Growth factors in reproduction

OUP accepted manuscript

STUDY QUESTION

Can the accuracy of timing of luteal phase endometrial biopsies based on urinary ovulation testing be improved by measuring the expression of a small number of genes and a continuous, non-categorical modelling approach?

SUMMARY ANSWER

Measuring the expression levels of six genes (IL2RB, IGFBP1, CXCL14, DPP4, GPX3 and SLC15A2) is sufficient to obtain substantially more accurate timing estimates and to assess the reliability of timing estimates for each sample.

WHAT IS KNOWN ALREADY

Commercially available endometrial timing approaches based on gene expression require large gene sets and use a categorical approach that classifies samples as pre-receptive, receptive or post-receptive.

STUDY DESIGN, SIZE, DURATION

Gene expression was measured by RTq-PCR in different sample sets, comprising a total of 664 endometrial biopsies obtained 4–12 days after a self-reported positive home ovulation test. A further 36 endometrial samples were profiled by RTq-PCR as well as RNA-sequencing.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A computational procedure, named ‘EndoTime’, was established that models the temporal profile of each gene and estimates the timing of each sample. Iterating these steps, temporal profiles are gradually refined as sample timings are being updated, and confidence in timing estimates is increased. After convergence, the method reports updated timing estimates for each sample while preserving the overall distribution of time points.

MAIN RESULTS AND THE ROLE OF CHANCE

The Wilcoxon rank-sum test was used to confirm that ordering samples by EndoTime estimates yields sharper temporal expression profiles for held-out genes (not used when determining sample timings) than ordering the same expression values by patient-reported times (GPX3: P < 0.005; CXCL14: P < 2.7e−6; DPP4: P < 3.7e−13). Pearson correlation between EndoTime estimates for the same sample set but based on RTq-PCR or RNA-sequencing data showed a high degree of congruency between the two (P = 8.6e−10, R² = 0.687). Estimated timings did not differ significantly between control subjects and patients with recurrent pregnancy loss or recurrent implantation failure (P > 0.05).

LARGE SCALE DATA

The RTq-PCR data files are available via the GitHub repository for the EndoTime software at https://github.com/AE-Mitchell/EndoTime, as is the code used for pre-processing of RTq-PCR data. The RNA-sequencing data are available on GEO (accession GSE180485).

LIMITATIONS, REASONS FOR CAUTION

Timing estimates are informed by glandular gene expression and will only represent the temporal state of other endometrial cell types if in synchrony with the epithelium. Methods that estimate the day of ovulation are still required as these data are essential inputs in our method. Our approach, in its current iteration, performs batch correction such that larger sample batches impart greater accuracy to timing estimations. In theory, our method requires endometrial samples obtained at different days in the luteal phase. In practice, however, this is not a concern as timings based on urinary ovulation testing are associated with a sufficient level of noise to ensure that a variety of time points will be sampled.

WIDER IMPLICATIONS OF THE FINDINGS

Our method is the first to assay the temporal state of luteal-phase endometrial samples on a continuous domain. It is freely available with fully shared data and open-source software. EndoTime enables accurate temporal profiling of any gene in luteal endometrial samples for a wide range of research applications and, potentially, clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by a Wellcome Trust Investigator Award (Grant/Award Number: 212233/Z/18/Z) and the Tommy's National Miscarriage Research Centre. None of the authors have any competing interests. J.L. was funded by the Biotechnology and Biological Sciences Research Council (UK) through the Midlands Integrative Biology Training Partnership (MIBTP, BB/M01116X/1).

Growth Factors, and Cytokines; Understanding the Role of Tyrosine Phosphatase SHP2 in Gametogenesis and Early Embryo Development

Growth factors and cytokines have vital roles in germ cell development, gamete maturation, and early embryo development. Cell surface receptors are present for growth factors and cytokines to integrate with and trigger protein signaling in the germ and embryo intracellular milieu. Src-homology-2-containing phosphotyrosine phosphatase (SHP2) is a ubiquitously expressed, multifunctional protein that plays a central role in the signaling pathways involved in growth factor receptors, cytokine receptors, integrins, and G protein-coupled receptors. Over recent decades, researchers have recapitulated the protein signaling networks that influence gamete progenitor specification as well as gamete differentiation and maturation. SHP2 plays an indispensable role in cellular growth, survival, proliferation, differentiation, and migration, as well as the basic events in gametogenesis and early embryo development. SHP2, a classic cytosolic protein and a key regulator of signal transduction, displays unconventional nuclear expression in the genital organs. Several observations provided shreds of evidence that this behavior is essential for fertility. The growth factor and cytokine-dependent roles of SHP2 and its nuclear/cytoplasmic presence during gamete maturation, early embryonic development and embryo implantation are fascinating and complex subjects. This review is intended to summarize the previous and recent knowledge about the SHP2 functions in gametogenesis and early embryo development.

