Human embryonic stem cells passaged using enzymatic methods retain a normal karyotype and express CD30

Process parameter development for the scaled generation of stem cell-derived pancreatic endocrine cells

Diabetes is a debilitating disease characterized by high blood glucose levels. The global prevalence of this disease has been projected to reach 700 million adults by the year 2045. Type 1 diabetes represents about 10% of the reported cases of diabetes. Although islet transplantation can be a highly effective method to treat type 1 diabetes, its widespread application is limited by the paucity of cadaveric donor islets. The use of pluripotent stem cells as an unlimited cell source to generate insulin‐producing cells for implant is a promising alternative for treating diabetes. However, to be clinically relevant, it is necessary to manufacture these stem cell‐derived cells at sufficient scales. Significant advances have been made in differentiation protocols used to generate stem cell‐derived cells capable of reversing diabetes in animal models and for testing in clinical trials. We discuss the potential of both stem cell‐derived pancreatic progenitors and more matured insulin‐producing cells to treat diabetes. We discuss the need for rigorous bioprocess parameter optimization and identify some critical process parameters and strategies that may influence the critical quality attributes of the cells with the goal of facilitating scalable manufacturing of human pluripotent stem cell‐derived pancreatic endocrine cells.

Human Induced Pluripotent Stem Cell (iPSC) Handling Protocols: Maintenance, Expansion, and Cryopreservation

Human induced pluripotent stem cells (iPSCs) have emerged as an invaluable resource for basic research, disease modeling, and drug discovery over recent years. Given the numerous advantages of iPSCs over alternative models-including their human origin, their ability to be differentiated into almost any cell type, and the therapeutic potential of patient-specific iPSCs in personalized medicine-many labs are now considering iPSC models for their studies. As the quality of the starting population of iPSCs is a key determinant in the success of any one of these applications, it is crucial to adhere to best practices in iPSC culture. In the following protocol, we offer a comprehensive guide to the culture, cryopreservation, and quality control methods required for the establishment and maintenance of high-quality iPSC cultures.

Editing the Genome of Human Induced Pluripotent Stem Cells Using CRISPR/Cas9 Ribonucleoprotein Complexes

Genome editing using the CRISPR/Cas9 system has rapidly established itself as an essential tool in the genetic manipulation of many organisms, including human cell lines. Its application to human induced pluripotent stem cells (hiPSCs) allows for the generation of isogenic cell pairs that differ in a single genetic lesion, and therefore the identification and characterization of causal genetic variants. We describe a simple, effective approach to perform delicate manipulations of the genome of hiPSCs through delivery of Cas9 RNPs along with ssDNA oligonucleotide repair templates that can generate mutations in up to 98% of single cell clones and introduce single nucleotide changes at an efficiency of up to 40%. We describe our use of a T7 endonuclease assay to identify active guide RNAs, and a high-throughput sequencing genotyping strategy that allows the identification of correctly edited clones. We also present our experiences of generating single nucleotide changes at 15 sites, which show considerable variability between both guides and target sites in the efficiency at which such changes can be introduced.

Generation of functional cardiomyocytes from rat embryonic and induced pluripotent stem cells using feeder-free expansion and differentiation in suspension culture

The possibility to generate cardiomyocytes from pluripotent stem cells in vitro has enormous significance for basic research, disease modeling, drug development and heart repair. The concept of heart muscle reconstruction has been studied and optimized in the rat model using rat primary cardiovascular cells or xenogeneic pluripotent stem cell derived-cardiomyocytes for years. However, the lack of rat pluripotent stem cells (rPSCs) and their cardiovascular derivatives prevented the establishment of an authentic clinically relevant syngeneic or allogeneic rat heart regeneration model. In this study, we comparatively explored the potential of recently available rat embryonic stem cells (rESCs) and induced pluripotent stem cells (riPSCs) as a source for cardiomyocytes (CMs). We developed feeder cell-free culture conditions facilitating the expansion of undifferentiated rPSCs and initiated cardiac differentiation by embryoid body (EB)-formation in agarose microwell arrays, which substituted the robust but labor-intensive hanging drop (HD) method. Ascorbic acid was identified as an efficient enhancer of cardiac differentiation in both rPSC types by significantly increasing the number of beating EBs (3.6 ± 1.6-fold for rESCs and 17.6 ± 3.2-fold for riPSCs). These optimizations resulted in a differentiation efficiency of up to 20% cTnT^pos rPSC-derived CMs. CMs showed spontaneous contractions, expressed cardiac markers and had typical morphological features. Electrophysiology of riPSC-CMs revealed different cardiac subtypes and physiological responses to cardio-active drugs. In conclusion, we describe rPSCs as a robust source of CMs, which is a prerequisite for detailed preclinical studies of myocardial reconstruction in a physiologically and immunologically relevant small animal model.

