Pluripotent Stem Cell Aggregates Research Articles

Validation of a mouse 3D gastruloid-based embryotoxicity assay in reference to the ICH S5(R3) guideline chemical exposure list

There is growing interest in establishing alternative methods in place of conventional animal tests to assess the developmental and reproductive toxicity (DART) of chemicals. Gastruloids are 3D aggregates of pluripotent stem cells that spontaneously exhibit axial elongation morphogenesis similar to gastrulation. They have been explored as in vitro embryogenesis models for developmental and toxicological studies. Here, a mouse gastruloid-based assay was validated for DART assessment in accordance with the ICH S5(R3) guideline, which provides the plasma concentration data of various reference drugs in rodents, specifically Cmax and AUC for NOAEL and LOAEL. First, adverse effect concentrations of the reference drugs and their known metabolites on gastruloid development were determined based on morphological impact, namely reduced growth or aberrant elongation. Then, the NOAEL to LOAEL concentration range obtained from the gastruloid assay was compared with that in rodents to examine similarities in sensitivity between the in vitro and in vivo assays for each chemical. For 18 out of the 24 reference drugs that have both NOAEL and LOAEL information in rodents, the sensitivity of the gastruloid assay was comparable to the in vivo assay within an 8-fold concentration margin. For 7 out of the 8 additional reference drugs that have only NOAEL or LOAEL information in rodents, the gastruloid assay was in line with the in vivo data. Altogether, these results support the effectiveness of the gastruloid assay, which may be exploited as a non-animal alternative method for DART assessment.

O-156 Embryo-like models: Using 3D gastruloids to understand human development

Abstract The mammalian embryo develops through coordinated cell fate decisions that enable emerging spatiotemporal and morphogenetic complexity. While much insight into this process has been gained through studying model organisms, including mouse embryos, equivalent experiments are technically and ethically challenging in the human embryonic context. Instead, we use gastruloids: 3-dimensional aggregates of pluripotent stem cells that undergo multilineage differentiation to all three germ layers, polarise their gene expression and exhibit axial organisation that recapitulates many of the features of gastrulation and early organogenesis. By closely examining the dynamics and coordination of cell fate decisions and spatial gene expression organisation, we hope to better understand the regulatory logic behind early developmental events, particularly those that are human-specific. Likewise, by carefully manipulating the environment in which these gastruloids are grown, we can bias the structures towards particular lineages and morphological structures of interest. Doing so allows us to explore many of the principles of early development, and provides an opportunity to probe the mechanisms of biomedically-relevant conditions, such as congenital abnormalities.

Developmental toxicity of remdesivir, an anti-COVID-19 drug, is implicated by in vitro assays using morphogenetic embryoid bodies of mouse and human pluripotent stem cells.

Remdesivir is an antiviral drug approved for the treatment of COVID-19, whose developmental toxicity remains unclear. More information about the safety of remdesivir is urgently needed for people of childbearing potential, who are affected by the ongoing pandemic. Morphogenetic embryoid bodies (MEBs) are three-dimensional (3D) aggregates of pluripotent stem cells that recapitulate embryonic body patterning in vitro, and have been used as effective embryo models to detect the developmental toxicity of chemical exposures specifically and sensitively. MEBs were generated from mouse P19C5 and human H9 pluripotent stem cells, and used to examine the effects of remdesivir. The morphological effects were assessed by analyzing the morphometric parameters of MEBs after exposure to varying concentrations of remdesivir. The molecular impact of remdesivir was evaluated by measuring the transcript levels of developmental regulator genes. The mouse MEB morphogenesis was impaired by remdesivir at 1-8μM. Remdesivir affected MEBs in a manner dependent on metabolic conversion, and its potency was higher than GS-441524 and GS-621763, presumptive anti-COVID-19 drugs that act similarly to remdesivir. The expressions of developmental regulator genes, particularly those involved in axial and somite patterning, were dysregulated by remdesivir. The early stage of MEB development was more vulnerable to remdesivir exposure than the later stage. The morphogenesis and gene expression profiles of human MEBs were also impaired by remdesivir at 1-8μM. Remdesivir impaired mouse and human MEBs at concentrations that are comparable to the therapeutic plasma levels in humans, urging further investigation into the potential impact of remdesivir on developing embryos.

