Effect of different fetal bovine serum concentrations on the replicative life span of cultured chick cells

Summary The effect of Eagle's minimal essential medium, containing different fetal bovine serum (FBS) concentrations, on the proliferation and replicative life span of cultured chick cells has been studied. Our results showed that the rate of chick cell proliferation and the cell density at stationary phase increased as a function of serum concentration between 5 and 30% FBS. The replicative life span of cultured chick cells was dependent on the FBS concentration between 5 and 20% in a medium volume of 0.20 ml/cm². The maximum replicative life span of chick cells was obtained by serially propagating cells in a medium volume of 0.20 ml/cm² containing 20 or 30% FBS, or, alternatively, in 0.53 ml/cm² containing 10, 20 or 30% FBS. Cells grown in medium containing 5% serum had a calendar life span of 35 days, whereas cells propagated in medium containing higher serum concentrations had a calendar life span of 50 days. These results reenforce the concept that, although the kinetics of cell population aging can be affected by the culture medium composition, the aging of cells in culture is controlled by alterations within the cell. This work was supported by IIT Research Institute.     

Optimization of culture conditions for endothelial progenitor cells from porcine bone marrow in vitro

Objectives: The aim of this study was to determine an optimal culture method for porcine bone marrow‐derived endothelial progenitor cells (EPCs). Materials and methods: Mononuclear cells (MNCs) were isolated by density centrifugation and differentiated into EPCs in in vitro. At first‐passage, EPCs were cultured at different cell densities (5 × 10³, 1 × 10⁴, 2 × 10⁴ or 5 × 10⁴/cm²) and in basic medium (EGM, medium 199, DMEM or 1640) supplemented with FBS (2%, 5%, 10% or 20%) and different combinations of cytokines (VEGF, VEGF + bFGF, VEGF + bFGF + EGF, or VEGF + bFGF + EGF + IGF), the experiment being based on L₆₄ (4²¹) orthogonal design. Results and conclusions: This demonstrated that the optimal culture method for our EPCs displayed higher expansion and migration rates as compared to other groups, by analysis of variance; that is, cultured at 1 × 10⁴/cm² in M199 supplemented with 10% FBS and VEGF + bFGF + IGF + EGF. Furthermore, percentage of positive cells stained by Dil‐ac‐LDL and FITC‐UEA‐1 was more than 65%, and as shown by immunohistochemistry, these cells also stained positively for CD133, CD34 and KDR. The present study indicates that the number and function of porcine EPCs significantly increased when using our optimized culture parameters.     

A novel technique to propagate primary human preadipocytes without loss of differentiation capacity

Objective: The study of human preadipocytes is hampered by the limited availability of adipose tissue and low yield of cell preparation. Proliferation of preadipocytes using common protocols, including fetal bovine serum (FBS), results in a markedly reduced differentiation capacity. Therefore, we were interested in developing an improved culture system that allows the proliferation of human preadipocytes without loss of differentiation capacity. Research Methods and Procedures: Adipose tissue samples were taken from subjects undergoing elective abdominal surgery. Cells were seeded at various densities and cultured using different formulations of proliferation media including factors such as fibroblast growth factor‐2 (basic fibroblast growth factor), epidermal growth factor, insulin, and FBS either alone or in combination. Cells were counted and induced to differentiate after confluence. After complete differentiation, cells were harvested, and glycerol‐3‐phosphate dehydrogenase activity was measured. Cells were subcultured for up to five passages. Results: The proliferation medium with 4 growth factors (PM4), consisting of 2.5% FBS, 10 ng/mL epidermal growth factor, 1 ng/mL basic fibroblast growth factor, and 8.7 µM insulin, resulted in lower doubling times at all seeding densities tested (0.05 × 10⁴ to 1.5 × 10⁴) compared with medium supplemented with 10% FBS. In contrast to cells in FBS medium, cells grown with PM4 medium retained full differentiation rate (glycerol‐3‐phosphate dehydrogenase activity, 493 ± 215 vs. 41 ± 17 mU/mg, p < 0.01). Differentiation capacity was fully retained at least for up to three passages in PM4 medium. Discussion: The use of PM4 medium results in substantial proliferation of human preadipocytes with preserved differentiation capacity. This novel technique represents a valuable tool for the study of human adipose tissue development and function starting from small samples.     

