Development of Mouse Embryos in Organ Cultures of Fallopian Tubes on A Chemically Defined Medium

Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy

The female reproductive lifespan is highly dependent on egg quality, especially the presence of a normal number of chromosomes in an egg, known as euploidy. Mistakes in meiosis leading to egg aneuploidy are frequent in humans. Yet, knowledge of the precise genetic landscape that causes egg aneuploidy in women is limited, as phenotypic data on the frequency of human egg aneuploidy are difficult to obtain and therefore absent in public genetic datasets. Here, we identify genetic determinants of reproductive aging via egg aneuploidy in women using a biobank of individual maternal exomes linked with maternal age and embryonic aneuploidy data. Using the exome data, we identified 404 genes bearing variants enriched in individuals with pathologically elevated egg aneuploidy rates. Analysis of the gene ontology and protein-protein interaction network implicated genes encoding the kinesin protein family in egg aneuploidy. We interrogate the causal relationship of the human variants within candidate kinesin genes via experimental perturbations and demonstrate that motor domain variants increase aneuploidy in mouse oocytes. Finally, using a knock-in mouse model, we validate that a specific variant in kinesin KIF18A accelerates reproductive aging and diminishes fertility. These findings reveal additional functional mechanisms of reproductive aging and shed light on how genetic variation underlies individual heterogeneity in the female reproductive lifespan, which might be leveraged to predict reproductive longevity. Together, these results lay the groundwork for the noninvasive biomarkers for egg quality, a first step toward personalized fertility medicine.

Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy

The female reproductive lifespan depends on egg quality, particularly euploidy. Mistakes in meiosis leading to egg aneuploidy are common, but the genetic landscape causing this is not well understood due to limited phenotypic data. We identify genetic determinants of reproductive aging via egg aneuploidy using a biobank of maternal exomes linked with maternal age and embryonic aneuploidy data. We found 404 genes with variants enriched in individuals with high egg aneuploidy rates and implicate kinesin protein family genes in aneuploidy risk. Experimental perturbations showed that motor domain variants in these genes increase aneuploidy in mouse oocytes. A knock-in mouse model validated that a specific variant in kinesin KIF18A accelerates reproductive aging and diminishes fertility. These findings suggest potential non-invasive biomarkers for egg quality, aiding personalized fertility medicine.

One sentence summary

The study identifies novel genetic determinants of reproductive aging linked to egg aneuploidy by analyzing maternal exomes and demonstrates that variants in kinesin genes, specifically KIF18A , contribute to increased aneuploidy and accelerated reproductive aging, offering potential for personalized fertility medicine.

In vitro production of naked mole-rats' blastocysts from non-breeding females using in vitro maturation and intracytoplasmic sperm injection

The African naked mole-rat (Heterocephalus glaber) is an attractive model for cancer and aging research due to its peculiar biological traits, such as unusual long life span and resistance to cancer. The establishment of induced pluripotent stem cells (iPSCs) would be a useful tool for in vitro studies but, in this species, the reprogramming of somatic cells is problematic because of their stable epigenome. Therefore, an alternative approach is the derivation of embryonic stem cells from in vitro-produced embryos. In this study, immature oocytes, opportunistically retrieved from sexually inactive females, underwent first in vitro maturation (IVM) and then in vitro fertilization via piezo-intracytoplasmic sperm injection (ICSI). Injected oocytes were then cultivated with two different approaches: (i) in an in vitro culture and (ii) in an isolated mouse oviduct organ culture system. The second approach led to the development of blastocysts, which were fixed and stained for further analysis.

Mouse embryo assay for human in vitro fertilization quality control: a fresh look

The mouse embryo assay (MEA) has been used in the field of human in vitro fertilization (IVF) for multiple purposes such as developing embryo culture media, quality control within the laboratory, and procedural training and proficiency testing for embryology staff. In addition, manufacturing companies use the MEA as a means of quality control for the development of embryo culture media and medical devices and to meet the standards of testing for FDA approval of new products. It has long been considered by embryologists and laboratory scientists whether the MEA is an accurate or sensitive test in the quality assessment of culture media and medical devices or if use of this testing is more an obligation. There is no uniformly accepted gold standard method for IVF lab quality control or FDA approval. This review aims to revisit the role of the use of mouse embryos in the formulation of IVF media for clinical use and the different methods of employing the mouse embryo assay for quality control. In addition, we will review the use of the MEA as an important adjunct in the training for embryology staff and fellows in training in reproductive endocrinology and infertility (REI), as well as alternatives to the use of the MEA for these purposes.

High Potassium Concentration during Culturing of Early Mammalian Embryos: Normal or Extreme Situation?

Analysis of the element composition of oviduct and uterine fluid in mammals showed high potassium concentrations in the early embryo microenvironment in vivo. The results of early embryogenesis of mammals in vitro in the presence of high potassium concentrations are discussed. The data are summarized in accordance with the conditions of experimentally modeled pre-implantation development. Comparative assessment of the quality of embryo development until the blastocyst stage in vitro proved the embryos more successfully developed at potassium concentrations close to those registered in the oviductal fluid.

IVF culture media: past, present and future

BACKGROUND

The advances in the world of IVF during the last decades have been rapid and impressive and culture media play a major role in this success. Until the 1980s fertility centers made their media in house. Nowadays, there are numerous commercially available culture media that contain various components including nutrients, vitamins and growth factors. This review goes through the past, present and future of IVF culture media and explores their composition and quality assessment.

METHODS

A computerized search was performed in PubMed regarding IVF culture media including results from 1929 until March 2014. Information was gathered from the websites of companies who market culture media, advertising material, instructions for use and certificates of analysis. The regulation regarding IVF media mainly in the European Union (EU) but also in non-European countries was explored.

