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

A case report of a normal fertile woman with 46,XX/46,XY somatic chimerism reveals a critical role for germ cells in sex determination

Individuals with 46,XX/XY chimerism can display a wide range of characteristics, varying from hermaphroditism to complete male or female, and can display sex chromosome chimerism in multiple tissues, including the gonads. The gonadal tissues of females contain both granulosa and germ cells. However, the specific sex chromosome composition of the granulosa and germ cells in 46,XX/XY chimeric female is currently unknown. Here, we reported a 30-year-old woman with secondary infertility who displayed a 46,XX/46,XY chimerism in the peripheral blood. FISH testing revealed varying degrees of XX/XY chimerism in multiple tissues of the female patient. Subsequently, the patient underwent preimplantation genetic testing (PGT) treatment, and 26 oocytes were retrieved. From the twenty-four biopsied mature oocytes, a total of 23 first polar bodies (PBs) and 10 second PBs were obtained. These PBs and two immature metaphase I (MI) oocytes only displayed X chromosome signals with no presence of the Y, suggesting that all oocytes in this chimeric female were of XX germ cell origin. On the other hand, granulosa cells obtained from individual follicles exhibited varied proportions of XX/XY cell types, and six follicles possessed 100% XX or XY granulosa cells. A total of 24 oocytes were successfully fertilized, and 12 developed into blastocysts, where 5 being XY and 5 were XX. Two blastocysts were transferred with one originating from an oocyte aspirated from a follicle containing 100% XY granulosa cells. This resulted in a twin pregnancy. Subsequent prenatal diagnosis confirmed normal male and female karyotypes. Ultimately, healthy boy-girl twins were delivered at full term. In summary, this 46,XX/XY chimerism with XX germ cells presented complete female, suggesting that germ cells may exert a significant influence on the sexual determination of an individual, which provide valuable insights into the intricate processes associated with sexual development and reproduction.

Uniparental parthenogenetic embryonic stem cell derivatives adaptable for bone and cartilage regeneration

Cells with the desired phenotype and number are critical for regenerative medicine and tissue engineering. Uniparental parthenogenetic embryonic stem cells (pESCs) share fundamental properties with embryonic stem cells. This study aims to determine the viability of pESC-based tissue engineering for bone and cartilage reconstruction. The mouse pESCs were cultured in suspension to form embryoid bodies. An adherent cultivation approach was employed to obtain parthenogenetic embryonic mesenchymal stem cells (pMSCs) from the embryoid bodies. Then, the pMSCs were cultured in conditional media to differentiate into osteogenic and chondrogenic lineages. The pESC-derived osteoblasts and chondroblasts were seeded into coral and sodium alginate scaffolds, respectively. The cell-seeded scaffolds were implanted into dorsal subcutaneous pockets of nude mice to evaluate ectopic reconstruction of bone and cartilage. We demonstrated that pESCs display the capacity to differentiate into all three germ layers. The generated pMSCs were able to differentiate into osteogenic and chondrogenic lineages, which survived well after seeding into coral and alginate acid scaffolds. Six weeks after cell-scaffold implantation, gross inspection and histological examination revealed that ectopic bone and cartilage tissues had successfully regenerated in the specimen. According to the findings of this study, pESC derivatives have a high potential for bone and cartilage regeneration.

bESC from cloned embryos do not retain transcriptomic or epigenetic memory from somatic donor cells

In brief

Epigenetic reprogramming after mammalian somatic cell nuclear transfer is often incomplete, resulting in low efficiency of cloning. However, gene expression and histone modification analysis indicated high similarities in transcriptome and epigenomes of bovine embryonic stem cells from in vitro fertilized and somatic cell nuclear transfer embryos.

Abstract

Embryonic stem cells (ESC) indefinitely maintain the pluripotent state of the blastocyst epiblast. Stem cells are invaluable for studying development and lineage commitment, and in livestock, they constitute a useful tool for genomic improvement and in vitro breeding programs. Although these cells have been recently derived from bovine blastocysts, a detailed characterization of their molecular state is lacking. Here, we apply cutting-edge technologies to analyze the transcriptomic and epigenomic landscape of bovine ESC (bESC) obtained from in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos. bESC were efficiently derived from SCNT and IVF embryos and expressed pluripotency markers while retaining genome stability. Transcriptome analysis revealed that only 46 genes were differentially expressed between IVF- and SCNT-derived bESC, which did not reflect significant deviation in cellular function. Interrogating histone 3 lysine 4 trimethylation, histone 3 lysine 9 trimethylation, and histone 3 lysine 27 trimethylation with cleavage under targets and tagmentation, we found that the epigenomes of both bESC groups were virtually indistinguishable. Minor epigenetic differences were randomly distributed throughout the genome and were not associated with differentially expressed or developmentally important genes. Finally, the categorization of genomic regions according to their combined histone mark signal demonstrated that all bESC shared the same epigenomic signatures, especially at gene promoters. Overall, we conclude that bESC derived from SCNT and IVF embryos are transcriptomically and epigenetically analogous, allowing for the production of an unlimited source of pluripotent cells from high genetic merit organisms without resorting to transgene-based techniques.

Generation of developmentally competent oocytes and fertile mice from parthenogenetic embryonic stem cells

Parthenogenetic embryos, created by activation and diploidization of oocytes, arrest at mid-gestation for defective paternal imprints, which impair placental development. Also, viable offspring has not been obtained without genetic manipulation from parthenogenetic embryonic stem cells (pESCs) derived from parthenogenetic embryos, presumably attributable to their aberrant imprinting. We show that an unlimited number of oocytes can be derived from pESCs and produce healthy offspring. Moreover, normal expression of imprinted genes is found in the germ cells and the mice. pESCs exhibited imprinting consistent with exclusively maternal lineage, and higher X-chromosome activation compared to female ESCs derived from the same mouse genetic background. pESCs differentiated into primordial germ cell-like cells (PGCLCs) and formed oocytes following in vivo transplantation into kidney capsule that produced fertile pups and reconstituted ovarian endocrine function. The transcriptome and methylation of imprinted and X-linked genes in pESC-PGCLCs closely resembled those of in vivo produced PGCs, consistent with efficient reprogramming of methylation and genomic imprinting. These results demonstrate that amplification of germ cells through parthenogenesis faithfully maintains maternal imprinting, offering a promising route for deriving functional oocytes and having potential in rebuilding ovarian endocrine function.

Molecular Mechanisms of Multi-Organ Failure in COVID-19 and Potential of Stem Cell Therapy

As the number of confirmed cases and deaths occurring from Coronavirus disease 2019 (COVID-19) surges worldwide, health experts are striving hard to fully comprehend the extent of damage caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although COVID-19 primarily manifests itself in the form of severe respiratory distress, it is also known to cause systemic damage to almost all major organs and organ systems within the body. In this review, we discuss the molecular mechanisms leading to multi-organ failure seen in COVID-19 patients. We also examine the potential of stem cell therapy in treating COVID-19 multi-organ failure cases.

