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.

Body Building on Diamonds

Whereas conservative therapies aim to stall the advance of disease,regenerative medicine strives to reverse it.The capacity of most tissues to regenerate derives from stem cells,but there are a number of barriers which have to be circumvented before it will be possible to use stem-cell-based therapies.Such therapies,however,are expected to improve human health enormously, and knowledge gained from studying stem cells in culture and in model organisms is now laying the groundwork for a new era of regenerative medicine.One of the most prominent methods to study stem cell differentiation is to let them to form embryoid bodies.Under favourable conditions any stem cell line will form embryoid bodies.However,the mechanism of the formation of embryoid bodies is not very well understood,and to produce them in the laboratory is in no way trivial-an important technical barrier in stem cell research.Recently,the embryoid body cultivation step has been successfully circumvented for the derivation of osteogenic cultures of embryonic stem cells.Here we report on a simple and reusable system to cultivate embryoid bodies in extremely short times.The method is inspired by the principles that lead to the establishment of the biomimetic triangle.

Differentiation of neuron-like cells from mouse parthenogenetic embryonic stem cells

Parthenogenetic embryonic stem cells have pluripotent differentiation potentials, akin to fertilized embryo-derived embryonic stem cells. The aim of this study was to compare the neuronal differentiation potential of parthenogenetic and fertilized embryo-derived embryonic stem cells. Before differentiation, karyotype analysis was performed, with normal karyotypes detected in both parthenogenetic and fertilized embryo-derived embryonic stem cells. Sex chromosomes were identified as XX. Immunocytochemistry and quantitative real-time PCR detected high expression of the pluripotent gene, Oct4, at both the mRNA and protein levels, indicating pluripotent differentiation potential of the two embryonic stem cell subtypes. Embryonic stern cells were induced with retinoic acid to form embryoid bodies, and then dispersed into single cells. Single cells were differentiated in N2 differentiation medium for 9 days. Immunocytochemistry showed parthenogenetic and fertilized embryo-derived embryonic stem cells both express the neuronal cell markers nestin, ~lll-tubulin and myelin basic protein. Quantitative real-time PCR found expression of neuregenesis related genes （Sox-1, Nestin, GABA, Pax6, Zic5 and Pitxl） in both types of embryonic stem cells, and Oct4 expression was significantly decreased. Nestin and Pax6 expression in parthenogenetic embryonic stem cells was significantly higher than that in fertilized embryo-derived embryonic stem cells. Thus, our experimental findings indicate that parthenogenetic embryonic stem cells have stronger neuronal differentiation potential than fertilized embryo-derived embryonic stem cells.

The Defined siRNAs Suppress Nanog and Sox2 Expressions in Mouse ES Cells

Nanog, Oct4 and Sox2 are important transcription factors that are expressed in embryonic stem （ES） cells or embryonic carcinoma （EC） cells, but in most cases they are absent in somatic cells. These factors play a key role to maintain embryonic stem cell self-renew and pluripotency. Down-regulation of Nanog and Sox2 gene expression can change multiple gene expression pattems and signal transduction pathways, and will initiate ES cell differentiation. This study was designed to select the efficient small interfering RNA （siRNA） fragments that inhibit Nanog and Sox2 gene expression in mouse J1 ES cells and P19 EC cells. Among synthesized siRNAs we screened out the siRNA N301 for Nanog and siRNA $720 for Sox2, which not only down- regulated of Nanog and Sox2 gene expression, but also interfered embryoid bodies formation. Our study provided the defined siRNA fragments that could be used to investigate the epigenetic function of Nanog and Sox2 genes.

Study on Artificial Seeds of Plants

The establishment and development of artificial seed technology is to quickly reproduce excellent varieties or hybrids,which can be applied to hybrid generation seeds produced by the three-two line method.For some varieties that are difficult to propagate with seeds or plant species with unstable genetic traits and poor fertility,artificial seed technology can also be used for mass reproduction.In particular,some new plants created through genetic engineering,such as somatic hybrids or transgenic plants,can be propagated or maintained by artificial seed technology.In addition,artificial seed technology can be used for the maintenance and rapid propagation of virus-free seedlings.Compared with ordinary test tube seedlings,artificial seeds have low cost,convenient transportation,and to a certain extent reduce vitrified seedlings.In particular,the production of artificial seeds does not occupy a large amount of soil.It can be produced all year round.Therefore,the research on artificial seeds has developed rapidly in the world.

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.

Embryoid bodies formation and differentiation from mouse embryonic stem cells in collagen/Matrigel scaffolds

Embryonic stem （ES） cells have the potential to develop into any type of tissue and are considered as a promising source of seeding cells for tissue engineering and transplantation therapy.The main catalyst for ES cells differentiation is the growth into embryoid bodies （EBs）,which are utilized widely as the trigger of in vitro differentiation.In this study,a novel method for generating EBs from mouse ES cells through culture in collagen/Matrigel scaffolds was successfully established.When single ES cells were seeded in three dimensional collagen/Matrigel scaffolds,they grew into aggregates gradually and formed simple EBs with circular structures.After 7 days＇ culture,they formed into cystic EBs that would eventually differentiate into the three embryonic germ layers.Evaluation of the EBs in terms of morphology and potential to differentiate indicated that they were typical in structure and could generate various cell types;they were also able to form into tissue-like structures.Moreover,with introduction of ascorbic acid,ES cells differentiated into cardiomyocytes efficiently and started contracting synchronously at day 19.The results demonstrated that collagen/Matrigel scaffolds supported EBs formation and their subsequent differentiation in a single three dimensional environment.