RESULTS

The keyword 'IVF culture media' gave 923 results in PubMed and 'embryo culture media' 12 068 results dating from 1912 until March 2014, depicting the increased scientific activity in this field. The commercialization of IVF culture media has increased the standards bringing a great variety of options into clinical practice. However, it has led to reduced transparency and comparisons of brand names that do not facilitate the scientific dialogue. Furthermore, there is some evidence suggesting that suboptimal culture conditions could cause long-term reprogramming in the embryo as the periconception period is particularly susceptible to epigenetic alterations. IVF media are now classified as class III medical devices and only CE (Conformité Européene)-marked media should be used in the EU.

CONCLUSION

The CE marking of IVF culture media is a significant development in the field. However, the quality and efficiency of culture media should be monitored closely. Well-designed randomized controlled trials, large epidemiological studies and full transparency should be the next steps. Reliable, standardized models assessing multiple end-points and post-implantation development should replace the mouse embryo assay. Structured long-term follow-up of children conceived by assisted reproduction technologies and traceability are of paramount importance.

Nonspecies-specific effects of mouse oviducts on the development of bovine IVM/IVF embryos by a serum free co-culture

In Experiment 1, development of bovine embryos derived from in vitro-matured (IVM) and in vitro-fertilized (IVF) oocytes was examined under 4 culture conditions: 1) co-culture with mouse ampullae continuously for 8 d, 2) co-culture with mouse ampullae that were replaced with fresh ampullae at 48-h intervals, 3) co-culture with bovine granulosa cell monolayers, and 4) culture in medium alone. Culture medium consisted of tissue culture medium 199 (TCM-199) supplemented with 1% fetal calf serum (FCS). Inseminated oocytes were transferred to each of the culture treatment 24 h after insemination and were cultured for 8 d. The number of blastocysts per number of cleaved ova obtained after co-culture with mouse ampullae (42.9%) was significantly (P<0.05) higher than that obtained after co-culture with granulosa cell monolayers (28.3%) or culture without cells (4.2%). In Experiment 2, the developmental ability of bovine IVM/IVF embryos co-cultured with mouse ampullae supplemented with or without serum was examined. When serum was excluded from the culture medium, 26.4% (33 125 ) of the total number of embryos cultured were able to develop to the blastocysts stage using this co-culture system. This value was comparable to that obtained in a serum-supplemented co-culture system (30.7%; 39 125 ). In addition, the developmental ability of embryos that reached to the 4-cell stage or beyond at 46 to 48 h after insemination was not significantly different when the embryos were co-cultured with mouse ampullae with (38.5 vs 44.6%) or without (37.0 vs 33.8%) serum.

Culture systems: single step

Culture media to support development of zygotes to the blastocyst stage is based either on a single medium or sequential (two-step) media. Single medium culture either with or without day 3 renewal is associated with simplified laboratory protocols and lower costs compared with sequential medium. There are currently insufficient clinical data to conclude that one system, either single or sequential, is superior to the other with regard to clinical performance. This chapter summarizes the rationale for use of a single medium, along with supporting animal and human data for culturing embryos in a single medium, renewed or not renewed.

Utility of animal models for human embryo culture development: rodents

Advancements in clinical human embryo culture over the last 30-40 years have been supported by research conducted with embryos from rodent and domestic species. The mouse has been the primary rodent species that has contributed to improved embryo culture outcomes. Numerous parameters applied in the beginning of experiments, during progress of experiments, and as end-point measures provide varying degrees of rigor and interpretive strength and/or complexity. A nonexhaustive discussion of these parameters is presented with important emphasis on experimental design to obtain the greatest power of intraexperimental interpretation of inferior, equivalent, or improved culture conditions in the mouse model. Additionally, data are presented demonstrating the inherent flaw of overinterpretation of interexperimental outcome comparisons and caution of expectations of data translation from the mouse to the human embryo culture scenario. Finally, a materials, methods, and notes discussion enumerates important steps in use of mouse embryos as a bioassay tool, independent of whether they are being used in an experiment focused on quality control or improving culture conditions.

Embryo Culture Media, Culture Techniques and Embryo Selection: A Tribute to Wesley Kingston Whitten

This review article gives a brief history of the classical experiments that led to the development of the embryo culture medium and in vitro embryo culture. It proposes that, in view of the outstanding and significant pioneering contributions of Wesley Kingston Whitten to the development of embryo culture medium, he be considered the “Father of Embryo Culture Medium”. Furthermore, it describes the nutritional requirements of early embryos and how these requirements with specific references to carbohydrates, amino acids, phosphates, growth factors, etc, have been utilized to formulate increasingly more complex embryo culture media. This has led to the development of progressively more efficacious embryo culture media including the formulation of completely defined and synthetic protein-free embryo culture medium. The review also describes physical factors, growth factors, insemination methods for the fertilization of oocytes and culture methods affecting embryo growth, development, metabolism, oxygen embryotoxicity and survival. In procedural terms, the review also summarizes the evolution of embryo culture techniques from tube culture to, microdrop culture under oil to co-culture to ultra microdrop culture techniques. It includes techniques of in vitro maturation and for the selection of potentially viable embryos of various developmental stages.

Consequences of in vitro culture conditions on embryo development and quality

Despite major efforts directed at improving the yield of blastocysts from immature oocytes in vitro, the quality of such blastocysts continually lags behind that of blastocysts produced in vivo. These differences are manifested at the level of morphology, metabolism, gene expression and cryotolerance, and may have a knock-on effect further along the developmental axis. Evidence suggesting that in vitro culture conditions, while capable of producing blastocysts in relatively high numbers, are far from optimal with deficiencies being manifested in terms of abnormally large offspring. It is clear nowadays that modification of the post-fertilization culture environment in vitro can improve blastocyst quality to some extent.

