Nonhuman primate parthenogenetic stem cells

Establishment and characterization of baboon embryonic stem cell lines: an Old World Primate model for regeneration and transplantation research

Here we have developed protocols using the baboon as a complementary alternative Old World Primate to rhesus and other macaques which have severe limitations in their availability. Baboons are not limited as research resources, they are evolutionarily closer to humans, and the multiple generations of pedigreed colonies which display complex human disease phenotypes all support their further optimization as an invaluable primate model. Since neither baboon-assisted reproductive technologies nor baboon embryonic stem cells (ESCs) have been reported, here we describe the first derivations and characterization of baboon ESC lines from IVF-generated blastocysts. Two ESCs lines (BabESC-4 and BabESC-15) display ESC morphology, express pluripotency markers (Oct-4, hTert, Nanog, Sox-2, Rex-1, TRA1-60, TRA1-81), and maintain stable euploid female karyotypes with parentage confirmed independently. They have been grown continuously for >430 and 290 days, respectively. Teratomas from both lines have all three germ layers. Availabilities of these BabESCs represent another important resource for stem cell biologists.

Stem cell-based therapies for spinal cord injury

Spinal cord injury (SCI) results in loss of nervous tissue and consequently loss of motor and sensory function. There is no treatment available that restores the injury-induced loss of function to a degree that an independent life can be guaranteed. Transplantation of stem cells or progenitors may support spinal cord repair. Stem cells are characterized by self-renewal and their ability to become any cell in an organism. Promising results have been obtained in experimental models of SCI. Stem cells can be directed to differentiate into neurons or glia in vitro, which can be used for replacement of neural cells lost after SCI. Neuroprotective and axon regeneration-promoting effects have also been credited to transplanted stem cells. There are still issues related to stem cell transplantation that need to be resolved, including ethical concerns. This paper reviews the current status of stem cell application for spinal cord repair.

Parthenogenesis-derived multipotent stem cells adapted for tissue engineering applications

Embryonic stem cells are envisioned as a viable source of pluripotent cells for use in regenerative medicine applications when donor tissue is not available. However, most current harvest techniques for embryonic stem cells require the destruction of embryos, which has led to significant political and ethical limitations on their usage. Parthenogenesis, the process by which an egg can develop into an embryo in the absence of sperm, may be a potential source of embryonic stem cells that may avoid some of the political and ethical concerns surrounding embryonic stem cells. Here we provide the technical aspects of embryonic stem cell isolation and expansion from the parthenogenetic activation of oocytes. These cells were characterized for their stem-cell properties. In addition, these cells were induced to differentiate to the myogenic, osteogenic, adipogenic, and endothelial lineages, and were able to form muscle-like and bony-like tissue in vivo. Furthermore, parthenogenetic stem cells were able to integrate into injured muscle tissue. Together, these results demonstrate that parthenogenetic stem cells can be successfully isolated and utilized for various tissue engineering applications.

New discoveries on the biology and detection of human chorionic gonadotropin

Human chorionic gonadotropin (hCG) is a glycoprotein hormone comprising 2 subunits, alpha and beta joined non covalently. While similar in structure to luteinizing hormone (LH), hCG exists in multiple hormonal and non-endocrine agents, rather than as a single molecule like LH and the other glycoprotein hormones. These are regular hCG, hyperglycosylated hCG and the free beta-subunit of hyperglycosylated hCG. For 88 years regular hCG has been known as a promoter of corpus luteal progesterone production, even though this function only explains 3 weeks of a full gestations production of regular hCG. Research in recent years has explained the full gestational production by demonstration of critical functions in trophoblast differentiation and in fetal nutrition through myometrial spiral artery angiogenesis. While regular hCG is made by fused villous syncytiotrophoblast cells, extravillous invasive cytotrophoblast cells make the variant hyperglycosylated hCG. This variant is an autocrine factor, acting on extravillous invasive cytotrophoblast cells to initiate and control invasion as occurs at implantation of pregnancy and the establishment of hemochorial placentation, and malignancy as occurs in invasive hydatidiform mole and choriocarcinoma. Hyperglycosylated hCG inhibits apoptosis in extravillous invasive cytotrophoblast cells promoting cell invasion, growth and malignancy. Other non-trophoblastic malignancies retro-differentiate and produce a hyperglycosylated free beta-subunit of hCG (hCG free beta). This has been shown to be an autocrine factor antagonizing apoptosis furthering cancer cell growth and malignancy. New applications have been demonstrated for total hCG measurements and detection of the 3 hCG variants in pregnancy detection, monitoring pregnancy outcome, determining risk for Down syndrome fetus, predicting preeclampsia, detecting pituitary hCG, detecting and managing gestational trophoblastic diseases, diagnosing quiescent gestational trophoblastic disease, diagnosing placental site trophoblastic tumor, managing testicular germ cell malignancies, and monitoring other human malignancies. There are very few molecules with such wide and varying functions as regular hCG and its variants, and very few tests with such a wide spectrum of clinical applications as total hCG.

Embryonic stem cells: isolation, characterization and culture

Embryonic stem cells are pluripotent cells isolated from the mammalian blastocyst. Traditionally, these cells have been derived and cultured with mouse embryonic fibroblast (MEF) supportive layers, which allow their continuous growth in an undifferentiated state. However, for any future industrial or clinical application hESCs should be cultured in reproducible, defined, and xeno-free culture system, where exposure to animal pathogens is prevented. From their derivation in 1998 the methods for culturing hESCs were significantly improved. This chapter wills discuss hESC characterization and the basic methods for their derivation and maintenance.

State-of-the-art technologies, current opinions and developments, and novel findings: news from the field of histochemistry and cell biology

Investigations of cell and tissue structure and function using innovative methods and approaches have again yielded numerous exciting findings in recent months and have added important data to current knowledge, inspiring new ideas and hypotheses in various fields of modern life sciences. Topics and contents of comprehensive expert reviews covering different aspects in methodological advances, cell biology, tissue function and morphology, and novel findings reported in original papers are summarized in the present review.

