Establishment of porcine and human expanded potential stem cells

We recently derived mouse expanded potential stem cells (EPSCs) from individual blastomeres by inhibiting the critical molecular pathways that predispose their differentiation. EPSCs had enriched molecular signatures of blastomeres and possessed developmental potency for all embryonic and extra-embryonic cell lineages. Here, we report the derivation of porcine EPSCs, which express key pluripotency genes, are genetically stable, permit genome editing, differentiate to derivatives of the three germ layers in chimeras and produce primordial germ cell-like cells in vitro. Under similar conditions, human embryonic stem cells and induced pluripotent stem cells can be converted, or somatic cells directly reprogrammed, to EPSCs that display the molecular and functional attributes reminiscent of porcine EPSCs. Importantly, trophoblast stem-cell-like cells can be generated from both human and porcine EPSCs. Our pathway-inhibition paradigm thus opens an avenue for generating mammalian pluripotent stem cells, and EPSCs present a unique cellular platform for translational research in biotechnology and regenerative medicine.

The Embryotrophic Activity of Oviductal Cell-derived Complement C3b and iC3b, a Novel Function of Complement Protein in Reproduction

The oviduct-derived embryotrophic factor, ETF-3, enhances the development of trophectoderm and the hatching process of treated embryos. Monoclonal anti-ETF-3 antibody that abolishes the embryotrophic activity of ETF-3 recognized a 115-kDa protein from the conditioned medium of immortalized human oviductal cells. Mass spectrometry analysis showed that the protein was complement C3. Western blot analysis using an antibody against C3 confirmed the cross-reactivities between anti-C3 antibody with ETF-3 and anti-ETF-3 antibody with C3 and its derivatives, C3b and iC3b. Both derivatives, but not C3, were embryotrophic. iC3b was most efficient in enhancing the development of blastocysts with larger size and higher hatching rate, consistent with the previous reported embryotrophic activity of ETF-3. Embryos treated with iC3b contained iC3b immunoreactivity. The oviductal epithelium produced C3 as evidenced by the presence of C3 immunoreactivity and mRNA in the human oviduct and cultured oviductal cells. Cyclical changes in the expression of C3 immunoreactivity and mRNA were also found in the mouse oviduct with the highest expression at the estrus stage. Molecules involving in the conversion of C3b to iC3b and binding of iC3b were present in the human oviduct (factor I) and mouse preimplantation embryo (Crry and CR3), respectively. In conclusion, the present data showed that the oviduct produced C3/C3b, which was converted to iC3b to stimulate embryo development.

Establishment and characterization of an immortalized human oviductal cell line

Human oviductal cells stimulate embryo development in vitro partly by the production of embryotrophic glycoproteins. The identity of these glycoproteins is not yet known mainly because oviductal samples are limited and that the cultured parental oviductal cells cannot produce sufficient amount of embryotrophic factors for characterization. In this study, human oviductal epithelial cells (OE) were immortalized by HPV 16 E6/E7 open reading frame (ORF) by retroviral expression. The characteristics of this immortalized cell line (OE-E6/E7) were compared to the parental OE. HPV 16 E6/E7 DNA was found only in OE-E6/E7 but not in OE. Human oviduct-specific glycoprotein, estrogen receptors, and cytokeratin were found in both cell types. Both OE and OE-E6/E7 possessed telomerase activities but the former had much lower activity. OE-E6/E7 also produced glycoproteins with chromatographic behavior similar to the embryotrophic glycoproteins derived from OE. These results showed that OE-E6/E7 retained a number of characteristics of OE. The development of preimplantation mouse embryo was significantly better after coculture with OE-E6/E7 when compared to medium alone culture in term of blastulation rates (52% vs. 32%) and blastocyst diameter (113.0 +/- 2.07 microm vs. 83.9 +/- 5.23 microm). This immortalized cell line can be used as a continuous and stable in vitro system for the study of the oviductal embryotrophic activity. Mol. Reprod. Dev. 59: 400-409, 2001.

