CHO工程细胞 (11G-S) 悬浮培养的无血清培养基的设计

以悬浮适应的表达重组尿激酶原 (Pro-urokinase,pro-UK) CHO工程细胞系11G-S为对象,采用Plackett-Burman实验设计及响应面分析法,设计支持CHO工程细胞 (11G-S) 悬浮生长的无血清培养基。以细胞密度为评价指标,在单因素实验的基础上采用Plackett-Burman实验设计对影响细胞生长的培养基添加成分进行考察,确定了3种对细胞生长明显促进作用的培养基添加成分：胰岛素、转铁蛋白及腐胺。继而利用响应面法分析了这3种添加成分的最佳水平范围,设计了一种适用于CHO工程细胞 (11G-S) 悬浮培养的无血清培养基SFM-CHO-S。11G-S细胞在SFM-CHO-S批次悬浮培养的细胞最大生长密度达到4.12×106 cells/mL,pro-UK的最大累积活性达到5 614 IU/mL,培养效果优于商品化的同类无血清培养基。     

Serum-free production of recombinant proteins and adenoviral vectors by 293SF-3F6 cells

This article describes the step-wise approach undertaken to select a serum-free medium (SFM) for the efficient production of a recombinant adenoviral vectors expressing beta-galactosidase (Ad5 CMV-LacZ), in the complementing human embryonic kidney 293S cells. In the first step, a 293S-derived transfectoma, secreting a soluble epidermal growth factor receptor sEGFr (D2-22), was used to estimate the potential of selected serum-free formulations to support the production of a recombinant protein as compared to serum-containing medium. Assays showed that only one among six commercial serum-free formulations could support both sEGFr production and cell growth in static or suspension culture. In commercially available calcium-containing serum-free formulations, the cell aggregates reached up to 3 mm in diameter. In the second step, 293S cells were gradually adapted to a low-calcium version of the selected medium (LC-SFM). Cells were cloned, then screened according to their ability to grow at a rate and an extent comparable to parental cells in serum-containing medium (standard) as single cells or small aggregates. The 293SF-3F6 clone, first adapted to and then cloned in the selected serum-free medium, was selected for further experiments. Bioreactor run performed with the 293SF-3F6 clone showed similar growth curve as in the shake-flask controls. In the final step, the recombinant viral vector productivity of the 293S cells and the 293SF-3F6 clone was tested. The 293SF-3F6 cells infected by Ad5 CMV-LacZ in 3 L-scale bioreactor maintained the specific productivities of both beta-galactosidase and adenoviral vector equivalent to the shake-flask controls in suspension culture. Results from this study clearly demonstrate that the 293SF-3F6 cell line thus selected may be used either for establishing stable transfected cell line or for the production of adenoviral vectors required for gene therapy studies.     

适于无血清贴壁培养的抗凋亡宿主细胞系CHO-IVB2的构建

应用无血清培养基培养CHO细胞时,由于没有血清提供各种贴壁因子,细胞以悬浮的方式生长。在实际的大规模细胞培养中,CHO细胞往往以贴壁方式培养,要么贴壁于悬浮的微载体中,要么贴壁于固定的聚酯盘状介质或中空纤维中,而很少直接悬浮于培养基中。在无血清培养基中,Vitronectin单一组分可以促使CHO细胞的贴壁和扩增。通过双表达lgf-1和Bcl-2基因,已经构建了可以在无蛋白培养基IMEM中抗凋亡生长的细胞株CHO-IB3。在此基础上,构建了可以同时表达Igf-1、Vitronectin和Bcl-2三个蛋白的三顺反子表达载体pCI—NII—IVB。将该载体转染于CHO—dhfr^-细胞中,构建了一个细胞株CHO—IVB2。该细胞株可以在无蛋白培养基中抗凋亡生长,适于以贴壁的方式大规模培养,用于大量生产外源目的蛋白。     

Differentiation of mouse embryonic stem cells into dental epithelial-like cells induced by ameloblasts serum-free conditioned medium

