The growth factor inhibitor suramin reduces apoptosis and cell aggregation in protein-free CHO cell batch cultures

Effects and mechanism of small molecule additives on recombinant protein in CHO cells

Chinese hamster ovary (CHO) cells can produce proteins with complex structures and post-translational modifications which are similar to human-derived cells, and they have been the ideal host cells for the production of recombinant therapy proteins (RTPs). Nearly 70% of approved RTPs are produced by CHO cells. In recent years, a series of measures have been developed to increase the expression of RTPs to achieve the lower production cost during the process of large-scale industrial production of recombinant protein in CHO cells. Among of them, the addition of small molecule additives in the culture medium can improve the expression and production efficiency of recombinant proteins, and has become an effective and simple method. In this paper, the characteristics of CHO cells, the effect and mechanism of small molecule additives are reviewed. KEY POINTS: • Small molecular additives on the expression of RTPs in CHO cells are reviewed • Small molecular additives improve the yield of RTPs • Small molecular additives provide methods for the optimization of serum-free medium.

Single-Use Bioreactors for Human Pluripotent and Adult Stem Cells: Towards Regenerative Medicine Applications

Research on human stem cells, such as pluripotent stem cells and mesenchymal stromal cells, has shown much promise in their use for regenerative medicine approaches. However, their use in patients requires large-scale expansion systems while maintaining the quality of the cells. Due to their characteristics, bioreactors have been regarded as ideal platforms to harbour stem cell biomanufacturing at a large scale. Specifically, single-use bioreactors have been recommended by regulatory agencies due to reducing the risk of product contamination, and many different systems have already been developed. This review describes single-use bioreactor platforms which have been used for human stem cell expansion and differentiation, along with their comparison with reusable systems in the development of a stem cell bioprocess for clinical applications.

Quantifying the impact of cell culture media on CHO cell growth and protein production

In recombinant protein production, cell culture media development and optimization is typically seen as a useful strategy to increase titer and cell density, reduce by-products, as well as improve product quality (with cell density and titer often serving as the primary reported outcome of media studies). However, despite the large number of media optimization studies, there have been few attempts to comprehensively assess the overall effectiveness of media additives. The aim of this review is therefore both to document published media optimization studies over the last twenty years (in the context of Chinese hamster ovary cell recombinant production) and quantitatively estimate the impact of this media optimization on cell culture performance. In considering 78 studies, we have identified 238 unique media components that have been supplemented over the last 20 years. Among these additives, trace elements stood out as having a positive impact on cell density while nucleotides show potential for increasing titer, with commercial supplements benefiting both. However, we also identified that the impact of specific additives is far more variable than often perceived. With relatively few media studies considering multiple cell lines or multiple basal media, teasing out consistent and general trends becomes a considerable challenge. By extracting cell density and titer values from all of the reviewed studies, we were able to build a mixed-effect model capable of estimating the relative impact of additives, cell line, product type, basal medium, cultivation method (flask or reactor), and feeding strategy (batch or fed-batch). Overall, additives only accounted for 3% of the variation in cell density and 1% of the variation in titer. Similarly, the impact of basal media was also relatively modest, at 10% for cell density and 0% for titer. Cell line, product type, and feeding strategy were all found to have more impact. These results emphasize the need for media studies to consider more factors to ensure that reported observations can be generalized and further developed.

Investigating the influence of physiologically relevant hydrostatic pressure on CHO cell batch culture

Chinese hamster ovary (CHO) cells have been the most commonly used mammalian host for large-scale commercial production of therapeutic proteins, such as monoclonal antibodies. Enhancement of productivity of these CHO cells is one of the top priorities in the biopharmaceutical industry to reduce manufacturing cost. Although there are many different methods (e.g. temperature, pH, feed) to improve protein production in CHO cells, the role of physiologically relevant hydrostatic pressure in CHO cell culture has not been reported yet. In this study, four different hydrostatic pressures (0, 30, 60, and 90 mmHg) were applied to batch CHO cells, and their cell growth/metabolism and IgG₁ production were examined. Our results indicate that hydrostatic pressure can increase the maximum cell concentration by up to 50%. Moreover, overall IgG₁ concentration on Day 5 showed that 30 mmHg pressure can increase IgG₁ production by 26%. The percentage of non-disulphide-linked antibody aggregates had no significant change under pressure. Besides, no significant difference was observed between 30 mmHg and no pressure conditions in terms of cell clumping formation. All these findings are important for the optimization of fed-batch or perfusion culture for directing cell growth and improving antibody production.

