Patient-specific embryonic stem cells derived from human SCNT blastocysts

Human Embryonic Stem Cells Reprogram Myeloid Precursors Following Cell-Cell Fusion

Here, we examine the ability of undifferentiated human embryonic stem cells (hESCs) to reprogram the nuclei of hESC-derived myeloid precursors following cell-cell fusion. Using an OP9 coculture system, we produced CD45+ CD33+ myeloperoxidase+ myeloid precursors from an Oct4-enhanced green fluorescent protein (EGFP) knock-in hESC line and demonstrated that Oct4-EGFP expression was extinguished in these precursors. Upon fusion with undifferentiated hESCs, EGFP expression from the endogenous Oct4 promoter/regulatory region was re-established, ESC-specific surface antigens and marker genes were expressed, and myeloid precursor-specific antigens were no longer detectable. When the hybrid cells were formed into embryoid bodies, upregulation of genes characteristic of the three germ layers and extraembryonic tissues occurred, indicating that the hybrid cells had the potential to differentiate into multiple lineages. Interestingly, the hybrid cells were capable of redifferentiating into myeloid precursors with efficiency comparable with that of diploid hESCs despite their neartetraploid chromosome complement. These results indicate that hESCs are capable of reprogramming nuclei from differentiated cells and that hESC hybrid cells provide a new model system for studying the mechanisms of nuclear reprogramming.

Egg harvesting for stem cell research: medical risks and ethical problems

Increasingly, researchers are seeking eggs from young women to be used for embryo cloning procedures. The harvesting of multiple eggs often involves the administration of drugs that have not been approved for this purpose. Also these drugs have not been adequately studied for their long-term effects on women despite research providing some evidence of significant harm to women in both the short and long term. Current practices follow a historical pattern of exposing women to risks that ultimately prove unacceptable. In addition, egg harvesting is taking place in a research climate marked by conflicts of interest, the misleading use of language to describe research goals, and a commercial push that may lead to the exploitation of young women. In this article, we outline these matters and explain how they are leading to an international campaign for a moratorium on egg harvesting for cloning purposes.

Human embryonic stem cell derivation: from the IVF perspective to therapeutic applications

Human embryonic stem cells (hESC) are capable of proliferating indefinitely in an undifferentiated state and are pluripotent, being able to differentiate into most cell types under the correct conditions. Since the establishment of the first hESC line in 1998, the hope has existed that these cells could constitute an unlimited cell source for replacement therapy in the treatment of various diseases and disabilities. However, there is opposition and concern within society towards hESC derivation. The purpose of this article is to introduce the medical and scientific issues surrounding hESC derivation for clinical use concerning the source for this research (human embryos donated from in vitro fertilization procedures), and the methodologies implicated in feeder-free, xeno-free derivation that will allow potential clinical applications.

Derivation of clinical-grade human embryonic stem cells

Embryonic stem cells proliferate in vitro while maintaining an undifferentiated state, and are capable of differentiating into most cell types under appropriate conditions. These properties imply great potential in the treatment of various diseases and disabilities. In fact, the first clinical trials with hESC for treating spinal cord injuries will begin next year. However, therapeutic application of human embryonic stem cell derivatives is compromised by the exposure of existing lines to animal and human components, with the subsequent risk of contamination with retroviruses and other pathogens, which can be transmitted to patients. The scientific community is striving to avoid the use of xenogeneic or allogeneic components in the process of derivation new hESC lines. This review summarizes attempts that have been made to avoid these contaminants and the breakthroughs achieved in the derivation of clinical-grade hESC that could be used for therapeutic purposes.

Reprogramming of human somatic cells by embryonic stem cell cytoplast

Somatic cell nuclear transfer (SCNT) provides the basis for the development of patient-specific stem cell lines. Recent progress in SCNT suggested the presence of reprogramming factors in human embryonic stem (hES) cells, although no method is currently available for replacement of nuclei of hES cells by somatic cell nuclei. An original technique has been developed, involving the fusion of different types of somatic cells with hES cells, which allowed a complete replacement of the nuclei of hES cells by nuclei of somatic cells. The resulting 'cybrids' were demonstrated to have the genotype of the donor somatic cells and 'stemness' of the recipient hES cells. However, the colonies isolated from the resulting fusion contained a mixture of these cybrid cells with the cells with the recipient nuclei, as well as hybrid cells containing both donor and recipient nuclei, so future purification will be necessary before the technique can be considered for future practical application.

