Natural history of the female germ cell from its origin to full maturation through prenatal ovarian development

Reproductive, Obstetric and Neonatal Outcomes in Women with Congenital Uterine Anomalies: A Systematic Review and Meta-Analysis

Congenital uterine anomalies (CUA) may influence reproductive performance, resulting in adverse pregnancy associated complications. This study aimed to assess the association of CUA subtypes with reproductive, obstetric, and perinatal outcomes. We performed a systematic search of the MEDLINE, EMBASE, and Cochrane libraries for studies comparing pregnancy outcomes between women with CUA and those with a normal uterus. The random effects model was used to estimate the odds ratios (ORs) with a 95% confidence interval (CI). Women with CUA had a lower rate of live births (OR 0.47; 95% CI 0.33-0.69), and a higher rate of first trimester miscarriage (OR, 1.79; 95% CI 1.34-2.4), second trimester miscarriage (OR 2.92; 95% CI 1.35-6.32), preterm birth (OR 2.98; 95% CI 2.43-3.65), malpresentation (OR 9.1; 95% CI 5.88-14.08), cesarean section (OR 2.87; 95% CI 1.56-5.26), and placental abruption (OR 3.12; 95% CI 1.58-6.18). Women with canalization defects appear to have the poorest reproductive performance during early pregnancy. However, unification defects were associated with obstetric and neonatal outcomes throughout the course of pregnancy. It may be beneficial for clinicians to advise on potential complications that may be increased depending on the type and severity of CUA.

At the Crossroads of Fate-Somatic Cell Lineage Specification in the Fetal Gonad

The reproductive endocrine systems are vastly different between males and females. This sexual dimorphism of the endocrine milieu originates from sex-specific differentiation of the somatic cells in the gonads during fetal life. Most gonadal somatic cells arise from the adrenogonadal primordium. After separation of the adrenal and gonadal primordia, the gonadal somatic cells initiate sex-specific differentiation during gonadal sex determination with the specification of the supporting cell lineages: Sertoli cells in the testis vs granulosa cells in the ovary. The supporting cell lineages then facilitate the differentiation of the steroidogenic cell lineages, Leydig cells in the testis and theca cells in the ovary. Proper differentiation of these cell types defines the somatic cell environment that is essential for germ cell development, hormone production, and establishment of the reproductive tracts. Impairment of lineage specification and function of gonadal somatic cells can lead to disorders of sexual development (DSDs) in humans. Human DSDs and processes for gonadal development have been successfully modeled using genetically modified mouse models. In this review, we focus on the fate decision processes from the initial stage of formation of the adrenogonadal primordium in the embryo to the maintenance of the somatic cell identities in the gonads when they become fully differentiated in adulthood.

Taking control of the female fertile lifespan: a key role for Bcl-2 family proteins

Precisely how the length of the female fertile lifespan is regulated is poorly understood and it is likely to involve complex factors, one of which is follicle number. Indeed, the duration of female fertility appears to be intimately linked to the number of available oocytes, which are stored in the ovary as primordial follicles. There is mounting evidence implicating the intrinsic apoptosis pathway, which is controlled by members of the B-cell lymphoma-2 (BCL-2) family, as a key regulator of the number of primordial follicles established in the ovary at birth and maintained throughout reproductive life. Consequently, the pro- and anti-apoptotic BCL-2 family proteins are emerging as key determinants of the length of the female fertile lifespan. This review discusses the relationship between the intrinsic apoptosis pathway, follicle number and length of the female fertile lifespan.

Incidence of intracranial germ cell tumors by race in the United States, 1992-2010