Rg3 and Rh2 ginsenosides suppress embryoid body formation by inhibiting the epithelial-mesenchymal transition

Numerous active compounds derived from ginseng exhibit various pharmacological and therapeutic effects in humans. Despite the benefits of ginsenosides, little is known about their influence on embryonic development, especially in human embryonic models. In this study, we evaluated the effect of two ginsenosides (Rg3 and Rh2) on human embryonic development, using embryoid bodies and three-dimensional (3D) aggregates of pluripotent stem cells. We exposed embryoid bodies to varying concentrations of Rg3 and Rh2 (5, 10, and 25μg/mL), and their embryotoxicity was evaluated by measuring the size of the embryoid body and the expression of epithelial-mesenchymal transition (EMT) markers. The growth rates of embryoid bodies were reduced upon treatment with a high concentration (25μg/mL) of Rg3 and Rh2. In addition, Rg3 induced E-cadherin expression while inhibiting N-cadherin and vimentin expression, which implies the inhibition of EMT. Such a change in E-cadherin expression was not observed after Rh2 treatment, but the inhibition of N-cadherin and vimentin expression was observed to be consistent with that observed on treatment with Rg3. Taken together, using the human embryoid model, we found that the two active ginsenosides, Rg3 and Rh2, induce aberrant embryoid body formation and ablate normal EMT.

Production of homogenous size‐controlled human induced pluripotent stem cell aggregates using ring‐shaped culture vessel

Aggregate size is an important parameter that determines the cell fate and quality of the resulting human-induced pluripotent stem cells (hiPSCs). Nowadays, large-scale suspension culture is a common method for scaling-up the biomanufacturing of hiPSCs to realize their practical application. However, this culture system exhibits a complex hydrodynamic condition resulting from the different mixing conditions of culture media, which potentially produce non-uniform aggregates, which may decrease the quality of the cell yield. Here, we performed expansion in a ring-shaped culture vessel and compared it with three other suspension-based culture systems to evaluate the uniformity and characteristics of hiPSC aggregates. Morphologically, the hiPSC aggregates formed and expanded in the ring-shaped culture vessel, resulting in small and uniform aggregates compared to the other culture systems. This aggregate population showed a decent mass transfer required for the exchange of biochemical substances, such as nutrients, growth factors, oxygen, and waste metabolic products, inside the aggregates. Thus, better metabolic performance and pluripotency markers were achieved in this system. Interestingly, all culture systems used in this study showed different tendencies in embryoid body differentiation. The smaller aggregates produced by sphere ring and dish bag tended to differentiate toward ectodermal and mesodermal lineages, while predominantly larger aggregates from the 6-well plates and spinner flask exhibited more potential for endodermal lineage. Our study demonstrates the production of a decent homogenous aggregate population by providing equal hydrodynamic force through the ring-shaped culture vessel design, which may be further upscaled to produce a large number of hiPSCs for clinical applications.

Single-cell-resolved differentiation of human induced pluripotent stem cells into pancreatic duct-like organoids on a microwell chip.

Creating in vitro models of diseases of the pancreatic ductal compartment requires a comprehensive understanding of the developmental trajectories of pancreas-specific cell types. Here, we report the single-cell characterization of the differentiation of pancreatic duct-like organoids (PDLOs) from human induced pluripotent stem cells (hiPSCs) on a microwell chip that facilitates the uniform aggregation and chemical induction of hiPSC-derived pancreatic progenitors. Via time-resolved single-cell transcriptional profiling and immunofluorescence imaging of the forming PDLOs, we identified differentiation routes from pancreas progenitors through ductal intermediates to two types of mature duct-like cell and a few non-ductal cell types. PDLO subpopulations expressed either mucins or the cystic fibrosis transmembrane conductance regulator, and resembled human adult duct cells. We also used the chip to uncover ductal markers relevant to pancreatic carcinogenesis, and to establish PDLO co-cultures with stellate cells, which allowed for the study of epithelial–mesenchymal signalling. The PDLO microsystem could be used to establish patient-specific pancreatic-duct models.

Axial elongation of caudalized human organoids mimics aspects of neural tube development.