Sirtuin 1 facilitates generation of induced pluripotent stem cells from mouse embryonic fibroblasts through the miR-34a and p53 pathways

Forced-expression of transcription factors can reprogram somatic cells into induced pluripotent stem cells (iPSC). Recent studies show that the reprogramming efficiency can be improved by inclusion of small molecules that regulate chromatin modifying enzymes. We report here that sirtuin 1 (SIRT1), a member of the sirtuin family of NAD⁺-dependent protein deacetylases, is involved in iPSC formation. By using an efficient mouse secondary fibroblast reprogramming system with doxycycline (DOX) inducible Yamanaka’s transcription factors delivered by piggyBac (PB) transposition (2°F/1B MEF), we show that SIRT1 knockdown decreased while resveratrol (RSV) increased the efficiency of iPSC formation. The treatments were associated with altered acetylated p53 and its downstream Nanog but not p21 expression. The stimulatory effect was also confirmed by SIRT1 over-expression, which stimulated the formation of colonies with induced Nanog and reduced p21 expression. Furthermore, the effects of RSV and SIRT1 knockdown on reprogramming were most pronounced during the initiation phase of reprogramming. MicroRNA-34a is a known regulator of SIRT1. Its inhibitor increased, while its mimics reduced iPSC formation. The stimulatory effect of SIRT1 during reprogramming was also confirmed in the primary MEF. RSV increased while tenovin-6, a small molecule that activates p53 through SIRT1 inhibition, suppressed reprogramming. In conclusion, SIRT1 enhances iPSC generation, in part, through deacetylation of p53, inhibition of p21 and enhancement of Nanog expression.

Increased fetal abortion rate in autoimmune thyroid disease is related to circulating TPO autoantibodies in an autoimmune thyroiditis animal model

OBJECTIVE

To determine the fertility and abortion rates in a mouse model of autoimmune thyroiditis and its relationship with circulating anti-thyroid peroxidase (TPO) antibody.

DESIGN

Experimental animal study.

SETTING

University research laboratory.

ANIMAL(S)

C57bl/6 mice.

INTERVENTION(S)

Female C57bl/6 mice immunized with recombinant mouse TPO (rmTPO) in complete Freund adjuvant (CFA) or glutathione-S-transferase (GST-CFA) were allowed to mate. The pregnant mice were killed on day 14 of pregnancy for assessment of fetal development. The effects of TPO antibody on preimplantation embryo development and implantation rate were also studied.

MAIN OUTCOME MEASURE(S)

Litter size, resorption rate, preimplantation embryo development, and implantation rate.

RESULT(S)

All of the mice immunized with rmTPO-CFA possessed anti-TPO antibody. They had reduced litter size and increased incidence of resorbed fetus compared with the control. Higher serum TSH levels, but not T(4) levels, were demonstrated after rmTPO-CFA immunization. Anti-TPO antibody bound to preimplantation embryos. Treatment of the embryos with the antibody marginally decreased the formation of 3/4-cell embryos but had no effect on the subsequent development and implantation compared with the nonimmune control sera.

CONCLUSION(S)

Autoimmune thyroiditis is associated with reduced fertility and higher incidence of fetal loss. The anti-TPO antibody may affect post-implantation embryo development, leading to fetal loss.

Preimplantation embryos cooperate with oviductal cells to produce embryotrophic inactivated complement-3b

Human oviductal epithelial (OE) cells produce complement protein 3 (C3) and its derivatives, C3b and inactivated complement-3b (iC3b). Among them, iC3b is the most potent embryotrophic molecule. We studied the production of iC3b in the oviductal cell/embryo culture system. In the immune system, C3 convertase converts C3 into C3b, and the conversion of C3b to iC3b requires factor I (fI) and its cofactors, such as factor H or membrane cofactor protein. Human oviductal epithelium and OE cells expressed mRNA and protein of the components of C3 convertase, including C2, C4, factor B, and factor D. The OE cell-conditioned medium contained active C3 convertase activity that was suppressed by C3 convertase inhibitor, H17 in a dose and time-dependent manner. Although the oviductal epithelium and OE cells produced fI, the production of its cofactor, factor H required for the conversion of C3b to iC3b, was weak. Thus, OE cell-conditioned medium was inefficient in producing iC3b from exogenous C3b. On the contrary, mouse embryos facilitated such conversion to iC3b, which was taken up by the embryos, resulting in the formation of more blastocysts of larger size. The facilitatory activity was mediated by complement receptor 1-related gene/protein Y (Crry) with known membrane cofactor protein activity on the trophectoderm of the embryos as anti-Crry antibody inhibited the conversion and embryotrophic activity of C3b in the presence of fI. In conclusion, human oviduct possesses C3 convertase activity converting C3 to C3b, and Crry of the preimplantation embryos may be involved in the production of embryotrophic iC3b on the surface of the embryos.

