Early prediction of the differentiation potential during the formation of human iPSC-derived embryoid bodies

Genes Involved in DNA Repair and Mitophagy Protect Embryoid Bodies from the Toxic Effect of Methylmercury Chloride under Physioxia Conditions

The formation of embryoid bodies (EBs) from human pluripotent stem cells resembles the early stages of human embryo development, mimicking the organization of three germ layers. In our study, EBs were tested for their vulnerability to chronic exposure to low doses of MeHgCl (1 nM) under atmospheric (21%O₂) and physioxia (5%O₂) conditions. Significant differences were observed in the relative expression of genes associated with DNA repair and mitophagy between the tested oxygen conditions in nontreated EBs. When compared to physioxia conditions, the significant differences recorded in EBs cultured at 21% O₂ included: (1) lower expression of genes associated with DNA repair (ATM, OGG1, PARP1, POLG1) and mitophagy (PARK2); (2) higher level of mtDNA copy number; and (3) higher expression of the neuroectodermal gene (NES). Chronic exposure to a low dose of MeHgCl (1 nM) disrupted the development of EBs under both oxygen conditions. However, only EBs exposed to MeHgCl at 21% O₂ revealed downregulation of mtDNA copy number, increased oxidative DNA damage and DNA fragmentation, as well as disturbances in SOX17 (endoderm) and TBXT (mesoderm) genes expression. Our data revealed that physioxia conditions protected EBs genome integrity and their further differentiation.

Integrating Oxygen and 3D Cell Culture System: A Simple Tool to Elucidate the Cell Fate Decision of hiPSCs

Oxygen, as an external environmental factor, plays a role in the early differentiation of human stem cells, such as induced pluripotent stem cells (hiPSCs). However, the effect of oxygen concentration on the early-stage differentiation of hiPSC is not fully understood, especially in 3D aggregate cultures. In this study, we cultivated the 3D aggregation of hiPSCs on oxygen-permeable microwells under different oxygen concentrations ranging from 2.5 to 20% and found that the aggregates became larger, corresponding to the increase in oxygen level. In a low oxygen environment, the glycolytic pathway was more profound, and the differentiation markers of the three germ layers were upregulated, suggesting that the oxygen concentration can function as a regulator of differentiation during the early stage of development. In conclusion, culturing stem cells on oxygen-permeable microwells may serve as a platform to investigate the effect of oxygen concentration on diverse cell fate decisions during development.

Strategies for differentiation of hiPSCs into dental epithelial cell lineage

Different stem cell-based strategies, especially induced pluripotent stem cells (iPSCs), have been exploited to regenerate teeth or restore biological and physiological functions after tooth loss. Further research is needed to establish an optimized protocol to effectively differentiate human iPSCs (hiPSCs) into dental epithelial cells (DECs). In this study, various factors were precisely modulated to facilitate differentiation of hiPSCs into DECs, which are essential for the regeneration of functional teeth. Embryoid bodies (EBs) were formed from hiPSCs as embryo-like aggregates, retinoic acid (RA) was used as an early ectodermal inducer, and bone morphogenic protein 4 (BMP4) activity was manipulated. The characteristics of DECs were enhanced and preserved after culture in keratinocyte serum-free medium (K-SFM). The yielded cell population exhibited noticeable DEC characteristics, consistent with the expression of epithelial cell and ameloblast markers. DECs demonstrated odontogenic abilities by exerting an inductive effect on human dental pulp stem cells (hDPSCs) and forming a tooth-like structure with the mouse tooth mesenchyme. Overall, our differentiation protocol provides a practical approach for applying hiPSCs for tooth regeneration.

