The zona pellucida in folliculogenesis, fertilization and early development

Effects of indented zona pellucida on oocyte growth and development explored from changes of gene expression in cumulus cells

PURPOSE

Abnormal Zona Pellucida (ZP) of human oocytes is an extracellular oocyte abnormality leading to subfertility or infertility, among which indented ZP (iZP) is a common clinical case, and there is currently no effective clinical solution. The study aimed to find out the influence of this abnormal ZP on the growth and development of GC and further explore its influence on the growth and development of oocytes, hoping to provide new ideas for the etiology and treatment of such patients.

METHODS

In this study, we collected granulosa cells GC from oocytes with iZP(four cases) and GC from oocytes with a normal appearance of the ZP(eight cases) during ICSI treatment cycles, and submitted them to transcriptomic analysis using next-generation RNA sequencing (RNAseq).

RESULTS

177 Differentially Expressed Genes (DEG) were identified by RNAseq analysis of Granulosa Cells (GC) from oocytes with a normal ZP morphological appearance and those with iZP. Correlation analysis of these DEGs showed that the expression levels of the immune factor CD274 and the inflammatory factors IL4R and IL-7R, which are positively associated with ovulation, were significantly down-regulated in the GC of oocytes with iZP. Hippo, PI3K-AKT, Ras and calcium signaling pathways related to oocyte growth and development, NTRK2 and its ligands (BDNF and NT5E) from the neurotrophin family that are trophic to the oocyte were also significantly down-regulated in the GC of oocytes with iZP. In addition, the expression of cadherin family members CDH6, CDH12 and CDH19 were significantly down-regulated in DEGs, and the down-regulation of these proteins may affect the gap junction between Granulosa cells and oocytes.

CONCLUSION

IZP might cause obstacles to dialogue and material exchange between GC and oocytes and further affect the growth and development of oocytes.

In silico identification and characterization of the SNPs in the human ASTL gene and their probable role in female infertility

Ovastacin (ASTL), a zinc metalloprotease, is released from a fertilized egg during exocytosis of cortical granules which occurs minutes after the sperm and egg fuse. ASTL cleaves ZP2, one of the four primary glycoproteins of human zona pellucida, and this cleavage prevents polyspermy, causes zona pellucida hardening, and also protects the pre-implantation embryo. Any perturbation in the activity of ASTL can thus disturb this process and may lead to infertility without changing the gross morphology of the oocyte. A small amount of ASTL is also released by unfertilized oocytes but its catalytic activity is absent as it is bound by its inhibitor, Fetuin-B (FETUB). Pre-mature release of ASTL when FETUB is absent also causes infertility. To identify and understand the structural and functional effects of deleterious SNPs of ASTL on its interaction with ZP2 and FETUB and hence on fertility, a total of 4,748 SNPs from the dbSNP database were evaluated using a variety of in silico tools. All of the 40 shortlisted nsSNPs were present in the catalytic domain of the protein. Comparison of the wild type with mutants using MutPred2 suggests an alteration in the catalytic activity/zinc binding site in many SNPs. Docking studies show the involvement of hydrophobic interactions and H bonding between ASTL and ZP2 and also between ASTL and FETUB. Four positions in ASTL involved in the hydrophobic interactions (P¹⁰⁵ and D²⁰⁰ between ASTL and ZP2; D¹⁹⁸ and L²⁷⁸ between ASTL and FETUB) and 5 in H bonding (E⁷⁵ and R¹⁵⁹ between ASTL and ZP2; and K⁹³, R^159, and C²⁸¹ between ASTL and FETUB) have SNP's associated with them validating their importance. Interestingly, a cluster of multiple SNPs was found in the motif ¹⁹⁸DRD²⁰⁰, which is also a well-conserved region among several species. Statistical Coupling Analysis (SCA) suggested that the deleterious SNPs were present in the functionally important amino acid positions of ASTL and are evolutionarily coupled. Thus, these results attempt to identify the regions in ASTL, mutations in which can affect its binding with ZP2 or FETUB and cause female infertility.