Citrullination regulates the expression of insulin-like growth factor-binding protein 1 (IGFBP1) in ovine uterine luminal epithelial cells

There are five peptidylarginine deiminase (PAD) isozymes designated as PADs 1, 2, 3, 4 and 6, and many are expressed in female reproductive tissues. These enzymes post-translationally convert positively charged arginine amino acids into neutral citrulline residues. Targets for PAD-catalyzed citrullination include arginine residues on histone tails, which results in chromatin decondensation and changes in gene expression. Some of the first studies examining PADs found that they are localized to rodent uterine epithelial cells. Despite these findings, the function of PAD-catalyzed citrullination in uterine epithelial cells is still unknown. To address this, we first examined PAD expression in uterine cross-sections from pregnant ewes on gestation day 25 (d25). Immunohistochemistry revealed that the levels of PADs 2 and 4 are robust in luminal and glandular epithelia compared with those of PADs 1 and 3. As PADs 2 and 4 have well-characterized roles in histone citrullination, we next hypothesized that PADs citrullinate histones in these uterine cells. Examination of caruncle lysates from pregnant ewes on gestation d25 and an ovine luminal epithelial (OLE) cell line shows that histone H3 arginine residues 2, 8, 17 and 26 are citrullinated, but histone H4 arginine 3 is not. Using a pan-PAD inhibitor, we next attenuated histone citrullination in OLE cells, which resulted in a significant decrease in the expression of insulin-like growth factor-binding protein 1 (IGFBP1) mRNA. As IGFBP1 is important for the migration and attachment of the trophectoderm to uterine endometrium, our results suggest that PAD-catalyzed citrullination may be an important post-translational mechanism for the establishment of pregnancy in ewes.

Both slowly developing embryos and a variable pace of luteal endometrial progression may conspire to prevent normal birth in spite of a capable embryo

Embryonic implantation requires synchrony between the endometrium and the embryo. When analyzed in isolation, competent embryos may be unsuccessful when placed on a nonreceptive endometrium or vice versa, contributing to the "black box" of implantation failure. It is when the two are assessed together that dyssynchrony becomes evident, due to premature progesterone stimulus on the endometrium, physiologic displacement of the window of implantation or late blastulation of the embryo, or all combined. From the embryonic component, detailed assessment of the timing of blastulation is essential. The molecular diagnosis of endometrial receptivity based on its transcriptomic signature could be superior to other techniques used in the past for defining the endometrial window of implantation.

Physiopathology of human embryonic implantation: clinical incidences

Embryo implantation consists of a series of events promoting the invasion of the endometrium and then the uterine arterial system by the extra-embryonic trophoblast. In order for this semi-heterologous implantation to succeed, the endometrium has to first undergo a number of structural and biochemical changes (decidualization). The decidua's various constituents subsequently play a role in the embryonic implantation. The third step is the transformation of the uterine vascular system and the growth of the placenta, which will provide the foetoplacental unit with nutrients. Several physiopathological aspects will be discussed: 1) the implantation window, regulated by maternal and embryonic hormonal secretions and thus influenced by any defects in the latter: dysharmonic luteal phase, 21-hydroxylase block, abnormal integrin expression, 2) the successive trophoblast invasions of uterine vessels which, when defective, lead to early embryo loss or late-onset vascular pathologies, as preeclampsia, 3) the pregnancy's immunological equilibrium, with a spontaneously tolerated semi-allogeneic implant, 4) the impact of pro-coagulant factors (thrombophilia) on the pregnancy's progression, 5) the environment of the uterus, ranging from hydrosalpinx to uterine contractions. In summary, the least anatomical or physiological perturbation can interfere with human embryonic implantation - a very particular phenomenon and a true biological paradox.

Elevated serum interleukin-1β levels and interleukin-1β-to-interleukin-1 receptor antagonist ratio 1 week after embryo transfer are associated with ectopic pregnancy

OBJECTIVE

To investigate whether interleukin-1β (IL-1β) and interleukin-1 receptor antagonist (IL-1RA) serum levels in the early luteal phase differ in IVF cycles that result in an ectopic pregnancy (EP) when compared with other outcomes.

