Laser-assisted blastocyst dissection and subsequent cultivation of embryonic stem cells in a serum/cell free culture system: applications and preliminary results in a murine model

Human Pluripotent Stem Cells in Neurodegenerative Diseases: Potentials, Advances and Limitations

Neurodegenerative diseases are progressive and uncontrolled gradual loss of motor neurons function or death of neuron cells in the central nervous system (CNS) and the mechanisms underlying their progressive nature remain elusive. There is urgent need to investigate therapeutic strategies and novel treatments for neural regeneration in disorders like Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). Currently, the development and identification of pluripotent stem cells enabling the acquisition of a large number of neural cells in order to improve cell recovery after neurodegenerative disorders. Pluripotent stem cells which consist of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are characterized by their ability to indefinitely self-renew and the capacity to differentiate into different types of cells. The first human ESC lines were established from donated human embryos; while, because of a limited supply of donor embryos, human ESCs derivation remains ethically and politically controversial. Hence, hiPSCs-based therapies have been shown as an effective replacement for human ESCs without embryo destruction. Compared to the invasive methods for derivation of human ESCs, human iPSCs has opened possible to reprogram patient-specific cells by defined factors and with minimally invasive procedures. Human pluripotent stem cells are a good source for cell-based research, cell replacement therapies and disease modeling. To date, hundreds of human ESC and human iPSC lines have been generated with the aim of treating various neurodegenerative diseases. In this review, we have highlighted the recent potentials, advances, and limitations of human pluripotent stem cells for the treatment of neurodegenerative disorders.

Derivation of new human embryonic stem cell lines (Yazd1-3) and their vitrification using Cryotech and Cryowin tools: A lab resources report

Background

Cell banking of initial outgrowths from newly derived human embryonic stem cells (hESCs) requires an efficient freezing method. Vitrification is used for the preservation of gametes and early embryos in assisted reproduction techniques (ART). Moreover, vitrification was applied for cryopreservation of hESCs using open pulled straws.

Objective

To derive and characterize new hESC lines and then use Cryotech and Cryowin tools for their vitrification.

Materials and Methods

Human ESC lines were generated in a microdrop culture system using mouse embryonic fibroblasts (MEFs) as the feeder layer; this was later scaled up using both MEFs and Yazd human foreskin fibroblasts batch 8 (YhFF#8). To bank the cell lines, master cell banks of 100 Cryotech and Cryowin tools were produced for each individual cell line using the vitrification method; flasks of hESC lines were also cryopreserved using a conventional slow-freezing method.

Results

The pluripotency of cell lines was assessed by their expression of pluripotency-associated genes (OCT4/POU5F1, NANOG, and SOX2) and markers such as SSEA4, TRA-1-60, and TRA-2-49. Their in vitro capacity to differentiate into germ layers and germ cells using embryoid body (EB) formation and monolayer culture was assessed by screening the expression of differentiation-associated genes. The chromosomal constitution of each hESC line was assessed by G-banding karyotyping.

Conclusion

Cryotech and Cryowin tools used to vitrify new hESCs at an early stage of derivation is an efficient method of preserving hESCs.

Versatile cell ablation tools and their applications to study loss of cell functions

Targeted cell ablation is a powerful approach for studying the role of specific cell populations in a variety of organotypic functions, including cell differentiation, and organ generation and regeneration. Emerging tools for permanently or conditionally ablating targeted cell populations and transiently inhibiting neuronal activities exhibit a diversity of application and utility. Each tool has distinct features, and none can be universally applied to study different cell types in various tissue compartments. Although these tools have been developed for over 30 years, they require additional improvement. Currently, there is no consensus on how to select the tools to answer the specific scientific questions of interest. Selecting the appropriate cell ablation technique to study the function of a targeted cell population is less straightforward than selecting the method to study a gene's functions. In this review, we discuss the features of the various tools for targeted cell ablation and provide recommendations for optimal application of specific approaches.

Allele-specific RNA-seq expression profiling of imprinted genes in mouse isogenic pluripotent states

BACKGROUND

Genomic imprinting, resulting in parent-of-origin specific gene expression, plays a critical role in mammalian development. Here, we apply allele-specific RNA-seq on isogenic B6D2F1 mice to assay imprinted genes in tissues from early embryonic tissues between E3.5 and E7.25 and in pluripotent cell lines to evaluate maintenance of imprinted gene expression. For the cell lines, we include embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs) derived from fertilized embryos and from embryos obtained after nuclear transfer (NT) or parthenogenetic activation (PGA).

