Preimplantation human embryos and embryonic stem cells show comparable expression of stage-specific embryonic antigens

Human tendon stem cells better maintain their stemness in hypoxic culture conditions

Tissues and organs in vivo are under a hypoxic condition; that is, the oxygen tension is typically much lower than in ambient air. However, the effects of such a hypoxic condition on tendon stem cells, a recently identified tendon cell, remain incompletely defined. In cell culture experiments, we subjected human tendon stem cells (hTSCs) to a hypoxic condition with 5% O₂, while subjecting control cells to a normaxic condition with 20% O₂. We found that hTSCs at 5% O₂ had significantly greater cell proliferation than those at 20% O₂. Moreover, the expression of two stem cell marker genes, Nanog and Oct-4, was upregulated in the cells cultured in 5% O₂. Finally, in cultures under 5% O₂, more hTSCs expressed the stem cell markers nucleostemin, Oct-4, Nanog and SSEA-4. In an in vivo experiment, we found that when both cell groups were implanted with tendon-derived matrix, more tendon-like structures formed in the 5% O₂ treated hTSCs than in 20% O₂ treated hTSCs. Additionally, when both cell groups were implanted with Matrigel, the 5% O₂ treated hTSCs showed more extensive formation of fatty, cartilage-like and bone-like tissues than the 20% O₂ treated cells. Together, the findings of this study show that oxygen tension is a niche factor that regulates the stemness of hTSCs, and that less oxygen is better for maintaining hTSCs in culture and expanding them for cell therapy of tendon injuries.

Improved methods for reprogramming human dermal fibroblasts using fluorescence activated cell sorting

Current methods to derive induced pluripotent stem cell (iPSC) lines from human dermal fibroblasts by viral infection rely on expensive and lengthy protocols. One major factor contributing to the time required to derive lines is the ability of researchers to identify fully reprogrammed unique candidate clones from a mixed cell population containing transformed or partially reprogrammed cells and fibroblasts at an early time point post infection. Failure to select high quality colonies early in the derivation process results in cell lines that require increased maintenance and unreliable experimental outcomes. Here, we describe an improved method for the derivation of iPSC lines using fluorescence activated cell sorting (FACS) to isolate single cells expressing the cell surface marker signature CD13^NEGSSEA4^POSTra-1-60^POS on day 7–10 after infection. This technique prospectively isolates fully reprogrammed iPSCs, and depletes both parental and “contaminating” partially reprogrammed fibroblasts, thereby substantially reducing the time and reagents required to generate iPSC lines without the use of defined small molecule cocktails. FACS derived iPSC lines express common markers of pluripotency, and possess spontaneous differentiation potential in vitro and in vivo. To demonstrate the suitability of FACS for high-throughput iPSC generation, we derived 228 individual iPSC lines using either integrating (retroviral) or non- integrating (Sendai virus) reprogramming vectors and performed extensive characterization on a subset of those lines. The iPSC lines used in this study were derived from 76 unique samples from a variety of tissue sources, including fresh or frozen fibroblasts generated from biopsies harvested from healthy or disease patients.

Is stage-specific embryonic antigen 4 a marker for human ductal stem/progenitor cells?

The presence of pancreatic stem cells (PnSCs) has not been firmly demonstrated in the human or animal pancreas. Previous reports have suggested that ductal and acinar structures in the exocrine pancreas can be a potential source of progenitor cells. More recently, immature insulin precursors in the periphery of human islets have been found to self-replicate and differentiate to endocrine cells in vitro. Transplantation of these cells under the kidney capsule improves the diabetic state in mice. The controversy surrounding where PnSCs reside could be resolved if a specific marker were to be found that allowed their identification, purification, and directed differentiation to endocrine cells. We have identified in human pancreas cells positive for the stage-specific embryonic antigen 4 (SSEA4), a stem cell marker. These cells also express ductal, pancreatic progenitor, and stem cell protein markers. Interestingly, some of the SSEA4(+) cells scattered in the ducts do not show a ductal cell phenotype. SSEA4(+)-sorted cells formed aggregate-like spheres in culture and robustly differentiated to pancreatic hormone-expressing cells in conditions of high glucose concentration and B27 supplementation. We hypothesize that SSEA4(+) cells or a subpopulation of those cells residing in the pancreatic ducts may be the elusive PnSCs, and in this case, SSEA4 may represent a potential surface antigen marker for human PnSCs. The discovery of specific markers for the identification and purification of human PnSCs would greatly facilitate studies aimed at the expansion of these cells and the development of targeting tools for their potential induction to insulin-producing cells.

Human skin cells that express stage-specific embryonic antigen 3 associate with dermal tissue regeneration

Stage-specific embryonic antigen 3 (SSEA3) is a glycosphingolipid that has previously been used to identify cells with stem cell-like, multipotent, and pluripotent characteristics. A rare subpopulation of SSEA3-expressing cells exists in the dermis of adult human skin. These SSEA3-expressing cells undergo a significant increase in cell number in response to injury, suggesting a possible role in regeneration. These SSEA3-expressing regeneration-associated (SERA) cells were derived through primary cell culture, purified by fluorescence-activated cell sorting (FACS), and characterized. Longer in vitro culture of the primary skin cells led to lower SSEA3 expression stability after FACS-based purification, suggesting that the current culture conditions may need to be optimized to permit the large-scale expansion of SERA cells. The SERA cells demonstrated a global transcriptional state that was most similar to bone marrow- and fat-derived mesenchymal stem cells (MSCs), and the highest expressing SSEA3-expressing cells co-expressed CD105 (clone 35). However, while a rare population of MSCs was observed in primary human skin cell cultures that could differentiate into adipocytes, osteoblasts, or chondrocytes, SERA cells did not possess this differentiation capacity, suggesting that there are at least two different rare subpopulations in adult human skin primary cultures. The identification, efficient purification, and large-scale expansion of these rare subpopulations (SERA cells and MSCs) from heterogeneous adult human skin primary cell cultures may have applications for future patient-specific cellular therapies.

Identification of aberrant methylation regions in neuroblastoma by screening of tissue-specific differentially methylated regions

BACKGROUND

The identification of tissue-specific differentially methylated regions (tDMRs) is key to our understanding of mammalian development. Research has indicated that tDMRs are aberrantly methylated in cancer and may affect the oncogenic process.

PROCEDURE

We used the MassARRAY EpiTYPER system to determine the quantitative methylation levels of seven neuroblastomas (NBs) and two control adrenal medullas at 12 conserved tDMRs. A second sample set of 19 NBs was also analyzed. Statistical analysis was carried out to determine the relationship of the quantitative methylation levels to other prognostic factors in these sample sets.

RESULTS

Screening of 12 tDMRs revealed 2 genomic regions (SLC16A5 and ZNF206) with frequent aberrant methylation patterns in NB. The methylation levels of SLC16A5 and ZNF206 were low compared to the control adrenal medullas. The SLC16A5 methylation level (cut-off point, 13.25%) was associated with age at diagnosis, disease stage, and Shimada classification but not with MYCN amplification. The ZNF206 methylation level (cut-off point, 68.80%) was associated with all of the prognostic factors analyzed. Although the methylation levels at these regions did not reach statistical significance in their association with prognosis in mono-variant analysis, patients with both hypomethylation of SLC16A5 and hypermethylation of ZNF206 had a significantly prolonged event-free survival, when these two variables were analyzed together.

CONCLUSIONS

We demonstrated that two tDMRs frequently displayed altered methylation patterns in the NB genome, suggesting their distinct involvement in NB development/differentiation. The combined analysis of these two regions could serve as a diagnostic biomarker for poor clinical outcome.

