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Hui Li, Yu-Han Meng, Wen-Qing Shang, Li-Bing Liu, Xuan Chen, Min-Min Yuan, Li-Ping Jin, Ming-Qing Li and Da-Jin Li

Chemokine CCL24, acting through receptor CCR3, is a potent chemoattractant for eosinophil in allergic diseases and parasitic infections. We recently reported that CCL24 and CCR3 are co-expressed by trophoblasts in human early pregnant uterus. Here we prove with evidence that steroid hormones estradiol (E), progesterone (P), and human chorionic gonadotropin (hCG), as well as decidual stromal cells (DSCs) could regulate the expression of CCL24 and CCR3 of trophoblasts. We further investigate how trophoblast-derived CCL24 mediates the function of trophoblasts in vitro, and conclude that CCL24/CCR3 promotes the proliferation, viability and invasiveness of trophoblasts. In addition, analysis of the downstream signaling pathways of CCL24/CCR3 show that extracellular signal-regulated kinases (ERK1/2) and phosphoinositide 3-kinase (PI3K) pathways may contribute to the proliferation, viability and invasiveness of trophoblasts by activating intracellular molecules Ki67 and matrix metallopeptidase 9 (MMP9). However, we did not observe any inhibitory effect on trophoblasts when blocking c-Jun N-terminal kinase (JNK) or p38 pathways. In conclusion, our data suggests that trophoblast-derived CCL24 at the maternal-fetal interface promotes trophoblasts cell growth and invasiveness by ERK1/2 and PI3K pathways. Meanwhile, pregnancy-related hormones (P and hCG), as well as DSCs could up-regulate CCL24/CCR3 expression in trophoblasts, which may indirectly influence the biological functions of trophoblasts. Thus, our results provide a possible explanation for the growth and invasion of trophoblasts in human embryo implantation.

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Joëlle A Desmarais, Mingju Cao, Andrew Bateman and Bruce D Murphy

Embryo implantation in the mink is preceded by a variable but obligate period of delay in development. Under the influence of progesterone and unknown luteal factors, the mink embryo implants 11–13 days following its exit from diapause. Recent work suggests that progranulin, a growth factor and secreted glycoprotein, is involved in trophoblast proliferation, placental development and endometrial differentiation in the mouse. Using the mink model of delayed implantation and endotheliochorial placentation, we examined the spatiotemporal distribution of progranulin in trophoblast and endometrium during pre- and early post-implantation gestation in vivo. A partial sequence of the mink progranulin gene was cloned and sequenced. Comparative sequence analysis revealed that exons 1 and 2 of mink progranulin share 86.6, 82.4, and 94.9% of nucleic acid sequence identity with the human, mouse, and dog sequences respectively, and indicated that the invariable residues of the cysteine-rich motifs of progranulin are well conserved in the mink sequence. By in situ hybridization, we show that mink progranulin transcript is present in the cytotrophoblast and in epithelial and stromal endometrial cells at the site of implantation and during early placental formation. Immunohistochemistry revealed the progranulin protein to be strongly expressed in endometrial luminal and glandular epithelium around the time of implantation. In the incipient labyrinth, progranulin expression is localized to cytotrophoblasts and fetal capillaries, as well as to the hypertrophied maternal endothelial cells. This study demonstrates that high levels of progranulin expression correspond to active cell proliferation, remodeling, and angiogenesis occurring during the establishment of the placenta in the mink.

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GA Thouas, GM Jones and AO Trounson

A novel system of in vitro culture termed the 'glass oviduct' or 'GO' culture system is described. Mouse zygotes were cultured in pairs to the blastocyst stage in open-ended 1 microl glass capillaries. 'GO' culture supported the development of significantly more hatching or hatched blastocysts than did a standard microdroplet (10 zygotes per 20 microl) control culture (48.3 versus 3.3%, respectively). 'GO' bslastocysts contained significantly larger populations of cells (92+/-3 versus 75+/-3), and inner cell mass (25+/-1 versus 21+/-1) and trophectoderm (68+/-2 versus 53+/-3) subpopulations, compared with microdroplet-derived blastocysts. Before blastulation, 'GO'-derived morulae were found to contain significantly more cells than microdroplet-derived morulae (27+/-0.7 versus 14+/-0.5). After implantation, 'GO' blastocysts formed fetuses at a similar rate to microdroplet-derived blastocysts (55 versus 62%), but at a lower rate than blastocysts derived in vivo (80%). 'GO'- and microdroplet-derived fetuses were similar in wet weight to each other (0.412 and 0.415 g, respectively) but were heavier than fetuses derived from flushed blastocysts (0.390 g). An additional experiment investigated whether the beneficial effect of 'GO' culture was due to the significantly increased embryo density. Proportions of hatching or hatched blastocysts after 'GO' culture (50%) were higher than after standard microdroplet culture (7.6%), but were not different from culture in high embryo density microdroplets (20 zygotes per 10 microl; 42%). 'GO' blastocysts contained more cells (79.6+/-2.1) than did standard microdroplet-derived blastocysts (68.7+/-2.0), but were similar to high density microdroplet-derived blastocysts (85.8+/-2.7). Similarly, 'GO' blastocysts contained more trophectoderm cells (62.2+/-2.0) than did standard microdroplet-derived blastocysts (52.7+/-1.7), but were similar to the high density microdroplet blastocysts (68.8+/-2.5). Numbers of inner cell mass cells ('GO', standard microdroplet and high density microdroplet culture) were not different from each other (17.4+/-0.5, 16+/-0.5 and 17+/-0.4, respectively). In conclusion, the 'GO' culture system represents an alternative method to the microdroplet system for small numbers of preimplantation embryos, without detriment to implantation potential.