Derivation and characterization of nonhuman primate embryonic stem cells

Embryonic stem (ES) cells are a powerful research tool enabling the generation of mice with custom genetics, the study of the earliest stages of mammalian differentiation in vitro and, with the isolation of human ES cells, the potential of cell-based therapies for a number of diseases including Parkinson's and Type 1 diabetes. ES cells isolated from nonhuman primates (nhpES cells) offer the opportunity to ethically test the developmental potential of primate ES cells in chimeric offspring. If these cells have similar potency to mouse ES cells, this may open a new era of primate models of human disease. Nonhuman primates are the perfect model system for the preclinical testing of ES cell-derived therapies. In this unit, we describe methods for the derivation and characterization of nonhuman primate ES cells. With these protocols, the investigator will be able to isolate nhpES cells and perform the necessary tests to confirm the pluripotent phenotype.

[Heart tissue from embryonic stem cells]

Embryonic stem cells can give rise to all somatic cells, making them an attractive cell source for tissue engineering applications. The propensity of cells to form tissue-like structures in a culture dish has been well documented. We and others made use of this intrinsic property to generate bioartificial heart muscle. First proof-of-concept studies involved immature heart cells mainly from fetal chicken, neonatal rats and mice. They eventually provided evidence that force-generating heart muscle can be engineered in vitro. Recently, the focus shifted to the application of stem cells to eventually enable the generation of human heart muscle and reach following long-term goals: (1) development of a simplified in vitro model of heart muscle development; (2) generation of a human test-bed for drug screening and development; (3) allocation of surrogate heart tissue to myocardial repair applications. This overview will provide the background for cell-based myocardial repair, introduce the main myocardial tissue engineering concepts, discuss the use of embryonic and non-embryonic stem cells, and lays out the potential direct and indirect therapeutic use of human tissue engineered myocardium.

HLA homozygous stem cell lines derived from human parthenogenetic blastocysts

Individual HLA homozygous parthenogenetic human stem cell (hpSC-Hhom) lines have the potential for cell-based therapy in a significant number of individuals, provided the HLA haplotype is prevalent. We report the successful derivation of four stable hpSC-Hhom lines from both HLA homozygous and HLA heterozygous donors. Of these, the hpSC-Hhom-4 line carries the HLA haplotype found most commonly within the U.S. population, and is shared by different racial groups. These hpSC-Hhom lines demonstrate typical human embryonic stem cell morphology, expressing appropriate stem cell markers and possessing high levels of alkaline phosphatase and telomerase activity. Additionally, injection of these cell lines into immunodeficient animals leads to teratoma formation. G-banded karyotyping demonstrates a normal 46,XX karyotype in lines hpSC-Hhom-1 and hpSC-Hhom-4, and chromosomal anomalies in lines hpSC-Hhom-2 and hpSC-Hhom-3, both derived from the same donor. HLA genotyping of all four hpSC-Hhom lines demonstrates that they are HLA homozygous. Furthermore, in the case of HLA heterozygous donors, the hpSC-Hhom lines inherit the haplotype from only one of the donor's parents. Single-nucleotide polymorphism (SNP) data analysis suggests that hpSC-Hhom lines derived from HLA heterozygous oocyte donors are homozygous throughout the genome as assessed by SNP analysis. The protocol used for deriving these HLA homozygous stem cell lines minimizes the use of animal-derived components, which makes them more appealing for potential clinical application.

Parthenogenesis as an approach to pluripotency: advantages and limitations involved

Embryonic stem cells (ESCs) are invaluable cells derived from the inner cell mass of the mammalian blastocyst. They have nearly indefinite self-renewal, retain their developmental potential after prolonged periods in culture and display great plasticity that allow them to differentiate into all cell types of the body. They provide exciting opportunities to develop unique models for developmental research and hold great potential for cell and tissue replacement therapy. However, these unique cells cannot be obtained without destroying an embryo and, despite the potential therapeutic usefulness, their derivation in the human raises substantial ethical as well as legal and political concerns because it unavoidably involves the destruction of viable embryos. In the recent years a number of scientific proposals that do not require the generation and subsequent destruction of human embryos have been put forward in an attempt to fill the gap between ethical questions and potential scientific and medical benefits. In this review we briefly summarize data obtained from the literature related to these different alternative approaches and focus in more details on our experience in the derivation of parthenothes, as a possible alternative source for pluripotent cells, discussing the advantages as well as the limits of these cell lines.

Stem cells and tissue engineering applications of the genitourinary tract

The field of regenerative medicine continues to make substantial advancements in therapeutic strategies addressing urologic diseases. Tissue engineering borrows principles from the fields of cell biology, materials science, transplantation and engineering in an effort to repair or replace damaged tissues. This review is intended to provide a current overview of the use of stem cells and tissue engineering technologies specifically in the treatment of genitourinary diseases. Current themes in the field include the use of adult stem cells seeded onto biocompatible resorbable matrices for implantation as tissue substitutes, which is conducive to host tissue in-growth. Injection therapy of adult stem cells for organ rehabilitation is also making strong headway toward the restoration of organ structure and function. With new data describing the molecular mechanisms for differentiation, work has begun on targeting tissues for regeneration by genetic modification methods. Promising laboratory discoveries portend the emergence of a new class of clinical therapies for regenerative medicine applications in the genitourinary tract.

Parthenotes as a source of embryonic stem cells

The derivation and study of human embryonic stem cell lines, despite their potential therapeutic usefulness, raise considerable ethical, religious, legal and political concerns because it inevitably leads to the destruction of viable embryos. In an attempt to bridge the division between ethical questions and potential scientific and medical benefits, considerable efforts have been devoted to the search for alternative sources of pluripotent cell lines. In this review we discuss the use of artificial parthenogenesis as a way to create entities, called parthenotes, that may represent an alternative ethical source for pluripotent cell lines. We describe the biological differences between parthenotes and embryos, in order to provide a rationale for the discussion on whether their use can be acceptable as a source of stem cells. We present data derived from animal models on the extent parthenogenetic stem cells are similar to biparental cell lines and discuss these aspects in the context of their extension to the human species. Finally, we present experiments recently carried out in our laboratory that allowed us to generate human parthenotes through artificial activation of human oocytes and to use them as a source for the derivation of parthenogenetic pluripotent cell lines.