Rescuing monopronucleated-derived human blastocysts: a model to study chromosomal topography and fingerprinting

OBJECTIVE

To quantify the percentage of monopronuclear-derived blastocysts (MNBs) that are potentially useful for reproductive purposes using classic and state-of-the-art chromosome analysis approaches, and to study chromosomal distribution in the inner cell mass (ICM) and trophectoderm (TE) for intertissue/intratissue concordance comparison.

DESIGN

Prospective experimental study.

SETTING

Single-center in vitro fertilization clinic and reproductive genetics laboratory.

PATIENT(S)

A total of 1,128 monopronuclear zygotes were obtained between June 2016 and December 2018.

INTERVENTION(S)

MNBs were whole-fixed or biopsied to obtain a portion of ICM and 2 TE portions (TE1 and TE2) and were subsequently analyzed by fluorescence in situ hybridization, new whole-genome sequencing, and fingerprinting by single-nucleotide polymorphism array-based techniques (a-SNP).

MAIN OUTCOME MEASURE(S)

We assessed MNB rate, ploidy rate, and chromosomal constitution by new whole-genome sequencing, and parental composition by comparative a-SNP, performed in a "trio"-format (embryo/parents). The 24-chromosome distribution was compared between the TE and the ICM and within the TE.

RESULT(S)

A total of 18.4% of monopronuclear zygotes progressed to blastocysts; 77.6% of MNBs were diploid; 20% of MNBs were male and euploid, which might be reproductively useful. Seventy-five percent of MNBs were biparental and half of them were euploid, indicating that 40% might be reproductively useful. Intratissue concordance (TE1/TE2) was established for 93.3% and 73.3% for chromosome matching. Intertissue concordance (TE/ICM) was established for 78.8%, but 57.6% for chromosome matching. When segmental aneuploidy was not considered, intratissue concordance and chromosome matching increased to 100% and 80%, respectively, and intertissue concordance and chromosome matching increased to 84.8% and 75.8%, respectively.

CONCLUSION(S)

The a-SNP-trio strategy provides information about ploidy, euploidy, and parental origin in a single biopsy. This approach enabled us to identify 40% of MNBs with reproductive potential, which can have a significant effect in the clinical setting. Additionally, segmental aneuploidy is relevant for mismatched preimplantation genetic testing of aneuploidies, both within and between MNB tissues. Repeat biopsy might clarify whether segmental aneuploidy is a prone genetic character.

Convergence of human pluripotent stem cell, organoid, and genome editing technologies

The last decade has seen many exciting technological breakthroughs that greatly expanded the toolboxes for biological and biomedical research, yet few have had more impact than induced pluripotent stem cells and modern-day genome editing. These technologies are providing unprecedented opportunities to improve physiological relevance of experimental models, further our understanding of developmental processes, and develop novel therapies. One of the research areas that benefit greatly from these technological advances is the three-dimensional human organoid culture systems that resemble human tissues morphologically and physiologically. Here we summarize the development of human pluripotent stem cells and their differentiation through organoid formation. We further discuss how genetic modifications, genome editing in particular, were applied to answer basic biological and biomedical questions using organoid cultures of both somatic and pluripotent stem cell origins. Finally, we discuss the potential challenges of applying human pluripotent stem cell and organoid technologies for safety and efficiency evaluation of emerging genome editing tools.

Differentiation of Human Parthenogenetic Embryonic Stem Cells into Functional Hepatocyte-like Cells

Stem cell and tissue engineering-based therapies for acute liver failure (ALF) have been limited by the lack of an optimal cell source. We aimed to determine the suitability of human parthenogenetic embryonic stem cells (hPESCs) for the development of strategies to treat ALF. We studied the ability of human parthenogenetic embryonic stem cells (hPESCs) with high whole-genome SNP homozygosity, which were obtained by natural activation during in vitro fertilization (IVF), to differentiate into functional hepatocyte-like cells in vitro by monolayer plane orientation. hPESCs were induced on a single-layer flat plate for 21 d in complete medium with the inducers activin A, FGF-4, BMP-2, HGF, OSM, DEX, and B27. Polygonal cell morphology and binuclear cells were observed after 21 d of induction by using an inverted microscope. RT-qPCR results showed that the levels of hepatocyte-specific genes such as AFP, ALB, HNF4a, CYP3A4, SLCO1B3, and ABCC2 significantly increased after induction. Immunocytochemical assay showed CK18 and Hepa expression in the induced cells. Indocyanine green (ICG) staining showed that the cells had the ability to absorb and metabolize dyes. Detection of marker proteins and urea in cell culture supernatants showed that the cells obtained after 21 d of induction had synthetic and secretory functions. The typical ultrastructure of liver cells was observed using TEM after 21 d of induction. The results indicate that naturally activated hPESCs can be induced to differentiate into hepatocellular cells by monolayer planar induction.

Obstetric and neonatal outcomes after the transfer of vitrified-warmed blastocysts developing from nonpronuclear and monopronuclear zygotes: a retrospective cohort study

OBJECTIVE

To evaluate the obstetric and neonatal outcomes after the transfer of vitrified-warmed single blastocysts developing from nonpronuclear (0PN) and monopronuclear (1PN) zygotes.

DESIGN

Cohort study.

SETTING

Affiliated hospital.

PATIENT(S)

This study was a retrospective analysis of 435 0PN and 281 1PN vitrified-warmed single blastocyst transfers, and 151 0PN and 75 1PN singletons, compared with 13,167 two-pronuclear (2PN) vitrified-warmed single blastocyst transfers and 4,559 2PN singletons, respectively.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pregnancy rate (PR), abortion rate (AR), live birth rate (LBR), and singleton birthweight were the primary outcome measures.

RESULT(S)

PR, AR, and LBR were similar when compared between the 0PN and 2PN groups after vitrified-warmed blastocyst transfer. However, the 0PN group had a higher birthweights, higher z scores, and a greater proportion of very large for gestational age newborns. When comparing the 1PN and 2PN groups, we found that the PR was similar whereas the AR was higher and the LBR was lower. No differences were detected in the other neonatal outcomes.

CONCLUSION(S)

The results of the present study show that the transfer of 2PN blastocysts should be prioritized because of a higher AR and a lower LBR after 1PN blastocyst transfers and a higher birthweight after 0PN blastocyst transfers when compared with 2PN blastocyst transfers. Our data indicate the need for concern about the safety of 1PN and 0PN embryo transfers.