An Alternative Way to Improve Mammalian Embryo Development In Vitro: Culture of Zona Pellucida-Free Embryos

An increasing number of data proves that the presence of the zona pellucida is not essential to mammalian embryo production, including maturation, fertilization, and embryo culture. In fact, the structure of the zona pellucida of in vitro-produced embryos differs significantly from its in vivo counterpart, influencing metabolism and requiring disproportionate efforts to crack open at the time of hatching. This review aims to focus attention on this field and stimulate research in zona-free embryo culture. In domestic animals, extensive application of purpose-designed culture systems for zona-free embryos proved the feasibility of this approach. It may open new possibilities and increase efficiency in both transgenic research and human-assisted reproduction.

Identification and in silico Characterization of Deleterious Single Nucleotide Variations in Human ZP2 Gene

ZP2, an important component of the zona matrix, surrounds mammalian oocytes and facilitates fertilization. Recently, some studies have documented the association of mutations in genes encoding the zona matrix with the infertile status of human females. Single nucleotide polymorphisms are the most common type of genetic variations observed in a population and as per the dbSNP database, around 5,152 SNPs are reported to exist in the human ZP2 (hZP2) gene. Although a wide range of computational tools are publicly available, yet no computational studies have been done to date to identify and analyze structural and functional effects of deleterious SNPs on hZP2. In this study, we conducted a comprehensive in silico analysis of all the SNPs found in hZP2. Six different computational tools including SIFT and PolyPhen-2 predicted 18 common nsSNPs as deleterious of which 12 were predicted to most likely affect the structure/functional properties. These were either present in the N-term region crucial for sperm-zona interaction or in the zona domain. 31 additional SNPs in both coding and non-coding regions were also identified. Interestingly, some of these SNPs have been found to be present in infertile females in some recent studies.

The effects of gallic acid and metformin on male reproductive dysfunction in diabetic mice induced by methylglyoxal: An experimental study

BACKGROUND

Diabetes mellitus is a disease that has reached a dangerous point. Today, nearly 500 million men and women around the world live with diabetes. Gallic acid (Gal) affects diabetes.

OBJECTIVE

To evaluate the effects of Gal and metformin (met) on the levels of glucose, insulin, testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), sperm count, antioxidant status, and histological changes in the testes of diabetic mice induced by methylglyoxal (MGO).

MATERIALS AND METHODS

In this experimental study, 50 male adult NMRI mice, weighting 25-30 gr, aged 3-4 months were randomly divided into five equal groups (n = 10/each). (i) Control (vehicle, normal saline), (ii) MGO (600 mg/kg/d) orally for 28 days, (iii) Gal (50 mg/kg/d), (iv) MGO+Gal, and (v) MGO+met (200 mg/kg/d). Gal and met were administered orally for 21 consecutive days after the induction of diabetes. Blood samples were taken at 24 hr after the latest doses of treatment. Histological assessment of the testis was done, and the epididymis sperm count was obtained. Antioxidant indices, glucose, insulin, LH, FSH, and testosterone levels were measured.

RESULTS

In the MGO group compared to the control group, insulin, glucose (p = 0.001), LH (p = 0.04) and malondialdehyde (p = 0.001) were increased. However, the level of testosterone (p = 0.001), seminiferous tubule diameters, epithelial height, sperm count, superoxide dismutase activity (p = 0.02), and testis volume (p = 0.01) were decreased. The results indicated that Gal and met ameliorated the MGO effects.

CONCLUSION

These findings suggested that the animals receiving MGO became diabetic. According to the results, Gal and met can effectively prevent MGO-induced diabetes. The effect of Gal was equivalent and sometimes better than metformin.

Does combination of estradiol and sesame oil improve the oocyte quality, embryo development and expressions of Zp3, E-cad, and Ctnnb1 genes in mice? An experimental study

BACKGROUND

Aging may reduce oocyte maturation, embryo quality, and fertility potential.

OBJECTIVE

To compare the effect of estradiol (E2) and sesame oil on oocyte and embryo quality between young and old mice.

MATERIALS AND METHODS

Sixty old and young female mice were divided in to two groups (30 mice/group, grouped by age). Each group was divided into three subgroups of mice treated with sesame oil, E2 + sesame oil, and normal saline as control group. After ovulation induction, some oocytes were considered for in vitro fertilization and the rest were assessed for morphological status. After obtaining the two-cell embryos, the embryos were collected to determine the expression of zona pellucida (ZP) glycoprotein 3, E-cadherin, and β-catenin genes and some of them followed until the blastocysts stage to evaluate the viability.