Derivation of human embryonic stem cell lines from parthenogenetic blastocysts

Parthenogenesis is one of the main, and most useful, methods to derive embryonic stem cells (ESCs), which may be an important source of histocompatible cells and tissues for cell therapy. Here we describe the derivation and characterization of two ESC lines (hPES-1 and hPES-2) from in vitro developed blastocysts following parthenogenetic activation of human oocytes. Typical ESC morphology was seen, and the expression of ESC markers was as expected for alkaline phosphatase, octamer-binding transcription factor 4, stage-specific embryonic antigen 3, stage-specific embryonic antigen 4, TRA-1-60, and TRA-1-81, and there was absence of expression of negative markers such as stage-specific embryonic antigen 1. Expression of genes specific for different embryonic germ layers was detected from the embryoid bodies (EBs) of both hESC lines, suggesting their differentiation potential in vitro. However, in vivo, only hPES-1 formed teratoma consisting of all three embryonic germ layers (hPES-2 did not). Interestingly, after continuous proliferation for more than 100 passages, hPES-1 cells still maintained a normal 46 XX karyotype; hPES-2 displayed abnormalities such as chromosome translocation after long term passages. Short Tandem Repeat (STR) results demonstrated that the hPES lines were genetic matches with the egg donors, and gene imprinting data confirmed the parthenogenetic origin of these ES cells. Genome-wide SNP analysis showed a pattern typical of parthenogenesis. All of these results demonstrated the feasibility to isolate and establish human parthenogenetic ESC lines, which provides an important tool for studying epigenetic effects in ESCs as well as for future therapeutic interventions in a clinical setting.

A highly homozygous and parthenogenetic human embryonic stem cell line derived from a one-pronuclear oocyte following in vitro fertilization procedure

Homozygous human embryonic stem cells (hESCs) are thought to be better cell sources for hESC banking because their human leukocyte antigen (HLA) haplotype would strongly increase the degree of matching for certain populations with relatively smaller cohorts of cell lines. Homozygous hESCs can be generated from parthenogenetic embryos, but only heterozygous hESCs have been established using the current strategy to artificially activate the oocyte without second polar body extrusion. Here we report the first successful derivation of a human homozygous ESC line (chHES-32) from a one-pronuclear oocyte following routine in vitro fertilization treatment. chHES-32 cells express common markers and genes with normal hESCs. They have been propagated in an undifferentiated state for more than a year (>P50) and have maintained a stable karyotype of 46, XX. When differentiated in vivo and in vitro, chHES-32 cells can form derivatives from all three embryonic germ layers. The almost undetectable expression of five paternally expressed imprinted genes and their HLA genotype identical to the oocyte donor indicated their parthenogenetic origin. Using genome-wide single-nucleotide polymorphism analysis and DNA fingerprinting, the homozygosity of chHES-32 cells was further confirmed. The results indicated that 'unwanted' one-pronuclear oocytes might be a potential source for human homozygous and parthenogenetic ESCs, and suggested an alternative strategy for obtaining homozygous hESC lines from parthenogenetic haploid oocytes.

Human parthenogenetic blastocysts derived from noninseminated cryopreserved human oocytes

OBJECTIVE

To report on the development of human parthenogenetic blastocysts and an in vitro attachment that was generated from noninseminated cryopreserved human oocytes for the first time.

DESIGN

Prospective study.

SETTING

Department of reproductive medicine in a medical institute in Buenos Aires, Argentina.

PATIENT(S)

Five healthy fertile donors.

INTERVENTION(S)

Artificial activation of noninseminated cryopreserved human oocytes after thawing, parthenote culture, and their in vitro attachment.

MAIN OUTCOME MEASURE(S)

Survival rate, activation rate, cleavage rate, and blastocyst formation.

RESULT(S)

Thirty-six of 38 cryopreserved noninseminated oocytes survived after thawing (survival rate, 94.7%). Thirty-one of 36 oocytes showed one pronucleus (activation rate, 86.1%). Thirty of 31 cleaved (cleavage rate, 96.8%). Five of 30 showed cavitation (blastocyst rate, 16.7%).

CONCLUSION(S)

Noninseminated cryopreserved human oocytes showed a high survival rate after thawing. They responded very satisfactorily to artificial activation, which was followed by a high rate of parthenogenetic embryos, which can develop into blastocysts. In the future, these could be a new source for development of human parthenogenetic stem cells.

Patient-specific stem cell lines derived from human parthenogenetic blastocysts

Parthenogenetic activation of human oocytes may be one way to produce histocompatible cells for cell-based therapy. We report the successful derivation of six pluripotent human embryonic stem cell (hESC) lines from blastocysts of parthenogenetic origin. The parthenogenetic human embryonic stem cells (phESC) demonstrate typical hESC morphology, express appropriate markers, and possess high levels of alkaline phosphatase and telomerase activity. The phESC lines have a normal 46, XX karyotype, except one cell line, and have been cultured from between 21 to 35 passages. The phESC lines form embryoid bodies in suspension culture and teratomas after injection to immunodeficient animals and give differentiated derivatives of all three embryonic germ layers. DNA profiling of all six phESC lines demonstrates that they are MHC matched with the oocyte donors. The study of imprinted genes demonstrated further evidence of the parthenogenetic origin of the phESC lines. Our research has resulted in a protocol for the production of human parthenogenetic embryos and the derivation of stem cell lines from them, which minimizes the presence of animal-derived components, making the derived phESC lines more suitable for potential clinical use.

