Application of process quality engineering techniques to improve the understanding of the in vitro processing of stem cells for therapeutic use

Mannose-Decorated Co-Polymer Facilitates Controlled Release of Butyrate to Accelerate Chronic Wound Healing

Butyrate is a key bacterial metabolite that plays an important and complex role in modulation of immunity and maintenance of epithelial barriers. Its translation to clinic is limited by poor bioavailability, pungent smell, and the need for high doses, and effective delivery strategies have yet to realize clinical potential. Here, a novel polymeric delivery platform for tunable and sustainable release of butyrate consisting of a methacrylamide backbone with butyryl ester or phenyl ester side chains as well as mannosyl side chains, which is also applicable to other therapeutically relevant metabolites is reported. This platform's utility in the treatment of non-healing diabetic wounds is explored. This butyrate-containing material modulated immune cell activation in vitro and induced striking changes in the milieu of soluble cytokine and chemokine signals present within the diabetic wound microenvironment in vivo. This novel therapy shows efficacy in the treatment of non-healing wounds through the modulation of the soluble signals present within the wound, and importantly accommodates the critical temporal regulation associated with the wound healing process. Currently, the few therapies to address non-healing wounds demonstrate limited efficacy. This novel platform is positioned to address this large unmet clinical need and improve the closure of otherwise non-healing wounds.

Reduced inflammation following human endometrial stromal/stem cell injection into male Wistar rats with cisplatin-induced acute kidney injury

Introduction: Inflammation is one of the most important mechanisms involved in cisplatin-induced acute kidney injury (AKI). Mesenchymal stromal/stem cells (MSCs) exhibit anti-inflammatory and immunomodulatory abilities. Human endometrial stromal/stem cells (hEnSCs) exhibit similar properties to MSCs. These cells secrete immunoregulators, so we investigated the inflammatory aspect of hEnSCs in the treatment of cisplatin-induced AKI in Wistar rats.

Methods: Each group consisted of 6 male Wistar rats. Groups were as follows: sham, model (5 mg/kg cisplatin, IP), and treatment (1 million hEnSCs, IV, 3 hours after cisplatin). Renal function, histopathology, proliferation rate, infiltration of CD3⁺ T cell, and expression of Il-10 and cystatin c (Cst3) were assessed on day 5. DiI-labeled cells were tracked in kidney and liver on days 4 and 14.

Results: HEnSC transplantation improved cisplatin-induced injuries such as renal dysfunction and tissue damage. The highest levels of pathologic scores and hyaline cast formation were observed in the model group while hEnSCs transplantation resulted in their reduction (154.00 ± 14.95, 8.00 ± 1.41 vs. 119.40 ± 5.43, 2.50 ± 1.05). The percentage of Ki-67 positive cells in the treatment group increased while cisplatin decreased proliferation (39.91 ± 5.33 vs. 23.91 ± 3.57 in glomeruli and 39.07 ± 2.95 vs. 16.61 ± 3.25 in tubules). The expression of Cst3 and Il-10 was higher in the model and treatment groups, respectively. DiI-labeled cells were observed in the renal tubules and liver lobes on days 4 and 14.

Conclusion: HEnSCs may ameliorate cisplatin-induced AKI through anti-inflammatory and immunomodulatory effects and/or through paracrine effects.

Clever Experimental Designs: Shortcuts for Better iPSC Differentiation

For practical use of pluripotent stem cells (PSCs) for disease modelling, drug screening, and regenerative medicine, the cell differentiation process needs to be properly refined to generate end products with consistent and high quality. To construct and optimize a robust cell-induction process, a myriad of cell culture conditions should be considered. In contrast to inefficient brute-force screening, statistical design of experiments (DOE) approaches, such as factorial design, orthogonal array design, response surface methodology (RSM), definitive screening design (DSD), and mixture design, enable efficient and strategic screening of conditions in smaller experimental runs through multifactorial screening and/or quantitative modeling. Although DOE has become routinely utilized in the bioengineering and pharmaceutical fields, the imminent need of more detailed cell-lineage specification, complex organoid construction, and a stable supply of qualified cell-derived material requires expedition of DOE utilization in stem cell bioprocessing. This review summarizes DOE-based cell culture optimizations of PSCs, mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and Chinese hamster ovary (CHO) cells, which guide effective research and development of PSC-derived materials for academic and industrial applications.