RESULTS

As homozygous genomic regions of PGA-derived cells are not compatible with allele-specific RNA-seq, we developed an RNA-seq-based genotyping strategy allowing identification of informative heterozygous regions. Global analysis shows that proper imprinted gene expression as observed in embryonic tissues is largely lost in the ESC lines included in this study, which mainly consisted of female ESCs. Differentiation of ESC lines to embryoid bodies or NPCs does not restore monoallelic expression of imprinted genes, neither did reprogramming of the serum-cultured ESCs to the pluripotent ground state by the use of 2 kinase inhibitors. Fertilized EpiSC and EpiSC-NT lines largely maintain imprinted gene expression, as did EpiSC-PGA lines that show known paternally expressed genes being silent and known maternally expressed genes consistently showing doubled expression. Notably, two EpiSC-NT lines show aberrant silencing of Rian and Meg3, two critically imprinted genes in mouse iPSCs. With respect to female EpiSC, most of the lines displayed completely skewed X inactivation suggesting a (near) clonal origin.

CONCLUSIONS

Altogether, our analysis provides a comprehensive overview of imprinted gene expression in pluripotency and provides a benchmark to allow identification of cell lines that faithfully maintain imprinted gene expression and therefore retain full developmental potential.

Laser-assisted Lentiviral Gene Delivery to Mouse Fertilized Eggs

Lentiviruses are efficient vectors for gene delivery to mammalian cells. Following transduction, the lentiviral genome is stably incorporated into the host chromosome and is passed on to progeny. Thus, they are ideal vectors for creation of stable cell lines, in vivo delivery of indicators, and transduction of single cell fertilized eggs to create transgenic animals. However, mouse fertilized eggs and early stage embryos are protected by the zona pellucida, a glycoprotein matrix that forms a barrier against lentiviral gene delivery. Lentiviruses are too large to penetrate the zona and are typically delivered by microinjection of viral particles into the perivitelline cavity, the space between the zona and the embryonic cells. The requirement for highly skilled technologists and specialized equipment has minimized the use of lentiviruses for gene delivery to mouse embryos. This article describes a protocol for permeabilizing the mouse fertilized eggs by perforating the zona with a laser. Laser-perforation does not result in any damage to embryos and allows lentiviruses to gain access to embryonic cells for gene delivery. Transduced embryos can develop into blastocyst in vitro, and if implanted in pseudopregnant mice, develop into transgenic pups. The laser used in this protocol is effective and easy to use. Genes delivered by lentiviruses stably incorporate into mouse embryonic cells and are germline transmittable. This is an alternative method for creation of transgenic mice that requires no micromanipulation and microinjection of fertilized eggs.

Isolation, Culture, and Functional Characterization of Human Embryonic Stem Cells: Current Trends and Challenges

Human embryonic stem cells (hESCs) hold great potential for the treatment of various degenerative diseases. Pluripotent hESCs have a great ability to undergo unlimited self-renewal in culture and to differentiate into all cell types in the body. The journey of hESC research is not that smooth, as it has faced several challenges which are limited to not only tumor formation and immunorejection but also social, ethical, and political aspects. The isolation of hESCs from the human embryo is considered highly objectionable as it requires the destruction of the human embryo. The issue was debated and discussed in both public and government platforms, which led to banning of hESC research in many countries around the world. The banning has negatively affected the progress of hESC research as many federal governments around the world stopped research funding. Afterward, some countries lifted the ban and allowed the funding in hESC research, but the damage has already been done on the progress of research. Under these unfavorable conditions, still some progress was made to isolate, culture, and characterize hESCs using different strategies. In this review, we have summarized various strategies used to successfully isolate, culture, and characterize hESCs. Finally, hESCs hold a great promise for clinical applications with proper strategies to minimize the teratoma formation and immunorejection and better cell transplantation strategies.