Demarcation of stable subpopulations within the pluripotent hESC compartment

Heterogeneity is a feature of stem cell populations, resulting from innate cellular hierarchies that govern differentiation capability. How heterogeneity impacts human pluripotent stem cell populations is directly relevant to their efficacious use in regenerative medicine applications. The control of pluripotency is asserted by a core transcription factor network, of which Oct4 is a necessary member. In mouse embryonic stem cells (ESCs), the zinc finger transcription factor Rex1 (Zfp42) closely tracks the undifferentiated state and is capable of segregating Oct4 positive mESCs into metastable populations expressing or lacking Rex1 that are inter-convertible. However, little is currently understood about the extent or function of heterogeneous populations in the human pluripotent compartment. Human ESCs express REX1 transcripts but the distribution and properties of REX1 expressing cells have yet to be described. To address these questions, we used gene targeting in human ESCs to insert the fluorescent protein Venus and an antibiotic selection marker under the control of the endogenous REX1 transcription regulatory elements, generating a sensitive, selectable reporter of pluripotency. REX1 is co-expressed in OCT4 and TRA-1-60 positive hESCs and rapidly lost upon differentiation. Importantly, REX1 expression reveals significant heterogeneity within seemingly homogenous populations of OCT4 and TRA-1-60 hESCs. REX1 expression is extinguished before OCT4 during differentiation, but, in contrast to the mouse, loss of REX1 expression demarcates a stable, OCT4 positive lineage-primed state in pluripotent hESCs that does not revert back to REX1 positivity under normal conditions. We show that loss of REX1 expression correlates with altered patterns of DNA methylation at the REX1 locus, implying that epigenetic mechanisms may interfere with the metastable phenotype commonly found in murine pluripotency.

Isolation and characterization of human dental pulp derived stem cells by using media containing low human serum percentage as clinical grade substitutes for bovine serum

Adult stem cells have been proposed as an alternative to embryonic stem cells to study multilineage differentiation in vitro and to use in therapy. Current culture media for isolation and expansion of adult stem cells require the use of large amounts of animal sera, but animal-derived culture reagents give rise to some questions due to the real possibility of infections and severe immune reactions. For these reasons a clinical grade substitute to animal sera is needed. We tested the isolation, proliferation, morphology, stemness related marker expression, and osteoblastic differentiation potential of Dental Pulp Stem Cells (DPSC) in a chemically defined medium containing a low percentage of human serum, 1.25%, in comparison to a medium containing 10% Fetal Bovine Serum (FBS). DPSCs cultured in presence of our isolation/proliferation medium added with low HS percentage were obtained without immune-selection methods and showed high uniformity in the expression of stem cell markers, proliferated at higher rate, and demonstrated comparable osteoblastic potential with respect to DPSCs cultured in 10% FBS. In this study we demonstrated that a chemically defined medium added with low HS percentage, derived from autologous and heterologous sources, could be a valid substitute to FBS-containing media and should be helpful for adult stem cells clinical application.

Generation of naive-like porcine-induced pluripotent stem cells capable of contributing to embryonic and fetal development

In pluripotent stem cells (PSCs), there are 2 types: naive and primed. Only the naive type has the capacity for producing chimeric offspring. Mouse PSCs are naive, but human PSCs are in the primed state. Previously reported porcine PSCs appear in the primed state. In this study, putative naive porcine-induced pluripotent stem cells (iPSCs) were generated. Porcine embryonic fibroblasts were transduced with retroviral vectors expressing Yamanaka's 4 genes. Emergent colonies were propagated in the presence of porcine leukemia inhibitory factor (pLIF) and forskolin. The cells expressed pluripotency markers and formed embryoid bodies, which gave rise to cell types from all 3 embryonic germ layers. The naive state of the cells was demonstrated by pLIF dependency, 2 active X chromosomes (when female), absent MHC class I expression, and characteristic gene expression profiles. The porcine iPSCs contributed to the in vitro embryonic development (11/24, 45.8%) as assessed by fluorescent markers. They also contributed to the in utero fetal development (11/71, 15.5% at day 23; 1/13, 7.7% at day 65). This is the first demonstration of macroscopic fluorescent chimeras derived from naive-like porcine PSCs, although adult chimeras remain to be produced.

Human adipose tissue-derived SSEA-4 subpopulation multi-differentiation potential towards the endothelial and osteogenic lineages

Human adipose tissue has been recently recognized as a potential source of stem cells for regenerative medicine applications, including bone tissue engineering (TE). Despite the gathered knowledge regarding the differentiation potential of human adipose tissue-derived stem cells (hASCs), in what concerns the endothelial lineage many uncertainties are still present. The existence of a cell subpopulation within the human adipose tissue that expresses a SSEA-4 marker, usually associated to pluripotency, raises expectations on the differentiation capacity of these cells (SSEA-4(+)hASCs). In the present study, the endothelial and osteogenic differentiation potential of the SSEA-4(+)hASCs was analyzed, aiming at proposing a single-cell source/subpopulation for the development of vascularized bone TE constructs. SSEA-4(+)hASCs were isolated using immunomagnetic sorting and cultured either in α-MEM, in EGM-2 MV (endothelial growth medium), or in osteogenic medium. SSEA-4(+)hASCs cultured in EGM-2 MV formed endothelial cell-like colonies characterized by a cobblestone morphology and expression of CD31, CD34, CD105, and von Willebrand factor as determined by quantitative reverse transcriptase (RT)-polymerase chain reaction, immunofluorescence, and flow cytometry. The endothelial phenotype was also confirmed by their ability to incorporate acetylated low-density lipoprotein and to form capillary-like structures when seeded on Matrigel. SSEA-4(+)hASCs cultured in α-MEM displayed fibroblastic-like morphology and exhibited a mesenchymal surface marker profile (>90% CD90(+)/CD73(+)/CD105(+)). After culture in osteogenic conditions, an overexpression of osteogenic-related markers (osteopontin and osteocalcin) was observed both at molecular and protein levels. Matrix mineralization detected by Alizarin Red staining confirmed SSEA-4(+)hASCs osteogenic differentiation. Herein, we demonstrate that from a single-cell source, human adipose tissue, and by selecting the appropriate subpopulation it is possible to obtain microvascular-like endothelial cells and osteoblasts, the most relevant cell types for the creation of vascularized bone tissue-engineered constructs.

Ontological differences in first compared to third trimester human fetal placental chorionic stem cells

Human mesenchymal stromal/stem cells (MSC) isolated from fetal tissues hold promise for use in tissue engineering applications and cell-based therapies, but their collection is restricted ethically and technically. In contrast, the placenta is a potential source of readily-obtainable stem cells throughout pregnancy. In fetal tissues, early gestational stem cells are known to have advantageous characteristics over neonatal and adult stem cells. Accordingly, we investigated whether early fetal placental chorionic stem cells (e-CSC) were physiologically superior to their late gestation fetal chorionic counterparts (l-CSC). We showed that e-CSC shared a common phenotype with l-CSC, differentiating down the osteogenic, adipogenic and neurogenic pathways, and containing a subset of cells endogenously expressing NANOG, SOX2, c-MYC, and KLF4, as well as an array of genes expressed in pluripotent stem cells and primordial germ cells, including CD24, NANOG, SSEA4, SSEA3, TRA-1-60, TRA-1-81, STELLA, FRAGILIS, NANOS3, DAZL and SSEA1. However, we showed that e-CSC have characteristics of an earlier state of stemness compared to l-CSC, such as smaller size, faster kinetics, uniquely expressing OCT4A variant 1 and showing higher levels of expression of NANOG, SOX2, c-MYC and KLF4 than l-CSC. Furthermore e-CSC, but not l-CSC, formed embryoid bodies containing cells from the three germ layer lineages. Finally, we showed that e-CSC demonstrate higher tissue repair in vivo; when transplanted in the osteogenesis imperfecta mice, e-CSC, but not l-CSC increased bone quality and plasticity; and when applied to a skin wound, e-CSC, but not l-CSC, accelerated healing compared to controls. Our results provide insight into the ontogeny of the stemness phenotype during fetal development and suggest that the more primitive characteristics of early compared to late gestation fetal chorionic stem cells may be translationally advantageous.