Understanding cell culture dynamics: a tool for defining protocol parameters for improved processes and efficient manufacturing using human embryonic stem cells

Standardization is crucial when culturing cells including human embryonic stem cells (hESCs) which are valuable for therapy development and disease modeling. Inherent issues regarding reproducibility of protocols are problematic as they hinder translation to good manufacturing practice (GMP), thus reducing clinical efficacy and uptake. Pluripotent cultures require standardization to ensure that input material is consistent prior to differentiation, as inconsistency of input cells creates end-product variation. To improve protocols, developers first must understand the cells they are working with and their related culture dynamics. This innovative work highlights key conditions required for optimized and cost-effective bioprocesses compared to generic protocols typically implemented. This entailed investigating conditions affecting growth, metabolism, and phenotype dynamics to ensure cell quality is appropriate for use. Results revealed critical process parameters (CPPs) including feeding regime and seeding density impact critical quality attributes (CQAs) including specific metabolic rate (SMR) and specific growth rate (SGR). This implied that process understanding, and control is essential to maintain key cell characteristics, reduce process variation and retain CQAs. Examination of cell dynamics and CPPs permitted the formation of a defined protocol for culturing H9 hESCs. The authors recommend that H9 seeding densities of 20,000 cells/cm2, four-day cultures or three-day cultures following a recovery passage from cryopreservation and 100% medium exchange after 48 hours are optimal. These parameters gave ~SGR of 0.018 hour-1 ± 1.5x10-3 over three days and cell viabilities ≥95%±0.4, while producing cells which highly expressed pluripotent and proliferation markers, Oct3/4 (>99% positive) and Ki-67 (>99% positive).

Mechanobiological conceptual framework for assessing stem cell bioprocess effectiveness

Fully realizing the enormous potential of stem cells requires developing efficient bioprocesses and optimizations founded in mechanobiological considerations. Here, we emphasize the importance of mechanotransduction as one of the governing principles of stem cell bioprocesses, underscoring the need to further explore the behavioral mechanisms involved in sensing mechanical cues and coordinating transcriptional responses. We identify the sources of intrinsic, extrinsic, and external noise in bioprocesses requiring further study, and discuss the criteria and indicators that may be used to assess and predict cell-to-cell variability resulting from environmental fluctuations. Specifically, we propose a conceptual framework to explain the impact of mechanical forces within the cellular environment, identify key cell state determinants in bioprocesses, and discuss downstream implementation challenges.

Evaluation of Knee Cartilage Diurnal, Activity, and BMI-Related Variations Using Quantitative T2 Mapping MRI and Fitbit Activity Tracking

The aim of this study is to evaluate diurnal variation in knee cartilage 3 Tesla magnetic resonance imaging (MRI) T2 mapping relaxation times, as well as activity- and body mass index (BMI)-dependent variability, using quantitative analysis of T2 values from segmented regions of the weight-bearing articular surfaces of the medial and lateral femoral condyles and tibial plateaus. Ten healthy volunteers' daily activity (steps) were tracked with Fitbit pedometers. Sagittal MRI T2 maps were obtained in the morning and afternoon on days 2 and 3. Mean T2 values were analyzed for variation related to the number of steps taken (activity), time of day (diurnal variation), and BMI using mixed effect model. Significant (albeit small) differences in the medial femoral and medial tibial cartilage regions were identified between morning and afternoon scans (diurnal variation). Daily activity did not result in significant changes and increasing BMI only demonstrated a slight increase in T2 values for the lateral tibial plateau. These findings suggest that it may be necessary to control diurnal variation when using quantitative MRI T2 mapping to assess articular cartilage longitudinally in healthy participants. Further investigation is needed to confirm these findings and determine if they also apply to symptomatic patients.

From protocol to product: ventral midbrain dopaminergic neuron differentiation for the treatment of Parkinson's disease

Current cell therapy product limitations include the need for in-depth product understanding to ensure product potency, safety and purity. New technologies require development and validation to address issues of production scale-up to meet clinical need; assays are required for process control, validation and release. Prior to clinical realization, an understanding of production processes is required to implement process changes that are essential for process control. Identification of key parameters forms the basis of process tolerances, allowing for validated, adaptive manufacturing processes. This enables greater process control and yield while withstanding regulatory scrutiny. This report summaries key milestones in specifically for ventral midbrain dopaminergic neuroprogenitor differentiation and key translational considerations and recommendations to enable successful, robust and reproducible current cell therapy product-manufacturing.

Fresh osteochondral grafting in the United States: the current status of tissue banking processing

The use of musculoskeletal allografts has become increasingly popular among surgeons. The purpose of this review is to highlight the procurment and delievery process of fresh osteochondral allografts in the United States. The four distributors of fresh osteochondral allografts in the United States were contacted. Surveys containing quantitative and qualitative sections concerning the procurement and processing of osteochondral allograft tissue were obtained. Our results showed an average of 13 ± 4.24 years of experience with osteochondral allografts. The average donor age ranged from 13.5 ± 3 to 37.5 ± 5 years, with an average age of 27 ± 2.83 years. All donors were between ages 12 and 45 years old. The percentage of screened donors that were accepted for allograft transplant was consistent at 70-75% for 3 out of the 4 tissue banks. The percentage of grafts that expire without implantation ranged from 20% to 29%. Maximum shipping time varied between 24 and 96 hours. Each tissue bank used its own proprietary storage medium. The time from donor death to the harvest of allograft tissue was < 24 hours. The most commonly requested osteochondral allograft tissue for all banks was the medial femoral condyle. The market share of fresh allografts is as follows: Joint Restoration Foundation (JRF) 59.9%, Muskuloskeletal Transplant Foundation (MTF) 15.3%, LifeNet Health (LN) 14.5%, and Regeneration Technology Incorporated (RTI) 10.2%, with approximately 4700 fresh allografts distributed in 2018. This compiled data from the four tissue banks that supply fresh osteochondral allograft in the United States  provides important background information for patients and orthopaedic surgeons.