Development and pattern of mRNA relative abundance of bovine embryos cultured in the isolated mouse oviduct in organ culture

The aim of this study was to examine the development of bovine zygotes in isolated mouse oviducts (IMO) and the quality of the blastocysts produced. In vitro produced bovine zygotes were transferred into the ampullae of the IMO and cultured in SOF or KSOM. Control embryos were cultured in droplets of the same media. Following 6 days of culture, blastocysts were processed for nuclei counts or mRNA abundance. Culture in the IMO did not affect the proportion of zygotes developing to the blastocyst stage compared to the respective control droplets (SOF: 17.7 +/- 3.2% vs. 18.8 +/- 2.7%; KSOM: 20.7 +/- 2.6% vs. 22.2 +/- 2.8%). Culture in the IMO in KSOM resulted in an increased number of inner cell mass (ICM) nuclei; however, total nuclei number or incidence of apoptosis was unaffected. Culture in the IMO in SOF resulted in an increase (P < 0.05) in abundance of transcripts in blastocysts for Oct-4 and SOX, and reduced abundance of Glut-1, Na/K, Cx43, and survivin compared to blastocysts derived from culture in SOF alone. In contrast, culture in the IMO in KSOM resulted in increased abundance of transcripts for Glut-1, Cx43, Oct-4, and survivin and reduced expression of Na/K and SOX compared to KSOM alone. Transcripts for G6PDH, IFN-tau, and E-Cad were unaffected. These data confirm that the IMO is capable of supporting development of bovine embryos. Depending on the basal medium used, the pattern of transcript abundance in embryos derived from the IMO is similar to that of in vivo derived embryos.

Role of oocyte-specific genes in the development of mammalian embryos

Studies on oocyte-specific genes are important in understanding the genetic pathways essential for folliculogenesis, oogenesis and early embryogenesis. Although the molecular mechanisms regulating oocyte growth and embryo development in mammals have partially been unraveled by gene knockout studies, many aspects concerning reproduction remain to be determined. Development of mammalian embryos starts with the fusion of sperm and egg. After fertilization, the first major developmental transition, maternal to zygotic transition, occurs at the specific stages of preimplantation development in each mammal. The transition is called zygotic gene activation (ZGA) or embryonic genome activation. The ZGA is one of the most important events that occur during preimplantation development; however, the mechanism of the event remains unknown. Because the development until the transition is maintained by maternally inherited proteins and transcripts stored in the oocytes, it is highly likely that these products play an important role in the initiation of ZGA. Several maternal-effects genes that are specifically expressed in oocytes have been identified and their involvement in preimplantation development has been revealed. Therefore, to study oocyte-specific gene regulation would help not only to understand the precise mechanisms of mammalian development, but also to show the mechanisms of reproductive disorders, such as premature ovarian failure and infertility. (Reprod Med Biol 2006; 5: 175-182).

Differences in proteinase digestibility of the zona pellucida of in vivo and in vitro derived porcine oocytes and embryos

Embryo transfer practitioners know very well that, in a variety of species, there are differences between in vitro- and in vivo-derived embryos. It is assumed that these differences are results of suboptimal in vitro conditions leading to cytoplasmic and nuclear imperfections that will result in decreased embryo viability. In the present investigation the resistance of the zona pellucida of in vivo- and ex vivo-derived porcine embryos to a proteolytic enzyme is addressed. Ovulated but unfertilized oocytes, in vitro and in vivo-derived embryos of various developmental stages were exposed to a 0.5% pronase solution. The zonae of ovulated oocytes and in vivo-derived embryos at various stages of development took much longer to be digested than zonae of comparable in vitro-stages. Residence of in vitro derived embryos in an oviduct, no matter whether excised or in situ, significantly increased the zona resistance to pronase digestion. Embryonal stages normally residing in the uterus exhibited a distinctly decreased zona resistance to pronase. The culture of IVF embryos in an excised oviduct brought about a 6- to 14-fold increase in time required for zona digestion. A 24 h residence of IVF-derived embryos in the oviduct of a live recipient resulted in a digestion time for the zona of, on average, 48 h versus 1.4 h in the controls. Individual differences were substantial. The observations suggest that there must be structural changes in the zona pellucida or some sort of protective coating deposited while ova or embryos reside in the oviduct supplying protection against the action of proteolytic enzymes.

Cyclin A2 is phosphorylated during the G2/M transition in mouse two-cell embryos

In the present study, we investigated the expression of cyclin A2 in mouse two-cell embryos to elucidate the role of cyclin A2 at the G2/M transition. Two forms of cyclin A2 on SDS-PAGE (an upper and a lower band) were detected in two-cell embryos synchronized at the M phase by nocodazole. To investigate the nature of this shift, embryos synchronized at the M phase were treated with alkaline phosphatase (AP). The upper band of cyclin A2 was fainter in AP-treated embryos than in nontreated embryos. This result indicates that cyclin A2 in mouse two-cell embryos is phosphorylated and the band on SDS-PAGE shifts up during the G2/M transition. In addition, we examined the sequential expression of cyclin A2 in two-cell blocked embryos after OA treatment. The upper band of cyclin A2 was first detected at 2 hr after the treatment, corresponding to the timing of Cdc2 kinase activation. In two-cell embryos after removal from nocodazole treatment, the phosphorylated form of cyclin A2 protein decreased abruptly just before cytokinesis. These results suggest that the mechanism of cyclin A2 degradation in mouse two-cell embryos may be different from that in somatic cells.

