Unsupervised analysis of whole transcriptome data from human pluripotent stem cells cardiac differentiation

The main objective of the present work was to highlight differences and similarities in gene expression patterns between different pluripotent stem cell cardiac differentiation protocols, using a workflow based on unsupervised machine learning algorithms to analyse the transcriptome of cells cultured as a 2D monolayer or as 3D aggregates. This unsupervised approach effectively allowed to portray the transcriptomic changes that occurred throughout the differentiation processes, with a visual representation of the entire transcriptome. The results allowed to corroborate previously reported data and also to unveil new gene expression patterns. In particular, it was possible to identify a correlation between low cardiomyocyte differentiation efficiencies and the early expression of a set of non-mesodermal genes, which can be further explored as predictive markers of differentiation efficiency. The workflow here developed can also be applied to analyse other stem cell differentiation transcriptomic datasets, envisaging future clinical implementation of cellular therapies.

Bioprocess Economic Modeling: Decision Support Tools for the Development of Stem Cell Therapy Products

Over recent years, the field of cell and gene therapy has witnessed rapid growth due to the demonstrated benefits of using living cells as therapeutic agents in a broad range of clinical studies and trials. Bioprocess economic models (BEMs) are fundamental tools for guiding decision-making in bioprocess design, being capable of supporting process optimization and helping to reduce production costs. These tools are particularly important when it comes to guiding manufacturing decisions and increasing the likelihood of market acceptance of cell-based therapies, which are often cost-prohibitive because of high resource and quality control costs. Not only this, but the inherent biological variability of their underlying bioprocesses makes them particularly susceptible to unforeseen costs arising from failed or delayed production batches. The present work reviews important concepts concerning the development of bioprocesses for stem cell therapy products and highlights the valuable role which BEMs can play in this endeavor. Additionally, some theoretical concepts relevant to the building and structuring of BEMs are explored. Finally, a comprehensive review of the existent BEMs so far reported in the scientific literature for stem cell-related bioprocesses is provided to showcase their potential usefulness.

Characterization of the Aeration and Hydrodynamics in Vertical-Wheel™ Bioreactors

In this work, the oxygen transport and hydrodynamic flow of the PBS Vertical-Wheel MINI™ 0.1 bioreactor were characterized using experimental data and computational fluid dynamics simulations. Data acquired from spectroscopy-based oxygenation measurements was compared with data obtained from 3D simulations with a rigid-lid approximation and LES-WALE turbulence modeling, using the open-source software OpenFOAM-8. The mass transfer coefficients were determined for a range of stirring speeds between 10 and 100 rpm and for working volumes between 60 and 100 mL. Additionally, boundary condition, mesh refinement, and temperature variation studies were performed. Lastly, cell size, energy dissipation rate, and shear stress fields were calculated to determine optimal hydrodynamic conditions for culture. The experimental results demonstrate that the kL can be predicted using Sh=1.68Re0.551Sc13G1.18, with a mean absolute error of 2.08%. Using the simulations and a correction factor of 0.473, the expression can be correlated to provide equally valid results. To directly obtain them from simulations, a partial slip boundary condition can be tuned, ensuring better near-surface velocity profiles or, alternatively, by deeply refining the mesh. Temperature variation studies support the use of this correlation for temperatures up to 37 °C by using a Schmidt exponent of 1/3. Finally, the flow was characterized as transitional with diverse mixing mechanisms that ensure homogeneity and suspension quality, and the results obtained are in agreement with previous studies that employed RANS models. Overall, this work provides new data regarding oxygen mass transfer and hydrodynamics in the Vertical-Wheel bioreactor, as well as new insights for air-water mass transfer modeling in systems with low interface deformation, and a computational model that can be used for further studies.

Cell Culture Process Scale-Up Challenges for Commercial-Scale Manufacturing of Allogeneic Pluripotent Stem Cell Products

Allogeneic cell therapy products, such as therapeutic cells derived from pluripotent stem cells (PSCs), have amazing potential to treat a wide variety of diseases and vast numbers of patients globally. However, there are various challenges related to manufacturing PSCs in single-use bioreactors, particularly at larger volumetric scales. This manuscript addresses these challenges and presents potential solutions to alleviate the anticipated bottlenecks for commercial-scale manufacturing of high-quality therapeutic cells derived from PSCs.