Establishment of a novel human embryonic stem cell-derived trophoblastic spheroid implantation model

STUDY QUESTION

Can human embryonic stem cell-derived trophoblastic spheroids be used to study the early stages of implantation?

SUMMARY ANSWER

We generated a novel human embryonic stem cell-derived trophoblastic spheroid model mimicking human blastocysts in the early stages of implantation.

WHAT IS KNOWN ALREADY

Both human embryos and choriocarcinoma cell line derived spheroids can attach onto endometrial cells and are used as models to study the early stages of implantation. However, human embryos are limited and the use of cancer cell lines for spheroid generation remains sub-optimal for research.

STUDY DESIGN, SIZE, DURATION

Experimental induced differentiation of human embryonic stem cells into trophoblast and characterization of the trophoblast.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Trophoblastic spheroids (BAP-EB) were generated by inducing differentiation of a human embryonic stem cell line, VAL3 cells with bone morphogenic factor-4, A83-01 (a TGF-β inhibitor), and PD173074 (a FGF receptor-3 inhibitor) after embryoid body formation. The expressions of trophoblastic markers and hCG levels were studied by real-time PCR and immunohistochemistry. BAP-EB attachment and invasion assays were performed on different cell lines and primary endometrial cells.

MAIN RESULTS AND THE ROLE OF CHANCE

After 48 h of induced differentiation, the BAP-EB resembled early implanting human embryos in terms of size and morphology. The spheroids derived from embryonic stem cells (VAL3), but not from several other cell lines studied, possessed a blastocoel-like cavity. BAP-EB expressed several markers of trophectoderm of human blastocysts on Day 2 of induced differentiation. In the subsequent days of differentiation, the cells of the spheroids differentiated into trophoblast-like cells expressing trophoblastic markers, though at levels lower than that in the primary trophoblasts or in a choriocarcinoma cell line. On Day 3 of induced differentiation, BAP-EB selectively attached onto endometrial epithelial cells, but not other non-endometrial cell lines or an endometrial cell line that had lost its epithelial character. The attachment rates of BAP-EB was significantly higher on primary endometrial epithelial cells (EEC) taken from 7 days after hCG induction of ovulation (hCG+7 day) when compared with that from hCG+2 day. The spheroids also invaded through Ishikawa cells and the primary endometrial stromal cells in the co-culture.

LIMITATIONS, REASONS FOR CAUTION

The attachment rates of BAP-EB were compared between EEC obtained from Day 2 and Day 7 of the gonadotrophin stimulated cycle, but not the natural cycles.

WIDER IMPLICATIONS OF THE FINDINGS

BAP-EB have the potential to be used as a test for predicting endometrial receptivity in IVF cycles and provide a novel approach to study early human implantation, trophoblastic cell differentiation and trophoblastic invasion into human endometrial cells.

Complement 3 deficiency impairs early pregnancy in mice

Human oviductal cells produce complement-3 (C3) and its derivative, iC3b. These molecules are important in immune responses. Our recent study suggested that iC3b also possessed embryotrophic activity and it stimulates the blastulation and hatching rates of in vitro cultured mouse embryos. The objective is to study the impact of C3 deficiency on early pregnancy in vivo using homozygous C3-deficient (C3KO) and wild-type (C3WT) mice. C3 protein was undetectable in the reproductive tissues of C3KO mice. Deficiency in C3 is associated with significantly longer estrous cycle (P = 0.037). No significant difference was found in the ovulation rate, total cell count in blastocysts and implantation rate between the wild-type and the C3KO mice, though C3KO mice tended to have lower values in the latter two parameters. On day 15 of pregnancy, C3KO mice had fewer conceptus (P < 0.001) and higher resorption rate (P < 0.001) than that of C3WT mice. The fetal and placental weights (P < 0.001) were lower in the C3KO mice. The placenta of C3KO mice had smaller spongiotrophoblast (P = 0.001) and labyrinth (P = 0.037). Deficiency in C3 is associated with mild impairment in early pregnancy including longer estrous cycle and higher resorption rates after implantation. The impairment may be related to compromised placental development leading to under-developed fetuses.