Nomenclature Inconsistency and Selective Outcome Reporting Hinder Understanding of Stem Cell Therapy for the Knee

BACKGROUND

The prospect of treating knee cartilage injury/pathology with mesenchymal stem cells (MSCs) has garnered considerable attention in recent years, but study heterogeneity and a lack of randomized controlled trials (RCTs) preclude quantitative analysis. The purpose of this review was to provide clinicians with an overview of RCTs that addresses 2 key areas that have been largely overlooked: nomenclature inconsistency and selective outcome reporting.

METHODS

RCTs that purported to use stem cells or MSCs to treat knee cartilage were identified with use of PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses). Study variables were compiled, and methodological quality was assessed. The cell treatments and the methods used to characterize them were recorded and compared. Clinical, radiographic, and arthroscopic outcomes were extracted and evaluated qualitatively.

RESULTS

There was extensive variation among the treatments, adjuvant therapies, and outcome measures. Treatments did not coincide with terminology. Significant differences in clinical outcomes were reported infrequently, and intra-group improvements or inter-group subscore differences were consistently highlighted, particularly when inter-group comparisons were left unreported.

CONCLUSIONS

Overall, there are isolated cases in which positive efficacy results have been published, but our results suggest that the generally positive efficacy conclusions concerning stem cell therapy for knee cartilage pathology may be overstated. Nevertheless, it is important to understand that the efficacy of stem cell therapies should not be considered in aggregate. Cells that are procured or processed differently produce entirely different drugs. When evaluating the efficacy of "stem cell" therapies, clinicians must consider the methodological quality, nomenclature, and inherent distinctness of each treatment.

The Economics and Regulation of PRP in the Evolving Field of Orthopedic Biologics

PURPOSE OF REVIEW

This review provides an update on the current status of platelet-rich plasma (PRP). Topics covered include the current regulatory environment, economic outlook, and current clinical evidence.

RECENT FINDINGS

The global PRP market is expected to grow to between 380 million and 4.5 billion (USD) over the next 5-10 years. The cost of a single treatment, which is not covered by most insurance, is roughly $500-$2500, with patients often returning for additional treatments. While PRP is not 'FDA-approved', it can be legally offered in the clinic 'off-label' in the USA for a myriad of musculoskeletal indications. Recently published meta-analyses have demonstrated statistically significant improvements that, in some cases, suggest that PRP may have clinically meaningful effects. However, given the fact that clearance is not synonymous with approval, PRP is a costly treatment not covered by insurance, and clinical trials have not demonstrated definitive efficacy, we recommend informing patients when providing PRP 'off-label'.

Intra-articular Mesenchymal Stem Cell Therapy for the Human Joint: A Systematic Review

BACKGROUND

Stem cell therapy is emerging as a potential treatment of osteoarthritis (OA) and chondral defects (CDs). However, there is a great deal of heterogeneity in the literature. The indications for stem cell use, the ideal tissue source, and the preferred outcome measures for stem cell-based treatments have yet to be determined.

PURPOSE

To provide clinicians with a comprehensive overview of the entire body of the current human literature investigating the safety and efficacy of intra-articular mesenchymal stem cell (MSC) therapy in all joints.

METHODS

To provide a comprehensive overview of the current literature, all clinical studies investigating the safety and efficacy of intra-articular MSC therapy were included. PubMed, MEDLINE, and Cochrane Library databases were searched for published human clinical trials involving the use of MSCs for the treatment of OA and CDs in all joints. A total of 3867 publications were screened.

RESULTS

Twenty-eight studies met the criteria to be included in this review. Fourteen studies treating osteoarthritis and 14 studies treating focal chondral defects were included. MSCs originating from bone marrow (13), adipose tissue (12), synovial tissue (2), or peripheral blood (2) were administered to 584 distinct individuals. MSCs were administered into the knee (523 knees), foot/ankle (61), and hip (5). The mean follow-up time was 24.4 months after MSC therapy. All studies reported improvement from baseline in at least 1 clinical outcome measure, and no study reported major adverse events attributable to MSC therapy.

DISCUSSION

The studies included in this review suggest that intra-articular MSC therapy is safe. While clinical and, in some cases, radiological improvements were reported for both OA and CD trials, the overall quality of the literature was poor, and heterogeneity and lack of reproducibility limit firm conclusions regarding the efficacy of these treatments.

CONCLUSION

This review provides strong evidence that autologous intra-articular MSC therapy is safe, with generally positive clinical outcomes.