Current advanced therapy cell-based medicinal products for type-1-diabetes treatment

In the XXI century diabetes mellitus has become one of the main threats to human health with higher incidence in regions such as Europe and North America. Type 1 diabetes mellitus (T1DM) occurs as a consequence of the immune-mediated destruction of insulin producing β-cells located in the endocrine part of the pancreas, the islets of Langerhans. The administration of exogenous insulin through daily injections is the most prominent treatment for T1DM but its administration is frequently associated to failure in glucose metabolism control, finally leading to hyperglycemia episodes. Other approaches have been developed in the past decades, such as whole pancreas and islet allotransplantation, but they are restricted to patients who exhibit frequent episodes of hypoglycemia or renal failure because the lack of donors and islet survival. Moreover, patients transplanted with either whole pancreas or islets require of immune suppression to avoid the rejection of the transplant. Currently, advanced therapy medicinal products (ATMP), such as implantable devices, have been developed in order to reduce immune rejection response while increasing cell survival. To overcome these issues, ATMPs must promote vascularization, guaranteeing the nutritional contribution, while providing O₂ until vasculature can surround the device. Moreover, it should help in the immune-protection to avoid acute and chronic rejection. The transplanted cells or islets should be embedded within biomaterials with tunable properties like injectability, stiffness and porosity mimicking natural ECM structural characteristics. And finally, an infinitive cell source that solves the donor scarcity should be found such as insulin producing cells derived from mesenchymal stem cells (MSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Several companies have registered their ATMPs and future studies envision new prototypes. In this review, we will discuss the mechanisms and etiology of diabetes, comparing the clinical trials in the last decades in order to define the main characteristics for future ATMPs.

Inappropriate cadherin switching in the mouse epiblast compromises proper signaling between the epiblast and the extraembryonic ectoderm during gastrulation

Cadherin switching from E-cadherin (E-cad) to N-cadherin (N-cad) is a key step of the epithelial-mesenchymal transition (EMT) processes that occurs during gastrulation and cancer progression. We investigate whether cadherins actively participate in progression of EMT by crosstalk to signaling pathways. We apply ectopic cadherin switching before the onset of mouse gastrulation. Mutants with an induced E-cad to N-cad switch (Ncadki) die around E8.5. Severe morphological changes including a small epiblast, a rounded shape, an enlarged extra-embryonic compartment and lack of the amnion, combined with a massive cell detachment from the ectodermal layer are detected. In contrast to epiblast-specific E-cad depletion, gastrulation is initiated in Ncadki embryos, but patterning of the germ-layers is abnormal. An overall reduction in BMP signaling, expansion of Nodal and Eomes domains, combined with reduced Wnt3a expression at the primitive streak is observed. Our results show that in addition to cadherin-dependent adhesion, proper embryonic development requires E-cad mediated signaling function to facilitate a feedback loop that stabilizes Bmp4 and Bmp2 expression in the extraembryonic ectoderm and sustained downstream activity in the epiblast. Moreover, for proper morphogenesis a fine-tuned spatio-temporal control of cadherin switching is required during EMT at gastrulation to avoid premature cell detachment and migration.

Human embryonic stem cell cultivation: historical perspective and evolution of xeno-free culture systems

Human embryonic stem cells (hESC) have emerged as attractive candidates for cell-based therapies that are capable of restoring lost cell and tissue function. These unique cells are able to self-renew indefinitely and have the capacity to differentiate in to all three germ layers (ectoderm, endoderm and mesoderm). Harnessing the power of these pluripotent stem cells could potentially offer new therapeutic treatment options for a variety of medical conditions. Since the initial derivation of hESC lines in 1998, tremendous headway has been made in better understanding stem cell biology and culture requirements for maintenance of pluripotency. The approval of the first clinical trials of hESC cells for treatment of spinal cord injury and macular degeneration in 2010 marked the beginning of a new era in regenerative medicine. Yet it was clearly recognized that the clinical utility of hESC transplantation was still limited by several challenges. One of the most immediate issues has been the exposure of stem cells to animal pathogens, during hESC derivation and during in vitro propagation. Initial culture protocols used co-culture with inactivated mouse fibroblast feeder (MEF) or human feeder layers with fetal bovine serum or alternatively serum replacement proteins to support stem cell proliferation. Most hESC lines currently in use have been exposed to animal products, thus carrying the risk of xeno-transmitted infections and immune reaction. This mini review provides a historic perspective on human embryonic stem cell culture and the evolution of new culture models. We highlight the challenges and advances being made towards the development of xeno-free culture systems suitable for therapeutic applications.

