The role of biopreservation in cell and gene therapy bioprocessing

Cell and gene-based therapies represent a novel therapeutic modality that has the potential to provide a treatment option for a range of medical conditions. There are, however, numerous processing and manufacturing challenges that must be addressed before such therapies are considered commercially and clinically viable. A significant challenge associated with the manufacture of such therapies is ensuring cell quality and the product’s critical quality attributes are retained throughout the entire bioprocess. Biopreservation is an important aspect of cell and gene-based therapy bioprocessing, which enables the development of cell banks. It increases process flexibility by providing a shelf-life to the product, enables the storage of intermediates and provides breakpoints within the process. In this article, we summarize the advances and challenges associated with biopreservation of cell and gene therapies

Expansion of human mesenchymal stem/stromal cells (hMSCs) in bioreactors using microcarriers: lessons learnt and what the future holds

Human mesenchymal stem/stromal cells (hMSCs) present a key therapeutic cellular intervention for use in cell and gene therapy (CGT) applications due to their immunomodulatory properties and multi-differentiation capability. Some of the indications where hMSCs have demonstrated pre-clinical or clinical efficacy to improve outcomes are cartilage repair, acute myocardial infarction, graft versus host disease, Crohn’s disease and arthritis. The current engineering challenge is to produce hMSCs at an affordable price and at a commercially-relevant scale whilst minimising process variability and manual, human operations. By employing bioreactors and microcarriers (due to the adherent nature of hMSCs), it is expected that production costs would decrease due to improved process monitoring and control leading to better consistency and process efficiency, and enabling economies of scale. This approach will result in off the shelf (allogeneic) hMSC-based products becoming more accessible and affordable. Importantly, cell quality, including potency, must be maintained during the bioreactor manufacturing process. This review aims to examine the various factors to be considered when developing a hMSC manufacturing process using microcarriers and bioreactors and their potential impact on the final product. As concluding remarks, gaps in the current literature and potential future areas of research are also discussed

Culture of human mesenchymal stem cells on microcarriers in a 5 l stirred-tank bioreactor

This article was published in the journal, Biotechnology Letters [© Springer Science+Business Media] and the definitive version is available at: http://dx.doi.org/10.1007/s10529-013-1211-9For the first time, fully functional human mesenchymal stem cells (hMSCs) have been cultured at the litre-scale on microcarriers in a stirred-tank 5 l bioreactor, (2.5 l working volume) and were harvested via a potentially scalable detachment protocol that allowed for the successful detachment of hMSCs from the cell-microcarrier suspension. Over 12 days, the dissolved O2 concentration was >45 % of saturation and the pH between 7.2 and 6.7 giving a maximum cell density in the 5 l bioreactor of 1.7 × 105 cells/ml; this represents >sixfold expansion of the hMSCs, equivalent to that achievable from 65 fully-confluent T-175 flasks. During this time, the average specific O2 uptake of the cells in the 5 l bioreactor was 8.1 fmol/cell h and, in all cases, the 5 l bioreactors outperformed the equivalent 100 ml spinner-flasks run in parallel with respect to cell yields and growth rates. In addition, yield coefficients, specific growth rates and doubling times were calculated for all systems. Neither the upstream nor downstream bioprocessing unit operations had a discernible effect on cell quality with the harvested cells retaining their immunophenotypic markers, key morphological features and differentiation capacity

Design and development of a new ambr250® bioreactor vessel for improved cell and gene therapy applications

The emergence of cell and gene therapies has generated significant interest in their clinical and commercial potential. However, these therapies are prohibitively expensive to manufacture and can require extensive time for development due to our limited process knowledge and understanding. The automated ambr250® stirred-tank bioreactor platform provides an effective platform for high-throughput process development. However, the original dual pitched-blade 20 mm impeller and baffles proved sub-optimal for cell therapy candidates that require suspension of microcarriers (e.g. for the culture of adherent human mesenchymal stem cells) or other particles such as activating Dynabeads® (e.g. for the culture of human T-cells). We demonstrate the development of a new ambr250® stirred-tank bioreactor vessel which has been designed specifically to improve the suspension of microcarriers/beads and thereby improve the culture of such cellular systems. The new design is unbaffled and has a single, larger elephant ear impeller. We undertook a range of engineering and physical characterizations to determine which vessel and impeller configuration would be most suitable for suspension based on the minimum agitation speed (NJS) and associated specific power input (P/V)JS. A vessel (diameter, T, = 60 mm) without baffles and incorporating a single elephant ear impeller (diameter 30 mm and 45° pitch-blade angle) was selected as it had the lowest (P/V)JS and therefore potentially, based on Kolmogorov concepts, was the most flexible system. These experimentally-based conclusions were further validated firstly with computational fluid dynamic (CFD) simulations and secondly experimental studies involving the culture of both T-cells with Dynabeads® and hMSCs on microcarriers. The new ambr250® stirred-tank bioreactor successfully supported the culture of both cell types, with the T-cell culture demonstrating significant improvements compared to the original ambr250® and the hMSC-microcarrier culture gave significantly higher yields compared with spinner flask cultures. The new ambr250® bioreactor vessel design is an effective process development tool for cell and gene therapy candidates and potentially for autologous manufacture too