DESIGN

Retrospective cohort.

SETTING

Not applicable.

PATIENT(S)

A total of 307 women whose serum samples were available, with the following IVF outcomes: 103 live births, 80 negative pregnancy tests, 52 biochemical pregnancies, 47 EPs, and 25 miscarriages.

INTERVENTION(S)

Serum samples were obtained on cycle days 24 and 28 (cycle day 14 = day of egg retrieval). Levels of IL-1β and IL-1RA were determined by quantitative ELISA performed by blinded personnel.

MAIN OUTCOME MEASURE(S)

IL-1β and IL-1RA levels, IL-1β-to-IL-1RA ratio versus cycle outcome.

RESULT(S)

The IL-1β levels were predictive of an EP. At cycle days 24 and 28 the mean IL-1β levels were higher in patients with an EP (127.1 pg/mL and 166.9 pg/mL, respectively) than in women with any other IVF outcome (15.8-55.3 pg/mL and 14.8-75.5 pg/mL, respectively). At cycle day 24 the IL-1β-to-IL-1RA ratio was 0.18 in the ectopic group versus 0.01-0.09 in the other groups.

CONCLUSION(S)

Elevated IL-1β levels and IL-1β-to-IL-1RA ratio as early as 4 days before the first pregnancy test are associated with an EP. If confirmed by prospective studies, clinical application of these findings could potentially improve EP detection.

Mitogen activated protein kinase pathway-dependent effects of platelet-derived growth factor on migration of trophectoderm cells

Successful development of the conceptus and implantation requires an intimate trophic connection between maternal uterus and conceptus mediated by local regulators including growth factors. Platelet-derived growth factor (PDGF) acts as a chemotactic factor for a variety of cell types. Current studies have determined that PDGF participates in rapid growth and development of cleavage stage embryos, but PDGF-induced effects on the growth and development of peri-implantation conceptus remains unknown. In the present study, PDGF induced phosphorylation of ERK1/2, AKT and RPS6 proteins in porcine trophectoderm (pTr) cells in a dose- and time-dependent manner. Addition of U0126 (an inhibitor of ERK1/2) or LY294002 (a PI3K inhibitor) blocked PDGF-induced effects on phosphorylation of signaling proteins. Combinations of PDGF and U0126 decreased PDGF-induced p-ERK1/2 and p-AKT1, but combinations of PDGF and LY294002 blocked only PDGF-induced AKT phosphorylation. Furthermore, PDGF significantly induced pTr cell migration and these stimulatory effects were blocked by U0126 and LY294002. Immunoreactive p-ERK1/2 and p-RPS6 proteins were abundant in pTr cells treated with PDGF, but U0126 reduced PDGF-induced p-ERK1/2 and p-RPS6 levels to basal amounts. Present study suggests that PDGF secreted into the maternal-conceptus microenvironment stimulates pTr cell migration through signal transduction cascades mediated by the ERK1/2 MAPK and AKT1 pathways.

Differential expression of functionality markers in mid-secretory endometrium of infertile women under treatment with ovulation-inducing agents

OBJECTIVES

To analyze the expression of protein markers related to cell proliferation and death, as well as oestrogen and progesterone receptors in the endometrium of infertile women with hypothalamic-pituitary dysfunction treated with clomiphene citrate (CC) or recombinant follicle-stimulating hormone (rFSH), and compare them with ovulatory women.

STUDY DESIGN

The study included 12 control ovulatory women and 29 anovulatory women, 19 of whom underwent ovulation induction with CC (n = 12) or rFSH (n = 5). Endometrial biopsies were obtained by Pipelle during the mid-secretory phase. Samples were stained with haematoxylin and eosin. Immunohistochemistry of proteins related to cell proliferation and cell death, as well as steroid receptors, was undertaken, and apoptosis was determined using TUNEL analysis.

RESULTS

Immunohistochemical analysis of Ki67 expression showed significantly higher expression in the glandular epithelium of ovulatory women compared with the other groups. Glandular oestrogen receptor α expression was significantly lower in rFSH-treated women compared with ovulatory women. The number of apoptotic cells, Bax expression and progesterone receptor expression were similar in all groups. In contrast, Bcl-2 expression was significantly lower in the glandular epithelium of rFSH-treated women.

