Regulation of cellular adhesion molecule expression in murine oocytes, peri-implantation and post-implantation embryos

Chemical modification of hyaluronic acid improves its supportive action on embryo implantation

Hyaluronic acid (HA) is a supplement of the embryo transfer medium that improves embryo implantation. We have suggested that the supportive action of HA can be promoted by introducing additional artificial binding sites on the HA structure. HA was modified at carboxyl sites separately with thiol (SH) and N-hydroxysuccinimide (NHS), as mucoadhesive and amine-reactive groups, respectively. The mouse blastocysts were incubated with HA derivatives for 15 min. The HA coatings maintained their potential for enzymatic degradation and showed no detrimental effect on embryonic viability and developmental potential. After in vivo transfer, a significantly higher implantation rate was attained by HA-NHS treatment (80 %) compared with the HA-SH (53 %) and the commercial transfer medium, EmbryoGlue® (56 %). The HA-NHS was produced by a slight modification on the native structure of HA using a simple, fast, non-expensive and scalable chemistry which all promise applicability of this new HA derivative in assisted reproductive technologies.

Molecules and Prostaglandins Related to Embryo Tolerance

It is generally understood that the entry of semen into the female reproductive tract provokes molecular and cellular changes facilitating conception and pregnancy. We show a broader picture of the participation of prostaglandins in the fertilization, implantation and maintenance of the embryo. A large number of cells and molecules are related to signaling networks, which regulate tolerance to implantation and maintenance of the embryo and fetus. In this work, many of those cells and molecules are analyzed. We focus on platelets, polymorphonuclear leukocytes, and group 2 innate lymphoid cells involved in embryo tolerance in order to have a wider view of how prostaglandins participate. The combination of platelets and neutrophil extracellular traps (Nets), uterine innate lymphoid cells (uILC), Treg cells, NK cells, and sex hormones have an important function in immunological tolerance. In both animals and humans, the functions of these cells can be regulated by prostaglandins and soluble factors in seminal plasma to achieve an immunological balance, which maintains fetal-maternal tolerance. Prostaglandins, such as PGI2 and PGE2, play an important role in the suppression of the previously mentioned cells. PGI2 inhibits platelet aggregation, in addition to IL-5 and IL-13 expression in ILC2, and PGE2 inhibits some neutrophil functions, such as chemotaxis and migration processes, leukotriene B4 (LTB4) biosynthesis, ROS production, and the formation of extracellular traps, which could help prevent trophoblast injury and fetal loss. The implications are related to fertility in female when seminal fluid is deposited in the vagina or uterus.

Investigating the role of CD44 and hyaluronate in embryo-epithelial interaction using an in vitro model

Implantation failure is an important impediment to increasing success rates in assisted reproductive technologies. Knowledge of the cascade of morphological and molecular events at implantation remains limited. Cell surface CD44 and hyaluronate (HA) have been reported in the uterus, but a role in intercellular interaction at implantation remains to be evaluated. Mouse embryos were co-cultured with human Ishikawa endometrial epithelial monolayers over 2 days. Attachment was tenuous during the first 24 h, after which it became stable, leading to breaching of the monolayer. The effects of enzymatically reducing the density of HA, or introducing a function-blocking antibody to CD44, were monitored during progression from weak to stable embryonic attachment. Hyaluronidase-mediated removal of surface HA from the epithelial cells enhanced the speed of attachment, while a similar treatment of embryos had no effect. The antibody to CD44 caused retardation of initial attachment. These results suggest that CD44-HA binding could be employed by embryos during initial docking, but the persistence of HA in epithelial cells might be detrimental to later stages of implantation by retarding attainment of stable attachment.