Embryonic stem cells (ESCs) possess an intrinsic self-renewal ability and can differentiate into numerous types of functional tissue cells; however, whether ESCs can differentiate toward the odontogenic lineage is still unknown. In this study, we developed an efficient culture strategy to induce the differentiation of murine ESCs (mESCs) into dental epithelial cells. By culturing mESCs in ameloblasts serum-free conditioned medium (ASF-CM), we could induce their differentiation toward dental epithelial cell lineages; however, similar experiments with the tooth germ cell-conditioned medium (TGC-CM) did not yield effective results. After culturing the cells for 14 days in the differentiation-inducing media, the expression of ameloblast-specific proteins such as cytokeratin (CK)14, ameloblastin (AMBN), and amelogenin (AMGN) was markedly higher in mESCs obtained with embryoid body (EB) formation than in mESCs obtained without EB formation. We observed that immunocompromised mice implanted with induced murine EBs (mEBs) showed tissue regenerative capacity and produced odontogenic epithelial-like structures, whereas those implanted with mSCE monolayer cells mainly formed connective tissues. Thus, for the first time, we report that ASF-CM provides a suitable microenvironment for inducing mESC differentiation along the odontogenic epithelial cell lineage. This result has important implications for tooth tissue engineering.     

Isolation and analysis of a baculovirus vector that supports recombinant glycoprotein sialylation by SfSWT-1 cells cultured in serum-free medium

The inability to sialylate recombinant glycoproteins is a critical limitation of the baculovirus-insect cell expression system. This limitation is due, at least in part, to the absence of detectable sialyltransferase activities and CMP-sialic acids in the insect cell lines routinely used as hosts in this system. SfSWT-1 is a transgenic insect cell line encoding five mammalian glycosyltransferases, including sialyltransferases, which can contribute to sialylation of recombinant glycoproteins expressed by baculovirus vectors. However, sialylation of recombinant glycoproteins requires culturing SfSWT-1 cells in the presence of fetal bovine serum or another exogenous source of sialic acid. To eliminate this requirement and extend the utility of SfSWT-1 cells, we have isolated a new baculovirus vector, AcSWT-7B, designed to express two mammalian enzymes that can convert N-acetylmannosamine to CMP-sialic acid during the early phase of infection. AcSWT-7B was also designed to express a model recombinant glycoprotein during the very late phase of infection. Characterization of this new baculovirus vector showed that it induced high levels of intracellular CMP-sialic acid and sialylation of the recombinant N-glycoprotein upon infection of SfSWT-1 cells cultured in serum-free medium supplemented with N-acetylmannosamine. In addition, co-infection of SfSWT-1 cells with AcSWT-7B plus a conventional baculovirus vector encoding human tissue plasminogen activator resulted in sialylation of this recombinant N-glycoprotein under the same culture conditions. These results demonstrate that AcSWT-7B can be used in two different ways to support recombinant N-glycoprotein sialylation by SfSWT-1 cells in serum-free medium. Thus, AcSWT-7B can be used to extend the utility of this previously described transgenic insect cell line for recombinant sialoglycoprotein production.     

Evaluation of a Serum-free Medium for the Production of rAAV-2 using HeLa Derived Producer Cells

During the last decade, recombinant AAVs have become of increasing interest for gene therapy. Clinical trials have been conducted following promising in vivo evaluations, thus leading laboratories to adapt their production systems for larger and higher quality demands. Classical transfection protocols seem difficult and cumbersome to adapt to a bioreactor scale. The use of stable producer cells appears as an attractive alternative, as this system requires only a single infection step to induce rAAV production. Furthermore, the switch to a serum-free medium is an interesting strategy to increase the biosafety level to satisfy clinical grade requirements for gene therapy products. Here, we have combined both approaches and evaluated different rAAV producer clones in a serum-free medium. We first evaluated the cell growth in a serum-free medium and then did a partial optimisation of the medium composition to obtain vector yields as close as possible to the yields obtained in a classical serum containing medium. Different helper viruses, multiplicity of infection, times of infection and harvest have been compared in small scale cultures in order to determine the optimal settings which were then transferred and evaluated in suspension cultures in spinner flasks. The yields obtained in this system were similar to or at most 2 times lower than those obtained in a serum-containing medium. The scale-up of such a production system as well as the use of high cell density perfusion culture systems will probably lead to considerably higher yields than those obtained in a classical process.     