Applications of small molecules in modulating productivity and product quality of recombinant proteins produced using cell cultures

Mammalian cell cultures have been used extensively for production of recombinant protein therapeutics such as monoclonal antibodies, fusion proteins and enzymes for decades. Small molecules have been investigated as media supplements to improve process productivity and reduce cost of goods. Those chemicals can lead to significant yield improvement through different mechanisms such as cell cycle modulation, cellular redox regulation, etc. In addition to productivity, small molecules have also been routinely used to regulate post-translational modifications of recombinant proteins. This review summarizes key applications of small molecules in protein productivity improvement and product quality control.

Evaluating the impact of suramin additive on CHO cells producing Fc-fusion protein

OBJECTIVE

To examine the effects of suramin in CHO cell cultures in terms of the cell culture performance and quality of the Fc-fusion protein.

RESULTS

Suramin had positive effects on the CHO cell cultures. The addition of suramin caused an increase in the viable cell density, cell viability, and titer of the Fc-fusion protein. Moreover, suramin had no impact on protein aggregation and enhanced the sialic acid contents of Fc-fusion protein by 1.18-fold. The enhanced sialylation was not caused by the increased nucleotide sugar level but by the inhibition of sialidase activity. The results showed that suramin inhibited apoptosis and had positive impacts on the productivity and quality of Fc-fusion protein.

CONCLUSION

The addition of suramin increased the production of Fc-fusion protein and enhanced sialylation when added as a supplement to the media component in CHO cell cultures. This study suggested that suramin could be a beneficial additive during the biological production in terms of the productivity and quality of Fc-fusion protein.

Strategies for the expansion of human induced pluripotent stem cells as aggregates in single-use Vertical-Wheel™ bioreactors

Background

Since their inception, human induced pluripotent stem cells (hiPSCs) have held much promise for pharmacological applications and cell-based therapies. However, their potential can only be realised if large numbers of cells can be produced reproducibly on-demand. While bioreactors are ideal systems for this task, due to providing agitation and control of the culture parameters, the common impeller geometries were not designed for the expansion of mammalian cells, potentially leading to sub-optimal results.

Results

This work reports for the first time the usage of the novel Vertical-Wheel single-use bioreactors for the expansion of hiPSCs as floating aggregates. Cultures were performed in the PBS MINI 0.1 bioreactor with 60 mL of working volume. Two different culture media were tested, mTeSR1 and mTeSR3D, in a repeated batch or fed-batch mode, respectively, as well as dextran sulfate (DS) supplementation. mTeSR3D was shown to sustain hiPSC expansion, although with lower maximum cell density than mTeSR1. Dextran sulfate supplementation led to an increase in 97 and 106% in maximum cell number when using mTeSR1 or mTeSR3D, respectively. For supplemented media, mTeSR1 + DS allowed for a higher cell density to be obtained with one less day of culture. A maximum cell density of (2.3 ± 0.2) × 10⁶ cells∙mL^− 1 and a volumetric productivity of (4.6 ± 0.3) × 10⁵ cells∙mL^− 1∙d^− 1 were obtained after 5 days with mTeSR1 + DS, resulting in aggregates with an average diameter of 346 ± 11 μm. The generated hiPSCs were analysed by flow cytometry and qRT-PCR and their differentiation potential was assayed, revealing the maintenance of their pluripotency after expansion.

Conclusions

The results here described present the Vertical-Wheel bioreactor as a promising technology for hiPSC bioprocessing. The specific characteristics of this bioreactor, namely in terms of the innovative agitation mechanism, can make it an important system in the development of hiPSC-derived products under current Good Manufacturing Practices.

Mucin-coating technologies for protection and reduced aggregation of cellular production systems

Optimization of host-cell production systems with improved yield and production reliability is desired to meet the increasing demand for biologics with complex posttranslational modifications. Aggregation of suspension-adapted mammalian cells remains a significant problem that can limit the cellular density and per volume yield of bioreactors. Here, we propose a genetically encoded technology that directs the synthesis of antiadhesive and protective coatings on the cellular surface. Inspired by the natural ability of mucin glycoproteins to resist cellular adhesion and hydrate and protect cell and tissue surfaces, we genetically encode new cell-surface coatings through the fusion of engineered mucin domains to synthetic transmembrane anchors. Combined with appropriate expression systems, the mucin-coating technology directs the assembly of thick, highly hydrated barriers to strongly mitigate cell aggregation and protect cells in suspension against fluid shear stresses. The coating technology is demonstrated on suspension-adapted human 293-F cells, which resist clumping even in media formulations that otherwise would induce extreme cell aggregation and show improved performance over a commercially available anticlumping agent. The stable biopolymer coatings do not show deleterious effects on cell proliferation rate, efficiency of transient transfection with complementary DNAs, or recombinant protein expression. Overall, our mucin-coating technology and engineered cell lines have the potential to improve the single-cell growth and viability of suspended cells in bioreactors.