Ultrastructural characteristics of three undifferentiated mouse embryonic stem cell lines and their differentiated three-dimensional derivatives: a comparative study

The fine structures of mouse embryonic stem cells (mESCs) grown as colonies and differentiated in three-dimensional (3D) culture as embryoid bodies (EBs) were analyzed by transmission electron microscopy. Undifferentiated mESCs expressed markers that proved their pluripotency. Differentiated EBs expressed different differentiation marker proteins from the three germ layers. The ultrastructure of mESCs revealed the presence of microvilli on the cell surfaces, large and deep infolded nuclei, low cytoplasm-to-nuclear ratios, frequent lipid droplets, nonprominent Golgi apparatus, and smooth endoplasmic reticulum. In addition, we found prominent juvenile mitochondria and free ribosomes-rich cytoplasm in mESCs. Ultrastructure of the differentiated mESCs as EBs showed different cell arrangements, which indicate the different stages of EB development and differentiation. The morphologies of BALB/c and 129 W9.5 EBs were very similar at day 4, whereas C57BL/6 EBs were distinct from the others at day 4. This finding suggested that differentiation of EBs from different cell lines occurs in the same pattern but not at the same rate. Conversely, the ultrastructure results of BALB/c and 129 W9.5 ESCs revealed differentiating features, such as the dilated profile of a rough endoplasmic reticulum. In addition, we found low expression levels of undifferentiated markers on the outer cells of BALB/c and 129 W9.5 mESC colonies, which suggests a faster differentiation potential.

A simple and effective method for the isolation of inner cell mass samples from human blastocysts for gene expression analysis

The isolation of pure inner cell mass (ICM) and trophectoderm (TE) cells from a single human blastocyst is necessary to obtain accurate gene expression patterns of these cells, which will aid in the understanding of the primary steps of embryo differentiation. However, previously developed pure ICM isolation methods are either time-consuming or alter the normal gene expression patterns of these cells. Here, we demonstrate a simple and effective method of ICM samples isolation from human blastocysts. In total, 35 human blastocysts of all stages with expanded and good morphology were incubated in calcium/magnesium-free HEPES medium for 5 min before micromanipulation. With the aid of a laser, a biopsy pipette was inserted directly into the blastocoel for the suction-based removal of ICM samples. The ICM samples were obtained through simple mechanical pulling force or laser assistance, and each isolation process required 3-4 min. The isolated ICM and TE fractions were subjected to single-cell real-time quantitative RT-PCR to evaluate keratin 18 (KRT18) expression. Finally, 33 paired ICM and TE samples were verified using gene expression analysis. KRT18 was readily detectable in all TE cells but absent in 30 ICM counterparts, indicating a pure ICM isolation rate of 90.9% (30/33). The relative KRT18 expression of three TE samples compared with their three contaminated ICM counterparts was 19-fold (P < 0.001), indicating that the contamination was very weak. These results demonstrate that our ICM isolation method is simple and effective.

Laser-mediated cell ablation during post-implantation mouse development

BACKGROUND

Laser-mediated cell ablation is a powerful tool that has been used to understand cell fate in a variety of externally developing organisms but has not been used during mammalian post-implantation development.

RESULTS

We describe a method pairing laser ablation with murine embryo culture and establish parameters that can be used to precisely ablate cells in the selected field with minimal disruption to adjacent cells or the underlying cell matrix. Ablation of a large domain of endoderm, followed by ~1 day of culture results in a phenotypically normal embryo and gut tube, indicating that laser ablation is compatible with normal development. We next focused on one of the three precursor populations that have been shown to produce the liver bud. Ablations of a single progenitor domain result in a unilateral delay in the liver bud while the contralateral side is unaffected.

CONCLUSIONS

We demonstrate that laser ablation is a specific and useful technique for studying cell fate in the mouse embryo. This method represents a powerful advance in developmental studies in the mouse and can be used to provide information on the specification of organs, differentiation, cell migration, and vital tissue interactions during development.

Laser capture microdissection for gene expression analysis of specific cell populations in single blastocysts

Laser capture microdissection (LCM) allows for the isolation of small tissue fractions from heterogeneous tissue sections, for downstream genetic or proteomic analysis without contamination by the surrounding tissue. This technique can also be successfully used for the isolation of small tissue fractions from developing embryos, such as expanding blastocysts. However, the small size of early-stage embryos hampers tissue processing prior to LCM. The present protocol describes the application of LCM to isolate specific cell fractions from blastocysts for downstream gene expression analysis with RT-PCR.

