Long term and large-scale cultivation of human hepatoma Hep G2 cells in hollow fiber bioreactor

Three Dimensional Culture Upregulates Extracellular Matrix Protein Expression in Human Liver Cell Lines - a Step towards Mimicking the Liver in Vivo?

Extracellular matrix (ECM) in the liver affects the phenotype of both hepatocytes and non-parenchymal cells. To be able to mimic in vivo liver function for extracorporeal hepatic support using human cell lines, a necessary step is to upregulate the function normally seen in monolayer culture. 3-D spheroid colonies were formed by culturing single HepG2 cells encapsulated in alginate beads. ECM expression in these cultures was compared to monolayer Hep G2 cultures. The following ECM proteins were detected immunohistochemically:- collagens I, III, V and VI, the glycoproteins fibronectin, tenascin and vitronectin, and the basement membrane protein laminin. In 3-D cultures, all proteins except tenascin were strongly expressed, as compared with weak or undetectable expression in monolayer cultures, even with 10-fold increases in the antibody concentration used. In conclusion, we have demonstrated that the 3-D environment created by alginate encapsulation of cell lines leads to cell behaviour mimicking that in vivo.

Bioengineering the liver: scale-up and cool chain delivery of the liver cell biomass for clinical targeting in a bioartificial liver support system

Acute liver failure has a high mortality unless patients receive a liver transplant; however, there are insufficient donor organs to meet the clinical need. The liver may rapidly recover from acute injury by hepatic cell regeneration given time. A bioartificial liver machine can provide temporary liver support to enable such regeneration to occur. We developed a bioartificial liver machine using human-derived liver cells encapsulated in alginate, cultured in a fluidized bed bioreactor to a level of function suitable for clinical use (performance competence). HepG2 cells were encapsulated in alginate using a JetCutter to produce ∼500 μm spherical beads containing cells at ∼1.75 million cells/mL beads. Within the beads, encapsulated cells proliferated to form compact cell spheroids (AELS) with good cell-to-cell contact and cell function, that were analyzed functionally and by gene expression at mRNA and protein levels. We established a methodology to enable a ∼34-fold increase in cell density within the AELS over 11-13 days, maintaining cell viability. Optimized nutrient and oxygen provision were numerically modeled and tested experimentally, achieving a cell density at harvest of >45 million cells/mL beads; >5×10(10) cells were produced in 1100 mL of beads. This process is scalable to human size ([0.7-1]×10(11)). A short-term storage protocol at ambient temperature was established, enabling transport from laboratory to bedside over 48 h, appropriate for clinical translation of a manufactured bioartificial liver machine.

Comparison of cell growth in T-flasks, in micro hollow fiber bioreactors, and in an industrial scale hollow fiber bioreactor system

In this article, cell growth in a novel micro hollow fiberbioreactor was compared to that in a T-flask and theAcuSyst-Maximizer(R), a large scale industrial hollowfiber bioreactor system. In T-flasks, there was relativelylittle difference in the growth rates of one murine hybridomacultured in three different media and for three other murinehybridomas cultured in one medium. However, substantialdifferences were seen in the growth rates of cells in themicro bioreactor under these same conditions. These differencecorrelated well with the corresponding rates of initial cellexpansion in the Maximizer. Quantitative prediction of thesteady-state antibody production rate in the Maximizer was moreproblematic. However, conditions which lead to faster initialcell growth and higher viable cell densities in the microbioreactor correlated with better performance of a cell line inthe Maximizer. These results demonstrate that the microbioreactor is more useful than a T-flask for determining optimalconditions for cell growth in a large scale hollow fiberbioreactor system.

Bioartificial liver support systems

A variety of bioartificial liver support systems were developed to replace some of the liver's function in case of liver failure. Those systems, in contrast to purely artificial systems, incorporate metabolically active cells to contribute synthetic and regulatory functions as well as detoxification. The selection of the ideal cell source and the design of more sophisticated bioreactors are the main issues in this field of research. Several systems were already introduced into clinical studies to prove their safety. This review briefly introduces a cross-section of experimental and clinically applied systems and tries to give an overview on the problems and limitations of bioartificial liver support.

