Scalable expansion of human pluripotent stem cells in suspension culture. Nat Protoc. 2011;6:689-700. [PMID: 21527925 DOI: 10.1038/nprot.2011.318]

Chemically defined production of engineered cardiac tissue microspheres from hydrogel-encapsulated pluripotent stem cells

Chemically defined, suspension culture conditions are a key requirement in realizing clinical translation of engineered cardiac tissues (ECTs). Building on our previous work producing functional ECT microspheres through differentiation of biomaterial encapsulated human induced pluripotent stem cells (hiPSCs), here we establish the ability to use chemically defined culture conditions, including stem cell media (E8) and cardiac differentiation media (chemically defined differentiation media with three components, CDM3). A custom microfluidic cell encapsulation system was used to encapsulate hiPSCs at a range of initial cell concentrations and diameters in the hybrid biomaterial, poly(ethylene glycol)-fibrinogen (PF), for the formation of highly spherical and uniform ECT microspheres for subsequent cardiac differentiation. Initial microsphere diameter could be tightly controlled, and microspheres could be produced with an initial diameter between 400 and 800 µm. Three days after encapsulation, cardiac differentiation was initiated through small molecule modulation of Wnt signaling in CDM3. Cardiac differentiation occurred resulting in in situ ECT formation; results showed that this differentiation protocol could be used to achieve cardiomyocyte (CM) contents greater than 90%, although there was relatively high variability in CM content and yield between differentiation batches. Spontaneous contraction of ECT microspheres initiated between Days 7 and 10 of differentiation and ECT microspheres responded to electrical pacing up to 1.5 Hz. Resulting CMs had well-defined sarcomeres and the gap junction protein, connexin 43, and had appropriate temporal changes in gene expression. In summary, this study demonstrated the proof-of-concept to produce functional ECT microspheres with chemically defined media in suspension culture in combination with biomaterial support of microsphere encapsulated hiPSCs.

Robust bioprocess design and evaluation of commercial media for the serial expansion of human induced pluripotent stem cell aggregate cultures in vertical-wheel bioreactors

BACKGROUND

While pluripotent stem cell (PSC) therapies move toward clinical and commercial applications at a rapid rate, manufacturing reproducibility and robustness are notable bottlenecks in regulatory approval. Therapeutic applications of PSCs require large cell quantities to be generated under highly robust, well-defined, and economically viable conditions. Small-scale and short-term process optimization, however, is often performed in a linear fashion that does not account for time needed to verify the bioprocess protocols and analysis methods used. Design of a reproducible and robust bioprocess should be dynamic and include a continuous effort to understand how the process will respond over time and to different stresses before transitioning into large-scale production where stresses will be amplified.

METHODS

This study utilizes a baseline protocol, developed for the short-term culture of PSC aggregates in Vertical-Wheel® bioreactors, to evaluate key process attributes through long-term (serial passage) suspension culture. This was done to access overall process robustness when performed with various commercially available media and cell lines. Process output variables including growth kinetics, aggregate morphology, harvest efficiency, genomic stability, and functional pluripotency were assessed through short and long-term culture.

RESULTS

The robust nature of the expansion protocol was demonstrated over a six-day culture period where spherical aggregate formation and expansion were observed with high-fold expansions for all five commercial media tested. Profound differences in cell growth and quality were revealed only through long-term serial expansion and in-vessel dissociation operations. Some commercial media formulations tested demonstrated maintenance of cell growth rates, aggregate morphology, and high harvest recovery efficiencies through three bioreactor serial passages using multiple PSC lines. Exceptional bioprocess robustness was even demonstrated with sustained growth and quality maintenance over 10 serial bioreactor passages. However, some commercial media tested proved less equipped for serial passage cultures in bioreactors as cultures led to cell lysis during dissociation, reduction in growth rates, and a loss of aggregate morphology.

CONCLUSIONS

This study demonstrates the importance of systematic selection and testing of bioprocess input variables, with multiple bioprocess output variables through serial passages to create a truly reproducible and robust protocol for clinical and commercial PSC production using scalable bioreactor systems.

Label-Free Single Microparticles and Cell Aggregates Sorting in Continuous Cell-Based Manufacturing

There is a paradigm shift in biomanufacturing toward continuous bioprocessing but cell-based manufacturing using adherent and suspension cultures, including microcarriers, hydrogel microparticles, and 3D cell aggregates, remains challenging due to the lack of efficient in-line bioprocess monitoring and cell harvesting tools. Herein, a novel label-free microfluidic platform for high throughput (≈50 particles/sec) impedance bioanalysis of biomass, cell viability, and stem cell differentiation at single particle resolution is reported. The device is integrated with a real-time piezo-actuated particle sorter based on user-defined multi-frequency impedance signatures. Biomass profiling of Cytodex-3 microcarriers seeded with adipose-derived mesenchymal stem cells (ADSCs) is first performed to sort well-seeded or confluent microcarriers for downstream culture or harvesting, respectively. Next, impedance-based isolation of microcarriers with osteogenic differentiated ADSCs is demonstrated, which is validated with a twofold increase of calcium content in sorted ADSCs. Impedance profiling of heterogenous ADSCs-encapsulated hydrogel (alginate) microparticles and 3D ADSC aggregate mixtures is also performed to sort particles with high biomass and cell viability to improve cell quality. Overall, the scalable microfluidic platform technology enables in-line sample processing from bioreactors directly and automated analysis of cell quality attributes to maximize cell yield and improve the control of cell quality in continuous cell-based manufacturing.

Standardized production of hPSC-derived cardiomyocyte aggregates in stirred spinner flasks

A promising cell-therapy approach for heart failure aims at differentiating human pluripotent stem cells (hPSCs) into functional cardiomyocytes (CMs) in vitro to replace the disease-induced loss of patients' heart muscle cells in vivo. But many challenges remain for the routine clinical application of hPSC-derived CMs (hPSC-CMs), including good manufacturing practice (GMP)-compliant production strategies. This protocol describes the efficient generation of hPSC-CM aggregates in suspension culture, emphasizing process simplicity, robustness and GMP compliance. The strategy promotes clinical translation and other applications that require large numbers of CMs. Using a simple spinner-flask platform, this protocol is applicable to a broad range of users with general experience in handling hPSCs without extensive know-how in biotechnology. hPSCs are expanded in monolayer to generate the required cell numbers for process inoculation in suspension culture, followed by stirring-controlled formation of cell-only aggregates at a 300-ml scale. After 48 h at checkpoint (CP) 0, chemically defined cardiac differentiation is induced by WNT-pathway modulation through use of the glycogen-synthase kinase-3 inhibitor CHIR99021 (WNT agonist), which is replaced 24 h later by the chemical WNT-pathway inhibitor IWP-2. The exact application of the described process parameters is important to ensure process efficiency and robustness. After 10 d of differentiation (CP I), the production of ≥100 × 106 CMs is expected. Moreover, to 'uncouple' cell production from downstream applications, continuous maintenance of CM aggregates for up to 35 d in culture (CP II) is demonstrated without a reduction in CM content, supporting downstream logistics while potentially overcoming the requirement for cryopreservation.

Unlocking the Future: Pluripotent Stem Cell-Based Lung Repair

The human respiratory system is susceptible to a variety of diseases, ranging from chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis to acute respiratory distress syndrome (ARDS). Today, lung diseases represent one of the major challenges to the health care sector and represent one of the leading causes of death worldwide. Current treatment options often focus on managing symptoms rather than addressing the underlying cause of the disease. The limitations of conventional therapies highlight the urgent clinical need for innovative solutions capable of repairing damaged lung tissue at a fundamental level. Pluripotent stem cell technologies have now reached clinical maturity and hold immense potential to revolutionize the landscape of lung repair and regenerative medicine. Meanwhile, human embryonic (HESCs) and human-induced pluripotent stem cells (hiPSCs) can be coaxed to differentiate into lung-specific cell types such as bronchial and alveolar epithelial cells, or pulmonary endothelial cells. This holds the promise of regenerating damaged lung tissue and restoring normal respiratory function. While methods for targeted genetic engineering of hPSCs and lung cell differentiation have substantially advanced, the required GMP-grade clinical-scale production technologies as well as the development of suitable preclinical animal models and cell application strategies are less advanced. This review provides an overview of current perspectives on PSC-based therapies for lung repair, explores key advances, and envisions future directions in this dynamic field.