Delivery of proteases in aqueous two-phase systems enables direct purification of stem cell colonies from feeder cell co-cultures for differentiation into functional cardiomyocytes

Patterning of bioactive enzymes with subcellular resolution is achieved by dispensing droplets of dextran (DEX) onto polyethylene glycol (PEG)-covered cells though a glass capillary needle connected to a pneumatic pump. This technique is applied to purify colonies of induced pluripotent stem cells (iPSCs) from mouse embryonic fibroblast (MEF) feeder cultures and inefficiently induced iPSC colonies by selectively dissociating the iPSCs with proteases.

Genetic and epigenetic instability in human pluripotent stem cells

BACKGROUND

There is an increasing body of evidence that human pluripotent stem cells (hPSCs) are prone to (epi)genetic instability during in vitro culture. This review aims at giving a comprehensive overview of the current knowledge on culture-induced (epi)genetic alterations in hPSCs and their phenotypic consequences.

METHODS

Combinations of the following key words were applied as search criteria: human induced pluripotent stem cells and human embryonic stem cells in combination with malignancy, tumorigenicity, X inactivation, mitochondrial mutations, genomic integrity, chromosomal abnormalities, culture adaptation, aneuploidy and CD30. Only studies in English, on hPSCs and focused on (epi)genomic integrity were included. Further manuscripts were added from cross-references.

RESULTS

Numerous (epi)genetic aberrations have been detected in hPSCs. Recurrent genetic alterations give a selective advantage in culture to the altered cells leading to overgrowth of abnormal, culture-adapted cells. The functional effects of these alterations are not yet fully understood, but suggest a (pre)malignant transformation of abnormal cells with decreased differentiation and increased proliferative capacity.

CONCLUSIONS

Given the high degree of (epi)genetic alterations reported in the literature and altered phenotypic characteristics of the abnormal cells, controlling for the (epi)genetic integrity of hPSCs before any clinical application is an absolute necessity.

Comprehensive characterization of genomic instability in pluripotent stem cells and their derived neuroprogenitor cell lines

The genomic integrity of two human pluripotent stem cells and their derived neuroprogenitor cell lines was studied, applying a combination of high-resolution genetic methodologies. The usefulness of combining array-comparative genomic hybridization (aCGH) and multiplex fluorescence in situ hybridization (M-FISH) techniques should be delineated to exclude/detect a maximum of possible genomic structural aberrations. Interestingly, in parts different genomic imbalances at chromosomal and subchromosomal levels were detected in pluripotent stem cells and their derivatives. Some of the copy number variations were inherited from the original cell line, whereas other modifications were presumably acquired during the differentiation and manipulation procedures. These results underline the necessity to study both pluripotent stem cells and their differentiated progeny by as many approaches as possible in order to assess their genomic stability before using them in clinical therapies.

Passaging and colony expansion of human pluripotent stem cells by enzyme-free dissociation in chemically defined culture conditions

This protocol describes an EDTA-based passaging procedure to be used with chemically defined E8 medium that serves as a tool for basic and translational research into human pluripotent stem cells (PSCs). In this protocol, passaging one six-well or 10-cm plate of cells takes about 6-7 min. This enzyme-free protocol achieves maximum cell survival without enzyme neutralization, centrifugation or drug treatment. It also allows for higher throughput, requires minimal material and limits contamination. Here we describe how to produce a consistent E8 medium for routine maintenance and reprogramming and how to incorporate the EDTA-based passaging procedure into human induced PSC (iPSC) derivation, colony expansion, cryopreservation and teratoma formation. This protocol has been successful in routine cell expansion, and efficient for expanding large-volume cultures or a large number of cells with preferential dissociation of PSCs. Effective for all culture stages, this procedure provides a consistent and universal approach to passaging human PSCs in E8 medium.