Little is known about the etiology of intracranial germ cell tumors (iGCTs), although international incidence data suggest that the highest incidence rates occur in Asian countries. In this analysis, we used 1992-2010 data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program to determine whether rates of iGCT were also high in Asian/Pacific Islanders living in the United States. Frequencies, incidence rates and survival rates were evaluated for the entire cohort and for demographic subgroups based on sex, age category (0-9 and 10-29 years), race (white, black, and Asian/Pacific Islander), and tumor location (pineal gland vs. other) as sample size permitted. Analyses were conducted using SEER*Stat 8.1.2. We observed a significantly higher incidence rate of iGCT in Asian/Pacific Islanders compared with whites (RR = 2.05, 95 % CI 1.57-2.64, RR = 3.04, 95 % CI 1.75-5.12 for males and females, respectively) in the 10-29 year age group. This difference was observed for tumors located both in the pineal gland and for tumors in other locations. Five-year relative survival differed by demographic and tumor characteristics, although these differences were not observed in comparisons limited to cases treated with radiation. Increased incidence rates of iGCT in individuals of Asian descent in the SEER registry are in agreement with data from the International Agency for Research on Cancer, where Japan and Singapore were among the countries with highest incidence. The increased incidence in individuals of Asian ancestry in the United States suggests that underlying genetic susceptibility may play a role in the etiology of iGCT.

PUMA regulates germ cell loss and primordial follicle endowment in mice

The number of primordial follicles initially established within the ovary is influenced by the extent of germ cell death during foetal ovarian development, but the mechanisms that mediate this death have not been fully uncovered. In this study, we identified BBC3 (PUMA) (p53 upregulated modulator of apoptosis, also known as BCL2-binding component 3), a pro-apoptotic BH3-only protein belonging to the BCL2 family, as a critical determinant of the number of germ cells during ovarian development. Targeted disruption of the Bbc3 gene revealed a significant increase in the number of germ cells as early as embryonic day 13.5. The number of germ cells remained elevated in Bbc3−/− female mice compared with WT female mice throughout the remainder of embryonic and early postnatal life, resulting in a 1.9-fold increase in the number of primordial follicles in the ovary on postnatal day 10. The increase in the number of germ cells observed in the ovaries of Bbc3−/− mice could not be attributed to the altered proliferative activity of germ cells within the ovaries. Furthermore, BBC3 was found to be not required for the massive germ cell loss that occurs during germ cell nest breakdown. Our data indicate that BBC3 is a critical regulator of germ cell death that acts during the migratory phase of oogenesis or very soon after the arrival of germ cells in the gonad and that BBC3-mediated cell death limits the number of primordial follicles established in the initial ovarian reserve.

Involvement of doublesex and mab-3-related transcription factors in human female germ cell development demonstrated by xenograft and interference RNA strategies

We identified three doublesex and mab-3-related transcription factors (DMRT) that were sexually differentially expressed in human fetal gonads and present in the ovaries at the time of meiotic initiation. These were also identified in murine embryonic female germ cells. Among these, we focused on DMRTA2 (DMRT5), whose function is unknown in the developing gonads, and clarified its role in human female fetal germ cells, using an original xenograft model. Early human fetal ovaries (8-11 weeks post-fertilization) were grafted into nude mice. Grafted ovaries developed normally, with no apparent overt changes, when compared with ungrafted ovaries at equivalent developmental stages. Appropriate germ cell density, mitotic/meiotic transition, markers of meiotic progression and follicle formation were evident. Four weeks after grafting, mice were treated with siRNA, specifically targeting human DMRTA2 mRNA. DMRTA2 inhibition triggered an increase in undifferentiated FUT4-positive germ cells and a decrease in the percentage of meiotic γH2AX-positive germ cells, when compared with mice that were injected with control siRNA. Interestingly, the expression of markers associated with pre-meiotic germ cell differentiation was also impaired, as was the expression of DMRTB1 (DMRT6) and DMRTC2 (DMRT7). This study reveals, for the first time, the requirement of DMRTA2 for normal human female embryonic germ cell development. DMRTA2 appears to be necessary for proper differentiation of oogonia, prior to entry into meiosis, in the human species. Additionally, we developed a new model of organ xenografting, coupled with RNA interference, which provides a useful tool for genetic investigations of human germline development.