Derivation and cloning of a novel rhesus embryonic stem cell line stably expressing tau-green fluorescent protein

Embryonic stem cells (ESC) have the ability of indefinite self-renewal and multilineage differentiation, and they carry great potential in cell-based therapies. The rhesus macaque is the most relevant preclinical model for assessing the benefit, safety, and efficacy of ESC-based transplantations in the treatment of neurodegenerative diseases. In the case of neural cell grafting, tracing both the neurons and their axonal projections in vivo is essential for studying the integration of the grafted cells in the host brain. Tau-Green fluorescent protein (tau-GFP) is a powerful viable lineage tracer, allowing visualization of cell bodies, dendrites, and axons in exquisite detail. Here, we report the first rhesus monkey ESC line that ubiquitously and stably expresses tau-GFP. First, we derived a new line of rhesus monkey ESC (LYON-ES1) that show marker expression and cell cycle characteristics typical of primate ESCs. LYON-ES1 cells are pluripotent, giving rise to derivatives of the three germ layers in vitro and in vivo through teratoma formation. They retain all their undifferentiated characteristics and a normal karyotype after prolonged culture. Using lentiviral infection, we then generated a monkey ESC line stably expressing tau-GFP that retains all the characteristics of the parental wild-type line and is clonogenic. We show that neural precursors derived from the tau-GFP ESC line are multipotent and that their fate can be precisely mapped in vivo after grafting in the adult rat brain. Disclosure of potential conflicts of interest is found at the end of this article.

Heterozygous embryonic stem cell lines derived from nonhuman primate parthenotes

Monoparental parthenotes represent a potential source of histocompatible stem cells that should be isogenic with the oocyte donor and therefore suitable for use in cell or tissue replacement therapy. We generated five rhesus monkey parthenogenetic embryonic stem cell (PESC) lines with stable, diploid female karyotypes that were morphologically indistinguishable from biparental controls, expressed key pluripotent markers, and generated cell derivatives representative of all three germ layers following in vivo and in vitro differentiation. Interestingly, high levels of heterozygosity were observed at the majority of loci that were polymorphic in the oocyte donors. Some PESC lines were also heterozygous in the major histocompatibility complex region, carrying haplotypes identical to those of the egg donor females. Expression analysis revealed transcripts from some imprinted genes that are normally expressed from only the paternal allele. These results indicate that limitations accompanying the potential use of PESC-derived phenotypes in regenerative medicine, including aberrant genomic imprinting and high levels of homozygosity, are cell line-dependent and not always present. PESC lines were derived in high enough yields to be practicable, and their derivatives are suitable for autologous transplantation into oocyte donors or could be used to establish a bank of histocompatible cell lines for a broad spectrum of patients.

Immunohistochemical localisation of TRA-1-60, TRA-1-81, GCTM-2 and podocalyxin in the developing baboon kidney

The baboon is an ideal animal model to study human kidney development. The aim of the current study was to use immunohistochemistry to localise the antigens TRA-1-60, TRA-1-81, GCTM-2 and podocalyxin in the developing baboon kidney where nephrogenesis was still on-going and in kidneys where nephrogenesis was complete. Fixed kidney sections from baboons delivered at 125, 140, 175 and 185 days gestation (term = 185 days) were immuno-labelled with antibodies directed against TRA-1-60, TRA-1-81, GCTM-2 and podocalyxin. In kidneys with on-going nephrogenesis (125 and 140 days gestation), TRA-1-60, TRA-1-81 and GCTM-2 were specifically localised to the apical plasma membrane of the epithelium of the ureteric ampullae and the collecting ducts, while podocalyxin immunostaining was not detected. In kidneys where nephrogenesis was complete (175 and 185 days gestation) localisation of these markers was again very specifically localised to the collecting ducts. In conclusion, although further experimentation is required to confirm the identity of the specific cell types marked by these antibodies, this study provides new insight into the distribution of commonly utilised stem cell antibodies in the developing baboon kidney.

Alternative sources of pluripotent stem cells: scientific solutions to an ethical dilemma

Stem cell researchers in the United States have faced a quagmire of uncertainty due to multiple factors: the ethical divide over the use of embryos for research, the lack of clarity in federal guidelines governing this research, the restrictive patent situation surrounding the generation of new human embryonic stem (HES) cell lines; and the limits on types of research eligible for federal funding. In this commentary, we describe how recent advances in derivation of hES cell-like lines may allow at least some of these uncertainties to be resolved. More importantly, we suggest that the derivation of hES cell-like lines by morally acceptable methods would not only avoid the corrosive effects of a protracted ethical debate over stem cell research, but would also allow U.S. researchers to access federal funds and compete on a more level international playing field.

Human embryonic stem cells: preclinical perspectives

Human embryonic stem cells (hESCs) have been extensively discussed in public and scientific communities for their potential in treating diseases and injuries. However, not much has been achieved in turning them into safe therapeutic agents. The hurdles in transforming hESCs to therapies start right with the way these cells are derived and maintained in the laboratory, and goes up-to clinical complications related to need for patient specific cell lines, gender specific aspects, age of the cells, and several post transplantation uncertainties. The different types of cells derived through directed differentiation of hESC and used successfully in animal disease and injury models are described briefly. This review gives a brief outlook on the present and the future of hESC based therapies, and talks about the technological advances required for a safe transition from laboratory to clinic.

Embryonic stem cells for cardiac muscle engineering

The aim of cardiac tissue engineering is twofold: (1) to provide three-dimensional cardiac tissue to restore the function of diseased hearts and (2) to develop improved test beds for target validation and substance screening. Both concepts have been successfully demonstrated by several groups using immature primary heart cells, but these cells are essentially postmitotic, precluding clinical and large-scale in vitro applications. Identification of a renewable cell source is therefore one of the key objectives in the field. Embryonic stem (ES) cells are attractive candidates because they can be propagated in large quantities, have a robust capacity to differentiate into cardiac myocytes, and can be obtained from humans. Classic isolation of ES cells from the inner cell mass is associated with destruction of the respective embryo. Thus, alternative technologies to generate stem cell lines with ES cell properties are inevitably called for. This review discusses the usefulness of ES cells in cardiac tissue engineering and alternative, embryo-sparing technologies to derive ES cells.