Axial elongation of the neural tube is crucial during mammalian embryogenesis for anterior-posterior body axis establishment and subsequent spinal cord development, but these processes cannot be interrogated directly in humans as they occur post-implantation. Here, we report an organoid model of neural tube extension derived from human pluripotent stem cell (hPSC) aggregates that have been caudalized with Wnt agonism, enabling them to recapitulate aspects of the morphological and temporal gene expression patterns of neural tube development. Elongating organoids consist largely of neuroepithelial compartments and contain TBXT+SOX2+ neuro-mesodermal progenitors in addition to PAX6+NES+ neural progenitors. A critical threshold of Wnt agonism stimulated singular axial extensions while maintaining multiple cell lineages, such that organoids displayed regionalized anterior-to-posterior HOX gene expression with hindbrain (HOXB1) regions spatially distinct from brachial (HOXC6) and thoracic (HOXB9) regions. CRISPR interference-mediated silencing of TBXT, a Wnt pathway target, increased neuroepithelial compartmentalization, abrogated HOX expression and disrupted uniaxial elongation. Together, these results demonstrate the potent capacity of caudalized hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.

Human heart-forming organoids recapitulate early heart and foregut development

Organoid models of early tissue development have been produced for the intestine, brain, kidney and other organs, but similar approaches for the heart have been lacking. Here we generate complex, highly structured, three-dimensional heart-forming organoids (HFOs) by embedding human pluripotent stem cell aggregates in Matrigel followed by directed cardiac differentiation via biphasic WNT pathway modulation with small molecules. HFOs are composed of a myocardial layer lined by endocardial-like cells and surrounded by septum-transversum-like anlagen; they further contain spatially and molecularly distinct anterior versus posterior foregut endoderm tissues and a vascular network. The architecture of HFOs closely resembles aspects of early native heart anlagen before heart tube formation, which is known to require an interplay with foregut endoderm development. We apply HFOs to study genetic defects in vitro by demonstrating that NKX2.5-knockout HFOs show a phenotype reminiscent of cardiac malformations previously observed in transgenic mice.

Enhanced Neuronal Activity and Asynchronous Calcium Transients Revealed in a 3D Organoid Model of Alzheimer’s Disease

Advances in the development of three-dimensional (3D) brain organoids maintained in vitro have provided excellent opportunities to study brain development and neurodegenerative disorders, including Alzheimer's disease (AD). However, there remains a need to generate AD organoids bearing patient-specific genomic backgrounds that can functionally recapitulate the key features observed in the AD patient's brain. To address this need, we described a strategy to generate self-organizing 3D cerebral organoids which develop a functional neuronal network connectivity. This was achieved by neuroectoderm induction of human pluripotent stem cell (hPSCs) aggregates and subsequent differentiation into desired neuroepithelia and mature neurons in a 3D Matrigel matrix. Using this approach, we successfully generated AD cerebral organoids from human pluripotent stem cells (hPSCs) derived from a familial AD patient with a common mutation in presenilin 2 (PSEN2N141I). An isogenic control with an identical genetic background but wild-type PSEN2 was generated using CRISPR/Cas9 technology. Both control and AD organoids were characterized by analyzing their morphology, the Aβ42/Aβ40 ratio, functional neuronal network activity, drug sensitivity, and the extent of neural apoptosis. The spontaneous activity of the network and its synchronization was measured in the organoids via calcium imaging. We found that compared with the mutation-corrected control organoids, AD organoids had a higher Aβ42/Aβ40 ratio, asynchronous calcium transients, and enhanced neuronal hyperactivity, successfully recapitulating an AD-like pathology at the molecular, cellular, and network level in a human genetic context. Moreover, two drugs which increase neuronal activity, 4-aminopyridine (4-AP) and bicuculline methochloride, induced high-frequency synchronized network bursting to a similar extent in both organoids. Therefore, our study presents a promising organoid-based biosystem for the study of the pathophysiology of AD and a platform for AD drug development.

Protection of human induced pluripotent stem cells against shear stress in suspension culture by Bingham plastic fluid.