Female reproductive aging is master-planned at the level of ovary

The ovary receives a finite pool of follicles during fetal life. Atresia remains the major form of follicular expenditure at all stages since development of ovary. The follicular reserve, however, declines at an exponential rate leading to accelerated rate of decay during the years preceding menopause. We examined if diminished follicle reserve that characterizes ovarian aging impacts the attrition rate. Premature ovarian aging was induced in rats by intra-embryonic injection of galactosyltransferase-antibody on embryonic day 10. On post-natal day 35 of the female litters, either a wedge of fat (sham control) or a wild type ovary collected from 25-day old control rats, was transplanted under the ovarian bursa in both sides. Follicular growth and atresia, and ovarian microenvironment were evaluated in the follicle-deficient host ovary and transplanted ovary by real time RT-PCR analysis of growth differentiation factor-9, bone morphogenetic protein 15, and kit ligand, biochemical evaluation of ovarian lipid peroxidation, superoxide dismutase (SOD) and catalase activity, and western blot analysis of ovarian pro- and anti-apoptotic factors including p53, bax, bcl2, and caspase 3. Results demonstrated that the rate of follicular atresia, which was highly preponderant in the follicle-deficient ovary of the sham-operated group, was significantly prevented in the presence of the transplanted ovary. As against the follicle-deficient ovary of the sham-operated group, the follicle-deficient host ovary as well as the transplanted ovary in the ovary-transplanted group exhibited stimulated follicle growth with increased expression of anti-apoptotic factors and down regulation of pro-apoptotic factors. Both the host and transplanted ovaries also had significantly lower rate of lipid peroxidation with increased SOD and catalase activity. We conclude that the declining follicular reserve is perhaps the immediate thrust that increases the rate of follicle depletion during the final phase of ovarian life when the follicle reserve wanes below certain threshold size.

The role of ovarian surface epithelium in folliculogenesis during fetal development of the bovine ovary: a histological and immunohistochemical study

Although many aspects of ovarian differentiation have been established, comparatively little is known about prenatal follicle formation and differentiation of bovine ovaries. The objective of this investigation was to study the role of the surface epithelium during the development of germ cell nests, germ cell cords and follicle formation in the fetal bovine ovary. Associated important proliferation and apoptotic features were further investigated. Additionally, the expression pattern of the S100 protein was detected. A strong increase of mitotic figures was detected in the surface epithelium, germ cell nests and germ cell cords of ovaries with a crown-rump length (CRL) of 13.0-58.0 cm. Oocytes were positively stained with S100 in bovine ovaries from fetuses with a CRL of 21.0 cm. The staining intensity enhanced parallel to increasing oocyte and follicle sizes during the ovary development. In later stages, a strong staining for S100 was observed in healthy oocytes in contradistinction to atretic oocytes where no expression of the S100 protein could be found. In conclusion, increasing mitosis index of surface epithelium cells, as well as oogonia directly beneath the surface epithelium, in combination with open surface connection during stages from a CRL of 11.0-94.0 cm of bovine fetal ovaries could play an important role in the period of time of ongoing folliculogenesis and derivation of granulosa cells. Additionally, S100-positive oocytes in primordial and later follicle stages joined by a high rate of Ki67-positive index in surrounding granulosa cells indicate that in the oocytes the S100 protein can perhaps be a useful marker for intact oocytes in bovine ovaries.

Mammalian foetal ovarian development: consequences for health and disease

The development of a normal ovary during foetal life is essential for the production and ovulation of a high-quality oocyte in adult life. Early in embryogenesis, the primordial germ cells (PGCs) migrate to and colonise the genital ridges. Once the PGCs reach the bipotential gonad, the absence of the sex-determining region on the Y chromosome (SRY) gene and the presence of female-specific genes ensure that the indifferent gonad takes the female pathway and an ovary forms. PGCs enter into meiosis, transform into oogonia and ultimately give rise to oocytes that are later surrounded by granulosa cells to form primordial follicles. Various genes and signals are implicated in germ and somatic cell development, leading to successful follicle formation and normal ovarian development. This review focuses on the differentiation events, cellular processes and molecular mechanisms essential for foetal ovarian development in the mice and humans. A better understanding of these early cellular and morphological events will facilitate further study into the regulation of oocyte development, manifestation of ovarian disease and basis of female infertility.