CONCLUSIONS

In infertile women with hypothalamic-pituitary dysfunction, treatment with ovulation-inducing agents modifies the expression of proteins involved in cell proliferation and death, as well as the expression of steroid hormone receptors in the endometrium. These differences may help to explain, at the molecular level, the functionality of the endometrium during the implantation window, and may help to optimize pregnancy rates obtained with these treatments.

Human conditions of insulin-like growth factor-I (IGF-I) deficiency

Insulin-like growth factor I (IGF-I) is a polypeptide hormone produced mainly by the liver in response to the endocrine GH stimulus, but it is also secreted by multiple tissues for autocrine/paracrine purposes. IGF-I is partly responsible for systemic GH activities although it possesses a wide number of own properties (anabolic, antioxidant, anti-inflammatory and cytoprotective actions). IGF-I is a closely regulated hormone. Consequently, its logical therapeutical applications seems to be limited to restore physiological circulating levels in order to recover the clinical consequences of IGF-I deficiency, conditions where, despite continuous discrepancies, IGF-I treatment has never been related to oncogenesis. Currently the best characterized conditions of IGF-I deficiency are Laron Syndrome, in children; liver cirrhosis, in adults; aging including age-related-cardiovascular and neurological diseases; and more recently, intrauterine growth restriction. The aim of this review is to summarize the increasing list of roles of IGF-I, both in physiological and pathological conditions, underlying that its potential therapeutical options seem to be limited to those proven states of local or systemic IGF-I deficiency as a replacement treatment, rather than increasing its level upper the normal range.

Comparative developmental biology of the uterus: insights into mechanisms and developmental disruption

The uterus is an essential organ for reproduction in mammals that derives from the Müllerian duct. Despite the importance of the uterus for the fertility and health of women and their offspring, relatively little is known about the hormonal, cellular and molecular mechanisms that regulate development of the Müllerian duct and uterus. This review aims to summarize the hormonal, cellular and molecular mechanisms and pathways governing development of the Müllerian duct and uterus as well as highlight developmental programming effects of endocrine disruptor compounds. Organogenesis, morphogenesis, and functional differentiation of the uterus are complex, multifactorial processes. Disruption of uterine development in the fetus and neonate by genetic defects and exposure to endocrine disruptor compounds can cause infertility and cancer in the adult and their offspring via developmental programming. Clear conservation of some factors and pathways are observed between species; therefore, comparative biology is useful to identify candidate genes and pathways underlying congenital abnormalities in humans.

Discovery of candidate genes and pathways in the endometrium regulating ovine blastocyst growth and conceptus elongation

Establishment of pregnancy in ruminants requires blastocyst growth to form an elongated conceptus that produces interferon tau, the pregnancy recognition signal, and initiates implantation. Blastocyst growth and development requires secretions from the uterine endometrium. An early increase in circulating concentrations of progesterone (P4) stimulates blastocyst growth and elongation in ruminants. This study utilized sheep as a model to identify candidate genes and regulatory networks in the endometrium that govern preimplantation blastocyst growth and development. Ewes were treated daily with either P4 or corn oil vehicle from day 1.5 after mating to either day 9 or day 12 of pregnancy when endometrium was obtained by hysterectomy. Microarray analyses revealed many differentially expressed genes in the endometria affected by day of pregnancy and early P4 treatment. In situ hybridization analyses revealed that many differentially expressed genes were expressed in a cell-specific manner within the endometrium. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to identify functional groups of genes and biological processes in the endometrium that are associated with growth and development of preimplantation blastocysts. Notably, biological processes affected by day of pregnancy and/or early P4 treatment included lipid biosynthesis and metabolism, angiogenesis, transport, extracellular space, defense and inflammatory response, proteolysis, amino acid transport and metabolism, and hormone metabolism. This transcriptomic data provides novel insights into the biology of endometrial function and preimplantation blastocyst growth and development in sheep.

Insulin-like growth factor binding protein-1 in the ruminant uterus: potential endometrial marker and regulator of conceptus elongation