The importance of factorial design in tissue engineering and biomaterials science: Optimisation of cell seeding efficiency on dermal scaffolds as a case study

This article presents a case study to show the usefulness and importance of using factorial design in tissue engineering and biomaterials science. We used a full factorial experimental design (2 × 2 × 2 × 3) to solve a routine query in every biomaterial research project: the optimisation of cell seeding efficiency for pre-clinical in vitro cell studies, the importance of which is often overlooked. In addition, tissue-engineered scaffolds can be cellularised with relevant cell type(s) to form implantable tissue constructs, where the cell seeding method must be reliable and robust. Our results show the complex relationship between cells and scaffolds and suggest that the optimum seeding conditions for each material may be different due to different material properties, and therefore, should be investigated for individual scaffolds. Our factorial experimental design can be easily translated to other cell types and three-dimensional biomaterials, where multiple interacting variables can be thoroughly investigated for better understanding of cell–biomaterial interactions.

Climbing the mountain: experimental design for the efficient optimization of stem cell bioprocessing

"To consult the statistician after an experiment is finished is often merely to ask him to conduct a post mortem examination. He can perhaps say what the experiment died of." - R.A. Fisher While this idea is relevant across research scales, its importance becomes critical when dealing with the inherently large, complex and expensive process of preparing material for cell-based therapies (CBTs). Effective and economically viable CBTs will depend on the establishment of optimized protocols for the production of the necessary cell types. Our ability to do this will depend in turn on the capacity to efficiently search through a multi-dimensional problem space of possible protocols in a timely and cost-effective manner. In this review we discuss approaches to, and illustrate examples of the application of statistical design of experiments to stem cell bioprocess optimization.

Development of a Modular Automated System for Maintenance and Differentiation of Adherent Human Pluripotent Stem Cells

Patient-specific induced pluripotent stem cells (iPSCs) have tremendous potential for development of regenerative medicine, disease modeling, and drug discovery. However, the processes of reprogramming, maintenance, and differentiation are labor intensive and subject to intertechnician variability. To address these issues, we established and optimized protocols to allow for the automated maintenance of reprogrammed somatic cells into iPSCs to enable the large-scale culture and passaging of human pluripotent stem cells (PSCs) using a customized TECAN Freedom EVO. Generation of iPSCs was performed offline by nucleofection followed by selection of TRA-1-60-positive cells using a Miltenyi MultiMACS24 Separator. Pluripotency markers were assessed to confirm pluripotency of the generated iPSCs. Passaging was performed using an enzyme-free dissociation method. Proof of concept of differentiation was obtained by differentiating human PSCs into cells of the retinal lineage. Key advantages of this automated approach are the ability to increase sample size, reduce variability during reprogramming or differentiation, and enable medium- to high-throughput analysis of human PSCs and derivatives. These techniques will become increasingly important with the emergence of clinical trials using stem cells.

The translation of cell-based therapies: clinical landscape and manufacturing challenges

Cell-based therapies have the potential to make a large contribution toward currently unmet patient need and thus effective manufacture of these products is essential. Many challenges must be overcome before this can become a reality and a better definition of the manufacturing requirements for cell-based products must be obtained. The aim of this study is to inform industry and academia of current cell-based therapy clinical development and to identify gaps in their manufacturing requirements. A total of 1342 active cell-based therapy clinical trials have been identified and characterized based on cell type, target indication and trial phase. Multiple technologies have been assessed for the manufacture of these cell types in order to facilitate product translation and future process development.

Large-scale cell production of stem cells for clinical application using the automated cell processing machine

BACKGROUND

Cell-based regeneration therapies have great potential for application in new areas in clinical medicine, although some obstacles still remain to be overcome for a wide range of clinical applications. One major impediment is the difficulty in large-scale production of cells of interest with reproducibility. Current protocols of cell therapy require a time-consuming and laborious manual process. To solve this problem, we focused on the robotics of an automated and high-throughput cell culture system. Automated robotic cultivation of stem or progenitor cells in clinical trials has not been reported till date. The system AutoCulture used in this study can automatically replace the culture medium, centrifuge cells, split cells, and take photographs for morphological assessment. We examined the feasibility of this system in a clinical setting.

RESULTS

We observed similar characteristics by both the culture methods in terms of the growth rate, gene expression profile, cell surface profile by fluorescence-activated cell sorting, surface glycan profile, and genomic DNA stability. These results indicate that AutoCulture is a feasible method for the cultivation of human cells for regenerative medicine.

CONCLUSIONS

An automated cell-processing machine will play important roles in cell therapy and have widespread use from application in multicenter trials to provision of off-the-shelf cell products.