RESULTS

The findings showed that the mean ZP and perivitelline space thickness increased in the old mice that received the E2 + sesame oil treatment. The number of 2-cell embryos, blastocysts, and live cells were significantly higher in the old group treated with sesame oil respectively (p = 0.018, 0.002, and < 0.0001, respectively). The normal ZP shape and refractile body numbers increased in the old mice that were treated with sesame oil, respectively. The E-cadherin gene was downregulated in the treatment groups compared to the controls.

CONCLUSION

Sesame oil showed a better response in the old mice, because aging is associated with an increased rate of reactive oxygen species, causing deficiencies in both oocyte and embryo qualities.

Electroporation of Mouse Follicles, Oocytes and Embryos without Manipulating Zona Pellucida

Electroporation is an effective technique of transfection, but its efficiency depends on the optimization of various parameters. In this study, a simplified and efficient method of gene manipulation was standardized through electroporation to introduce a recombinant green fluorescent protein (GFP) construct as well as RNA-inhibitors in intact mouse follicles, oocytes and early embryos, where various electroporation parameters like voltage, pulse number and pulse duration were standardized. Electroporated preantral follicles were cultured further in vitro to obtain mature oocytes and their viability was confirmed through the localization of a known oocyte maturation marker, ovastacin, which appeared to be similar to the in vivo-derived mature oocytes and thus proved the viability of the in vitro matured oocytes after electroporation. Standardized electroporation parameters, i.e., three pulses of 30 V for 1 millisecond at an interval of 10 s, were applied to manipulate the expression of mmu-miR-26a in preantral follicles through the electroporation of miR inhibitors and mimics. The TUNEL apoptosis assay confirmed the normal development of the electroporated embryos when compared to the normal embryos. Conclusively, for the first time, this study demonstrated the delivery of exogenous oligonucleotides into intact mouse follicles, oocytes and embryos without hampering their zona pellucida (ZP) and further development.

ALADDIN study: does assisted hatching of vitrified/warmed blastocysts improve live birth rate? Protocol for a multicentric randomised controlled trial

INTRODUCTION

Recent data suggest a higher clinical pregnancy rate performing assisted hatching (AH) on previously cryopreserved embryos but fail to demonstrate significant effects on live birth rate. However, current evidence is based on studies with a small sample size and may hide a type II error. Moreover, poor attention has been given to the specific effect of AH on frozen/thawed blastocysts. To shed light on this topic, we developed the present protocol for a randomised trial to investigate the benefits of the laser-mediated partial removal of the zona pellucida in vitrified/warmed blastocysts.

METHODS AND ANALYSIS

The pArtiaL zonA pelluciDa removal by assisteD hatchINg of blastocysts (ALADDIN) study is a multicentric prospective comparative study with a parallel randomised controlled design aiming to investigate whether AH performed on warmed blastocysts before embryo transfer can improve live birth rate. Women allocated to the control group will undergo embryo transfer of blastocysts not previously subjected to AH. Two infertility units will be involved in the study. Enrolment of patients will last 18 months with quarterly monitoring and the entire study is foreseen to be closed in 36 months. Secondary outcomes include: proportion of transferred blastocysts/thawed blastocyst, morphological features of blastocysts before embryo transfer, implantation, biochemical pregnancy, clinical pregnancy (ultrasound visible gestational sac), miscarriage, multiple pregnancy, preterm birth (<37 weeks of gestation), obstetrical and neonatal complications and congenital anomaly rates.

ETHICS AND DISSEMINATION

This protocol received a favourable ethical opinion from the Ethical Committee of IRCCS San Raffaele Scientific Institute and the Ethical Committee Area 2 Milan. Each participant will provide written consent to participate and remain encoded during the study. The trial results will be published in peer-reviewed journals and presented at conferences.

TRIAL REGISTRATION NUMBER

NCT03623659; Pre-results.