Matrix-free human pluripotent stem cell manufacturing by seed train approach and intermediate cryopreservation

BACKGROUND

Human pluripotent stem cells (hPSCs) have an enormous therapeutic potential, but large quantities of cells will need to be supplied by reliable, economically viable production processes. The suspension culture (three-dimensional; 3D) of hPSCs in stirred tank bioreactors (STBRs) has enormous potential for fuelling these cell demands. In this study, the efficient long-term matrix-free suspension culture of hPSC aggregates is shown.

METHODS AND RESULTS

STBR-controlled, chemical aggregate dissociation and optimized passage duration of 3 or 4 days promotes exponential hPSC proliferation, process efficiency and upscaling by a seed train approach. Intermediate high-density cryopreservation of suspension-derived hPSCs followed by direct STBR inoculation enabled complete omission of matrix-dependent 2D (two-dimensional) culture. Optimized 3D cultivation over 8 passages (32 days) cumulatively yielded ≈4.7 × 1015 cells, while maintaining hPSCs' pluripotency, differentiation potential and karyotype stability. Gene expression profiling reveals novel insights into the adaption of hPSCs to continuous 3D culture compared to conventional 2D controls.

CONCLUSIONS

Together, an entirely matrix-free, highly efficient, flexible and automation-friendly hPSC expansion strategy is demonstrated, facilitating the development of good manufacturing practice-compliant closed-system manufacturing in large scale.

Growth prolongation of human induced pluripotent stem cell aggregate in three-dimensional suspension culture system by addition of botulinum hemagglutinin

Human induced pluripotent stem cells (hiPSCs) can be used in regenerative therapy as an irresistible cell source, and so the development of scalable production of hiPSCs for three-dimensional (3D) suspension culture is required. In this study, we established a simple culture strategy for improving hiPSC aggregate growth using botulinum hemagglutinin (HA), which disrupts cell-cell adhesion mediated by E-cadherin. When HA was added to the suspension culture of hiPSC aggregates, E-cadherin-mediated cell-cell adhesion was temporarily disrupted within 24 h, but then recovered. Phosphorylated myosin light chain, a contractile force marker, was also recovered at the periphery of hiPSC aggregates. The cell aggregates were suppressed the formation of collagen type I shell-like structures at the periphery by HA and collagen type I was homogenously distributed within the cell aggregates. In addition, these cell aggregates retained the proliferation marker Ki-67 throughout the cell aggregates. The apparent specific growth rate with HA addition was maintained continuously throughout the culture, and the final cell density was 1.7-fold higher than that in the control culture. These cells retained high expression levels of pluripotency markers. These observations indicated that relaxation of cell-cell adhesions by HA addition induced rearrangement of the mechanical tensions generated by actomyosin in hiPSC aggregates and suppression of collagen type I shell-like structure formation. These results suggest that this simple and readily culture strategy is a potentially useful tool for improving the scalable production of hiPSCs for 3D suspension cultures.

Inducible Pluripotent Suspension Cell Cultures (iPSCs) to Study Plant Cell Differentiation

Inducing the differentiation of specific cell type(s) synchronously and on-demand is a great experimental system to understand the sequential progression of the cellular processes, their timing and their resulting properties for distinct isolated plant cells independently of their tissue context. The inducible differentiation in cell suspension cultures, moreover, enables to obtain large quantities of distinct cell types at specific development stage, which is not possible when using whole plants. The differentiation of tracheary elements (TEs) - the cell type responsible for the hydro-mineral sap conduction and skeletal support of plants in xylem tissues - has been the most studied using inducible cell suspension cultures. We herein describe how to establish and use inducible pluripotent suspension cell cultures (iPSCs) in Arabidopsis thaliana to trigger on-demand different cell types, such as TEs or mesophyll cells. We, moreover, describe the methods to establish, monitor, and modify the sequence, duration, and properties of differentiated cells using iPSCs.

Analysis of the effects of bench-scale cell culture platforms and inoculum cell concentrations on PSC aggregate formation and culture

Introduction: Human pluripotent stem cells (hPSCs) provide many opportunities for application in regenerative medicine due to their ability to differentiate into cells from all three germ layers, proliferate indefinitely, and replace damaged or dysfunctional cells. However, such cell replacement therapies require the economical generation of clinically relevant cell numbers. Whereas culturing hPSCs as a two-dimensional monolayer is widely used and relatively simple to perform, their culture as suspended three-dimensional aggregates may enable more economical production in large-scale stirred tank bioreactors. To be more relevant to this biomanufacturing, bench-scale differentiation studies should be initiated from aggregated hPSC cultures. Methods: We compared five available bench-scale platforms for generating undifferentiated cell aggregates of human embryonic stem cells (hESCs) using AggreWell™ plates, low attachment plates on an orbital shaker, roller bottles, spinner flasks, and vertical-wheel bioreactors (PBS-Minis). Thereafter, we demonstrated the incorporation of an hPSC aggregation step prior to directed differentiation to pancreatic progenitors and endocrine cells. Results and discussion: The AggreWell™ system had the highest aggregation yield. The initial cell concentrations had an impact on the size of aggregates generated when using AggreWell™ plates as well as in roller bottles. However, aggregates made with low attachment plates, spinner flasks and PBS-Minis were similar regardless of the initial cell number. Aggregate morphology was compact and relatively homogenously distributed in all platforms except for the roller bottles. The size of aggregates formed in PBS-Minis was modulated by the agitation rate during the aggregation. In all cell culture platforms, the net growth rate of cells in 3D aggregates was lower (range: -0.01-0.022 h-1) than cells growing as a monolayer (range: 0.039-0.045 h-1). Overall, this study describes operating ranges that yield high-quality undifferentiated hESC aggregates using several of the most commonly used bench-scale cell culture platforms. In all of these systems, methods were identified to obtain PSC aggregates with greater than 70% viability, and mean diameters between 60 and 260 mm. Finally, we showed the capacity of hPSC aggregates formed with PBS-Minis to differentiate into viable pancreatic progenitors and endocrine cell types.

Stem cell culture and differentiation in 3-D scaffolds

Conventional two-dimensional (2-D) cultivation are easy to utilize for human pluripotent stem (hPS) cell cultivation in standard techniques and are important for analysis or development of the signal pathways to keep pluripotent state of hPS cells cultivated on 2-D cell culture materials. However, the most efficient protocol to prepare hPS cells is the cell culture in a three dimensional (3-D) cultivation unit because huge numbers of hPS cells should be utilized in clinical treatment. Some 3-D cultivation strategies for hPS cells are considered: (a) microencapsulated cell cultivation in suspended hydrogels, (b) cell cultivation on microcarriers (MCs), (c) cell cultivation on self-aggregated spheroid [cell aggregates; embryoid bodies (EBs) and organoids], (d) cell cultivation on microfibers or nanofibers, and (e) cell cultivation in macroporous scaffolds. These cultivation ways are described in this chapter.