TGFβ (transforming growth factor β) and keratocyte motility in 24 h zebrafish explant cultures

Fish keratocytes are used as a model system for the study of the mechanics of cell motility because of their characteristic rapid, smooth gliding motion, but little work has been done on the regulation of fish keratocyte movement. As TGFβ (transforming growth factor β) plays multiple roles in primary human keratinocyte cell migration, we investigated the possible involvement of TGFβ in fish keratocyte migration. Studying the involvement of TGFβ1 in 24 h keratocyte explant allows the examination of the cells before alterations in cellular physiology occur due to extended culture times. During this initial period, TGFβ levels increase 6.2‐fold in SFM (serum‐free medium) and 2.4‐fold in SFM+2% FBS (fetal bovine serum), while TGFβ1 and TGFβRII (TGFβ receptor II) mRNA levels increase ～3‐ and ～5‐fold respectively in each culture condition. Two measures of motility, cell sheet area and migration distance, vary with the amount of exogenous TGFβ1 and culture media. The addition of 100 ng/ml exogenous TGFβ1 in SFM increases both measures [3.3‐fold (P=4.5 × 10^?5) and 26% (P=2.1 × 10^?2) respectively]. In contrast, 100 ng/ml of exogenous TGFβ1 in medium containing 2% FBS decreases migration distance by 2.1‐fold (P=1.7 × 10^?7), but does not affect sheet area. TGFβ1 (10 ng/ml) has little effect on cell sheet area in SFM cultures, but leads to a 1.8‐fold increase (P=1.5 × 10^?2) with 2% FBS. The variable response to TGFβ1 may be, at least in part, explained by the effect of 2% FBS on cell morphology, mode of motility and expression of endogenous TGFβ1 and TGFβRII. Together, these results suggest that expression of TGFβ and its receptor are up‐regulated during zebrafish keratocyte explant culture and that TGFβ promotes fish keratocyte migration.     

NuSerum,a synthetic serum replacement,supports chondrogenesis of embryonic chick limb bud mesenchymal cells in micromass culture

Summary In an effort to establish a more chemically defined culture system to study the regulation of chondrogenic differentiation in vitro, two commercially available serum replacements, NuSerum and NuSerum IV, were tested on embryonic limb mesenchyme. Limb bud (LB) mesenchymal cells were isolated from Hamilton-Hamburger stage 23–24 chick embryos and plated at various densities (1, 5, 10, or 20 × 10⁶ cells/ml) in micromass culture for 4 days in media supplemented with 10% fetal bovine serum (FBS), NuSerum or NuSerum IV. Cell growth was assessed by the incorporation of [³H]leucine and [³H]thymidine. Chondrogenesis was determined by the incorporation of [³⁵S]sulfate and by the number of Alcian blue-staining cartilage nodules. In high density (20 × 10⁶ cells/ml) cultures, which favored chondrogenic differentiation, both serum replacements supported protein synthesis and chondrogenesis equally well as FBS. In cultures plated at 5 × 10⁶ cells/ml, a cell density in which was chondrogenesis-limiting, both NuSerum and NuSerum IV significantly enhanced incorporation of [³⁵S]sulfate (2.6-fold), [³H]leucine (1.4-fold), and [³H]thymidine (1.9-fold), compared to FBS. Enhancement of chondrogenesis was also apparent by the increases in the number of Alcian blue-staining cartilage nodules and the ratio of sulfate: leucine incorporation in cultures plated at 5 × 10⁶ cells/ml. Interestingly, the localization of cartilage nodules was extended out to the periphery of micromass cultures fed with NuSerum or NuSerum IV. The observed effects of NuSerum and NuSerum IV may be attributed to a combination of factors, including lower concentrations of serum and its associated proteins, as well as supplemented growth factors and hormones known to promote cell proliferation and differentiation. Therefore, NuSerum and NuSerum IV are excellent, low-cost replacements for FBS in maintaining cellular growth and promoting chondrogenesis in LB mesenchymal cell cultures in vitro.     