Demilune cell and parotid protein from murine oviductal epithelium stimulates preimplantation embryo development

In mammals, fertilization and early preimplantation embryo development occur in the oviduct. We hypothesized that interaction exists between the developing embryos and the maternal genital tract, such that the embryos modulate the physiology and gene expression of the oviduct so that it is conducive to their development. By comparing the gene expression patterns in mouse oviducts containing transferred preimplantation embryos with those of oviducts containing oocytes, we report here the characterization of demilune cell and parotid protein (Dcpp), which was up-regulated in the embryo-containing oviduct. Dcpp mRNA was highly expressed in the oviductal epithelium at the estrus stage. The Dcpp gene codes for a protein of 150 amino acids and contains a signal peptide suggestive of secretory function. The Dcpp mRNA level was maintained in the oviductal epithelium of pregnant females but decreased continuously in those of pseudopregnant mice. Exogenous estrogen stimulated the expression of Dcpp mRNA and protein in ovariectomized mice. The effect was abolished by an estrogen antagonist, ICI 182,780. Dcpp protein was present in mouse oviductal fluid but not in uterine fluid. More importantly, Dcpp immunoreactivity was found in embryos recovered from the oviduct but not in mature oocytes from the ovary. Supplementation of Dcpp to culture medium stimulated the development of mouse embryos to the blastocyst stage. Anti-Dcpp antibody decreased the beneficial effect of Dcpp on implantation of two-cell mouse embryos transferred to the oviducts of the foster mothers. In summary, our data demonstrated that Dcpp is highly expressed in the oviductal lumen in the presence of preimplantation embryos. It stimulates the growth of preimplantation embryos and may play an important role in embryo-maternal dialogue.

Let-7 derived from endometrial extracellular vesicles is an important inducer of embryonic diapause in mice

Embryonic diapause is a maternally controlled phenomenon. The molecule controlling the onset of the phenomenon is unknown. We demonstrated that overexpression of microRNA let-7a or incubation with let-7g-enriched extracellular vesicles from endometrial epithelial cells prolonged the in vitro survival of mouse blastocysts, which developed into live pups after having been transferred to foster mothers. Similar to in vivo dormant blastocysts, let-7-induced dormant blastocysts exhibited low level of proliferation, apoptosis, and nutrient metabolism. Let-7 suppressed c-myc/mTORC1 and mTORC2 signaling to induce embryonic diapause. It also inhibited ODC1 expression reducing biosynthesis of polyamines, which are known to reactivate dormant embryos. Furthermore, the overexpression of let-7 blocked trophoblast differentiation and implantation potential of human embryo surrogates, and prolonged survival of human blastocysts in vitro, supporting the idea that embryonic diapause was an evolutionary conserved phenomenon. In conclusion, let-7 is the main factor inducing embryonic diapause.

The Forkhead box transcription factor FOXM1 is required for the maintenance of cell proliferation and protection against oxidative stress in human embryonic stem cells

Human embryonic stem cells (hESCs) exhibit unique cell cycle structure, self-renewal and pluripotency. The Forkhead box transcription factor M1 (FOXM1) is critically required for the maintenance of pluripotency in mouse embryonic stem cells and mouse embryonal carcinoma cells, but its role in hESCs remains unclear. Here, we show that FOXM1 expression was enriched in undifferentiated hESCs and was regulated in a cell cycle-dependent manner with peak levels detected at the G2/M phase. Expression of FOXM1 did not correlate with OCT4 and NANOG during in vitro differentiation of hESCs. Importantly, knockdown of FOXM1 expression led to aberrant cell cycle distribution with impairment in mitotic progression but showed no profound effect on the undifferentiated state. Interestingly, FOXM1 depletion sensitized hESCs to oxidative stress. Moreover, genome-wide analysis of FOXM1 targets by ChIP-seq identified genes important for M phase including CCNB1 and CDK1, which were subsequently confirmed by ChIP and RNA interference analyses. Further peak set comparison against a differentiating hESC line and a cancer cell line revealed a substantial difference in the genomic binding profile of FOXM1 in hESCs. Taken together, our findings provide the first evidence to support FOXM1 as an important regulator of cell cycle progression and defense against oxidative stress in hESCs.