Suspension culture improves iPSC expansion and pluripotency phenotype

BACKGROUND

Induced pluripotent stem cells (iPSCs) offer potential to revolutionize regenerative medicine as a renewable source for islets, dopaminergic neurons, retinal cells, and cardiomyocytes. However, translation of these regenerative cell therapies requires cost-efficient mass manufacturing of high-quality human iPSCs. This study presents an improved three-dimensional Vertical-Wheel® bioreactor (3D suspension) cell expansion protocol with comparison to a two-dimensional (2D planar) protocol.

METHODS

Sendai virus transfection of human peripheral blood mononuclear cells was used to establish mycoplasma and virus free iPSC lines without common genetic duplications or deletions. iPSCs were then expanded under 2D planar and 3D suspension culture conditions. We comparatively evaluated cell expansion capacity, genetic integrity, pluripotency phenotype, and in vitro and in vivo pluripotency potential of iPSCs.

RESULTS

Expansion of iPSCs using Vertical-Wheel® bioreactors achieved 93.8-fold (IQR 30.2) growth compared to 19.1 (IQR 4.0) in 2D (p < 0.0022), the largest expansion potential reported to date over 5 days. 0.5 L Vertical-Wheel® bioreactors achieved similar expansion and further reduced iPSC production cost. 3D suspension expanded cells had increased proliferation, measured as Ki67⁺ expression using flow cytometry (3D: 69.4% [IQR 5.5%] vs. 2D: 57.4% [IQR 10.9%], p = 0.0022), and had a higher frequency of pluripotency marker (Oct4⁺Nanog⁺Sox2⁺) expression (3D: 94.3 [IQR 1.4] vs. 2D: 52.5% [IQR 5.6], p = 0.0079). q-PCR genetic analysis demonstrated a lack of duplications or deletions at the 8 most commonly mutated regions within iPSC lines after long-term passaging (> 25). 2D-cultured cells displayed a primed pluripotency phenotype, which transitioned to naïve after 3D-culture. Both 2D and 3D cells were capable of trilineage differentiation and following teratoma, 2D-expanded cells generated predominantly solid teratomas, while 3D-expanded cells produced more mature and predominantly cystic teratomas with lower Ki67⁺ expression within teratomas (3D: 16.7% [IQR 3.2%] vs.. 2D: 45.3% [IQR 3.0%], p = 0.002) in keeping with a naïve phenotype.

CONCLUSION

This study demonstrates nearly 100-fold iPSC expansion over 5-days using our 3D suspension culture protocol in Vertical-Wheel® bioreactors, the largest cell growth reported to date. 3D expanded cells showed enhanced in vitro and in vivo pluripotency phenotype that may support more efficient scale-up strategies and safer clinical implementation.

Primary Ciliary Dyskinesia Patient-Specific hiPSC-Derived Airway Epithelium in Air-Liquid Interface Culture Recapitulates Disease Specific Phenotypes In Vitro

Primary ciliary dyskinesia (PCD) is a rare heterogenic genetic disorder associated with perturbed biogenesis or function of motile cilia. Motile cilia dysfunction results in diminished mucociliary clearance (MCC) of pathogens in the respiratory tract and chronic airway inflammation and infections successively causing progressive lung damage. Current approaches to treat PCD are symptomatic, only, indicating an urgent need for curative therapeutic options. Here, we developed an in vitro model for PCD based on human induced pluripotent stem cell (hiPSC)-derived airway epithelium in Air-Liquid-Interface cultures. Applying transmission electron microscopy, immunofluorescence staining, ciliary beat frequency, and mucociliary transport measurements, we could demonstrate that ciliated respiratory epithelia cells derived from two PCD patient-specific hiPSC lines carrying mutations in DNAH5 and NME5, respectively, recapitulate the respective diseased phenotype on a molecular, structural and functional level.

Scalable expansion of iPSC and their derivatives across multiple lineages

Induced pluripotent stem cell (iPSC) technology enabled the production of pluripotent stem cell lines from somatic cells from a range of known genetic backgrounds. Their ability to differentiate and generate a wide variety of cell types has resulted in their use for various biomedical applications, including toxicity testing. Many of these iPSC lines are now registered in databases and stored in biobanks such as the European Bank for induced pluripotent Stem Cells (EBiSC), which can streamline the quality control and distribution of these individual lines. To generate the quantities of cells for banking and applications like high-throughput toxicity screening, scalable and robust methods need to be developed to enable the large-scale production of iPSCs. 3D suspension culture platforms are increasingly being used by stem cell researchers, owing to a higher cell output in a smaller footprint, as well as simpler scaling by increasing culture volume. Here we describe our strategies for successful scalable production of iPSCs using a benchtop bioreactor and incubator for 3D suspension cultures, while maintaining quality attributes expected of high-quality iPSC lines. Additionally, to meet the increasing demand for "ready-to-use" cell types, we report recent work to establish robust, scalable differentiation protocols to cardiac, neural, and hepatic fate to enable EBiSC to increase available research tools.

Process control and in silico modeling strategies for enabling high density culture of human pluripotent stem cells in stirred tank bioreactors

The routine therapeutic and industrial applications of human pluripotent stem cells (hPSCs) require their constant mass supply by robust, efficient, and economically viable bioprocesses. Our protocol describes the fully controlled expansion of hPSCs in stirred tank bioreactors (STBRs) enabling cell densities of 35 × 10⁶ cells/mL while reducing culture medium consumption by 75%. This is achieved by in silico process modeling and computable upscaling. We provide a detailed blueprint for systematic process development of hPSCs and their progenies. For complete details on the use and execution of this protocol, please refer to Manstein et al. (2021).

Human Induced Pluripotent Stem Cell as a Disease Modeling and Drug Development Platform-A Cardiac Perspective

A comprehensive understanding of the pathophysiology and cellular responses to drugs in human heart disease is limited by species differences between humans and experimental animals. In addition, isolation of human cardiomyocytes (CMs) is complicated because cells obtained by biopsy do not proliferate to provide sufficient numbers of cells for preclinical studies in vitro. Interestingly, the discovery of human-induced pluripotent stem cell (hiPSC) has opened up the possibility of generating and studying heart disease in a culture dish. The combination of reprogramming and genome editing technologies to generate a broad spectrum of human heart diseases in vitro offers a great opportunity to elucidate gene function and mechanisms. However, to exploit the potential applications of hiPSC-derived-CMs for drug testing and studying adult-onset cardiac disease, a full functional characterization of maturation and metabolic traits is required. In this review, we focus on methods to reprogram somatic cells into hiPSC and the solutions for overcome immaturity of the hiPSC-derived-CMs to mimic the structure and physiological properties of the adult human CMs to accurately model disease and test drug safety. Finally, we discuss how to improve the culture, differentiation, and purification of CMs to obtain sufficient numbers of desired types of hiPSC-derived-CMs for disease modeling and drug development platform.

Rock inhibitor may compromise human induced pluripotent stem cells for cardiac differentiation in 3D

Cardiomyocytes differentiated from human induced pluripotent stem cells (iPSCs) are valuable for the understanding/treatment of the deadly heart diseases and their drug screening. However, the very much needed homogeneous 3D cardiac differentiation of human iPSCs is still challenging. Here, it is discovered surprisingly that Rock inhibitor (RI), used ubiquitously to improve the survival/yield of human iPSCs, induces early gastrulation-like change to human iPSCs in 3D culture and may cause their heterogeneous differentiation into all the three germ layers (i.e., ectoderm, mesoderm, and endoderm) at the commonly used concentration (10 μM). This greatly compromises the capacity of human iPSCs for homogeneous 3D cardiac differentiation. By reducing the RI to 1 μM for 3D culture, the human iPSCs retain high pluripotency/quality in inner cell mass-like solid 3D spheroids. Consequently, the beating efficiency of 3D cardiac differentiation can be improved to more than 95 % in ~7 days (compared to less than ~50 % in 14 days for the 10 μM RI condition). Furthermore, the outset beating time (OBT) of all resultant cardiac spheroids (CSs) is synchronized within only 1 day and they form a synchronously beating 3D construct after 5-day culture in gelatin methacrylol (GelMA) hydrogel, showing high homogeneity (in terms of the OBT) in functional maturity of the CSs. Moreover, the resultant cardiomyocytes are of high quality with key functional ultrastructures and highly responsive to cardiac drugs. These discoveries may greatly facilitate the utilization of human iPSCs for understanding and treating heart diseases.