Clonal neural stem cells from human embryonic stem cell colonies

Clonal cell culture is crucial for experimental protocols that require growth or selection of pure populations of cells. High-density derivation of neural progenitors from human embryonic stem cells (hESCs) can lead to incomplete differentiation, and transplantation of resulting heterogeneous cell mixtures can cause proliferation of tumorigenic clusters in vivo. We have identified the neural precursor that resides among normal hESC colonies as a TRA-1-60(-)/SSEA4(-)/SOX1(+) cell and developed a method that allows for the clonal expansion of these FACS-selected progenitors to neural stem cells (NSCs) in serum-free conditions. Single TRA-1-60(-)/SSEA4(-)/SOX1(+) cells grown in serum-free media give rise to multipotent NSCs with an efficiency of 0.7%. The fate of the TRA-1-60(-)/SSEA4(-)/SOX1(+) neural precursor becomes specified in maintenance conditions by inhibition of BMP signaling. This clonal culture method can be scaled up to produce NSCs for differentiation and use in cell therapies.

Buffalo (Bubalus bubalis) ES cell-like cells are capable of in vitro skeletal myogenic differentiation

When buffalo embryonic stem (ES) cell-like cells that expressed surface markers SSEA-4, TRA-1-60, TRA-1-81, CD9 and CD90 and intracellular markers OCT4, SOX2 and FOXD3, as shown by immunofluorescence, and that expressed REX-1 and NUCLEOSTEMIN as confirmed by RT-PCR, were subjected to suspension culture in hanging drops in absence of LIF and buffalo foetal fibroblast feeder layer support, they differentiated to form three-dimensional embryoid bodies (EBs). Of 231 EBs examined on Day 3 of suspension culture, 141 (61.3 ± 3.09%) were of compact type, whereas 90 (38.4 ± 3.12%) were of cystic type. The cells obtained from EBs were found to express NF-68 and NESTIN (ectodermal lineage), BMP-4 and α-skeletal actin (mesodermal lineage), and α-fetoprotein, GATA-4 and HNF-4 (endodermal lineage). When these EBs were cultured on gelatin-coated dishes, they spontaneously differentiated to several cell types such as epithelial- and neuron-like cells. When EBs were cultured in the presence of 1 or 2% DMSO or 10(-8) M or 10(-7) M retinoic acid for 25 days, ES cells could be directed to form muscle cell-like cells, the identity of which was confirmed by expression of α-actinin by immunofluorescence and of MYF-5, MYOD and MYOGENIN genes by RT-PCR. MYOD was first detected on Day 10 in both treatment groups and on Day 15 in controls, whereas MYOGENIN was first detected on Day 10, Day 15 and Day 25 in the presence of retinoic acid, in the presence of DMSO and in controls, respectively. The present study demonstrates the ability of buffalo ES cell-like cells to undergo directed differentiation to cells of skeletal myogenic lineage.

In vivo differentiation potential of buffalo (Bubalus bubalis) embryonic stem cell

Embryonic stem cells (ESCs) derived from inner cell mass (ICM) of mammalian blastocyst are having indefinite proliferation and differentiation capability for any type of cell lineages. In the present study, ICMs of in vitro-derived buffalo blastocysts were cultured into two different culture systems using buffalo fetal fibroblast as somatic cell support and Matrigel as synthetic support to obtain pluripotent buffalo embryonic stem cell (buESC) colonies. Pluripotency of the ESCs were characterised through pluripotency markers whereas, their differentiation capability was assessed by teratoma assay using immuno-compromised mice. Cumulus ooccyte complexes from slaughter house-derived ovaries were subjected to in vitro maturation, in vitro fertilization and in vitro culture to generate blastocysts. Total 262 blastocysts were derived through IVEP with 11.83 % (31/262) hatching rate. To generate buESCs, 15 ICMs from hatched blastocysts were cultured on mitomycin-C-treated homologous fetal fibroblast feeder layer, whereas the leftover 16 ICMs were cultured on extra-cellular matrix (Matrigel). No significant differences were observed for primary ESCs colony formation between two culture systems. Primary colonies as well as passaged ESCs were characterised by alkaline phosphatase staining, karyotyping and expression of transcription-based stem cell markers, OCT-4 and cell surface antigens SSEA-4 and TRA-1-60. Batch of ESCs found positive for pluripotency markers and showing normal karyotype after fifteenth passage were inoculated into eight immuno-compromised mice through subcutaneous and intramuscular route. Subcutaneous route of inoculation was found to be better than intramuscular route. Developed teratomas were excised surgically and subjected to histological analysis. Histological findings revealed presence of all the three germinal layer derivatives in teratoma sections. Presence of germinal layer derivatives were further confirmed by reverse transcriptase-polymerase chain reaction for the presence of differentiation markers like nerve cell adhesion molecule, fetal liver kinase-1 and alpha-feto protein for ectoderm, mesoderm and endoderm, respectively.

Embryonic stem cell markers

Embryonic stem cell (ESC) markers are molecules specifically expressed in ES cells. Understanding of the functions of these markers is critical for characterization and elucidation for the mechanism of ESC pluripotent maintenance and self-renewal, therefore helping to accelerate the clinical application of ES cells. Unfortunately, different cell types can share single or sometimes multiple markers; thus the main obstacle in the clinical application of ESC is to purify ES cells from other types of cells, especially tumor cells. Currently, the marker-based flow cytometry (FCM) technique and magnetic cell sorting (MACS) are the most effective cell isolating methods, and a detailed maker list will help to initially identify, as well as isolate ESCs using these methods. In the current review, we discuss a wide range of cell surface and generic molecular markers that are indicative of the undifferentiated ESCs. Other types of molecules, such as lectins and peptides, which bind to ESC via affinity and specificity, are also summarized. In addition, we review several markers that overlap with tumor stem cells (TSCs), which suggest that uncertainty still exists regarding the benefits of using these markers alone or in various combinations when identifying and isolating cells.

Identification and characterisation of the early differentiating cells in neural differentiation of human embryonic stem cells

One of the challenges in studying early differentiation of human embryonic stem cells (hESCs) is being able to discriminate the initial differentiated cells from the original pluripotent stem cells and their committed progenies. It remains unclear how a pluripotent stem cell becomes a lineage-specific cell type during early development, and how, or if, pluripotent genes, such as Oct4 and Sox2, play a role in this transition. Here, by studying the dynamic changes in the expression of embryonic surface antigens, we identified the sequential loss of Tra-1-81 and SSEA4 during hESC neural differentiation and isolated a transient Tra-1-81(−)/SSEA4(+) (TR−/S4+) cell population in the early stage of neural differentiation. These cells are distinct from both undifferentiated hESCs and their committed neural progenitor cells (NPCs) in their gene expression profiles and response to extracellular signalling; they co-express both the pluripotent gene Oct4 and the neural marker Pax6. Furthermore, these TR−/S4+ cells are able to produce cells of both neural and non-neural lineages, depending on their environmental cues. Our results demonstrate that expression of the pluripotent factor Oct4 is progressively downregulated and is accompanied by the gradual upregulation of neural genes, whereas the pluripotent factor Sox2 is consistently expressed at high levels, indicating that these pluripotent factors may play different roles in the regulation of neural differentiation. The identification of TR-S4+ cells provides a cell model for further elucidation of the molecular mechanisms underlying hESC neural differentiation.