Ashwin Gene Expression Profiles in Oocytes, Preimplantation Embryos, and Fetal and Adult Bovine Tissues

Simple Summary

Ashwin is a gene involved in the morphogenesis of the central nervous system and the early embryonic development of Xenopus laevis. The analysis of its phylogeny in silico has shown that its functions are restricted to vertebrates, but we lack additional information regarding its biological importance in higher vertebrates, such as mammals. The present study reveals the wide and variable expression of this gene in different bovine organs and confirms its significant expression during early embryonic development, with a pattern similar to that reported for maternal genes. In addition, specific expression of this gene throughout follicular development and during bovine spermatogenesis is revealed, leading to the proposal of ashwin as a new gene with important biological implications in bovine development and reproduction.

Abstract

The ashwin gene, originally identified in Xenopus laevis, was found to be expressed first in the neural plate and later in the embryonic brain, eyes, and spinal cord. Functional studies of ashwin suggest that it participates in cell survival and anteroposterior patterning. Furthermore, ashwin is expressed zygotically in this species, which suggests that it participates in embryonic development. Nevertheless, the expression of this gene has not been studied in mammals. Thus, the aim of this study was to analyze the ashwin expression pattern in bovine fetal and adult tissues, as well as in three independent samples of immature and mature oocytes, and in two- to four-, and eight-cell embryos, morula, and blastocysts. Spatiotemporal expression was analyzed using real-time polymerase chain reaction (PCR); ashwin mRNA was detected in all tissues analyzed, immature and mature oocytes, and two- to eight-cell embryos. It was down-regulated in morula and blastocysts, suggesting that this expression profile is similar to that of maternal genes. Immunohistochemical localization of the ashwin protein in fetal and adult ovaries and testes reveals that this protein is consistently present during all stages of follicular development and during bovine spermatogenesis. These observations lead us to propose ashwin as an important gene involved in mammalian reproduction.

Hashimoto's thyroiditis impairs embryo implantation by compromising endometrial morphology and receptivity markers in euthyroid mice

BACKGROUND

Although thyroid dysfunction caused by Hashimoto's thyroiditis (HT) is believed to be related to implantation failure due to the underdevelopment of the receptive uterus, it is unknown whether HT itself, even in the euthyroid state, impairs embryo implantation associated with endometrial receptivity defects. To address whether HT itself can affect endometrial receptivity accompanied by implantation alterations, a euthyroid HT model was established in mice.

METHODS

Female NOD mice were immunized twice with thyroglobulin and adjuvant to induce the experimental HT model. Four weeks after the second treatment, the mice were normally mated, and pregnant ones were sacrificed in implantation window for thyroid-related parameter and steroid hormones measurements by electrochemiluminescence immunoassay and enzyme-linked immunosorbent assay and implantation site number calculation by uptake of Chicago Blue dye. In addition, certain morphological features of endometrial receptivity were observed by hematoxylin-eosin staining and scanning electron microscopy, and the expression of other receptivity markers were analyzed by immunohistochemistry, RT-qPCR or Western Blot.

RESULTS

HT mice displayed intrathyroidal monocyte infiltration and elevated serum thyroid autoantibody levels without thyroid dysfunction, defined as euthyroid HT in humans. Euthyroid HT resulted in implantation failure, fewer pinopodes, retarded pinopode maturation, and inhibited expression of receptivity markers: estrogen receptor α (ERα), integrin β3, leukemia inhibitory factor (LIF), and cell adhesion molecule-1 (ICAM-1). Interestingly, despite this compromised endometrial receptivity response, no statistical differences in serum estradiol or progesterone level between groups were found.

CONCLUSIONS

These findings are the first to indicate that HT induces a nonreceptive endometrial milieu in the euthyroid state, which may underlie the detrimental effects of HT itself on embryo implantation.

Link between neurodegeneration and trabecular meshwork injury in glaucomatous patients

Background

Glaucoma is classified as a neurodegenerative disease. However, the biomarkers of neurodegeneration in the aqueous humour of primary open angle glaucoma (POAG) eyes have not been quantitatively examined yet. In this study, levels of neurodegeneration-related cytokines in the aqueous humour of POAG eyes were measured and compared with those of non-glaucoma (senile cataract) control eyes.