Generation of heart-forming organoids from human pluripotent stem cells

Heart-forming organoids (HFOs) derived from human pluripotent stem cells (hPSCs) are a complex, highly structured in vitro model of early heart, foregut and vasculature development. The model represents a potent tool for various applications, including teratogenicity studies, gene function analysis and drug discovery. Here, we provide a detailed protocol describing how to form HFOs within 14 d. In an initial 4 d preculture period, hPSC aggregates are individually formed in a 96-well format and then Matrigel-embedded. Subsequently, the chemical WNT pathway modulators CHIR99021 and IWP2 are applied, inducing directed differentiation. This highly robust protocol can be used on many different hPSC lines and be combined with manipulation technologies such as gene targeting and drug testing. HFO formation can be assessed by numerous complementary methods, ranging from various imaging approaches to gene expression studies. Here, we highlight the flow cytometry-based analysis of individual HFOs, enabling the quantitative monitoring of lineage formation.

Critical Analysis of cGMP Large-Scale Expansion Process in Bioreactors of Human Induced Pluripotent Stem Cells in the Framework of Quality by Design

Human induced pluripotent stem cells (hiPSCs) are manufactured as advanced therapy medicinal products for tissue replacement applications. With this aim, the feasibility of hiPSC large-scale expansion in existing bioreactor systems under current good manufacturing practices (cGMP) has been tested. Yet, these attempts have lacked a paradigm shift in culture settings and technologies tailored to hiPSCs, which jeopardizes their clinical translation. The best approach for industrial scale-up of high-quality hiPSCs is to design their manufacturing process by following quality-by-design (QbD) principles: a scientific, risk-based framework for process design based on relating product and process attributes to product quality. In this review, we analyzed the hiPSC expansion manufacturing process implementing the QbD approach in the use of bioreactors, stressing the decisive role played by the cell quantity, quality and costs, drawing key QbD concepts directly from the guidelines of the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use.

Acoustic streaming induced by MHz-frequency ultrasound extends the volume limit of cell suspension culture

Large-scale cell suspension culture technology opens up opportunities for numerous medical and bioengineering applications. For these purposes, scale-up of the culture system is paramount. For initial small-scale culture, a simple static suspension culture (SSC) is generally employed. However, cell sedimentation due to the lack of agitation limits the culture volume feasible for SSC. Thus, when scaling up, cell suspensions must be manually transferred from the culture flask to another vessel suitable for agitation, which increases the risk of contamination and human error. Ideally, the number of culture transfer steps should be kept to a minimum. The present study describes the fabrication of an ultrasonic suspension culture system that stirs cell suspensions with the use of acoustic streaming generated by ultrasound irradiation at a MHz frequency. This system was applied to 100-mL suspension cultures of Chinese hamster ovary cells-a volume ten-fold larger than that generally used. The cell proliferation rate in this system was 1.88/day when applying an input voltage of 40 V to the ultrasonic transducer, while that of the SSC was 1.14/day. Hence, the proposed method can extend the volume limit of static cell suspension cultures, thereby reducing the number of cell culture transfer steps.

Application of hiPSCs in tooth regeneration via cellular modulation

BACKGROUND

Induced pluripotent stem cell (iPSC)-based technology provides limitless resources for customized development of organs without any ethical concerns. In theory, iPSCs generated from terminally differentiated cells can be induced to further differentiate into all types of organs that are derived from the embryonic germ layers. Since iPSC reprogramming technology is relatively new, extensive efforts by the researchers have been put together to optimize the protocols to establish in vitro differentiation of human iPSCs (hiPSCs) into various desirable cell types/organs.

HIGHLIGHTS

In the present study, we review the potential application of iPSCs as an efficient alternative to primary cells for modulating signal molecules. Furthermore, an efficient culture system that promotes the differentiation of cell lineages and tissue formation has been reviewed. We also summarize the recent studies wherein tissue engineering of the three germ layers has been explored. Particularly, we focus on the current research strategies for iPSC-based tooth regeneration via molecular modulation.

CONCLUSION

In recent decades, robust knowledge regarding the hiPSC-based regenerative therapy has been accumulated, especially focusing on cellular modulation. This review provides the optimization of the procedures designed to regenerate specific organs.

High density bioprocessing of human pluripotent stem cells by metabolic control and in silico modeling

To harness the full potential of human pluripotent stem cells (hPSCs) we combined instrumented stirred tank bioreactor (STBR) technology with the power of in silico process modeling to overcome substantial, hPSC‐specific hurdles toward their mass production. Perfused suspension culture (3D) of matrix‐free hPSC aggregates in STBRs was applied to identify and control process‐limiting parameters including pH, dissolved oxygen, glucose and lactate levels, and the obviation of osmolality peaks provoked by high density culture. Media supplements promoted single cell‐based process inoculation and hydrodynamic aggregate size control. Wet lab‐derived process characteristics enabled predictive in silico modeling as a new rational for hPSC cultivation. Consequently, hPSC line‐independent maintenance of exponential cell proliferation was achieved. The strategy yielded 70‐fold cell expansion in 7 days achieving an unmatched density of 35 × 10⁶ cells/mL equivalent to 5.25 billion hPSC in 150 mL scale while pluripotency, differentiation potential, and karyotype stability was maintained. In parallel, media requirements were reduced by 75% demonstrating the outstanding increase in efficiency. Minimal input to our in silico model accurately predicts all main process parameters; combined with calculation‐controlled hPSC aggregation kinetics, linear process upscaling is also enabled and demonstrated for up to 500 mL scale in an independent bioreactor system. Thus, by merging applied stem cell research with recent knowhow from industrial cell fermentation, a new level of hPSC bioprocessing is revealed fueling their automated production for industrial and therapeutic applications.

Production and cryopreservation of definitive endoderm from human pluripotent stem cells under defined and scalable culture conditions

The endodermal germ layer gives rise to respiratory epithelium, hepatocytes, pancreatic cells and intestinal lineages, among other cell types. These lineages can be differentiated from human pluripotent stem cells (hPSCs) via a common definitive endoderm (DE) intermediate that is characterized by the co-expression of the cell surface markers CXCR4, c-KIT and EPCAM and the transcription factors SOX17 and FOXA2. Here we provide a detailed protocol for mass production of DE from hPSCs in scalable and easy-to-handle suspension culture using a rotating Erlenmeyer flask or a sophisticated, fully controllable, 150-ml stirred tank bioreactor. This protocol uses two different media formulations that are chemically defined and xeno free and therefore good manufacturing practice ready. Our protocol allows for efficient hPSC-derived DE specification in multicellular aggregates within 3 days and generates up to 1 × 10⁸ DE cells with >92% purity in one differentiation batch when using the bioreactor. The hPSC-derived DE cells that are generated can be cryopreserved for later downstream differentiation into various endodermal lineages. This protocol should facilitate the flexible production of mature DE derivatives for physiologically relevant disease models, high-throughput drug screening, toxicology testing and cellular therapies.