Nuclear accumulation of cyclin B1 in mouse two-cell embryos is controlled by the activation of Cdc2

In the present study, the sequential expression and cellular localization of cyclin B1 was examined in two-cell mouse embryos to elucidate the mechanism of the two-cell block. One-cell embryos derived from in vitro fertilization were cultured with oviductal tissue (nonblocking condition) or without oviductal tissue (blocking condition) to establish the experimental conditions in which the embryos either overcome the two-cell block or do not. The amount of cyclin B1 gradually increased through the second cell cycle (through S to G2 phase). However, the difference was not observed between culture conditions. This showed that even embryos exhibiting the two-cell block normally synthesize cyclin B1 through the cell cycle. Cyclin B1 in embryos cultured under nonblocking condition accumulates in the nucleus during the transition from the G2 to the M phase, whereas that in embryos cultured in blocking condition localizes in the cytoplasm throughout the cell cycle. These data indicate that two-cell embryos cultured in blocking condition are able to normally synthesize cyclin B1 but have defects in nuclear accumulation of the protein. However, when two-cell blocked embryos were treated with okadaic acid, an activator of Cdc2 kinase, part of cyclin B1 in the embryos translocated into the nucleus. Moreover, treatment with butyrolactone I, a specific inhibitor of Cdc2 kinase, inhibits nuclear translocation of cyclin B1 in those embryos. These results suggest that Cdc2 kinase regulates the nuclear accumulation of cyclin B1 in mouse two-cell embryos.

Analysis of gene expression in mouse 2-cell embryos using fluorescein differential display: comparison of culture environments

The effect of the oviductal environment on gene expression in 2-cell mouse embryos was examined with mRNA differential display. Embryos used for experiments were cultured in modified Whitten medium with or without oviductal tissue until late 2-cell stage. The results of sequencing indicated that the genes for ATP synthase (ATPase 6), S:-adenosylmethionine decarboxylase (S:-AMDC) and nuclear autoantigenic sperm protein (NASP) were differentially expressed in embryos cultured in the oviductal environment (nonblocking culture condition). The ATPase 6 gene is encoded by mitochondrial DNA and is essential for the production of ATP. This indicates that the expression of ATP synthesis-related genes at the 2-cell stage may be required to maintain normal development in vitro. S:-Adenosylmethionine decarboxylase decarboxylates adenosylmethionine, which is a substrate of DNA methylation. The expression of S:-AMDC may be responsible for the low level of methylation of preimplantation development. As NASP is a histone-binding protein that is thought to be testis and sperm specific, its function in embryos remains unclear. On the other hand, the Tcl1 gene and a novel gene, the c-1 gene, were strongly expressed in embryos cultured without oviductal tissue (blocking culture condition). The expression patterns of these genes are quite similar. However, the detailed functions of these genes in embryos remain to be determined.

In vitro stimulation of cumulus-cell expansion by human cord serum in mouse oocyte-cumulus complexes

PURPOSE

The aim of this study was to test whether human cord serum (HCS) containing gonadotropins has an effect on the expansion of oocyte-cumulus complexes (OCCs).

METHODS

The concentration of follicle stimulating hormone (FSH) and luteinizing hormone (LH) was measured in HCS by radioimmunoassay (RIA). After short-term culture (4 hr) with or without OCCs, medium containing 0.4% bovine serum albumin (BSA) as control or 10% HCS was collected and analyzed for its concentration of estradiol, progesterone, and testosterone.

RESULTS

The FSH concentration was at the basal level, but the LH level was as high as 142.4 mIU/ml in both natured and denatured serum. Undetectable levels of steroids were observed in control media with or without OCCs. In contrast, a moderate amount of steroid hormones was detected in culture medium containing HCS. OCCs secreted a minute amount of steroid hormones in response to HCS. Similar patterns of cumulus expansion were observable by treatment with HCS, human chorionic gonadotropin (hCG), or HCS plus hCG after 4, 8, or 22 hr of culture. However, no cumulus expansion was observed in controls.

CONCLUSION

These results suggest that LH in HCS induces cumulus expansion but does not affect the secretion of steroid hormones by OCCs during culture.

The effect of activin-A on the development of mouse preimplantation embryos in vitro

PURPOSE

Our purpose was to clarify the involvement of transforming growth factor-beta (TGF-beta) family in the regulation of preimplantation embryo development.

METHODS

The effects of activin-A and TGF-beta on the rates of morula and blastocyst formations as well as on the cleavage velocity of a mouse two-cell embryo in vitro were analyzed. The gene expressions of these two growth factors in various developmental stages were also studied using RT-PCR.

RESULTS

Activin-A at a concentration of 0.2 ng/ml significantly stimulated not only the rate of morula formation but also the velocity of embryo cleavage, whereas no significant effect was found with TGF-beta. RT-PCR revealed that activin-A subunit mRNA, but not TGF-beta mRNA, was detected in preimplantation mouse embryo at any developmental stage.

CONCLUSIONS

Activin-A plays an important role in the regulation of preimplantation mouse embryo development in an autocrine fashion.

Optimizing tubal epithelial cell growth promotes mouse embryo hatching in coculture

PURPOSE

This study investigates the relationship between human tubal epithelial cell growth characteristics and mouse embryonic development to determine which cellular requirements should be preferentially provided in a coculture system.

METHODS

Cell growth and viability were assessed for 5 days in alpha-minimal essential medium or human tubal fluid supplemented with 10% human serum or 10% synthetic serum. Two-cell mouse embryo development to blastocyst and hatching blastocyst stages was also assessed with or without coculture.

RESULTS

Both epithelial cell growth and embryo development were dependent on serum supplementation with better cell viability and growth rates in human serum and better blastocyst development in synthetic serum. The highest proportion of hatching blastocysts was found in alpha-minimal essential medium and human serum with coculture.

CONCLUSIONS

Culture conditions which improve tubal epithelial cell growth also improve the hatching rate of mouse embryos in coculture. This indicates that by meeting the metabolic and nutritional demands for epithelial cell growth, the beneficial effects of coculture on embryo development may be optimized.