Novel Methods to Mobilize, Isolate, and Expand Mesenchymal Stem Cells

Numerous studies demonstrate the essential role of mesenchymal stem cells (MSCs) in the treatment of metabolic and inflammatory diseases, as these cells are known to modulate humoral and cellular immune responses. In this manuscript, we efficiently present two novel approaches to obtain MSCs from equine or human sources. In our first approach, we used electro-acupuncture as previously described by our group to mobilize MSCs into the peripheral blood of horses. For equine MSC collection, culture, and expansion, we used the Miltenyi Biotec CliniMACS Prodigy system of automated cell manufacturing. Using this system, we were able to generate appoximately 100 MSC colonies that exhibit surface marker expression of CD105 (92%), CD90 (85%), and CD73 (88%) within seven days of blood collection. Our second approach utilized the iPSC embryoid bodies from healthy or diabetic subjects where the iPSCs were cultured in standard media (endothelial + mesoderm basal media). After 21 days, the cells were FACS sorted and exhibited surface marker expression of CD105, CD90, and CD73. Both the equine cells and the human iPSC-derived MSCs were able to differentiate into adipogenic, osteogenic, and chondrogenic lineages. Both methods described simple and highly efficient methods to produce cells with surface markers phenotypically considered as MSCs and may, in the future, facilitate rapid production of MSCs with therapeutic potential.

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.

Differential genetic mutations of ectoderm, mesoderm, and endoderm-derived tumors in TCGA database

Background

In terms of biological behavior, gene regulation, or signaling pathways, there is a certain similarity between tumorigenesis and embryonic development of humans. Three germ layer structure exhibits the distinct ability to form specific tissues and organs.

Methods

The present study set out to investigate the genetic mutation characteristics of germ layer differentiation-related genes using the tumor cases of the cancer genome atlas (TCGA) database.

Results

These tumor samples were divided into three groups, including the ectoderm, mesoderm, and endoderm. Children cases less than 9 years old accounted for a larger proportion for the cases in the ectoderm and mesoderm groups; whereas the middle-aged and elderly individuals (from 50 to 89 years old) were more susceptible to tumors of endoderm. There was a better prognosis for the cases of mesoderm, especially the male with the race of White, compared with the other groups. A missense mutation was frequently detected for the cases of ectoderm and endoderm, while deletion mutation was common for that of mesoderm. We could not identify the ectoderm, mesoderm, or endoderm-specific mutated genes or variants with high mutation frequency. However, there was a relatively higher mutation incidence of endoderm markers (GATA6, FOXA2, GATA4, AFP) in the endoderm group, compared with the groups of ectoderm and mesoderm. Additionally, four members (SMO, GLI1, GLI2, GLI3) within the Hedgehog signaling pathway genes showed a relatively higher mutation rate in the endoderm group than the other two groups.

Conclusions

TCGA tumors of ectoderm, mesoderm, and endoderm groups exhibit the distinct subject distribution, survival status, and genomic alteration characteristics. The synergistic mutation effect of specific genes closely related to embryonic development may contribute to the tumorigenesis of tissues or organs derived from the specific germ layers. This study provides a novel reference for exploring the functional connection between embryogenesis and tumorigenesis.

Post-Vaccination Yellow Fever Antiserum Reduces Zika Virus in Embryoid Bodies When Placental Cells are Present

Zika virus (ZIKV) is a flavivirus that originated in Africa but emerged in Latin America in 2015. In this region, other flaviviruses such as Dengue (DENV), West Nile, and Yellow Fever virus (YFV) also circulate, allowing for possible antigenic cross-reactivity to impact viral infections and immune responses. Studies have found antibody-mediated enhancement between DENV and ZIKV, but the impact of YFV antibodies on ZIKV infection has not been fully explored. ZIKV infections cause congenital syndromes, such as microcephaly, necessitating further research into ZIKV vertical transmission through the placental barrier. Recent advancements in biomedical engineering have generated co-culture methods that allow for the in vitro recapitulation of the maternal–fetal interface. This study utilized a transwell assay, which was a co-culture model utilizing human placental syncytiotrophoblasts, fetal umbilical cells, and a differentiating embryoid body, to replicate the maternal–fetal axis. To determine if cross-reactive YFV vaccine antibodies impacted the pathogenesis of ZIKV across the maternal–fetal axis, syncytiotrophoblasts were inoculated with ZIKV or ZIKV incubated with YFV vaccine antisera, and the viral load was measured 72 h post-inoculation. Here, we report that BeWo and HUVEC cells were permissive to ZIKV and that the impact of YFV post-vaccination antibodies on ZIKV replication was cell line-dependent. Embryoid bodies were also permissive to ZIKV, and the presence of YFV antibodies collected 4–14 months post-vaccination reduced ZIKV infection when placental cells were present. However, when directly infected with ZIKV, the embryoid bodies displayed significantly increased viral loads in the presence of YFV antiserum taken 30 days post-vaccination. The data show that each of the cell lines and EBs have a unique response to ZIKV complexed with post-vaccination serum, suggesting there may be cell-specific mechanisms that impact congenital ZIKV infections. Since ZIKV infections can cause severe congenital syndromes, it is crucial to understand any potential enhancement or protection offered from cross-reactive, post-vaccination antibodies.