Engineering myocardial tissue

To create an artificial heart is one of the most ambitious dreams of the young field of tissue engineering, a dream that, when publicly announced in 1999 (LIFE initiative around M. Sefton), provoked as much compassion as scepticism in the scientific and lay press. Today, it is fair to state that the field is still far away from having built the "bioartificial heart." Nevertheless, substantial progress has been made over the past 10 years, and a realistic perspective exists to create 3-dimensional heart muscle equivalents that may not only serve as experimental models but could also be useful for cardiac regeneration.

Embryonic stem-cell gametes: the new frontier in human reproduction

As infertility increases and gamete donations decline, an alternate source of sex cells may prove valuable for research and infertility treatment. This article examines the social and scientific value of gametes derived from the differentiation of established human embryonic stem (ES)-cell lines (ES-cell-derived gametes) and customized gametes created using nuclear transfer technologies to contain a haploid set of genes creating children genetically related to parent(s). ES-cell-derived gametes may be valuable as a resource for biomedical research, instruction and training in assisted reproductive technologies and perhaps for creating children. The creation of children by ES-cell-derived and customized gametes may not result in psychological harm to children but customized gametes may lead to physical harm to children or an accumulation of gene mutations in a population. Although the creation of new types of children using ES-cell gametes provides more reproductive choices to both fertile and infertile individuals, the risk or physical harm to children from customized gametes may be so severe that the scope of reproductive liberty must be limited. Further scientific and ethical analysis of the creation of children by ES-cell gametes is required.

Regulatory networks in embryo-derived pluripotent stem cells

Mammalian development requires the specification of over 200 cell types from a single totipotent cell. Investigation of the regulatory networks that are responsible for pluripotency in embryo-derived stem cells is fundamental to understanding mammalian development and realizing therapeutic potential. Extracellular signals and second messengers modulate cell-autonomous regulators such as OCT4, SOX2 and Nanog in a combinatorial complexity. Knowledge of this circuitry might reveal how to achieve phenotypic changes without the genetic manipulation of Oct4, Nanog and other toti/pluripotency-associated genes.

Banking on human embryonic stem cells: estimating the number of donor cell lines needed for HLA matching

BACKGROUND

Human embryonic stem (hES) cells are a promising source for transplantation to replace diseased or damaged tissue, but their differentiated progeny express human leucocyte antigens (HLAs) that will probably cause graft rejection. The creation of a bank of HLA-typed hES cells, from which a best match could be selected, would help reduce the likelihood of graft rejection. We investigated how many hES cell lines would be needed to make matching possible in most cases.

METHODS

The number of hES cell lines needed to achieve varying degrees of HLA match was estimated by use of, as a surrogate for hES-cell donor embryos, blood group and HLA types on a series of 10,000 consecutive UK cadaveric organ donors. The degree of blood group compatibility and HLA matching for a recipient population consisting of 6577 patients registered on the UK kidney transplant waiting list was determined, assuming all donor hES cell lines could provide a transplant for an unlimited number of recipients.

FINDINGS

A bank of 150 consecutive donors provided a full match at HLA-A, HLA-B, and HLA-DR for a minority of recipients (<20%); a beneficial match (defined as one HLA-A or one HLA-B mismatch only) or better for 37.9% (range 27.9-47.5); and an HLA-DR match or better for 84.9% (77.5-90.0). Extending the number of donors beyond 150 conferred only a very gradual incremental benefit with respect to HLA matching. A panel of only ten donors homozygous for common HLA types selected from 10,000 donors provided a complete HLA-A, HLA-B and HLA-DR match for 37.7% of recipients, and a beneficial match for 67.4%.

INTERPRETATION

Approximately 150 consecutive blood group compatible donors, 100 consecutive blood group O donors, or ten highly selected homozygous donors could provide the maximum practical benefit for HLA matching. The findings from these simulations have practical, political, and ethical implications for the establishment of hES-cell banks.