The state of the art for pluripotent stem cells derivation in domestic ungulates

Since the successful isolation, characterization and long-term culture of embryonic stem cells (ESCs) from mice in the early 1980s and from humans a decade later, considerable effort has been made to establish ESCs lines from livestock. The derivation of validated ESCs lines is a necessary step if the generation of economically relevant transgenic animals is to be achieved. However, this is still elusive, as the isolation of true ESCs lines for livestock has not been accomplished to date. It has been demonstrated that by forced expression of a defined set of transcription factors, it is possible to reprogram somatic cells to cells that closely resemble an ES-like state. These cells were termed induced pluripotent stem cells (iPSCs). We introduce the basic concepts relating to stem cell biology and give an overview of the various attempts to isolate and generate pluripotent stem cells (PSCs) from species relevant to livestock production. Further, we point out the issues to be addressed and hurdles to be overcome to realize the promise of stem cells in agriculture.

The differential formation of the LINC-mediated perinuclear actin cap in pluripotent and somatic cells

The actin filament cytoskeleton mediates cell motility and adhesion in somatic cells. However, whether the function and organization of the actin network are fundamentally different in pluripotent stem cells is unknown. Here we show that while conventional actin stress fibers at the basal surface of cells are present before and after onset of differentiation of mouse (mESCs) and human embryonic stem cells (hESCs), actin stress fibers of the actin cap, which wrap around the nucleus, are completely absent from undifferentiated mESCs and hESCs and their formation strongly correlates with differentiation. Similarly, the perinuclear actin cap is absent from human induced pluripotent stem cells (hiPSCs), while it is organized in the parental lung fibroblasts from which these hiPSCs are derived and in a wide range of human somatic cells, including lung, embryonic, and foreskin fibroblasts and endothelial cells. During differentiation, the formation of the actin cap follows the expression and proper localization of nuclear lamin A/C and associated linkers of nucleus and cytoskeleton (LINC) complexes at the nuclear envelope, which physically couple the actin cap to the apical surface of the nucleus. The differentiation of hESCs is accompanied by the progressive formation of a perinuclear actin cap while induced pluripotency is accompanied by the specific elimination of the actin cap, and that, through lamin A/C and LINC complexes, this actin cap is involved in progressively shaping the nucleus of hESCs undergoing differentiation. While, the localization of lamin A/C at the nuclear envelope is required for perinuclear actin cap formation, it is not sufficient to control nuclear shape.

Very small embryonic-like stem cells purified from umbilical cord blood lack stem cell characteristics

Very small embryonic-like (VSEL) cells have been described as putatively pluripotent stem cells present in murine bone marrow and human umbilical cord blood (hUCB) and as such are of high potential interest for regenerative medicine. However, there remain some questions concerning the precise identity and properties of VSEL cells, particularly those derived from hUCB. For this reason, we have carried out an extensive characterisation of purified populations of VSEL cells from a large number of UCB samples. Consistent with a previous report, we find that VSEL cells are CXCR4⁺, have a high density, are indeed significantly smaller than HSC and have an extremely high nuclear/cytoplasmic ratio. Their nucleoplasm is unstructured and stains strongly with Hoechst 33342. A comprehensive FACS screen for surface markers characteristic of embryonic, mesenchymal, neuronal or hematopoietic stem cells revealed negligible expression on VSEL cells. These cells failed to expand in vitro under a wide range of culture conditions known to support embryonic or adult stem cell types and a microarray analysis revealed the transcriptional profile of VSEL cells to be clearly distinct both from well-defined populations of pluripotent and adult stem cells and from the mature hematopoietic lineages. Finally, we detected an aneuploid karyotype in the majority of purified VSEL cells by fluorescence in situ hybridisation. These data support neither an embryonic nor an adult stem cell like phenotype, suggesting rather that hUCB VSEL cells are an aberrant and inactive population that is not comparable to murine VSEL cells.

Derivation of novel genetically diverse human embryonic stem cell lines

Human embryonic stem cells (hESCs) have the potential to revolutionize many biomedical fields ranging from basic research to disease modeling, regenerative medicine, drug discovery, and toxicity testing. A multitude of hESC lines have been derived worldwide since the first 5 lines by Thomson et al. 13 years ago, but many of these are poorly characterized, unavailable, or do not represent desired traits, thus making them unsuitable for application purposes. In order to provide the scientific community with better options, we have derived 12 new hESC lines at New York University from discarded genetically normal and abnormal embryos using the latest techniques. We examined the genetic status of the NYUES lines in detail as well as their molecular and cellular features and DNA fingerprinting profile. Furthermore, we differentiated our hESCs into the tissues most affected by a specific condition or into clinically desired cell types. To our knowledge, a number of characteristics of our hESCs have not been previously reported, for example, mutation for alpha thalassemia X-linked mental retardation syndrome, linkage to conditions with a genetic component such as asthma or poor sperm morphology, and novel combinations of ethnic backgrounds. Importantly, all of our undifferentiated euploid female lines tested to date did not show X chromosome inactivation, believed to result in superior potency. We continue to derive new hESC lines and add them to the NIH registry and other registries. This should facilitate the use of our hESCs and lead to advancements for patient-benefitting applications.

Amniotic mesenchymal stem cells: a new source for hepatocyte-like cells and induction of CFTR expression by coculture with cystic fibrosis airway epithelial cells

Cystic fibrosis (CF) is a monogenic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, with lung and liver manifestations. Because of pitfalls of gene therapy, novel approaches for reconstitution of the airway epithelium and CFTR expression should be explored. In the present study, human amniotic mesenchymal stem cells (hAMSCs) were isolated from term placentas and characterized for expression of phenotypic and pluripotency markers, and for differentiation potential towards mesoderm (osteogenic and adipogenic) lineages. Moreover, hAMSCs were induced to differentiate into hepatocyte-like cells, as demonstrated by mixed function oxidase activity and expression of albumin, alpha1-antitrypsin, and CK19. We also investigated the CFTR expression in hAMSCs upon isolation and in coculture with CF airway epithelial cells. Freshly isolated hAMSCs displayed low levels of CFTR mRNA, which even decreased with culture passages. Following staining with the vital dye CM-DiI, hAMSCs were mixed with CFBE41o- respiratory epithelial cells and seeded onto permeable filters. Flow cytometry demonstrated that 33–50% of hAMSCs acquired a detectable CFTR expression on the apical membrane, a result confirmed by confocal microscopy. Our data show that amniotic MSCs have the potential to differentiate into epithelial cells of organs relevant in CF pathogenesis and may contribute to partial correction of the CF phenotype.

Isolation and basic characterization of human term amnion and chorion mesenchymal stromal cells

BACKGROUND AIMS

Emerging evidence suggests human placental membrane is a valuable source of mesenchymal stromal cells (MSC). Amnion and chorion are tissues of early embryologic origin that may entail progenitor potential. These tissues are abundantly available and ethically unobjectionable and, because they are discarded post-partum, they can be widely used for extensive research and eventually for therapeutic studies.