Electrical stimulation of neural-differentiating iPSCs on novel coaxial electroconductive nanofibers

Neural tissue engineering strategies are paramount to create fully mature neurons, necessary for new therapeutic strategies for neurological diseases or the creation of reliable in vitro models. Scaffolds can provide physical support for these neurons and enable cues for enhancing neural cell differentiation, such as electrical current. Coaxial electrospinning fibers, designed to fulfill neural cell needs, bring together an electroconductive shell layer (PCL-PANI), able to mediate electrical stimulation of cells cultivated on fibers mesh surface, and a soft core layer (PGS), used to finetune fiber diameter (951 ± 465 nm) and mechanical properties (1.3 ± 0.2 MPa). Those dual functional coaxial fibers are electroconductive (0.063 ± 0.029 S cm-1, stable over 21 days) and biodegradable (72% weigh loss in 12 hours upon human lipase accelerated assay). For the first time, the long-term effects of electrical stimulation on induced neural progenitor cells were studied using such fibers. The results show increase in neural maturation (upregulation of MAP2, NEF-H and SYP), up-regulation of glutamatergic marker genes (VGLUT1 - 15-fold) and voltage-sensitive channels (SCN1α - 12-fold, CACNA1C - 32-fold), and a down-regulation of GABAergic marker (GAD67 - 0.09-fold), as detected by qRT-PCR. Therefore, this study suggest a shift from an inhibitory to an excitatory neural cell profile. This work shows that the PGS/PCL-PANI coaxial fibers here developed have potential applications in neural tissue engineering.

Suspension Culture of Human Induced Pluripotent Stem Cells in Single-Use Vertical-Wheel™ Bioreactors Using Aggregate and Microcarrier Culture Systems

Human induced pluripotent stem cells (hiPSCs) have the potential to be used in a variety of biomedical applications, including drug discovery and Regenerative Medicine. The success of these approaches is, however, limited by the difficulty of generating the large quantities of cells required in a reproducible and controlled system. Bioreactors, widely used for industrial manufacture of biological products, constitute a viable strategy for large-scale production of stem cell derivatives. In this chapter, we describe the expansion of hiPSCs using the Vertical-Wheel™ bioreactor, a novel bioreactor configuration specifically designed for the culture of shear-sensitive cells. We provide protocols for the expansion of hiPSCs in suspension, both as floating aggregates and using microcarriers for cell adhesion. These methods may be important for the establishment of a scalable culture of hiPSCs, allowing the manufacturing of industrial- or clinical-scale cell numbers.

Transcriptome profiling of human pluripotent stem cell-derived cerebellar organoids reveals faster commitment under dynamic conditions

Human-induced pluripotent stem cells (iPSCs) have great potential for disease modeling. However, generating iPSC-derived models to study brain diseases remains a challenge. In particular, the ability to recapitulate cerebellar development in vitro is still limited. We presented a reproducible and scalable production of cerebellar organoids by using the novel single-use Vertical-Wheel bioreactors, in which functional cerebellar neurons were obtained. Here, we evaluate the global gene expression profiles by RNA sequencing (RNA-seq) across cerebellar differentiation, demonstrating a faster cerebellar commitment in this novel dynamic differentiation protocol. Furthermore, transcriptomic profiles suggest a significant enrichment of extracellular matrix (ECM) in dynamic-derived cerebellar organoids, which can better mimic the neural microenvironment and support a consistent neuronal network. Thus, an efficient generation of organoids with cerebellar identity was achieved for the first time in a continuous process using a dynamic system without the need of organoids encapsulation in ECM-based hydrogels, allowing the possibility of large-scale production and application in high-throughput processes. The presence of factors that favors angiogenesis onset was also detected in dynamic conditions, which can enhance functional maturation of cerebellar organoids. We anticipate that large-scale production of cerebellar organoids may help developing models for drug screening, toxicological tests, and studying pathological pathways involved in cerebellar degeneration.

