Few signaling molecules have as much potential to influence the developing mammal as the nucleoside adenosine. Adenosine levels increase rapidly with tissue hypoxia and inflammation. Adenosine antagonists include the methylxanthines caffeine and theophylline. The receptors that transduce adenosine action are the A1, A2a, A2b, and A3 adenosine receptors (A1AR, A2aAR, A2bAR, and A3AR). We examined how adenosine acts via A1ARs to influence embryo development. Transgenic mice were studied along with embryo cultures. Embryos lacking A1ARs were markedly growth retarded following intrauterine hypoxia exposure. Studies of mice selectively lacking A1AR in the heart identify the heart as a key site of adenosine's embryo-protective effects. Studies of isolated embryos showed that adenosine plays a key role in modulating embryo cardiac function, especially in the setting of hypoxia. When pregnant mice were treated during embryogenesis with the adenosine antagonist caffeine, adult mice had abnormal heart function. Adenosine acts via A1ARs to play an essential role in protecting the embryo against intrauterine stress, and adenosine antagonists, including caffeine, may be an unwelcome exposure for the embryo.

Mammalian preimplantation embryos normally develop within the protected environment of the female reproductive tract, which virtually precludes studies on embryogenesis in situ. Information must therefore be derived from experiments on cultured embryos. Consequently, studies on the epigenetic regulation of embryogenesis have long been interwoven with efforts to formulate culture media capable of sustaining normal development. In this review, comparative information on epigenetic regulation of embryo development is discussed, including information on energy substrate and amino acid preferences of embryos. Advantages of simple versus complex culture media, and of substituting serum albumin or synthetic macromolecules for serum, are discussed. Some potential pitfalls of co-culture are described. Culture appears to induce anomalies in embryo metabolism, which may derive from disturbed intracellular pH. Rationales for selecting endpoints to evaluate the outcome of experiments are considered, including incorporation of timing of embryo development into the analysis. Poor experimental design and/or data analysis can detract from or even negate the value of data obtained from embryo culture; examples are examined to help correct this problem. All of these points are discussed with a view to using data on the needs of embryos for making improvements in the design of culture media, so that higher yields and increased viability of embryos are achieved.

Select members of the Wnt family of secreted glycoproteins have been implicated in inducing the myogenic determinant genes Pax3, MyoD and Myf5 during mammalian embryogenesis, but the mechanism of induction has not been defined. We describe an unexpected role for protein kinase A (PKA) signalling via CREB in this induction. Using a combination of in vitro explant assays, mutant analysis and gene delivery into mouse embryos cultured ex vivo, we demonstrate that adenylyl cyclase signalling via PKA and its target transcription factor CREB are required for Wnt-directed myogenic gene expression. Wnt proteins can also stimulate CREB-mediated transcription, providing evidence for a Wnt signalling pathway involving PKA and CREB. Our findings raise the possibility that PKA/CREB signalling may also contribute to other Wnt-regulated processes in embryonic patterning, stem cell renewal and cancer.

It was reported recently that human fibroblasts can be reprogrammed into a pluripotent state that resembles that of human embryonic stem (hES) cells. This was achieved by ectopic expression of four genes followed by culture on mouse embryonic fibroblast (MEF) feeders under a condition favoring hES cell growth. However, the efficiency of generating human induced pluripotent stem (iPS) cells is low, especially for postnatal human fibroblasts. We started supplementing with an additional gene or bioactive molecules to increase the efficiency of generating iPS cells from human adult as well as fetal fibroblasts. We report here that adding SV40 large T antigen (T) to either set of the four reprogramming genes previously used enhanced the efficiency by 23-70-fold from both human adult and fetal fibroblasts. Discernible hES-like colonies also emerged 1-2 weeks earlier if T was added. With the improved efficiency, we succeeded in replacing MEFs with immortalized human feeder cells that we previously established for optimal hES cell growth. We further characterized individually picked hES-like colonies after expansion (up to 24 passages). The majority of them expressed various undifferentiated hES markers. Some but not all the hES-like clones can be induced to differentiate into the derivatives of the three embryonic germ layers in both teratoma formation and embryoid body (EB) formation assays. These pluripotent clones also differentiated into trophoblasts after EB formation or bone morphogenetic protein 4 induction as classic hES cells. Using this improved approach, we also generated hES-like cells from homozygous fibroblasts containing the sickle cell anemia mutation Hemoglobin Sickle. Disclosure of potential conflicts of interest is found at the end of this article.