Apoptosis in the germ line

Apoptosis is a critical process for regulating both the size and the quality of the male and female germ lines. In this review, we examine the importance of this process during embryonic development in establishing the pool of spermatogonial stem cells and primordial follicles that will ultimately define male and female fertility. We also consider the importance of apoptosis in controlling the number and quality of germ cells that eventually determine reproductive success. The biochemical details of the apoptotic process as it affects germ cells in the mature gonad still await resolution, as do the stimuli that persuade these cells to commit to a pathway that leads to cell death. Our ability to understand and ultimately control the reproductive potential of male and female mammals depends upon a deeper understanding of these fundamental processes.

Trends in incidence and survival of pediatric and adolescent patients with germ cell tumors in the United States, 1975 to 2006

BACKGROUND

Pediatric germ cell tumors (GCTs) are rare and heterogeneous tumors with uncertain etiology. In the current study, data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program were used to evaluate trends in incidence and survival of GCTs in boys and girls ages ≤19 years. To the authors' knowledge, few studies to date have evaluated trends in pediatric GCTs. Results from these analyses may provide clues to the etiology of GCTs.

METHODS

Frequencies, incidence rates, and 5-year relative survival rates stratified by sex were evaluated overall and by demographic subgroups based on age (birth to 9 years and 10-19 years), race (white, black, and other), and ethnicity (non-Hispanic and Hispanic) as sample size permitted.

RESULTS

In whites, the incidence of GCTs was lower for females than males in the 10-year to 19-year age group (rate ratio [RR], 0.47; 95% confidence interval [95% CI], 0.42-0.53), whereas the rates were similar in the age group for birth to 9 years. In contrast, incidence rates were higher in black females than in black males in both age groups (RR, 2.01 [95%CI, 1.08-3.84] in those ages birth to 9 years; RR, 3.30 [95% CI, 2.13-5.28] in those ages 10-19 years). The incidence of ovarian GCT was significantly higher in Hispanic compared with non-Hispanic girls in the groups aged 10 to 19 years. Incidence rates increased during the study period in boys ages 10 to 19 years (annual percentage change [APC], 1.2; 95% CI, 0.4-2.1) and girls ages birth to 9 years (APC, 1.9; 95% CI, 0.3-2.5).

CONCLUSIONS

The incidence of pediatric GCTs in the United States appears to be increasing only in certain subgroups, suggesting that the etiology is not completely overlapping in all age groups. Differences in incidence patterns by race and ethnicity merit further investigation.

Congenital uterine anomalies and their impact on fertility

Congenital uterine anomalies are not uncommon. Many are asymptomatic and have been associated with normal and adverse reproductive outcomes. The interference of these anomalies with a patient's fertility is an interesting but still debatable issue, and the proper management of infertile women with many forms of these anomalies remains controversial. The current literature regarding the frequency and probable causes of infertility among women with congenital uterine anomalies is insufficient to allow any robust conclusions to be drawn. Diagnostic and selection bias, a lack of objective diagnostic criteria for the different anomaly types and heterogeneity of study designs have contributed to the conflicting results from different studies of the prevalence of these anomalies among the infertile and fertile populations. However, emerging evidence from recent literature suggests causal associations between these anomalies (particularly the septate uterus) and infertility, and demonstrates significant improvements in the fecundity of women with septate uteri and otherwise unexplained infertility after hysteroscopic metroplasty. This review provides a critical update of the state of knowledge regarding congenital uterine anomalies, our current understanding of their effect on fertility and discusses how they can be managed from the reproductive perspective.

Coordinated regulation of follicle development by germ and somatic cells

The continuum of folliculogenesis begins in the fetal ovary with the differentiation of the oogonia and their isolation within the primordial follicles. Primordial follicle activation is an enigmatic process, whereby some follicles enter the growing pool to become primary follicles, thereby embarking on an irreversible progression towards ovulation or atresia. This process is under the coordinated regulation of factors from the oocyte itself, as well as from the somatic cells of the ovary, in particular the theca and granulosa cells, which are structural components of the follicle. These two influences provide the principal stimuli for the growth of the follicle to the late preantral or early antral stage of development. The endocrine effects of the gonadotrophins FSH and LH are essential to the continued progression of the follicle and most atresia can be attributed to the failure to receive or process the gonadotrophin signals. The peri-ovulatory state has received intensive investigation recently, demonstrating a coordinated role for gonadotrophins, steroids, epidermal growth factor family proteins and prostaglandins. Thus, a complex programme of coordinated interaction of governing elements from both germ and somatic cell sources is required for successful follicle development.