The four reprogramming factors and embryonic development in mice

The transcription factors (Oct4, Sox2, c-Myc, and Klf4) play an important role in the generation of induced pluripotent stem cells. These factors are expressed in metaphase II oocytes and embryonic stem cells (ESCs). The mechanisms responsible for the reprogramming of ooplasm during nuclear transfer are expected to be associated with the four factors. Here, we show that different paternal genetic backgrounds are able to influence the in vitro development of parthenogenetic and cloned embryos. Using real- time polymerase chain reaction (PCR) we found that the expression level of Oct4 in oocytes was less than that of ESCs, whereas oocytes from KM x C3H females showed the highest expression level of Sox2 than the other strains tested or in G1 ESCs. c-Myc mRNA levels in oocytes from KM mice were greater than those found in ESCs or oocytes of KM x C3H mice. These data demonstrate that the expression of the four transcription factors was different among the oocytes, which may be a contributing factor for the different efficiencies of parthenogenesis and the development of cloned embryos in vitro.

Derivation and characterization of novel nonhuman primate embryonic stem cell lines from in vitro-fertilized baboon preimplantation embryos

The development of nonhuman primate (NHP) embryonic stem cell (ESC) models holds great promise for cell-mediated treatment of debilitating diseases and to address numerous unanswered questions regarding the therapeutic efficacy of ESCs while supplanting ethical considerations involved with human studies. Here we report successful establishment and characterization of 3 novel baboon (Papio cynocephalus) ESC lines from the inner cell mass of intracytoplasmic sperm injection-derived blastocysts. Embryos were cultured in an improved baboon embryo in vitro culture protocol. The inner cell mass of blastocyst was laser-dissected and plated on mouse embryonic fibroblast feeder cell monolayer in the NHP ESC culture medium. Three cell lines with characteristic ESC morphology have been cultured through an extended period (>14 months), with 2 male cell lines (UT-1 and -2) and 1 female cell line (UT-3) displaying normal baboon karyotypes. Reverse transcription-polymerase chain reaction analysis confirmed that all 3 lines express primate ESC pluripotency markers, including OCT-4, NANOG, SOX-2, TERT, TDGF, LEFTYA, and REX-1. All 3 lines demonstrated positive immunocytochemical staining for OCT-4, stage-specific embryonic antigen-3, stage-specific embryonic antigen-4, TRA-1-60, and TRA-1-81. Baboon ESCs injected into NOD/SCID mice formed teratomas with all 3 germ layers. In addition, embryoid body-like spherical structures were derived and initial outgrowth was observed when embedded into extracellular matrix Matrigel. The ESC lines established in this NHP model have the potential to extend our knowledge in the fields of developmental biology, regenerative medicine, and future applications, including preclinical safety assessment of in vivo stem cell therapy.

Generation of Sheffield (Shef) human embryonic stem cell lines using a microdrop culture system

The conventional method for the derivation of human embryonic stem cells (hESCs) involves inner cell mass (ICM) co-culture with a feeder layer of inactivated mouse or human embryonic fibroblasts in an in vitro fertilisation culture dish. Growth factors potentially involved in primary derivation of hESCs may be lost or diluted in such a system. We established a microdrop method which maintained feeder cells and efficiently generated hESCs. Embryos were donated for stem cell research after fully informed patient consent. A feeder cell layer was made by incubating inactivated mouse embryonic fibroblasts (MEFs) feeder cells in a 50 microl drop of medium (DMEM/10% foetal calf serum) under mineral oil in a small tissue culture dish. MEFs formed a confluent layer and medium was replaced with human embryonic stem medium supplemented with 10% Plasmanate (Bayer) and incubated overnight. Cryopreserved embryos were thawed and cultured until the blastocyst stage and the zona pellucida removed with pronase (2 mg/ml; Calbiochem). A zona-free intact blastocyst was placed in the feeder microdrop and monitored for ES derivation with medium changed every 2-3 d. Proliferating hESCs were passaged into other feeder drops and standard feeder preparation by manual dissection until a stable cell line was established. Six hESC lines (Shef 3-8) were derived. From a total of 46 blastocysts (early to expanded), five hESC lines were generated (Shef 3-7). Shef 3-6 were generated on MEFs from 25 blastocysts. Shef7 was generated on human foetal gonadal embryonic fibroblasts from a further 21 blastocysts. From our experience, microdrop technique is more efficient than conventional method for derivation of hESCs and it is much easier to monitor early hESC derivation. The microdrop method lends itself to good manufacturing practice derivation of hESCs.