Value of transferring embryos derived from monopronucleated (1PN) zygotes at the time of fertilization assessment

This paper is a retrospective analysis of the sole transfer of monopronucleated zygotes (1PN) embryos both in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) to determine the value of transferring embryos formed from 1PN. In fresh cycles, 1PN cleavage-stage embryos (1PN cleavage fresh) were transferred. In frozen–thawed cycles, 1PN blastocyst-stage embryos (1PN blast frozen) were transferred. We used comparison groups: for fresh cycles, 2PN cleavage-stage embryos (2PN cleavage fresh) were transferred; and for frozen–thawed cycles, 2PN blastocyst-stage embryos (2PN blast frozen) were transferred. Comparison groups were matched for cycle and patient characteristics to the 1PN group. Finally, for fresh cycles, live birth rates (LBR) in the 1PN cleavage group were significantly lower than those in 2PN cleavage group, both for IVF [LBR = 7.64% vs. pregnancy rate (PR) = 22.12%, P = 0.003, respectively] and ICSI (LBR = 0% vs. LBR = 20.00%, P < 0.001, respectively). For frozen–thawed IVF cycles, the PR in the 1PN blastocyst group were comparable with those of the 2PN blastocyst group (1PN: LBR = 33.14% vs. 2PN: LBR = 37.24%, P = 0.289, respectively), while in ICSI, the PR in the 1PN blastocyst group were lower than those in the 2PN blastocyst group (LBR = 15.25% vs. LBR = 40.68%, P = 0.002, respectively). So, for IVF, blastocyst culture was capable of selecting normal 1PN embryos for transfer and achieves satisfying outcomes. However, for ICSI, blastocyst culture was not effective enough to eliminate abnormal embryos and 1PN embryo transfer needed to be treated with caution.

Can We Engineer a Human Cardiac Patch for Therapy?

Some of the most significant leaps in the history of modern civilization-the development of article in China, the steam engine, which led to the European industrial revolution, and the era of computers-have occurred when science converged with engineering. Recently, the convergence of human pluripotent stem cell technology with biomaterials and bioengineering have launched a new medical innovation: functional human engineered tissue, which promises to revolutionize the treatment of failing organs including most critically, the heart. This compendium covers recent, state-of-the-art developments in the fields of cardiovascular tissue engineering, as well as the needs and challenges associated with the clinical use of these technologies. We have not attempted to provide an exhaustive review in stem cell biology and cardiac cell therapy; many other important and influential reports are certainly merit but already been discussed in several recent reviews. Our scope is limited to the engineered tissues that have been fabricated to repair or replace components of the heart (eg, valves, vessels, contractile tissue) that have been functionally compromised by diseases or developmental abnormalities. In particular, we have focused on using an engineered myocardial tissue to mitigate deficiencies in contractile function.

Out-of-Plane Rotation Control of Biological Cells With a Robot-Tweezers Manipulation System for Orientation-Based Cell Surgery

In many cell surgery applications, cell must be oriented properly such that the microsurgery tool can access the target components with minimum damage to the cell. In this paper, a scheme for out of image plane orientation control of suspended biological cells using robotic controlled optical tweezers is presented for orientation-based cell surgery. Based on our previous work on planar cell rotation using optical tweezers, the dynamic model of cell out-of-plane orientation control is formulated by using the T-matrix approach. Vision-based algorithms are developed to extract the cell out of image plane orientation angles, based on 2-D image slices obtained under an optical microscope. A robust feedback controller is then proposed to achieve cell out-of-plane rotation. Experiments of automated out of image plane rotational control for cell nucleus extraction surgery are performed to demonstrate the effectiveness of the proposed approach. This approach advances robot-aided single cell manipulation and produces impactful benefits to cell surgery applications such as nucleus transplantation and organelle biopsy in precision medicine.

Comparison of Teratoma Formation between Embryonic Stem Cells and Parthenogenetic Embryonic Stem Cells by Molecular Imaging

With their properties of self-renewal and differentiation, embryonic stem (ES) cells hold great promises for regenerative therapy. However, teratoma formation and ethical concerns of ES cells may restrict their potential clinical applications. Currently, parthenogenetic embryonic stem (pES) cells have attracted the interest of researchers for its self-renewing and pluripotent differentiation while eliciting less ethic concerns. In this study, we established a model with ES and pES cells both stably transfected with a double-fusion reporter gene containing renilla luciferase (Rluc) and red fluorescent protein (RFP) to analyze the mechanisms of teratoma formation. Transgenic Vegfr2-luc mouse, which expresses firefly luciferase (Fluc) under the promoter of vascular endothelial growth factor receptor 2 (Vegfr2-luc), was used to trace the growth of new blood vessel recruited by transplanted cells. Bioluminescence imaging (BLI) of Rluc/Fluc provides an effective tool in estimating the growth and angiogenesis of teratoma in vivo. We found that the tumorigenesis and angiogenesis capacity of ES cells were higher than those of pES cells, in which VEGF/VEGFR2 signal pathway plays an important role. In conclusion, pES cells have the decreased potential of teratoma formation but meanwhile have similar differentiating capacity compared with ES cells. These data demonstrate that pES cells provide an alternative source for ES cells with the risk reduction of teratoma formation and without ethical controversy.

Imprinting Status in Two Human Parthenogenetic Embryonic Stem Cell Lines: Analysis of 63 Imprinted Gene Expression Levels in Undifferentiated and Early Differentiated Stages

Human parthenogenetic embryonic stem cells (hPESCs) represent a source of histocompatible tissues for transplantation and carry two copies of the maternal genome, but lack the paternal genome. In this study, we selected 63 known human imprinted genes to investigate the imprinting status of hPESC. The expression level of these genes, including 27 maternally and 36 paternally imprinted were illustrated in hPESC and human embryonic stem cells (hESCs) derived from fertilized embryo lines. The expression activity changes of these genes were analyzed in undifferentiated and early differentiated hPESC lines. In addition, the methylation status of four differentially methylated regions (DMRs) of the imprinted genes was analyzed in undifferentiated and early differentiated hPESC and hESC lines. As a result, we found that all the maternally imprinted genes were expressed at similar levels in the undifferentiated hPESC lines and the hESC lines, except ZNF264 and ATP10A. Twenty-one analyzed paternal imprinted genes were expressed at the same level in two separated hPESC lines as well as compared with the hESC lines, whereas 15 other paternal imprinted genes were significantly downregulated or inactivated in hPESC lines as compared with the hESC line. During prolonged passage, the expression levels of the majority of imprinted genes remained stable in two hPESC lines. The four DMRs, including PEG3/ZIM2 (DMRs), SNURF/SNRPN DMRs, and KVDMR1 DMRs are highly methylated in the genes of two undifferentiated hPESCs and its embryonic bodies (EBs), whereas the genes of the undifferentiated hESCs and its EBs are half methylated. During the early differentiation stage, the imprinted genes showed the same expression trend and the expression levels of H19, IGF2, SLC22A2, SLC22A3/SLC22A18, and CPA4 were significantly upregulated in both hPESC lines. As conclusion, hPESCs show a substantial degree of epigenetic stability with respect to some imprinted genes.