Characterization of proliferation and differentiation of opossum kidney cells in a serum-free defined medium

Summary Proliferation and differentiation of opossum kidney cells in a serum-free defined medium was investigated and compared to that under conditions in which fetal bovine serum FBS (10%) was employed. Monolayers were grown in Dulbecco's modified Eagle's medium-Ham's F12 nutrient mixture containing insulin (10 μg/ml), bovine serum albumin fraction V (1 mg/ml) and fetuin (1 mg/ml). Cells in serum-free medium seeded at 1×10⁴ per cm² grew to confluency within 6 to 8 d and formed hemicysts or domes at a frequency equivalent to those in serum-containing medium. Electron microscopy of cultures grown in serum-free medium revealed polarized monolayers with the presence of microvilli and tight junctions. The differentiated characteristics, including sodium-dependent phosphate transport, the inhibition of this transport by parathyroid hormone (PTH), and the generation of cyclic AMP in response to PTH, were preserved in opossum kidney cells grown in serum-free medium.     

Reconstruction of tissue‐engineered bone with bone marrow mesenchymal stem cells and partially deproteinized bone in vitro

We have explored the optimal seeding density and timing for transplantation of the tissue‐engineered bone with BMMSCs (bone marrow mesenchymal stem cells) and PDPB (partially deproteinized bone) in vitro. Rabbit BMMSCs of different densities were seeded into PDPB generated from fresh pig vertebrates to reconstruct tissue‐engineered bone in vitro. Adhesion and proliferation of BMMSCs were analysed by MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide] assay from which growth curves of BMMSCs on the PDPB materials were generated. The data show that BMMSCs began to adhere to PDPB after 24 h of primary culture, all groups reaching peak growth on the 6th day, after which the value of A decreased gradually and reached a plateau phase. The optimal BMMSCs seeding density of 5×10⁶/ml achieved an excellent adhesion and proliferation activity on PDPB. In summary, the best cell seeding density of constructing tissue‐engineered bone with BMMSCs in vitro is 5×10⁶/ml, the optimal timing to transplant is the 6th day.     

Enhancement of Sf9 Cells and Baculovirus Production Employing Grace’s Medium Supplemented with Milk Whey Ultrafiltrate

Animal cells can be cultured both in basal media supplemented with fetal bovine serum (FBS) and in serum-free media. In this work, the supplementation of Grace’s medium with a set of nutrients to reduce FBS requirements in Spodoptera frugiperda (Sf9) cell culture was evaluated, aiming the production of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) at a cost lower than those for the production using Sf900 II medium. In Grace’s medium supplemented with glucose, Pluronic F68 (PF68) and yeast extract (YE), the effects of FBS and milk whey ultrafiltrate (MWU) on cell concentration and viability during midexponential and stationary growth phase were evaluated. In spite of the fact that FBS presented higher statistical effects than MWU on all dependent variables in the first cell passage studies, after cell adaptation, AgMNPV polyhedra production was comparable to that in Sf900 II. Batch cultivation in Grace’s medium with 2.7 g l⁻¹ glucose, 8 g l⁻¹ YE and 0.1% (w/v) PF68 supplemented with 1% (w/v) MWU and 3% (v/v) FBS increased viable cell concentration to about 5-fold (4.7×10⁶ cells ml⁻¹) when compared to Grace’s containing 10% (v/v) FBS (9.5×10⁵ cells ml⁻¹). AgMNPV polyhedra (PIBs) production was around 3-fold higher in the MWU supplemented medium (1.6×10⁷ PIBs ml⁻¹) than in Grace’s medium with 10% FBS (0.6×10⁷ PIBs ml⁻¹). This study therefore shows a promising achievement to significantly reduce FBS concentration in Sf9 insect cell media, keeping high productivity in terms of cell concentration and final virus production at a cost almost 50% lower than that observed for Sf900 II medium. C.A. Pereira is recipient of a CNPq fellowship.     