Human Pluripotent Stem Cells: Applications and Challenges for Regenerative Medicine and Disease Modeling

In recent years, human pluripotent stem (hPS) cells have started to emerge as a potential tool with application in fields such as regenerative medicine, disease modeling, and drug screening. In particular, the ability to differentiate human-induced pluripotent stem (hiPS) cells into different cell types and to mimic structures and functions of a specific target organ, resourcing to organoid technology, has introduced novel model systems for disease recapitulation while offering a powerful tool to provide a faster and reproducible approach in the process of drug discovery. All these technologies are expected to improve the overall quality of life of the humankind. Here, we highlight the main applications of hiPS cells and the main challenges associated with the translation of hPS cell derivatives into clinical settings and other biomedical applications, such as the costs of the process and the ability to mimic the complexity of the in vivo systems. Moreover, we focus on the bioprocessing approaches that can be applied towards the production of high numbers of cells as well as their efficient differentiation into the final product and further purification.

Chemically controlled aggregation of pluripotent stem cells

Heterogeneity in pluripotent stem cell (PSC) aggregation leads to variability in mass transfer and signaling gradients between aggregates, which results in heterogeneous differentiation and therefore variability in product quality and yield. We have characterized a chemical‐based method to control aggregate size within a specific, tunable range with low heterogeneity, thereby reducing process variability in PSC expansion. This method enables controlled, scalable, stirred suspension‐based manufacturing of PSC cultures that are critical for the translation of regenerative medicine strategies to clinical products.

Combination of temperature shift and hydrolysate addition regulates anti-IgE monoclonal antibody charge heterogeneity in Chinese hamster ovary cell fed-batch culture

Charge heterogeneity has been broadly studied as a critical quality attribute during monoclonal antibody (mAb) production that may subsequently affect product stability and biopotency. However, the charge variation distribution is poorly controlled, so methods of more effective control need to be explored. In this study, the combined effects of temperature shift (37-34, 37-32, or 37-30 °C) and hydrolysate addition (0.100 g/L) to culture feed on the charge heterogeneity of anti-IgE mAb were investigated. The results showed that the distribution of charge variation was significantly regulated by the combination of hydrolysate addition with a highly sub-physiological temperature (34 °C). In addition, under this condition, the main peak content significantly increased, and the acidic peak content significantly decreased. Furthermore, we explored Lys variant content, which is the major basic variant content, as well as its relationship with temperature shift and hydrolysate addition. Lys variant levels were positively related to the Lys and Arg concentrations in the medium and negatively related to carboxypeptidase B and carboxypeptidase H transcript levels. The combination of temperature shift and hydrolysate addition can thus effectively improve anti-IgE mAb charge heterogeneity and significantly increase main variant levels and decrease acidic variant levels.

Measuring the aggregation of CHO cells prior to single cell cloning allows a more accurate determination of the probability of clonality

The manufacturing process for biotherapeutics is closely regulated by the Food and Drug Administration (FDA), European Medicines Agency (EMA) and other regulatory agencies worldwide. To ensure consistency of the product of a manufacturing cell line, International Committee on Harmonization guidelines (Q5D, 1997) state that the cell substrate should be derived from a single cell progenitor, i.e., clonal.Cell lines in suspension culture may naturally revert to cell adhesion in the form of doublets, triplets and higher order structures of clustered cells. We can show evidence of a single colony from limiting dilution cloning or in semi-solid media, but we cannot determine the number of cells from which the colony originated. To address this, we have used the ViCELL® XR (Beckman Coulter, High Wycombe, UK) cell viability analyzer to determine the proportion of clusters of two or more cells in a sample of the cell suspension immediately prior to cloning. Here, we show data to define the accuracy of the ViCELL for characterizing a cell suspension and summarize the statistical model combining two or more rounds of cloning to derive the probability of clonality. The resulting statistical model is applied to cloning in semi-solid medium, but could equally be applied to a limiting dilution cloning process. We also describe approaches to reduce cell clusters to generate a cell line with a high probability of clonality from a CHO host lineage. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:593-601, 2018.