Embryotrophic factor-3 from human oviductal cells affects the messenger RNA expression of mouse blastocyst

Our previous results showed that embryotrophic factor-3 (ETF-3) from human oviductal cells increased the size and hatching rate of mouse blastocysts in vitro. The present study investigated the production of ETF-3 by an immortalized human oviductal cell line (OE-E6/E7) and the effects of ETF-3 on the mRNA expression of mouse embryos. The ETF-3 was purified from primary oviductal cell conditioned media using sequential liquid chromatographic systems, and antiserum against ETF-3 was raised. The ETF-3-supplemented Chatot-Ziomek-Bavister medium was used to culture Day 1 MF1 x BALB/c mouse embryos for 4 days. The ETF-3 treatment significantly enhanced the mouse embryo blastulation and hatching rate. The antiserum, at concentrations of 0.03-3%, abolished the embryotrophic effect of ETF-3. Positive ETF-3 immunoreactivity was detected in the primary oviductal cells, OE-E6/E7, and blastocysts derived from ETF-3 treatment. Vero cells (African Green Monkey kidney cell line), fibroblasts, and embryos cultured in control medium did not possess ETF-3 immunoreactivity. The mRNA expression patterns of the treated embryos were studied at the blastocyst stage by mRNA differential display reverse transcription-polymerase chain reaction (DDRT-PCR). The DDRT-PCR showed that some of the mRNAs were differentially expressed after ETF-3 treatment. Twelve of the differentially expressed mRNAs that had high homology with cDNA sequences in the GenBank were selected for further characterization. The differential expression of seven of these mRNAs (ezrin, heat shock 70-kDa protein, cytochrome c oxidase subunit VIIa-L precursor, proteinase-activated receptor 2, eukaryotic translation initiation factor 2beta, cullin 1, and proliferating cell nuclear antigen) was confirmed by semiquantitative RT-PCR. In conclusion, immortalized oviductal cells produce ETF-3, which influences mRNA expression of mouse blastocyst.

Oviductal microsomal epoxide hydrolase (EPHX1) reduces reactive oxygen species (ROS) level and enhances preimplantation mouse embryo development

Somatic cell-embryo coculture enhances embryo development in vitro by producing embryotrophic factor(s) and/or removing harmful substances from the culture environment. Yet, the underlying molecular mechanisms on how somatic cells remove the toxicants from the culture medium remain largely unknown. By using suppression subtractive hybridization, we identified a number of mouse oviductal genes that were up-regulated when developing preimplantation embryos were present in the oviduct. Epoxide hydrolase 1, microsomal (Ephx1 previously known as mEH) was one of these genes. EPHX1 detoxifies genotoxic compounds and participates in the removal of reactive oxygen species (ROS). The transcript of Ephx1 increases in the oviductal epithelium at the estrus stage and in Day 3 of pregnancy as well as in the uterus of ovariectomized mice injected with estrogen or progesterone. Human oviductal epithelial cells OE-E6/E7 express EPHX1 and improve mouse embryo development in vitro. Addition of an EPHX1 inhibitor, cyclohexene oxide (CHO) or 1,1,1-trichloropropene 2,3-oxide (TCPO), to the culture medium increased intracellular and extracellular ROS levels of OE-E6/E7 cells and suppressed the beneficial effect of the cells on embryo development; CHO and TCPO at these concentrations had no adverse effect on OE-E6/E7 growth and embryo development in vitro. Taken together, EPHX1 in oviductal cells may enhance the development of cocultured embryos by protecting them from oxidative stress. Our result supports the notion that somatic cell coculture may enhance embryo development via removal of deleterious substances in the culture medium.

Cell membrane proteins from oviductal epithelial cell line protect human spermatozoa from oxidative damage

OBJECTIVE

To study the potential protective action in vitro of oviductal epithelial cell membrane proteins against oxidative damage in human spermatozoa.

DESIGN

Prospective in vitro study.

SETTING

University research laboratory and infertility clinic.

PATIENT(S)

Semen from men attending the infertility clinic at the Queen Mary Hospital with normal semen parameters (World Health Organization, 2010).

INTERVENTION(S)

We studied the effect of oviductal epithelial cell membrane proteins on the sperm functions and endogenous antioxidant enzyme activities.