Significant improvement of mouse cloning technique by treatment with trichostatin A after somatic nuclear transfer

The low success rate of animal cloning by somatic cell nuclear transfer (SCNT) is believed to be associated with epigenetic errors including abnormal DNA hypermethylation. Recently, we elucidated by using round spermatids that, after nuclear transfer, treatment of zygotes with trichostatin A (TSA), an inhibitor of histone deacetylase, can remarkably reduce abnormal DNA hypermethylation depending on the origins of transferred nuclei and their genomic regions [S. Kishigami, N. Van Thuan, T. Hikichi, H. Ohta, S. Wakayama. E. Mizutani, T. Wakayama, Epigenetic abnormalities of the mouse paternal zygotic genome associated with microinsemination of round spermatids, Dev. Biol. (2005) in press]. Here, we found that 5-50 nM TSA-treatment for 10 h following oocyte activation resulted in more efficient in vitro development of somatic cloned embryos to the blastocyst stage from 2- to 5-fold depending on the donor cells including tail tip cells, spleen cells, neural stem cells, and cumulus cells. This TSA-treatment also led to more than 5-fold increase in success rate of mouse cloning from cumulus cells without obvious abnormality but failed to improve ES cloning success. Further, we succeeded in establishment of nuclear transfer-embryonic stem (NT-ES) cells from TSA-treated cloned blastocyst at a rate three times higher than those from untreated cloned blastocysts. Thus, our data indicate that TSA-treatment after SCNT in mice can dramatically improve the practical application of current cloning techniques.

Scientific and clinical opportunities for modeling blood disorders with embryonic stem cells

Our considerable wealth of data concerning hematologic processes has come despite difficulties working with stem and progenitor cells in vitro and their propensity to differentiate. Key methodologies that have sought to overcome such limitations include transgenic/knock-out animals and in vitro studies using murine embryonic stem cells, because both permit investigation of the formation of hematopoietic tissue from nonhematopoietic precursors. Although there have been many successful studies in model animals for understanding hematopoietic-cell development, differences between lower vertebrates and humans have left gaps in our understanding. Clearly, human-specific strategies to study the onset of hematopoiesis, particularly the earliest events leading to the specification of both normal and abnormal hematopoietic tissue, could bring an investigational renaissance. The recent availability of human embryonic stem (hES) cells suggests that such a system is now at hand. This review highlights the potential of hES cells to model human hematologic processes in vitro with an emphasis on disease targets.

Mitotic Remodeling of the Replicon and Chromosome Structure

Animal cloning by nuclear-transfer experiments frequently fails due to the inability of transplanted nuclei to support normal embryonic development. We show here that the formation of mitotic chromosomes in the egg context is crucial for adapting differentiated nuclei for early development. Differentiated erythrocyte nuclei replicate inefficiently in Xenopus eggs but do so as rapidly as sperm nuclei if a prior single mitosis is permitted. This mitotic remodeling involves a topoisomerase II-dependent shortening of chromatin loop domains and an increased recruitment of replication initiation factors onto chromatin, leading to a short interorigin spacing characteristic of early developmental stages. It also occurs within each early embryonic cell cycle and dominantly regulates initiation of DNA replication for the subsequent S phase. These results indicate that mitotic conditioning is crucial to reset the chromatin structure of differentiated adult donor cells for embryonic DNA replication and suggest that it is an important step in nuclear cloning.

Amyotrophic lateral sclerosis: recent advances and future therapies

PURPOSE OF REVIEW

Amyotrophic lateral sclerosis is a rare but fatal motoneuron disorder. Despite intensive research riluzole remains the only available therapy, with only marginal effects on survival. Here we review some of the recent advances in the search for a disease-modifying therapy for amyotrophic lateral sclerosis.

RECENT FINDINGS

A number of established agents have recently been re-investigated for their potential as neuroprotective agents, including beta-lactam antibiotics and minocycline. Progress has also been made in exploiting growth factors for the treatment of amyotrophic lateral sclerosis, partly due to advances in developing effective delivery systems to the central nervous system. A number of new therapies have also been identified, including a novel class of compounds, heat-shock protein co-inducers, which upregulate cell stress responses thereby mediating neuroprotection. Non-drug-based therapies are also under development, with progress in gene-silencing and stem cell therapies.