Automated method for the rapid and precise estimation of adherent cell culture characteristics from phase contrast microscopy images

The quantitative determination of key adherent cell culture characteristics such as confluency, morphology, and cell density is necessary for the evaluation of experimental outcomes and to provide a suitable basis for the establishment of robust cell culture protocols. Automated processing of images acquired using phase contrast microscopy (PCM), an imaging modality widely used for the visual inspection of adherent cell cultures, could enable the non-invasive determination of these characteristics. We present an image-processing approach that accurately detects cellular objects in PCM images through a combination of local contrast thresholding and post hoc correction of halo artifacts. The method was thoroughly validated using a variety of cell lines, microscope models and imaging conditions, demonstrating consistently high segmentation performance in all cases and very short processing times (<1 s per 1,208 × 960 pixels image). Based on the high segmentation performance, it was possible to precisely determine culture confluency, cell density, and the morphology of cellular objects, demonstrating the wide applicability of our algorithm for typical microscopy image processing pipelines. Furthermore, PCM image segmentation was used to facilitate the interpretation and analysis of fluorescence microscopy data, enabling the determination of temporal and spatial expression patterns of a fluorescent reporter. We created a software toolbox (PHANTAST) that bundles all the algorithms and provides an easy to use graphical user interface. Source-code for MATLAB and ImageJ is freely available under a permissive open-source license. Biotechnol. Bioeng. 2014;111: 504–517. © 2013 Wiley Periodicals, Inc.

Oxygen-controlled automated neural differentiation of mouse embryonic stem cells

Automation and oxygen tension control are two tools that provide significant improvements to the reproducibility and efficiency of stem cell production processes.

AIM

the aim of this study was to establish a novel automation platform capable of controlling oxygen tension during both the cell-culture and liquid-handling steps of neural differentiation processes.

MATERIALS & METHODS

We built a bespoke automation platform, which enclosed a liquid-handling platform in a sterile, oxygen-controlled environment. An airtight connection was used to transfer cell culture plates to and from an automated oxygen-controlled incubator.

RESULTS

Our results demonstrate that our system yielded comparable cell numbers, viabilities, metabolism profiles and differentiation efficiencies when compared with traditional manual processes. Interestingly, eliminating exposure to ambient conditions during the liquid-handling stage resulted in significant improvements in the yield of MAP2-positive neural cells, indicating that this level of control can improve differentiation processes.

CONCLUSION

This article describes, for the first time, an automation platform capable of maintaining oxygen tension control during both the cell-culture and liquid-handling stages of a 2D embryonic stem cell differentiation process.

Reproducible culture and differentiation of mouse embryonic stem cells using an automated microwell platform

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We describe an automated platform for hands-free ESC expansion and differentiation.

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Key bioprocess variables were investigated to optimize culture inductions.

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Cell growth was more consistent with automated ESC expansion than manual culture.

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ESCs expanded on the automated platform maintained high levels of pluripotency.

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Cells expressed βIII-tubulin after successful automated neuronal differentiation.

The use of embryonic stem cells (ESCs) and their progeny in high throughput drug discovery and regenerative medicine will require production at scale of well characterized cells at an appropriate level of purity. The adoption of automated bioprocessing techniques offers the possibility to overcome the lack of consistency and high failure rates seen with current manual protocols. To build the case for increased use of automation this work addresses the key question: “can an automated system match the quality of a highly skilled and experienced person working manually?” To answer this we first describe an integrated automation platform designed for the ‘hands-free’ culture and differentiation of ESCs in microwell formats. Next we outline a framework for the systematic investigation and optimization of key bioprocess variables for the rapid establishment of validatable Standard Operating Procedures (SOPs). Finally the experimental comparison between manual and automated bioprocessing is exemplified by expansion of the murine Oct-4-GiP ESC line over eight sequential passages with their subsequent directed differentiation into neural precursors. Our results show that ESCs can be effectively maintained and differentiated in a highly reproducible manner by the automated system described. Statistical analysis of the results for cell growth over single and multiple passages shows up to a 3-fold improvement in the consistency of cell growth kinetics with automated passaging. The quality of the cells produced was evaluated using a panel of biological markers including cell growth rate and viability, nutrient and metabolite profiles, changes in gene expression and immunocytochemistry. Automated processing of the ESCs had no measurable negative effect on either their pluripotency or their ability to differentiate into the three embryonic germ layers. Equally important is that over a 6-month period of culture without antibiotics in the medium, we have not had any cases of culture contamination. This study thus confirms the benefits of adopting automated bioprocess routes to produce cells for therapy and for use in basic discovery research.

Process quality engineering for bioreactor-driven manufacturing of tissue-engineered constructs for bone regeneration

The incorporation of Quality-by-Design (QbD) principles in tissue-engineering bioprocess development toward clinical use will ensure that manufactured constructs possess prerequisite quality characteristics addressing emerging regulatory requirements and ensuring the functional in vivo behavior. In this work, the QbD principles were applied on a manufacturing process step for the in vitro production of osteogenic three-dimensional (3D) hybrid scaffolds that involves cell matrix deposition on a 3D titanium (Ti) alloy scaffold. An osteogenic cell source (human periosteum-derived cells) cultured in a bioinstructive medium was used to functionalize regular Ti scaffolds in a perfusion bioreactor, resulting in an osteogenic hybrid carrier. A two-level three-factor fractional factorial design of experiments was employed to explore a range of production-relevant process conditions by simultaneously changing value levels of the following parameters: flow rate (0.5-2 mL/min), cell culture duration (7-21 days), and cell-seeding density (1.5×10(3)-3×10(3) cells/cm(2)). This approach allowed to evaluate the individual impact of the aforementioned process parameters upon key quality attributes of the produced hybrids, such as collagen production, mineralization level, and cell number. The use of a fractional factorial design approach helped create a design space in which hybrid scaffolds of predefined quality attributes may be robustly manufactured while minimizing the number of required experiments.