Quantitative inference of cellular parameters from microfluidic cell culture systems

Microfluidic cell culture systems offer a convenient way to measure cell biophysical parameters in conditions close to the physiological environment. We demonstrate the application of a mathematical model describing the spatial distribution of nutrient and growth factor concentrations in inferring cellular oxygen uptake rates from experimental measurements. We use experimental measurements of oxygen concentrations in a poly(dimethylsiloxane) (PDMS) microreactor culturing human hepatocellular liver carcinoma cells (HepG2) to infer quantitative information on cellular oxygen uptake rates. We use a novel microchannel design to avoid the parameter correlation problem associated with simultaneous cellular uptake and diffusion of oxygen through the PDMS surface. We find that the cellular uptake of oxygen is dependent on the cell density and can be modeled using a logistic term in the Michaelis-Menten equation. Our results are significant not only for the development of novel assays to quantitatively infer cell response to stimuli, but also for the development, design, and optimization of novel in vitro systems for drug discovery and tissue engineering.

Evaluation of a new immortalized human fetal liver cell line (cBAL111) for application in bioartificial liver

BACKGROUND/AIMS

Clinical use of bioartificial livers (BAL) relies heavily on the development of human liver cell lines. The aim of this study was to assess the potential of the recently developed human fetal liver cell line cBAL111 for application in the AMC-BAL.

METHODS

Laboratory-scale AMC-BAL bioreactors were loaded with 20 or 200 million cBAL111 cells and were cultured for 3 days. Parameters for hepatocyte-specific function and general metabolism were determined daily using tests with culture medium or 100% human serum. The bioreactors were also analyzed for mRNA levels of liver-specific genes and histology.

RESULTS

cBAL111 eliminated ammonia at a rate up to 49% of that in primary porcine hepatocytes (PPH), despite a low (1.1%) urea production. Transcript levels of glutamine synthetase (GS) were 570% of that in human liver, whereas genes of the urea cycle showed low expression. GS expression was confirmed immunohistochemically, and glutamine was produced by the cells. cBAL111 eliminated galactose (90.1% of PPH) and lidocaine (0.1% of PPH) and produced albumin (6% of PPH). Human serum did not increase function of cBAL111.

CONCLUSIONS

cBAL111 showed liver-specific functionality when cultured inside the AMC-BAL and eliminated ammonia mainly by the activity of GS, and not through the urea cycle.

Studies on the use of hollow fibre membrane bioreactors for tissue generation by using rat bone marrow fibroblastic cells and a composite scaffold

Production of sufficient tissue in vitro for use in tissue engineering is limited mainly by the absence of adequate oxygenation and appropriate transport of nutrients to, and waste product from, the tissue. To overcome the limitations of diffusive transport, the possibility of growing three dimensional (3D) tissue structures by using hollow fibre membrane bioreactors (HFMB) has been considered in this study. The hollow fibre membranes, embedded in the 3D scaffold, are porous and semi-permeable and can thus serve similar functions to arteries and veins in vivo. Collagen gel and Cytodex 1 microcarriers were used as a composite 3D scaffold and permeating cellulose acetate hollow fibre membranes were attached to both ends of a polycarbonate cylindrical shell to form a bioreactor. Rat bone marrow fibroblastic (RBMF) cells were seeded initially onto Cytodex 1 microcarriers and these were subsequently mixed with collagen gel before inoculation into the bioreactor. Bioreactors were perfused by culture medium through the hollow fibre membranes for a one week period. Bioreactors containing cells cultured under similar conditions except for the lack of perfusion of medium served as controls. The proliferation, viability, metabolism and morphological appearances of the cells in the perfused and non-perfused constructs were compared. The results indicated that there was significantly greater maintenance of functional activity and normal cellular morphology in the perfused group than in the non-perfused group. Further studies are required to evaluate the additional advantages of using this novel HFMB for growing 3D dense tissues.