Mouse Parthenogenetic Embryonic Stem Cells with Biparental-Like Expression of Imprinted Genes Generate Cortical-Like Neurons That Integrate into the Injured Adult Cerebral Cortex

One strategy for stem cell-based therapy of the cerebral cortex involves the generation and transplantation of functional, histocompatible cortical-like neurons from embryonic stem cells (ESCs). Diploid parthenogenetic Pg-ESCs have recently emerged as a promising source of histocompatible ESC derivatives for organ regeneration but their utility for cerebral cortex therapy is unknown. A major concern with Pg-ESCs is genomic imprinting. In contrast with biparental Bp-ESCs derived from fertilized oocytes, Pg-ESCs harbor two maternal genomes but no sperm-derived genome. Pg-ESCs are therefore expected to have aberrant expression levels of maternally expressed (MEGs) and paternally expressed (PEGs) imprinted genes. Given the roles of imprinted genes in brain development, tissue homeostasis and cancer, their deregulation in Pg-ESCs might be incompatible with therapy. Here, we report that, unexpectedly, only one gene out of 7 MEGs and 12 PEGs was differentially expressed between Pg-ESCs and Bp-ESCs while 13 were differentially expressed between androgenetic Ag-ESCs and Bp-ESCs, indicating that Pg-ESCs but not Ag-ESCs, have a Bp-like imprinting compatible with therapy. In vitro, Pg-ESCs generated cortical-like progenitors and electrophysiologically active glutamatergic neurons that maintained the Bp-like expression levels for most imprinted genes. In vivo, Pg-ESCs participated to the cortical lineage in fetal chimeras. Finally, transplanted Pg-ESC derivatives integrated into the injured adult cortex and sent axonal projections in the host brain. In conclusion, mouse Pg-ESCs generate functional cortical-like neurons with Bp-like imprinting and their derivatives properly integrate into both the embryonic cortex and the injured adult cortex. Collectively, our data support the utility of Pg-ESCs for cortical therapy. Stem Cells 2018;36:192-205.

Directing the Differentiation of Parthenogenetic Stem Cells into Tenocytes for Tissue-Engineered Tendon Regeneration

Uniparental parthenogenesis yields pluripotent stem cells without the political and ethical concerns surrounding the use of embryonic stem cells (ESCs) for biomedical applications. In the current study, we hypothesized that parthenogenetic stem cells (pSCs) could be directed to differentiate into tenocytes and applied for tissue‐engineered tendon. We showed that pSCs displayed fundamental properties similar to those of ESCs, including pluripotency, clonogenicity, and self‐renewal capacity. pSCs spontaneously differentiated into parthenogenetic mesenchymal stem cells (pMSCs), which were positive for mesenchymal stem cell surface markers and possessed osteogenic, chondrogenic, and adipogenic potential. Then, mechanical stretch was applied to improve the tenogenic differentiation of pMSCs, as indicated by the expression of tenogenic‐specific markers and an increasing COL1A1:3A1 ratio. The pSC‐derived tenocytes could proliferate and secrete extracellular matrix on the surface of poly(lactic‐co‐glycolic) acid scaffolds. Finally, engineered tendon‐like tissue was successfully generated after in vivo heterotopic implantation of a tenocyte‐scaffold composite. In conclusion, our experiment introduced an effective and practical strategy for applying pSCs for tendon regeneration. Stem Cells Translational Medicine2017;6:196–208

Pronuclear removal of tripronuclear zygotes can establish heteroparental normal karyotypic human embryonic stem cells

PURPOSE

This study aimed to derive heteroparental normal karyotypic human embryonic stem cells (hESCs) from microsurgically corrected tripronuclear (3PN) zygotes.

METHODS

After sequential culture for 5-6 days, embryos developed from microsurgically corrected 3PN zygotes were analyzed by fluorescence in situ hybridization (FISH) using probes for chromosomes 17, X and Y. Intact 3PN zygotes from clinical in vitro fertilization (IVF) cycles were cultured as the control group. The inner cell mass (ICM) of blastocysts that developed from microsurgically corrected 3PN zygotes was used to derive hESC lines, and the stem cell characteristics of these lines were evaluated. G-banding analysis was adopted to identify the karyotype of the hESC line, and the heteroparental inheritance of the hESC line was analyzed by DNA fingerprinting analysis.

RESULTS

The blastocyst formation rate (13.5 %) of the microsurgically corrected 3PN zygotes was significantly higher (P < 0.05) than that of intact 3PN zygotes (8.7 %). The diploid rate of the blastocysts (55.0 %) was significantly higher (P < 0.05) than that of the arrested cleavage-stage embryos (18.4 %) in microsurgically corrected 3PN zygotes. The triploid rate of the microsurgically corrected 3PN zygotes (5.7 %) was significantly lower (P < 0.01) than that of intact 3PN zygotes (19.4 %). Furthermore, we established one heteroparental normal karyotypic hESC line from the microsurgically corrected tripronuclear zygotes.

CONCLUSIONS

Pronuclear removal can effectively remove the surplus chromosome set of 3PN zygotes. A combination of pronuclear removal and blastocyst culture enables the selection of diploidized blastocysts from which heteroparental normal karyotypic hESC lines can be derived.

Chromosomal instability in mammalian pre-implantation embryos: potential causes, detection methods, and clinical consequences

Formation of a totipotent blastocyst capable of implantation is one of the first major milestones in early mammalian embryogenesis, but less than half of in vitro fertilized embryos from most mammals will progress to this stage of development. Whole chromosomal abnormalities, or aneuploidy, are key determinants of whether human embryos will arrest or reach the blastocyst stage. Depending on the type of chromosomal abnormality, however, certain embryos still form blastocysts and may be morphologically indistinguishable from chromosomally normal embryos. Despite the implementation of pre-implantation genetic screening and other advanced in vitro fertilization (IVF) techniques, the identification of aneuploid embryos remains complicated by high rates of mosaicism, atypical cell division, cellular fragmentation, sub-chromosomal instability, and micro-/multi-nucleation. Moreover, several of these processes occur in vivo following natural human conception, suggesting that they are not simply a consequence of culture conditions. Recent technological achievements in genetic, epigenetic, chromosomal, and non-invasive imaging have provided additional embryo assessment approaches, particularly at the single-cell level, and clinical trials investigating their efficacy are continuing to emerge. In this review, we summarize the potential mechanisms by which aneuploidy may arise, the various detection methods, and the technical advances (such as time-lapse imaging, "-omic" profiling, and next-generation sequencing) that have assisted in obtaining this data. We also discuss the possibility of aneuploidy resolution in embryos via various corrective mechanisms, including multi-polar divisions, fragment resorption, endoreduplication, and blastomere exclusion, and conclude by examining the potential implications of these findings for IVF success and human fecundity.

Chromosomal Abnormalities in Embryonic and Somatic Stem Cells

The potential use of stem cells (SCs) for tissue engineering, regenerative medicine, disease modeling, toxicological studies, drug delivery, and as in vitro model for the study of basic developmental processes implies large-scale in vitro culture. Here, after a brief description of the main techniques used for karyotype analysis, we will give a detailed overview of the chromosome abnormalities described in pluripotent (embryonic and induced pluripotent SCs) and somatic SCs, and the possible causes of their origin during culture.