Factors determining the risk of inadvertent retroviral transduction of male germ cells after in utero gene transfer in sheep

The possibility of permanent genetic changes to the germline is central to the bioethics of in utero gene therapy (IUGT) because of the concern of inadvertent potentially deleterious alterations to the gene pool. Despite presumed protection of the male germline due to early germ cell (GC) compartmentalization, we reported that GCs within the developing ovine testes are transduced at low levels after retrovirus-mediated IUGT, thus underscoring the need for a thorough understanding of GC development in clinically predictive models to determine the optimal time to perform IUGT and avoid germline modification. In the present studies, we used the fetal sheep model to analyze GCs for phenotype, location, proliferation, and incidence of transduction after IUGT at various fetal ages to learn when during development the nascent germline is likely to be at greatest risk of retrovirus-mediated alteration. Our studies show that although GCs were transduced at all injection ages, the levels of transduction varied by nearly 700-fold as a function of the age at transfer. After remaining largely quiescent as they migrated to/settled within nascent sex cords, GCs began active cycling before cord closure was complete, suggesting this is likely the point at which they would be most susceptible to retroviral transduction.Furthermore, we observed that compartmentalization of GCs continued into early postnatal life, suggesting the male germline may be vulnerable to low-level inadvertent retroviral vector modification throughout fetal life, but that this risk can be minimized by performing IUGT later in gestation.

Primordial follicular assembly in humans – revisited

Recent interest in the initial phases of ovarian follicular formation and development has lead to a number of publications in this area, most of which address the autocrine and paracrine factors involved in primordial follicle activation to primary follicle. Primordial follicle assembly (first step in follicle formation) determines the lifetime supply of primordial follicles and remains a poorly understood phenomenon. Despite a number of recent articles that are concentrating on immuno-histochemistry, basic steps in the process are not clear. Hence, we feel it is time to take a step back and see what is available in the literature and identify the gaps in which future research about primordial follicle assembly in humans needs to be directed.

Stem cells: a perspective on oocytes

Stem cells, with their unlimited self-renewal feature and their ability to differentiate into almost every mature cell type in the body, have enormous potential for research and therapeutic application. In this article, we review the formation of primordial germ cells, the precursors of adult gametocytes, from their specification to their migration to prospective gonads. We discuss recent studies that obtained germ cells from stem cells in vitro. We place special emphasis on studies that challenge the current dogma in reproductive biology that female mammals are born with a set number of nonrenewable germ cells in the ovary by showing germ cell renewal in the adult ovary.

Expression of bone morphogenetic proteins 4 and 7 and their receptors IA, IB, and II in human ovaries from fetuses and adults

OBJECTIVE

To investigate the immunocytochemical and mRNA expression of bone morphogenetic proteins 4 (BMP-4) and 7 (BMP-7) and their three receptors (BMPR-IA, BMPR-IB, and BMPR-II) in ovaries from human adults and fetuses.

DESIGN

Immunocytochemical and in situ hybridization study.

SETTING

Major tertiary care and referral academic centers.

PATIENT(S)

Sixteen adolescents/adults aged 13-38 years and 31 women undergoing second and third trimester pregnancy terminations.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Immunocytochemistry and in situ hybridization on paraffin sections of human ovaries from fetuses and adults.

RESULT(S)

The expression of the proteins for BMP-4 and BMP-7 and their receptors was detected in oogonia/oocytes and stroma cells from both sources (fetuses and women/adolescents). BMP-7 and the three receptors were identified in all of these granulosa cells, and BMP-4 was detected only in the granulosa cells of women/adolescents. Transcripts for all five ligands were identified in stroma cells of all samples and in fetal oogonia/oocytes. BMPR-IA and BMPR-IB mRNA expression was also identified in oocytes from women/adolescents. BMP-7 and BMPR-IA mRNA staining was detected in fetal granulosa cells.