The effect of electrospun scaffolds on the glycosaminoglycan profile of differentiating neural stem cells

The use of electrospun scaffolds for neural tissue engineering applications allows a closer mimicry of the native tissue extracellular matrix (ECM), important for the transplantation of cells in vivo. Moreover, the role of the electrospun fiber mat topography on neural stem cell (NSC) differentiation remains to be completely understood. In this work REN-VM cells (NSC model) were differentiated on polycaprolactone (PCL) nanofibers, obtained by wet/wet electrospinning, and on flat glass lamellas. The obtained differentiation profile of NSCs was evaluated using immunofluorescence and qPCR analysis. Glycosaminoglycan (GAG) analysis was successfully emplyed to evaluate changes in the GAG profile of differentiating cells through the use of the highly sensitive liquid chromatography-tandem mass/mass spectrometry (LC-MS/MS) method. Our results show that both culture platforms allow the differentiation of REN-VM cells into neural cells (neurons and astrocytes) similarly. Moreover, LC-MS/MS analysis shows changes in the production of GAGs present both in cell cultures and conditioned media samples. In the media, hyaluronic acid (HA) was detected and correlated with cellular activity and the production of a more plastic extracellular matrix. The cell samples evidence changes in chondroitin sulfate (CS4S, CS6S, CS4S6S) and heparan sulfate (HS6S, HS0S), similar to those previously described in vivo studies and possibly associated with the creation of complex structures, such as perineural networks. The GAG profile of differentiating REN-VM cells on electrospun scaffolds was analyzed for the first time. Our results highlight the advantage of using platforms obtain more reliable and robust neural tissue-engineered transplants.

Effect of Electrical Stimulation Conditions on Neural Stem Cells Differentiation on Cross-Linked PEDOT:PSS Films

The ability to culture and differentiate neural stem cells (NSCs) to generate functional neural populations is attracting increasing attention due to its potential to enable cell-therapies to treat neurodegenerative diseases. Recent studies have shown that electrical stimulation improves neuronal differentiation of stem cells populations, highlighting the importance of the development of electroconductive biocompatible materials for NSC culture and differentiation for tissue engineering and regenerative medicine. Here, we report the use of the conjugated polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS CLEVIOS P AI 4083) for the manufacture of conductive substrates. Two different protocols, using different cross-linkers (3-glycidyloxypropyl)trimethoxysilane (GOPS) and divinyl sulfone (DVS) were tested to enhance their stability in aqueous environments. Both cross-linking treatments influence PEDOT:PSS properties, namely conductivity and contact angle. However, only GOPS-cross-linked films demonstrated to maintain conductivity and thickness during their incubation in water for 15 days. GOPS-cross-linked films were used to culture ReNcell-VM under different electrical stimulation conditions (AC, DC, and pulsed DC electrical fields). The polymeric substrate exhibits adequate physicochemical properties to promote cell adhesion and growth, as assessed by Alamar Blue® assay, both with and without the application of electric fields. NSCs differentiation was studied by immunofluorescence and quantitative real-time polymerase chain reaction. This study demonstrates that the pulsed DC stimulation (1 V/cm for 12 days), is the most efficient at enhancing the differentiation of NSCs into neurons.

Polyaniline-polycaprolactone fibers for neural applications: Electroconductivity enhanced by pseudo-doping