SUMMARY

In the past few years, significant advances have been made in both our understanding of amyotrophic lateral sclerosis pathogenesis and the development of new therapeutic approaches. However, caution must be exercised in view of the long-standing failure to successfully transfer therapeutic compounds to the clinic. A deeper awareness in the research community of the need for clinically relevant preclinical studies, coupled with a better understanding of the issues surrounding clinical trial design for amyotrophic lateral sclerosis, offers hope that the growing list of validated preclinical therapeutics can finally yield an effective disease-modifying treatment.

Temporal and parental-specific expression of imprinted genes in a newly derived Chinese human embryonic stem cell line and embryoid bodies

Although the study of imprinted genes in human development is very important, little is known about their expression and regulation in the early differentiation of human tissues due to lack of an appropriate model. In this study, a Chinese human embryonic stem (hES) cell line, SHhES1, was derived and fully characterized. Expression profiles of human imprinted genes were determined by Affymetrix Oligo micro-array in undifferentiated SHhES1 cells and SHhES1-derived embryoid bodies (EBs) at day 3, 8, 13 and 18. Thirty-two known human imprinted genes were detected in undifferentiated ES cells. Significantly, differential expression was found in nine genes at different stages of EB formation. Expression profile changes were confirmed by quantitative real-time reverse transcriptase-polymerase chain reaction in SHhES1 cells as well as in another independently derived hES cell line, HUES-7. In addition, the monoallelic expressions of four imprinted genes were examined in three different passages of undifferentiated ES cells and EBs of both hES cell lines. The monoallelic expressions of imprinted genes, H19, PEG10, NDNL1 and KCNQ1 were maintained in both undifferentiated hES cells and derived EBs. More importantly, with the availability of maternal peripheral blood lymphocyte sample, we demonstrated that the maternal expression of KCNQ1 and the paternal expression of NDNL1 and PEG10 were maintained in SHhES1 cells. These data provide the first demonstration that the parental-specific expression of imprinted genes is stable in EBs after extensive differentiation, also indicating that in vitro fertilization protocol does not disrupt the parental monoallelic expression of the imprinted genes examined.

Global gene expression profiles reveal significant nuclear reprogramming by the blastocyst stage after cloning

Nuclear transfer (NT) has potential applications in agriculture and biomedicine, but the technology is hindered by low efficiency. Global gene expression analysis of clones is important for the comprehensive study of nuclear reprogramming. Here, we compared global gene expression profiles of individual bovine NT blastocysts with their somatic donor cells and fertilized control embryos using cDNA microarray technology. The NT embryos' gene expression profiles were drastically different from those of their donor cells and closely resembled those of the naturally fertilized embryos. Our findings demonstrate that the NT embryos have undergone significant nuclear reprogramming by the blastocyst stage; however, problems may occur during redifferentiation for tissue genesis and organogenesis, and small reprogramming errors may be magnified downstream in development.

Derivation of human embryonic stem cell lines from embryos obtained after IVF and after PGD for monogenic disorders

BACKGROUND

Human embryonic stem (hES) cells are pluripotent cells usually derived from the inner cell mass (ICM) of blastocysts. Because of their ability to differentiate into all three embryonic germ layers, hES cells represent an important material for studying developmental biology and cell replacement therapy. hES cell lines derived from blastocysts diagnosed as carrying a genetic disorder after PGD represent in vitro disease models.

METHODS

ICMs isolated by immunosurgery from human blastocysts donated for research after IVF cycles and after PGD were plated in serum-free medium (except VUB01) on mouse feeder layers.

RESULTS

Five hES cell lines were isolated, two from IVF embryos and three from PGD embryos. All lines behave similarly in culture and present a normal karyotype. The lines express all the markers considered characteristic of undifferentiated hES cells and were proven to be pluripotent both in vitro and in vivo (ongoing for VUB05_HD).

CONCLUSIONS

We report here on the derivation of two hES cell lines presumed to be genetically normal (VUB01 and VUB02) and three hES cell lines carrying mutations for myotonic dystrophy type 1 (VUB03_DM1), cystic fibrosis (VUB04_CF) and Huntington disease (VUB05_HD).