Stem cells for the treatment of spinal cord injury

This article reviews stem cell-based strategies for spinal cord injury repair, and practical issues concerning their translation to the clinic. Recent progress in the stem cell field includes clinically compliant culture conditions and directed differentiation of both embryonic stem cells and somatic stem cells. We provide a brief overview of the types of stem cells under evaluation, comparing their advantages and disadvantages for use in human clinical trials. We review the practical considerations and risks that must be addressed before human treatments can begin. With a growing understanding of these practical issues, stem cell biology, and spinal cord injury pathophysiology, stem cell-based therapies are moving closer to clinical application.

Simian fetal brain progenitor cells for studying viral neuropathogenesis

The pathogenesis of neurologic dysfunctions caused by human immunodeficiency virus type 1 (HIV-1) infection is not yet well understood. Simian immunodeficiency virus (SIV) infection of macaques is an important animal model for HIV-1 infection. This is the first report to characterize brain progenitor cells (BPCs) isolated from embryonic brain of cynomolgus monkeys (Macaca fascicularis) by neurosphere assay and utilize BPC-derived cell culture for studying SIV infection. The self-renewal and multilineage differentiation properties of BPCs are convenient for planning viral infection experiments. The BPC-derived culture does not contain macrophage/microglial cells, fibroblasts, or endothelial cells. Thus, this culture is appropriate for studying direct relation between SIV infection and neuronal and glial cells. First, the authors characterized undifferentiated and differentiated simian BPCs by immunocytochemistry, flow cytometry analysis, real-time polymerase chain reaction (PCR), and reverse transcriptase (RT)-PCR. The BPCs induced to differentiate by the addition of 1% fetal bovine serum (FBS) were composed of heterogeneous cells expressing nestin, glial fibrillary acidic protein (GFAP), and/or tubulin beta III isoform (Tuj). None of them expressed the monocyte/macrophage/microglial marker. mRNA expression of CD4, CXCR4, CCR5, GPR1, STRL33, and APJ in both undifferentiated and differentiated BPCs were shown by RT-PCR method, suggesting that SIV would infect and replicate in this culture system. Then, it was confirmed that the neurotropic SIV strain, SIV17/E-Fr, replicated productively in BPC-derived cells. The SIV/17E-FrDelta nefGFP was inoculated to identify the infected cells and immunocytochemistry analysis revealed that green fluorescent protein (GFP)-expressing cells were mostly GFAP positive and coexpressed with SIV p27 antigen. Thus, BPC-derived cell culture system is applicable for studying SIV infection in glial and neuronal cells.

Can we develop ethically universal embryonic stem-cell lines?

Human embryonic stem-cell (hESC) research faces opposition from those who object to the destruction of human embryos. Over the past few years, a series of new approaches have been proposed for deriving hESC lines without injuring a living embryo. Each of these presents scientific challenges and raises ethical and political questions. Do any of these methods have the potential to provide a source of hESCs that will be acceptable to those who oppose the current approaches?

Directed differentiation and transplantation of human embryonic stem cell-derived motoneurons

Motoneurons represent a specialized class of neurons essential for the control of body movement. Motoneuron loss is the cause of a wide range of neurological disorders including amyotrophic lateral sclerosis and spinal muscular atrophy. Embryonic stem cells are a promising cell source for the study and potential treatment of motoneuron diseases. Here, we present a novel in vitro protocol of the directed differentiation of human embryonic stem cells (hESCs) into engraftable motoneurons. Neural induction of hESCs was induced on MS5 stromal feeders, resulting in the formation of neural rosettes. In response to sonic hedgehog and retinoic acid, neural rosettes were efficiently directed into spinal motoneurons with appropriate in vitro morphological, physiological, and biochemical properties. Global gene expression analysis was used as an unbiased measure to confirm motoneuron identity and type. Transplantation of motoneuron progeny into the developing chick embryo resulted in robust engraftment, maintenance of motoneuron phenotype, and long-distance axonal projections into peripheral host tissues. Transplantation into the adult rat spinal cord yielded neural grafts comprising a large number of human motoneurons with outgrowth of choline acetyltransferase positive fibers. These data provide evidence for in vivo survival of hESC-derived motoneurons, a key requirement in the development of hESC-based cell therapy in motoneuron disease. Disclosure of potential conflicts of interest is found at the end of this article.

Differentiation potential of histocompatible parthenogenetic embryonic stem cells

Embryonic stem cells (ESCs) hold unique promise for the development of cell replacement therapies, but derivation of therapeutic products from ESCs is hampered by immunological barriers. Creation of HLA-typed ESC banks, or derivation of customized ESC lines by somatic cell nuclear transfer, have been envisioned for engineering histocompatible ESC-derived products. Proof of principle experiments in the mouse have demonstrated that autologous ESCs can be obtained via nuclear transfer and differentiated into transplantable tissues, yet nuclear transfer remains a technology with low efficiency. Parthenogenesis provides an additional means for deriving ESC lines. In parthenogenesis, artificial oocyte activation initiates development without sperm contribution and no viable offspring are produced in the absence of paternal gene expression. Development proceeds readily to the blastocyst stage, from which parthenogenetic ESC (pESC) lines can be derived with high efficiency. We have recently shown that when pESC lines are derived from hybrid mice, early recombination events produce heterozygosity at the major histocompatibility complex (MHC) loci in some of these lines, enabling the generation of histocompatible differentiated cells that can engraft immunocompetent MHC-matched mouse recipients. Here, we explore the differentiation potential of murine pESCs derived in our laboratory.