METHODS

We looked at the cells isolated from the six amnions and chorions of term placentas of gestational weeks 39 ± 1. Isolated cells were characterized by morphologic and immunophenotypic analysis.

RESULTS

With flow cytometry immunophenotype analysis, amnion- and chorion-derived cells were positive for MSC markers, and negative for hematopoietic markers. Immunocytochemical staining was positive for the embryonic cell markers Oct-3/4 and Rex-1. Oct-3/4 is a POU transcription factor that is expressed in embryonic stem (ES) cells and germ cells, and its expression is required to sustain cell self-renewal and pluripotency. Oct-3/4 is the most recognized marker for totipotent ES cells. Rex-1 is a zinc finger family transcription factor that is highly expressed in embryonic stem cells. It is one of several gene markers used to identify undifferentiated stem cells, and its expression is downregulated upon stem cell differentiation. Amnion- and chorion-derived cells were capable, under differentiation conditions, to differentiate into to mesoderm lineages.

CONCLUSIONS

Phenotypic studies indicate MSC-like profiles in both amnion- and chorion-derived cells. Cells in vitro had fibroblastoid morphology. The in vitro growth behavior of such placenta-derived progenitor cells was similar to that of bone marrow MSC. Our results indicate that MSC can be easily isolated from the human term placenta. The human amniotic and chorion MSC maintained a marker profile similar to the mesenchymal progenitors and could be used for studies as an alternative source of MSC for further application in cellular therapy.

Genome-wide identification of microRNA targets in human ES cells reveals a role for miR-302 in modulating BMP response

MicroRNAs are important regulators in many cellular processes, including stem cell self-renewal. Recent studies demonstrated their function as pluripotency factors with the capacity for somatic cell reprogramming. However, their role in human embryonic stem (ES) cells (hESCs) remains poorly understood, partially due to the lack of genome-wide strategies to identify their targets. Here, we performed comprehensive microRNA profiling in hESCs and in purified neural and mesenchymal derivatives. Using a combination of AGO cross-linking and microRNA perturbation experiments, together with computational prediction, we identified the targets of the miR-302/367 cluster, the most abundant microRNAs in hESCs. Functional studies identified novel roles of miR-302/367 in maintaining pluripotency and regulating hESC differentiation. We show that in addition to its role in TGF-β signaling, miR-302/367 promotes bone morphogenetic protein (BMP) signaling by targeting BMP inhibitors TOB2, DAZAP2, and SLAIN1. This study broadens our understanding of microRNA function in hESCs and is a valuable resource for future studies in this area.

Modeling neurological disorders by human induced pluripotent stem cells

Studies of human brain development are critical as research on neurological disorders have been progressively advanced. However, understanding the process of neurogenesis through analysis of the early embryo is complicated and limited by a number of factors, including the complexity of the embryos, availability, and ethical constrains. The emerging of human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) has shed light of a new approach to study both early development and disease pathology. The cells behave as precursors of all embryonic lineages; thus, they allow tracing the history from the root to individual branches of the cell lineage tree. Systems for neural differentiation of hESCs and iPSCs have provided an experimental model that can be used to augment in vitro studies of in vivo brain development. Interestingly, iPSCs derived from patients, containing donor genetic background, have offered a breakthrough approach to study human genetics of neurodegenerative diseases. This paper summarizes the recent reports of the development of iPSCs from patients who suffer from neurological diseases and evaluates the feasibility of iPSCs as a disease model. The benefits and obstacles of iPSC technology are highlighted in order to raising the cautions of misinterpretation prior to further clinical translations.

TOPAZ1, a novel germ cell-specific expressed gene conserved during evolution across vertebrates

BACKGROUND

We had previously reported that the Suppression Subtractive Hybridization (SSH) approach was relevant for the isolation of new mammalian genes involved in oogenesis and early follicle development. Some of these transcripts might be potential new oocyte and granulosa cell markers. We have now characterized one of them, named TOPAZ1 for the Testis and Ovary-specific PAZ domain gene.

PRINCIPAL FINDINGS

Sheep and mouse TOPAZ1 mRNA have 4,803 bp and 4,962 bp open reading frames (20 exons), respectively, and encode putative TOPAZ1 proteins containing 1,600 and 1653 amino acids. They possess PAZ and CCCH domains. In sheep, TOPAZ1 mRNA is preferentially expressed in females during fetal life with a peak during prophase I of meiosis, and in males during adulthood. In the mouse, Topaz1 is a germ cell-specific gene. TOPAZ1 protein is highly conserved in vertebrates and specifically expressed in mouse and sheep gonads. It is localized in the cytoplasm of germ cells from the sheep fetal ovary and mouse adult testis.

CONCLUSIONS

We have identified a novel PAZ-domain protein that is abundantly expressed in the gonads during germ cell meiosis. The expression pattern of TOPAZ1, and its high degree of conservation, suggests that it may play an important role in germ cell development. Further characterization of TOPAZ1 may elucidate the mechanisms involved in gametogenesis, and particularly in the RNA silencing process in the germ line.

Knockdown of the potential cancer stem-like cell marker Rex-1 improves chemotherapeutic effects in gliomas

In the present study, we show that Rex-1 mRNA and protein are found at high levels in both 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU)-resistant glioma cell subpopulations and malignant glioblastoma multiforme (GBM) tissue. We used a combination therapy of small interfering RNA (siRNA) against Rex-1 (siRex-1) and BCNU to target GBM cells. Rex-1 siRNA/BCNU treatment resulted in growth inhibition and a diminished S phase. The treatment efficiently induced P38/JNK and Akt/PI3K/GSK3β signaling and led to apoptosis both in vitro and in vivo. We also show that Rex-1/ABCG2 (ATP binding cassette transporter G2)-coexpressing subpopulations were chemoresistant; however, BCNU was not a substrate for ABCG2. siRex-1 treatment led to cell death in GBM subpopulations by promoting apoptosis. Moreover, siRex-1/BCNU combination therapy targeted both the major population and cancer stem cell-like subpopulations. Our findings are important for the development of clinical applications to treat GBM.

Human amniotic fluid-derived stem cells can differentiate into hepatocyte-like cells in vitro and in vivo

Although human amniotic fluid is an attractive source of multipotent stem cells, the potential of amniotic fluid stem cells (AFSCs) to differentiate into hepatic cells has not been extensively evaluated. In this study, we examined whether human AFSCs can differentiate into a hepatic cell lineage in vitro and in vivo. After being treated with cytokines (fibroblast growth factor 4, basic fibroblast growth factor, hepatocyte growth factor, and oncostatin), AFSCs developed a morphology similar to that of hepatocytes. RT-PCR and immunofluorescence analysis showed that the treated AFSCs expressed the hepatocyte-specific markers albumin, cytokeratin 18, and alpha-fetoprotein. The differentiated cells also developed hepatocyte-specific functions, i.e., they secreted albumin, absorbed indocyanine green, and stored glycogen. When transplanted into CCl(4)-injured immunodeficient mice, undifferentiated AFSCs were integrated into the liver tissue, and they expressed markers characteristic of mature human hepatocytes. Although integration of AFSCs into the liver was limited (0.1-0.3% of hepatocytes), histological analysis showed that the recipient mice recovered more rapidly from CCl(4) injury than CCl(4)-injured mice that did not receive AFSCs. AFSCs can differentiate into hepatocyte-like cells in vitro and in vivo and can represent an easily accessible source of progenitor cells for hepatocyte regeneration and liver cell transplantation.