Overcoming bioprocess bottlenecks in the large-scale expansion of high-quality hiPSC aggregates in vertical-wheel stirred suspension bioreactors

BACKGROUND

Human induced pluripotent stem cells (hiPSCs) hold enormous promise in accelerating breakthroughs in understanding human development, drug screening, disease modeling, and cell and gene therapies. Their potential, however, has been bottlenecked in a mostly laboratory setting due to bioprocess challenges in the scale-up of large quantities of high-quality cells for clinical and manufacturing purposes. While several studies have investigated the production of hiPSCs in bioreactors, the use of conventional horizontal-impeller, paddle, and rocking-wave mixing mechanisms have demonstrated unfavorable hydrodynamic environments for hiPSC growth and quality maintenance. This study focused on using computational fluid dynamics (CFD) modeling to aid in characterizing and optimizing the use of vertical-wheel bioreactors for hiPSC production.

METHODS

The vertical-wheel bioreactor was modeled with CFD simulation software Fluent at agitation rates between 20 and 100 rpm. These models produced fluid flow patterns that mapped out a hydrodynamic environment to guide in the development of hiPSC inoculation and in-vessel aggregate dissociation protocols. The effect of single-cell inoculation on aggregate formation and growth was tested at select CFD-modeled agitation rates and feeding regimes in the vertical-wheel bioreactor. An in-vessel dissociation protocol was developed through the testing of various proteolytic enzymes and agitation exposure times.

RESULTS

CFD modeling demonstrated the unique flow pattern and homogeneous distribution of hydrodynamic forces produced in the vertical-wheel bioreactor, making it the opportune environment for systematic bioprocess optimization of hiPSC expansion. We developed a scalable, single-cell inoculation protocol for the culture of hiPSCs as aggregates in vertical-wheel bioreactors, achieving over 30-fold expansion in 6 days without sacrificing cell quality. We have also provided the first published protocol for in-vessel hiPSC aggregate dissociation, permitting the entire bioreactor volume to be harvested into single cells for serial passaging into larger scale reactors. Importantly, the cells harvested and re-inoculated into scaled-up vertical-wheel bioreactors not only maintained consistent growth kinetics, they maintained a normal karyotype and pluripotent characterization and function.

CONCLUSIONS

Taken together, these protocols provide a feasible solution for the culture of high-quality hiPSCs at a clinical and manufacturing scale by overcoming some of the major documented bioprocess bottlenecks.

Cell-Based Therapy Manufacturing in Stirred Suspension Bioreactor: Thoughts for cGMP Compliance

Cell-based therapy (CBT) is attracting much attention to treat incurable diseases. In recent years, several clinical trials have been conducted using human pluripotent stem cells (hPSCs), and other potential therapeutic cells. Various private- and government-funded organizations are investing in finding permanent cures for diseases that are difficult or expensive to treat over a lifespan, such as age-related macular degeneration, Parkinson’s disease, or diabetes, etc. Clinical-grade cell manufacturing requiring current good manufacturing practices (cGMP) has therefore become an important issue to make safe and effective CBT products. Current cell production practices are adopted from conventional antibody or protein production in the pharmaceutical industry, wherein cells are used as a vector to produce the desired products. With CBT, however, the “cells are the final products” and sensitive to physico- chemical parameters and storage conditions anywhere between isolation and patient administration. In addition, the manufacturing of cellular products involves multi-stage processing, including cell isolation, genetic modification, PSC derivation, expansion, differentiation, purification, characterization, cryopreservation, etc. Posing a high risk of product contamination, these can be time- and cost- prohibitive due to maintenance of cGMP. The growing demand of CBT needs integrated manufacturing systems that can provide a more simple and cost-effective platform. Here, we discuss the current methods and limitations of CBT, based upon experience with biologics production. We review current cell manufacturing integration, automation and provide an overview of some important considerations and best cGMP practices. Finally, we propose how multi-stage cell processing can be integrated into a single bioreactor, in order to develop streamlined cGMP-compliant cell processing systems.

A Marine Collagen-Based Biomimetic Hydrogel Recapitulates Cancer Stem Cell Niche and Enhances Progression and Chemoresistance in Human Ovarian Cancer

Recent attention has focused on the development of an effective three-dimensional (3D) cell culture system enabling the rapid enrichment of cancer stem cells (CSCs) that are resistant to therapies and serving as a useful in vitro tumor model that accurately reflects in vivo behaviors of cancer cells. Presently, an effective 3D in vitro model of ovarian cancer (OC) was developed using a marine collagen-based hydrogel. Advantages of the model include simplicity, efficiency, bioactivity, and low cost. Remarkably, OC cells grown in this hydrogel exhibited biochemical and physiological features, including (1) enhanced cell proliferation, migration and invasion, colony formation, and chemoresistance; (2) suppressed apoptosis with altered expression levels of apoptosis-regulating molecules; (3) upregulated expression of crucial multidrug resistance-related genes; (4) accentuated expression of key molecules associated with malignant progression, such as epithelial–mesenchymal transition transcription factors, Notch, and pluripotency biomarkers; and (5) robust enrichment of ovarian CSCs. The findings indicate the potential of our 3D in vitro OC model as an in vitro research platform to study OC and ovarian CSC biology and to screen novel therapies targeting OC and ovarian CSCs.

Human iPSC-Based Models for the Development of Therapeutics Targeting Neurodegenerative Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a group of rare genetic conditions. The absence or deficiency of lysosomal proteins leads to excessive storage of undigested materials and drives secondary pathological mechanisms including autophagy, calcium homeostasis, ER stress, and mitochondrial abnormalities. A large number of LSDs display mild to severe central nervous system (CNS) involvement. Animal disease models and post-mortem tissues partially recapitulate the disease or represent the final stage of CNS pathology, respectively. In the last decades, human models based on induced pluripotent stem cells (hiPSCs) have been extensively applied to investigate LSD pathology in several tissues and organs, including the CNS. Neural stem/progenitor cells (NSCs) derived from patient-specific hiPSCs (hiPS-NSCs) are a promising tool to define the effects of the pathological storage on neurodevelopment, survival and function of neurons and glial cells in neurodegenerative LSDs. Additionally, the development of novel 2D co-culture systems and 3D hiPSC-based models is fostering the investigation of neuron-glia functional and dysfunctional interactions, also contributing to define the role of neurodevelopment and neuroinflammation in the onset and progression of the disease, with important implications in terms of timing and efficacy of treatments. Here, we discuss the advantages and limits of the application of hiPS-NSC-based models in the study and treatment of CNS pathology in different LSDs. Additionally, we review the state-of-the-art and the prospective applications of NSC-based therapy, highlighting the potential exploitation of hiPS-NSCs for gene and cell therapy approaches in the treatment of neurodegenerative LSDs.

Stirred suspension bioreactors maintain naïve pluripotency of human pluripotent stem cells

Due to their ability to standardize key physiological parameters, stirred suspension bioreactors can potentially scale the production of quality-controlled pluripotent stem cells (PSCs) for cell therapy application. Because of differences in bioreactor expansion efficiency between mouse (m) and human (h) PSCs, we investigated if conversion of hPSCs, from the conventional "primed" pluripotent state towards the "naïve" state prevalent in mPSCs, could be used to enhance hPSC production. Through transcriptomic enrichment of mechano-sensing signaling, the expression of epigenetic regulators, metabolomics, and cell-surface protein marker analyses, we show that the stirred suspension bioreactor environment helps maintain a naïve-like pluripotent state. Our research corroborates that converting hPSCs towards a naïve state enhances hPSC manufacturing and indicates a potentially important role for the stirred suspension bioreactor's mechanical environment in maintaining naïve-like pluripotency.