Roles for Golgi Glycans in Oogenesis and Spermatogenesis

Glycosylation of proteins by N- and O-glycans or glycosaminoglycans (GAGs) mostly begins in the endoplasmic reticulum and is further orchestrated in the Golgi compartment via the action of >100 glycosyltransferases that reside in this complex organelle. The synthesis of glycolipids occurs in the Golgi, also by resident glycosyltransferases. A defect in the glycosylation machinery may impair the functions of glycoproteins and other glycosylated molecules, and lead to a congenital disorder of glycosylation (CDG). Spermatogenesis in the male and oogenesis in the female are tightly regulated differentiation events leading to the production of functional gametes. Insights into roles for glycans in gamete production have been obtained from mutant mice following deletion or inactivation of genes that encode a glycosylation activity. In this review, we will summarize the effects of altering the synthesis of N-glycans, O-glycans, proteoglycans, glycophosphatidylinositol (GPI) anchored proteins, and glycolipids during gametogenesis in the mouse. Glycosylation genes whose deletion causes embryonic lethality have been investigated following conditional deletion using various Cre recombinase transgenes with a cell-type specific promoter. The potential effects of mutations in corresponding glycosylation genes of humans will be discussed in relation to consequences to fertility and potential for use in contraception.

The Effect of Assisted Hatching on Live Birth Rate Following Fresh Embryo Transfer in Advanced Maternal Age

OBJECTIVE

Assisted hatching (AH) was introduced 3 decades ago as an adjunct method to in vitro fertilization (IVF) and embryo transfer (ET) to improve embryo implantation rate. Limited data are available on the effect of AH on live birth rate (LBR) in advanced maternal age. The objective of this study is to investigate the effect of AH on LBR in women aged 40 years and older.

MATERIALS AND METHODS

A retrospective study conducted at a single academic reproductive center. Women aged ≥40 years, who were undergoing their first IVF cycle were included. Laser-assisted hatching was the method used for AH and single or double embryos were transferred. Embryo transfer was performed at the cleavage or blastocyst stage. Separate analysis was performed on each ET stage. Live birth rate was the primary outcome.

RESULTS

A total of 892 patients were included. Of these, 681 women underwent cleavage ET and 211 underwent blastocyst ET. The clinical pregnancy rate in the entire group was 15.3% and the LBR was 10.2%. Baseline and cycle parameters between the AH group and the control group were comparable. Assisted hatching in the cleavage stage was associated with lower clinical pregnancy rate (odds ratio [OR], 0.52; confidence interval [CI], 0.31-0.86; P = .012) and lower LBR (OR, 0.36; CI, 0.19-0.68; P = .001). Assisted hatching did not have any effect on outcomes in blastocyst ET.

CONCLUSION

Assisted hatching does not improve the reproductive outcomes in advanced maternal age. Performing routine AH for the sole indication of advanced maternal age is not clinically justified.

CAR expression in human embryos and hESC illustrates its role in pluripotency and tight junctions

Coxsackie virus and adenovirus receptor, CXADR (CAR), is present during embryogenesis and is involved in tissue regeneration, cancer and intercellular adhesion. We investigated the expression of CAR in human preimplantation embryos and embryonic stem cells (hESC) to identify its role in early embryogenesis and differentiation. CAR protein was ubiquitously present during preimplantation development. It was localised in the nucleus of uncommitted cells, from the cleavage stage up to the precursor epiblast, and corresponded with the presence of soluble CXADR3/7 splice variant. CAR was displayed on the membrane, involving in the formation of tight junction at compaction and blastocyst stages in both outer and inner cells, and CAR corresponded with the full-length CAR-containing transmembrane domain. In trophectodermal cells of hatched blastocysts, CAR was reduced in the membrane and concentrated in the nucleus, which correlated with the switch in RNA expression to the CXADR4/7 and CXADR2/7 splice variants. The cells in the outer layer of hESC colonies contained CAR on the membrane and all the cells of the colony had CAR in the nucleus, corresponding with the transmembrane CXADR and CXADR4/7. Upon differentiation of hESC into cells representing the three germ layers and trophoblast lineage, the expression of CXADR was downregulated. We concluded that CXADR is differentially expressed during human preimplantation development. We described various CAR expressions: i) soluble CXADR marking undifferentiated blastomeres; ii) transmembrane CAR related with epithelial-like cell types, such as the trophectoderm (TE) and the outer layer of hESC colonies; and iii) soluble CAR present in TE nuclei after hatching. The functions of these distinct forms remain to be elucidated.