Ex vivo expansion of hematopoietic stem cells in a proliferation chamber with external stirred conditioning tank: Sequential optimization of growth factors

The insufficient number of hematopoietic stem cells (HSCs) extracted from various cell sources creates the need for the use of growth factors in the culture systems. Numerous types and concentrations of growth factors have been reported in the literature. In this study, we investigated the effect of three important hematopoietic growth factors thrombopoietin (TPO), stem cell factor (SCF), and Fms‐like tyrosine kinase‐3 ligand (Flt‐3) as well as cell‐seeding density on ex vivo expansion of human HSCs using a factorial design. Sequential optimization was then followed by methods of steepest ascent and central composite design. The optimum concentrations of growth factors were 50, 90, and 34 ng/mL for SCF, TPO, and Flt‐3, respectively, at an initial cell density of 2.5 × 10⁵ cells/mL. Effective expansion factor value (EEF) of HSCs increased considerably and revealed almost similar results when the cells were cultured in a 24‐well plate (EEF = 4.54 ± 0.43) and a proliferation chamber with an external stirred conditioning tank (PC‐ESCT; EEF = 5.1 ± 0.35) at seeding density of 2.5 × 10⁵ cells/mL after 7 days. The cells did not show considerable changes in proliferation when they were cultured in medium containing serum or in a commercial serum‐free medium at the optimum concentrations of the growth factors. The present study demonstrated the optimum condition of hematopoietic growth factors as well as the potential of PC‐ESCT for ex vivo expansion of HSCs.     

Chinese hamster ovary cells cultured in low concentrations of fetal bovine serum: Cloning efficiency,growth in suspension,and selection of drug-resistant mutant phenotypes

Summary Reducing serum concentrations in media provides a potential cost advantage. To determine whether such media could be used for applied mutagenesis assays, we measured cloning efficiency and growth parameters in suspension of Chinese hamster ovary cells cultured in reduced serum with or without additives (1 μg/ml insulin, 3×10⁻⁷ M linoleic acid, 1×10⁻⁸ M H₂SeO₃) or bovine serum albumin (BSA, 1% wt/vol). With the additives and ≤0.5% fetal bovine serum (FBS), Ham’s F12 medium (without hypoxanthine and thymidine) was more optimal than alpha Eagle’s minimum essential medium (MEM) (without ribosides and deoxyribosides) for low density cloning and high density suspension growth. Acceptable cloning efficiencies were obtained with 2% FBS plus BSA without additives in either medium; the addition of BSA resulted in improved colony size and more compact colony morphology. In alpha MEM, satisfactory growth rates and maximum saturation densities in suspension culture were obtained only with 5% FBS; in Ham’s F12, 1% FBS+deoxycytidine+BSA yielded satisfactory suspension growth. Spontaneous mutant frequencies were compared for each medium containing 10% dialyzed FBS (DFBS), 1% FBS plus BSA, or 2% FBS plus BSA. The spontaneous frequency of azaadenine-resistant phenotypes (mutant at theaprt locus) in 1% FBS plus BSA was significantly lower than the frequency observed in 2% FBS plus BSA or 10% DFBS. Frequencies of spontaneous mutants resistant to thioguanine (hgprt locus) or fluorodeoxyuridine (tk locus) were similar with 10% DFBS, 1% FBS plus BSA, or 2% FBS plus BSA. Compared to alpha MEM with 10% DFBS, frequencies of drug-resistant mutants induced by ethyl methanesulfonate or mitomycin C (MMC) were not significantly lower in alpha MEM with 2% FBS plus BSA; observed mutant frequencies induced by dimethyl-nitrosamine or benzo(a)pyrene seemed to be decreased at lower survival levels. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-ENG-48 and supported by the Environmental Protection Agency under Interagency Agreements IAG-D5-E681-AN and AO.     