Replenishing neurons in patients with neurodegenerative diseases is one of the ultimate therapies for these progressive, debilitating and fatal diseases. Electrical stimulation can improve neuron stem cell differentiation but requires a reliable nanopatterned electroconductive substrate. Potential candidate substrates are polycaprolactone (PCL) - polyaniline:camphorsulfonic acid (PANI:CSA) nanofibers, but their nanobiophysical properties need to be finetuned. The present study investigates the use of the pseudo-doping effect on the optimization of the electroconductivity of these polyaniline-based electrospun nanofibers. This was performed by developing a new solvent system that comprises a mixture of hexafluoropropanol (HFP) and trifluoroethanol (TFE). For the first time, an electroconductivity so high as 0.2 S cm^-1 was obtained for, obtained from a TFE:HFP 50/50 vol% solution, while maintaining fiber biocompatibility. The physicochemical mechanisms behind these changes were studied. The results suggest HFP promotes changes on PANI chains conformations through pseudo-doping, leading to the observed enhancement in electroconductivity. The consequences of such change in the nanofabrication of PCL-PANI fibers include an increase in fiber diameter (373 ± 172 nm), a decrease in contact angle (42 ± 3°) and a decrease in Young modulus (1.6 ± 0.5 MPa), making these fibers interesting candidates for neural tissue engineering. Electrical stimulation of differentiating neural stem cells was performed using AC electrical current. Positive effects on cell alignment and gene expression (DCX, MAP2) are observed. The novel optimized platform shows promising applications for (1) building in vitro platforms for drug screening, (2) interfaces for deep-brain electrodes; and (3) fully grown and functional neurons transplantation.

Scalable Production of Human Mesenchymal Stromal Cell-Derived Extracellular Vesicles Under Serum-/Xeno-Free Conditions in a Microcarrier-Based Bioreactor Culture System

Mesenchymal stromal cells (MSC) hold great promise for tissue engineering and cell-based therapies due to their multilineage differentiation potential and intrinsic immunomodulatory and trophic activities. Over the past years, increasing evidence has proposed extracellular vesicles (EVs) as mediators of many of the MSC-associated therapeutic features. EVs have emerged as mediators of intercellular communication, being associated with multiple physiological processes, but also in the pathogenesis of several diseases. EVs are derived from cell membranes, allowing high biocompatibility to target cells, while their small size makes them ideal candidates to cross biological barriers. Despite the promising potential of EVs for therapeutic applications, robust manufacturing processes that would increase the consistency and scalability of EV production are still lacking. In this work, EVs were produced by MSC isolated from different human tissue sources [bone marrow (BM), adipose tissue (AT), and umbilical cord matrix (UCM)]. A serum-/xeno-free microcarrier-based culture system was implemented in a Vertical-Wheel^TM bioreactor (VWBR), employing a human platelet lysate culture supplement (UltraGRO^TM-PURE), toward the scalable production of MSC-derived EVs (MSC-EVs). The morphology and structure of the manufactured EVs were assessed by atomic force microscopy, while EV protein markers were successfully identified in EVs by Western blot, and EV surface charge was maintained relatively constant (between −15.5 ± 1.6 mV and −19.4 ± 1.4 mV), as determined by zeta potential measurements. When compared to traditional culture systems under static conditions (T-flasks), the VWBR system allowed the production of EVs at higher concentration (i.e., EV concentration in the conditioned medium) (5.7-fold increase overall) and productivity (i.e., amount of EVs generated per cell) (3-fold increase overall). BM, AT and UCM MSC cultured in the VWBR system yielded an average of 2.8 ± 0.1 × 10¹¹, 3.1 ± 1.3 × 10¹¹, and 4.1 ± 1.7 × 10¹¹ EV particles (n = 3), respectively, in a 60 mL final volume. This bioreactor system also allowed to obtain a more robust MSC-EV production, regarding their purity, compared to static culture. Overall, we demonstrate that this scalable culture system can robustly manufacture EVs from MSC derived from different tissue sources, toward the development of novel therapeutic products.