Establishment of Homozygote Mutant Human Embryonic Stem Cells by Parthenogenesis

We report on the derivation of a diploid 46(XX) human embryonic stem cell (HESC) line that is homozygous for the common deletion associated with Spinal muscular atrophy type 1 (SMA) from a pathenogenetic embryo. By characterizing the methylation status of three different imprinted loci (MEST, SNRPN and H19), monitoring the expression of two parentally imprinted genes (SNRPN and H19) and carrying out genome-wide SNP analysis, we provide evidence that this cell line was established from the activation of a mutant oocyte by diploidization of the entire genome. Therefore, our SMA parthenogenetic HESC (pHESC) line provides a proof-of-principle for the establishment of diseased HESC lines without the need for gene manipulation. As mutant oocytes are easily obtained and readily available during preimplantation genetic diagnosis (PGD) cycles, this approach should provide a powerful tool for disease modelling and is especially advantageous since it can be used to induce large or complex mutations in HESCs, including gross DNA alterations and chromosomal rearrangements, which are otherwise hard to achieve.

Ascorbic acid improves pluripotency of human parthenogenetic embryonic stem cells through modifying imprinted gene expression in the Dlk1-Dio3 region

Introduction

Human parthenogenetic embryonic stem cells (hpESCs) are generated from artificially activated oocytes, however, the issue of whether hpESCs have equivalent differentiation ability to human fertilized embryonic stem cells remains controversial.

Methods

hpESCs were injected into male severe combined immunodeficiency (SCID) mice and the efficiency of teratoma formation was calculated. Then the gene expression and methylation modification were detected by real time-PCR and bisulfate methods.

Results

Comparison of five hpESCs with different differentiation abilities revealed that levels of paternal genes in the Dlk1-Dio3 region on chromosome 14 in the hpESCs with high differentiation potential are enhanced, but strictly methylated and silenced in the hpESCs with lower differentiation potential. Treatment with ascorbic acid, rescued their ability to support teratoma formation and altered the expression profiles of paternally expressed genes in hpESCs that could not form teratoma easily. No differences in the expression of other imprinting genes were evident between hpESCs with higher and lower differentiation potential, except for those in the Dlk1-Dio3 region.

Conclusions

The Dlk1-Dio3 imprinting gene cluster distinguishes the differentiation ability of hpESCs. Moreover, modification by ascorbic acid may facilitate application of hpESCs to clinical settings in the future by enhancing their pluripotency.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0054-9) contains supplementary material, which is available to authorized users.

Activin A can induce definitive endoderm differentiation from human parthenogenetic embryonic stem cells

OBJECTIVES

As activin/nodal signaling plays a key role in definitive endoderm (DE) differentiation, we have explored activin A-induced differentiation of DE from human parthenogenetic embryonic stem cells (hPESCs).

RESULTS

Administration of 5 ng activin A/ml had no effect on the expression of markers of DE differentiation. However, higher concentrations of activin A (50 and 100 ng/ml) upregulated Sox17 and Cxcr4, as well upregulating the mesendodermal precursor marker, Brachyury.

CONCLUSIONS

These findings demonstrate that low dose activin A can maintain the undifferentiated potency of hPESCs, whereas higher doses induce DE differentiation; 50 ng/ml is the optimal concentration for inducing DE from hPESCs.

Human Parthenogenetic Embryonic Stem Cell-Derived Neural Stem Cells Express HLA-G and Show Unique Resistance to NK Cell-Mediated Killing

Parent-of-origin imprints have been implicated in the regulation of neural differentiation and brain development. Previously we have shown that, despite the lack of a paternal genome, human parthenogenetic (PG) embryonic stem cells (hESCs) can form proliferating neural stem cells (NSCs) that are capable of differentiation into physiologically functional neurons while maintaining allele-specific expression of imprinted genes. Since biparental ("normal") hESC-derived NSCs (N NSCs) are targeted by immune cells, we characterized the immunogenicity of PG NSCs. Flow cytometry and immunocytochemistry revealed that both N NSCs and PG NSCs exhibited surface expression of human leukocyte antigen (HLA) class I but not HLA-DR molecules. Functional analyses using an in vitro mixed lymphocyte reaction assay resulted in less proliferation of peripheral blood mononuclear cells (PBMC) with PG compared with N NSCs. In addition, natural killer (NK) cells cytolyzed PG less than N NSCs. At a molecular level, expression analyses of immune regulatory factors revealed higher HLA-G levels in PG compared with N NSCs. In line with this finding, MIR152, which represses HLA-G expression, is less transcribed in PG compared with N cells. Blockage of HLA-G receptors ILT2 and KIR2DL4 on natural killer cell leukemia (NKL) cells increased cytolysis of PG NSCs. Together this indicates that PG NSCs have unique immunological properties due to elevated HLA-G expression.

Directing parthenogenetic stem cells differentiate into adipocytes for engineering injectable adipose tissue

The selection of appropriate seed cells is crucial for adipose tissue engineering. Here, we reported the stepwise induction of parthenogenetic embryonic stem cells (pESCs) to differentiate into adipogenic cells and its application in engineering injectable adipose tissue with Pluronic F-127. pESCs had pluripotent differentiation capacity and could form teratomas that include the three primary germ layers. Cells that migrated from the embryoid bodies (EBs) were selectively separated and expanded to obtain embryonic mesenchymal stem cells (eMSCs). The eMSCs exhibited similar cell surface marker expression profiles with bone morrow mesenchymal stem cells (BMSCs) and had multipotent differentiation capacity. Under the induction of dexamethasone, indomethacin, and insulin, eMSCs could differentiate into adipogenic cells with increased expression of adipose-specific genes and oil droplet depositions within the cytoplasm. To evaluate their suitability as seed cells for adipose tissue engineering, the CM-Dil labelled adipogenic cells derived from eMSCs were seeded into Pluronic F-127 hydrogel and injected subcutaneously into nude mice. Four weeks after injection, glistering and semitransparent constructs formed in the subcutaneous site. Histological observations demonstrated that new adipose tissue was successfully fabricated in the specimen by the labelled cells. The results of the current study indicated that pESCs have great potential in the fabrication of injectable adipose tissue.

X chromosome inactivation in human parthenogenetic embryonic stem cells following prolonged passaging

The present study aimed to investigate the X chrochromosome inactivation (XCI) status in long-term cultured human parthenogenetic embryonic stem cells. One human embryonic stem (hES) cell line and 2 human parthenogenetic embryonic stem (hPES) cell lines were subjected to long-term culture in vitro (>50 passages). Karyotyping, array-based comparative genomic hybridization (aCGH), X-inactive specific transcript (XIST) RNA, immunofluorescence staining and real-time PCR were used to assess the chromosome karyotypes of these cells and the XCI status. X chromosome microdeletion was observed in the hPES-2 cells following culture for 50 passages. As early as 20 passages, XIST RNA expression was detected in the hPES-2 cells and was followed by low X-linked gene expression. The XIST RNA expression level was higher in the differentiated hPES-2 cells. The hPES-2′ cells that were subclones of hPES-2 retained the XCI status, and had low XIST and X-linked gene expression. XIST RNA expression remained at a low level in the differentiated hPES-2′ cells. The human biparental embryonic stem (hBES)-1 and hPES-1 cells did not exhibit XCI, and the differentiated hPES-1 cells had high expression levels of XIST RNA. In conclusion, the chromosome karyotypes of some hPES cell lines revealed instabilities. Similar to the hES cells, the hPES cells exhibited 3 XCI statuses. The unstable XCI status of the hPES-2 line may have been related to chromosome instability. These unstable chromosomes renedered these cells susceptible to environmental conditions and freezing processes, which may be the result of environmental adaptations.