Nuclear reprogramming: the strategy used in normal development is also used in somatic cell nuclear transfer and parthenogenesis

Somatic cell nuclear transfer (SCNT) and parthenogenesis are alternative forms of reproduction and development, building new life cycles on differentiated somatic cell nuclei and duplicated maternal chromatin, respectively. In the preceding paper (Sun F, et al., Cell Res 2007; 17:117-134.), we showed that an "erase-and-rebuild" strategy is used in normal development to transform the maternal gene expression profile to a zygotic one. Here, we investigate if the same strategy also applies to SCNT and parthenogenesis. The relationship between chromatin and chromatin factors (CFs) during SCNT and parthenogenesis was examined using immunochemical and GFP-fusion protein assays. Results from these studies indicated that soon after nuclear transfer, a majority of CFs dissociated from somatic nuclei and were redistributed to the cytoplasm of the egg. The erasure process in oogenesis is recaptured during the initial phase in SCNT. Most CFs entered pseudo-pronuclei shortly after their formation. In parthenogenesis, all parthenogenotes underwent normal oogenesis, and thus had removed most CFs from chromosomes before the initiation of development. The CFs were subsequently re-associated with female pronuclei in time and sequence similar to that in fertilized embryos. Based on these data, we conclude that the "erase-and-rebuild" process observed in normal development also occurs in SCNT and in parthenogenesis, albeit in altered fashions. The process is responsible for transcription reprogramming in these procedures. The "erase" process in SCNT is compressed and the efficiency is compromised, which likely contribute to the developmental defects often observed in nuclear transfer (nt) embryos. Furthermore, results from this study indicated that the cytoplasm of an egg contains most, if not all, essential components for assembling the zygotic program and can assemble them onto appropriate diploid chromatin of distinct origins.

In vitro development of human oocytes after parthenogenetic activation or intracytoplasmic sperm injection

OBJECTIVE

To compare directly in vitro developmental competence between parthenogenetically activated and intracytoplasmic sperm injection (ICSI)-fertilized oocytes.

DESIGN

For each patient, three metaphase II oocytes were randomized to the ICSI procedure, while n-3 were allocated to parthenogenetic activation.

SETTING

University hospital infertility unit.

PATIENTS

Thirty-eight patients, aged 35.2 +/- 3.3 years (mean +/- SD) selected for ICSI.

INTERVENTIONS

After 1 hour from denudation, oocytes were either fertilized by ICSI (n = 114) or chemically activated (n = 104). Fertilized and activated oocytes were cultured for up to 3 and 5 days, respectively.

MAIN OUTCOME MEASURES

Development rate, cell number, and morphological grade during culture.

RESULTS

The two groups showed no significant differences between rates of fertilization and parthenogenetic activation, development, and blastomere number on days 2 and 3 of culture. However, parthenotes showed a lower morphological grade, and a significantly lower proportion went on cleaving to day 3, when only activated rather than total numbers of oocytes were considered. On day 5 after activation, nine oocytes (8.6%) reached the blastocyst stage, representing 12.9% of parthenotes.

CONCLUSIONS

Since most parameters examined in this study were similar between activated and fertilized oocytes, parthenogenetic activation may be a useful tool for the preclinical evaluation of experimental procedures.

Human embryo: a biological definition

This paper defines a human embryo from a biological standpoint that takes into account emerging technologies in reproductive science. The paper does not consider legal, moral, religious or social views. As the definition of a human embryo must reflect the multifactorial processes of development, an approach has been adopted which combines recognition of observed events with potential for further development. This acknowledges that fertilization and development are not static processes, and as such embryo status can only be defined by observation of specific markers. The following biological definition of 'human embryo' is proposed. A human embryo is a discrete entity that has arisen from either: the first mitotic division when fertilization of a human oocyte by a human sperm is complete or any other process that initiates organized development of a biological entity with a human nuclear genome or altered human nuclear genome that has the potential to develop up to, or beyond, the stage at which the primitive streak appears, and has not yet reached 8 weeks of development since the first mitotic division.

Human therapeutic cloning (NTSC)

Human therapeutic cloning or nuclear transfer stem cells (NTSC) to produce patient-specific stem cells, holds considerable promise in the field of regenerative medicine. The recent withdrawal of the only scientific publications claiming the successful generation of NTSC lines afford an opportunity to review the available research in mammalian reproductive somatic cell nuclear transfer (SCNT) with the goal of progressing human NTSC. The process of SCNT is prone to epigenetic abnormalities that contribute to very low success rates. Although there are high mortality rates in some species of cloned animals, most surviving clones have been shown to have normal phenotypic and physiological characteristics and to produce healthy offspring. This technology has been applied to an increasing number of mammals for utility in research, agriculture, conservation, and biomedicine. In contrast, attempts at SCNT to produce human embryonic stem cells (hESCs) have been disappointing. Only one group has published reliable evidence of success in deriving a cloned human blastocyst, using an undifferentiated hESC donor cell, and it failed to develop into a hESC line. When optimal conditions are present, it appears that in vitro development of cloned and parthenogenetic embryos, both of which may be utilized to produce hESCs, may be similar to in vitro fertilized embryos. The derivation of ESC lines from cloned embryos is substantially more efficient than the production of viable offspring. This review summarizes developments in mammalian reproductive cloning, cell-to-cell fusion alternatives, and strategies for oocyte procurement that may provide important clues facilitating progress in human therapeutic cloning leading to the successful application of cell-based therapies utilizing autologous hESC lines.

Ethical questions concerning research on human embryos, embryonic stem cells and chimeras

Research using human embryos and embryonic stem cells is viewed as important for various reasons. Apart from questions concerning legal regulations, numerous ethical objections are raised pertaining to the use of surplus embryos from reproductive medicine as well as the creation of embryos and stem cells through cloning. In the hopes of avoiding ethical problems, alternatives have been proposed including the extraction of egg cells from "dead" embryos derived from in vitro fertilization procedures, the extraction of pluripotent stem cells from blastocysts, technologies such as "altered nuclear transfer" (ANT) and "oocyte-assisted reprogramming" (ANT-OAR) as well as parthenogenesis. Initial ethical assessments show that certain questions pertaining to such strategies have remained unanswered. Furthermore, with the help of new or more differentiated biotechnological procedures, it is possible to create chimeras and hybrids in which human and non-human cells are combined. Human-animal chimeras, in which gametes or embryonic tissue have been mixed with embryonic or adult stem cells, demonstrate a different "quality" and "degree of penetration" from those produced in previous experiments. Not only does this have consequences regarding questions of patentability, this situation also raises fundamental questions concerning the human being's self image, the concept of person, identity and species and the moral rights and duties that are connected with such concepts. There is a need for legal regulation, on the national as well as the international level.