Molecular aspects of implantation failure

Despite expanding global experience with advanced reproductive technologies, the majority of IVF attempts do not result in a successful pregnancy, foremost as a result of implantation failure. The process of embryo implantation, a remarkably dynamic and precisely controlled molecular and cellular event, appears inefficient in humans and is poorly understood. However, insights gained from clinical implantation failure, early pregnancy loss, and emerging techologies that enable molecular interrogation of endometrial-embryo interactions are unravelling this major limiting step in human reproduction. We review current molecular concepts thought to underlie implantation failure, consider the contribution of embryonic and endometrial factors, and discuss the clinical value of putative markers of impaired endometrial receptivity. Finally we highlight the nature of the dialogue between the maternal endometrium and the implanting embryo and discuss the concept of natural embryo selection. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Bone morphogenetic protein signaling transcription factor (SMAD) function in granulosa cells

The transforming growth factor β (TGFβ) family of proteins are key regulators of growth and differentiation. Members of this family, including multiple TGFβs, activins, bone morphogenetic proteins (BMPs), and growth and differentiation factor 9 (GDF9), are expressed from oocytes or their associated follicular somatic cells (granulosa and thecal cells) with cell-type and stage-dependent specificity. Granulosa cells are the target cells for many of these ligands. Granulosa cell-specific knockout mice for all of the receptor-regulated SMADs, as well as the common regulatory SMAD4, have recently been generated and highlight the importance of this family in most stages of folliculogenesis. These models have also uncovered a novel role for the BMPs in suppression of granulosa cell tumor development and metastasis. This review summarizes the phenotypes of these mouse models and their contribution to our understanding of the complexity of BMP function during follicle development.

Is there a role for immunocontraception?

The world's population is continuing to grow at an alarming rate and yet no novel methods of contraception have been introduced since 1960s. The paucity of our current contraceptive armoury is indicated by the 46 million abortions that are performed each year, largely in developing countries where population growth is greatest. Thus, whatever new forms of fertility control we develop for the next millennium, the particular needs of developing countries should be borne in mind. Contraceptive vaccines have the potential to provide safe, effective, prolonged, reversible protection against pregnancy in a form that can be easily administered in the Third World. In this review we consider the contraceptive targets that might be pursued, how vaccines might be engineered and the problems generated by inter-individual variations in antibody titre. We conclude that the specifications for a safe, effective, reversible vaccine are more likely to be met in animals than man.

High doses of medroxyprogesterone as the cause of disappearance of adherence of the zona pellucida to an oocyte

The zona pellucida (ZP) is an external glycoprotein membrane of oocytes of mammals and embryos in the early stage of their development. ZP first appears in growing ovarian follicles as an extracellular substance between the oocyte and granular cells. The zona pellucid markedly affects the development and maturation of the oocyte. The morphology of the ZP-oocyte complex allows a more precise determination of the oocyte maturity. According to numerous experimental studies, ZP is essential for preimplantation embryonic development of humans and other mammals. It prevents dispersion of blastomeres and enhances their mutual interactions. ZP is a dynamic structure responsible for the provision of nutrients to early forms of oocytes in mammals. The aim of the present study was untrastructural evaluation of the ZP-oocyte contact during inhibited ovulation. Female white rats (Wistar strain) received a suspension of medroxyprogesterone acetate (MPA) in incremental intramuscular bolus doses of 3.7 mg (therapeutic dose), 7.4 mg and 11.1 mg. The animals were decapitated 5 days after the administration of MPA. Ovarian sections were evaluated under a transmission electron microscope (TEM) Zeiss EM 900. Morphometric analysis of ZP was conducted using the cell imaging system by Olympus. In females exposed to therapeutic doses of MPA, ZP showed the structure of granular-fibrous reticulum of a medium electron density with single cytoplasmic processes originating from the surrounding structures. The oocyte cell membrane generated single, delicate processes directed toward ZP. Microvilli of the oocyte were short and thin. In the group receiving 7.4 mg of MPA, ZP had the structure of a delicate, loose granular-fibrous reticulum, and the oocyte cell membrane generated single microvilli directed toward ZP. In both those groups, the close ZP-oocyte contact was observed. Otherwise, in the group exposed to the highest MPA doses (11.1 mg), thicker and more numerous oocyte microvilli were found, which did not penetrate ZP matrix. They were dense, irregularly separated contour, forming a barrier between ZP and oocyte. The present findings are likely to suggest that MPA has inhibiting effects on the synthesis of binding proteins and causes the loss of the oocyte contact with ZP.