Suspension culture is an important method used in the industrial preparation of pluripotent stem cells (PSCs), for regenerative therapy and drug screening. Generally, a suspension culture requires agitation to keep PSC aggregates suspended and to promote mass transfer, but agitation also causes cell damage. In this study, we investigated the use of a Bingham plastic fluid, supplemented with a polysaccharide‐based polymer, to preserve PSCs from cell damage in suspension culture. Rheometric analysis showed that the culture medium gained yield stress and became a Bingham plastic fluid, after supplementation with the polymer FP003. A growth/death analysis revealed that 2 days of aggregate formation and 2 days of suspension in the Bingham plastic medium improved cell growth and prevented cell death. After the initial aggregation step, whereas strong agitation (120 rpm) of a conventional culture medium resulted in massive cell death, in the Bingham plastic fluid we obtained the same growth as the normal culture with optimal agitation (90 rpm). This indicates that Bingham plastic fluid protected cells from shear stress in suspension culture and could be used to enhance their robustness when developing a large‐scale.

Cell Mechanics in Embryoid Bodies.

Embryoid bodies (EBs) resemble self-organizing aggregates of pluripotent stem cells that recapitulate some aspects of early embryogenesis. Within few days, the cells undergo a transition from rather homogeneous epithelial-like pluripotent stem cell colonies into a three-dimensional organization of various cell types with multifaceted cell–cell interactions and lumen formation—a process associated with repetitive epithelial-mesenchymal transitions. In the last few years, culture methods have further evolved to better control EB size, growth, cellular composition, and organization—e.g., by the addition of morphogens or different extracellular matrix molecules. There is a growing perception that the mechanical properties, cell mechanics, and cell signaling during EB development are also influenced by physical cues to better guide lineage specification; substrate elasticity and topography are relevant, as well as shear stress and mechanical strain. Epithelial structures outside and inside EBs support the integrity of the cell aggregates and counteract mechanical stress. Furthermore, hydrogels can be used to better control the organization and lineage-specific differentiation of EBs. In this review, we summarize how EB formation is accompanied by a variety of biomechanical parameters that need to be considered for the directed and reproducible self-organization of early cell fate decisions.

The role of Hippo signaling pathway and mechanotransduction in tuning embryoid body formation and differentiation.

Embryoid bodies (EBs) are the three-dimensional aggregates of pluripotent stem cells that are used as a model system for the in vitro differentiation. EBs mimic the early stages of embryogenesis and are considered as a potential biomimetic body in tuning the stem cell fate. Although EBs have a spheroid shape, they are not formed accidentally by the agglomeration of cells; they are formed by the deliberate and programmed aggregation of stem cells in a complex topological and biophysical microstructure instead. EBs could be programmed to promisingly differentiate into the desired germ layers with specific cell lineages, in response to intra- and extra-biochemical and biomechanical signals. Hippo signaling and mechanotransduction are the key pathways in controlling the formation and differentiation of EBs. The activity of the Hippo pathway strongly relies on cell-cell junctions, cell polarity, cellular architecture, cellular metabolism, and mechanical cues in the surrounding microenvironment. Although the Hippo pathway was initially thought to limit the size of the organ by inhibiting the proliferation and the promotion of apoptosis, the evidence suggests that this pathway even regulates stem cell self-renewal and differentiation. Considering the abovementioned explanations, the present study investigated the interplay of the Hippo signaling pathway, mechanotransduction, differentiation, and proliferation pathways to draw the molecular network involved in the control of EBs fate. In addition, this study highlighted several neglected critical parameters regarding EB formation, in the interplay with the Hippo core component involved in the promising differentiation.

Gaps in Embryo Model Ethics

Embryo models are aggregates of pluripotent stem cells that exhibit aspects of embryonic development. Investigators use embryo models to study mammalian development and prevent adverse outcomes in pregnancy. However, researchers have called for debate on ethical guidelines for the use of embryo models. In addition, the International Society for Stem Cell Research (ISSCR) has announced that it will update its research guidelines to more fully address embryo models. If embryo models are equivalent to human embryos, then they deserve the respect afforded to all humans. The definition of the organismic potential of an embryo model should not require complete mature development or the presence of all of the typical organism’s parts. There are explanatory gaps in the ISSCR’s published recommended guidelines. The research needed to determine the nature of the human embryo model places the model in danger; thus, principled caution is needed in moving forward.

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.

CC chemokine CCL1 receptor CCR8 mediates conversion of mesenchymal stem cells to embryoid bodies expressing FOXP3+CCR8+ regulatory T cells.