Oviductins possess chitinase- and mucin-like domains: a lead in the search for the biological function of these oviduct-specific ZP-associating glycoproteins

Over the last 10 years considerable progress has been made in the immunological and biochemical characterization of oviduct-specific glycoproteins. It is now well established that a subclass of these secretory products, designated as oviductins, associate with the zona pellucida of the ovulated oocyte and with the early embryo. Recent reports on the cloning of cDNAs of oviductins from various species, including that of golden hamster (Mesocricetus auratus) oviductin by our laboratory, allowed us to compare their deduced amino acid sequences with those of other proteins. Optimal alignment analysis showed that oviductins contain regions of significant similarity with catalytically inactive mammalian members of the bacterial and microfilarial chitinase protein family. Most importantly, a close examination of the hamster and human deduced amino acid sequences revealed that both glycoproteins possess contiguous Ser/Thr rich repeated units, clustered in their carboxy-terminal portions. These mucin-type motifs are similar in the hamster and human glycoprotein, although hamster oviductin contains more of these complete units. This striking feature might indicate that these molecules play a similar role to mucin-type glycoproteins, e.g., in protecting the oocyte and early embryo against attacks from their environment. We propose a model whereby oviductins are targeted to the oocyte via the interaction of their chitinase-like domains with specific oligosaccharide moieties of the zona pellucida. Once localized to this structure, oviductin molecules would act as a protective shield around the oocyte and early embryo by virtue of their densely glycosylated mucin-type domains.

Activin beta A subunit is expressed in bovine oviduct

It is evident that members of several growth factor families are actively involved in embryogenesis from its earliest phases. Several reports also indicate the oviduct as a possible source of growth factors, suggesting an active role of this organ in mammalian embryonic development. The aim of this study was to investigate the presence of activin/inhibin subunits in bovine oviduct since activin is a well-characterised morphogen in amphibian development. The presence of transcripts for alpha, beta A, and beta B subunits was investigated by analysing oviduct epithelial cells mRNA with reverse transcription-polymerase chain reaction (RT-PCR). Moreover, antisera specific for the three subunits were used for the Western blot analysis of the proteins secreted by oviduct epithelial cells in vitro and for their immunohistochemical localisation in different oviductal regions. Oviduct epithelial cells expressed only the beta A-subunit gene. Immunoreactive material was present among in vitro secreted proteins, indicating that the transcript is translated into a polypeptide that has been localised in the epithelium of both the ampullary and isthmic tract of the organ. Consistent with these results, the antisera for the alpha and beta B subunits did not recognise any specific antigen either among secreted proteins or in the sections. These results indicate that beta A subunit gene is expressed in bovine oviduct epithelial cells, and the protein is secreted in vitro and can be found along the whole extension of the organ. In the absence of alpha or beta B subunits, this suggests that activin A is present in bovine oviduct.(ABSTRACT TRUNCATED AT 250 WORDS)

Culture of bovine embryos to the blastocyst stage using Buffalo rat liver (BRL) cells

A comparison was made between the development of in vitro matured and fertilized bovine oocytes in co-culture with bovine oviduct epithelial (BOE) cells or with Buffalo rat liver (BRL) cells. Both cell types supported development from the 1-cell to the blastocyst stage with equal efficiencies (4.4% for BRL cells, 4.0% for BOE cells). Medium conditioned by either cell type supported development to the blastocyst stage as efficiently as co-cultures (6.4 and 7.3% blastocysts for BOE and BRL conditioned medium, respectively). A higher percentage of blastocyst development was found when embryos were cultured closely apposed in small drops of BRL-conditioned medium compared with larger volumes (20.5 versus 7.0%). The ability of BRL-conditioned medium to support embryonic development was dependent on the duration of the conditioning period (optimum 24 to 48 h), and was not lost when the medium was stored at -20 degrees C for extended periods. The effects were independent of the conditions used to promote maturation in vitro and the procedure for fertilization. With 2 different methods to produce embryos in culture, both the BRL cell co-culture and BRL-conditioned medium in microdrops supported embryo development to the blastocyst stage. The use of the BRL cell line reduces the variability associated with primary BOE cell cultures.

Successful freezing of unfertilized mouse oocytes and effect of cocultures in oviducts on development of in vitro fertilized embryos after thawing

PURPOSE

To establish a freeze-thawing method for unfertilized oocytes with a high success rate, we examined several conditions for freeze-thawing. The effects of EDTA and cocultures in oviducts on the development of embryos fertilized in vitro after thawing were also studied.

RESULTS

In the first experiment, unfertilized oocytes that were frozen in 1.5 M dimethylsulfoxide (DMSO) supplemented with 0.2 M sucrose by a slow freeze-thawing method showed the best results (fertilization rate, 71.9%; blastocyst rate per frozen oocyte, 18.8%). The proportion of embryos that developed to blastocysts was significantly higher when DMSO was added at 4 degrees C than at room temperature (39.4 vs 19.4%; P < 0.01). The addition of EDTA (10 microM) to the culture medium did not promote embryo development after fertilization in vitro. However, the rate of development of in vitro fertilized embryos to blastocysts after thawing was significantly higher when the embryos were cultured in oviducts in vitro than the rates in control cultures and those cultured with EDTA (blastocyst rate from fertilized oocytes, 71.4 vs 51.0 and 52.8%, respectively; P < 0.01).

CONCLUSION

Unfertilized mouse oocytes can be cryopreserved successfully by a slow freeze-thawing method with the addition of 1.5 M DMSO and 0.2 M sucrose at low temperatures, and coculture with oviducts enhances the development of embryos that are fertilized in vitro after thawing.

Porcine oviductal cells support in vitro bovine embryo development

This study was designed to investigate the developmental competency of in vitro-matured and in vitro-fertilized bovine embryos co-cultured with a) medium alone, b) bovine oviductal cells (BOC), c) bovine conditioned medium (BCM), d) porcine oviductal cells (POC), and porcine conditioned medium (PCM). Follicular oocytes collected from cattle at local slaughterhouses were matured and fertilized in vitro. Epithelial cells were scraped from the luminal surface tissue of either bovine or porcine oviducts collected after ovulation, cultured in TALP + 10% heat-treated fetal calf serum, and the conditioned media were collected following a 3- to 5-d incubation period. After 18 to 22 h of sperm-ova co-incubation, the fertilized and/or cleaved ova were randomly assigned to 1 of 5 co-culture groups. The results revealed that the efficiency of medium alone in supporting embryo development from the 16- to 32-cell stage up to the blastocyst stage was significantly (P<0.01) lower than of embryos co-cultured with either bovine or porcine epithelial cells, or with conditioned media from such cells. Epithelial cell co-culture, regardless of cell source, was more effective (P<0.01) than culture with conditioned medium. Co-culture in medium containing or conditioned by porcine cells was more effective in supporting bovine embryo development than co-culture with bovine-derived cells or conditioned medium. These data support the concept that oviductal cells produce a soluble component which enhances embryo development to the blastocyst stage in vitro and that the effect is not species-specific.