Application of response surface methodology to maximize the productivity of scalable automated human embryonic stem cell manufacture

Aim: Commercial regenerative medicine will require large quantities of clinical-specification human cells. The cost and quality of manufacture is notoriously difficult to control due to highly complex processes with poorly defined tolerances. As a step to overcome this, we aimed to demonstrate the use of ‘quality-by-design’ tools to define the operating space for economic passage of a scalable human embryonic stem cell production method with minimal cell loss. Materials & methods: Design of experiments response surface methodology was applied to generate empirical models to predict optimal operating conditions for a unit of manufacture of a previously developed automatable and scalable human embryonic stem cell production method. Results & conclusion: Two models were defined to predict cell yield and cell recovery rate postpassage, in terms of the predictor variables of media volume, cell seeding density, media exchange and length of passage. Predicted operating conditions for maximized productivity were successfully validated. Such ‘quality-by-design’ type approaches to process design and optimization will be essential to reduce the risk of product failure and patient harm, and to build regulatory confidence in cell therapy manufacturing processes.

How can measurement, monitoring, modeling and control advance cell culture in industrial biotechnology?

This report highlights the potential of measurement, monitoring, modeling and control (M(3) C) methodologies in animal and human cell culture technology. In particular, state-of-the-art of M(3) C technologies and their industrial relevance of existing technology are addressed. It is a summary of an expert panel discussion between biotechnologists and biochemical engineers with both academic and industrial backgrounds. The latest ascents in M(3) C are discussed from a cell culture perspective for industrial process development and production needs. The report concludes with a set of recommendations for targeting M(3) C research toward the industrial interests. These include issues of importance for biotherapeutics production, miniaturization of measurement techniques and modeling methods.

Precision manufacturing for clinical-quality regenerative medicines

Innovations in engineering applied to healthcare make a significant difference to people's lives. Market growth is guaranteed by demographics. Regulation and requirements for good manufacturing practice-extreme levels of repeatability and reliability-demand high-precision process and measurement solutions. Emerging technologies using living biological materials add complexity. This paper presents some results of work demonstrating the precision automated manufacture of living materials, particularly the expansion of populations of human stem cells for therapeutic use as regenerative medicines. The paper also describes quality engineering techniques for precision process design and improvement, and identifies the requirements for manufacturing technology and measurement systems evolution for such therapies.

Developing assays to address identity, potency, purity and safety: cell characterization in cell therapy process development

A major challenge to commercializing cell-based therapies is developing scalable manufacturing processes while maintaining the critical quality parameters (identity, potency, purity, safety) of the final live cell product. Process development activities such as extended passaging and serum reduction/elimination can facilitate the streamlining of cell manufacturing process as long as the biological functions of the product remain intact. Best practices in process development will be dependent on cell characterization; a thorough understanding of the cell-based product. Unique biological properties associated with different types of cell-based products are discussed. Cell characterization may be used as a tool for successful process development activities, which can promote a candidate cell therapy product through clinical development and ultimately to a commercialized product.

Environmental parameters influence non-viral transfection of human mesenchymal stem cells for tissue engineering applications

Non-viral transfection is a promising technique that could be used to increase the therapeutic potential of stem cells. The purpose of this study was to explore practical culture parameters of relevance in potential human mesenchymal stem cell (hMSC) clinical and tissue engineering applications, including type of polycationic transfection reagent, N/P ratio and dose of polycation/pDNA polyplexes, cell passage number, cell density and cell proliferation. The non-viral transfection efficiency was significantly influenced by N/P ratio, polyplex dose, cell density and cell passage number. hMSC culture conditions that inhibited cell division also decreased transfection efficiency, suggesting that strategies to promote hMSC proliferation may be useful to enhance transfection efficiency in future tissue engineering studies. Non-viral transfection treatments influenced hMSC phenotype, including the expression level of the hMSC marker CD105 and the ability of hMSCs to differentiate down the osteogenic and adipogenic lineages. The parameters found here to promote hMSC transfection efficiency, minimize toxicity and influence hMSC phenotype may be instructive in future non-viral transfection studies and tissue engineering applications.