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Blood sera and yolk-sac fluids were collected from pregnant tammar wallabies and analysed for free amino acids, proteins and glucose.

The total and individual concentrations of free amino acids at all stages of pregnancy were higher in yolk-sac fluids than in sera, with the exception of glutamic acid, which was at a higher concentration in serum.

Protein concentrations were lower in yolk-sac fluids than in the serum but the number of protein components in yolk-sac fluid, as determined by acrylamide gel electrophoresis, increased after implantation.

Glucose concentration in yolk-sac fluids also increased with the age of the embryo. These values were lower than those in sera before implantation, but higher than in sera after implantation.

These results indicate that the transfer and accumulation of nutrient materials in the yolk-sac is not only by simple diffusion from maternal serum, but also by selective transfer through the yolk-sac placenta.

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Z. Zhu, L. Cheng, Z. Tsui, S. Hakomori and B. A. Fenderson

Summary. The glycolipids of nonpregnant and pregnant rabbit endometrium were characterized using a combination of biochemical and immunochemical techniques. Quantitative analyses indicated a 70% decline in acidic glycolipid (ganglioside) content during early pregnancy (day 6), and a 2·5-fold increase in neutral glycolipid content during later pregnancy (day 26). The major gangliosides of rabbit endometrium were identified by thin-layer chromatography as GM3 and GD3, with minor amounts of GM1, GD1 a and GT1b. The major neutral glycolipids were identified similarly as globo-series structures Gb3 and Gb4. Monoclonal antibodies (mAbs) directed to glycolipid antigens permitted the detection of additional glycolipid species, including sialylated, sulfated and fucosylated lacto-series structures. Difucosyl Ley structure (defined by mAb AH-6) and sulfated-galactosyl structure (defined by mAb VESP 6·2) were identified by indirect immunofluorescence along the luminal surface of the endometrium during the implantation period. Rapid changes in the glycolipid composition of endometrial cells during early pregnancy may facilitate embryo adhesion and trophectoderm outgrowth during implantation.

Keywords: endometrium; glycolipids; pregnancy; immunohistochemistry; rabbit

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Removal of the conceptuses (decidua+embryos) from the uterus of the guinea-pig between the 9th and 15th days after mating allowed the recurrence of oestrus at, or only slightly after, the time it would have occurred had not fertile mating taken place. The transfer of a single 6-day blastocyst to the uterus of unmated cycling animals resulted in pregnancy in three of six animals in which the cycles of the host and donor were synchronized. Normal development was never observed after transfer of 9- to 11-day implanted conceptuses (without associated decidua) to the uterus. Blastocysts and 9- to 10-day implanted conceptuses transferred to the spleen developed in eight of thirteen animals. The ectopic placental tissue did not prevent the normal recurrence of oestrus. Grafts developing from a single 11- to 12-day implanted conceptus in the spleen maintained the corpora lutea and delayed oestrus until after the 20th day in thirteen of twenty-four animals. The guinea-pig placenta appears to produce a systemically-active substance capable of neutralizing the luteolytic abilities of the uterus. This anti-luteolytic hormone probably acts only between Days 12 to 25 after mating.