Functionalization of Electrospun Nanofibers and Fiber Alignment Enhance Neural Stem Cell Proliferation and Neuronal Differentiation

Neural stem cells (NSCs) have the potential to generate the cells of the nervous system and, when cultured on nanofiber scaffolds, constitute a promising approach for neural tissue engineering. In this work, the impact of combining nanofiber alignment with functionalization of the electrospun poly-ε-caprolactone (PCL) nanofibers with biological adhesion motifs on the culture of an NSC line (CGR8-NS) is evaluated. A five-rank scale for fiber density was introduced, and a 4.5 level, corresponding to 70–80% fiber density, was selected for NSC in vitro culture. Aligned nanofibers directed NSC distribution and, especially in the presence of laminin (PCL-LN) and the RGD-containing peptide GRGDSP (PCL-RGD), promoted higher cell elongation, quantified by the eccentricity and axis ratio. In situ differentiation resulted in relatively higher percentage of cells expressing Tuj1 in PCL-LN, as well as significantly longer neurite development (41.1 ± 1.0 μm) than PCL-RGD (32.0 ± 1.0 μm), pristine PCL (25.1 ± 1.2 μm), or PCL-RGD randomly oriented fibers (26.5 ± 1.4 μm), suggesting that the presence of LN enhances neuronal differentiation. This study demonstrates that aligned nanofibers, functionalized with RGD, perform as well as PCL-LN fibers in terms of cell adhesion and proliferation. The presence of the full LN protein improves neuronal differentiation outcomes, which may be important for the use of this system in tissue engineering applications.

Scalable Generation of Mature Cerebellar Organoids from Human Pluripotent Stem Cells and Characterization by Immunostaining

The cerebellum plays a critical role in the maintenance of balance and motor coordination, and a functional defect in different cerebellar neurons can trigger cerebellar dysfunction. Most of the current knowledge about disease-related neuronal phenotypes is based on postmortem tissues, which makes understanding of disease progression and development difficult. Animal models and immortalized cell lines have also been used as models for neurodegenerative disorders. However, they do not fully recapitulate human disease. Human induced pluripotent stem cells (iPSCs) have great potential for disease modeling and provide a valuable source for regenerative approaches. In recent years, the generation of cerebral organoids from patient-derived iPSCs improved the prospects for neurodegenerative disease modeling. However, protocols that produce large numbers of organoids and a high yield of mature neurons in 3D culture systems are lacking. The protocol presented is a new approach for reproducible and scalable generation of human iPSC-derived organoids under chemically-defined conditions using scalable single-use bioreactors, in which organoids acquire cerebellar identity. The generated organoids are characterized by the expression of specific markers at both mRNA and protein level. The analysis of specific groups of proteins allows the detection of different cerebellar cell populations, whose localization is important for the evaluation of organoid structure. Organoid cryosectioning and further immunostaining of organoid slices are used to evaluate the presence of specific cerebellar cell populations and their spatial organization.

Challenges and Solutions for Commercial Scale Manufacturing of Allogeneic Pluripotent Stem Cell Products

Allogeneic cell therapy products, such as therapeutic cells derived from pluripotent stem cells (PSCs), have amazing potential to treat a wide variety of diseases and vast numbers of patients globally. However, there are various challenges related to the manufacturing of PSCs in large enough quantities to meet commercial needs. This manuscript addresses the challenges for the process development of PSCs production in a bioreactor, and also presents a scalable bioreactor technology that can be a possible solution to remove the bottleneck for the large-scale manufacturing of high-quality therapeutic cells derived from PSCs.

Maturation of Human Pluripotent Stem Cell-Derived Cerebellar Neurons in the Absence of Co-culture

The cerebellum plays a critical role in all vertebrates, and many neurological disorders are associated with cerebellum dysfunction. A major limitation in cerebellar research has been the lack of adequate disease models. As an alternative to animal models, cerebellar neurons differentiated from pluripotent stem cells have been used. However, previous studies only produced limited amounts of Purkinje cells. Moreover, in vitro generation of Purkinje cells required co-culture systems, which may introduce unknown components to the system. Here we describe a novel differentiation strategy that uses defined medium to generate Purkinje cells, granule cells, interneurons, and deep cerebellar nuclei projection neurons, that self-formed and differentiated into electrically active cells. Using a defined basal medium optimized for neuronal cell culture, we successfully promoted the differentiation of cerebellar precursors without the need for co-culturing. We anticipate that our findings may help developing better models for the study of cerebellar dysfunctions, while providing an advance toward the development of autologous replacement strategies for treating cerebellar degenerative diseases.