Automated adherent human cell culture (mesenchymal stem cells)

Human cell culture processes developed at research laboratory scale need to be translated to large-scale production processes to achieve commercial application to a large market. To allow this transition of scale with consistent process performance and control of costs, it will be necessary to reduce manual processing and increase automation. There are a number of commercially available platforms that will reduce manual process intervention and improve process control for different culture formats. However, in many human cell-based applications, there is currently a need to remain close to the development format, usually adherent culture on cell culture plastic or matrix-coated wells or flasks due to deterioration of cell quality in other environments, such as suspension. This chapter presents an example method for adherent automated human stem cell culture using a specific automated flask handling platform, the CompacT SelecT.

Characterization and optimization of cell seeding in scaffolds by factorial design: quality by design approach for skeletal tissue engineering

Cell seeding into scaffolds plays a crucial role in the development of efficient bone tissue engineering constructs. Hence, it becomes imperative to identify the key factors that quantitatively predict reproducible and efficient seeding protocols. In this study, the optimization of a cell seeding process was investigated using design of experiments (DOE) statistical methods. Five seeding factors (cell type, scaffold type, seeding volume, seeding density, and seeding time) were selected and investigated by means of two response parameters, critically related to the cell seeding process: cell seeding efficiency (CSE) and cell-specific viability (CSV). In addition, cell spatial distribution (CSD) was analyzed by Live/Dead staining assays. Analysis identified a number of statistically significant main factor effects and interactions. Among the five seeding factors, only seeding volume and seeding time significantly affected CSE and CSV. Also, cell and scaffold type were involved in the interactions with other seeding factors. Within the investigated ranges, optimal conditions in terms of CSV and CSD were obtained when seeding cells in a regular scaffold with an excess of medium. The results of this case study contribute to a better understanding and definition of optimal process parameters for cell seeding. A DOE strategy can identify and optimize critical process variables to reduce the variability and assists in determining which variables should be carefully controlled during good manufacturing practice production to enable a clinically relevant implant.

Current understanding and challenges in bioprocessing of stem cell-based therapies for regenerative medicine

BACKGROUND

A novel manufacturing industry is emerging to translate unique cellular therapy bioprocesses to robust, scaled manufacturing production for successful clinical translation.

SOURCE OF DATA

This review summarizes key translational issues, and current and future perspectives to improve translation of cell-based therapy bioprocessing, based on literature search and author research.

AREAS OF AGREEMENT

It is widely recognized that cell-based therapies could revolutionize health care for a range of diseases, and that there are gaps in the overarching framework and technologies to generate clinical success.

AREAS OF CONTROVERSY

There is limited understanding of how to fulfil requirements as regulatory and manufacturing guidelines are incomplete and few have achieved commercialization.

GROWING POINTS

Recent developments are encouraging adoption of automation and quality engineering approaches for bioprocessing of cell-based therapies.

AREAS TIMELY FOR DEVELOPING RESEARCH

Include technology development to improve the cost and purity of manufacture and final product quality.

Adventures in time and space: Nonlinearity and complexity of cytokine effects on stem cell fate decisions

Cytokines are central factors in the control of stem cell fate decisions and, as such, they are invaluable to those interested in the manipulation of stem and progenitor cells for clinical or research purposes. In their in vivo niches or in optimized cultures, stem cells are exposed to multiple cytokines, matrix proteins and other cell types that provide individual and combinatorial signals that influence their self-renewal, proliferation and differentiation. Although the individual effects of cytokines are well-characterized in terms of increases or decreases in stem cell expansion or in the production of specific cell lineages, their interactions are often overlooked. Factorial design experiments in association with multiple linear regression is a powerful multivariate approach to derive response-surface models and to obtain a quantitative understanding of cytokine dose and interactions effects. On the other hand, cytokine interactions detected in stem cell processes can be difficult to interpret due to the fact that the cell populations examined are often heterogeneous, that cytokines can exhibit pleiotropy and redundancy and that they can also be endogenously produced. This perspective piece presents a list of possible biological mechanisms that can give rise to positive and negative two-way factor interactions in the context of in vivo and in vitro stem cell-based processes. These interpretations are based on insights provided by recent studies examining intra- and extra-cellular signaling pathways in adult and embryonic stem cells. Cytokine interactions have been classified according to four main types of molecular and cellular mechanisms: (i) interactions due to co-signaling; (ii) interactions due to sequential actions; (iii) interactions due to high-dose saturation and inhibition; and (iv) interactions due to intercellular signaling networks. For each mechanism, possible patterns of regression coefficients corresponding to the cytokine main effects, quadratic effects and two-way interactions effects are provided. Finally, directions for future mechanistic studies are presented.