Culture of preimplantation embryos affects gene expression. The magnitude of the effect on the global pattern of gene expression, however, is not known. We compared global patterns of gene expression in blastocysts cultured from the one-cell stage in either Whitten's medium or KSOM + amino acids (KSOM/AA) with that of blastocysts that developed in vivo, using the Affymetrix MOE430A chip. The analysis revealed that expression of 114 genes was affected after culture in Whitten's medium, whereas only 29 genes were mis-expressed after culture in KSOM/AA. Expression Analysis Systematic Explorer was used to identify biological and molecular processes that are perturbed after culture and indicated that genes involved in protein synthesis, cell proliferation and transporter function were down-regulated after culture in Whitten's medium. A common set of genes involved in transporter function was also down-regulated after culture in KSOM/AA. These results provide insights as to why embryos develop better in KSOM/AA than in Whitten's medium, and highlight the power of microarray analysis to assess global patterns of gene expression.

BACKGROUND Single-embryo transfer has been recommended to reduce the incidence of multiple gestations when in vitro fertilization is performed in women under 36 years of age. We designed a prospective, randomized, controlled trial to determine whether there were any differences in the rates of pregnancy and delivery between women undergoing transfer of a single cleavage-stage (day 3) embryo and those undergoing transfer of a single blastocyst-stage (day 5) embryo. METHODS We studied 351 infertile women under 36 years of age who were randomly assigned to undergo transfer of either a single cleavage-stage embryo (176 patients) or a single blastocyst-stage embryo (175 patients). Multifollicular ovarian stimulation was performed with a gonadotropin-releasing hormone antagonist and recombinant follicle-stimulating hormone. RESULTS The study was terminated early after a prespecified interim analysis (which included 50 percent of the planned number of patients) found a higher rate of pregnancy among women undergoing transfer of a single blastocyst-stage embryo (P=0.02). The rate of delivery was also significantly higher in this group than in the group undergoing transfer of a single cleavage-stage embryo (32.0 percent vs. 21.6 percent; relative risk, 1.48; 95 percent confidence interval, 1.04 to 2.11). Two multiple births occurred, both of monozygotic twins, both of which were in the group undergoing transfer of a single cleavage-stage embryo. CONCLUSIONS These findings support the transfer of a single blastocyst-stage (day 5) embryo in infertile women under 36 years of age.

Outside cells of the preimplantation mouse embryo form the trophectoderm (TE), a process requiring the transcription factor Tead4. Here, we show that transcriptionally active Tead4 can induce Cdx2 and other trophoblast genes in parallel in embryonic stem cells. In embryos, the Tead4 coactivator protein Yap localizes to nuclei of outside cells, and modulation of Tead4 or Yap activity leads to changes in Cdx2 expression. In inside cells, Yap is phosphorylated and cytoplasmic, and this involves the Hippo signaling pathway component Lats. We propose that active Tead4 promotes TE development in outside cells, whereas Tead4 activity is suppressed in inside cells by cell contact- and Lats-mediated inhibition of nuclear Yap localization. Thus, differential signaling between inside and outside cell populations leads to changes in cell fate specification during TE formation.

Oxygen concentrations used during in vitro embryo culture can influence embryo development, cell numbers, and gene expression. Here we propose that the preimplantation bovine embryo possesses a molecular mechanism for the detection of, and response to, oxygen, mediated by a family of basic helix-loop-helix transcription factors, the hypoxia-inducible factors (HIFs). Day 5 compacting bovine embryos were cultured under different oxygen tensions (2%, 7%, 20%) and the effect on the expression of oxygen-regulated genes, development, and cell number allocation and HIFalpha protein localization were examined. Bovine in vitro-produced embryos responded to variations in oxygen concentration by altering gene expression. GLUT1 expression was higher following 2% oxygen culture compared with 7% and 20% cultured blastocysts. HIF mRNA expression (HIF1alpha, HIF2alpha) was unaltered by oxygen concentration. HIF2alpha protein was predominantly localized to the nucleus of blastocysts. In contrast, HIF1alpha protein was undetectable at any oxygen concentration or in the presence of the HIF protein stabilizer desferrioxamine (DFO), despite being detectable in cumulus cells following normal maturation conditions, acute anoxic culture, or in the presence of DFO. Oxygen concentration also significantly altered inner cell mass cell proportions at the blastocyst stage. These results suggest that oxygen can influence gene expression in the bovine embryo during postcompaction development and that these effects may be mediated by HIF2alpha.