Growth factors mediated differentiation of mesenchymal stem cells to cardiac polymicrotissue using hanging drop and bioreactor

Heart disease is the major leading cause of death worldwide and the use of stem cells promises new ways for its treatment. The relatively easy and quick acquisition of human umbilical cord matrix mesenchymal stem cells (HUMSCs) and their properties make them useful for the treatment of cardiac diseases. Therefore, the main aim of this investigation was to create cardiac polymicrotissue from HUMSCs using a combination of growth factors [sphingosine-1-phosphate (S1P) and suramin] and techniques (hanging drop and bioreactor). Using designated culture conditions of the growth factors (100 nM S1P and 500 µM suramin), cardiomyocyte differentiation medium (CDM), hanging drop, bioreactor and differentiation for 7 days, a potential specific cardiac polymicrotissue was derived from HUMSCs. The effectiveness of growth factors alone or in combination in differentiation of HUMSCs to cardiac polymicrotissue was analysed by assessing the presence of cardiac markers by immunocytochemistry. This analysis demonstrated the importance of those growth factors for the differentiation. This study for the first time demonstrated the formation of a cardiac polymicrotissue under specific culture conditions. The polymicrotissue thus obtained may be used in future as a 'patch' to cover the injured cardiac region and would thereby be useful for the treatment of heart diseases.

Combination of dextran sulfate and recombinant trypsin on aggregation of Chinese hamster ovary cells

In laboratory scale therapeutical protein production, cell clumps form typically in shake flasks, which hinders cell growth and decreases protein yield. To minimize clumps during the culture of Chinese hamster ovary cells, we employed the combination of two reagents, dextran sulfate (DS) and recombinant trypsin (r-trypsin). Our results showed that both DS and r-trypsin could diminish cell aggregation when adding them respectively, but clumps were still noticed obviously. In order to further mitigate cell agglomerate, a combination of 1.2 g/L DS and 8.0 mg/L r-trypsin was employed and no clumps were found under the bright field microscope. Strikingly, the highest viable cell density of combination group was increased from 5.12 × 10(6) to 7.13 × 10(6) cells/mL, while the integral of viable cells concentration was raised from 35.13 × 10(6) to 60.87 × 10(6) cells·days/mL, and the culture period was prolonged by 4 days. In addition, the antibody integrity was maintained in the combination group compared with that of the control.

The beneficial effect of suramin on monocrotaline-induced pulmonary hypertension in rats

BACKGROUND

Pulmonary hypertension (PH) is a progressive disorder characterized by an increase in pulmonary artery pressure and structural changes in the pulmonary vasculature. Several observations indicate that growth factors play a key role in PH by modulating pulmonary artery smooth muscle cell (PA-SMC) function. In rats, established monocrotaline-induced PH (MCT-PH) can be reversed by blocking platelet-derived growth factor receptors (PDGF-R), epidermal growth factor receptors (EGF-R), or fibroblast growth factor receptors (FGF-R). All these receptors belong to the receptor tyrosine kinase (RTK) family.

METHODS AND RESULTS

We evaluated whether RTK blockade by the nonspecific growth factor inhibitor, suramin, reversed advanced MCT-PH in rats via its effects on growth-factor signaling pathways. We found that suramin inhibited RTK and ERK1/2 phosphorylation in cultured human PA-SMCs. Suramin inhibited PA-SMC proliferation induced by serum, PDGF, FGF2, or EGF in vitro and ex vivo. Treatment with suramin from day 1 to day 21 after monocrotaline injection attenuated PH development, as shown by lower values for pulmonary artery pressure, right ventricular hypertrophy, and distal vessel muscularization on day 21 compared to control rats. Treatment with suramin from day 21 to day 42 after monocrotaline injection reversed established PH, thereby normalizing the pulmonary artery pressure values and vessel structure. Suramin treatment suppressed PA-SMC proliferation and attenuated both the inflammatory response and the deposition of collagen.

CONCLUSIONS

RTK blockade by suramin can prevent MCT-PH and reverse established MCT-PH in rats. This study suggests that an anti-RTK strategy that targets multiple RTKs could be useful in the treatment of pulmonary hypertension.