Estimating Young's modulus of zona pellucida by micropipette aspiration in combination with theoretical models of ovum

The zona pellucida (ZP) is the spherical layer that surrounds the mammalian oocyte. The physical hardness of this layer plays a crucial role in fertilization and is largely unknown because of the lack of appropriate measuring and modelling methods. The aim of this study is to measure the biomechanical properties of the ZP of human/mouse ovum and to test the hypothesis that Young's modulus of the ZP varies with fertilization. Young's moduli of ZP are determined before and after fertilization by using the micropipette aspiration technique, coupled with theoretical models of the oocyte as an elastic incompressible half-space (half-space model), an elastic compressible bilayer (layered model) or an elastic compressible shell (shell model). Comparison of the models shows that incorporation of the layered geometry of the ovum and the compressibility of the ZP in the layered and shell models may provide a means of more accurately characterizing ZP elasticity. Evaluation of results shows that although the results of the models are different, all confirm that the hardening of ZP will increase following fertilization. As can be seen, different choices of models and experimental parameters can affect the interpretation of experimental data and lead to differing mechanical properties.

Antibodies to two ZP3 B cell epitopes affect zona pellucida assembly

Mouse zona pellucida (ZP) proteins are synthesized in developing oocytes and assembled into ZP after their secretion. This study has investigated whether anti-ZP3 antibodies affect ZP assembly. Peptides CP2 and CP3 were used to elicit antibodies to two ZP3 B cell epitopes, ZP3 (335-342) and ZP3 (171-180). Ovulated eggs from mice immunized with a mixture of CP2/CP3 showed an abnormal ZP; importantly, the ZP completely dissolved both in vitro and in vivo 12h after ovulation. Although CP3 immunization resulted also in abnormal ZP, the ZP did not dissociate. Binding of antibodies to the ZP prior to oocyte maturation was requisite, as in vitro incubation of ovulated eggs in combination with the two antibodies failed to induce ZP dissolution. Electron microscopic observation further demonstrated a significant abnormality in ZP structure in CP2/CP3-immunized mice, especially in mature follicles, suggesting that B cell epitopes may be involved in ZP assembly. Though antibody elicited by CP2 has been shown to inhibit fertilization, we now show that antibody induced by CP3 had no effect on fertility. However, immunization with CP3/CP2 resulted in a significantly lower fertility rate than CP2 alone. This suggests that infertility in these mice may be due to an unstable ZP structure. Our model provides a useful tool to study ZP assembly and its structure beyond molecular biology method.

Oocyte quality and maternal control of development

The oocyte is a unique and highly specialized cell responsible for creating, activating, and controlling the embryonic genome, as well as supporting basic processes such as cellular homeostasis, metabolism, and cell cycle progression in the early embryo. During oogenesis, the oocyte accumulates a myriad of factors to execute these processes. Oogenesis is critically dependent upon correct oocyte-follicle cell interactions. Disruptions in oogenesis through environmental factors and changes in maternal health and physiology can compromise oocyte quality, leading to arrested development, reduced fertility, and epigenetic defects that affect long-term health of the offspring. Our expanding understanding of the molecular determinants of oocyte quality and how these determinants can be disrupted has revealed exciting new insights into the role of oocyte functions in development and evolution.

High inter-individual variation in the gestation length of the hedgehog tenrec, Echinops telfairi (Afrotheria)

The gestation length (GL) of Tenrecs (Tenrecinae, Afrotheria) is still uncertain. This lack of knowledge also applies to the lesser hedgehog tenrec, Echinops telfairi, the species most commonly bred and maintained in captivity. The animals used in this study were held under controlled conditions (light, temperature and humidity). In order to determine the GL, groups of female tenrecs were subjected to various mating procedures followed by isolation periods of different lengths. A total of n=249 pregnancies were analysed and the number of offspring per litter was 3.29+/-0.09. The length of gestation could be determined in n=199 pregnancies and a mean GL of 67.53+/-0.36 days was calculated. Initial attempts with isolation periods of less than 16 days did not allow to accurately define the GL. Experiments with longer isolation periods and females subjected to only one mating procedure (n=10) revealed a variation in the GLs of 57-79 days. However, in one female a GL of only 50 days was also observed indicating an even greater range in GL variation. There was a statistically significant tendency for shorter GLs in the animals that conceived later in the mating season, but no statistical evidence was found that age, parity or litter size played an essential role in determining the GL. In conclusion, an unexpected high variability in gestation length in E. telfairi was demonstrated although the study animals were kept under controlled environmental conditions. The factors and mechanisms regulating this high intra-species variability in gestation length need further investigations.