Effective transplantation of photoreceptor precursor cells selected via cell surface antigen expression

Retinal degenerative diseases are a major cause of untreatable blindness. Stem cell therapy to replace lost photoreceptors represents a feasible future treatment. We previously demonstrated that postmitotic photoreceptor precursors expressing an NrlGFP transgene integrate into the diseased retina and restore some light sensitivity. As genetic modification of precursor cells derived from stem cell cultures is not desirable for therapy, we have tested cell selection strategies using fluorochrome-conjugated antibodies recognizing cell surface antigens to sort photoreceptor precursors. Microarray analysis of postnatal NrlGFP-expressing precursors identified four candidate genes encoding cell surface antigens (Nt5e, Prom1, Podxl, and Cd24a). To test the feasibility of using donor cells isolated using cell surface markers for retinal therapy, cells selected from developing retinae by fluorescence-activated cell sorting based on Cd24a expression (using CD24 antibody) and/or Nt5e expression (using CD73 antibody) were transplanted into the wild-type or Crb1(rd8/rd8) or Prph2(rd2/rd2) mouse eye. The CD73/CD24-sorted cells migrated into the outer nuclear layer, acquired the morphology of mature photoreceptors and expressed outer segment markers. They showed an 18-fold higher integration efficiency than that of unsorted cells and 2.3-fold higher than cells sorted based on a single genetic marker, NrlGFP, expression. These proof-of-principle studies show that transplantation competent photoreceptor precursor cells can be efficiently isolated from a heterogeneous mix of cells using cell surface antigens without loss of viability for the purpose of retinal stem cell therapy. Refinement of the selection of donorphotoreceptor precursor cells can increase the number of integrated photoreceptor cells,which is a prerequisite for the restoration of sight.

SSEA4 is a potential negative marker for the enrichment of human corneal epithelial stem/progenitor cells

PURPOSE

To examine the expression of stage-specific embryonic antigen-4 (SSEA4) in the epithelium of the human ocular surface and characterize SSEA4(+) and SSEA4(-) limbal epithelial cells.

METHODS

SSEA4 expression in the human cornea and limbus was examined by RT-PCR and immunohistochemistry. SSEA4(+) and SSEA4(-) cells were then separated by using magnetic beads. The phenotypes of these two cell populations were evaluated on the basis of cell size, clonogenic assay, and expression of putative limbal stem cell (LSC) and corneal epithelial differentiation markers.

RESULTS

SSEA4 was expressed in all layers of the corneal and anterior limbal epithelia. Discrete clusters of SSEA4(+) cells were present in the central and posterior limbal epithelia. SSEA4(+) cells accounted for an average of 40% of the total limbal epithelial cells. The SSEA4(-) population contained five times more small cells (≤11 μm in diameter) than did the SSEA4(+) population. The expression levels of the putative LSC markers ABCG2, ΔNp63α, and cytokeratin (K)14 were significantly higher in the SSEA4(-) population than in the SSEA4(+) population. The SSEA4(-) cells also expressed a significantly higher level of N-cadherin, but a lower level of the differentiation marker K12. The colony-forming efficiency in the SSEA4(-) population was 25.2% (P = 0.04) and 1.6-fold (P < 0.05) higher than in the unsorted population and the SSEA4(+) population, respectively.

CONCLUSIONS

SSEA4 is highly expressed in differentiated corneal epithelial cells, and SSEA4(-) limbal epithelial cells contain a higher proportion of limbal stem/progenitor cells. SSEA4 could be used as a negative marker to enrich the isolation of LSCs.

Pitx1 haploinsufficiency causes clubfoot in humans and a clubfoot-like phenotype in mice

Clubfoot affects 1 in 1000 live births, although little is known about its genetic or developmental basis. We recently identified a missense mutation in the PITX1 bicoid homeodomain transcription factor in a family with a spectrum of lower extremity abnormalities, including clubfoot. Because the E130K mutation reduced PITX1 activity, we hypothesized that PITX1 haploinsufficiency could also cause clubfoot. Using copy number analysis, we identified a 241 kb chromosome 5q31 microdeletion involving PITX1 in a patient with isolated familial clubfoot. The PITX1 deletion segregated with autosomal dominant clubfoot over three generations. To study the role of PITX1 haploinsufficiency in clubfoot pathogenesis, we began to breed Pitx1 knockout mice. Although Pitx1(+/-) mice were previously reported to be normal, clubfoot was observed in 20 of 225 Pitx1(+/-) mice, resulting in an 8.9% penetrance. Clubfoot was unilateral in 16 of the 20 affected Pitx1(+/-) mice, with the right and left limbs equally affected, in contrast to right-sided predominant hindlimb abnormalities previously noted with complete loss of Pitx1. Peroneal artery hypoplasia occurred in the clubfoot limb and corresponded spatially with small lateral muscle compartments. Tibial and fibular bone volumes were also reduced. Skeletal muscle gene expression was significantly reduced in Pitx1(-/-) E12.5 hindlimb buds compared with the wild-type, suggesting that muscle hypoplasia was due to abnormal early muscle development and not disuse atrophy. Our morphological data suggest that PITX1 haploinsufficiency may cause a developmental field defect preferentially affecting the lateral lower leg, a theory that accounts for similar findings in human clubfoot.

The role of engineered tendon matrix in the stemness of tendon stem cells in vitro and the promotion of tendon-like tissue formation in vivo

When injured, tendons tend to heal but with poor structure and compromised function. Tissue engineering is a promising approach to enhancing the quality of healing tendons. Our group and others have identified tendon stem cells (TSCs), a type of tendon-specific stem cells which may be optimal for cellular interventions seeking to restore normal structure and function to injured tendons. However, in vitro expanding of TSCs on regular plastic cell culture dishes only yields a limited number of TSCs before they lose the stemness, i.e., the self-renewal capability and multipotency. In this study, we developed a substrate material for TSCs, engineered tendon matrix (ETM) from decellularized tendon tissues. We showed that ETM in vitro was able to stimulate TSC proliferation and better preserve the stemness of TSCs than plastic culture surfaces. In vivo, implantation of ETM-TSC composite promoted tendon-like tissue formation whereas implantation of TSCs alone led to little such tissue formation. Together, the findings of this study indicate that ETM may be used to effectively expand TSCs in vitro and with TSCs, to enhance repair of injured tendons in vivo.

Amnion-derived stem cells: in quest of clinical applications

In the promising field of regenerative medicine, human perinatal stem cells are of great interest as potential stem cells with clinical applications. Perinatal stem cells could be isolated from normally discarded human placentae, which are an ideal cell source in terms of availability, the fewer number of ethical concerns, less DNA damage, and so on. Numerous studies have demonstrated that some of the placenta-derived cells possess stem cell characteristics like pluripotent differentiation ability, particularly in amniotic epithelial (AE) cells. Term human amniotic epithelium contains a relatively large number of stem cell marker-positive cells as an adult stem cell source. In this review, we introduce a model theory of why so many AE cells possess stem cell characteristics. We also describe previous work concerning the therapeutic applications and discuss the pluripotency of the AE cells and potential pitfalls for amnion-derived stem cell research.