Embryoid bodies (EBs) are three dimensional aggregates of pluripotent stem cells primarily used to investigate morphogenesis and cell toxicity, are also attractive tools in regenerative medicine. While embryonic stem cells (ESCs) and induced pluripotent cells (IPSCs) have been shown to form EBs in mouse, primate and humans, EB formation have not been previously demonstrated in mesenchymal stem cells (MSCs). Here we show that rat MSCs form EBs; which express regulatory T cell (Treg) marker Foxp3 and CC chemokine CCL1 receptor CCR8. We show a novel method for formation of EBs from MSCs under stress and demonstrate that the induction of FoxP3+ CCR8+ EBs is dependent upon CCL1 gradients which mediate cell proliferation, migration and invasion of mTregs. The identification of EBs and novel FoxP3+ CCR8+ regulatory T cells (mTregs) for selective conversion and isolation of bone marrow derived MSCs offers novel avenues for research, diagnosis and treatment.

Scale up of allogeneic cell therapy manufacturing in single-use bioreactors: challenges, insights and solutions

Background & Aim Many allogeneic cell therapy drug candidates are getting closer to commercialization. However, lack of a scalable manufacturing platform to meet commercial demands could be a potential bottleneck for the future success of the cell therapy industry. With the benefits of high volumetric productivity and controllability of cell culture processes, single-use bioreactors are recognized as promising solutions for large-scale manufacturing of cell therapy products. However, cell therapy products have unique bioprocessing requirements as not only is the final product the cell itself, but they are anchorage-dependent and grow on microcarriers or as cell aggregates. These microcarriers and cell aggregates require greater power input to be suspended in a bioreactor, which can lead to hydrodynamic sheer stress and damage to cells. A single-use bioreactor that can suspend the large particles homogeneously in a low shear environment and provide evenly distributed dissipation energy inside the vessel consistently across various working volumes would be greatly beneficial for scale up of cell therapy manufacturing. Methods, Results & Conclusion A novel, single-use Vertical-Wheel (VW) bioreactor system was designed in an attempt to provide a solution to these challenges. Experiments with various cell types such as human mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), pluripotent stem cells (PSCs), and chondrocytes were performed in different sizes of VW bioreactors with the following results. Comparable final cell densities of MSCs in a xeno-free microcarrier culture was achieved in four different scales of VW bioreactors (0.1L, 3L, 15L, and 80L). More uniform size ESC aggregates were achieved in 0.5L VW bioreactors compared to the ESCs grown in stirred-type spinner flasks. Furthermore, the narrow range of cell aggregate size distribution achieved in 0.5L VW bioreactors was reproduced to larger 3L scale. A test by specific surface marker identifiers indicated that the pluripotency of PSC aggregates after cell expansion in the bioreactor was maintained. Subsequent directed differentiation of PSCs after cell expansion in a single-use bioreactor is another challenge of manufacturing scale up. VW bioreactors have been used to successfully differentiate PSCs into different types of target cells, such as insulin-producing islets or cerebellar organoids. Further details regarding manufacturing challenges, experimental data, and potential solutions will be discussed in this presentation.

Automated Closed-System Expansion of Pluripotent Stem Cell Aggregates in a Rocking-Motion Bioreactor.

Pluripotent stem cell suspension aggregates have proven to be an efficient and phenotypically stable means for expansion and directed differentiation. Bioreactor systems with automation of perfusion, fluidization, and gas exchange are essential for scaling up pluripotent stem cell cultures. Since stem cell pluripotency and differentiation are affected by both chemical and physical signals, we investigated a low-shear method for the expansion of cells in a rocking-motion bioreactor. The rocking motion drives continual mixing and aeration, and the single-use disposable bioreactors avoid issues around contamination during seeding, medium exchange, passage, and cell harvest. Serial passaging from a 150 mL to a 1 L scale was demonstrated, achieving cell densities of up to 4 million cells/mL. In an average of 13 experiments, pluripotent stem cell aggregates expanded 5.7-fold (with maximal 9.5-fold expansion) and maintained 97% viability over 4 days in a rocking bioreactor culture. In seven experiments with improved culture conditions, the average expansion was 6.8-fold. Maintenance of pluripotency was confirmed by differentiation to all three germ layers and surface marker expression, and the expanded aggregates maintained a stable normal karyotype. The automation associated with the rocking platform bioreactor required no user intervention during the 4-day culture, providing hands-off expansion of pluripotent stem cells.