POLYBENZIMIDAZOLE NANOFIBERS FOR NEURAL STEM CELL CULTURE

Neurodegenerative diseases compromise the quality of life of increasing numbers of the world's aging population. While diagnosis is possible no effective treatments are available. Strong efforts are needed to develop new therapeutic approaches, namely in the areas of tissue engineering and deep brain stimulation (DBS). Conductive polymers are the ideal material for these applications due to the positive effect of conducting electricity on neural cell's differentiation profile. This novel study assessed the biocompatibility of polybenzimidazole (PBI), as electrospun fibers and after being doped with different acids. Firstly, doped films of PBI were used to characterize the materials' contact angle and electroconductivity. After this, fibers were electrospun and characterized by SEM, FTIR and TGA. Neural Stem Cell's (NSC) proliferation was assessed and their growth rate and morphology on different samples was determined. Differentiation of NSCs on PBI - CSA fibers was also investigated and gene expression (SOX2, NES, GFAP, Tuj1) was assessed through Immunochemistry and qPCR. All the samples tested were able to support neural stem cell (NSC) proliferation without significant changes on the cell's typical morphology. Successfully differentiation of NSCs towards neural cells on PBI - CSA fibers was also achieved. This promising PBI fibrous scaffold material is envisioned to be used in neural cell engineering applications, including scaffolds, in vitro models for drug screening and electrodes.

Strategies for the expansion of human induced pluripotent stem cells as aggregates in single-use Vertical-Wheel™ bioreactors

Background

Since their inception, human induced pluripotent stem cells (hiPSCs) have held much promise for pharmacological applications and cell-based therapies. However, their potential can only be realised if large numbers of cells can be produced reproducibly on-demand. While bioreactors are ideal systems for this task, due to providing agitation and control of the culture parameters, the common impeller geometries were not designed for the expansion of mammalian cells, potentially leading to sub-optimal results.

Results

This work reports for the first time the usage of the novel Vertical-Wheel single-use bioreactors for the expansion of hiPSCs as floating aggregates. Cultures were performed in the PBS MINI 0.1 bioreactor with 60 mL of working volume. Two different culture media were tested, mTeSR1 and mTeSR3D, in a repeated batch or fed-batch mode, respectively, as well as dextran sulfate (DS) supplementation. mTeSR3D was shown to sustain hiPSC expansion, although with lower maximum cell density than mTeSR1. Dextran sulfate supplementation led to an increase in 97 and 106% in maximum cell number when using mTeSR1 or mTeSR3D, respectively. For supplemented media, mTeSR1 + DS allowed for a higher cell density to be obtained with one less day of culture. A maximum cell density of (2.3 ± 0.2) × 10⁶ cells∙mL^− 1 and a volumetric productivity of (4.6 ± 0.3) × 10⁵ cells∙mL^− 1∙d^− 1 were obtained after 5 days with mTeSR1 + DS, resulting in aggregates with an average diameter of 346 ± 11 μm. The generated hiPSCs were analysed by flow cytometry and qRT-PCR and their differentiation potential was assayed, revealing the maintenance of their pluripotency after expansion.

Conclusions

The results here described present the Vertical-Wheel bioreactor as a promising technology for hiPSC bioprocessing. The specific characteristics of this bioreactor, namely in terms of the innovative agitation mechanism, can make it an important system in the development of hiPSC-derived products under current Good Manufacturing Practices.

Transcriptomic analysis of 3D Cardiac Differentiation of Human Induced Pluripotent Stem Cells Reveals Faster Cardiomyocyte Maturation Compared to 2D Culture

Human induced pluripotent stem cells (hiPSCs) represent an almost limitless source of cells for disease modelling and drug screening applications. Here we established an efficient and robust 3D platform for cardiomyocyte (CMs) production from hiPSCs, solely through small-molecule-based temporal modulation of the Wnt signalling, which generates more than 90% cTNT⁺ cells. The impact of performing the differentiation process in 3D conditions as compared to a 2D culture system, was characterized by transcriptomic analysis by using data collected from sequential stages of 2D and 3D culture. We highlight that performing an initial period of hiPSC aggregation before cardiac differentiation primed hiPSCs towards an earlier mesendoderm lineage differentiation, via TGF-β/Nodal signaling stabilization. Importantly, it was also found that CMs in the 3D microenvironment mature earlier and show an improved communication system, which we suggested to be responsible for a higher structural and functional maturation of 3D cardiac aggregates.