MAIN OUTCOME MEASURE(S)

Sperm motility, lipid peroxidation, DNA fragmentation, intracellular reactive oxygen species (ROS) level, superoxide dismutase, and glutathione peroxidase activities.

RESULT(S)

Oviductal epithelial cell membrane proteins bind to the human spermatozoa and protect them from ROS-induced damages in terms of sperm motility, membrane integrity, DNA integrity, and intracellular ROS level. Spermatozoa-oviduct epithelial cell interaction also enhances the antioxidant defenses in spermatozoa.

CONCLUSION(S)

Our results demonstrated the protective effects of spermatozoon-oviductal epithelial cell interaction against oxidative stress in human spermatozoa. The results enhance our understanding of the protective mechanism of oviduct on sperm functions.

Aberrant expression of angiopoietins-1 and -2 and vascular endothelial growth factor-A in peri-implantation endometrium after gonadotrophin stimulation

BACKGROUND

Ovarian stimulation affects normal endometrial development. The expression of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor-A (VEGF-A) and the vascular state in the peri-implantation endometrium in women with natural and gonadotrophin-stimulated cycles were compared.

METHODS

The expression of these angiogenesis-associated molecules in endometrial biopsies, collected on Day 7 after human chorionic gonadotrophin injection or luteinizing hormone surge in stimulated or natural cycles respectively, or at mid-luteal phase of women undergoing diagnositic laparoscopy, were analysed.

RESULTS

Women with gonadotrophin-stimulation had lower Ang-1, but higher Ang-2, mRNA and protein expression (P < 0.05), and increased concentrations of von Willebrand factor (vWF) and blood vessel density than those with natural cycles (P < 0.05). Although stimulated cycles had higher VEGF-A mRNA expression (P = 0.023), VEGF-A protein expression was similar between the groups. Lower Ang-1/Ang-2 but higher Ang-2/VEGF-A mRNA ratios (P = 0.025) were found after gonadotrophin-stimulation. The ratios were negatively (P < 0.001) and positively correlated (P < 0.001) with estradiol levels, respectively. Cyclical changes in Ang-1 and Ang-2, but not in VEGF-A expression were noted.

CONCLUSIONS

The decreased Ang-1 concentration and Ang-1/Ang-2 ratio and the increased Ang-2 concentration, with the increased vWF concentration and blood vessel density, in stimulated cycles suggests advanced endometrial angiogenesis after gonadotrophin-stimulation.

Phospholipid transfer protein (PLTP) mRNA expression is stimulated by developing embryos in the oviduct

In mammal, fertilization and early preimplantation embryo development occurs in the oviduct. Evidence is accumulating that the oviductal epithelia secrete various biomolecules to the lumen during the secretory phase of the estrus cycle to enhance embryo development. This secretory activity of the oviduct is under the regulation of steroid hormones. Observations also suggested that the gametes and embryos modulate the physiology and gene-expressing pattern of the oviduct. However, the underlying molecular changes remain elusive. We hypothesize that the developing embryos interact with the surrounding environment and affect the gene expression patterns of the oviduct, thereby modulating the oviductal secretory activity conducive to the preimplantation embryo development. To test this hypothesis, suppression subtractive hybridization (SSH) was used to compare the gene expressions in mouse oviduct containing transferred in vitro cultured preimplantation embryos with that of oviduct containing oocytes during the preimplantation period. We reported here the identification and characterization of phospholipids transfer protein (PLTP), which is highly expressed in the embryo-containing oviduct and localized at the oviductal epithelium by in situ hybridization. PLTP contains signal peptide putative for secretory function. More importantly, PLTP mRNA increases in the oviductal epithelia of pregnant, but not pseudo-pregnant mice when assayed by real-time PCR. Taken together, our data suggested that PLTP may play important role(s) during in vivo preimplantation embryo development. This molecule would be a target to delineate the mechanisms and the roles of oviductal secretory proteins on early embryonic development.

Vero cells, but not oviductal cells, increase the hatching frequency and total cell count of mouse blastocysts partly by changing energy substrate concentrations in culture medium

PURPOSE

To investigate the embryotrophic mechanisms of Vero and oviductal cells coculture.