Gene expression profiling for mechanistic understanding of cellular aggregation in mammalian cell perfusion cultures

Aggregation of baby hamster kidney (BHK) cells cultivated in perfusion mode for manufacturing recombinant proteins was characterized. The potential impact of cultivation time on cell aggregation for an aggregating culture (cell line A) was studied by comparing expression profiles of 84 genes in the extracellular adhesion molecules (ECM) pathway by qRT-PCR from 9 and 25 day shake flask samples and 80 and 94 day bioreactor samples. Significant up-regulation of THBS2 (4.4- to 6.9-fold) was seen in both the 25 day shake flask and 80 and 94 day bioreactor samples compared to the 9 day shake flask while NCAM1 was down-regulated 5.1- to 8.9-fold in the 80 and 94 day bioreactor samples. Subsequent comparisons were made between cell line A and a non-aggregating culture (cell line B). A 65 day perfusion bioreactor sample from cell line B served as the control for 80 and 94 day samples from four different perfusion bioreactors for cell line A. Of the 84 genes in the ECM pathway, four (COL1A1, COL4A1, THBS2, and VCAN) were consistently up-regulated in cell line A while two (NCAM1 and THBS1) were consistently down-regulated. The magnitudes of differential gene expression were much higher when cell lines were compared (4.1- to 44.6-fold) than when early and late cell line B samples were compared (4.4- to 6.9-fold) indicating greater variability between aggregating and non-aggregating cell lines. Based on the differential gene expression results, two mechanistic models were proposed for aggregation of BHK cells in perfusion cultures.

Detachment factors for enhanced carrier to carrier transfer of CHO cell lines on macroporous microcarriers

In this publication different detachment factors were tested for enhancing carrier to carrier transfer for scale-up of macroporous microcarrier based bioprocesses. Two Chinese hamster ovary cell lines, CHO-K1 and a genetically engineered CHO-K1 derived cell line (CHO-MPS), producing recombinant human Arylsulfatase B, were examined. The cells were grown on Cytoline 1microcarriers (Amersham Biosciences, Uppsala, Sweden) in protein-free and chemically defined medium respectively. Fully colonised microcarriers were used at passage ratios of approximately 1:10 for carrier to carrier transfer experiments. To accelerate the colonisation of the non-colonised, freshly added microcarriers the detachment reagents trypsin, papain, Accutasetrade mark (PAA, Linz, Austria), heparin and dextransulphate were used. Both cell lines showed good results with trypsin, Accutase and dextransulphate (Amersham Biosciences, Uppsala, Sweden), while papain failed to enhance carrier to carrier transfer in comparison to the non-treated reference. The maximum growth rate of cells on microcarriers with 2% dextransulphate in the medium was 0.25 +/- 0.02d(-1) and 0.27 +/- 0.03d(-1) for the CHO-MPS and CHO-K1, respectively. TheCHO-K1 grew best after detachment with trypsin (mu = 0.36 +/- 0.03d(-1)). This indicates, that one of the key parameters for carrier to carrier transfer is the uniform distribution of cells on the individual carriers during the initial phase. When this distribution can be improved, growth rate increases, resulting in a faster and more stable process.

NMR-based metabolomics of mammalian cell and tissue cultures

NMR spectroscopy was used to evaluate growth media and the cellular metabolome in two systems of interest to biomedical research. The first of these was a Chinese hamster ovary cell line engineered to express a recombinant protein. Here, NMR spectroscopy and a quantum mechanical total line shape analysis were utilized to quantify 30 metabolites such as amino acids, Krebs cycle intermediates, activated sugars, cofactors, and others in both media and cell extracts. The impact of bioreactor scale and addition of anti-apoptotic agents to the media on the extracellular and intracellular metabolome indicated changes in metabolic pathways of energy utilization. These results shed light into culture parameters that can be manipulated to optimize growth and protein production. Second, metabolomic analysis was performed on the superfusion media in a common model used for drug metabolism and toxicology studies, in vitro liver slices. In this study, it is demonstrated that two of the 48 standard media components, choline and histidine are depleted at a faster rate than many other nutrients. Augmenting the starting media with extra choline and histidine improves the long-term liver slice viability as measured by higher tissues levels of lactate dehydrogenase (LDH), glutathione and ATP, as well as lower LDH levels in the media at time points out to 94 h after initiation of incubation. In both models, media components and cellular metabolites are measured over time and correlated with currently accepted endpoint measures.