Human mesenchymal stem cells and their use in cell-based therapies

The human population is increasingly facing various diseases, including types of cancer, that cannot be cured with conventional drugs. Advanced drug targeting of tumor cells is also often impossible when treating highly invasive and infiltrative tumors such as glioblastoma or pulmonary cancer, because of tumor cells' high migration and invasiveness. Pluripotent human mesenchymal stem cells (hMSCs) have been extensively studied, and strategies are being proposed for treating "incurable" cancers and injury/disease-affected organs. Because of their own intrinsic properties, involving homing and immunomodulatory potency, hMSCs could be used as an excellent cell/drug delivery vehicle in those cell-based therapies. Their unprecedented use has been shadowed, however, by their spontaneous transformation, which links them to cancer-initiating cells during tumor development. How malignant initiation proceeds in vivo, and what are the exact characteristics of the cancer-initiating cells, still remain to be investigated. In the present review, the authors summed up the most recent knowledge about hMSC characteristics, their malignant transformation, and outlined the possibilities of their safe use in novel cell-based therapies.

Human cell culture process capability: a comparison of manual and automated production

Cell culture is one of the critical bioprocessing steps required to generate sufficient human-derived cellular material for most cell-based therapeutic applications in regenerative medicine. Automated cell expansion is fundamental to the development of scaled, robust and cost effective commercial production processes for cell-based therapeutic products. This paper describes the first application of process capability analysis to establish and compare the short-term process capability of manual and automated processes for the in vitro expansion of a selected anchorage-dependent cell line. Estimates of the process capability indices (Cp, Cpk) have been used to assess the ability of both processes to consistently meet the requirements for a selected productivity output and to direct process improvement activities. Point estimates of Cp and Cpk show that the manual process has poor capability (Cp = 0.55, Cpk = 0.26) compared to the automated process (Cp = 1.32, Cpk = 0.25), resulting from excess variability. Comparison of point estimates, which shows that Cpk < Cp, indicates that the automated process mean was off-centre and that intervention is required to adjust the location of the process mean. A process improvement strategy involving an adjustment to the automated process settings has demonstrated in principle that the process mean can be shifted closer to the centre of the specification to achieve an estimated seven-fold improvement in process performance. In practice, the 90% confidence bound estimate of Cp (Cp = 0.90) indicates that that once the process is centred within the specification, a further reduction of process variation is required to attain an automated process with the desired minimum capability requirement.

Automating the expansion process of human skeletal muscle myoblasts with suppression of myotube formation

An intelligent culture system accompanied by automated operations (liquid transfer and cell passage) was newly developed to perform serial cultures of human skeletal muscle myoblasts. To realize a desired performance, a laminin-coated surface was applied to myoblast expansion in a culture flask. It was found that the laminin coating enhanced the overall growth ability attributable not to shortening of the doubling time but to prevention of differentiation toward myotube formation, compared with that on a conventional plain surface. In addition, the effects of seeding density and confluence degree on the growth were investigated quantitatively in terms of cell attachment and division as well as proliferative cell population in the culture on the laminin-coated surface. With increasing in seeding density, the number of proliferative cells decreased at the end of culture accompanied by an increase in the confluence degree, which caused poor attachment of the passaged cells on the surface in the subsequent culture. The quantitative analyses of these cell behaviors helped us determine the appropriate seeding density and attainable confluence degree during one passage, which were 1.0 x 10(3) cells/cm(2) and 0.5 as the initial and boundary conditions, respectively. An automated culture system that could manage two serial cultures by monitoring the confluence degree was constructed. The automated operation with the intelligent determination of the time for passage was successfully performed without serious loss of growth activity, compared with manual operation using conventional flasks. These results indicated that the monitoring of confluence degree is effective to perform the culture passage of myoblasts, being contributable to automating the cell expansion process.

Optimizing mesenchymal stem cell-based therapeutics

Mesenchymal stem cell (MSC)-based therapeutics are showing significant benefit in multiple clinical trials conducted by both academic and commercial organizations, but obstacles remain for their large-scale commercial implementation. Recent studies have attempted to optimize MSC-based therapeutics by either enhancing their potency or increasing their delivery to target tissues. Overexpression of trophic factors or in vitro exposure to potency-enhancing factors are two approaches that are demonstrating success in preclinical animal models. Delivery enhancement strategies involving tissue-specific cytokine pathways or binding sites are also showing promise. Each of these strategies has its own set of distinct advantages and disadvantages when viewed with a mindset of ultimate commercialization and clinical utility.

Automated, scalable culture of human embryonic stem cells in feeder-free conditions

Large-scale manufacture of human embryonic stem cells (hESCs) is prerequisite to their widespread use in biomedical applications. However, current hESC culture strategies are labor-intensive and employ highly variable processes, presenting challenges for scaled production and commercial development. Here we demonstrate that passaging of the hESC lines, HUES7, and NOTT1, with trypsin in feeder-free conditions, is compatible with complete automation on the CompacT SelecT, a commercially available and industrially relevant robotic platform. Pluripotency was successfully retained, as evidenced by consistent proliferation during serial passage, expression of stem cell markers (OCT4, NANOG, TRA1-81, and SSEA-4), stable karyotype, and multi-germlayer differentiation in vitro, including to pharmacologically responsive cardiomyocytes. Automation of hESC culture will expedite cell-use in clinical, scientific, and industrial applications.