METHODS

Mouse embryos were cultured in Chatot, Ziomek, and Bavister medium (CZB), in modified CZB media (MM) with nutrient concentrations adjusted to that found in conditioned media after different periods of Vero cells or oviductal cells culture, in reconstituted medium (RM) containing the purified > 100-kDa components of Vero cell conditioned medium that had been reconstituted with CZB medium, and cocultured with Vero cells with an interposing membrane.

RESULTS

The blastulation rate was not different among embryos cultured in different Vero-cell-derived MMs. Nine-hour Vero-cell-derived MM significantly increased the total cell number and hatching frequency of the embryos. There was no difference in these parameters with oviductal-cell-derived MMs. The RM of Vero cells did not possess embryotrophic activity. The presence of a porous membrane between Vero cells and embryos did not affect the embryotrophic activity of coculture.

CONCLUSIONS

Vero cells, but not oviductal cells, improved mouse embryo development partly by modifying the energy substrate concentration in culture medium.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the differentiation of embryonic stem cells towards pancreatic lineage and pancreatic beta cell function

Animal and epidemiological studies demonstrated association of persistent exposure of TCDD, an endocrine disrupting chemical, to susceptibility of type 2 diabetes (T2D). High doses of TCDD were commonly employed in experimental animals to illustrate its diabetogenic effects. Data linking the epigenetic effects of low doses of TCDD on embryonic cells to T2D susceptibility risks is very limited. To address whether low dose exposure to TCDD would affect pancreatic development, hESCs pretreated with TCDD at concentrations similar to human exposure were differentiated towards pancreatic lineage cells, and their global DNA methylation patterns were determined. Our results showed that TCDD-treated hESCs had impaired pancreatic lineage differentiation potentials and altered global DNA methylation patterns. Four of the hypermethylated genes (PRKAG1, CAPN10, HNF-1B and MAFA) were validated by DNA bisulfite sequencing. PRKAG1, a regulator in the AMPK signaling pathway critical for insulin secretion, was selected for further functional study in the rat insulinoma cell line, INS-1E cells. TCDD treatment induced PRKAG1 hypermethylation in hESCs, and the hypermethylation was maintained after pancreatic progenitor cells differentiation. Transient Prkag1 knockdown in the INS-1E cells elevated glucose stimulated insulin secretions (GSIS), possibly through mTOR signaling pathway. The current study suggested that early embryonic exposure to TCDD might alter pancreatogenesis, increasing the risk of T2D.

Hyperglycemia impedes definitive endoderm differentiation of human embryonic stem cells by modulating histone methylation patterns

Exposure to maternal diabetes during fetal growth is a risk factor for the development of type II diabetes (T2D) in later life. Discovery of the mechanisms involved in this association should provide valuable background for therapeutic treatments. Early embryogenesis involves epigenetic changes including histone modifications. The bivalent histone methylation marks H3K4me3 and H3K27me3 are important for regulating key developmental genes during early fetal pancreas specification. We hypothesized that maternal hyperglycemia disrupted early pancreas development through changes in histone bivalency. A human embryonic stem cell line (VAL3) was used as the cell model for studying the effects of hyperglycemia upon differentiation into definitive endoderm (DE), an early stage of the pancreatic lineage. Hyperglycemic conditions significantly down-regulated the expression levels of DE markers SOX17, FOXA2, CXCR4 and EOMES during differentiation. This was associated with retention of the repressive histone methylation mark H3K27me3 on their promoters under hyperglycemic conditions. The disruption of histone methylation patterns was observed as early as the mesendoderm stage, with Wnt/β-catenin signaling being suppressed during hyperglycemia. Treatment with Wnt/β-catenin signaling activator CHIR-99021 restored the expression levels and chromatin methylation status of DE markers, even in a hyperglycemic environment. The disruption of DE development was also found in mouse embryos at day 7.5 post coitum from diabetic mothers. Furthermore, disruption of DE differentiation in VAL3 cells led to subsequent impairment in pancreatic progenitor formation. Thus, early exposure to hyperglycemic conditions hinders DE development with a possible relationship to the later impairment of pancreas specification.

Embryotrophic factor-3 from human oviductal cells enhances proliferation, suppresses apoptosis and stimulates the expression of the β1 subunit of sodium–potassium ATPase in mouse embryos

BACKGROUND

Embrytrophic factor-3 (ETF-3) from human oviductal cells enhanced the development of mouse preimplantation embryos. This report studied the embryotrophic mechanisms of the molecule.