Derivation of xeno-free and GMP-grade human embryonic stem cells--platforms for future clinical applications

Clinically compliant human embryonic stem cells (hESCs) should be developed in adherence to ethical standards, without risk of contamination by adventitious agents. Here we developed for the first time animal-component free and good manufacturing practice (GMP)-compliant hESCs. After vendor and raw material qualification, we derived xeno-free, GMP-grade feeders from umbilical cord tissue, and utilized them within a novel, xeno-free hESC culture system. We derived and characterized three hESC lines in adherence to regulations for embryo procurement, and good tissue, manufacturing and laboratory practices. To minimize freezing and thawing, we continuously expanded the lines from initial outgrowths and samples were cryopreserved as early stocks and banks. Batch release criteria included DNA-fingerprinting and HLA-typing for identity, characterization of pluripotency-associated marker expression, proliferation, karyotyping and differentiation in-vitro and in-vivo. These hESCs may be valuable for regenerative therapy. The ethical, scientific and regulatory methodology presented here may serve for development of additional clinical-grade hESCs.

Novel developmental biology-based protocol of embryonic stem cell differentiation to morphologically sound and functional yet immature hepatocytes

BACKGROUND/AIMS

Liver diseases are common in the United States and often require liver transplantation; however, donated organs are limited and thus alternative sources for liver cells are in high demand. Embryonic stem cells (ESC) can provide a continuous and readily available source of liver cells. ESC differentiation to liver cells is yet to be fully understood and comprehensive differentiation protocols are yet to be defined. Here, we aimed to achieve human (h)ESC differentiation into mature hepatocytes using defined recombinant differentiation factors and metabolites.

METHODS

Embryonic stem cell H1 line was sub-cultured on feeder layer. We induced hESCs into endodermal differentiation succeeded by early/late hepatic specification and finally into hepatocyte maturation using step combinations of Activin A and fibroblast growth factor (FGF)-2 for 7 days; followed by FGF-4 and bone morphogenic protein 2 (BMP2) for 7 days, succeeded by FGF-10 + hepatocyte growth factor 4 + epidermal growth factor for 14 days. Specific inhibitors/stimulators were added sequentially throughout differentiation. Cells were analysed by PCR, flow cytometry, microscopy or functional assays.

RESULTS

Our hESC differentiation protocol resulted in viable cells with hepatocyte shape and morphology. We observed gradual changes in cell transcriptome, including up-regulation of differentiation-promoting GATA4, GATA6, POU5F1 and HNF4 transcription factors, steady levels of stemness-promoting SOX-2 and low levels of Nanog, as defined by PCR. The hESC-derived hepatocytes expressed alpha-antitrypsin, CD81, cytokeratin 8 and low density lipoprotein (LDL) receptor. The levels of alpha-fetoprotein and proliferation marker Ki-67 in hESC-derived hepatocytes remained elevated. Unlike stem cells, the hESC-derived hepatocytes performed LDL uptake, produced albumin and alanine aminotransferase and had functional alcohol dehydrogenase.

CONCLUSION

We report a novel protocol for hESC differentiation into morphological and functional yet immature hepatocytes as an alternative method for hepatocyte generation.

Stem cell banks: preserving cell lines, maintaining genetic integrity, and advancing research

The ability to cryopreserve and successfully recover cell lines has been critical to the conservation of all cell lines, especially the preservation of pristine early-stage cultures and the preparation of well-characterized cell banks. Indeed, the systematic storage and establishment of cryopreserved banks of cells for the stem cell research community is fundamental to the promotion of standardisation in stem cell research and their use in clinical applications. In spite of the significant potential for the use of stem cells in research and therapy, they are challenging to maintain and have been shown to be unstable after prolonged culture that often results in permanent alterations in their genetic make-up, which ultimately alters the phenotype of the culture. This chapter will review the principles of cell bank production, techniques for the scale-up of human pluripotent stem cells, quality control, and characterisation methods for banked cell lines.

Expansion of human embryonic stem cells: a comparative study

OBJECTIVES

Human embryonic stem cells (hESC) are promising for tissue engineering (TE) purposes due to their unique properties. However, current standard mechanical passaging techniques limit rates of possible TE experiments, as it is difficult to obtain high enough numbers of the cells for experimentation. In this study, several dissociative solutions and application methods are tested for their applicability to, and influence on, hESC culture and expansion.

MATERIALS AND METHODS

Expansion of two hESC lines, H1 and VUB01, subjected to different passaging techniques, was evaluated. Four dissociative solutions - TrypLE™ Express, Trypsin-EDTA, Cell Dissociation Solution and Accutase™- were combined with two application protocols. As reference conditions, manual and bead-based passaging techniques were used.