In vitro synthesis of oviductal secretory proteins by estrogen-treated ovariectomized gilts

The objective of this study was to identify, characterize, and examine oviductal secretory proteins (OSP) synthesized de novo by whole oviduct (WO), ampulla (A), and isthmic (I) tissue from ovariectomized (OVX), corn oil (CO)-, estrogen (E)-, progesterone (P)-, and E + P-treated gilts. Oviducts were collected from OVX gilts after CO, E, P, or E + P treatment for 11 consecutive days and tissue was incubated with 3H-leucine (3H-leu). Rates of 3H-leu incorporation into nondialyzable macromolecules by WO explants were greater (P less than 0.01) with E- compared to CO-, P-, or E + P-treated gilts and greater (P less than 0.05) by A explants with E- compared to CO-, P-, or E + P-treated gilts. An effect of location was noted, with A having a greater (P less than 0.01) rate of incorporation than WO or I. Conditioned culture medium was analyzed by one (1D)- and two-dimensional (2D) sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. Analyses by 1D-SDS-PAGE revealed three major E-dependent bands (335,000, 100,000, and 80,000 M(r)) in WO and A, and one (335,000 M(r)) in the I. A 20,000 M(r) band found in A was inhibited by E, while a 60,000 M(r) band found in the A was induced by P. Analyses by 2D-SDS-PAGE resolved major E-dependent bands 2 (100,000 M(r)) and 3 (80,000 M(r)) into basic and acidic 100,000 M(r) proteins and a 75,000-85,000 M(r) protein (pI less than 4), respectively, found in WO and A, but not in I. A basic 20,000 M(r) protein and an acidic 45,000 M(r) complex, both found in A, were inhibited by E. Gel filtration of culture medium revealed a high M(r) fraction (greater than 2 x 10(6)) that was induced by E and was 6.8-fold greater in medium from A than from I. This study clearly demonstrates that 1) WO and A tissue from E-treated gilts de novo synthesize and secrete three major proteins (basic 100,000, acidic 100,000, and 75,000-85,000 M(r)); 2) these E-dependent proteins are not found in I or with other treatment; 3) several protein complexes synthesized by A are inhibited by E treatment; and 4) a high M(r) fraction, produced primarily in the A, is induced or amplified by E.

An improved medium for long-term culture of human embryos overcomes the in vitro developmental block and increases blastocyst formation

OBJECTIVE

To determine if a culture medium, designated CZB after the authors who first described it, which is supplemented with 0.11 mM ethylenediaminetetraacetic acid, 1.0 mM glutamine, 31.30 mM lactate, and 0.27 mM pyruvate and is lacking glucose for the initial stages of culture that overcomes the in vitro two-cell block of mouse embryos, can improve the rate of blastocyst formation of human embryos in long-term cultures and increase the pregnancy rate (PR) when used in a clinical in vitro fertilization (IVF) program.

DESIGN

The study is in two parts. Initially, excess oocytes from IVF and gamete intrafallopian transfer patients were fertilized in vitro and then placed in long-term culture of either CZB plus 10% heat-inactivated human serum (32 zygotes) or Earle's balanced salt solution (EBSS) supplemented with 0.45 mM pyruvate plus 10% human serum (28 zygotes) to determine if CZB medium could enhance in vitro development and increase blastocyst formation when compared with EBSS. Subsequently, CZB or EBSS medium was used for short-term cultures of embryos in a clinical IVF program to determine if the use of CZB could increase the clinical IVF PR.

SETTING

Private practice of one author (M.D.).

PATIENTS

The excess oocytes were donated by couples not wishing to have cryopreservation. In the clinical trial, 49 couples presenting with tubal or male factor infertility and who had three or more fertilized zygotes were randomly assigned to one of the culture media being used.

RESULTS

In long-term cultures, embryos were observed at 42, 66, 90, 114, and 138 hours after fertilization and scored for blastomere number, degree of fragmentation, and developmental arrest. When CZB- and EBSS-cultured embryos were evaluated over 138 hours, there was a significant increase in the number of CZB-cultured embryos reaching the blastocyst stage (56% versus 20%; P less than 0.009) and less fragmentation of CZB-cultured embryos (18.8% versus 50%; P less than 0.01). In short-term cultures, pronuclear stage embryos from patients undergoing IVF were cultured in CZB or EBSS for 24 hours, graded, and then used in embryo transfers. Of the 28 patients assigned to EBSS, 6 became pregnant (21.4%), and of the 21 assigned to CZB, 5 attained pregnancy (23.8%). These results were not significantly different.

CONCLUSIONS

The use of CZB for the long-term culture of human embryos is highly beneficial and increases the rate of blastocyst formation, but its use in an IVF program does not increase the clinical PR.

