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Animal Cell CultureAnimal Cell CultureAnimal Cell Culture

Prof. S.T. YangDept. Chemical & Biomolecular Eng.

The Ohio State University

Animal Cell Culture Applications

Animal Cell Culture Animal Cell Culture ApplicationsApplications

• Production of recombinant proteins • Production of MAb - Hybridoma• Study of cell biology• Tissue engineering - artificial organs • in vitro cell toxicity and drug screening

Cell culture vs. AnimalCell culture vs. Animal

• Advantages– Consistency and reproducibility results– understanding the effects of a particular

compound on a specific cell type (e.g., liver cells)– avoid contaminants

• Disadvantages– cell characteristics can change (growth and

biochemical)– cell may need to adapt to nutrients

Animal Cell BioprocessingAnimal Cell Bioprocessing• Problems for large-scale animal cell cultures

(compared to microorganism)– Minimum inoculum size: ~105/ml or 1-5x104/cm2

– low cell proliferation rate: tg = 12 - 48 h– low productivity of target products– high medium costs (serum)– low resistance to toxic metabolites (ammonia,

inhibit growth or lactic acid, change in pH)– higher sensibility to outer stimuli, higher

susceptibility to shear stress (only thin & soft cell membrane of lipid bilayer)

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Products from Mammalian Cell CulturesProducts from Mammalian Cell Cultures

Annals New York Academy of Sciences, 356

• Group I: cells as end products– Artificial skin– Artificial organs

• Beta-islet cells (pancreas)• Hepatocytes (liver)

– Bone marrow– Lymphocytes– Gene/cell theraphy

• Group II: cell-derived products– Growth factors

• Nerve growth factor, Epidermal growth factor– Proteases (Urokinase, etc.) – Hormones

• Human growth hormone, Insulin, Calcitonin, Parathyroid hormone

– Monoclonal antibodies• single type of antibody binds to specific

compounds selectively.• Used in diagnostic and therapeutic agents

– Vaccines• Polio, Measles, Mumps, Rubella, Yellow

fever, Rabies, Influenza– Recombinant Glycoproteins (Cytokines)

• Interferons, block virus replication• Blood clotting factors (VIII, IX)• Glycoprotein hormone, EPO• Plasminogen activators

Cell TypesCell Types

• Epithelial (skin)

• Fibroblast (most widely used, bone cartilage and fibrous matrix for body)

• Muscle

• Neuron

• Blood and lymph (cells in suspension)

20 μm

• Anchorage-independent– Blood cells– Cancer cells– Hybridoma cells - Produce MAb (monoclonal

antibody)

• Anchorage-dependent – Need solid surface to support growth– Primary cells– Chinese hamster ovary (CHO) cells - Produce

glycosylated recombinant proteins

Animal CellsAnimal CellsAnimal cells Animal cells -- characteristicscharacteristics

• Unicellular organisms (microbes) – proliferate until stop signal is detected

• Multicellular organisms – proliferation is tightly regulated– Some cells never divide – nerve, muscle cells– Some cells are always dividing – stem cells– Some cells don’t normally divide unless stimulated –

fibroblasts – wound recovery– Loss of proper control cancer

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Cellular Responses Cellular Responses to Environmental Stimulito Environmental Stimuli

Growing Cell

Apoptosis

Cancer

Growth Arrest

Differentiation

Continue growth

The Cell CycleThe Cell Cycle

M

G1

S

G2ApoptosisApoptosisDifferentiationDifferentiation CancerCancer

Tissue CulturesTissue Cultures• Initiated by placing a piece of tissue in a glass dish that contains serum• Cells migrates out of the tissue along the surface of the glass and proliferate.

They proliferate only if they are firmly attached to and spread out over an adhesive substrate (anchorage dependence)

• Proliferation ceases when the dish is covered with a single layer of cells. Once the cells form a continuous sheet they stop dividing (contact inhibition)

• Transferring the contact inhibited primary cells at lower densities to new dishes that contain fresh medium induces them to resume proliferation. After about 50 divisions in tissue culture proliferation slows and cells begin to die (senescence)

• Some of the cells in the culture accumulate genetic change that allow them to escape senescence. As long as they are transferred to new dishes periodically, these cells can divide indefinitely. These homogeneous populations are called tissue culture cell lines. They resemble primary cells in their growth control. (non-transformed)

Transformed Cell Lines

• Lost normal growth control• Can be selected when tissue culture cell lines are

allowed to grow repeatedly to high densities• Produced by allowing cells to grow out of tumors• Produced by treating primary cells or

nontransformed cell lines with chemical carcinogens or cancer-inducing viruses

• When injected into animals without functional immune system, transformed cell lines cause tumors.