RESULTS

Results showed that use of Cell Dissociation Solution in combination with a slow adaptation protocol, generated the best expansion profile for both cell lines. The hESC single cell lines remained pluripotent, had good expansion profiles and were capable of differentiation into representatives of all three germ layers. Reproducibility of the results was confirmed by adaptation for three other hESC lines.

CONCLUSION

Use of Cell Dissociation Solution, combined with slow adaptation protocol, allows a fast switch from the mechanical passaging technique to a single-cell split technique, generating stable and robust hESC cell lines, which allow for large scale expansion of hESC for TE purposes.

Ascorbate promotes epigenetic activation of CD30 in human embryonic stem cells

Human embryonic stem cells (hESCs) and induced pluripotent stem cells have the ability to adapt to various culture conditions. Phenotypic and epigenetic changes brought about by the culture conditions can, however, have significant impacts on their use in research and in clinical applications. Here, we show that diploid hESCs start to express CD30, a biomarker for malignant cells in Hodgkin's disease and embryonal carcinoma cells, when cultured in knockout serum replacement (KOSR)-based medium, but not in fetal calf serum containing medium. We identify the commonly used medium additive, ascorbate, as the sole medium component in KOSR responsible for CD30 induction. Our data show that this epigenetic activation of CD30 expression in hESCs by ascorbate occurs through a dramatic loss of DNA methylation of a CpG island in the CD30 promoter. Analysis of the phenotype and transcriptome of hESCs that overexpress the CD30 signaling domain reveals that CD30 signaling leads to inhibition of apoptosis, enhanced single-cell growth, and transcriptome changes that are associated with cell signaling, lipid metabolism, and tissue development. Collectively, our data show that hESC culture media that contain ascorbate trigger CD30 expression through an epigenetic mechanism and that this provides a survival advantage and transcriptome changes that may help adapt hESCs to in vitro culture conditions.

Embryonic and embryonic-like stem cells in heart muscle engineering

Cardiac muscle engineering is evolving rapidly and may ultimately be exploited to (1) model cardiac development, physiology, and pathology; (2) identify and validate drug targets; (3) assess drug safety and efficacy; and (4) provide therapeutic substitute myocardium. The ultimate success in any of these envisioned applications depends on the utility of human cells and their assembly into myocardial equivalents with structural and functional properties of mature heart muscle. Embryonic stem cells appear as a promising cell source in this respect, because they can be cultured reliably and differentiated robustly into cardiomyocytes. Despite their unambiguous cardiogenicity, data on advanced maturation and seamless myocardial integration of embryonic stem cell-derived cardiomyocytes in vivo are sparse. Additional concerns relate to the limited control over cardiomyogenic specification and cardiomyocyte maturation in vitro as well as the risk of teratocarcinoma formation and immune rejection of stem cell implants in vivo. Through the invent of embryonic-like stem cells - such as parthenogenetic stem cells, male germline stem cells, and induced pluripotent stem cells - some but certainly not all of these issues may be addressed, albeit at the expense of additional concerns. This review will discuss the applicability of embryonic and embryonic-like stem cells in myocardial tissue engineering and address issues that require particular attention before the potential of stem cell-based heart muscle engineering may be fully exploited. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

Human cystic fibrosis embryonic stem cell lines derived on placental mesenchymal stromal cells

This study describes the production of two new human embryonic stem cell (hESC) lines affected by cystic fibrosis. These cell lines are heterozygous compounds, each a carrier of the DF508 mutations associated either with E585X or with 3849+10 kb C-->T. The derivation process was performed on irradiated human placental mesenchymal stromal cells and designed to minimize contact with xeno-components. This new source of feeder cells is easy to obtain and devoid of ethical concerns. The cells have a great capacity to proliferate which reduces the need for continuous preparation of new feeder cell lines. In addition, three normal hESC lines were obtained in the same conditions. The five stem cell lines retained hESC-specific features, including an unlimited and undifferentiated proliferation capacity, marker expression and the maintenance of stable karyotype. They also demonstrated pluripotency in vitro, forming cell lineages of the three germ layers, as indicated by immunolocalization of beta-tubulin, alpha-fetoprotein and actin. These new genetic cell lines represent an important in-vitro tool to study the physiological processes underlying this genetic disease, drug screening, and tissue engineering.