Culture of one-cell bovine embryos in explanted mouse oviduct and bovine oviductal epithelial cells

One-cell bovine embryos fertilized in vivo were cultured in TCM-199 and bovine oviductal epithelial cells, in TCM-199, or in explanted immature mouse oviducts supported by TCM-199 to compare development to the blastocyst stage. The morphological stage of development and cell number were determined following 144 hours of culture. Of the embryos that cleaved at least once, 52.6, 30.4 and 0.0% developed to the morula/blastocyst stage after culture in oviductal epithelial cells, in TCM-199 alone, or in explanted mouse oviducts, respectively. The mean total cell number for embryos cultured in oviductal epithelial cells (24.5) was higher than for embryos cultured in TCM-199 (12.8) or in explanted mouse oviducts (5.9; P<0.05). The mean cell number of embryos cultured in TCM-199 or in explanted mouse oviducts did not differ. The explanted immature mouse oviduct supported by TCM-199 did not provide an environment adequate for development of one-cell bovine embryos to the blastocyst stage. Development of one-cell bovine embryos was best supported by co-culture with oviductal epithelial cells in TCM-199 medium.

Oxidative stress on mouse embryo development in vitro

Oxygen radicals are involved in the in vitro block phenomenon of embryo development, because a low oxygen tension and superoxide dismutase (SOD) have been shown to promote the in vitro development of mouse embryos. One of the target molecules damaged by oxygen radicals may be the thiol (SH) group of proteins because it is readily oxidized. In this study, we evaluated the effects of thioredoxin, which is a powerful protein disulfide reductase, on mouse (Institute of Cancer Research, ICR) preimplantation embryo development. Culture of mouse pronuclear embryos recovered 17 h after human chorionic gonadotrophin (hCG) administration in the presence of thioredoxin (200 micrograms/mL) significantly increased the blastulation rate (75.3%) when compared to the control culture system (8.9%). The effects of thioredoxin were observed only from the pronuclear stage to the two-cell stage (17-48 h after hCG administration). An additive effect of thioredoxin and SOD, or thioredoxin and a low oxygen tension, was observed. These results suggest that the oxidation of the SH group of proteins is one of the causes of developmental blockage of embryos in vitro. The target protein for reduction by thioredoxin has not been identified yet, but thioredoxin will be a new clue for clarifying the mechanism of blocking development in vitro.

Co-culture of day-5 to day-7 equine embryos in medium with oviductal tissue

Oviductal and uterine embryos were collected from mares at 5 to 7 days following ovulation 1) to evaluate the effects of oviductal tissue explants on in vitro growth and development of equine embryos and 2) to study the morphologic development of equine embryos in culture. Embryos were incubated for 5 days in a medium (control group) or in medium supplemented with oviductal tissue explants (co-culture group). Embryos were evaluated and the media changed daily. Following 5 days in culture, 10 10 (100%) control embryos and 27 29 (93%) co-cultured embryos had doubled in diameter. All embryos that were recovered as morulae developed to the blastocyst stage in culture. By 5 days in culture, 6 10 (60%) control embryos and 19 29 (66%) co-cultured embryos had reached the hatching blastocyst stage of development. By 3 days in culture, significantly more (P<0.05) control embryos versus co-cultured embryos had degenerated (4 10 vs 2 29 , respectively). By 5 days in culture, significantly more (P<0.01) control embryos versus co-cultured embryos had degenerated (6 10 vs. 3 29 , respectively). Embryos cultured with oviductal tissue were sustained longer than embryos cultured in medium alone. Hatching was characterized by the blastocyst squeezing through a small opening in the zona pellucida or by the zona pellucida thinning over approximately half of the blastocyst surface and subsequently disappearing entirely.

Involvement of superoxide radicals in the mouse two-cell block

The effect of oxygen toxicity on the development of mammalian embryos was assessed by the use of superoxide dismutase (SOD), a potent scavenger of superoxide radicals. Mouse pronuclear embryos recovered 17 h after human chorionic gonadotropin (hCG) were cultured in medium BWW at 37 degrees C under an atmosphere of 5% CO2 in air. Culture of mouse pronuclear embryos in the presence of Cu.Zn-SOD (500 micrograms/ml) significantly increased the blastulation rate (44.6%) when compared with the control culture system (4.2%). Essentially the same effects were observed in SOD containing either Mn or Fe in the catalytic center. Heat treatment of the SOD preparation, and the addition of anti-SOD antibodies to the culture medium, significantly reduced the attenuation of the two-cell block by SOD, indicating that this effect is SOD dependent. SOD activity was detected in rabbit oviduct fluid (3.675 +/- 3.084 mIU/mg protein) by electron spin resonance. These results suggest that active oxygen is involved in the two-cell block phenomenon in mouse embryos exposed to air and that SOD in the oviduct may play an important role in the protection of embryos from superoxide radicals.

A consideration of the factors which influence and control the viability and developmental potential of the preimplantation embryo

The advent of the new reproductive technologies (including in vitro fertilization) has led to a revolution in the treatment of infertility. It has not yet led to a marked improvement in our understanding of the control of development and of viability of the early embryo. It is the poor viability of embryos, with consequent implantation failure, which is the major limiting factor to successful outcomes. While much of the research in this area has concentrated on strategies of ovulation induction, experimental models have shown that the major cause of reduced embryo viability is due to the actual process of fertilization in vitro and subsequent culture of the preembryo in synthetic culture medium. It is likely that this is due to the absence of critical nutrients or trophic factors of maternal origin and work with co-culture of embryos with somatic cells suggests improved viability can be achieved. Such co-culture is not an option for routine clinical use, however. It is essential therefore to understand by detailed study of the physiology of embryonic development their requirements for optimal development. The empirical approach of comparing different formulations of culture media is unlikely to be successful because of the vast range of parameters to be tested and the large number of pregnancies required to demonstrate a significant improvement in outcome. The strategy that is most likely to be successful in the future, therefore, is the use of appropriate experimental models, such as the developing rodent embryo, to understand the essential physiological changes in the embryo during its development, the control processes in place, and the effect of the embryo's environment on the processes. This will allow the rational design of culture media which can then be rigorously tested for improved outcome. An example of successful application of this approach is the discovery of embryo-derived platelet activating factor (PAF). The production of embryo-derived PAF was first described and validated in the rodent. In the same species it was shown to have an essential role in pregnancy and to act as an autocrine mediator of embryo viability. This fundamental observation in rodents was then confirmed in humans, and recent work has shown that supplementation of culture human embryo media with PAF results in a dramatic increase in their developmental and pregnancy potential. This example should be the first of many such improvements based on a more fundamental understanding of the embryo's developmental requirements.