大规模动物细胞培养技术研究进展

利用动物细胞大规模培养技术可生产多种生物制品,为提高细胞活力和表达水平及有利于表达产物的纯化,采用有多种添加成分的无血清培养基培养细胞,选择更有利于细胞生长又可提高培养细胞密度的微载体和条件温和、易操作、气体交换速度快的生物反应器,在线监控细胞生存环境和生理活动,减少培养过程培养基中的抑制因素,可创造更适合细胞生存的环境,提高表达水平,向细胞中导入抗凋亡基因,可提高细胞活性和蛋白产量。利用多也微载体以球转球方式大规模培养动物细胞有很好的发展前景。     

Efficiently differentiating vascular endothelial cells from adipose tissue-derived mesenchymal stem cells in serum-free culture

Adipose tissue-derived mesenchymal stem cells (ASCs) have been reported to be multipotent and to differentiate into various cell types, including osteocytes, adipocytes, chondrocytes, and neural cells. Recently, many authors have reported that ASCs are also able to differentiate into vascular endothelial cells (VECs) in vitro. However, these reports included the use of medium containing fetal bovine serum for endothelial differentiation. In the present study, we have developed a novel method for differentiating mouse ASCs into VECs under serum-free conditions. After the differentiation culture, over 80% of the cells expressed vascular endothelial-specific marker proteins and could take up low-density lipoprotein in vitro. This protocol should be helpful in clarifying the mechanisms of ASC differentiation into the VSC lineage.     

Facile development of medium optimization for antibody production: implementation in spinner flask and hollow fiber reactor

Most bio-industrial mammalian cells are cultured in serum-free media to achieve advantages, such as batch consistency, suspended growth, and simplified purification. The successful development of a serum-free medium could contribute to a reduction in the experimental variation, enhance cell productivity, and facilitate biopharmaceuticals production using the cell culture process. Commercial serum-free media are also becoming more and more popular. However, the cell line secrets its own recombinant product and has special nutritional requirements. How can the composition of the proprietary medium be adjusted to support the specific cell’s metabolism and recombinant protein? This article uses statistical strategies to modify the commercial medium. A design of experiments is adopted to optimize the medium composition for the hybridoma cell in a serum-free condition. The supplements of peptone, ferric citrate, and trace elements were chosen to study their impact on hybridoma growth and antibody production using the response surface methodology. The stimulatory effect of the developed formulation on hybridoma growth was confirmed by the steepest ascent path. The optimal medium stimulated the hybridoma growth and antibody production in three diverse systems: a static plate, an agitated spinner flask, and a hollow fiber reactor. The cells in the developed serum-free medium had a better antibody production as compared to that in the commercial medium in the hollow fiber reactor. Our results demonstrated that the facile optimization for medium and antibody production was successfully accomplished in the hybridoma cells.     

Effects of phosphatidic acid on recombinant protein production by Chinese hamster ovary cells in serum-free culture

When recombinant Chinese hamster ovary (CHO) cells (ATCC CRL-8200) producing human interferon-γ (hIFN-γ) were incubated with exogenously supplied phosphatidic acid (PA) from egg yolk lecithin in a serum-free medium, PA induced increases in both the density of viable cells and concentration of hIFN-γ secreted into the medium. Dispersion of PA with a non-ionic surfactant, Tween 80, further enhanced both cell growth and hIFN-γ production. Replacement of the culture medium containing PA by fresh medium without PA in the course of a static culture did not influence cell growth indicating that PA is required to be continuously present in a serum-free medium to stimulate cell growth. Using a fresh medium containing PA for replacement resulted in significant enhancement of both cell density and hIFN-γ yield. These results suggest that PA is a promising constituent of low-protein serum-free media for the effective production of recombinant proteins.     

Modulation by extracellular matrices of monooxygenase and CYP1A1 induction in Hep G2 cells in serum-free culture

The in vitro cellular functions of differentiated cells are influenced by culture conditions. Effects of several extracellular matrices (ECMs) on cytochrome P450-dependent monooxygenases (MFOs) induction and cytochrome P4501A1 (CYP1A1) gene expression were estimated in Hep G2 cells cultured in a serum-free medium. The cells were cultured on collagen type I- and II-, fibronectin-, and matrigel-coated dishes and MFO activities were induced by the addition of 3-methylcholanthrene (MC). The induction of ethoxycoumarin O-deethylase (ECOD) and alkoxyresorufin O-dealkylase activities as well as the expression of CYP1A1 mRNA were also determined. ECOD and methoxy- and ethoxyresorufin O-dealkylase activities in Hep G2 cells were enhanced by culturing the cells using a serum-free medium on fibronectin- or matrigel-coated dishes. ECOD activity on fibronectin-coated dishes was about 3-fold higher than that using a serum-supplemented medium on untreated dishes. Furthermore, both immobilized and soluble fibronectin enhanced the induction of MFOs. The expression of CYP1A1 mRNA using fibronectin-coated dishes was about 2-fold higher than that using a serum-supplemented medium on untreated dishes. These findings suggest that the gene expression in cultured cells is greatly influenced by ECMs. By using fibronectin-coated dishes to cell culture in a serum-free medium, reproducible and highly sensitive results can be obtained in experiments using cultured cells. This revised version was published online in August 2006 with corrections to the Cover Date.     