Study of gas-liquid mixing in stirred vessel using electrical resistance tomography

This study presents a full operation and optimisation of a mixing unit; an innovative approach is developed to address the behaviour of gas-liquid mixing by using Electrical Resistance Tomography (ERT). The validity of the method is investigated by developing the tomographic images using different numbers of baffles in a mixing unit. This technique provided clear visual evidence of better mixing that took place inside the gasliquid system and the effect of a different number of baffles on mixing characteristics. For optimum gas flow rate (m3/s) and power input (kW), the oxygen absorption rate in water was measured. Dynamic gassingout method was applied for five different gas flow rates and four different power inputs to find out mass transfer coefficient (KLa). The rest of the experiments with one up to four baffles were carried out at these optimum values of power input (2.0 kW) and gas flow rate (8.5×10-4 m3/s). The experimental results and tomography visualisations showed that the gasliquid mixing with standard baffling provided near the optimal process performance and good mechanical stability, as higher mass transfer rates were obtained using a greater number of baffles. The addition of single baffle had a striking effect on mixing efficiency and additions of further baffles significantly decrease mixing time. The energy required for complete mixing was remarkably reduced in the case of four baffles as compared to without any baffle. The process economics study showed that the increased cost of baffles installation accounts for less cost of energy input for agitation. The process economics have also revealed that the optimum numbers of baffles are four in the present mixing unit and the use of an optimum number of baffles reduced the energy input cost by 54%

Optimization of insect cell based protein production processes - online monitoring, expression systems, scale-up

Due to the increasing use of insect cell based expression systems in research and industrial recombinant protein production, the development of efficient and reproducible production processes remains a challenging task. In this context, the application of online monitoring techniques is intended to ensure high and reproducible product qualities already during the early phases of process development. In the following chapter, the most common transient and stable insect cell based expression systems are briefly introduced. Novel applications of insect cell based expression systems for the production of insect derived antimicrobial peptides/proteins (AMPs) are discussed using the example of G. mellonella derived gloverin. Suitable in situ sensor techniques for insect cell culture monitoring in disposable and common bioreactor systems are outlined with respect to optical and capacitive sensor concepts. Since scale-up of production processes is one of the most critical steps in process development, a conclusive overview is given about scale up aspects for industrial insect cell culture processes

Numerical methods for the design and description of in vitro expansion processes of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are a valuable source of cells for clinical applications (e.g., treatment of acute myocardial infarction or inflammatory diseases), especially in the field of regenerative medicine. However, for autologous (patient-specific) and allogeneic (off-the-shelf) hMSC-based therapies, in vitro expansion is necessary prior to the clinical application in order to achieve the required cell numbers. Safe, reproducible, and economic in vitro expansion of hMSCs for autologous and allogeneic therapies can be problematic because the cell material is restricted and the cells are sensitive to environmental changes. It is beneficial to collect detailed information on the hydrodynamic conditions and cell growth behavior in a bioreactor system, in order to develop a so called “Digital Twin” of the cultivation system and expansion process. Numerical methods, such as Computational Fluid Dynamics (CFD) which has become widely used in the biotech industry for studying local characteristics within bioreactors or kinetic growth modelling, provide possible solutions for such tasks. In this review, we will present the current state-of-the-art for the in vitro expansion of hMSCs. Different numerical tools, including numerical fluid flow simulations and cell growth modelling approaches for hMSCs, will be presented. In addition, a case study demonstrating the applicability of CFD and kinetic growth modelling for the development of an microcarrier-based hMSC process will be shown