CONCLUSION(S)

This is the first report of the expression of BMP-4 and BMP-7 and their receptors in human ovaries from fetuses as well as adults. However, to elucidate whether indeed BMP-4 or BMP-7 are involved in the initiation of human primordial follicular growth, they should be added to the culture medium.

Pluripotent stem cells and their niches

The ability of stem cells to self-renew and to replace mature cells is fundamental to ontogeny and tissue regeneration. Stem cells of the adult organism can be categorized as mono-, bi-, or multipotent, based on the number of mature cell types to which they can give rise. In contrast, pluripotent stem cells of the early embryo have the ability to form every cell type of the adult body. Permanent lines of pluripotent stem cells have been derived from preimplantation embryos (embryonic stem cells), fetal primordial germ cells (embryonic germ cells), and malignant teratocarcinomas (embryonal carcinoma cells). Cultured pluripotent stem cells can easily be manipulated genetically, and they can be matured into adult-type stem cells and terminally differentiated cell types in vitro, thereby, providing powerful model systems for the study of mammalian embryogenesis and disease processes. In addition, human embryonic stem cell lines hold great promise for the development of novel regenerative therapies. To fully utilize the potential of these cells, we must first understand the mechanisms that control pluripotent stem cell fate and function. In recent decades, the microenvironment or niche has emerged as particularly critical for stem cell regulation. In this article, we review how pluripotent stem cell signal transduction mechanisms and transcription factor circuitries integrate information provided by the microenvironment. In addition, we consider the potential existence and location of adult pluripotent stem cell niches, based on the notion that a revealing feature indicating the presence of stem cells in a given tissue is the occurrence of tumors whose characteristics reflect the normal developmental potential of the cognate stem cells.

Genetic analysis of chromosome pairing, recombination, and cell cycle control during first meiotic prophase in mammals

Meiosis is a double-division process that is preceded by only one DNA replication event to produce haploid gametes. The defining event in meiosis is prophase I, during which chromosome pairs locate each other, become physically connected, and exchange genetic information. Although many aspects of this process have been elucidated in lower organisms, there has been scant information available until now about the process in mammals. Recent advances in genetic analysis, especially in mice and humans, have revealed many genes that play essential roles in meiosis in mammals. These include cell cycle-regulatory proteins that couple the exit from the premeiotic DNA synthesis to the progression through prophase I, the chromosome structural proteins involved in synapsis, and the repair and recombination proteins that process the recombination events. Failure to adequately repair the DNA damage caused by recombination triggers meiotic checkpoints that result in ablation of the germ cells by apoptosis. These analyses have revealed surprising sexual dimorphism in the requirements of different gene products and a much less stringent checkpoint regulation in females. This may provide an explanation for the 10-fold increase in meiotic errors in females compared with males. This review provides a comprehensive analysis of the use of genetic manipulation, particularly in mice, but also of the analysis of mutations in humans, to elucidate the mechanisms that are required for traverse through prophase I.

Human centromeric alphoid domains are periodically homogenized so that they vary substantially between homologues. Mechanism and implications for centromere functioning

Sequence analysis of alphoid repeats from human chromosomes 17, 21 and 13 reveals recurrent diagnostic variant nucleotides. Their combinations define haplotypes, with higher order repeats (HORs) containing identical or closely-related haplotypes tandemly arranged into separate domains. The haplotypes found on homologues can be totally different, while HORs remain 99.8% homogeneous both intrachromosomally and between homologues. These results support the hypothesis, never before demonstrated, that unequal crossovers between sister chromatids accumulate to produce homogenization and amplification into tandem alphoid repeats. I propose that the molecular basis of this involves the diagnostic variant nucleotides, which enable pairing between HORs with identical or closely-related haplotypes. Domains are thus periodically renewed to maintain high intrachromosomal and interhomologue homogeneity. The capacity of a domain to form an active centromere is maintained as long as neither retrotransposons nor significant numbers of mutations affect it. In the presented model, a chromosome with an altered centromere can be transiently rescued by forming a neocentromere, until a restored, fully-competent domain is amplified de novo or rehomogenized through the accumulation of unequal crossovers.