Botulinum hemagglutinin-mediated in situ break-up of human induced pluripotent stem cell aggregates for high-density suspension culture.

Large numbers of human induced pluripotent stem cells (hiPSCs) are required for making stable cell bank. Although suspension culture yields high cell numbers, there remain unresolved challenges for obtaining high-density of hiPSCs because large size aggregates exhibit low growth rates. Here, we established a simple method for hiPSC aggregate break-up using botulinum hemagglutinin (HA), which specifically bound with E-cadherin and disrupted cell-cell connections in hiPSC aggregates. HA showed temporary activity for disrupting the E-cadherin-mediated cell-cell connections to facilitate the break-up of aggregates into small sizes only 9 hr after HA addition. The transportation of HA into the aggregates was mediated by transcellular and paracellular way after HA addition to the culture medium. hiPSC aggregates broken up by HA showed a higher number of live cells, higher cell density, and higher expansion fold compared to those of aggregates dissociated with enzymatic digestion. Moreover, a maximum cell density of 4.5 ± 0.2 × 106 cells ml-1 was obtained by aggregate break-up into small ones, which was three times higher than that with the conventional culture without aggregate break-up. Therefore, the temporary activity of HA for disrupting E-cadherin-mediated cell-cell connection was key to establishing a simple in situ method for hiPSC aggregate break-up in bioreactors, leading to high cell density in suspension culture.

Developing a Cost-Effective and Scalable Production of Human Hepatic Competent Endoderm from Size-Controlled Pluripotent Stem Cell Aggregates.

Dynamic suspension culture of human pluripotent stem cells (hPSCs) in stirred bioreactors provides a valuable scalable culture platform for integrated differentiation toward different lineages for potential research and therapeutic applications. However, current protocols for scalable and integrated differentiation of hPSCs limited due to high cost of growth factors and technical challenges. Here, hPSCs aggregates primed with 6 and 12 μM of CHIR99021 (CHIR), a Wnt agonist, in combination with different concentrations of high cost Activin A (10, 25, 50, 100 ng/mL). We sought to determine the appropriate treatment duration for efficient and cost-effective differentiation protocol for foregut definitive endoderm production in a dynamic suspension culture. Afterward, we evaluated the impact of the initial hPSC aggregate sizes (small: 86 ± 18 μm; medium: 142 ± 32 μm; large: 214 ± 34 μm) as critical bioprocess parameter on differentiation efficacy at the beginning of induction. The results indicated that 1-day priming of hPSCs as 3D aggregates (hPSpheres) with 6 μM CHIR followed by treatment with a low concentration of Activin (10 ng/mL) for 2 days resulted in efficient differentiation to definitive endoderm. This finding confirmed by the presence of ≥70% SOX17/FOXA2-double positive cells that highly expressed the anterior endodermal marker HEX. These endodermal cells differentiated efficiently into mature functional hepatocytes [60% albumin (ALB)-positive cells]. The results showed that the initial size of hPSC aggregates significantly impacted on the efficacy of differentiation. The medium sized-hPSpheres resulted in higher productivity and differentiation efficiency for scalable hepatocytes production, whereas small aggregates resulted in significant cell-loss after CHIR treatment and large aggregates had less efficacious endodermal differentiation. Differentiated cells exhibited multiple characteristics of primary hepatocytes as evidenced by expressions of liver-specific markers, indocyanine green and low-density lipoprotein uptake, and glycogen storage. Thus, this platform could be employed for scalable production of hPSC-derived hepatocytes for clinical and drug discovery applications.

In Vitro Haematopoietic Differentiation from Pluripotent Stem Cells or by Direct Lineage Conversion: Current Advances and Challenges

The feasibility and possibility of in vitro haematopoiesis for clinical use such as cell therapy or substitution therapy have been discussed for years. In this review, we summarized the most promising and efficient strategies for in vitro haematopoietic cells production: the three-dimensional aggregates of pluripotent stem cells called embryoid bodies, a co-culturing system using feeder cells, and an extracellular matrix-coated dish system. We discussed the terminal differentiation of various types of blood cells using pluripotent stem cells or by direct lineage conversion.