Epigenetic modification is central to genome reprogramming in somatic cell nuclear transfer

The recent high-profile reports of the derivation of human embryonic stem cells (ESCs) from human blastocysts produced by somatic cell nuclear transfer (SCNT) have highlighted the possibility of making autologous cell lines specific to individual patients. Cell replacement therapies have much potential for the treatment of diverse conditions, and differentiation of ESCs is highly desirable as a means of producing the ranges of cell types required. However, given the range of immunophenotypes of ESC lines currently available, rejection of the differentiated cells by the host is a potentially serious problem. SCNT offers a means of circumventing this by producing ESCs of the same genotype as the donor. However, this technique is not without problems because it requires resetting of the gene expression program of a somatic cell to a state consistent with embryonic development. Some remodeling of parental DNA does occur within the fertilized oocyte, but the somatic genome presented in a radically different format to those of the gametes. Hence, it is perhaps unsurprising that many genes are expressed aberrantly within "cloned" embryos and the ESCs derived from them. Epigenetic modification of the genome through DNA methylation and covalent modification of the histones that form the nucleosome is the key to the maintenance of the differentiated state of the cell, and it is this that must be reset during SCNT. This review focuses on the mechanisms by which this is achieved and how this may account for its partial failure in the "cloning" process. We also highlight the potential dangers this may introduce into ESCs produced by this technology.

The egg-sharing model for human therapeutic cloning research: managing donor selection criteria, the proportion of shared oocytes allocated to research, and amount of financial subsidy given to the donor

Recent advances in human therapeutic cloning made by Hwang and colleagues have opened up new avenues of therapy for various human diseases. However, the major bottleneck of this new technology is the severe shortage of human donor oocytes. Egg-sharing in return for subsidized fertility treatment has been suggested as an ethically justifiable and practical solution to overcome the shortage of donor oocytes for therapeutic cloning. Because the utilization of shared oocytes in therapeutic cloning research does not result in any therapeutic benefit to a second party, this would necessitate a different management strategy compared to their use for the assisted conception of infertile women who are unable to produce any oocytes of their own. It is proposed that the pool of prospective egg-sharers in therapeutic cloning research be limited only to younger women (below 30 years of age) with indications for either male partner sub-fertility or tubal blockage. With regards to the proportion of the shared gametes being allocated to research, a threshold number of retrieved oocytes should be set that if not exceeded, would result in the patient being automatically removed from the egg-sharing scheme. Any excess supernumerary oocyte above this threshold number can be contributed to science, and allocation should be done in a randomized manner. Perhaps, a total of 10 retrieved oocytes from the patient may be considered a suitable threshold, since the chances of conception are unlikely to be impaired. With regards to the amount of subsidy being given to the patient, it is suggested that the proportion of financial subsidy should be equal to the proportion of the patient's oocytes being allocated to research. No doubt, the promise of future therapeutic benefit may be offered to the patient instead of financial subsidy. However, this is ethically controversial because therapeutic cloning has not yet been demonstrated to be a viable model of clinical therapy and any promises made to the patient might turn out to be illusionary. Hence, it is proposed that a tangible financial subsidy on the medical fees might be the better option for the patient's welfare.

Designer blood: creating hematopoietic lineages from embryonic stem cells

Embryonic stem (ES) cells exhibit the remarkable capacity to become virtually any differentiated tissue upon appropriate manipulation in culture, a property that has been beneficial for studies of hematopoiesis. Until recently, the majority of this work used murine ES cells for basic research to elucidate fundamental properties of blood-cell development and establish methods to derive specific mature lineages. Now, the advent of human ES cells sets the stage for more applied pursuits to generate transplantable cells for treating blood disorders. Current efforts are directed toward adapting in vitro hematopoietic differentiation methods developed for murine ES cells to human lines, identifying the key interspecies differences in biologic properties of ES cells, and generating ES cell-derived hematopoietic stem cells that are competent to repopulate adult hosts. The ultimate medical goal is to create patient-specific and generic ES cell lines that can be expanded in vitro, genetically altered, and differentiated into cell types that can be used to treat hematopoietic diseases.

Hot fusion

A team from Harvard University has demonstrated that human embryonic stem cells have the capacity to reprogram an adult cell nucleus, leading to a new way of deriving human embryonic stem cell lines without using oocytes.