Fetal hormones and sexual differentiation

The process of fetal sexual differentiation, which involves establishment of genetic sex, differentiation of the gonads, and development of phenotypic sex, is summarized. The morphologic changes that occur in utero that lead to development of the male and female gonads, germ cells, reproductive tracts, and external genitalia are described. Most of the article focuses on the hormones that regulate sexual differentiation and development in utero. The genetic factors that regulate sexual differentiation, which constitute a new and emerging field, also are discussed.

Renewed debate over postnatal oogenesis in the mammalian ovary

The central dogma of female reproductive biology has long held that oogenesis ceases prior to birth in mammals. During the first half of the last century, there was much debate about whether this was the case or whether oogenesis continued in the postnatal ovary. A report in 1951 effectively put an end to this debate and laid the foundation for the dogma. A new paper by Johnson et al. (2004) resurrects the debate over whether postnatal oogenesis occurs in the mammalian ovary. If confirmed, this would have tremendous impact on issues related to female fertility and reproductive longevity.

Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Epidemiology of gonadal germ cell cancer in males and females

The epidemiology of testicular germ cell cancer is relatively well understood, but less is known about the epidemiology of ovarian germ cell cancer. Cases of testicular (7910) and ovarian (453) germ cell cancer diagnosed 1960-1999 were extracted from the Thames Cancer Registry. The incidence rate in males doubled in the period from 2.0 to 4.4 per 100,000. In females the rate was much lower but the rate of increase over the period was similar to the increase in males. In both sexes the incidence increased sharply around the age of onset of puberty and decreased in older age groups. The biological mechanism of initiation of germ cell carcinogenesis is similar in males and females and probably occurs with roughly the same frequency in the two sexes. In males, the initiated cell population is promoted by the normal action of adult sex hormones to form carcinoma in situ, consisting of many millions of cells. The incidence of testicular cancer is rate limited by the development of carcinoma in situ. The key difference between males and females, which may explain the different levels of incidence, is the much lower number of susceptible cells in females at the time of puberty.

Fundamentals of human embryonic growth in vitro and the selection of high-quality embryos for transfer

Knowledge of the nature of embryo growth, and the handling and scoring of quality in human embryos are significant aspects for embryologists in IVF clinics. This review describes the formation, growth and maturation of human oocytes, many aspects of fertilization in vitro, embryonic transcription during preimplantation stages, and the formation of polarities, timing controls, role of mitochondria and functions of endocrine and paracrine systems. Modern concepts are fully discussed, together with their significance in the practice of IVF. This knowledge is essential for the correct clinical care of human embryos growing in vitro, especially in view of their uncharacteristic tendency to vary widely in implantation potential. Underlying causes of such variation have not been identified. Stringent tests must be enforced to ensure human embryos develop under optimal conditions, and are scored for quality using the most advanced techniques. Optimal methods of culture are described, including methods such as co-culture introduced to improve embryo quality but less important today. Detailed attention is given to quality as assessed from embryonic characteristics determined by timers, polarities, disturbed embryo growth and anomalous cell cycles. Methods for classification are described. Approaches to single embryo transfers are described, including the use of sequential media to produce high-quality blastocysts. These approaches, and others involved in surgical methods to remove fragments, transfer ooplasm or utilize newer approaches such as preimplantation diagnosis of chromosomal complements in embryos are covered. New outlooks in this field are summarized.

Female genital anomalies affecting reproduction

OBJECTIVE

A multitude of female congenital anomalies are uncommon. However, their impact on reproduction can be profound. The aim of this review is to remind the practicing physician of the clinically relevant embryology and summarize the studies that look at the impact of such various anomalies on a woman's fecundity. We review particular surgical therapies that possibly may improve fertility in such women.

DESIGN

Review and critique of available studies in which particular surgical therapies were done and whether they truly improved fertility in these women with congenital reproductive anomalies.

RESULTS

Clear evidence demonstrates that uterine septum resection is effective in women with demonstrated recurrent pregnancy losses. Arcuate uterus has little impact on reproduction. Other studies fail to definitively show that surgical correction will improve pregnancy retention or fertility except for specifically indicated clinical scenarios.