Methods

This cross-sectional study included 24 patients (24 eyes) with POAG and 22 patients (22 eyes) with cataract. Aqueous humour samples were collected before the commencement of phacoemulsification surgery. The concentrations of brain-derived neurotrophic factor (BDNF), cathepsin D, myeloperoxidase (MPO), soluble intercellular adhesion molecule-1 (sICAM-1), soluble neural cell adhesion molecule (sNCAM), soluble vascular cell adhesion molecule-1 (sVCAM-1), and plasminogen activator inhibitor-1 (PAI-1) were measured using the Luminex suspension array technique. The clinical characteristics of the patients were also obtained for correlation analysis.

Results

Compared with the cataract group, the levels of cathepsin D (P < 0.001), sNCAM (P < 0.001) and sVCAM-1 (P = 0.007) were significantly higher in the aqueous humour samples from POAG. The levels of BDNF, sICAM-1, MPO and PAI-1 did not differ among the groups. Mean deviation (MD) values measured by the Humphrey Visual Field Analyzer were significantly associated with levels of cathepsin D (P < 0.001; ρ= − 0.668), sICAM-1 (P = 0.003; ρ= − 0.579), sVCAM-1(P < 0.001; ρ= − 0.695), and PAI-1 (P = 0.007; ρ= − 0.533). The cytokines showed a positive correlation among each other (P < 0.0083).

Conclusion

These data suggest that POAG patients had elevated levels of multiple biomarkers of neurodegeneration in the aqueous humour, and these elevated biomarkers may be related to trabecular meshwork injury.

Trial registration

This study was registered in the Chinese Clinical Trial Registry (ChiCTR-OOC-16008516) on May 22, 2016.

Biochemical alterations in the oocyte in support of early embryonic development

Notwithstanding the enormous reproductive potential encapsulated within a mature mammalian oocyte, these cells present only a limited window for fertilization before defaulting to an apoptotic cascade known as post-ovulatory oocyte aging. The only cell with the capacity to rescue this potential is the fertilizing spermatozoon. Indeed, the union of these cells sets in train a remarkable series of events that endows the oocyte with the capacity to divide and differentiate into the trillions of cells that comprise a new individual. Traditional paradigms hold that, beyond the initial stimulation of fluctuating calcium (Ca2+) required for oocyte activation, the fertilizing spermatozoon plays limited additional roles in the early embryo. While this model has now been drawn into question in view of the recent discovery that spermatozoa deliver developmentally important classes of small noncoding RNAs and other epigenetic modulators to oocytes during fertilization, it is nevertheless apparent that the primary responsibility for oocyte activation rests with a modest store of maternally derived proteins and mRNA accumulated during oogenesis. It is, therefore, not surprising that widespread post-translational modifications, in particular phosphorylation, hold a central role in endowing these proteins with sufficient functional diversity to initiate embryonic development. Indeed, proteins targeted for such modifications have been linked to oocyte activation, recruitment of maternal mRNAs, DNA repair and resumption of the cell cycle. This review, therefore, seeks to explore the intimate relationship between Ca2+ release and the suite of molecular modifications that sweep through the oocyte to ensure the successful union of the parental germlines and ensure embryogenic fidelity.

MFGE8 regulates TGF-β-induced epithelial mesenchymal transition in endometrial epithelial cells in vitro