Differential growth factor responses of epithelial cell cultures derived from normal human prostate,benign prostatic hyperplasia,and primary prostate carcinoma

Because of a lack of information of the optimum nutritional requirements, epithelial cells derived from normal human prostate and prostate tumors have been difficult to propagate in vitro, which hinders research in prostate carcinogenesis. In an effort to establish optimum nutritional conditions and differences in growth characteristics of normal human prostate (NP), benign prostatic hyperplasia (BPH), and prostatic carcinoma (PCA), we have compared the effects of several growth factors on cell proliferation and elucidated growth properties of low passage epithelial cells derived from NP, BPH, and PCA of an African-American patient. Primary and low passage cultures were propagated in serum-free keratinocyte basal medium (KBM) supplemented with insulin (5 μg/ml), hydrocortisone (0.5 μg/ml), epidermal growth factor (EGF, 10 ng/ml), bovine pituitary extract (BPE; 50 μg/ml), cholera toxin (10 ng/ml), and antibiotics. Almost all NP, BPH, and PCA cells were positive for cytokeratins and prostate-specific antigen (PSA). The NP, BPH, and PCA cells were essentially diploid and lacked mutations in c-K-ras and c-Ha-ras oncogenes, and p53 tumor suppressor gene. However, they exhibited progressively accelerating growth parameters. The population doubling times of NP, BPH and PCA were 51 hr, 37 hr, and 29 hr, respectively; their saturation densities were 2.9 × 10⁴/cm², 3.3 × 10⁴/cm², and 7.2 × 10⁴/cm², respectively. The NP and BPH cells required all of the growth factors in the medium, as deletion of any one of the above factors strongly inhibited their growth. The PCA cells, however, were independent of EGF and hydrocortisone. PC-3, an established human prostate cancer cell line, was independent of the growth factors tested. Fetal bovine serum (FBS) inhibited the growth of NP, BPH and PCA cells. In contrast, FBS stimulated the growth of the PC-3 cells in a concentration-dependent manner. These results indicate that in the absence of any apparent karyotype alterations and mutations in c-K-ras, c-Ha-ras and p53 genes, epithelial cells derived from NP, BPH, and PCA exhibit significant differences in their growth properties and responses to growth factors. These variations may represent early changes involved in prostate cancer, while gene mutations and cytogenetic alterations occur in advanced and/or metastatic tumors. © 1996 Wiley-Liss, Inc.     

Structurally and functionally characterized in vitro model of rabbit vocal fold epithelium

In this paper, we describe a method for primary culture of a well differentiated electrically tight rabbit vocal fold epithelial cell multilayer and the measurement of transepithelial electrical resistance (TEER) for the evaluation of epithelial barrier function in vitro. Rabbit larynges were harvested and enzymatically treated to isolate vocal fold epithelial cells and to establish primary culture. Vocal fold epithelial cells were co-cultured with mitomycin C-treated feeder cells on collagen-coated plates. After 10–14 days in primary culture, cells were passaged and cultured until they achieved 70–90% confluence on collagen-coated plates. Epithelial cells were then passaged onto collagen-coated cell culture inserts using 4.5 cm² membrane filters (1.0 μm pore size) with 10% fetal bovine serum or 30 μg/mL bovine pituitary extract to investigate the effects of growth-promoting additives on TEER. Additional experiments were performed to investigate optimal seeding density (1.1, 2.2, 4.4, or 8.9 × 10⁵ cells/cm²), the effect of co-culture with feeder cells, and the effect of passage number on epithelial barrier function. Characterization of in vitro cultures was performed using hematoxylin and eosin staining and immunostaining for vocal fold epithelial cell markers and tight junctions. Results revealed higher TEER in cells supplemented with fetal bovine serum compared to bovine pituitary extract. TEER was highest in cells passaged at a seeding density of 2.2 × 10⁴ cells/cm², and TEER was higher in cells at passage two than passage three. Ultrastructural experiments revealed a well-differentiated epithelial cell multilayer, expressing the epithelial cell markers CK13, CK14 and the tight junction proteins occludin and ZO-1.     