METHODS AND RESULTS

Mouse embryos were incubated with ETF-3 for 24 h at different stages of development. ETF-3 treatment between 96 and 120 h post-HCG increased the cell count of blastocysts, whilst treatment between 72 and 96 h post-HCG enhanced the expansion and hatching of the blastocysts. ETF-3 increased the cell number of the embryos by suppressing apoptosis and increasing proliferation as determined by TUNEL and bromodeoxyuridine uptake assays, respectively. Real-time quantitative PCR showed that the in vivo developed and ETF-3-treated blastocysts had a significantly higher mRNA copy number of Na/K-ATPase-beta1, but not of hepsin, than that of blastocysts cultured in medium alone. The former gene was associated with cavitation of blastocysts while the latter was related to hatching of blastocyst. The beneficial effect of ETF-3 on blastocyst hatching was also seen when ETF-3-supplemented commercially available sequential culture medium for human embryo culture was used to culture mouse embryos.

CONCLUSIONS

ETF-3 improves embryo development by enhancing proliferation, suppressing apoptosis and stimulating expression of genes related to blastocyst cavitation. Supplementating human embryo culture medium with ETF-3 may improve the success rate in clinical assisted reproduction.

DNA Damage Response and Cell Cycle Regulation in Pluripotent Stem Cells

Pluripotent stem cells (PSCs) hold great promise in cell-based therapy because of their pluripotent property and the ability to proliferate indefinitely. Embryonic stem cells (ESCs) derived from inner cell mass (ICM) possess unique cell cycle control with shortened G1 phase. In addition, ESCs have high expression of homologous recombination (HR)-related proteins, which repair double-strand breaks (DSBs) through HR or the non-homologous end joining (NHEJ) pathway. On the other hand, the generation of induced pluripotent stem cells (iPSCs) by forced expression of transcription factors (Oct4, Sox2, Klf4, c-Myc) is accompanied by oxidative stress and DNA damage. The DNA repair mechanism of DSBs is therefore critical in determining the genomic stability and efficiency of iPSCs generation. Maintaining genomic stability in PSCs plays a pivotal role in the proliferation and pluripotency of PSCs. In terms of therapeutic application, genomic stability is the key to reducing the risks of cancer development due to abnormal cell replication. Over the years, we and other groups have identified important regulators of DNA damage response in PSCs, including FOXM1, SIRT1 and PUMA. They function through transcription regulation of downstream targets (P53, CDK1) that are involved in cell cycle regulations. Here, we review the fundamental links between the PSC-specific HR process and DNA damage response, with a focus on the roles of FOXM1 and SIRT1 on maintaining genomic integrity.

Bisphenol compounds regulate decidualized stromal cells in modulating trophoblastic spheroid outgrowth and invasion in vitro†

Bisphenol A (BPA) is commonly found in epoxy resins used in the manufacture of plastic coatings in food packaging and beverage cans. There is a growing concern about BPA as a weak estrogenic compound that can affect human endocrine function. Chemicals structurally similar to BPA, such as bisphenol F (BPF) and bisphenol S (BPS), have been developed as substitutes in the manufacturing industry. Whether these bisphenol substitutes have adverse effects on human endocrine and reproductive systems remains largely unknown. This study investigated the effects of BPA, BPF, and BPS on regulating the function of decidualized human primary endometrial stromal cells on trophoblast outgrowth and invasion by indirect and direct co-culture models. All three bisphenols did not affect the stromal cell decidualization process. However, BPA- and BPF-treated decidualized stromal cells stimulated trophoblastic spheroid invasion in the indirect coculture model. The BPA-treated decidualized stromal cells had upregulated expressions of several invasion-related molecules including leukemia inhibitory factor (LIF), whereas both BPA- and BPF-treated decidualized stromal cells had downregulated expressions of anti-invasion molecules including plasminogen activator inhibitor type 1 (PAI-1) and tumor necrosis factor (TNFα) . Taken together, BPA and BPF altered the expression of invasive and anti-invasive molecules in decidualized stromal cells modulating its function on trophoblast outgrowth and invasion, which could affect the implantation process and subsequent pregnancy outcome.