This study investigated the role of milk fat globule-epidermal growth factor-factor 8 (MFGE8) in TGF-β-induced epithelial-mesenchymal transition (EMT) of endometrial epithelial cells. These were in vitro studies using human endometrial epithelial cells and mouse blastocysts. We investigated the ability of TGF-β to induce EMT in endometrial epithelial cells (HEC-1A) by assessment of cytological phenotype (by light and atomic force microscopy), changes in expression of the markers of cell adhesion/differentiation E- and N-cadherin, and of the transcription factor Snail (by immunofluorescence and immunoblotting), and competence to support embryo attachment in a mouse blastocyst outgrowth assay. We also studied the effects of E-cadherin expression in cells transfected by retroviral shRNA vectors specifically silencing MFGE8. Results demonstrated that TGF-β induced EMT as demonstrated by phenotypic cell changes, by a switch of cadherin expression as well as by upregulation of the expression of the mesenchymal markers Snail and Vimentin. Upon MFGE8 knockdown, these processes were interfered with, suggesting that MFGE8 and TGF-β together may participate in regulation of EMT. This study demonstrated for the first time that endometrial MFGE8 modulates TGF-β-induced EMT in human endometrium cells.

EpCAM is decreased but is still present in uterine epithelial cells during early pregnancy in the rat: potential mechanism for maintenance of mucosal integrity during implantation

The non-receptive uterine luminal epithelium forms a polarised epithelial barrier, protective against potential pathogenic assault from the external environment and invasion by the blastocyst. However, during the window of implantation, the uterine luminal epithelial cells (UECs) transition to a receptive state by dismantling many of their intercellular and cell-matrix adhesions in preparation for epithelial detachment and subsequent blastocyst implantation. The present study investigated the presence and regulation of the intercellular adhesion protein, Epithelial Cell Adhesion Molecule (EpCAM) during early pregnancy in the rat to understand its role in the transition to receptivity. Immunofluorescence and western blotting analysis were used to study EpCAM expression in normal pregnancy, hormone replacement studies and pseudopregnancy. EpCAM was abundantly expressed and localised to the uterine luminal and glandular epithelium during the non-receptive state but decreased to lower but still observable levels around the time of implantation. This decrease was not dependent on ovarian hormones or the blastocyst. Further, EpCAM colocalised with but did not associate with its frequent binding partner, Tumour necrosis factor α (TNFα)-converting enzyme, also known as A Disintegrin And Metalloprotease 17 (TACE/ADAM17), at the time of fertilisation. These results suggest that, prior to implantation, EpCAM mediates intercellular adhesion in the uterine epithelium, but that, during implantation when UECs lose the majority of their intercellular and cell-matrix adhesions, EpCAM levels are decreased but still present for the maintenance of mucosal integrity.

Junctional adhesion molecule 2 mediates the interaction between hatched blastocyst and luminal epithelium: induction by progesterone and LIF

Background

Junctional adhesion molecule 2 (Jam2) is a member of the JAM superfamily. JAMs are localized at intercellular contacts and participated in the assembly and maintenance of junctions, and control of cell permeability. Because Jam2 is highly expressed in the luminal epithelium on day 4 of pregnancy, this study was to determine whether Jam2 plays a role in uterine receptivity and blastocyst attachment in mouse uterus.

Methodology/Principal Findings

Jam2 is highly expressed in the uterine luminal epithelium on days 3 and 4 of pregnancy. Progesterone induces Jam2 expression in ovariectomized mice, which is blocked by progesterone antagonist RU486. Jam2 expression on day 4 of pregnancy is also inhibited by RU486 treatment. Leukemia inhibitory factor (LIF) up-regulates Jam2 protein in isolated luminal epithelium from day 4 uterus, which is blocked by S3I-201, a cell-permeable inhibitor for Stat3 phosphorylation. Under adhesion assay, recombinant Jam2 protein increases the rate of blastocyst adhesion. Both soluble recombinant Jam2 and Jam3 can reverse this process.

Conclusion

Jam2 is highly expressed in the luminal epithelium of receptive uterus and up-regulated by progesterone and LIF via tyrosine phosphorylation of Stat3. Jam2 may play a role in the interaction between hatched blastocyst and receptive uterus.