Magnetic heating of nanoparticles as a scalable cryopreservation technology for human induced pluripotent stem cells

Scale-up of production is needed for industrial applications and clinical translation of human induced pluripotent stem cells (hiPSCs). However, in cryopreservation of hiPSCs, successful rewarming of vitrified cells can only be achieved by convective warming of small volumes (generally 0.2 mL). Here, we present a scalable nano-warming technology for hiPSC cryopreservation employing inductive heating of magnetic nanoparticles under an alternating magnetic field. The conventional method by water bath heating at 37 °C resulted in a decrease of cell viability owing to devitrification caused by slow warming of samples with large volumes (≥ 20 mL). Nano-warming showed uniform and rapid rewarming of vitrified samples and improved viability of hiPSCs in the 20-mL system. In addition to single cells, hiPSC aggregates prepared using a bioreactor-based approach were successfully cryopreserved by the nano-warming technique. These results demonstrate that nano-warming is a promising methodology for cryopreservation in mass production of hiPSCs.

Indirect Immunofluorescence and Tumorspheres Enrichment Technique for Identifying Cancer Stem Cell Markers in Cancer Cell Lines From Primary Oral Cancer Tissues: An In Vitro Study

Aim:

The cancer stem cells (CSCs) are known to be responsible for drug resistance and cancer relapse in the treatment of cancer. Identification and isolation of CSCs and study of their properties will play a crucial role in developing an effective drug against these targets. The aim of the study was to isolate CSCs from primary cancer by the tumorspheres enrichment method, to confirm by indirect immunofluorescence and gene expression of stem cell markers by using real-time polymerase chain reaction (RT-PCR) technique.

Materials and Methods:

In this in vitro study, we enriched oral CSCs through tumorsphere formation assay from seven primary cultures of OSCC patients with defined serum media. The expression and localization of the cell surface markers of CD133 and CD44 were tested by indirect immunofluorescence. Gene expression of stem cell markers such as CD44, CD133, Oct4, Sox2, and Nanog were quantified by RT-PCR technique. One-way analysis of variance was applied to analyze gene expression.

Results:

Tumorsphere formation has been used to isolate the CSCs from the OSCC tissue culture. Both CD133 and CD44 antibody confirmed the presence of CSCs through indirect immunofluorescence. In comparison to parental cell lines, the expression levels of CD133, CD44, Oct4, Sox2, and Nanog stem cell were significantly higher in CSC-enriched subpopulations.

Conclusions:

The cost-effective spheroid enrichment and the indirect immunofluorescence methods are useful for the isolation of CSCs from the primary tumor.

Modeling Cardiac Disease Mechanisms Using Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Progress, Promises and Challenges

Cardiovascular diseases (CVDs) are a class of disorders affecting the heart or blood vessels. Despite progress in clinical research and therapy, CVDs still represent the leading cause of mortality and morbidity worldwide. The hallmarks of cardiac diseases include heart dysfunction and cardiomyocyte death, inflammation, fibrosis, scar tissue, hyperplasia, hypertrophy, and abnormal ventricular remodeling. The loss of cardiomyocytes is an irreversible process that leads to fibrosis and scar formation, which, in turn, induce heart failure with progressive and dramatic consequences. Both genetic and environmental factors pathologically contribute to the development of CVDs, but the precise causes that trigger cardiac diseases and their progression are still largely unknown. The lack of reliable human model systems for such diseases has hampered the unraveling of the underlying molecular mechanisms and cellular processes involved in heart diseases at their initial stage and during their progression. Over the past decade, significant scientific advances in the field of stem cell biology have literally revolutionized the study of human disease in vitro. Remarkably, the possibility to generate disease-relevant cell types from induced pluripotent stem cells (iPSCs) has developed into an unprecedented and powerful opportunity to achieve the long-standing ambition to investigate human diseases at a cellular level, uncovering their molecular mechanisms, and finally to translate bench discoveries into potential new therapeutic strategies. This review provides an update on previous and current research in the field of iPSC-driven cardiovascular disease modeling, with the aim of underlining the potential of stem-cell biology-based approaches in the elucidation of the pathophysiology of these life-threatening diseases.

Three dimensional microcarrier system in mesenchymal stem cell culture: a systematic review

Stem cell-based regenerative medicine is a promising approach for tissue reconstruction. However, a large number of cells are needed in a typical clinical study, where conventional monolayer cultures might pose a limitation for scale-up. The purpose of this review was to systematically assess the application of microcarriers in Mesenchymal Stem Cell cultures. A comprehensive search was conducted in Medline via Ebscohost, Pubmed, and Scopus, and relevant studies published between 2015 and 2019 were selected. The literature search identified 53 related studies, but only 14 articles met the inclusion criteria. These include 7 utilised commercially available microcarriers, while the rest were formulated based on different surface characteristics, all of which are discussed in this review. Current applications of microcarriers were focused on MSC expansion and induction of MSCs into different lineages. These studies demonstrated that MSCs could proliferate in a microcarrier culture system in-fold compared to monolayer cultures, and the culture system could simulate a three-dimensional environment which induces cell differentiation. However, detailed studies are still required before this system were to be adapted into the scale of GMP manufacturing.

Optimized serial expansion of human induced pluripotent stem cells using low-density inoculation to generate clinically relevant quantities in vertical-wheel bioreactors

Human induced pluripotent stem cells (hiPSCs) have generated a great deal of attention owing to their capacity for self‐renewal and differentiation into the three germ layers of the body. Their discovery has facilitated a new era in biomedicine for understanding human development, drug screening, disease modeling, and cell therapy while reducing ethical issues and risks of immune rejection associated with traditional embryonic stem cells. Bioreactor‐based processes have been the method of choice for the efficient expansion and differentiation of stem cells in controlled environments. Current protocols for the expansion of hiPSCs use horizontal impeller, paddle, or rocking wave mixing method bioreactors which require large static cell culture starting populations and achieve only moderate cell fold increases. This study focused on optimizing inoculation, agitation, oxygen, and nutrient availability for the culture of hiPSCs as aggregates in single‐use, low‐shear, vertical‐wheel bioreactors. Under optimized conditions, we achieved an expansion of more than 30‐fold in 6 days using a small starting population of cells and minimal media resources throughout. Importantly, we showed that that this optimized bioreactor expansion protocol could be replicated over four serial passages resulting in a cumulative cell expansion of 1.06E6‐fold in 28 days. Cells from the final day of the serial passage were of high quality, maintaining a normal karyotype, pluripotent marker staining, and the ability to form teratomas in vivo. These findings demonstrate that a vertical‐wheel bioreactor‐based bioprocess can provide optimal conditions for efficient, rapid generation of high‐quality hiPSCs to meet the demands for clinical manufacturing of therapeutic cell products.

Modulation of Wnt and Activin/Nodal supports efficient derivation, cloning and suspension expansion of human pluripotent stem cells

Various culture systems have been used to derive and maintain human pluripotent stem cells (hPSCs), but they are inefficient in sustaining cloning and suspension expansion of hPSCs. Through systematically modulating Wnt and Activin/Nodal signaling, we developed a defined medium (termed AIC), which enables efficient cloning and long-term expansion of hPSCs (AIC-hPSCs) through single-cell passage on feeders, matrix or in suspension (25-fold expansion in 4 days) and maintains genomic stability of hPSCs over extensive expansion. Moreover, the AIC medium supports efficient derivation of hPSCs from blastocysts or somatic cells under feeder-free conditions. Compared to conventional hPSCs, AIC-hPSCs have similar gene expression profiles but down-regulated differentiation genes and display higher metabolic activity. Additionally, the AIC medium shows a good compatibility for different hPSC lines under various culture conditions. Our study provides a robust culture system for derivation, cloning and suspension expansion of high-quality hPSCs that benefits GMP production and processing of therapeutic hPSC products.

