that compared to the control culture, NaB alone increased the volumetric yield and specific productivity (Qp) by 166% and 143%, respectively. The volumetric yield and Qp of NaB combined with DAC (Cg1)-treated cells increased by 178% and 212%, respectively. Cg1 selectively blocked the cells in the G0/G1 cell cycle stage. The relative expression levels of B-cell lymphoma 2 (Bcl-2), Beclin 1, and microtubule-associated protein light chain 3 (LC3B) in Cg1-treated CHO cells were significantly increased, while relative levels of cleaved caspase-3 expression were significantly decreased. In conclusion, Cg1 had the most obvious effect on RTP production and Qp in CHO cells, suggesting the Cg1 combination of small molecules may be used to improve the expression of recombinant protein in CHO cells.

Clever Experimental Designs: Shortcuts for Better iPSC Differentiation

For practical use of pluripotent stem cells (PSCs) for disease modelling, drug screening, and regenerative medicine, the cell differentiation process needs to be properly refined to generate end products with consistent and high quality. To construct and optimize a robust cell-induction process, a myriad of cell culture conditions should be considered. In contrast to inefficient brute-force screening, statistical design of experiments (DOE) approaches, such as factorial design, orthogonal array design, response surface methodology (RSM), definitive screening design (DSD), and mixture design, enable efficient and strategic screening of conditions in smaller experimental runs through multifactorial screening and/or quantitative modeling. Although DOE has become routinely utilized in the bioengineering and pharmaceutical fields, the imminent need of more detailed cell-lineage specification, complex organoid construction, and a stable supply of qualified cell-derived material requires expedition of DOE utilization in stem cell bioprocessing. This review summarizes DOE-based cell culture optimizations of PSCs, mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and Chinese hamster ovary (CHO) cells, which guide effective research and development of PSC-derived materials for academic and industrial applications.

Generation of site-distinct N-glycan variants for in vitro bioactivity testing

Glycosylation, a critical product quality attribute, may affect the efficacy and safety of therapeutic proteins in vivo. Chinese hamster ovary fed-batch cell culture batches yielded consistent glycoprofiles of a Fc-fusion antibody comprizing three different N-glycosylation sites. By adding media supplements at specific concentrations in cell culture and applying enzymatic glycoengineering, a diverse N-glycan variant population was generated, including high mannose, afucosylated, fucosylated, agalactosylated, galactosylated, asialylated, and sialylated forms. Site-specific glycosylation profiles were elucidated by glycopeptide mapping and the effect of the glycosylation variants on the FcγRIIIa receptor binding affinity and the biological activity (cell-based and surface plasmon resonance) was assessed. The two fusion body glycosylation sites were characterized by a high degree of sialic acid, more complex N-glycan structures, a higher degree of antennarity, and a site-specific behavior in the presence of a media supplement. On the other hand, the media supplements affected the Fc-site glycosylation heterogeneity similarly to the various studies described in the literature with classical monoclonal antibodies. Enzymatic glycoengineering solely managed to generate high levels of galactosylation at the fusion body sites. Variants with low core fucosylation, and to a lower extent, high mannose glycans exhibited increased FcγRIIIa receptor binding affinity. All N-glycan variants exhibited weak effects on the biological activity of the fusion body. Both media supplementation and enzymatic glycoengineering are suitable to generate sufficient diversity to assess the effect of glycostructures on the biological activity.

Impact of hydrolysates on monoclonal antibody productivity, purification and quality in Chinese hamster ovary cells

Plant and yeast derived hydrolysates are economical and efficient alternative medium supplements to improve mammalian cell culture performance. We supplemented two commercial Chinese hamster ovary (CHO) culture media with hydrolysates from four different sources, yeast, soybean, Ex-Cell CD (a chemically defined hydrolysate replacement) and wheat to improve the productivity of two cell lines expressing different monoclonal antibodies (mAbs). Yeast, soybean and Ex-Cell CD improved the final mAb titer by increasing the specific productivity (qP) and/or extension of the culture period. Wheat hydrolysates increased peak viable cell density but did not improve productivity. IgG recovery from protein A purification was not compromised for all cultures by adding yeast, soybean and Ex-Cell CD hydrolysates except for one sample from soybean supplemented culture. Adding these three hydrolysates neither increased the amount of host cell protein, DNA or aggregate impurity amounts nor affect their clearance after purification. Profiling of the glycan types revealed that yeast and soybean hydrolysates could affect the distribution of galactosylated glycans. Ex-Cell CD performed the best at maintaining glycan profile compared to the non-supplemented cultures. Overall, yeast performed the best at improving CHO culture growth and productivity without being detrimental to downstream protein A processes but could affect mAb product glycan distribution while Ex-Cell CD yielded lower titers but has less effect on glycosylation. The hydrolysate to use would thus depend on the requirements of each process and our results would provide a good reference for improving culture performance with hydrolysates or related studies.