Effects of energy dissipation rate on islets of Langerhans: implications for isolation and transplantation

Acute physical stresses can occur in the procurement and isolation process and potentially can contribute to islet death or malfunction upon transplantation. A contractional flow device, previously used to subject suspended cells to well-defined hydrodynamic forces, has been modified and used to assess the vulnerability of porcine islets of Langerhans to hydrodynamic forces. The flow profiles and velocity gradients in this modified device were modeled using commercial CFD software and characterized, as in previous studies, with the scalar parameter, energy dissipation rate (EDR). Porcine islets were stressed in a single pass at various stress levels (i.e., values of EDR). Membrane integrity, oxygen uptake rate, caspase 3/7 activity, and insulin release were not affected by the levels of fluid stress tested up to an EDR of 2 x 10(3) W/m(3). Visual observation of the stressed islets suggested that cells at the islet exterior were peeled away at EDR greater than 10,000 W/m(3), however, this observation could not be confirmed using image analysis software, which determined the ratio of surface perimeter to total area. The result of this study suggests an upper limit in fluid stress to which islets can be subjected. Such upper limits assist in the design and operation of future islet processing equipment and processes.

Enhanced Human Thrombopoietin Production by Sodium Butyrate Addition to Serum-Free Suspension Culture of Bcl-2-Overexpressing CHO Cells

When sodium butyrate (NaBu) was added to serum-free suspension culture of recombinant CHO (rCHO) cells for enhanced expression of human thrombopoietin (hTPO), apoptotic cell death of rCHO cells was induced in a dose-dependent manner and hTPO quality was deteriorated in regard to sialic acid and acidic isoform contents. To overcome these problems, we overexpressed Bcl-2 protein, an antiapoptotic protein, in rCHO cells producing hTPO. Compared to serum-free suspension culture of control cells without Bcl-2 overexpression (R-neo cells) and NaBu addition, a more than 10-fold increase in the maximum hTPO concentration was obtained in serum-free suspension culture of cells with Bcl-2 overexpression (R-bc12-14 cells) and 3 mM NaBu addition. Both the enhanced specific productivity endowed by NaBu and the extended culture longevity provided by the antiapoptotic effect of Bcl-2 overexpression contributed to the enhancement of maximum hTPO concentration. The problem of quality reduction of hTPO induced by NaBu was not solved by Bcl-2 overexpression, but it was not that significant. Compared to the culture in the absence of NaBu, the percentage of hTPO isoforms in pI 3-5 with high in vivo biological activity produced by R-bc12-14 cells was decreased by approximately 18% in the presence of 3 mM. As a result, a more than 6-fold increase in the production of hTPO isoforms in pI 3-5 was achieved in R-bcl2-14 cell culture with 3 mM NaBu addition. Taken together, the data obtained suggest that Bcl-2 overexpression in rCHO cells and NaBu addition in serum-free suspension culture can be an effective means to enhance the production of highly glycosylated protein such as hTPO.

Assessment of cell engineering strategies for improved therapeutic protein production in CHO cells

Recombinant glycoprotein therapeutics have proven to be invaluable pharmaceuticals for the treatment of various diseases. Chinese hamster ovary (CHO) cells are widely used in industry for the production of these proteins. Several strategies for engineering CHO cells for improved protein production have been tried with considerable results. The focus has mainly been to increase the specific productivity and to extend the culture longevity by preventing programmed cell death. These CHO cell engineering strategies, particularly those developed in Korea, are reviewed here.

Acute hydrodynamic forces and apoptosis: a complex question

A second generation flow contraction device was developed and modeled which allows cells to be subjected to well-defined hydrodynamic forces. Studies were conducted with this system on wild-type Chinese Hamster Ovary cells (CHO-K1) and a strain of CHO cells which expresses the human Bcl-2 triangle gene (CHO-bcl-2). In this study, the following questions were asked: (1) Does an acute hydrodynamic force induce apoptosis in wild-type CHO and CHO-bcl-2 cells? (2) Does the type of culture media make a difference with respect to the induction of apoptosis or necrosis? and (3) Does culture history affect induction of apoptosis or necrosis? The results obtained with this new flow contraction device and corresponding computer simulations are consistent with previously published studies with respect to the level of energy dissipation rate (EDR) required to create significant cell lysis. Second, while detectable relative to the control in the T-flask experiments, only a small fraction of the cells become apoptotic when exposed to a sub-lysis level of EDR (<10(8) W x m(-3)). Third, cells cultured in suspension with serum free media do not exhibit any higher or lower sensitivity (with respect to apoptosis) to various levels of EDR when compared to control cultures grown in T-flask and serum containing media; on the other hand, necrosis is significantly increased in experiments performed on suspended cells without serum. Fourth, the addition of the Bcl-2 gene product might slightly reduce the occurrence of apoptosis in T-flask culture; however, the baseline response is so low that the difference is insignificant.