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The Pontamine Blue reaction (Finn & McLaren, 1967) reflects the increased vascular permeability at the site of blastocyst attachment (Psychoyos, 1960) which presages cellular changes in the uterus associated with implantation of the embryo (Finn & McLaren, 1967; Boshier, 1968, 1969). Leakage of this macromolecular dye, therefore, precedes any modifications in uterine histology that can be associated with attachment of the embryo. The increase in vascular permeability has been considered a sine qua non for decidua formation (Psychoyos, 1961). In this study, the Pontamine Blue reaction was used (1) as confirmation of earlier observations (Boshier, 1968) that implantation in sheep occurs on the 16th day of pregnancy, and (2) to determine whether this reaction is present in sheep, a species in which there is no evidence of decidual cell formation preceding the uterine epithelial changes which occur at the implantation site (Boshier, 1968, 1969). New Zealand Romney ewes of different ages were killed 15 min after an intravenous injection, lasting over 60 sec, of that volume of a 0·5% solution of Pontamine Sky Blue 5BX in normal saline which was equivalent to 10% of the recipient's blood volume [calculated as (lb body wt×0·07 litres)/2·2]. Uteri containing extra-embryonic membranes were examined under cold normal saline, and the caruncular and inter-caruncular areas were compared for difference in colouration. Only those uteri in which there was a differentially
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Daniel R Arnold, Vilceu Bordignon, Réjean Lefebvre, Bruce D Murphy and Lawrence C Smith

Abnormal placental development limits success in ruminant pregnancies derived from somatic cell nuclear transfer (SCNT), due to reduction in placentome number and consequently, maternal/fetal exchange. In the primary stages of an epithelial–chorial association, the maternal/fetal interface is characterized by progressive endometrial invasion by specialized trophoblast binucleate/giant cells (TGC). We hypothesized that dysfunctional placentation in SCNT pregnancies results from aberration in expression of genes known to be necessary for trophoblast proliferation (Mash2), differentiation (Hand1), and function (IFN-τ and PAG-9). We, therefore, compared the expression of these factors in trophoblast from bovine embryos derived from artificial insemination (AI), in vitro fertilization (IVF), and SCNT prior to (day 17) and following (day 40 of gestation) implantation, as well as TGC densities and function. In preimplantation embryos, Mash2 mRNA was more abundant in SCNT embryos compared to AI, while Hand1 was highest in AI and IVF relative to SCNT embryos. IFN-τ mRNA abundance did not differ among groups. PAG-9 mRNA was undetectable in SCNT embryos, present in IVF embryos and highest in AI embryos. In postimplantation pregnancies, SCNT fetal cotyledons displayed higher Mash2 and Hand1 than AI and IVF tissues. Allelic expression of Mash2 was not different among the groups, which suggests that elevated mRNA expression was not due to altered imprinting status of Mash2. The day 40 SCNT cotyledons had the fewest number of TGC compared to IVF and AI controls. Thus, expression of genes critical to normal placental development is altered in SCNT bovine embryos, and this is expected to cause abnormal trophoblast differentiation and contribute to pregnancy loss.

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Yanni Jia, Rui Cai, Tong Yu, Ruixue Zhang, Shouqin Liu, XinYan Guo, Chunmei Shang, Aihua Wang, Yaping Jin and Pengfei Lin

Decidualization is a critical process for successful embryo implantation and subsequent placenta formation. The characterization and physiological function of lncRNA during decidualization remain largely unknown. In the present study, we conducted RNA-sequencing analysis to compare gene expression between decidua of days 6 and 8, and normal pregnant endometrium (day 4). A total of 2332 high-confidence putative lncRNA transcripts were expressed. Functional clustering analysis of cis and trans lncRNA targets showed that differentially expressed lncRNAs may regulate multiple gene ontology terms and pathways that have important functions in decidualization. Subsequent analyses using qRT-PCR validated that eight of all lncRNAs were differentially regulated in mice uteri during decidualization, both in vivo and in vitro. Furthermore, we showed that differentially expressed lncRNA of Hand2os1 was specifically detected in stromal cells on days 2 to 5 of pregnancy and was strongly upregulated in decidual cells on days 6–8 of pregnancy. Similarly, Hand2os1 expression was also strongly expressed in decidualized cells following artificial decidualization, both in vivo and in vitro. In uterine stromal cells, P4 was able to significantly upregulate the expression of Hand2os1, but upregulation was impeded by RU486, whereas E2 appeared to have no regulating effect on Hand2os1 expression. Concurrently, Hand2os1 significantly promoted the decidual process in vitro and dramatically increased decidualization markers Prl8a2 and Prl3c1. Our results provide a valuable catalog for better understanding of the functional roles of lncRNAs in pregnant mouse uteri, as it relates to decidualization.

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O. J. Rottmann and W. W. Lampeter

Summary. Criteria for assessing embryo vitality of denuded rabbit and mouse embryos in vitro were: volume of the embryo, number of cells and number of metaphase plates after 24 and 48 h in culture. Mouse embryos grew normally, with and without the zona pellucida, but denuded rabbit embryos showed reduced growth (volume and cell number) and failure to implant in synchronized recipients.