Hepatocyte hollow-fibre bioreactors: design, set-up, validation and applications

Hepatocytes carry out many vital biological functions, such as synthetic and catabolic reactions, detoxification and excretion. Due to their ability to restore a tissue-like environment, hollow-fibre bioreactors (HFBs) show great potential among the different systems used to culture hepatocytes. Several designs of HFBs have been proposed in which hepatocytes or hepatocyte-derived cell lines can be cultured in suspensions or on a solid support. Currently the major use of hepatocyte HFBs is as bioartificial livers to sustain patients suffering from acute liver failure, but they can also be used to synthesize cell products and as cellular models for drug metabolism and transport studies. Here, we present an overview of the set-up of hepatocyte HFBs and aim to provide potential users with the basic knowledge necessary to develop their own system. First, general information on HFBs is given, including basic principles, transport phenomena, designs and cell culture conditions. The importance of the tests necessary to assess the performance of the HFBs, i.e. the viability and functionality of hepatocytes, is underlined. Special attention is paid to drug metabolism studies and to adequate analytical methods. Finally, the potential uses of hepatocyte HFBs are described.

Improved gene transfer and normalized enzyme levels in primitive hematopoietic progenitors from patients with mucopolysaccharidosis type I using a bioreactor

BACKGROUND

One of the major barriers to the clinical application of hematopoietic stem cell (HSC) gene therapy has been relatively low gene transfer efficiency. Other inadequacies of current transduction protocols are related to their multi-step procedures, e.g., using tissue-culture flasks, roller bottles or gas-permeable bags for clinical application.

METHODS

In comparison with a conventional bag transduction protocol, a 'closed' hollow-fiber bioreactor system (HBS) was exploited to culture and transduce human peripheral blood CD34(+) progenitor cells (PBPC(MPS)) from patients with mucopolysaccharidosis type I (MPS I) using an amphotropic retroviral vector based on a murine Moloney leukemia virus LN prototype. Both short-term colony-forming cell (CFC) and long-term culture initiating cell (LTCIC) assays were employed to determine transduction frequency and transgene expression in committed progenitor cells and primitive progenitors with multi-lineage potentials.

RESULTS

A novel ultrafiltration-transduction method was established to culture and transduce enzyme-deficient PBPC(MPS) over a 5-day period without loss in viability and CD34 identity (n = 5). Significantly higher transduction efficiencies were achieved in primary CFC that derived from the HBS (5.8-14.2%) in comparison with those from gas-permeable bags (undetectable to 1.7%; p < 0.01). Up to 15-fold higher-than-normal enzyme activity was found in selected PBPC(MPS)-LP1CD transductants. Moreover, higher gene transfer (4.4-fold) and expression in very primitive progenitors were observed in products from the HBS compared with bag experiments as indicated by CFC derived from primitive LTCIC. Remarkably, with relatively modest gene transfer levels in LTCIC from HBS experiments, the expression of the IDUA transgene corrected the enzyme-deficiency in 5-week long-term cultures (LTC).

CONCLUSIONS

MPS I progenitor cells achieved normalized enzyme levels in LTC after transduction in a HBS system. These studies demonstrate the advantages of a bioreactor-transduction system for viral-mediated stem cell gene transfer.

Hollow fiber bioreactor: New development for the study of contrast agent transport into hepatocytes by magnetic resonance imaging