Production of cloned and transgenic embryos using buffalo (Bubalus bubalis) embryonic stem cell-like cells isolated from in vitro fertilized and cloned blastocysts

Here, we report the isolation and characterization of embryonic stem (ES) cell-like cells from cloned blastocysts, generated using fibroblasts derived from an adult buffalo (BAF). These nuclear transfer embryonic stem cell-like cells (NT-ES) grew in well-defined and dome-shaped colonies. The expression pattern of pluripotency marker genes was similar in both NT-ES and in vitro fertilization (IVF) embryo-derived embryonic stem cell-like cells (F-ES). Upon spontaneous differentiation via embryoid body formation, cells of different morphology were observed, among which predominant were endodermal-like and epithelial-like cell types. The ES cell-like cells could be passaged only mechanically and did not form colonies when plated as single cell suspension at different concentrations. When F-ES cell-like, NT-ES cell-like, and BAF cells of same genotype were used for hand-made cloning (HMC), no significant difference (p > 0.05) was observed in cleavage and blastocyst rate. Following transfer of HMC embryos to synchronized recipients, pregnancies were established only with F-ES cell-like and BAF cell-derived embryos, and one live calf was born from F-ES cell-like cells. Further, when transfected NT-ES cell-like cells and BAF were used for HMC, no significant difference (p > 0.05) was observed between cleavage and blastocyst rate. In conclusion, here we report for the first time the derivation of ES cell-like cells from an adult buffalo, and its genetic modification. We also report the birth of a live cloned calf from buffalo ES cell-like cells.

Buffalo (Bubalus bubalis) embryonic stem cell-like cells and preimplantation embryos exhibit comparable expression of pluripotency-related antigens

In this study, inner cell mass (ICM) cells were isolated from in vitro produced buffalo blastocysts and were cultured on mitomycin-C treated buffalo foetal fibroblast feeder layer for producing embryonic stem (ES) cells. Among different sources (hatched vs expanded blastocysts) or methods (enzymatic vs mechanical), mechanical isolation of ICM from hatched blastocysts resulted in the highest primary colony formation rate and the maximum passage number up to which ES cells survived. Putative ES cells expressed alkaline phosphatase and exhibited a normal karyotype up to passage 7. Putative ES cells and embryos at 2- to 4-cell, 8- to 16-cell, morula and blastocyst stages strongly expressed stage-specific embryonic antigen (SSEA)-4 but lacked expressions of SSEA-1 and SSEA-3. Putative ES cells also expressed tumour rejection antigen (TRA)-1-60, TRA-1-81 and Oct4. Whereas in all early embryonic stages, TRA-1-60 was observed only in the periplasmic space, and TRA-1-81 expression was observed as small spots at a few places inside the embryos, both these markers were expressed by ICM. Oct4 expression, which was observed at all the embryonic stages and also in the trophectoderm, was the strongest in the ICM. Buffalo putative ES cells possess a unique pluripotency-related surface antigen phenotype, which resembles that of the ICM.

Cardiac regeneration: different cells same goal

Cardiovascular diseases are the leading cause of mortality, morbidity, hospitalization and impaired quality of life. In most, if not all, pathologic cardiac ischemia ensues triggering a succession of events leading to massive death of cardiomyocytes, fibroblast and extracellular matrix accumulation, cardiomyocyte hypertrophy which culminates in heart failure and eventually death. Though current pharmacological treatment is able to delay the succession of events and as a consequence the development of heart failure, the only currently available and effective treatment of end-stage heart failure is heart transplantation. However, donor heart availability and immunorejection upon transplantation seriously limit the applicability. Cardiac regeneration could provide a solution, making real a dream of both scientist and clinician in the previous century and ending an ongoing challenge for this century. In this review, we present a basic overview of the various cell types that have been used in both the clinical and research setting with respect to myocardial differentiation.

Embryonic stem cell factors undifferentiated transcription factor-1 (UFT-1) and reduced expression protein-1 (REX-1) are widely expressed in human skin and may be involved in cutaneous differentiation but not in stem cell fate determination

Undifferentiated transcription factor-1 (UTF-1) and reduced expression protein-1 (REX-1) are used as markers for the undifferentiated state of pluripotent stem cells. Because no highly specific cytochemical marker for epidermal stem cells has yet been identified, we investigated the expression pattern of these markers in human epidermis and skin tumours by immunohistochemistry and in keratinocyte cell cultures. Both presumed stem cell markers were widely expressed in the epidermis and skin appendages. Distinct expression was found in the matrix cells of the hair shaft. Differentiation of human primary keratinocytes (KC) in vitro strongly downregulated UTF-1 and REX-1 expression. In addition, REX-1 was upregulated in squamous cell carcinomas, indicating a possible role of this transcription factor in malignant tumour formation. Our data point to a role for these proteins not only in maintaining KC stem cell populations, but also in proliferation and differentiation of matrix cells of the shaft and also suprabasal KC.

Ethanol, acetaldehyde, and estradiol affect growth and differentiation of rhesus monkey embryonic stem cells

BACKGROUND

The timing of the origins of fetal alcohol syndrome has been difficult to determine, in part because of the challenge associated with in vivo studies of the peri-implantation stage of embryonic development. Because embryonic stem cells (ESCs) are derived from blastocyst stage embryos, they are used as a model for early embryo development.

METHODS

Rhesus monkey ESC lines (ORMES-6 and ORMES-7) were treated with 0, 0.01, 0.1, or 1.0% ethanol, 1.0% ethanol with estradiol, or 0.00025% acetaldehyde with or without estradiol for 4 weeks.

RESULTS

Although control ESCs remained unchanged, abnormal morphology of ESCs in the ethanol and acetaldehyde treatment groups was observed before 2 weeks of treatment. Immunofluorescence staining of key pluripotency markers (TRA-1-81 and alkaline phosphatase) indicated a loss of ESC pluripotency in the 1.0% ethanol group. ORMES-7 was more sensitive to effects of ethanol than ORMES-6.

CONCLUSIONS

Estradiol appeared to increase sensitivity to ethanol in the ORMES-6 and ORMES-7 cell line. The morphological changes and labeling for pluripotency, proliferation, and apoptosis demonstrated that how ethanol affects these early cells that develop in culture, their differentiation state in particular. The effects of ethanol may be mediated in part through metabolic pathways regulating acetaldehyde formation, and while potentially accentuated by estradiol in some individuals, how remains to be determined.

GROα regulates human embryonic stem cell self-renewal or adoption of a neuronal fate

Previously we reported that feeders formed from human placental fibroblasts (hPFs) support derivation and long-term self-renewal of human embryonic stem cells (hESCs) under serum-free conditions. Here, we show, using antibody array and ELISA platforms, that hPFs secrete ∼6-fold higher amounts of the CXC-type chemokine, GROα, than IMR 90, a human lung fibroblast line, which does not support hESC growth. Furthermore, immunocytochemistry and immunoblot approaches revealed that hESCs express CXCR, a GROα receptor. We used this information to develop defined culture medium for feeder-free propagation of hESCs in an undifferentiated state. Cells passaged as small aggregates and maintained in the GROα-containing medium had a normal karyotype, expressed pluripotency markers, and exhibited apical-basal polarity, i.e., had the defining features of pluripotent hESCs. They also differentiated into the three primary (embryonic) germ layers and formed teratomas in immunocompromised mice. hESCs cultured as single cells in the GROα-containing medium also had a normal karyotype, but they downregulated markers of pluripotency, lost apical-basal polarity, and expressed markers that are indicative of the early stages of neuronal differentiation-βIII tubulin, vimentin, radial glial protein, and nestin. These data support our hypothesis that establishing and maintaining cell polarity is essential for the long-term propagation of hESCs in an undifferentiated state and that disruption of cell-cell contacts can trigger adoption of a neuronal fate.