Establishment of pregnancy in ruminants requires conceptus elongation and production of interferon-tau (IFNT), the pregnancy recognition signal that maintains ovarian progesterone (P4) production. These studies determined temporal and spatial alterations in IGF binding protein (IGFBP)-1 and IGFBP3 in the ovine and bovine uterus; effects of P4 and IFNT on their expression in the ovine uterus; and effects of IGFBP1 on ovine trophectoderm cell proliferation, migration, and attachment. IGFBP1 and IGFBP3 were studied because they are the only IGFBPs specifically expressed by the endometrial luminal epithelia in sheep. In sheep, IGFBP1 and IGFBP3 expression was coordinate with the period of conceptus elongation, whereas only IGFBP1 expression was coordinate with conceptus elongation in cattle. IGFBP1 mRNA in the ovine endometria was between 5- and 29-fold more abundant between d 12 and 16 of pregnancy compared with the estrous cycle and greater on d 16 of pregnancy than nonpregnancy in the bovine uterus. In sheep, P4 induced and IFNT stimulated expression of IGFBP1 but not IGFBP3; however, the effect of IFNT did not mimic the abundant increase observed in pregnant ewes. Therefore, IGFBP1 expression in the endometrium is regulated by another factor from the conceptus. IGFBP1 did not affect the proliferation of ovine trophectoderm cells in vitro but did stimulate their migration and mediate their attachment. These studies reveal that IGFBP1 is a common endometrial marker of conceptus elongation in sheep and cattle and most likely regulates conceptus elongation by stimulating migration and attachment of the trophectoderm.

Progesterone regulates FGF10, MET, IGFBP1, and IGFBP3 in the endometrium of the ovine uterus

Progesterone (P4) is unequivocally required to maintain a uterine environment conducive to pregnancy. This study investigated the effects of P4 treatment on expression of selected growth factors (fibroblast growth factor 7 [FGF7], FGF10, hepatocyte growth factor [HGF], and insulin-like growth factors [IGF1 and IGF2]), their receptors (MET, FGFR2(IIIB), and IGF1R), and IGF binding proteins (IGFBPs) in the ovine uterus. Ewes received daily injections of corn oil vehicle (CO) or 25 mg of P4 in vehicle from 36 h after mating (Day 0) to hysterectomy on Day 9 or Day 12. Another group received P4 to Day 8 and 75 mg of mifepristone (RU486, a P4 receptor antagonist) from Day 8 through Day 12. Endometrial FGF10 mRNA levels increased between Day 9 and Day 12 and in response to P4 on Day 9 in CO-treated ewes, which had larger blastocysts, and were substantially reduced in P4+RU486-treated ewes, which had no blastocysts on Day 12. Endometrial FGF7 or HGF mRNA levels were not affected by day or reduced by RU486 treatment, but MET mRNA levels were higher in P4-treated ewes on Day 9 and Day 12. Levels of IGF1, IGF2, and IGF1R mRNA in the endometria were not affected by early P4 treatment. Although stromal IGFBPs were unaffected by P4, levels of IGFBP1 and IGFBP3 mRNA in uterine luminal epithelia were increased substantially between Day 9 and Day 12 of pregnancy in CO-treated ewes and on Day 9 in early P4-treated ewes. Therefore, FGF10, MET, IGFBP1, and IGFBP3 are P4-regulated factors within the endometrium of the ovine uterus that have potential effects on endometrial function and peri-implantation blastocyst growth and development.

Comparative developmental biology of the mammalian uterus

The uterus is an essential organ for reproduction in mammals. Despite the importance of the uterus for the fertility and health of women and their offspring, relatively little is known about the hormonal, cellular, and molecular mechanisms that regulate development of the uterus in either the fetus or neonate. Disruption of uterine development in the fetus and neonate by genetic defects or exposure to endocrine disruptors can program the function of the uterus in the adult and lead to infertility, cancer, and even death. The intent of this chapter is to review the current knowledge of regulatory factors and pathways governing prenatal organogenesis and postnatal morphogenesis of the uterus in mammals, with a particular focus on laboratory and domestic animals. Prenatal organogenesis, postnatal morphogenesis, and adult functional differentiation of the uterus are complex, multifactorial processes. Although conservation of some factors and pathways are observed between species, it is clear that mutation of candidate genes in the mouse does not always recapitulate the same defects observed in the human. Therefore, comparative biology of the mechanisms regulating uterine development in other species may be useful to identify candidate genes and pathways to understand congenital abnormalities in humans. This knowledge is necessary to develop rational therapies to prevent and treat infertility and to enhance fertility in humans and domestic animals.