Promoter analysis of the rabbit POU5F1 gene and its expression in preimplantation stage embryos

BACKGROUND

The POU5F1 gene encodes the octamer-binding transcription factor-4 (Oct4). It is crucial in the regulation of pluripotency during embryonic development and widely used as molecular marker of embryonic stem cells (ESCs). The objective of this study was to identify and to analyse the promoter region of rabbit POU5F1 gene; furthermore to examine its expression pattern in preimplantation stage rabbit embryos.

RESULTS

The upstream region of rabbit POU5F1 was subcloned sequenced and four highly conserved promoter regions (CR1-4) were identified. The highest degree of similarity on sequence level was found among the conserved domains between rabbit and human. Among the enhancers the proximal enhancer region (PE-1A) exhibited the highest degree of homology (96.4%). Furthermore, the CR4 regulator domain containing the distal enhancer (DE-2A) was responsible for stem cell-specific expression. Also, BAC library screen revealed the existence of a processed pseudogene of rabbit POU5F1. The results of quantitative real-time PCR experiments showed that POU5F1 mRNA was abundantly present in oocytes and zygotes, but it was gradually reduced until the activation of the embryonic genome, thereafter a continuous increase in POU5F1 mRNA level was observed until blastocyst stage. By using the XYClone laser system the inner cell mass (ICM) and trophoblast portions of embryos were microdissected and examined separately and POU5F1 mRNA was detected in both cell types.

CONCLUSION

In this study we provide a comparative sequence analysis of the regulatory region of rabbit POU5F1 gene. Our data suggest that the POU5F1 gene is strictly regulated during early mammalian development. We proposed that the well conserved CR4 region containing the DE-2A enhancer is responsible for the highly conserved ESC specific gene expression. Notably, we are the first to report that the rabbit POU5F1 is not restricted to ICM cells only, but it is expressed in trophoblast cells as well. This information may be well applicable to investigate further the possible phylogenetic role and the regulation of POU5F1 gene.

Challenges and approaches to the culture of pluripotent human embryonic stem cells

Since the establishment of the first human embryonic stem cell (hESC) lines, several groups have described the derivation and culture of hESC lines in various culture conditions. In this review, we describe how hESC lines have been derived from the inner cell mass of blastocysts or morula-stage embryos and the culture conditions used. In order to be used for therapeutic purposes, the pluripotent hESC lines must be established and propagated according to good manufacturing practice quality requirements. In addition, any use of animal-derived components should be avoided to gain safer hESC lines for clinical purposes. Here, we will describe the development in derivation and chemically defined culturing conditions of hESC towards good manufacturing practice and discuss the future challenges for hESCs in clinical use. Similarly, we discuss the challenges and future directions in optimization of standard culture conditions of hESCs for research purposes.

Endothelial differentiation of embryonic stem cells

Vascular progenitor cells derived from stem cells could potentially lead to a variety of clinically relevant applications, including cell-based therapies and tissue engineering. Here, we describe methods for isolating purified proliferating populations of vascular endothelial cells from mouse embryonic stem cells (mESC) using Flk-1 positive sorted cells, VEGF supplementation, and a rigorous manual selection technique required for endothelial cell purification and expansion. Using this in vitro derivation procedure, it is possible to obtain millions of cells at various stages of differentiation, with the potential for up to 25 population doublings.

Whole-blastocyst culture followed by laser drilling technology enhances the efficiency of inner cell mass isolation and embryonic stem cell derivation from good- and poor-quality mouse embryos: new insights for derivation of human embryonic stem cell lines