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Commonly used cell linesCommonly used cell linesCell Line Cell Type Application Comment

BHK (baby hamster kidney) Fibroblast Vaccine production Anchorage dependent, can be induced to suspension

COS (African green monkey kidney) Fibroblast Transient expression of

recombinant genes

Contain a mutant of SV40 virus

L (Mouse connective tissue) Fibroblast Tumour cell line

3T3 (Mouse connective tissue) Fibroblast Develop culture technique Vigorous growth in suspension;

WI-38 (human embryonic lung) Fibroblast Human vaccine Finite life-span, “normal” cells

Vero Fibroblast Human vaccine Established cell line capable of continuous growth but

with normal diploid charact.

CHO (chinese hamster ovary) Epithelial Genetic engineering Attach to surface if available, will grow in suspension

HeLa (Human cervical carcinoma) Epithelial Fast growing human cancer cell isolated in the 1950's

MPC-11 (Mouse myeloma) Lymphoblast immunoglobulin Derived from mouse tumor

Namalwa (human lymphoma) Lymphoblast a-interferon Derived from burkitt's lymphoma patient

NB41A3 (Mouse Neuroblastoma) Neuronal Tumour cells have nerve cell characteristics including

response to nerve growth factor

BW5147 (Murine thymus)

Requirements for cells used in cell cultureRequirements for cells used in cell culture

Mammalian Cell Biotechnology in Protein Production, H. Hauser, 1996

Property Examples

Efficient expression of foreign genes Transcription and post -transcriptional process;

Protein synthesis; Secretion

Post-translational modifications e.g. protein folding; glycosylation, phosphorylation

Stability of transgene expression Genotypic (chromosomal stability)

Phenotypic (CpG methylation, chromosome structure alterations)

Absence of adventitious agents Viruses; Mycoplasms

Cultivation requirements Serum Growth factors, stabilizing proteins

Fermentation properties Growth to high cell densities

Resistance to shear forces

Aeration processes

Production of toxic compounds (e.g. lactic acid)

Production under fermentation

conditions

High production at high cell density

Reduced cell growth

Protein requirements in medium

Cell Growth Fast growth at low cell density

Reduced growth at high cell density

Cell MetabolismCell Metabolism Culture TechniquesCulture Techniques

• Culture containers - T-flask, multiwell, bioreactor• Culture media - BME, BMEM, DMEM, GMEM,

Han’s F-12, CHO• CO2 incubator - 5-10%, pH 6.9-7.4, 37oC

• Sterilization - Filtration

• Liquid N2 storage

−+ +↔↔+ 33222 HCOHCOHOHCObasic acidic

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MediaMedia

• CarbohydrateEnergy sourceglucose (4-5g/L), fructose

• Amino acid (0.1-0.2 mM)protein precursorsglutamine (2-4mM)

• Salts (Buffer): K, Mg, Caisotonic, osmolarity 300 mOsm/lPBS, HEPES

• Vitamins (μM) and hormonesmetabolic cofactors

• Phenol redindicator, pH: 7.4 (red), 7.0 (orange), 6.5 (yellow)

• Serum– proteins (immunoglobulins, albumin,

transferin, fetuin, fibronectin)– growth factors– Insulin (glucose uptake)– steroids– Trace minerals (Fe, Cu, Zn, Se)– Growth inhibitors

• Alternative to serum(serum free)– cell type specific e.g. insulin,

transferrin, ethanolamine, sodium selenite

• Antibiotics– Penicillin G (100 U/ml) inhibit G+

bacteria– streptomycin (50 mg/l) G+ & G-– amphotericin B (25mg/l) anti-fungi– culture are easy to overgrow by bacteria

because of the difference in growth rates (typical doubling time: animal cell: 24 h, bacteria: 30min)

Supplements Extracellular matrix (ECM) proteins

Bioreactor Systems Bioreactor Systems for Animal Cell Culturesfor Animal Cell Cultures

• Static flasks and roller bottles• Spinner flasks• Bioreactors (stirred, airlift, immobilized)

Bioreactors for Culture in Bioreactors for Culture in Suspension or on CarriersSuspension or on Carriers

Features for Wave Bioreactor: - Disposable Bioreactor Chamber. - Scalable to 500 liters. - Completely closed system. Operates without an incubator.

- Easy to operate.

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Porous microcarrier increases available surface areas for anchorage-dependent cell growth

Non-woven fibers with large surface areas for cell attachment and growth

MicrocarrierMicrocarrier and Fibrous Support Matrixand Fibrous Support Matrix

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• Media composition selection• DO (dissolved oxygen)• Accumulation of toxic metabolites• Shear stress to cell when oxygen or mixing

is needed• Other factors: Temp, pH, osmotic pressure,

etc.