Inoculation of female American black bears (Ursus americanus) with partially purified porcine zona pellucidae limits cub production

The present 2-year study investigated the feasibility of using porcine zona pellucidae (pZP) as antigen for immunocontraception in American black bears. Sows, 3–6 years of age, were administered either two doses of 250 µg pZP with Freund’s adjuvant (n = 10) or adjuvant alone (n = 5), one in April and one in May, and were kept away from the boars until June. Serum samples were collected before injections and before denning (November). The presence of sows with cubs at side was observed during premature emergence from denning. First-year results indicated that anti-pZP antibody titres in vaccinated sows were 2.5–9.0-fold (range) higher compared with non-vaccinated sows and that the vaccinated sows were threefold less likely to become pregnant (P = 0.167). Control and vaccinated bears produced 1.6 and 0.2 cubs per sow, respectively (P = 0.06). The second-year study investigated the feasibility of using pZP sequestered in a controlled-release pellet and a water-soluble adjuvant (QS-21) to avoid regulatory problems associated with Freund’s adjuvant. Sows in the treatment group (n = 22) were administered a single dose of an emulsion of 250 µg pZP and 150 μg QS-21 plus a pellet containing 70–90 µg pZP for delayed release as booster dose. Control sows (n = 5) received the QS-21 adjuvant in pellet alone. Serum samples were collected before inoculations (April) and before denning (November). Seven cubs were born to the five control sows, but none was born to the 22 vaccinated sows (P < 0.001). Anti-pZP antibody mean absorbance ratios in control sows remained at background levels, whereas vaccinated sows had ratios fourfold higher than controls. Two-dimensional polyacrylamide gel electrophoresis and immunohistochemical localisation confirmed immunoreactivity of sera from inoculated bears. We conclude that cub production in the American black bear can be effectively limited with either two injections of 250 μg pZP or a single inoculation of partially purified pZP sequestered in controlled-release pellets.

Evaluation of the Contraceptive Potential of brZPCp Vaccine in BALB/c Mice: Their Safety and Efficacy

In this study we have examined the potential ability of Microtus branditi partial ZPC (brZPCp) cDNA sequence (436-1150 nt) as a target for immunocontraception. Immunogenicity studies and fertility trials were performed in BALB/c mice using recombinant construction pCR3.1-brZPC(p). ELISA outcome indicated that antibodies could be generated by immunized mice, and IgG titer was increased compared to the control. Immunohistochemistry outcome indicated that antibodies could recognize native ZP in vivo, which in turn, prevented the binding of sperm to ovulated eggs. Antibodies could also recognize recombinant protein expressed by BL21 in vitro, which was confirmed by SDS-PAGE and Western blot. Fertility rate was reduced by 45% compared to the control immunized with pCR3.1. Meanwhile, there was no incidence of significant ovarian pathology in treated mice. This experiment indicates that this vaccine can elicit the specific antibody which binds exactly to the corresponding ZPC. This construction is proved to be immunogenic, and can reduce fertility without obvious oophoritis. The result in this study suggests a potentially important method for controlling population for its safety and easy production.

Embryonic diapause and its regulation

Embryonic diapause, a condition of temporary suspension of development of the mammalian embryo, occurs due to suppression of cell proliferation at the blastocyst stage. It is an evolutionary strategy to ensure the survival of neonates. Obligate diapause occurs in every gestation of some species, while facultative diapause ensues in others, associated with metabolic stress, usually lactation. The onset, maintenance and escape from diapause are regulated by cascades of environmental, hypophyseal, ovarian and uterine mechanisms that vary among species and between the obligate and facultative condition. In the best-known models, the rodents, the uterine environment maintains the embryo in diapause, while estrogens, in combination with growth factors, reinitiate development. Mitotic arrest in the mammalian embryo occurs at the G0 or G1 phase of the cell cycle, and may be due to expression of a specific cell cycle inhibitor. Regulation of proliferation in non- mammalian models of diapause provide clues to orthologous genes whose expression may regulate the reprise of proliferation in the mammalian context.