Inducing human parthenogenetic embryonic stem cells into islet‑like clusters

In order to determine whether human parthenogenetic embryonic stem (hpES) cells have the potential to differentiate into functional cells, a modified four-step protocol was used to induce the hpES cells into islet-like clusters (ILCs) in vitro. Growth factors activin A, retinoic acid, nicotinamide, Exendin-4 and betacellulin were added sequentially to the hpES cells at each step. The terminally differentiated cells were shown to gather into ILCs. Immunohistochemistry and semi quantitative polymerase chain reaction analyses demonstrated that the ILCs expressed islet specific hormones and functional markers. Furthermore, an insulin release test indicated that the clusters had the same physiological function as islets. The ILCs derived from hpES cells shared similar characteristics with islets. These results indicate that hpES cell-derived ILCs may be used as reliable material for the treatment of type I diabetes mellitus.

Concise review: parthenote stem cells for regenerative medicine: genetic, epigenetic, and developmental features

Embryonic stem cells (ESCs) have the potential to provide unlimited cells and tissues for regenerative medicine. ESCs derived from fertilized embryos, however, will most likely be rejected by a patient's immune system unless appropriately immunomatched. Pluripotent stem cells (PSCs) genetically identical to a patient can now be established by reprogramming of somatic cells. However, practical applications of PSCs for personalized therapies are projected to be unfeasible because of the enormous cost and time required to produce clinical-grade cells for each patient. ESCs derived from parthenogenetic embryos (pESCs) that are homozygous for human leukocyte antigens may serve as an attractive alternative for immunomatched therapies for a large population of patients. In this study, we describe the biology and genetic nature of mammalian parthenogenesis and review potential advantages and limitations of pESCs for cell-based therapies.

Research with parthenogenetic stem cells will help decide whether a safer clinical use is possible

The derivation and use of parthenogenetic stem cells (pESCs) are envisaged as a reliable alternative to conventional embryonic stem cells. Similar to embryonic stem cells in their proliferation, expression of pluripotency markers and capacity to multilineage differentiation, pESCs are at a lower risk of immune rejection within stem cell-based therapeutics. Moreover, pESCs represent an important model system to study the effect of paternally imprinted genes on cell differentiation. However, currently available information about the genetic and epigenetic behaviour of pESCs is limited. Thus, a detailed look at the biology of parthenogenetic (PG) embryos and PG-derived cell lines would allow gaining insight into the full potential of pESC in biotechnology. In this commentary article we review some features related to the biology of PG embryos and pESCs. In addition, novel traits on bovine pESCs (bpESCs) are discussed.

Centrosome amplification and chromosomal instability in human and animal parthenogenetic cell lines

Parthenotes have been proposed as a source of embryonic stem cells but they lack the centriole which is inherited through the sperm in all mammalian species, except for rodents. We investigated the centrosome of parthenotes and parthenogenetic embryonic stem cells using parthenogenetic and biparental pig pre-implantation embryos, human and pig parthenogenetic and biparental embryonic stem cells, sheep fibroblasts derived from post implantation parthenogenetic and biparental embryos developed in vivo. We also determined the level of aneuploidy in parthenogenetic cells. Oocytes of all species were activated using ionomycin and 6-dimethylaminopurine (6-DMAP). Over 60% of parthenogenetic blastomeres were affected by an excessive number of centrioles. Centrosome amplification, was observed by microscopical and ultrastructural analysis also in parthenogenetic cell lines of all three species. Over expression of PLK2 and down regulation of CCNF, respectively involved in the stimulation and inhibition of centrosome duplication, were present in all species. We also detected down regulation of spindle assembly checkpoint components such as BUB1, CENPE and MAD2. Centrosome amplification was accompanied by multipolar mitotic spindles and all cell lines were affected by a high rate of aneuploidy. These observations indicate a link between centrosome amplification and the high incidence of aneuploidy and suggest that parthenogenetic stem cells may be a useful model to investigate how aneuploidy can be compatible with cell proliferation and differentiation.

Parthenogenetic stem cells for tissue-engineered heart repair

Uniparental parthenotes are considered an unwanted byproduct of in vitro fertilization. In utero parthenote development is severely compromised by defective organogenesis and in particular by defective cardiogenesis. Although developmentally compromised, apparently pluripotent stem cells can be derived from parthenogenetic blastocysts. Here we hypothesized that nonembryonic parthenogenetic stem cells (PSCs) can be directed toward the cardiac lineage and applied to tissue-engineered heart repair. We first confirmed similar fundamental properties in murine PSCs and embryonic stem cells (ESCs), despite notable differences in genetic (allelic variability) and epigenetic (differential imprinting) characteristics. Haploidentity of major histocompatibility complexes (MHCs) in PSCs is particularly attractive for allogeneic cell-based therapies. Accordingly, we confirmed acceptance of PSCs in MHC-matched allotransplantation. Cardiomyocyte derivation from PSCs and ESCs was equally effective. The use of cardiomyocyte-restricted GFP enabled cell sorting and documentation of advanced structural and functional maturation in vitro and in vivo. This included seamless electrical integration of PSC-derived cardiomyocytes into recipient myocardium. Finally, we enriched cardiomyocytes to facilitate engineering of force-generating myocardium and demonstrated the utility of this technique in enhancing regional myocardial function after myocardial infarction. Collectively, our data demonstrate pluripotency, with unrestricted cardiogenicity in PSCs, and introduce this unique cell type as an attractive source for tissue-engineered heart repair.

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

Parthenogenetic embryonic stem cells have pluripotent differentiation potentials, akin to fertilized embryo-derived embryonic stem cells. The aim of this study was to compare the neuronal differentiation potential of parthenogenetic and fertilized embryo-derived embryonic stem cells. Before differentiation, karyotype analysis was performed, with normal karyotypes detected in both parthenogenetic and fertilized embryo-derived embryonic stem cells. Sex chromosomes were identified as XX. Immunocytochemistry and quantitative real-time PCR detected high expression of the pluripotent gene, Oct4, at both the mRNA and protein levels, indicating pluripotent differentiation potential of the two embryonic stem cell subtypes. Embryonic stem cells were induced with retinoic acid to form embryoid bodies, and then dispersed into single cells. Single cells were differentiated in N2 differentiation medium for 9 days. Immunocytochemistry showed parthenogenetic and fertilized embryo-derived embryonic stem cells both express the neuronal cell markers nestin, βIII-tubulin and myelin basic protein. Quantitative real-time PCR found expression of neurogenesis related genes (Sox-1, Nestin, GABA, Pax6, Zic5 and Pitx1) in both types of embryonic stem cells, and Oct4 expression was significantly decreased. Nestin and Pax6 expression in parthenogenetic embryonic stem cells was significantly higher than that in fertilized embryo-derived embryonic stem cells. Thus, our experimental findings indicate that parthenogenetic embryonic stem cells have stronger neuronal differentiation potential than fertilized embryo-derived embryonic stem cells.