Reprogramming factors involved in hybrids and cybrids of human embryonic stem cells fused with hepatocytes

Embryonic stem cells (ESCs) have the potential to reprogram somatic cells into ESC-like cells through cell fusion. In the present study, the potential of human (h)ESC cytoplasts and karyoplasts to reprogram human hepatocytes was evaluated. Green fluorescent protein (GFP) transfected hESCs (ENVY cells) were fused with SNARF-1 (CellTracker)-labeled human hepatocytes using polyethylene glycol (PEG) and fluorescence-activated cell sorting (FACS) to produce hESC-hepatocyte hybrids. Immunocytochemical analysis of ESC markers showed that the hybrids expressed OCT4, TRA-1-60, TRA-1-81, SSEA-4, and GCTM-2. However, SSEA-1, which is typically low or absent on hESCs, was detected on hESC–hepatocyte hybrids. Moreover, reverse transcriptase polymerase chain reaction (RT-PCR) showed that alpha-fetoprotein, which is highly expressed in hepatocytes, was erased in the hybrids. These results indicated that hESCs have the potential to reprogram hepatocyte phenotype to a relatively undifferentiated state, but such hybrid cells are not identical to hESCs. Although hESC–hepatocyte hybrids were aneuploid, they were able to differentiate into embryoid bodies and some types of somatic cells. Furthermore, cybrids of enucleated hESCs and hepatocytes were produced by cell fusion, but the cybrids were unable to self-renew in the same way as hESCs. Presumably, the reprogramming factors are associated with the karyoplast and not the cytoplast of hESCs.

Ultrastructural and molecular distinctions between the porcine inner cell mass and epiblast reveal unique pluripotent cell states

Characterization of the pluripotent cell populations within the porcine embryo is essential for understanding pluripotency and self-renewal regulation in the inner cell mass (ICM) and epiblast. In this study, we perform detailed ultrastructural and molecular characterization of the developing pluripotent cell population as it develops from the ICM to the late epiblast. The ultrastructural observations revealed that the outer cells of the ICM have a high nuclear:cytoplasmic ratio but are transcriptionally inactive and contain mitochondria with few cristae. In contrast, the epiblast cells have a reduced nuclear:cytoplasmic ratio, are more transcriptionally active, and contain abundant cellular organelles. This study also revealed cavitation and potential unfolding of the epiblast. As the ICM forms the epiblast, SSEA1 is lost and VIMENTIN is lost and re-expressed. The D6 blastocyst expressed high levels of STELLA, TERF1, and GDF3, and the epiblast expressed epithelial markers, MUC1 and E-CADHERIN, and the pluripotency markers, DNMT3B and CRIPTO.

Using human pluripotent stem cells to untangle neurodegenerative disease mechanisms

Human pluripotent stem cells, including embryonic (hES) and induced pluripotent stem cells (hiPS), retain the ability to self-renew indefinitely, while maintaining the capacity to differentiate into all cell types of the nervous system. While human pluripotent cell-based therapies are unlikely to arise soon, these cells can currently be used as an inexhaustible source of committed neurons to perform high-throughput screening and safety testing of new candidate drugs. Here, we describe critically the available methods and molecular factors that are used to direct the differentiation of hES or hiPS into specific neurons. In addition, we discuss how the availability of patient-specific hiPS offers a unique opportunity to model inheritable neurodegenerative diseases and untangle their pathological mechanisms, or to validate drugs that would prevent the onset or the progression of these neurological disorders.

Regional differentiation of retinoic acid-induced human pluripotent embryonic carcinoma stem cell neurons

The NTERA2 cl D1 (NT2) cell line, derived from human teratocarcinoma, exhibits similar properties as embryonic stem (ES) cells or very early neuroepithelial progenitors. NT2 cells can be induced to become postmitotic central nervous system neurons (NT2N) with retinoic acid. Although neurons derived from pluripotent cells, such as NT2N, have been characterized for their neurotransmitter phenotypes, their potential suitability as a donor source for neural transplantation also depends on their ability to respond to localized environmental cues from a specific region of the CNS. Therefore, our study aimed to characterize the regional transcription factors that define the rostocaudal and dorsoventral identity of NT2N derived from a monolayer differentiation paradigm using quantitative PCR (qPCR). Purified NT2N mainly expressed both GABAergic and glutamatergic phenotypes and were electrically active but did not form functional synapses. The presence of immature astrocytes and possible radial glial cells was noted. The NT2N expressed a regional transcription factor code consistent with forebrain, hindbrain and spinal cord neural progenitors but showed minimal expression of midbrain phenotypes. In the dorsoventral plane NT2N expressed both dorsal and ventral neural progenitors. Of major interest was that even under the influence of retinoic acid, a known caudalization factor, the NT2N population maintained a rostral phenotype subpopulation which expressed cortical regional transcription factors. It is proposed that understanding the regional differentiation bias of neurons derived from pluripotent stem cells will facilitate their successful integration into existing neuronal networks within the CNS.

Adult human CD133/1(+) kidney cells isolated from papilla integrate into developing kidney tubules

Approximately 60,000 patients in the United States are waiting for a kidney transplant due to genetic, immunologic and environmentally caused kidney failure. Adult human renal stem cells could offer opportunities for autologous transplant and repair of damaged organs. Current data suggest that there are multiple progenitor types in the kidney with distinct localizations. In the present study, we characterize cells derived from human kidney papilla and show their capacity for tubulogenesis. In situ, nestin(+) and CD133/1(+) cells were found extensively intercalated between tubular epithelia in the loops of Henle of renal papilla, but not of the cortex. Populations of primary cells from the renal cortex and renal papilla were isolated by enzymatic digestion from human kidneys unsuited for transplant and immuno-enriched for CD133/1(+) cells. Isolated CD133/1(+) papillary cells were positive for nestin, as well as several human embryonic stem cell markers (SSEA4, Nanog, SOX2, and OCT4/POU5F1) and could be triggered to adopt tubular epithelial and neuronal-like phenotypes. Isolated papillary cells exhibited morphologic plasticity upon modulation of culture conditions and inhibition of asymmetric cell division. Labeled papillary cells readily associated with cortical tubular epithelia in co-culture and 3-dimensional collagen gel cultures. Heterologous organ culture demonstrated that CD133/1(+) progenitors from the papilla and cortex became integrated into developing kidney tubules. Tubular epithelia did not participate in tubulogenesis. Human renal papilla harbor cells with the hallmarks of adult kidney stem/progenitor cells that can be amplified and phenotypically modulated in culture while retaining the capacity to form new kidney tubules. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

Using cadherin expression to assess spontaneous differentiation of embryonic stem cells

Embryonic stem cells (ESCs) are pluripotent cells derived from preimplantation embryos and can be maintained in an undifferentiated state over prolonged periods in vitro. In addition, ESCs can be induced to differentiate into cells representative of the three primary germ layers. As such, ESCs are a useful system for studying early developmental events in vitro and have the potential to provide a ubiquitous supply of somatic cells for use in regenerative medicine. However, significant differences in the expression pattern of various cell surface markers between murine and human ESCs, e.g. the SSEA series, necessitate the use of separate markers for determining the undifferentiated state of these cells. We have recently shown that an E- to N-cadherin switch occurs during spontaneous differentiation of both murine and human ESCs. Here we describe the use of E-cadherin and N-cadherin proteins and transcript expression for assessing the proportion of undifferentiated and spontaneously differentiated cells within ESC populations. In summary, loss of cell surface E-cadherin and/or gain of N-cadherin protein expression provides a useful nondestructive assay for the determination of the proportion of spontaneously differentiated cells within an ESC population. In addition, presence of N-cadherin transcripts in an ESC population is indicative of spontaneous differentiation of a proportion of the cells.