CONCLUSIONS

The practicing reproductive specialist should have working knowledge of evidence-based therapeutic options for women with reproductive congenital anomalies. A summary chart has been devised to clearly associate embryologic structures with normal adult derivative as well as anomalous structures.

Preliminary studies on apoptosis in human fetal ovaries

OBJECTIVE

To evaluate if apoptosis occurs in human germ cells between 19 and 33 gestational weeks (GW).

DESIGN

Human fetal ovaries were obtained from aborted fetuses aged 19-33 GW.

SETTING

Rabin Medical Center, a major tertiary care and referral center.

PATIENT(S)

Twenty-seven women undergoing pregnancy termination. The abortions were mostly because of fetal anatomical or chromosomal abnormalities.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Microscopy studies, terminal deoxynucleotidyl transferase (TdT) assay (TUNEL), and immunocytochemistry for B-cell lymphoma/leukemia-2 (bcl-2).

RESULT(S)

TUNEL assay revealed a slight increase in apoptotic oocytes in fetuses from 23 GW, with a peak at 27 GW. Overexpression of bcl-2 was detected in all ovarian components, regardless of fetal age.

CONCLUSION(S)

There seems to be a slight increase in apoptosis in oocytes from 23 GW with a peak at 27 GW. However, it is very unlikely that these low apoptotic rates could be the cause of the extensive germ cell loss throughout human pregnancy. The overexpression of bcl-2 possibly suggests either that this gene is necessary to overcome extensive apoptotic activity or that it is responsible for the low apoptosis rates. However, these results should be considered with caution, since the ovaries were mostly from abnormal fetuses after feticide.

Activation of follicle development: the primordial follicle

Investigations of primordial follicle formation and growth are fundamental to our understanding of female gamete production. In all mammalian females the full complement of oocytes is established during fetal development. This store of primordial follicles is not renewable and serves the entire reproductive life span of the adult. The correct programming of fetal ovarian development and the number of primordial follicles formed will therefore limit the fecundity of the ovary. Primordial follicles are characterized by the presence of a single oocyte surrounded by a varying number of pregranulosa cells. The relatively small size, undifferentiated status and large numbers of primordial follicles make them prime candidates for use in basic and applied research in animal production, gene transfer and cloning. Furthermore, the development of cell culture systems that use primordial follicles as a source of oocytes for in vitro growth and maturation will enable us to maximize the potential of high genetic merit females and to shorten generation intervals. Despite these possibilities, primordial follicles are the least understood of all stages of follicle development. The factor(s) responsible for maintaining the primordial pool or, conversely, for activating primordial follicle growth remain elusive.

Identification of BPESC1, a novel gene disrupted by a balanced chromosomal translocation, t(3;4)(q23;p15.2), in a patient with BPES

The blepharophimosis syndrome (BPES) is a rare genetic disorder characterized by blepharophimosis, ptosis, epicanthus inversus, and telecanthus. In type I, BPES is associated with female infertility, while in type II, the eyelid defect occurs by itself. The BPES syndrome has been mapped to 3q23. Previously, we constructed a YAC-, PAC-, and cosmid-based physical map surrounding the 3q23 translocation breakpoint of a t(3;4)(q23;p15.2) BPES patient, containing a 110-kb PAC (169-C 10) and a 43-kb cosmid (11-L 10) spanning the breakpoint. In this report, we present the identification of BPESC1 (BPES candidate 1), a novel candidate gene that is disrupted by the translocation on chromosome 3. Cloning of the cDNA has been performed starting from a testis-specific EST, AI032396, found in cosmid 11-L 10. The cDNA sequence of BPESC1 is 3518 bp in size and contains an open reading frame of 351 bp. No significant similarities with known proteins have been found in the sequence databases. BPESC1 contains three exons and spans a genomic fragment of 17.5 kb. Expression of BPESC1 was observed in adult testis tissue. We performed mutation analysis in 28 unrelated familial and sporadic BPES patients, but, apart from the disruption by the translocation, found no other disease-causing mutations. These data make it unlikely that BPESC1 plays a major role in the pathogenesis of BPES.