Stem cells for ischemic brain injury: a critical review

No effective therapy is currently available to promote recovery following ischemic stroke. Stem cells have been proposed as a potential source of new cells to replace those lost due to central nervous system injury, as well as a source of trophic molecules to minimize damage and promote recovery. We undertook a detailed review of data from recent basic science and preclinical studies to investigate the potential application of endogenous and exogenous stem cell therapies for treatment of cerebral ischemia. To date, spontaneous endogenous neurogenesis has been observed in response to ischemic injury, and can be enhanced via infusion of appropriate cytokines. Exogenous stem cells from multiple sources can generate neural cells that survive and form synaptic connections after transplantation in the stroke-injured brain. Stem cells from multiple sources cells also exhibit neuroprotective properties that may ameliorate stroke deficits. In many cases, functional benefits observed are likely independent of neural differentiation, although the exact mechanisms remain poorly understood. Future studies of neuroregeneration will require the demonstration of function in endogenously born neurons following focal ischemia. Further, methods are currently lacking to demonstrate definitively the therapeutic effect of newly introduced neural cells. Increased plasticity following stroke may facilitate the functional integration of new neurons, but the loss of appropriate guidance cues and supporting architecture in the infarct cavity will likely impede the restoration of lost circuitry. Thus careful investigation of the mechanisms underlying trophic benefits will be essential. Evidence to date suggests that continued development of stem cell therapies may ultimately lead to viable treatment options for ischemic brain injury.

Characterization of CD30 expression in human embryonic stem cell lines cultured in serum-free media and passaged mechanically

BACKGROUND

The presence of chromosomal abnormalities could have a negative impact for human embryonic stem cell (hESC) applications both in regenerative medicine and in research. A biomarker that allows the identification of chromosomal abnormalities induced in hESC in culture before they take over the culture would represent an important tool for defining optimal culture conditions for hESC. Here we investigate the expression of CD30, reported to be a biomarker of hESCs with abnormal karyotype, in undifferentiated and spontaneously differentiated hESC.

METHODS AND RESULTS

hESC were derived and cultured on mouse fibroblasts in KO-SR containing medium (serum free media) and passaged mechanically. Our results based on analysis at mRNA (RT-PCR) and protein (fluorescence-activated cell sorting and immunocytochemistry) level show that CD30 is expressed in undifferentiated hESC, even at very early passages, without any correlation with the presence of chromosomal anomalies. We also show that the expression of CD30 is rapidly lost during early spontaneous differentiation of hESC.

CONCLUSION

We conclude that CD30 expression in hESC cultures is probably a consequence of culture conditions, and that KO-SR may play a role. In addition, the expression of so-called 'stemness' markers does not change in undifferentiated hESC during long-term culture or when cells acquire chromosomal abnormalities.

Large scale production of stem cells and their derivatives

Stem cells have been envisioned to become an unlimited cell source for regenerative medicine. Notably, the interest in stem cells lies beyond direct therapeutic applications. They might also provide a previously unavailable source of valuable human cell types for screening platforms, which might facilitate the development of more efficient and safer drugs. The heterogeneity of stem cell types as well as the numerous areas of application suggests that differential processes are mandatory for their in vitro culture. Many of the envisioned applications would require the production of a high number of stem cells and their derivatives in scalable, well-defined and potentially clinical compliant manner under current good manufacturing practice (cGMP). In this review we provide an overview on recent strategies to develop bioprocesses for the expansion, differentiation and enrichment of stem cells and their progenies, presenting examples for adult and embryonic stem cells alike.

Human embryonic stem cells and lung regeneration

Human embryonic stem cells are pluripotent cells derived from the inner cell mass of preimplantation stage embryos. Their unique potential to give rise to all differentiated cell types has generated great interest in stem cell research and the potential that it may have in developmental biology, medicine and pharmacology. The main focus of stem cell research has been on cell therapy for pathological conditions with no current methods of treatment, such as neurodegenerative diseases, cardiac pathology, retinal dysfunction and lung and liver disease. The overall aim is to develop methods of application either of pure cell populations or of whole tissue parts to the diseased organ under investigation. In the field of pulmonary research, studies using human embryonic stem cells have succeeded in generating enriched cultures of type II pneumocytes in vitro. On account of their potential of indefinite proliferation in vitro, embryonic stem cells could be a source of an unlimited supply of cells available for transplantation and for use in gene therapy. Uncovering the ability to generate such cell types will expand our understanding of biological processes to such a degree that disease understanding and management could change dramatically.