The aim of our study was to develop a magnetic resonance (MR)-compatible in vitro model containing freshly isolated rat hepatocytes to study the transport of hepatobiliary contrast agents (CA) by MR imaging (MRI). We set up a perfusion system including a perfusion circuit, a heating device, an oxygenator, and a hollow fiber bioreactor (HFB). The role of the porosity and surface of the hollow fiber (HF) as well as the perfusate flow rate applied on the diffusion of CAs and O2 was determined. Hepatocytes were isolated and injected in the extracapillary space of the HFB (4 x 10(7) cells/mL). The hepatocyte HFB was perfused with an extracellular CA, gadopentetate dimeglumine (Gd-DTPA), and gadobenate dimeglumine (Gd-BOPTA), which also enters into hepatocytes. The HFB was imaged in the MR room using a dynamic T1-weighed sequence. No adsorption of CAs was detected in the perfusion system without hepatocytes. The use of a membrane with a high porosity (0.5 microm) and surface (420 cm2), and a high flow rate perfusion (100 mL/min) resulted in a rapid filling of the HFB with CAs. The cellular viability of hepatocytes in the HFB was greater than 85% and the O2 consumption was maintained over the experimental period. The kinetics of MR signal intensity (SI) clearly showed the different behavior of Gd-BOPTA that enters into hepatocytes and Gd-DTPA that remains extracellular. Thus, these results show that our newly developed in vitro model is an interesting tool to investigate the transport kinetics of hepatobiliary CAs by measuring the MR SI over time.

Combined ultrafiltration-transduction in a hollow-fiber bioreactor facilitates retrovirus-mediated gene transfer into peripheral blood lymphocytes from patients with mucopolysaccharidosis type II

The process of growing and transducing large quantities of human primary peripheral blood lymphocytes (PBLs) with high gene transfer efficiency continues to be one of the major challenges for clinical and experimental gene therapy. Toward developing a clinical trial of lymphocyte gene therapy for mucopolysaccharidosis type II (i.e., Hunter syndrome), we investigated a novel method that exploited the innate capability of a hollow-fiber bioreactor system to filter large quantities of vector supernatant and facilitate transduction. An aliquot (5 x 10(7)) of PBL apheresis product was precultured in a gas-permeable culture bag or a bioreactor, and then transduced with a retroviral vector L2SN containing the iduronate-2-sulfatase (IDS) and neomycin resistance genes. We observed that the total number of PBLs could be expanded up to 187-fold, yielding up to 10(10) cells at the end of a 7-day culture period. The multiplicity of infection could be increased (up to 20-fold) by ultrafiltrating a large volume of vector supernatant through the semipermeable membrane of this system. A high level of transduction efficiency (up to 57%) was achieved, resulting in IDS enzyme activity as high as 1250 U/mg/hr in transduced PBL(MPS) 15 days after transduction. This level was markedly increased from that of nontransduced cells (<3 U/mg/hr) and was even greater than that of normal PBLs (mean, 809; n = 10). After 12 days of G418 selection, PBL(MPS) transductants exhibited a proviral IDS enzyme level approximately threefold higher than that in normal PBLs. These results indicated that the hollow-fiber bioreactor could be used to culture and transduce human primary PBLs in clinically useful quantities with relatively high gene transfer efficiency and transgene expression.

Closed hollow-fiber bioreactor: a new approach to retroviral vector production

BACKGROUND

The ability to obtain high-titer and large quantities of retroviral vector production in a 'closed' system would have profound implications in clinical and experimental gene therapy.

METHODS

We studied the cell growth and vector production of three retroviral packaging cell lines in a variety of conditions using hollow-fiber bioreactors designed as an 'artificial capillary system' (ACS) and enhanced with the application of a hermetically sealing device for sterile welding of connecting plastic tubings. Vector titer, fetal bovine serum (FBS) concentration, volume and the duration of productivity were assessed to optimize vector production.

RESULTS

In this pilot study, we observed that retroviral vector production (frozen-and-thawed) from cultures containing as low as 2.5% FBS yielded titers up to 2.2 x 10(7) cfu/ml, 14.4-fold higher than titers obtained from control dish cultures. Up to 3 liters of vector supernatant were generated during a 2-month large-scale production run. There was a potential to double this volume of higher-titer supernatant by increasing the frequency of harvest. It seemed that a lower metabolic rate (i.e. lactate production) in the packaging cell culture was associated with higher vector producing ability.

CONCLUSIONS

These data demonstrated the feasibility of producing retroviral vector with enhanced titers and clinically useful quantities in a 'closed' ACS. Thus a new approach for large-scale retroviral vector production is developed.