A value-added exopolysaccharide as a coating agent for MRI nanoprobes

Fucopol, a fucose-containing exopolysaccharide (EPS) produced by the bacterium Enterobacter A47 DSM 23139 using glycerol as a carbon source, was employed as a new coating material for iron oxide magnetic nanoparticles (MNPs). The coated particles were assessed as nanoprobes for cell labeling by Magnetic Resonance Imaging (MRI). The MNPs were synthesized by a thermal decomposition method and transferred to an aqueous medium by a ligand-exchange reaction with meso-2,3-dimercaptosuccinic acid (DMSA). Covalent binding of EPS to DMSA-stabilized nanoparticles (MNP-DMSA) resulted in a hybrid magnetic-biopolymeric nanosystem (MNP-DMSA-EPS) with a hydrodynamic size of 170 nm, a negative surface charge under physiological conditions and transverse to longitudinal relaxivity ratio, r2/r1, of 148. In vitro studies with two human cell lines (colorectal carcinoma - HCT116 - and neural stem/progenitor cells - ReNcell VM) showed that EPS promotes internalization of nanoparticles in both cell lines. In vitro MRI cell phantoms showed a superior performance of MNP-DMSA-EPS in ReNcell VM, for which the iron dose-dependent MRI signal drop was obtained at relatively low iron concentrations (12-20 μg Fe per ml) and short incubation times. Furthermore, ReNcell VM multipotency was not affected by culture in the presence of MNP-DMSA or MNP-DMSA-EPS for 14 days. Our study suggests that Fucopol-coated MNPs represent useful cell labeling nanoprobes for MRI.

Clinical-scale purification of pluripotent stem cell derivatives for cell-based therapies

Human pluripotent stem cells (hPSCs) have the potential to revolutionize cell-replacement therapies because of their ability to self renew and differentiate into nearly every cell type in the body. However, safety concerns have delayed the clinical translation of this technology. One cause for this is the capacity that hPSCs have to generate tumors after transplantation. Because of the challenges associated with achieving complete differentiation into clinically relevant cell types, the development of safe and efficient strategies for purifying committed cells is essential for advancing hPSC-based therapies. Several purification strategies have now succeeded in generating non-tumorigenic and homogeneous cell-populations. These techniques typically enrich for cells by either depleting early committed populations from teratoma-initiating hPSCs or by positively selecting cells after differentiation. Here we review the working principles behind separation methods that have facilitated the safe and controlled application of hPSC-derived cells in laboratory settings and pre-clinical research. We underscore the need for improving and integrating purification strategies within differentiation protocols in order to unlock the therapeutic potential of hPSCs.

Purification of human induced pluripotent stem cell-derived neural precursors using magnetic activated cell sorting

Neural precursor (NP) cells derived from human induced pluripotent stem cells (hiPSCs), and their neuronal progeny, will play an important role in disease modeling, drug screening tests, central nervous system development studies, and may even become valuable for regenerative medicine treatments. Nonetheless, it is challenging to obtain homogeneous and synchronously differentiated NP populations from hiPSCs, and after neural commitment many pluripotent stem cells remain in the differentiated cultures. Here, we describe an efficient and simple protocol to differentiate hiPSC-derived NPs in 12 days, and we include a final purification stage where Tra-1-60+ pluripotent stem cells (PSCs) are removed using magnetic activated cell sorting (MACS), leaving the NP population nearly free of PSCs.