Generation and characterization of rabbit embryonic stem cells

We described the derivation of four stable pluripotent rabbit embryonic stem cell (ESC) lines, one (RF) from blastocysts fertilized in vivo and cultured in vitro and three (RP01, RP02, and RP03) from parthenogenetic blastocysts. These ESC lines have been cultivated for extended periods (RF >1 year, RP01 >8 months, RP02 >8 months, and RP03 >6 months) in vitro while maintaining expression of pluripotent ESC markers and a normal XY or XX karyotype. The ESCs from all lines expressed alkaline phosphatase, transcription factor Oct-4, stage-specific embryonic antigens (SSEA-1, SSEA-3, and SSEA-4), and the tumor-related antigens (TRA-1-60 and TRA-1-81). Similar to human and mouse ESCs, rabbit ESCs expressed pluripotency (Oct-4, Nanog, SOX2, and UTF-1) and signaling pathway genes (fibroblast growth factor, WNT, and transforming growth factor pathway). Morphologically, rabbit ESCs resembled primate ESCs, whereas their proliferation characteristics were more like those seen in mouse ESCs. Rabbit ESCs were induced to differentiate into many cell types in vitro and formed teratomas with derivatives of the three major germ layers in vivo when injected into severe combined immunodeficient mice. Our results showed that pluripotent, stable ESC lines could be derived from fertilized and parthenote-derived rabbit embryos.

Transplanted dopamine neurons derived from primate ES cells preferentially innervate DARPP-32 striatal progenitors within the graft

The correct identity and functional capacity of transplanted dopamine (DA) neurons derived in vitro from embryonic stem (ES) cells is a critical factor for the development of an ES cell-based replacement therapy for Parkinson's disease. We transplanted primate Cyno-1 ES cells differentiated in vitro for 4 (progenitor ES cells) or 6 (differentiated ES cells) weeks, or control fetal primate cells into the striatum of hemi-parkinsonian rats. Partial behavioral recovery in amphetamine-induced rotation was correlated with the number of ES-derived tyrosine hydroxylase-positive (TH+) neurons in the grafts (r=0.5, P<0.05). Post mortem analysis of ES-derived grafts revealed TH+neurons with mature morphology, similar to fetal DA neurons, and expression of midbrain transcription factors, such as Engrailed (En) and Nurr-1. While the total number of TH+neurons was not different between the two groups, TH/En co-expression was significantly higher (>90%) in grafts from differentiated ES cells than in grafts derived from progenitor cells (<50%), reflecting a more heterogeneous cellular composition. Within the grafts there was an overlap between ES-derived TH+axonal arbors and clusters of primate ES-derived striatal neurons expressing brain factor 1 (Bf-1, Foxg1) and DA and cAMP-regulated phosphoprotein (DARPP-32). Such overlap was never observed for other regional transcription factors that define neighboring forebrain domains in the developing brain, such as Nkx2.1 (medial ganglionic eminence), Nkx2.2 (pallidal and diencephalic progenitors) or Pax6 (dorsal telencephalic progenitors). Despite the heterogeneity of ES-derived graft cell composition, these results demonstrate normal phenotypic specification, conserved natural axonal target selectivity and functionality of DA neurons derived from primate ES cells.

Immunogenicity and Engraftment of Mouse Embryonic Stem Cells in Allogeneic Recipients

Embryonic stem cells (ESCs) are pluripotent and therefore able to differentiate both in vitro and in vivo into specialized tissues under appropriate conditions, a property that could be exploited for cellular therapies. However, the immunological nature of these cells in vivo has not been well understood. In vitro, mouse-derived ESCs fail to stimulate T cells, but they abrogate ongoing alloresponses by a process that requires cell-cell contact. We further show that despite a high expression of the NKG2D ligand retinoic acid early inducible-1 by mouse ESCs, they remain resistant to natural killer cell lysis. In vivo, allogeneic mouse ESCs populate the thymus, spleen, and liver of sublethally irradiated allogeneic host mice, inducing apoptosis to T cells and establishing multilineage mixed chimerism that significantly inhibits alloresponses to donor major histocompatibility complex antigens. Immunohistochemical imaging revealed a significant percentage of ESC-derived cells in the splenic marginal zones, but not in the follicles. Taken together, the data presented here reveal that nondifferentiated mouse embryonic stem cells are non-immunogenic and appear to populate lymphoid tissues in vivo, leading to T-cell deletion by apoptosis.

Developmental expression of pluripotency determining factors in caprine embryos: Novel pattern of NANOG protein localization in the nucleolus

Transcription factors, POU5F1/OCT4 and NANOG, whose expression is restricted to the inner cell mass (ICM) in mouse and human blastocysts, are used to characterize undifferentiated embryonic stem cells (ESC) in vitro. However, POU5F1 may not be a useful marker in domestic animals due to its expression in both ICM and trophectoderm (TE), while NANOG mRNA and protein expression have only been described fully in mice. In an effort to identify ESC markers for domestic animals, expression patterns of NANOG, POU5F1, and the cell surface markers (SSEA1, SSEA4, TRA-1-60, TRA-1-81) were examined in preimplantation goat embryos, a species that has proven to be a superior choice for the production of transgenic proteins in milk (biopharming). Our results indicate that while goat embryos express POU5F1, SSEA1, and SSEA4 proteins, their expression is not strictly restricted to the ICM. In a unique staining pattern, NANOG protein was localized to the nucleoplasm and nucleoli in ICM cells, but was localized strictly to nucleoli in TE. This pattern may reflect down-regulation of protein by sequestration/degradation utilizing a nucleolar mechanism known to operate in stem cells. Furthermore, NANOG mRNA in TE was also significantly down-regulated as compared with that in ICM. Taken together, this novel expression pattern of NANOG in goat preimplantation embryos suggests that NANOG could serve as marker of pluripotency in goats and may be useful in derivation and characterization of caprine ESC. This study is the first to characterize both NANOG mRNA and protein expression in any species other than the mouse.