The optimization of human embryonic stem (hES) cell line derivation methods is challenging because many worldwide laboratories have neither access to spare human embryos nor ethical approval for using supernumerary human embryos for hES cell derivation purposes. Additionally, studies performed directly on human embryos imply a waste of precious human biological material. In this study, we developed a new strategy based on the combination of whole-blastocyst culture followed by laser drilling destruction of the trophoectoderm for improving the efficiency of inner cell mass (ICM) isolation and ES cell derivation using murine embryos. Embryos were divided into good- and poor-quality embryos. We demonstrate that the efficiency of both ICM isolation and ES cell derivation using this strategy is significantly superior to whole-blastocyst culture or laser drilling technology itself. Regardless of the ICM isolation method, the ES cell establishment depends on a feeder cell growth surface. Importantly, this combined methodology can be successfully applied to poor-quality blastocysts that otherwise would not be suitable for laser drilling itself nor immunosurgery in an attempt to derive ES cell lines due to the inability to distinguish the ICM. The ES cell lines derived by this combined method were characterized and shown to maintain a typical morphology, undifferentiated phenotype, and in vitro and in vivo three germ layer differentiation potential. Finally, all ES cell lines established using either technology acquired an aneuploid karyotype after extended culture periods, suggesting that the method used for ES cell derivation does not seem to influence the karyotype of the ES cells after extended culture. This methodology may open up new avenues for further improvements for the derivation of hES cells, the majority of which are derived from frozen, poor-quality human embryos.

Shrinky-dink hanging drops: a simple way to form and culture embryoid bodies

Embryoid bodies (EB) are aggregates of embryonic stem cells. The most common way of creating these aggregates is the hanging drop method, a laborious approach of pipetting an arbitrary number of cells into well plates. The interactions between the stem cells forced into close proximity of one another promotes the generation of the EBs. Because the media in each of the wells has to be manually exchanged every day, this approach is manually intensive. Moreover, because environmental parameters including cell-cell, cell-soluble factor interactions, pH, and oxygen availability can be functions of EB size, cell populations obtained from traditional hanging drops can vary dramatically even when cultured under identical conditions. Recent studies have indeed shown that the initial number of cells forming the aggregate can have significant effects on stem cell differentiation. We have developed a simple, rapid, and scalable culture method to load pre-defined numbers of cells into microfabricated wells and maintain them for embryoid body development. Finally, these cells are easily accessible for further analysis and experimentation. This method is amenable to any lab and requires no dedicated equipment. We demonstrate this method by creating embryoid bodies using a red fluorescent mouse cell line (129S6B6-F1).

Xeno-free derivation and culture of human embryonic stem cells: current status, problems and challenges

Human embryonic stem cells (hESC) not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.

Role of the embryology laboratory in the human embryonic stem cell line derivation process

With the introduction of regenerative medicine and cell therapy programmes by means of human embryonic stem cells (hESC), several research centres have begun projects of derivation of hESC lines. In some stem cell banks, such as the Andalusian Stem Cell Bank, the law also permits the creation of these cell lines. Therefore, the recovery of cryopreserved embryos, their culture and the subsequent derivation to hESC lines requires a suitable embryology laboratory and specialized and highly qualified staff. Moreover, new techniques, from therapeutic nuclear transfer, need this type of laboratory and staff, too. Several International Associations have drawn up some guidelines for laboratories where embryos are manipulated and they reflect the physical space, the staff and the equipment needed in these kinds of laboratories. Nevertheless, we can see that these guidelines do not distinguish between IVF laboratories and other laboratories that obtain hESC lines, so it would be convenient to make a distinction. Following these guidelines, we have tried to draw up concurrent aspects applicable to areas of embryology within stem cell banks. So, the design and the specific implementation programmes for these areas and other research centres with this area but which do not use IVF techniques is vital to develop embryonic cell lines in optimum conditions for future therapeutic applications, although maybe it is rather premature to standardize this type of research.

Derivation of human embryonic stem cell lines

Human embryonic stem cells (hESC) are undifferentiated cells derived from an early embryo that can grow in vitro indefinitely, while retaining their capability to differentiate into specialized somatic cell types. Over the last decade there has been great interest in derivation and culture of these cells, as they can potentially provide a supply of readily available differentiated cells and tissues of all types to be used for therapeutic purposes in cell transplantation in humans, as well as for other medical uses such as drug discovery. The source of hESC lines is usually excess human embryos from in vitro fertilization treatments, although novel ways of producing hESCs have been suggested recently. The actual methods of hESC derivation have not changed greatly since the first report by Thomson et al. in 1998 . However, the main emphasis over the last several years has been in finding defined conditions for derivation and culture of hESCs, because to enable the clinical use of hESC for cell transplantation, the use of animal derived biological components is no longer acceptable. For basic research, the aim is to replace even human derived materials with completely defined systems. In this paper we describe methods utilized in our laboratory for hESC derivation and describe two studies conducted in an attempt to improve derivation efficiency and to enable research outcomes to be achieved using fewer embryos.