Substrates and supplements for hESCs: a critical review

BACKGROUND

Different laboratories around the world have succeeded in establishing human embryonic stem cell (hESC) lines. However, culture conditions vary considerably among the protocols used and the vast majority of the lines at some stage of their creation have been in contact with an animal derived component. One of the main problems to be overcome for the generation of a clinical-grade hESC line is the choice of a substrate and medium that allows derivation and culture, where animal derived components are kept to a minimum or completely excluded.

MATERIALS AND METHODS

The following review describes past and more recent achievements in the creation and culturing of hESC. It describes protocols, giving special attention to the matrices and supplements used for derivation, maintainance and cryostorage, considering whether they included defined, undefined and/or animal-derived components in their formulations.

CONCLUSION

This information shall be useful for the creation and choice of new substrates and supplements for future research in the field of hESC for therapeutic purposes.

Present and future cell therapies for pancreatic beta cell replenishment

If only at a small scale, islet transplantation has successfully addressed what ought to be the primary endpoint of any cell therapy: the functional replenishment of damaged tissue in patients. After years of less-than-optimal approaches to immunosuppression, recent advances consistently yield long-term graft survival rates comparable to those of whole pancreas transplantation. Limited organ availability is the main hurdle that stands in the way of the widespread clinical utilization of this pioneering intervention. Progress in stem cell research over the past decade, coupled with our decades-long experience with islet transplantation, is shaping the future of cell therapies for the treatment of diabetes. Here we review the most promising avenues of research aimed at generating an inexhaustible supply of insulin-producing cells for islet regeneration, including the differentiation of pluripotent and multipotent stem cells of embryonic and adult origin along the beta cell lineage and the direct reprogramming of non-endocrine tissues into insulin-producing cells.

Implications of aneuploidy for stem cell biology and brain therapeutics

Understanding the cellular basis of neurological disorders have advanced at a slow pace, especially due to the extreme invasiveness of brain biopsying and limitations of cell lines and animal models that have been used. Since the derivation of pluripotent stem cells (PSCs), a novel source of cells for regenerative medicine and disease modeling has become available, holding great potential for the neurology field. However, safety for therapy and accurateness for modeling have been a matter of intense debate, considering that genomic instability, including the gain and loss of chromosomes (aneuploidy), has been repeatedly observed in those cells. Despite the fact that recent reports have described some degree of aneuploidy as being normal during neuronal differentiation and present in healthy human brains, this phenomenon is particularly controversial since it has traditionally been associated with cancer and disabling syndromes. It is therefore necessary to appreciate, to which extent, aneuploid pluripotent stem cells are suitable for regenerative medicine and neurological modeling and also the limits that separate constitutive from disease-related aneuploidy. In this review, recent findings regarding chromosomal instability in PSCs and within the brain will be discussed.

Recent advances in bone tissue engineering scaffolds

Bone disorders are of significant concern due to increase in the median age of our population. Traditionally, bone grafts have been used to restore damaged bone. Synthetic biomaterials are now being used as bone graft substitutes. These biomaterials were initially selected for structural restoration based on their biomechanical properties. Later scaffolds were engineered to be bioactive or bioresorbable to enhance tissue growth. Now scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous, made of biodegradable materials that harbor different growth factors, drugs, genes, or stem cells. In this review, we highlight recent advances in bone scaffolds and discuss aspects that still need to be improved.

Functional neuronal cells generated by human parthenogenetic stem cells

Parent of origin imprints on the genome have been implicated in the regulation of neural cell type differentiation. The ability of human parthenogenetic (PG) embryonic stem cells (hpESCs) to undergo neural lineage and cell type-specific differentiation is undefined. We determined the potential of hpESCs to differentiate into various neural subtypes. Concurrently, we examined DNA methylation and expression status of imprinted genes. Under culture conditions promoting neural differentiation, hpESC-derived neural stem cells (hpNSCs) gave rise to glia and neuron-like cells that expressed subtype-specific markers and generated action potentials. Analysis of imprinting in hpESCs and in hpNSCs revealed that maternal-specific gene expression patterns and imprinting marks were generally maintained in PG cells upon differentiation. Our results demonstrate that despite the lack of a paternal genome, hpESCs generate proliferating NSCs that are capable of differentiation into physiologically functional neuron-like cells and maintain allele-specific expression of imprinted genes. Thus, hpESCs can serve as a model to study the role of maternal and paternal genomes in neural development and to better understand imprinting-associated brain diseases.

Higher copy number variation and diverse X chromosome inactivation in parthenote-derived human embryonic stem cells

Parthenote-derived human embryonic stem cells (phESCs) have many advantages over conventionally derived human embryonic stem cells (hESCs), but a more thorough investigation of these cells is needed before they can be implemented in cell therapies. In this work, we used a Cytogenetics Whole-Genome Array to study the copy number variation (CNV) status in phESCs and hESCs. We also investigated X chromosome inactivation (XCI) and expression levels of marker genes in these cells. More CNVs were found in phESCs than in hESCs in the present study, and gene expression appeared to be associated with the gain or loss of CNVs. In addition, a variable XCI status and different expression pattern of paternally expressed imprinted gene were also found in phESCs. In conclusion, although phESCs had a similar pluripotent profile to conventionally derived hESCs, these cells differed in imprinted gene expression, XCI status and number of CNVs. Our work highlights the need for a deeper investigation to elucidate the genetic and epigenetic characteristics of these cells.

Accumulation of instability in serial differentiation and reprogramming of parthenogenetic human cells

Human leukocyte antigen-homozygous parthenogenetic stem cells (pSC) could provide a source of progenitors for regenerative medicine, lowering the need for immune suppression in patients. However, the high level of homozygosis and the lack of a paternal genome might pose a safety challenge for their therapeutic use, and no study so far has evaluated the spread and significance of gene expression changes across serial potency changes in these cells. We performed serial rounds of differentiation and reprogramming to assess pSC gene expression stability, likely of epigenetic source. We first derived pSC from activated MII oocytes, and differentiated them to parthenogenetic mesenchymal stem cells (pMSC). We then proceeded to induce pluripotency in pMSC by over expression of the four transcription factors Oct4, Sox2, Klf4 and c-Myc. pMSC-derived iPS (piPS) were further differentiated into secondary pMSC (pMSC-II). At every potency change, we characterized the obtained lines both molecularly and by functional differentiation, and performed an extensive genome-wide expression study by microarray analysis. Although overall gene expression of parthenogenetic cells resembled that of potency-matched biparental lines, significantly broader changes were brought about upon secondary differentiation of piPS to pMSC-II compared with matched biparental controls; our results highlight the effect of the interplay of epigenetic reprogramming on a monoparental background, as well as the importance of heterozygosis and biparental imprinting for stable epigenetic reprogramming.