Glycosaminoglycans improves early development of zona-free 8-cell rat embryos to blastocysts in a chemically defined medium, but not the pregnancy rate following transfer of the blastocysts

The objective of the present study was to clarify the possible role of the zona pellucida (ZP) in early development of rat embryos and to determine the effect of glycosaminoglycans on the development of ZP-free 8-cell embryos before or after embryo transfer at the blastocyst stage. Eight-cell embryos were divided into three groups comprised of, 1) intact controls, 2) embryos with the ZP was removed with acidic solution and 3) pairs of ZP-free 8-cell embryos aggregated in a small hollow. These embryos were cultured in a chemically defined mR1ECM for 24 h. Developmental ability to the blastocyst stage and mean cell number in the blastocyst was lower in ZP-free embryos than in intact controls. When these blastocysts were transferred, the farrowing rate and efficiency of embryos developed to term were also lower in ZP-free embryos, but not in the aggregated ones. Supplementation with hyaluronan (HA; 63-250 µg/ml) or heparan sulfate proteoglycan (HS; 15 µg/ml) significantly improved blastocyst formation of ZP-free embryos and the cell number in the blastocyst by reducing the incidence of apoptosis. However, there were no beneficial effects of HA or HS on farrowing and newborn rates after transfer of the blastocysts. In conclusion, the ZP plays roles in maintaining successful development of early rat embryos at least from the 8-cell stage not only to the blastocyst stage but also to posttransfer stages. Glycosaminoglycans, such as HA or HS, appear to contribute to successful cleavage during early development to the blastocyst stage but may be insufficient to maintain the posttransfer survival of ZP-free embryos.

The effect of glycosaminoglycans on rat gametes in vitro and the associated signal pathway

The effects of adding the extracellular glycosaminoglycans (GAGs), hyaluronic acid (HA) and chondroitin sulphate (CS) to ratin vitrofertilisation (IVF) media were assessed. Metaphase II (MII) oocytes were also incubated in GAG-supplemented modified rat 1-cell embryo culture medium (mR1ECM+BSA) for 3 days. Cytoplasmic fragmentation was significantly reduced in mR1ECM+BSA with HA (39.0–48.0%) compared with the control (82.0%). In IVF experiments, neither HA (8.0–30.8%) nor CS (9.7–42.5%) improved fertilisation rates compared with controls fertilised in M16 (47.2%) or enriched Krebs–Ringer bicarbonate solution (61.5%). RT-PCR and Western blot were used to probe for CD44 mRNA and protein in Sprague–Dawley gametes and cumulus cells. CD44 was identified in cumulus cells, suggesting a role for oocyte maturation and cumulus expansion. The CD44 protein was also present on caudal epididymal spermatozoa that were highly stimulated by CSin vitroimplicating a role in fertilisation for CS and CD44.

Mitochondrial activity, distribution and segregation in bovine oocytes and in embryos produced in vitro

Contents Bovine oocytes and embryos produced in vitro were studied to determine the mitochondrial pattern of distribution, segregation and activity using DIOC 6 and Jc-1 fluorescence. The highest fluorescence level observed in mature oocytes was taken as 100% activity and six activity levels were estimated as follows: (1) 0%, (2) 1-15%, (3) 16-30%, (4) 31-50%, (5) 51-75% and (6) 76-100%. Three patterns of mitochondrial distribution were found: (1) diffused throughout the cytoplasm in oocytes and embryos, (2) pericytoplasmic in oocytes and embryos, and (3) perinuclear only in embryos. The segregation of mitochondria in blastomeres showed two distinct patterns: (1) symmetrical with an even mitochondrial population, and (2) asymmetrical with different numbers of mitochondria in each blastomere. In immature oocytes, mitochondrial activity was very low and the distribution was diffuse or negligible, while in mature oocytes the activity was high and the distribution was diffuse or pericytoplasmic. Competent embryos up to the 16-cell stage showed intermediate levels of activity (16-50%) but activity decreased thereafter up to the blastocyst stage. Non-competent embryos showed low levels of activity (1-15%) at all stages. These results suggest that mitochondria might play an important role during early development and that a minimum threshold of activity regulates the potential competence for reaching the blastocyst stage.