Bioprocess Technologies that Preserve the Quality of iPSCs

Large-scale production of induced pluripotent stem cells (iPSCs) is essential for the treatment of a variety of clinical indications. However, culturing enough iPSCs for clinical applications is problematic due to their sensitive pluripotent state and dependence on a supporting matrix. Developing stem cell bioprocessing strategies that are scalable and meet clinical needs requires incorporating methods that measure and monitor intrinsic markers of cell differentiation state, developmental status, and viability in real time. In addition, proper cell culture modalities that nurture the growth of high-quality stem cells in suspension are critical for industrial scale-up. In this review, we present an overview of cell culture media, suspension modalities, and monitoring techniques that preserve the quality and pluripotency of iPSCs during initiation, expansion, and manufacturing.

The effect of dual inhibition of Ras-MEK-ERK and GSK3β pathways on development of in vitro cultured rabbit embryos

Dual inhibition (2i) of Ras-MEK-ERK and GSK3β pathways enables the derivation of embryo stem cells (ESCs) from refractory mouse strains and, for permissive strains, allows ESC derivation with no external protein factor stimuli involvement. In addition, blocking of ERK signalling in 8-cell-stage mouse embryos leads to ablation of GATA4/6 expression in hypoblasts, suggesting fibroblast growth factor (FGF) dependence of hypoblast formation in the mouse. In human, bovine or porcine embryos, the hypoblast remains unaffected or displays slight-to-moderate reduction in cell number. In this study, we demonstrated that segregation of the hypoblast and the epiblast in rabbit embryos is FGF independent and 2i treatment elicits only a limited reinforcement in favour of OCT4-positive epiblast populations against the GATA4-/6-positive hypoblast population. It has been previously shown that TGFβ/Activin A inhibition overcomes the pervasive differentiation and inhomogeneity of rat iPSCs, rat ESCs and human iPSCs while prompting them to acquire naïve properties. However, TGFβ/Activin A inhibition, alone or together with Rho-associated, coiled-coil containing protein kinase (ROCK) inhibition, was not compatible with the viability of rabbit embryos according to the ultrastructural analysis of preimplantation rabbit embryos by electron microscopy. In rabbit models ovulation upon mating allows the precise timing of progression of the pregnancy. It produces several embryos of the desired stage in one pregnancy and a relatively short gestation period, making the rabbit embryo a suitable model to discover the cellular functions and mechanisms of maintenance of pluripotency in embryonic cells and the embryo-derived stem cells of other mammals.

Recent progress in induced pluripotent stem cell-derived cardiac cell sheets for tissue engineering

The past decade has witnessed remarkable development in tissue engineering technologies and stem cells. Our lab has developed a novel technology - "cell sheet technology" for tissue engineering. After the confluent cells are cultured on an innovative temperature-responsive culture dish, the cells can be harvested as an intact sheet by lowering temperature. We have successfully created multiple cell sheet-based tissues for therapies of a vast variety of diseases, in particular, myocardial diseases. On the other side, the discovery of human induced pluripotent stem cells (hiPSC) enables stable production of defined tissue-specific cell types and thus makes it possible to regenerate tissues or even organs for clinical application and in vitro drug screening/disease modeling. Recently, we have combined cell sheet technology and hiPSC-derived cardiac cells for fabrication of functional human cardiac tissues. This review summarizes ongoing challenges in this field and our progresses in solving issues, such as large scale culture of hiPSC-derived cardiac cells, elimination of undifferentiated iPSCs to decrease the risk of tumor formation as well as myocardial tissue fabrication technologies.

Bioengineering Considerations for a Nurturing Way to Enhance Scalable Expansion of Human Pluripotent Stem Cells

Understanding how defects in mechanotransduction affect cell-to-cell variability will add to the fundamental knowledge of human pluripotent stem cell (hPSC) culture, and may suggest new approaches for achieving a robust, reproducible, and scalable process that result in consistent product quality and yields. Here, the current state of the understanding of the fundamental mechanisms that govern the growth kinetics of hPSCs between static and dynamic cultures is reviewed, the factors causing fluctuations are identified, and culture strategies that might eliminate or minimize the occurrence of cell-to-cell variability arising from these fluctuations are discussed. The existing challenges in the development of hPSC expansion methods for enabling the transition from process development to large-scale production are addressed, a mandatory step for industrial and clinical applications of hPSCs.

Addressing Manufacturing Challenges for Commercialization of iPSC-Based Therapies

The development of reprogramming technology to generate human induced pluripotent stem cells (iPSCs) has tremendously influenced the field of regenerative medicine and clinical therapeutics where curative cell replacement therapies can be used in the treatment of devastating diseases such as Parkinson's disease (PD) and diabetes. In order to commercialize these therapies to treat a large number of individuals, it is important to demonstrate the safety and efficacy of these therapies and ensure that the manufacturing process for iPSC-derived functional cells can be industrialized at an affordable cost. However, there are a number of manufacturing obstacles that need to be addressed in order to meet this vision. It is important to note that the manufacturing process for generation of iPSC-derived specialized cells is relatively long and fairly complex and requires differentiation of high-quality iPSCs into specialized cells in a controlled manner. In this chapter, we have summarized our efforts to address the main challenges present in the industrialization of iPSC-derived cell therapy products with focus on the development of a current Good Manufacturing Practice (cGMP)-compliant iPSC manufacturing process, a comprehensive iPSC characterization platform, long-term stability of cGMP compliant iPSCs, and innovative technologies to address some of the scale-up challenges in establishment of iPSC processing in 3D computer-controlled bioreactors.

Adequate taylor couette flow-mediated shear stress is useful for dissociating human iPS cell-derived cell aggregates

Pluripotent stem cell including induced pluripotent stem cells (iPSC) are promising cell sources for regenerative medicine and for three-dimensional suspension culture technologies which may enable the generation of robust numbers of desired cells through cell aggregation. Although manual procedure is widely used for dissociating cell aggregates, the development of non-manual procedures using devices will contribute to efficient cell manufacturing. In the present study, we developed novel cell aggregate dissociation devices with a rotating cylinder inside based on taylor couette flow-mediated shear stress. The shear stress can be increased according to an increase in the size of the rotating cylinder inside the devices and the rotation rate. Adequate device size and suitable rotation rate efficiently dissociated cell aggregates after the undifferentiated expansion and the cardiac differentiation of human iPSC. These finding suggest that non-manual device procedure might be useful for harvesting single cells from human iPSC-derived cell aggregates.

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The newly device successfully generates taylor couette flow.

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Shear stress levels according to the different types of device and rotation rates are quantified through the flow analysis.

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Taylor couette flow-mediated adequate shear stress dissociate cell aggregates from human iPS cells.

Kinetics on aggregate behaviors of human induced pluripotent stem cells in static suspension and rotating flow cultures

Understanding of kinetics on aggregate behaviors of human induced pluripotent stem cells (hiPSCs) is critical knowledge for culture design because aggregate behaviors are considered to affect cell growth. In this study, we elucidated kinetics on aggregate behaviors of two types of hiPSCs (253G1 and 201B7 lines) to clarify the influence of aggregate behaviors on cell growth by comparing aggregate morphology, size of cell aggregates, and kinetic parameters in 72 h culture under static and floating conditions, which were realized by multi-dimple plate and rotating wall vessel, respectively. In the case of 253G1 line under floating condition, aggregate number decreased and size increased drastically during culture time, t = 0-24 h due to coalescence between cell aggregates. The apparent specific growth rate decreased after t = 24 h although cell number and aggregate size gradually increased under static condition. In the case of 201B7 line under floating condition, cell and aggregate number, and aggregate size kept constant levels during t = 24-72 h due to collapse of cell aggregates by stripping of single cells from aggregate, suggesting that specific death rate increased after t = 24 h despite constant levels of apparent specific growth rate and aggregate number under static condition. Our kinetic analysis concluded that excessive increase of aggregate size due to coalescence and cell death due to collapse critically affected growth of hiPSCs in suspension culture.