Alterations in the Ovarian Transcriptome During Primordial Follicle Assembly and Development1

The assembly of the developmentally arrested primordial follicle and subsequent transition to the primary follicle are poorly understood processes critical to ovarian biology. Abnormal primordial follicle development can lead to pathologies such as premature ovarian failure. The current study used a genome-wide expression profile to investigate primordial follicle assembly and development. Rat ovaries with predominantly unassembled, primordial, or primary follicles were obtained. RNA from these ovaries was hybridized to rat microarray gene chips, and the gene expression (i.e., ovarian transcriptome) was compared between the developmental stages. Analysis of the ovarian transcriptome demonstrated 148 genes up-regulated and 50 genes down-regulated between the unassembled and primordial follicle stages. Observations demonstrate 80 genes up-regulated and 44 genes down-regulated between the primordial and primary follicle stages. The analysis demonstrated 2332 genes common among the three developmental stages, 146 genes specific for the unassembled follicles, 94 genes specific for the primordial follicles, and 151 genes specific for the primary follicles. Steroidogenic genes are up-regulated between unassembled and primordial follicles, and then many are again down-regulated between primordial and primary follicles. The hormones inhibin and Mullerian inhibitory substance (MIS) display a similar pattern of expression with the highest levels of mRNA in the primordial follicles. Several novel unknown genes that had dramatic changes in expression during primordial follicle development were also identified. Gene families/clusters identified that were up-regulated from unassembled to primordial follicles include growth factors and signal transduction gene clusters, whereas a down-regulated gene family was the synaptonemal complex genes associated with meiosis. Gene families/clusters that were up-regulated between primordial and primary follicles included immune response genes, metabolic enzymes, and proteases, whereas down-regulated gene families include the globulin genes and some steroidogenic genes. The expression of several growth factors changed during primordial follicle development, including vascular endothelial growth factor and insulin-like growth factor II. Elucidation of how these changes in gene expression coordinate primordial follicle assembly and the primordial to primary follicle transition provides a better understanding of these critical biological processes and allows selection of candidate regulatory factors for further investigation.

Biosynthesis of the Canine Zona Pellucida Requires the Integrated Participation of Both Oocytes and Granulosa Cells1

In the dog, attempts to localize the expression of zona pellucida (ZP) proteins during folliculogenesis have failed to demonstrate conclusively whether any or all of the zona proteins are synthesized in the oocyte or the granulosa cells. Probing of paraformaldehyde-fixed prepubertal canine ovarian tissue sections with a panel of fluorescently conjugated lectins localized the expression of glycoproteins during folliculogenesis. We confirm that six lectins (PSA, s-WGA, ECL, GSL-II, LEL, and STL) consistently labeled the ZP and adjacent granulosa cells of the developing follicle and that canine ZP expresses beta-gal(1,4)glcNAc, beta-gal(1,3)galNac, alpha-mannose, and terminal sialic acid residues in a developmentally specific manner. Riboprobes for canine ZPA and ZPC genes were produced and used for in situ hybridization studies of mRNA expression in canine folliculogenesis. In addition, we isolated a partial cDNA transcript from total ovarian RNA for the canine ZPB gene having a high degree of sequence identity with the felid and porcine ZPB homologues. Subsequently, the ZPA gene transcripts were localized to the cytoplasm of oocytes in primordial, primary, and early secondary follicles. We then localized expression of ZPB and ZPC gene transcripts to the granulosa cells of growing follicles, but not in squamous granulosa cells of primordial follicles or oocytes. These observations indicate that in the juvenile canine ovary, the oocyte is responsible for synthesis of the ZPA protein and directing synthesis of the ZPB and ZPC proteins by the granulosa cells and that ZP gene transcription occurs in a sequential manner during folliculogenesis.

Intercellular communication in the mammalian ovary: oocytes carry the conversation

The production of functional female gametes is essential for the propagation of all vertebrate species. The growth of oocytes within ovarian follicles and their development to mature eggs have fascinated biologists for centuries, and scientists have long realized the importance of the ovarian follicle's somatic cells in nurturing oogenesis and delivering the oocyte to the oviduct by ovulation. Recent studies have revealed key roles of the oocyte in folliculogenesis and established that bidirectional communication between the oocyte and companion somatic cells is essential for development of an egg competent to undergo fertilization and embryogenesis. The challenge for the future is to identify the factors that participate in this communication and their mechanisms of action.