Enhancement of recombinant protein production in Chinese hamster ovary cells through anti-apoptosis engineering using30Kc6 gene

It was previously reported that silkworm hemolymph (SH) inhibits apoptosis and increases the production of recombinant human erythropoietin (EPO) in Chinese hamster ovary (CHO) cells. The apoptosis-inhibiting component in SH is a member of 30K protein family. In this study, the CHO cell line producing EPO was manipulated genetically to express the 30Kc6 gene encoding a 30K protein in the hemolymph of the silkworm, Bombyx mori. The transient expression of 30Kc6 significantly suppressed the cell death induced by serum deprivation. A stable cell line expressing 30Kc6 with an anti-apoptotic property was established. The stable expression of 30Kc6 inhibited serum-deprivation-induced apoptosis and increased the cell density and EPO titer by 5- and 10-fold, respectively. The positive effects of the 30Kc6 expression on cell viability and productivity were due to the stable maintenance of the mitochondrial activity. The 30Kc6 expression efficiently suppressed the depolarization of the mitochondrial membrane and subsequently balanced the generation/consumption of ATP. The use of the 30Kc6 gene is expected to provide a new method of host cell engineering for improving the productivity of the recombinant protein.

Cell cycle analysis of Chinese hamster ovary cells stimulated by phosphatidic acid in serum-free culture

When recombinant Chinese hamster ovary cells were treated with pertussis toxin or genistein, not only lysophosphatidic acid (LPA) but also phosphatidic acid (PA) failed to stimulate progression through the cell cycle in serum-free culture, suggesting that PA and LPA induce cell growth through the same signal transduction pathway. Cell cycle analysis also indicates that cell growth promoted by PA results in enhanced protein production.

Controlled, scalable embryonic stem cell differentiation culture

Embryonic stem (ES) cells are of significant interest as a renewable source of therapeutically useful cells. ES cell aggregation is important for both human and mouse embryoid body (EB) formation and the subsequent generation of ES cell derivatives. Aggregation between EBs (agglomeration), however, inhibits cell growth and differentiation in stirred or high-cell-density static cultures. We demonstrate that the agglomeration of two EBs is initiated by E-cadherin-mediated cell attachment and followed by active cell migration. We report the development of a technology capable of controlling cell-cell interactions in scalable culture by the mass encapsulation of ES cells in size-specified agarose capsules. When placed in stirred-suspension bioreactors, encapsulated ES cells can be used to produce scalable quantities of hematopoietic progenitor cells in a controlled environment.

Use of flow-cytometric analysis to optimize cell banking strategies for production of biopharmaceuticals from mammalian cells

Production of biopharmaceuticals from mammalian cells requires generation of master, working and post-production cell banks of high quality under GMP conditions. An optimal cryopreservation strategy is needed for each new production cell line, particularly with regard to establishing production processes that are completely devoid of serum or even any animal components and to ensuring robust thaw performance for reliable production. Here, we describe a novel strategy employing flow-cytometric (FC) analysis of Annexin V-stained cells for high-throughput characterization of cell banks. Our data show that this method enables predictive evaluation of a cryopreservation strategy as early as 6h after thawing of cells. Furthermore, a broad study is presented characterizing various factors that may influence the quality of serum-free production cell banks from NSO and CHO cell lines. These results demonstrate how FC-based analysis can be used for development of future state-of-the-art cryopreservation strategies.