Human embryonic stem (hES) cells are pluripotent cells derived from the inner cell mass cells of blastocysts with the potential to maintain an undifferentiated state indefinitely. Fully characterised hES cell lines express typical stem cell markers, possess high levels of telomerase activity, show normal karyotype and have the potential to differentiate into numerous cell types under in vitro and in vivo conditions. Therefore, hES cells are potentially valuable for the development of cell transplantation therapies for the treatment of various human diseases. However, there are a number of factors which may limit the medical application of hES cells:(a) continuous culture of hES cells in an undifferentiated state requires the presence of feeder layers and animal-based ingredients which incurs a risk of cross-transfer of pathogens;(b) hES cells demonstrate high genomic instability and non-predictable differentiation after long-term growth; and (c) differentiated hES cells express molecules which could cause immune rejection. In this review we summarise recent progress in the derivation and growth of undifferentiated hES cells and their differentiated progeny, and the problems associated with these techniques. We also examine the potential use of the therapeutic cloning technique to derive isogenic hES cells.

A retrospective cohort study was conducted on 201 women aged 28-44 years, each of whom underwent one cycle of IVF-embryo transfer with fresh, intracytoplasmic sperm injection (ICSI)-derived 7- to 10-cell embryos, transferred 72 h after oocyte retrieval. Samples of media surrounding separately cultured embryos were collected 46 h post-ICSI and stored for subsequent specific enzyme-linked immunosorbent assay. A total of 594 embryos (from own or donor oocytes) were transferred to 201 women. Group A comprised 159 recipients under 39 years and group B compromised 42 recipients aged 39-44 years. Groups A-1 and B-1 recipients had at least one embryo that tested above the geometric mean for soluble human leukocyte antigen-G (sHLA-G)('positive expression') transferred. In groups A-2 and B-2, all embryos transferred expressed sHLA-G below the geometric mean ('negative expression'). In group A-1, 72/101 women (71%) achieved ultrasound confirmed (clinical), viable (cardiac activity observed) pregnancies. The implantation rate per embryo (IR) was 38%. In group A-2, 13/58 (22%) achieved viable clinical pregnancies. The IR was 9%. In group B-1, the viable clinical pregnancy rate was 52%(15/29) and the IR was 25% compared with a viable clinical pregnancy rate of 15%(2/13) and an IR of 5% in group B-2. The results of this study suggest that by selecting specific embryos for transfer based on their individual sHLA-G expression, pregnancy and implantation rates can be maximized while the number of embryos transferred can be reduced, thereby minimizing the incidence of high-order multiple pregnancies.

The current success rate of cloned mice from adult somatic cell nuclei is very low, whereas it is relatively high for cloned mice from ES cell nuclei. In this experiment, we examined whether the success rate of cloning from somatic cells could be improved via nuclear transfer embryonic stem cells (ntES cells) established from somatic cell nuclei. We obtained 11 cloned mice and 68 ntES cell lines from the somatic cell nuclei of 7 mice, and cloned 41 mice were cloned from the ntES cell nuclei. Unexpectedly, the overall success rate of cloning from ntES cell nuclei in this series was no better than when using somatic cell nuclei. Interestingly, full-term cloned mice were produced only via ntES cells from two individuals, but not by direct nuclear transfer from the somatic cells, and vice versa. Ultimately, we were able to obtain clone mice from 6 out of 7 individuals using either somatic cells or ntES cells. Thus, although ntES cells as donor nuclei do not absolutely assure a better success rate for mouse cloning than somatic cells, to preserve and clone valuable individuals, we recommend that ntES cell lines be established. These can then be used as an unlimited source of donor nuclei for nuclear transfer, and thus complement conventional somatic cell nuclear transfer cloning approaches.