Isolation and characterization of novel rhesus monkey embryonic stem cell lines

ESCs are important as research subjects since the mechanisms underlying cellular differentiation, expansion, and self-renewal can be studied along with differentiated tissue development and regeneration in vitro. Furthermore, human ESCs hold promise for cell and tissue replacement approaches to treating human diseases. The rhesus monkey is a clinically relevant primate model that will likely be required to bring these clinical applications to fruition. Monkey ESCs share a number of properties with human ESCs, and their derivation and use are not affected by bioethical concerns. Here, we summarize our experience in the establishment of 18 ESC lines from rhesus monkey preimplantation embryos generated by the application of the assisted reproductive technologies. The newly derived monkey ESC lines were maintained in vitro without losing their chromosomal integrity, and they expressed markers previously reported present in human and monkey ESCs. We also describe initial efforts to compare the pluripotency of ESC lines by expression profiling, chimeric embryo formation, and in vitro-directed differentiation into endodermal, mesodermal, and ectodermal lineages.

The paths around stem cell intellectual property

Can new approaches for deriving human stem cells circumnavigate existing patents that dominate embryonic stem cell intellectual property?

Using therapeutic cloning to fight human disease: a conundrum or reality?

The development and transplantation of autologous cells derived from nuclear transfer embryonic stem cell (NT-ESC) lines to treat patients suffering from disease has been termed therapeutic cloning. Human NT is still a developing field, with further research required to improve somatic cell NT and human embryonic stem cell differentiation to deliver safe and effective cell replacement therapies. Furthermore, the implications of transferring mitochondrial heteroplasmic cells, which may harbor aberrant epigenetic gene expression profiles, are of concern. The production of human NT-ESC lines also remains plagued by ethical dilemmas, societal concerns, and controversies. Recently, a number of alternate therapeutic strategies have been proposed to circumvent the moral implications surrounding human nuclear transfer. It will be critical to overcome these biological, legislative, and moral restraints to maximize the potential of this therapeutic strategy and to alleviate human disease.

Generation and Characterization of Functional Cardiomyocytes from Rhesus Monkey Embryonic Stem Cells

Embryonic stem cells (ESCs) from mice and humans (hESCs) have been shown to be able to efficiently differentiate toward cardiomyocytes (CMs). Because murine ESCs and hESCs do not allow for establishment of pre-clinical allogeneic transplantation models, the aim of our study was to generate functional CMs from rhesus monkey ESCs (rESCs). Although formation of ectodermal and neuronal/glial cells appears to be the default pathway of the rESC line R366.4, we were able to change this commitment and to direct generation of endodermal/mesodermal cells and further differentiation toward CMs. Differentiation of rESCs resulted in an average of 18% of spontaneously contracting embryoid bodies (EBs) from rESCs. Semiquantitative reverse transcription-polymerase chain reaction analyses demonstrated expression of marker genes typical for endoderm, mesoderm, cardiac mesoderm, and CMs, including brachyury, goosecoid, Tbx-5, Tbx-20, Mesp1, Nkx2.5, GATA-4, FOG-2, Mlc2a, MLC2v, ANF, and alpha-MHC in rESC-derived CMs. Immunohistological and ultrastructural studies showed expression of CM-typical proteins, including sarcomeric actinin, troponin T, titin, connexin 43, and cross-striated muscle fibrils. Electrophysiological studies by means of multielectrode arrays revealed evidence of functionality, electrical coupling, and beta-adrenergic signaling of the generated CMs. This is the first study demonstrating generation of functional CMs derived from rESCs. In contrast to hESCs, rESCs allow for establishment of pre-clinical allogeneic transplantation models. Moreover, rESC-derived CMs represent a cell source for the development of high-throughput assays for cardiac safety pharmacology.

Bovine Embryonic Stem Cells

Bovine embryonic stem (bES) cell lines reported to date vary in morphology and marker expression, such as alkaline phosphatase (ALPL), stage-specific embryonic antigen 4 (SSEA4), and octamer-binding transcription factor-4 (OCT4), that normally are associated with the undifferentiated, pluripotent state. This chapter introduces the methods of isolating and maintaining bovine ES cells. These bovine ES cells grow in large, multicellular colonies resembling the mouse ES and embryonic germ (EG) cells, as well as human EG cells. Throughout the culture period, most of the cells within the colonies stain positive for ALPL and cell surface markers SSEA4 and OCT4. The staining patterns of the bES cells are identical to those of the blastocysts fertilized in vitro (IVF), yet different from most previously reported bovine ES cell lines, which are either negative or not detected. After undifferentiated culture for more than 1 year, these cells maintained the ability to differentiate into embryoid bodies and derivatives of all three EG layers, thus demonstrating their pluripotency. In addition to bES from IVF, this chapter introduces two methods of generating blastocyst stage embryos other than in vitro fertilization, which are parthenogenetic activation and somatic cell nuclear transfer for the potential application of generation "patient-specific" ES cells.

GeneChips in stem cell research

An understanding of the genes and signaling networks responsible for stem cell growth and differentiation will be essential for their ultimate therapeutic application. GeneChips are miniature platforms of nucleotides capable of monitoring the expression levels of almost every known and unknown gene. Performing a GeneChip experiment is like snapping a picture of a cell's mRNA (transcripts), thus giving a static view and measurement of gene expression inside the cell. Taking multiple "pictures" of stem cells as they grow and differentiate will provide insight into the genetic mechanisms of "stemness" or can be used to create "transcriptional signatures" to assess differentiation and variability between stem cell lines. The first half of this chapter covers the many components involved in a GeneChip experiment, illustrating the many variables at each step and describing a protocol for analysis that is inexpensive and requires minimal computer skills. The chapter then describes how researchers are currently applying GeneChips to stem cell biology. We conclude that the true potential of GeneChip technology lies in the in silico analysis-their integration and comparison of diverse data sets, where the biological questions are the driving force in the analysis.

Embryonic and extra-embryonic stem cell lines derived from single mouse blastomere

Evaluation of: Chung Y, Klimanskaya I, Becker S et al.: Embryonic and extra-embryonic stem cell lines derived from single mouse blastomere. Nature Epub ahead of publication Oct 16, Letters, 1–4 (2005).