Considerations in Bioprocess DesignConsiderations in Bioprocess Design

Minimizing Mechanical StressesMinimizing Mechanical Stresses

• Design agitation system • Thermal environment must be uniform• No disturbing the system during adding

nutrients and removing wastes • Adequate oxygen delivery without

excessive foaming or shear damage

Optimization and control Optimization and control of culturing conditionsof culturing conditions

• Precise pH control• Precise DO control• Accurate temperature control• Reliable monitoring of important cell culture

parameters (cell density, conc. of glucose, lactate, ammonia)

• Dependable nutrient feed and harvest rate controls

• Automatic impeller acceleration control for 20-225 rpm

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• serum free media (chemical defined, easy separation)

• up to 20,000L• oxygen

• bubble: direct sparging• bubble-free: surface aeration or flow through cage

• perfusion culture to remove toxic metabolites• reduce physical stress• pH, osmolality controlled by buffer, PBS,

HEPES (pH~7)• development of anchorage-independent cell line

Industrial Scale Cell CultureIndustrial Scale Cell CultureTypical Oxygen Transfer Coefficients Typical Oxygen Transfer Coefficients for Cell Growth in Various Systemsfor Cell Growth in Various Systems

System

Animal cells, 2 x 106 cells/ml (0.5 g/L)

Bacterial cells (10 - 20 g/L)

Yeast cells (10 - 30 g/L)

KLa (h-1)

1 -25

100 - 1000

100 - 1000

Culturing ModeCulturing Mode• Batch

– CSTR or PFR– maximum cell density 106 cell/ml

• depletion of an essential nutrient• accumulation of an inhibitor• complete cover of available growth surface (space)

• Fed-Batch• Continuous

– Chemostat vs. perfusion • Cell Immobilization

– surface attachment vs. entrapment

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Bioreactor as Cell FactoryBioreactor as Cell FactoryBioreactor as Cell Factory

Hole, Cells Tissues Organs 1999;165:181-189.Kaufman et al, Proc. Natl. Acad. Sci. 2001;98:10716-10721

HematopoiesisHematopoiesis

Embryonic Stem CellsEmbryonic Stem CellsEmbryonic Stem CellsEmbryonic Stem Cells (Inner Cell Mass)

Mesoderm

HeartMuscleKidney

Vascular systemMesenchymal

stem cell

Ectoderm

EpidermisNervous system

(Neural stem cell)

Endoderm

IntestinesLiver

PancreasLung

Hematopoietic stem cell (HSC)

Blood cells

Bone Cartilage Adipocyte Skeletal Muscle

Tissue EngineeringTissue EngineeringTissue Engineering

1.Muscle cells are seeded on a tube of biodegradable polymer matrix. 2.It is placed in a bioreactor. 3.Two month later, smooth muscle is generated. 4.Endothelial cells are added to line the tube. The blood vessel can be used for instance in heart surgery

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Artificial LiverArtificial LiverArtificial Liver

The liver-on-chip bioreactor from Hepatometrix.

CirculatingWater

CirculatingWater

Fibrous matrix

Media

Media

Media

Media

Bioreactor for Drug ScreeningBioreactor for Drug Screening

Capillary

Syncytiotrophoblast

Chorionic villousIntervillous space

• Human placenta trophoblast cells• Human colon cancer cells

Cell Number vs. GFP Fluorescence

GFP vs Cells

y = 0.657x + 22068

0.0E+00

1.0E+05

2.0E+05

3.0E+05

4.0E+05

5.0E+05

6.0E+05

7.0E+05

8.0E+05

0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05 1.0E+06

Cell Number

Fluo

resc

ence

(CPS

) CHO GFP

EGFP production under CMV promoter can be used as S-phase marker for drug screeningEGFP production under CMV promoter can be EGFP production under CMV promoter can be used as Sused as S--phase marker for phase marker for drug screeningdrug screening

A. Cells expressing GFPB. Cells stained with BrdUC. Superimposed image

A B C

Three critical issues in implant devices– Tissue– Immune rejection– Device design

Microbioreactor for Gene/Cell TherapyMicrobioreactor for Gene/Cell TherapyMicrobioreactor for Gene/Cell Therapy

GDNF: A novel treatment for ParkinsonGDNF: A novel treatment for Parkinson’’s Diseases DiseaseGlial cell line Derived Neurotrophic Factor

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Fermentation & Cell Culture GoHigh Throughput

Fermentation & Cell Culture GoFermentation & Cell Culture GoHigh ThroughputHigh Throughput

• Functional genomics call for high throughput in cell cultivation

• Reported working volumes: 250 μL - 2 mL

• Miniaturized and automated pH, temperature and dissolved oxygen measurements and/or reproducible gas delivery

• Combined with printed circuit board, integrated circuit sensors and electrochemical gas generation system

Michel et al (2004), Biotechnol Bioeng, 85,376-381

MicroMicro--bioreactorbioreactor

BioProcessors Corp.

Microfluidic Bioreactor ArrayMicrofluidic Bioreactor Array

Cell-based high throughput screening for drug discovery

Microscale cell culture analog Microscale cell culture analog --Animal on a chipAnimal on a chip

L2 cells in the lung chamber

HepG2/C3A in the liver chamber

3T3-L1 in the fat chamber