Animal cell cultures: recent achievements and perspectives in the production of biopharmaceuticals

There has been a rapid increase in the number and demand for approved biopharmaceuticals produced from animal cell culture processes over the last few years. In part, this has been due to the efficacy of several humanized monoclonal antibodies that are required at large doses for therapeutic use. There have also been several identifiable advances in animal cell technology that has enabled efficient biomanufacture of these products. Gene vector systems allow high specific protein expression and some minimize the undesirable process of gene silencing that may occur in prolonged culture. Characterization of cellular metabolism and physiology has enabled the design of fed-batch and perfusion bioreactor processes that has allowed a significant improvement in product yield, some of which are now approaching 5 g/L. Many of these processes are now being designed in serum-free and animal-component-free media to ensure that products are not contaminated with the adventitious agents found in bovine serum. There are several areas that can be identified that could lead to further improvement in cell culture systems. This includes the down-regulation of apoptosis to enable prolonged cell survival under potentially adverse conditions. The characterization of the critical parameters of glycosylation should enable process control to reduce the heterogeneity of glycoforms so that production processes are consistent. Further improvement may also be made by the identification of glycoforms with enhanced biological activity to enhance clinical efficacy. The ability to produce the ever-increasing number of biopharmaceuticals by animal cell culture is dependent on sufficient bioreactor capacity in the industry. A recent shortfall in available worldwide culture capacity has encouraged commercial activity in contract manufacturing operations. However, some analysts indicate that this still may not be enough and that future manufacturing demand may exceed production capacity as the number of approved biotherapeutics increases.

Beneficial effect of silkworm hemolymph on a CHO cell system: Inhibition of apoptosis and increase of EPO production

To produce erythropoietin (EPO), Chinese hamster ovary (CHO) cells were first cultured in a medium containing FBS (growth medium) and then in a serum-free medium containing sodium butyrate (production medium). Sodium butyrate increases recombinant protein production, but also induces apoptosis, which reduces cell viability and productivity. In a previous study, we found that silkworm hemolymph (SH), an insect serum, inhibits the apoptosis of insect and mammalian cells. To overcome sodium butyrate-induced apoptosis, we added SH to growth medium. This pretreatment with SH inhibited the sodium butyrate-induced apoptosis of CHO cells and consequently increased their longevity and their ability to produce EPO. As a result, the volumetric productivity of EPO was increased five-fold. SH was found to inhibit cytochrome c release from mitochondria into the cytosol, and prevented the activation of caspase-3 and other subsequent caspase reactions.

The Propeptide Domain of Lysyl Oxidase Induces Phenotypic Reversion of Ras-transformed Cells

Lysyl oxidase is an extracellular enzyme critical for the normal biosynthesis of collagens and elastin. In addition, lysyl oxidase reverts ras-mediated transformation, and lysyl oxidase expression is down-regulated in human cancers. Since suramin inhibits growth factor signaling pathways and induces lysyl oxidase in ras-transformed NIH3T3 cells (RS485 cells), we sought to investigate the effects of suramin on the phenotype of transformed cells and the role of lysyl oxidase in mediating these effects. Suramin treatment resulted in a more normal phenotype as judged by growth rate, cell cycle parameters, and morphology. beta-aminopropionitrile, the selective inhibitor of lysyl oxidase enzyme activity, was remarkably unable to block suramin-induced reversion. By contrast, ectopic antisense lysyl oxidase demonstrated that lysyl oxidase gene expression mediated phenotypic reversion. Since lysyl oxidase is synthesized as a 50 kDa precursor and processed to a 30 kDa active enzyme and 18 kDa propeptide, the effects of these two products on the transformed phenotype of RS485 cells were then directly assessed in the absence of suramin. Here we report, for the first time, that the lysyl oxidase propeptide, and not the lysyl oxidase enzyme, inhibits ras-dependent transformation as determined by effects on cell proliferation assays, growth in soft agar, and Akt-dependent induction of NF-kappaB activity. Thus, the lysyl oxidase propeptide, which is released during extracellular proteolytic processing of pro-lysyl oxidase, functions to inhibit ras-dependent cell transformation.

Life and death in mammalian cell culture: strategies for apoptosis inhibition

Mammalian cell culture is widely used to produce valuable biotherapeutics including monoclonal antibodies, vaccines and growth factors. Industrial cell lines such as Chinese hamster ovary (CHO), mouse myeloma (NS0), baby hamster kidney (BHK) and human embryonic kidney (HEK)-293 retain many molecular components of the apoptosis cascade. Consequently, these cells often undergo programmed cell death upon exposure to stresses encountered in bioreactors. The implementation of strategies to control apoptosis and enhance culture productivities represents a major goal of biotechnologists. Fortunately, previous research has uncovered many intracellular proteins involved in activating and inhibiting apoptosis. Here, we summarize three apoptotic pathways and discuss different environmental and genetic methodologies implemented to limit cell death for biotechnology applications.