Generation, culture, and differentiation of human embryonic stem cells for therapeutic applications

Embryonic stem (ES) cells, derived from the inner cell mass of the mammalian blastocyst, can continuously proliferate in an undifferentiated state and can also be induced to differentiate into a desired cell lineage. These abilities make ES cells an appealing source for cell replacement therapies, the study of developmental biology, and drug/toxin screening studies. As compared to mouse ES cells, human ES cells have only recently been derived and studied. Although there are many differences in properties between mouse and human ES cells, the study of mouse ES cells has provided important insights into human ES cell research. In this review, we describe the advantages and disadvantages of methods used for human ES cell derivation, the expansion of human ES cells, and the current status of human ES cell differentiation research. In addition, we discuss the endeavor that scientists have undertaken toward the therapeutic application of these cells, which includes therapeutic cloning and the improvement of human ES cell culture conditions.

Insulin-secreting cells derived from stem cells: clinical perspectives, hypes and hopes

Diabetes is a degenerative disease that results from the selective destruction of pancreatic beta-cells. These cells are responsible for insulin production and secretion in response to increases in circulating concentrations of nutrients, such as glucose, fatty acids and amino acids. This degenerative disease can be treated by the transplantation of differentiated islets obtained from cadaveric donors, according to a new surgical intervention developed as Edmonton protocol. Compared to the classical double transplant kidney-pancreas, this new protocol presents several advantages, concerning to the nature of the implant, immunosuppressive drug regime and the surgical procedure itself. However, the main problem to face in any islet transplantation program is the scarcity of donor pancreases and the low yield of islets isolated (very often around 50%) from each pancreas. Nevertheless, transplanted patients presented no adverse effects and no progression of diabetic complications. In the search of new cell sources for replacement trials, stem cells from embryonic and adult origins represent a key alternative. In order to become a realistic clinical issue transplantation of insulin-producing cells derived from stem cells, it needs to overcome multiple experimental obstacles. The first one is to develop a protocol that may allow obtaining a pure population of functional insulin-secreting cells as close as possible to the pancreatic beta-cell. The second problem should concern to the transplantation itself, considering issues related to immune rejection, tumour formation, site for implant, implant survival, and biosafety mechanisms. Although transplantation of bioengineered cells is still far in time, experience accumulated in islet transplantation protocols and in experiments with appropriate animal models will give more likely the clues to address this question in the future.

Generation of nuclear transfer-derived pluripotent ES cells from cloned Cdx2-deficient blastocysts

The derivation of embryonic stem (ES) cells by nuclear transfer holds great promise for research and therapy but involves the destruction of cloned human blastocysts. Proof of principle experiments have shown that 'customized' ES cells derived by nuclear transfer (NT-ESCs) can be used to correct immunodeficiency in mice. Importantly, the feasibility of the approach has been demonstrated recently in humans, bringing the clinical application of NT-ESCs within reach. Altered nuclear transfer (ANT) has been proposed as a variation of nuclear transfer because it would create abnormal nuclear transfer blastocysts that are inherently unable to implant into the uterus but would be capable of generating customized ES cells. To assess the experimental validity of this concept we have used nuclear transfer to derive mouse blastocysts from donor fibroblasts that carried a short hairpin RNA construct targeting Cdx2. Cloned blastocysts were morphologically abnormal, lacked functional trophoblast and failed to implant into the uterus. However, they efficiently generated pluripotent embryonic stem cells when explanted into culture.

Derivation of a human blastocyst after heterologous nuclear transfer to donated oocytes

This paper describes the derivation of a blastocyst following heterologous nuclear transfer (NT) into a human oocyte. It also demonstrates that a major obstacle to continuing research in human NT is the availability of suitable human oocytes. In this study, 36 oocytes were donated by 11 women undergoing four different treatments and their developmental potential was evaluated after NT. The time from oocyte collection to NT seems to be crucial, and only oocytes that were enucleated within 1 h proved successful. After enucleation of oocytes, fusion with undifferentiated human embryonic stem cells and in-vitro culture, early cleavage and blastocyst development of fused complexes was observed. The DNA fingerprinting comparison of the donor cells and derived blastocyst revealed successful heterologous NT, since both oocytes and donor cells were recovered from different patients. It has therefore been demonstrated that NT can be achieved in humans, using heterologous donor nuclei and surplus and donated oocytes. However, if the promise of this new science is to achieve its potential in the foreseeable future, it will be necessary to identify new sources of oocytes that can be used immediately after retrieval.