Effect of serum,fibronectin, and laminin on adhesion of rabbit intestinal epithelial cells in culture

Rabbit intestinal epithelial cells, obtained after a limited hyaluronidase digestion, were incubated in medium with or without calf serum, on bacteriological plastic dishes. The dishes, either plain or coated with an air-dried type I collagen film, were pretreated with medium alone or with medium containing purified laminin or purified fibronectin. Cells did not attach in significant numbers to untreated bacteriological plastic, even in the presence of serum. Cells did attach to collagen-coated dishes, and were judged viable on the basis of their incorporation of radiolabeled leucine into cell protein. Cell adhesion to the collagen substrate increased in proportion to the concentration of serum in the medium, with maximal attachment at 5% serum or greater. Pretreatment of plain or collagen-coated dishes with increasing amounts of fibronectin enhanced cell adhesion in a concentration-dependent manner. Either serum, or fibronectin-free serum in the medium enhanced cell attachment to substrates pretreated with cither fibronectin or laminin. Thus, intestinal epithelial cells appear to possess surface receptors for both laminin and fibronectin. The evidence further suggests that calf serum may contain factors, other than fibronectin, capable of enhancing intestinal epithelial cell attachment to collagen substrates.     

Regulation of cell attachment and cell number by fibronectin and laminin

We have examined the effect of laminin and fibronectin on the attachment and growth on type IV collagen of a line of mouse epithelial cells and a strain of adult human fibroblasts. Laminin stimulated attachment of the epidermal cells and fibronectin stimulated fibroblast attachment. At high concentrations (100 micrograms/ml), the attachment proteins altered the growth of cells in culture. The epidermal cells grew better in media containing fibronectin-free serum supplemented with laminin. Fibroblasts, on the other hand, grew best in media containing serum supplemented with fibronectin. These data suggest that laminin promotes epithelial cell growth whereas fibronectin promotes fibroblast growth. This observation was confirmed when these cells were cocultured in the presence of the attachment proteins or of their respective antibodies. The mouse epidermal cells grew best when laminin was added to cocultures of fibroblasts and epithelial cells. Fibroblasts grew best in the presence of antibody to laminin and poorly in the presence of antibody to fibronectin. Thus, fibronectin and laminin may participate in the regulation of cell populations in vivo and may be involved in epithelial-mesenchymal interactions.     

Sodium fluxes in human fibroblasts: Effect of serum,Ca+2, and amiloride

Human fibroblasts that have been serum deprived for 4 hours have a digitoxin-insensitive Na influx of 9.5 ± 1.0 (n = 4) μmol/g prot/min which is not significantly different from the influx of 9.4 ± 0.6 (n = 3) μmol/g prot/min measured in cells arrested in the G₁/G₀ state by serum-deprivation for a period of four days. The Na influx in serum-deprived cells is rapidly stimulated (within one minute) simply by assaying the cells in medium containing 10% fetal bovine serum (FBS). The digitoxin-insensitive Na influx for cells in the presence of 10% FBS is 22.9 ± 1.1 (n = 6) μmol/g prot/min. the stimulation of Na influx in serumdeprived cells can also be achieved by the addition of the purified mitogen, epidermal growth factor (EGF). Addition of EGF to serum-deprived cells gives a maximal stimulation of Na influx of approximately 1.6-fold, with the concentration for half-maximal stimulation being 7.5 ng/ml. The stimulation of Na influx results from the activation of an amiloride-sensitive pathway, which appears to be minimally active in serum-deprived cells. Kinetic analysis of Na influx experiments in the presence of 10% FBS and varying concentrations of amiloride indicate that at infinite concentrations of amiloride the Na flux would be reduced to 8.9 μmol/g prot/min, which is comparable to the level of Na flux measured in serum-deprived cells in the presence of 5 mM amiloride. Thus, amiloride can totally inhibit the serum-stimulated component of Na influx while inhibiting less than 10% of the Na influx in serum-deprived cells. The Na influx in serum-deprived cells can also be stimulated 2.5-fold by preincubating cells in the presence of the Ca⁺ ionophore A23187 to elevate the intracellular Ca content. This stimulation of Na influx by intracellular Ca⁺² can be virtually eliminated by adding 1 mM amiloride.     