Histocompatible parthenogenetic embryonic stem cells as a potential source for regenerative medicine

Parthenogenesis is the process by which an oocyte develops into an embryo without fertilization. Parthenogenetic activation can be performed at various stages of meiosis, yielding embryos with a distinct genetic pattern of homozygousity and heterozygousity. The heterozygousity pattern specific to parthenogenetic embryonic stem (pES) cells derived from such embryos, can be predicted using genome-wide single nucleotide polymorphism (SNP) analysis to determine whether extrusion of the first or second polar body is prohibited. The heterozygous pES cells carrying the full complement of major histocompatibility complex (MHC) antigen matched to the oocyte donor, could therefore provide a potential source of MHC matched cells or tissue for cell replacement therapy. In this review, we summarized the mechanism of deriving heterozygous MHC-matched pES cells using a mouse and human models.

Developmental incompatibility of human parthenogenetic embryonic stem cells in mouse blastocysts

Human parthenogenetic embryonic stem (pES) cells can be clinically used in the future to avoid immunological rejection. However, the developmental potential of human pES cells remains to be elucidated. In this study, we generated a human pES-enhanced green fluorescent protein (EGFP) cell line (chHES-32-EGFP), which shows pluripotency thus far and maintains stable and robust EGFP expression in the undifferentiated and differentiated states in vivo and in vitro. Using this pES-EGFP cell line, we found that when human pES-EGFP cells were injected into mice blastocysts, EGFP-positive cells progressively decreased with the development of blastocysts in vitro. Only 4 out of 23 embryos (17.4%) contained EGFP-positive cells and all of these embryos exhibited abnormal morphology or delayed development when the chimera blastocysts were implanted into the pseudopregnant recipient mouse uterus. These results raise serious questions regarding the feasibility of the generation of interspecific chimeras between mouse blastocysts and human pES cells.

Immunological considerations for embryonic and induced pluripotent stem cell banking

Recent advances in stem cell technology have generated enthusiasm for their potential to study and treat a diverse range of human disease. Pluripotent human stem cells for therapeutic use may, in principle, be obtained from two sources: embryonic stem cells (hESCs), which are capable of extensive self-renewal and expansion and have the potential to differentiate into any somatic tissue, and induced pluripotent stem cells (iPSCs), which are derived from differentiated tissue such as adult skin fibroblasts and appear to have the same properties and potential, but their generation is not dependent upon a source of embryos. The likelihood that clinical transplantation of hESC- or iPSC-derived tissues from an unrelated (allogeneic) donor that express foreign human leucocyte antigens (HLA) may undergo immunological rejection requires the formulation of strategies to attenuate the host immune response to transplanted tissue. In clinical practice, individualized iPSC tissue derived from the intended recipient offers the possibility of personalized stem cell therapy in which graft rejection would not occur, but the logistics of achieving this on a large scale are problematic owing to relatively inefficient reprogramming techniques and high costs. The creation of stem cell banks comprising HLA-typed hESCs and iPSCs is a strategy that is proposed to overcome the immunological barrier by providing HLA-matched (histocompatible) tissue for the target population. Estimates have shown that a stem cell bank containing around 10 highly selected cell lines with conserved homozygous HLA haplotypes would provide matched tissue for the majority of the UK population. These simulations have practical, financial, political and ethical implications for the establishment and design of stem cell banks incorporating cell lines with HLA types that are compatible with different ethnic populations throughout the world.

Parthenogenesis in mammals: pros and cons in pluripotent cell derivation

Embryonic stem cells (ESCs) represent a useful tool for cell therapy studies, however the use of embryos for their derivation give rise to ethical, religious and legal problems when applied to the human. During the last years parthenogenesis has been proposed as an alternative source to obtain ESCs. Based on the fact that parthenotes avoid many concerns surrounding the “ad hoc” in vitro production and following destruction of viable human embryos. Unfortunately many aspects related to parthenogenetic cell biology are not fully understood and still need to be elucidated. In this review we describe advantages and limits of these cells. We discuss their typical ESC morphology and high telomerase activity, which disappears after differentiation. We examine the pluripotency signature that they share with bi-parental ESCs. We review their high differentiation plasticity that allow for the derivation of several mature cell type populations when we expose these cells to adequate conditions. On the other hand, in-depth analysis demonstrated chromosome mal-segregation and altered mechanisms controlling centriole arrangement and mitotic spindle formation in these cells. We hypothesize their monoparental origin as one of the possible cause of these anomalies and suggest a great caution if a therapeutic use is considered.

The promise of human embryonic stem cells in aging-associated diseases

Aging-associated diseases are often caused by progressive loss or dysfunction of cells that ultimately affect the overall function of tissues and organs. Successful treatment of these diseases could benefit from cell-based therapy that would regenerate lost cells or otherwise restore tissue function. Human embryonic stem cells (hESCs) promise to be an important therapeutic candidate in treating aging-associated diseases due to their unique capacity for self-renewal and pluripotency. To date, there are numerous hESC lines that have been developed and characterized. We will discuss how hESC lines are derived, their molecular and cellular properties, and how their ability to differentiate into all three embryonic germ layers is determined. We will also outline the methods currently employed to direct their differentiation into populations of tissue-specific, functional cells. Finally, we will highlight the general challenges that must be overcome and the strategies being developed to generate highly-purified hESC-derived cell populations that can safely be used for clinical applications.

Derivation of high-purity definitive endoderm from human parthenogenetic stem cells using an in vitro analog of the primitive streak

Human parthenogenetic stem cells (hpSCs) are pluripotent stem cells with enormous potential as cell sources for cell-based therapies: hpSCs may have histocompatibilty advantages over human embryonic stem cells (hESCs) and derivation of hpSCs does not require viable blastocyst destruction. For translation of all pluripotent stem cell-based therapies, derivation of differentiated cell products that are not contaminated with undifferentiated cells is a major technical roadblock. We report here a novel method to derive high-purity definitive endoderm (DE) from hpSCs, based on reproducing features of the normal human embryonic microenvironment. The method mimics the developmental process of transition through a primitive streak, using a differentiation device that incorporates a three-dimensional extracellular matrix (ECM) combined with a porous membrane. Treatment of undifferentiated hpSCs above the membrane results an epithelial-to-mesenchymal transition (EMT); thus, responsive cells acquire the ability to migrate through the membrane into the ECM, where they differentiate into DE. Importantly, the resultant DE is highly purified, and is not contaminated by undifferentiated cells, as assessed by OCT4 expression using immunocytochemistry and flow cytometry. The functional properties of the DE are also preserved by the process: DE differentiated in the device can generate a highly enriched population of hepatocyte-like cells (HLCs) characterized by expression of hepatic lineage markers, indocyanine green clearance, glycogen storage, cytochrome P450 activity, and engraftment in the liver after transplantation into immunodeficient mice. The method is broadly applicable and we obtained purified DE using hESCs, as well as several hpSC lines. The novel method described here represents a significant step toward the efficient generation of high-purity cells derived from DE, including hepatocytes and pancreatic endocrine cells, for use in regenerative medicine and drug discovery, as well as a platform for studying cell fate specification and behavior during development.