Chemically-Defined, Xeno-Free, Scalable Production of hPSC-Derived Definitive Endoderm Aggregates with Multi-Lineage Differentiation Potential

For the production and bio-banking of differentiated derivatives from human pluripotent stem cells (hPSCs) in large quantities for drug screening and cellular therapies, well-defined and robust procedures for differentiation and cryopreservation are required. Definitive endoderm (DE) gives rise to respiratory and digestive epithelium, as well as thyroid, thymus, liver, and pancreas. Here, we present a scalable, universal process for the generation of DE from human-induced pluripotent stem cells (hiPSCs) and embryonic stem cells (hESCs). Optimal control during the differentiation process was attained in chemically-defined and xeno-free suspension culture, and high flexibility of the workflow was achieved by the introduction of an efficient cryopreservation step at the end of DE differentiation. DE aggregates were capable of differentiating into hepatic-like, pancreatic, intestinal, and lung progenitor cells. Scale-up of the differentiation process using stirred-tank bioreactors enabled production of large quantities of DE aggregates. This process provides a useful advance for versatile applications of DE lineages, in particular for cell therapies and drug screening.

Computational fluid dynamics modeling, a novel, and effective approach for developing scalable cell therapy manufacturing processes

Induced pluripotent stem cells (iPSCs) hold great potential to generate novel, curative cell therapy products. However, current methods to generate these novel therapies lack scalability, are labor-intensive, require a large footprint, and are not suited to meet clinical and commercial demands. Therefore, it is necessary to develop scalable manufacturing processes to accommodate the generation of high-quality iPSC derivatives under controlled conditions. The current scale-up methods used in cell therapy processes are based on empirical, geometry-dependent methods that do not accurately represent the hydrodynamics of 3D bioreactors. These methods require multiple iterations of scale-up studies, resulting in increased development cost and time. Here we show a novel approach using computational fluid dynamics modeling to effectively scale-up cell therapy manufacturing processes in 3D bioreactors. Using a GMP-compatible iPSC line, we translated and scaled-up a small-scale cardiomyocyte differentiation process to a 3-L computer-controlled bioreactor in an efficient manner, showing comparability in both systems.

Modeling methodology for defining a priori the hydrodynamics of a dynamic suspension bioreactor. Application to human induced pluripotent stem cell culture

Three-dimensional dynamic suspension is becoming an effective cell culture method for a wide range of bioprocesses, with an increasing number of bioreactors proposed for this purpose. The complex hydrodynamics establishing within these devices affects bioprocess outcomes and efficiency, and usually expensive in vitro trial-and-error experiments are needed to properly set the working parameters. Here we propose a methodology to define a priori the hydrodynamic working parameters of a dynamic suspension bioreactor, selected as a test case because of the complex hydrodynamics characterizing its operating condition. A combination of computational and analytical approaches was applied to generate operational guideline graphs for defining a priori specific working parameters. In detail, 43 simulations were performed under pulsed flow regime to characterize advective transport within the device depending on different operative conditions, i.e., culture medium flow rate and its duty cycle, cultured particle diameter, and initial particle suspension volume. The operational guideline graphs were then used to set specific hydrodynamic working parameters for an in vitro proof-of-principle test, where human induced pluripotent stem cell (hiPSC) aggregates were cultured for 24 h within the bioreactor. The in vitro findings showed that, under the selected pulsed flow regime, sedimentation was avoided, hiPSC aggregate circularity and viability were preserved, and culture heterogeneity was reduced, thus confirming the appropriateness of the a priori method. This methodology has the potential to be adaptable to other dynamic suspension devices to support experimental studies by providing in silico-based a priori knowledge, useful to limit costs and to optimize culture bioprocesses.

Stirred Suspension Bioreactor Culture of Porcine Induced Pluripotent Stem Cells

Induced pluripotent stem cells (iPSCs) are an attractive cell source for regenerative medicine and the development of therapies, as they can proliferate indefinitely under defined conditions and differentiate into any cell type in the body. Large-scale expansion of cells is limited in adherent culture, making it difficult to obtain adequate cell numbers for research. It has been previously shown that stirred suspension bioreactors (SSBs) can be used to culture mouse and human stem cells. Pigs are important preclinical models for stem cell research. Therefore, this study investigated the use of SSBs as an alternative culture method for the expansion of iPSCs. Using an established porcine iPSC (piPSC) line as well as a new cell line derived and characterized in the current study, we report that piPSCs can grow in SSB while maintaining characteristics of pluripotency and karyotypic stability similar to cells grown in traditional two-dimensional static culture. This culture method provides a suitable platform for scale-up of cell culture to provide adequate cell numbers for future research applications involving piPSCs.

Using computational fluid dynamics (CFD) modeling to understand murine embryonic stem cell aggregate size and pluripotency distributions in stirred suspension bioreactors

Computational fluid dynamics (CFD) modeling can be applied to understand hydrodynamics in stirred suspension bioreactors, which can in turn affect cell viability, proliferation, pluripotency and differentiation. In this study, we developed a CFD model to determine the effects of average shear rates and turbulent eddies on the formation and growth of murine embryonic stem cell aggregates. We found a correlation between average eddy size and aggregate size, which depended on bioreactor agitation rates. By relating these computational and biological variables, CFD modeling can predict optimal agitation rates to grow embryonic stem cell aggregates in stirred suspension bioreactors. To examine the effect of hydrodynamics on pluripotency, mESCs cultured in bioreactors under various agitation rates were tested for SSEA-1, Sox-2, and Nanog expression. Cells maintained a minimum of 95% positive expression with no change in the intensity distribution pattern between the different bioreactor conditions. This indicates that the average level of pluripotency marker expression is independent of changes in the hydrodynamic profile and resulting aggregate size distribution. The findings here can be further extended to other cell types that grow as aggregates in stirred suspension bioreactors and offer important insights necessary to realize cell therapies.

"Necessity Is the Mother of Invention" or Inexpensive, Reliable, and Reproducible Protocol for Generating Organoids

Organoids are three-dimensional (3D) cell cultures that replicate some of the key features of morphology, spatial architecture, and functions of a particular organ. Organoids can be generated from both adult and pluripotent stem cells (PSCs), and complex organoids can also be obtained by combining different types of cells, including differentiated cells. The ability of pluripotent cells to self-organize into organotypic structures containing several cell subtypes specific for a particular organ was used for creating organoids of the brain, eye, kidney, intestine, and other organs. Despite the advantages of using PSCs for obtaining organoids, an essential shortcoming that prevents their widespread use has been a low yield when they are obtained from a PSC monolayer culture and a large variation in size. This leads to great heterogeneity on further differentiation. In this article, we describe our own protocol for generating standardized organoids, with emphasis on a method for generating brain organoids, which allows scaling-up experiments and makes their cultivation less expensive and easier.

3D bioprinting for high-throughput screening: Drug screening, disease modeling, and precision medicine applications

High-throughput technologies have become essential in many fields of pharmaceutical and biological development and production. Such technologies were initially developed with compatibility with liquid handling-based cell culture techniques to produce large-scale 2D cell culture experiments for the compound analysis of candidate drug compounds. Over the past two decades, tools for creating 3D cell cultures, organoids, and other 3D in vitro models, such as cell supportive biomaterials and 3D bioprinting, have rapidly advanced. Concurrently, a significant body of evidence has accumulated which speaks to the many benefits that 3D model systems have over traditional 2D cell cultures. Specifically, 3D cellular models better mimic aspects such as diffusion kinetics, cell-cell interactions, cell-matrix interactions, inclusion of stroma, and other features native to in vivo tissue and as such have become an integral part of academic research. However, most high throughput assays were not developed to specifically support 3D systems. Here, we describe the need for improved compatibility and relevant advances toward deployment and adoption of high throughput 3D models to improve disease modeling, drug efficacy testing, and precision medicine applications.