Modulation of hybridoma cell growth and antibody production by coating cell culture material with extracellular matrix proteins

The influence of coating polystyrene tissue culture plates with different proteins on murine hybridoma cell growth and antibody production was investigated. Fibronectin, collagen I, bovine serum albumin and laminin were used to coat NUNC^® and COSTAR^® cell culture plates. Cell number and antibody concentration in culture fluids were quantified as indicators for cell viability, proliferation and productivity. Adhesive behaviour, morphology, expression of surface receptors of hybridoma cells and the presence of tyrosine-phosphorylated proteins in cell lysates were characterized by cell adhesion experiments, microscopy, flow cytometry and Western Blot analysis.It was shown that coatings with fibronectin (0.2 μg/ml) lead to a substantial improvement of cell growth by 50–70% and an increase of monoclonal antibody production by 100–120%.Collagen I coatings showed an improvement in cell growth by 30–70% and by 60% for the production of monoclonal antibodies. Coatings with BSA and laminin had minor effects on these parameters. It was found that the hybridoma cell lines used in this study did not express the α₂-chain of the α₂β₁-integrin, which is responsible for binding to collagen and laminin.However, the presence of β₁-integrin on the cell surface was shown, which should enable hybridoma cells to bind fibronectin. We propose, therefore, that fibronectin adsorption to cell culture materials may be a promising approach to enhance the production of monoclonal antibodies by cultivated hybridoma cells.     

Establishment and conditions for growth and differentiation of a myoblast cell line derived from the semimembranosus muscle of newborn piglets

To establish an adequate model to study the proliferation and differentiation of porcine skeletal muscle in response to bioactive compounds, a pool of satellite cells was derived from the semimembranosus muscle (SM) of newborn piglets using a Percoll gradient centrifugation. The final yield amounted to 4.1 × 10⁶ cells/g muscle tissue. The percentage of muscle satellite cells has been determined by immunostaining for desmin and subsequent fluorescence analysis by flow cytometry, which revealed 95% of desmin-positive cells. For proliferation studies, satellite cell born myoblasts were seeded in gelatin-coated 96-well microplates at about 5 × 10³ cells per well. Cells were grown for 1 day in MEMα plus 10% fetal bovine serum (FBS) and 10% horse serum (HS), followed by 2 d cultivation in serum-free growth medium. For differentiation studies, myoblasts were cultured in matrigel-coated 24-well plates for 4 d with growth medium containing 10% FBS and 10% HS. At 80% confluence, cells were grown for 24 h in medium plus 10% FBS and 1 μM insulin to initiate differentiation. Subsequently, the cells were cultured in serum-free differentiation medium (SFDM) for 3 d to form myotubes. Cultures reached a maximum fusion rate of approximately 20% after 96 h. By establishing this culture system, we provide an advanced and appropriate in vitro model to study porcine skeletal muscle cell growth and differentiation including the responses to various bioactive compounds.     

Optimization of primary culture condition for mesenchymal stem cells derived from umbilical cord blood with factorial design