Culture medium and protein supplementation influence in vitro fertilization and embryo development in the domestic cat

The influence of culture medium and protein supplements on in vitro fertilization (IVF) and morula-to-blastocyst development in culture was examined in the domestic cat. In Study I, follicular oocytes were fertilized and cultured in 1) modified Krebs Ringer bicarbonate (mKRB); 2) modified Tyrode's solution (TALP) without phosphate or glucose; or 3) Ham's F10. All media contained bovine serum albumin (BSA). Fertilization rates were similar (P greater than .05) among mKRB (75.0%), TALP (70.6%), and Ham's F10 (80.0%) treatments. Compared to TALP (77.8%), more (P less than .05) embryos in Ham's F10 (95.0%) developed to the morula stage; development of mKRB embryos (88.9%) was intermediate and not different (P greater than .05). Study II evaluated the effects of protein availability and type on IVF and embryo growth. Ham's F10 was supplemented with polyvinylalcohol (PVA, 2 mg/ml), BSA (4 mg/ml), fetal calf serum (FCS, 5%), or estrous cat serum (ECS, 5%) and used to fertilize and culture embryos. Fertilization was enhanced (P less than .05) using either FCS (84.0%) or ECS (85.2%) compared to PVA (67.3%). Oocytes exposed to BSA fertilized at a rate (76.1%) similar (P greater than .05) to other treatments. Embryos exposed to all four treatment groups (PVA, 82.8%; BSA, 82.8%; FCS, 92.9%; or ECS, 97.8%) were equally capable (P greater than .05) of becoming morulae. However, more FCS- or ECS-supplemented morulae continued to the early blastocyst stage (30.8%, 22.2%, respectively, P less than .05) than PVA- (10.3%) or BSA- (13.8%) exposed morulae. In the domestic cat IVF system, the type of medium and protein supplement used appears to have a greater impact on embryo development in vitro than on fertilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Co-culture of rabbit 2-cell embryos with rabbit oviduct epithelial cells and other somatic cells

Rabbit 2-cell embryos were co-cultured in Basel Synthetic Medium II + 10% fetal bovine serum with one of the following: primary cultures of rabbit oviduct epithelial cells (ROEC), a rabbit kidney epithelioid cell line (RK13), a rabbit epidermal epithelioid cell line (Sf1), or a rabbit skin fibroblast-like cell line (RAB9). Embryos cultured in medium alone served as controls. After 4 d of culture at 39 degrees C in 5% CO2 in air, 77-93% of the rabbit embryos which were co-cultured with somatic cells had reached the blastocyst stage, and 60-76% were hatching through their zonae pellucidae. These percentages, however, were not significantly different (P greater than .05) from those of embryos in medium alone, of which 90% had reached the blastocyst stage and 83% were hatching. Mean intrazonal embryo diameters also did not differ significantly among treatments (239-302 microns). Bovine 1-8-cell embryos were also co-cultured with ROEC. This stimulated 60% of these embryos to develop beyond the so-called "16-cell block" in vitro, whereas 0% of the embryos cultured in medium alone developed past this block. Evaluation of the ROEC cultures by light microscopy, immunocytochemistry, and gel electrophoretic analysis of conditioned medium, together with the positive results with bovine embryos, indicate that the ROEC culture partially simulates oviductal conditions in vivo. Therefore, our results suggest that oviduct epithelial cells may play a less pivotal role in regulating early development in the rabbit than in the cow.(ABSTRACT TRUNCATED AT 250 WORDS)

Cumulus cell dispersion induced by estradiol in mouse oviduct in vitro

Dispersion of cumulus cells in nonmated mice is completed in the oviduct 15-20 h after ovulation. Oviducts, isolated 1 h after ovulation (13 h post-human chorionic gonaditropin), were cultured in vitro for 40 h. In these oviducts, denuded oocytes were first seen at 30 h of culture, indicating that cumulus dispersion proceeded at a slower rate in vitro. Oocyte denudation was accelerated in a dose-dependent manner by the addition of estradiol to the culture medium in which oviducts were incubated. The addition of progesterone or cycloheximide to the culture medium strongly inhibited oocyte denudation even in the presence of estradiol. When isolated cumuli were incubated in the absence of oviductal tissue, the rate of cell dispersion was slower than that of cumuli incubated inside the oviduct and the addition of estradiol to the culture failed to accelerate this process. On the basis of these data, we propose that cumulus cell dispersion is accelerated by an estrogen-dependent protein produced by the oviduct and that this effect of estrogen is antagonized by progesterone.

Development of porcine embryos from the one-cell stage to blastocyst in mouse oviducts maintained in organ culture

Successful development of porcine embryos from the one-cell stage to the blastocyst stage has been accomplished using mouse oviducts in organ culture. One-cell embryos were transferred to mouse oviducts maintained in organ culture and were cultured for 6 days. Control embryos from each donor pig were cultured in a modified Krebs-Ringer bicarbonate medium. Thus control and experimental embryos obtained from the same individual pig could be directly compared. At the end of the culture period, all embryos were scored for the stage of development attained and stained to allow the cell number of each embryo to be counted. In medium alone, only 35.7% of the one-cell embryos reached the morula or blastocyst stage, whereas 78.1% of the one-cell embryos transferred to mouse oviducts reached the morula or blastocyst stage. Of those embryos reaching the morula or blastocyst stage, cell numbers were similar for the two treatments (medium alone vs. oviduct culture). The procedure described for mouse oviduct organ culture provides a simple method for culturing early-stage pig embryos to the morula or blastocyst stage prior to embryo transfer.