Practical choice for robust and efficient differentiation of human pluripotent stem cells

Human pluripotent stem cells (hPSCs) have the distinct advantage of being able to differentiate into cells of all three germ layers. Target cells or tissues derived from hPSCs have many uses such as drug screening, disease modeling, and transplantation therapy. There are currently a wide variety of differentiation methods available. However, most of the existing differentiation methods are unreliable, with uneven differentiation efficiency and poor reproducibility. At the same time, it is difficult to choose the optimal method when faced with so many differentiation schemes, and it is time-consuming and costly to explore a new differentiation approach. Thus, it is critical to design a robust and efficient method of differentiation. In this review article, we summarize a comprehensive approach in which hPSCs are differentiated into target cells or organoids including brain, liver, blood, melanocytes, and mesenchymal cells. This was accomplished by employing an embryoid body-based three-dimensional (3D) suspension culture system with multiple cells co-cultured. The method has high stable differentiation efficiency compared to the conventional 2D culture and can meet the requirements of clinical application. Additionally, ex vivo co-culture models might be able to constitute organoids that are highly similar or mimic human organs for potential organ transplantation in the future.

Generation of Human iMelanocytes from Induced Pluripotent Stem Cells through a Suspension Culture System

Melanocytes, derived from neural crest cells, are involved in melanin production. This protocol describes a method to generate induced melanocytes (iMelanocytes) from human induced pluripotent stem cells (iPSCs) using a suspension culture system, which considerably improves the differentiation efficiency. The most critical parts of this protocol are the selection of a reliable iPSC line with strong potential to differentiate into melanocytes and their stemness maintenance.

For complete information on the use and generation of this protocol, please refer to our Cell Reports article, Liu el al. (2019).

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Selection of reliable iPSC lines and their stemness maintenance is critical

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EB-based suspensive system enhances efficiency of iMelanocytes generation

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EBs characterized by smooth borders and dark centers without cavities are preferred

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Quality control is performed through morphology checks and melanocyte markers

Inducing human induced pluripotent stem cell differentiation through embryoid bodies: A practical and stable approach

Human induced pluripotent stem cells (hiPSCs) are invaluable resources for producing high-quality differentiated cells in unlimited quantities for both basic research and clinical use. They are particularly useful for studying human disease mechanisms in vitro by making it possible to circumvent the ethical issues of human embryonic stem cell research. However, significant limitations exist when using conventional flat culturing methods especially concerning cell expansion, differentiation efficiency, stability maintenance and multicellular 3D structure establishment, differentiation prediction. Embryoid bodies (EBs), the multicellular aggregates spontaneously generated from iPSCs in the suspension system, might help to address these issues. Due to the unique microenvironment and cell communication in EB structure that a 2D culture system cannot achieve, EBs have been widely applied in hiPSC-derived differentiation and show significant advantages especially in scaling up culturing, differentiation efficiency enhancement, ex vivo simulation, and organoid establishment. EBs can potentially also be used in early prediction of iPSC differentiation capability. To improve the stability and feasibility of EB-mediated differentiation and generate high quality EBs, critical factors including iPSC pluripotency maintenance, generation of uniform morphology using micro-pattern 3D culture systems, proper cellular density inoculation, and EB size control are discussed on the basis of both published data and our own laboratory experiences. Collectively, the production of a large quantity of homogeneous EBs with high quality is important for the stability and feasibility of many PSCs related studies.