Mesenchymal stem cells (MSCs) can not only support the expansion of hematopoietic stem cells in vitro, but also alleviate complications and accelerate recovery of hematopoiesis during hematopoietic stem cell transplantation. However, it proved challenging to culture MSCs from umbilical cord blood (UCB) with a success rate of 20–30%. Many cell culture parameters contribute to this outcome and hence optimization of culture conditions is critical to increase the probability of success. In this work, fractional factorial design was applied to study the effect of cell inoculated density, combination and dose of cytokines, and presence of serum and stromal cells. The cultured UCB‐MSC‐like cells were characterized by flow cytometry and their multilineage differentiation potentials were tested. The optimal protocol was identified achieving above 90% successful outcome: 2 × 10⁶ cells/mL mononuclear cells inoculated in Iscove's modified Dulbecco's medium supplied with 10% FBS, 15 ng/mL IL‐3, and 5 ng/mL Granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). Moreover, the UCB‐MSC‐like cells expressed MSC surface markers of CD13, CD29, CD105, CD166, and CD44 positively, and CD34, CD45, and human leukocyte antigens‐DR (HLA‐DR) negatively. Meanwhile, these cells could differentiate into osteoblasts, chondrocytes, and adipocytes similarly to MSCs derived from bone marrow. In conclusion, we have developed an efficient protocol for the primary culture of UCB‐MSCs by adding suitable cytokines into the culture system. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Optimization of a MRC-5 Cell Culture Process for the Production of a Smallpox Vaccine

A cell culture process adaptable to produce smallpox vaccine at large scale has been developed. To achieve this, Design of Experiments (DOE) was applied to identify and optimize critical cell culture process parameters for MRC-5 cell growth and recovery during cell expansion. For cell growth, a 2^5?1 partial factorial (two level, five factor, 16 conditions) study was designed to evaluate the effects of basal media, seeding density, culture volume, feeding frequency and serum concentration on population doubling level (PDL) after 6–7 days in adherent T-flask cultures. Results indicated that lowering the cell density to 1×10⁴ cells/cm², increasing the culture volume to 0.5 ml/cm² and increasing serum concentration to 20% significantly improved cell expansion. These findings correlated with PDLs above 2.0 and cell densities above 1×10⁵ cells/cm² at the end of the study period. For cell recovery at passaging, a similar DOE was used to evaluate the effect of trypsin concentration, solution temperature, duration of treatment, incubation temperature and duration of standing time between quenching and reseeding. By increasing the trypsin treatment duration to 60 min and lowering the standing time between quenching and reseeding to within 1 h, the recovery of the MRC-5 cells was greatly improved. By using these newly defined conditions, a two-fold improvement in cell expansion was consistently achieved in both roller bottles and 10 layer Nunc^® Cell Factories (Cell Factories). Application of these new conditions for current Good Manufacturing Practices (cGMP) production of MRC-5 cell banks and clinical material demonstrated predictably high cell expansion as well as significantly higher production of vaccinia virus, thus providing the basis for manufacturing vaccinia virus at large scale. These findings demonstrate the need for cell culture optimization and the effectiveness of DOE to rapidly define processes suitable for cGMP manufacturing of a smallpox vaccine or other viral vaccine products.     

Polarity, Protrusion–Retraction Dynamics and Their Interplay during Keratinocyte Cell Migration

Keratinocyte migration on a two-dimensional substrate can be split into four distinct phases: cell extension, attachment, contraction, and detachment. It is preceded by polarization of the cell which leads to a functional asymmetry observable by the formation of a leading lamella. In this work variation of fibronectin coating concentrations and competitive inhibition with RGD peptides are used to investigate the dependency of polarization, migration, lamella dynamics, and ruffling on substrate adhesiveness. Looking at migrating human epidermal keratinocytes with a well-defined polarity we find that a fibronectin-coating concentration of 10 μg/cm² stimulates migration and ruffling speed twofold, whereas protrusion speed increases only by 20% (compared to 2.5 μg/cm² fibronectin). Nonpolar cells show a constant migration and ruffling speed independent of the amount of fibronectin. In contrast protrusion speeds of polar and nonpolar cells are equal. Treatment of cells on 10 μg/cm² fibronectin with 1 mg/ml GRGDS reduces the characteristic migration, protrusion, and ruffling speed of polar cells which corresponds to lowering the effective coating concentration to under 5 μg/cm². The probability of being polarized (quantified by a polarity index) increases with increasing fibronectin concentration. However, addition of soluble RGD on 10 μg/cm² fibronectin does not simply reduce the polarity index like one would expect from the corresponding changes in the other motility parameters, but it remains unchanged.