Human embryoid bodies to hepatocyte-like clusters:Preparing for translation

End-stage liver disease and acute liver failure are some of the most common causes of death worldwide,affecting over 40,000 patients in the United States,for most of whom liver transplantation is the only treatment.Transplantable livers are obtained primarily from deceased donors in the west and living donors in the east,with demand outstripping supply,leading to thousands of deaths each year for those on the transplant waiting lists.As a bridge to liver transplantation,human primary hepatocytes have been transplanted with low success,owing to their inability to grow and expand in vitro,their high sensitivity to cold storage-induced damage,and their dedifferentiation following two-dimensional culture.In the past decade,human induced pluripotent stem cells(hiPSCs)have been studied as a potential alternative to liver and primary hepatocyte transplantation through their differentiation into hepatocyte-like cells(HLCs).Differentiation of hiPSCs into HLCs is limited by the low percentage of differentiated cells that reach a mature hepatic phenotype,poor reproducibility of existing differentiation protocols,and inadequate long-term viability and function in vitro and in vivo.In this review,we will discuss the mechanisms of the various techniques that aim to improve the hepatic differentiation of hiPSCs into mature and genotypically stable HLCs for use in drug studies,as a potential bridge for liver transplantation after liver failure or as therapy for liver regeneration and replacement.

A matrigel-free method to generate matured human cerebral organoids using 3D-Printed microwell arrays

The current methods of generating human cerebral organoids rely excessively on the use of Matrigel or other external extracellular matrices(ECM)for cell micro-environmental modulation.Matrigel embedding is problematic for long-term culture and clinical applications due to high inconsistency and other limitations.In this study,we developed a novel microwell culture platform based on 3D printing.This platform,without using Matrigel or external signaling molecules(i.e.,SMAD and Wnt inhibitors),successfully generated matured human cerebral organoids with robust formation of high-level features(i.e.,wrinkling/folding,lumens,neuronal layers).The formation and timing were comparable or superior to the current Matrigel methods,yet with improved consistency.The effect of microwell geometries(curvature and resolution)and coating materials(i.e.,mPEG,Lipidure,BSA)was studied,showing that mPEG outperformed all other coating materials,while curved-bottom microwells outperformed flat-bottom ones.In addition,high-resolution printing outperformed low-resolution printing by creating faithful,isotropically-shaped microwells.The trend of these effects was consistent across all developmental characteristics,including EB formation efficiency and sphericity,organoid size,wrinkling index,lumen size and thickness,and neuronal layer thickness.Overall,the microwell device that was mPEG-coated,high-resolution printed,and bottom curved demonstrated the highest efficacy in promoting organoid development.This platform provided a promising strategy for generating uniform and mature human cerebral organoids as an alternative to Matrigel/ECM-embedding methods.

Study on Transplanting Germ Like Cells Differentiated from Embryonic Stem Cell into Mouse Seminiferous Tubules

Objective To investigate whether germ like cells isolated from embryoid body formed by mouse embryonic stem cells could survive and initiate spermatogenesis in seminiferous tubules of adult mice. Methods SSEA-1＋ cells were isolated from embryoid bodies prepared from mouse EGFP-ES cells, after retinoic acid treatment, the cells were detected for the expression of alkaline phosphatase, Rnh2, stella, fragilis, Tex14, Sry, Hsp90-a, Stra8 and integrin a6, and then, the cells were transplanted into seminiferous tubules of busulfan-treated adult mice. Results Six days after retinoic acid treatment, alkaline phosphatase expressing cells could still be found in embryoid body （EB） derived cells, indicating the existence of retinoic acid-resistant primordial germ cells. When the SSEA-1＋ cells isolated from embryoid bodies were stimulated with retinoic acid for 6 days, some of these cells expressed cell markers of Hsp90-a, Stra8 and integrin a6, resembling the expression profile of spermatogonial stem cells. Forty-five days after cell transplantation, a little amount of GFP-expressing cells attached to the basement membrane of seminiferous tubule and formed small colonies; Three months later, these cells started amplification in the form of cell chains with varied length, and moving towards the lumen of the seminiferous tubules. Five months after the transplantation, multilayered cell mass was found in seminiferous tubules of two, out of four recipient mice. There was no GFP-expressing cells existed in non-cell-transplanted seminiferous tubules. Conclusion In our study, although full-termed spermatogenesis was not observed in all of the recipients, the results did indicate that the embryoid body contains germ like cells, and these cells can survive and initiate amplification in seminiferous tubules of adult mouse.

Studying developmental neurotoxic effects of bisphenol A(BPA) using embryonic stem cells

There is little to no toxicity information regarding thousands of chemicals to which people are exposed daily.In fact,of the84,000 chemicals listed in the United States Toxic Substances Control Act Inventory,there is limited information available on their effects on neural development（Betts,2010;US EPA,2015）.