Scalable expansion of human-induced pluripotent stem cells in xeno-free microcarriers

The expansion of human-induced pluripotent stem cells (hiPSCs) is commonly performed using feeder layers of mouse embryonic fibroblasts or in feeder-free conditions in two-dimensional culture platforms, which are associated with low production yields and lack of process control. Robust large-scale production of these cells under defined conditions has been one of the major challenges to fulfil the large cell number requirement for drug screening applications, toxicology assays, disease modeling and potential cellular therapies. Microcarrier-based systems, in particular, are a promising culture format since they provide a high surface-to-volume ratio and allow the scale-up of the process to stirred suspension bioreactors. In this context, this chapter describes a detailed methodology for the scalable expansion of hiPSCs in spinner flasks and using xeno-free microcarriers to allow further translation to Good Manufacturing Practice (GMP) conditions.

Microcarrier expansion of mouse embryonic stem cell-derived neural stem cells in stirred bioreactors

Neural stem cells (NSCs) are self-renewing multipotent cells, able to differentiate into the phenotypes present in the central nervous system. Applications of NSCs may include toxicology, fundamental research, or cell therapies. The culture of floating cell clusters, called "neurospheres," is widely used for the propagation of NSC populations in vitro but shows several limitations, which may be circumvented by expansion under adherent conditions. In particular, the derivation of distinct populations of NSCs from embryonic stem cells capable of long-term culture under adherent conditions without losing differentiation potential was recently described. However, the expansion of these cells in agitated bioreactors has not been addressed until now and was the aim of this study. Selected microcarriers were tested under dynamic conditions in spinner flasks. Superior performance was observed with polystyrene beads coated with a recombinant peptide containing the Arg-Gly-Asp (RGD) motif (Pronectin F). After optimization of the culture, a 35-fold increase in cell number was achieved after 6 days. High cellular viability and multipotency were maintained throughout the culture. The study presented here may be the basis for the development of larger scale bioprocesses for expansion of these and other populations of adherent NSCs, either from mouse or human origin.

Stem cell cultivation in bioreactors

Cell-based therapies have generated great interest in the scientific and medical communities, and stem cells in particular are very appealing for regenerative medicine, drug screening and other biomedical applications. These unspecialized cells have unlimited self-renewal capacity and the remarkable ability to produce mature cells with specialized functions, such as blood cells, nerve cells or cardiac muscle. However, the actual number of cells that can be obtained from available donors is very low. One possible solution for the generation of relevant numbers of cells for several applications is to scale-up the culture of these cells in vitro. This review describes recent developments in the cultivation of stem cells in bioreactors, particularly considerations regarding critical culture parameters, possible bioreactor configurations, and integration of novel technologies in the bioprocess development stage. We expect that this review will provide updated and detailed information focusing on the systematic production of stem cell products in compliance with regulatory guidelines, while using robust and cost-effective approaches.

Hypoxia enhances proliferation of mouse embryonic stem cell-derived neural stem cells

Neural stem (NS) cells can provide a source of material with potential applications for neural drug testing, developmental studies, or novel treatments for neurodegenerative diseases. Herein, the ex vivo expansion of a model system of mouse embryonic stem (mES) cell-derived NS cells was characterized and optimized, cells being cultivated under adherent conditions. Culture was first optimized in terms of initial cell plating density and oxygen concentration, known to strongly influence brain-derived NS cells. To this end, the growth of cells cultured under hypoxic (2%, 5%, and 10% O(2)) and normoxic (20% O(2)) conditions was compared. The results showed that 2-5% oxygen, without affecting multipotency, led to fold increase values in total cell number about twice higher than observed under 20% oxygen (20-fold vs. 10-fold, respectively) this effect being more pronounced when cells were plated at low density. With an optimal cell density of 10(4) cells/cm(2), the maximum growth rates were 1.9 day(-1) under hypoxia versus 1.7 day(-1) under normoxia. Cell division kinetics analysis by flow cytometry based on PKH67 tracking showed that when cultured in hypoxia, cells are at least one divisional generation ahead compared to normoxia. In terms of cell cycle, a larger population in a quiescent G(0) phase was observed in normoxic conditions. The optimization of NS cell culture performed here represents an important step toward the generation of a large number of neural cells from a reduced initial population, envisaging the potential application of these cells in multiple settings.