Establishment and optimization of epithelial cell cultures from human ectocervix,transformation zone,and endocervix optimization of epithelial cell cultures

Cervical cancer is a major public health problem and research using cell culture models has improved understanding of this disease. The human cervix contains three anatomic regions; ectocervix with stratified squamous epithelium, endocervix with secretory epithelium, and transformation zone (TZ) with metaplastic cells. Most cervical cancers originate within the TZ. However, little is known about the biology of TZ cells or why they are highly susceptible to carcinogenesis. The goal of this study was to develop and optimize methods to compare growth and differentiation of cells cultured from ectocervix, TZ or endocervix. We examined the effects of different serum-free media on cell attachment, cell growth and differentiation, and cell population doublings in monolayer culture. We also optimized conditions for organotypic culture of cervical epithelial cells using collagen rafts with human cervical stromal cells. Finally, we present a step-by-step protocol for culturing cells from each region of human cervix.     

Optimization of the differentiation of human preadipocytes in vitro

This study aimed at developing an optimal protocol for proliferation and differentiation of preadipocytes that is a prerequisite for constructing an ideal biohybrid composed of viable adipose precursor cells in a three-dimensional matrix. Such an implant could represent an adequate solution for correcting soft tissue defects, e.g., extensive deep burns or tumor resections. Preadipocytes were isolated from human subcutaneous adipose tissue samples and cultured in Dulbecco's modified eagle medium (DMEM)/Ham's F12 medium (F12) or OPTIMEM medium with or without the addition of human serum (hS) or fetal calf serum (FCS). The advantages of fibronectin-coated culture dishes for preadipocyte yield after isolation and differentiation were evaluated. After culture expansion, differentiation was induced by insulin, isobutylmethylxanthine, pioglitazone, dexamethasone, and transferrin in the absence of serum. The extent of differentiation was assayed by measuring the activity of glycerophosphate dehydrogenase as well as counting of differentiated versus undifferentiated cells. Our results show that fibronectin coating does not only strongly increase the yield of preadipocytes after isolation from adipose tissue but also significantly enhances differentiation of precursor cells to mature adipocytes. For optimal cell expansion, DMEM/F12 is more promoting than OPTIMEM and culturing with FCS shows a slightly better proliferation compared with hS supplementation. Differentiation, in contrast, is significantly improved when hS is used instead of FCS during proliferation. Our results smooth the way for autologous preadipocyte culturing and show that hS for preadipocyte culturing opens new and promising perspectives for adipose tissue engineering by optimizing in vitro expansion in cell culture and inducing substantial differentiation.     

Rice bran extract affects differentiation of mesenchymal stem cells potency into osteogenic cells

As rice bran contains various nutrients and other proteins of which a part has biological effects on animal cells, we tested the effect of rice bran extract on rat mesenchymal stem cells (rMSCs) obtained from bone marrow. These rMSCs are pluripotent and can be readily induced to differentiate into a number of cell types, including bone and cartilage. rMSC was aggregated by culturing in serum-free condition with rice bran extract, but was not aggregated by culturing in serum-free condition or in serum-containing medium. Moreover, the longer aggregates of rMSCs were cultured in serum-free condition with rice bran extract, the more the aggregates grew. After two passages in serum-free conditions, rMSCs lost their potency for differentiation into osteogenic cells; however, the addition of rice bran extract to serum-free medium successfully prevented the loss of this ability for differentiation. In addition, MSC makers CD105 and CD166 gene expression in serum-free condition with rice barn extract corresponded to these expressions in serum-containing medium. This result suggests that certain factors in rice bran could be bioactive and contribute toward retaining the ability of MSCs to differentiate into osteogenic cells after passaging.     

Enhancement of productivity of recombinant α-amidating enzyme by low temperature culture

We have produced a recombinant C-terminal α-amidating enzyme (799BglIIα-AE) derived from Xenopus laevis by culturing a CHO cell line named 3μ-1S. Recently, we demonstrated that culturing 3μ-1S cells at a temperature below 37 °C led to the following phenomena: inhibited cell growth with high viability, enhanced cellular productivity (maximally at 32 °C), and suppressed medium consumption and release of impurities from the cells. Therefore, it is suggested that the 799BglIIα-AE production will be increased by culturing a sufficient number of the cells at a low temperature (especially at 32 °C). To assess this effect on batch and perfusion cultures, the culture temperature was shifted from 37 to 32 °C in the mid-exponential phase in the case of batch culture and from 37 to 34 °C when the cell density became high enough in the case of perfusion culture. Application of the low temperature culture to batch and perfusion cultures was effective in comparison with the culture at 37 °C: the productivity per medium and the productivity per time were increased severalfold with enhanced cellular productivity at a low culture temperature. The low temperature culture also increased the relative content of 799BglIIα-AE in the supernatant and reduced the glucose consumption. The method presented here would contribute to production of bioactive proteins using other recombinant cell lines. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of recombinant proteins in serum-free media

The advantages of serum-free culture for the manufacture of recombinant biopharmaceuticals from mammalian cells are reviewed. The process favoured is fed-batch serum-free cell culture. This process is applicable to the majority of cell lines, is practical on the large scale, gives the lowest manufacturing cost, and can b e carried out without the use of any serum.The advantages of serum-free culture for the manufacture of recombinant biopharmaceuticals from mammalian cells are reviewed. The process favoured is fed-batch serum-free cell culture. This process is applicable to the majority of cell lines, is practical on the large scale, gives the lowest manufacturing cost, and can be carried out without the use of any serum.     

Serum- and protein-free media formulations for the Chinese hamster ovary cell line DUKXB11

The production of therapeutic proteins in mammalian cell lines is of outstanding importance. The maintenance of most mammalian cell lines in culture requires the addition of serum to the culture medium. The elimination of serum from mammalian cell culture is desirable since serum is expensive and a source of contaminants, e.g. viruses, mycoplasma or prions. Here we describe the composition of serum- and protein-free media for the Chinese hamster ovary (CHO) cell line DUKXB11. The serum-free formulation supports excellent growth of CHO DUKXB11 cells at low (23cells/cm2) and high (2 x 10(4) cells/cm2) seeding densities characterized by a generation time of 10-12h, and, after addition of 0.2% pluronic F-68, the growth of a recombinant suspension cell line derived from DUKXB11. In addition, this formulation also allowed us to adapt recombinant cell lines expressing various amounts of human antithrombin ATIII (ATIII) to serum-free conditions. Secretion of ATIII was readily observed in the serum-free medium. Minor changes to the serum-free formulation resulted in a protein free formulation that supported growth of CHO DUKXB11 cells, growth of recombinant CHO cells expressing ATIII, and production of ATIII.     

Long-term-cultured mouse B-lymphocyte line. II. Modulation of Ia-antigen expression on B-lymphocyte line

Mouse B-cell line, established by culturing anti-Thy-1 and complement-treated splenic B cells with concanavalin A-stimulated conditioned medium, expressed immunoglobulins and Ia antigens on its surface. The long-term-cultured B-cell line was split in two and maintained with or without 3300 R X-irradiated T-cell-depleted syngeneic splenic adherent cells (SAC). Interestingly, the B-cell line cultured without SAC lost its Ia antigen but not its Ig expression, whereas the cell line with SAC maintained both Ia and Ig expression. The ability to express Ia antigens was restored by culturing them only in the presence of Ia-positive feeder cells. Neither recombinant interferon-gamma or lectin-stimulated conditioned medium nor cell-free culture supernatant SAC had the ability to restore Ia antigen expression on the B-cell line. Incubation of Ia-negative B-cell line with phorbol esters restored the Ia expression. It is suggested that the expression of Ia antigen on B lymphocytes was controlled differently from that on macrophage lineage. The B-cell line expressing Ia antigens acts as stimulator cells for alloantigen-activated T lymphocytes and as antigen-presenting cells on the KLH-specific Ia-restricted proliferative T-cell clone in the presence of a specific antigen.     

Guidelines for cultivation and preservation of the serum-free cell line McCoy-Plovdiv

In this paper, we offer detailed information concerning manipulations with the novel serum-free cell line McCoy-Plovdiv. Guidelines for procedures as trypsinization of the monolayer, subculturing, as well as freezing and thawing conditions are proposed. Our results give us grounds to assume that this is a cell line entirely serum-independent at any step of the process of culturing and preservation. The serum-free cell line McCoy-Plovdiv enriches the collection of mammalian serum-free cell lines. The easier cultivation, the lower expenses and the higher sensitivity in comparison with the serum-supplemented McCoy cells are discussed as possibilities for broad applications of McCoy-Plovdiv cells in different types of laboratory investigations. This revised version was published online in July 2006 with corrections to the Cover Date.