Involvement of growth factors in induction of persistent proliferation of vaginal epithelium of mice exposed neonatally to diethylstilbestrol

Neonatal treatment of female mice with natural and synthetic estrogens including diethylstilbestrol (DES) results in persistent proliferation and cornification of vaginal epithelium. In order to study the mechanism of persistent proliferation of vaginal epithelium, histological and biochemical changes were examined in the vagina of C57BL female mice exposed neonatally to 3 microg DES for 5 days. In intact control adult mice, ovariectomy induced apoptotic cell death in vaginal epithelial cells detected by in situ 3'-DNA nick end labeling method accompanied by low DNA synthesis detected by incorporation of bromodeoxyuridine. In neonatally DES-exposed adult mice, however, ovariectomy did not induce reduction of DNA synthesis and showed only a slight increase in apoptotic cells of vaginal epithelium. In neonatally DES-exposed mouse vagina, semi-quantitative reverse transcription polymerase chain reaction revealed a continuous higher expression of mRNAs encoding epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha). These results indicate that neonatal DES exposure causes the increase in expression of EGF and TGF-alpha mRNA, possibly resulting in the induction of persistent proliferation and cornification of vaginal epithelium in mice.

Pathophysiology of preeclampsia: links with implantation disorders

The phenomenon of implantation anchors the embryo into the uterine wall and produces a hemochorial placenta that maintains the pregnancy and fetal growth. Implantation and placentation are intimately linked and cannot be dissociated either in time or in space. Preeclampsia is characterized by hypertension and proteinuria. It is secondary to an anomaly of the invasion of the uterine spiral arteries by extra-villous cytotrophoblast cells, associated with local disruptions of vascular tone, of immunological balance and inflammatory status, and sometimes with genetic predispositions. Preeclampsia is a disease of early pregnancy, a form of incomplete spontaneous abortion, but is expressed late in pregnancy. Aspirin may play a favorable role in implantation which is related to the genesis of preeclampsia and some cases of intra-uterine growth restriction. The most important points in obtaining a preventive effect from low-dose aspirin during the pregnancy are early treatment (before 13 weeks of gestation) and the prescription of a sufficient dose (more than 100 mg per day).

Developmental biology of uterine glands

All mammalian uteri contain endometrial glands that synthesize or transport and secrete substances essential for survival and development of the conceptus (embryo/fetus and associated extraembryonic membranes). In rodents, uterine secretory products of the endometrial glands are unequivocally required for establishment of uterine receptivity and conceptus implantation. Analyses of the ovine uterine gland knockout model support a primary role for endometrial glands and, by default, their secretions in peri-implantation conceptus survival and development. Uterine adenogenesis is the process whereby endometrial glands develop. In humans, this process begins in the fetus, continues postnatally, and is completed during puberty. In contrast, endometrial adenogenesis is primarily a postnatal event in sheep, pigs, and rodents. Typically, endometrial adenogenesis involves differentiation and budding of glandular epithelium from luminal epithelium, followed by invagination and extensive tubular coiling and branching morphogenesis throughout the uterine stroma to the myometrium. This process requires site-specific alterations in cell proliferation and extracellular matrix (ECM) remodeling as well as paracrine cell-cell and cell-ECM interactions that support the actions of specific hormones and growth factors. Studies of uterine development in neonatal ungulates implicate prolactin, estradiol-17 beta, and their receptors in mechanisms regulating endometrial adenogenesis. These same hormones appear to regulate endometrial gland morphogenesis in menstruating primates and humans during reconstruction of the functionalis from the basalis endometrium after menses. In sheep and pigs, extensive endometrial gland hyperplasia and hypertrophy occur during gestation, presumably to provide increasing histotrophic support for conceptus growth and development. In the rabbit, sheep, and pig, a servomechanism is proposed to regulate endometrial gland development and differentiated function during pregnancy that involves sequential actions of ovarian steroid hormones, pregnancy recognition signals, and lactogenic hormones from the pituitary or placenta. That disruption of uterine development during critical organizational periods can alter the functional capacity and embryotrophic potential of the adult uterus reinforces the importance of understanding the developmental biology of uterine glands. Unexplained high rates of peri-implantation embryonic loss in humans and livestock may reflect defects in endometrial gland morphogenesis due to genetic errors, epigenetic influences of endocrine disruptors, and pathological lesions.

Identification of a novel platelet-derived growth factor-like gene, fallotein, in the human reproductive tract

We isolated the cDNA of a novel platelet-derived growth factor-like gene from human endometrium. The gene was named fallotein; it was 3007 bases in length, and encoded a protein of 345 amino acids. Antiserum against the fallotein protein can recognize a specific protein in the fallopian tube, with a molecular size in accordance with the anticipated size of fallotein. Fallotein mRNA is expressed in two molecular sizes, 3.8 and 2.9 kb, with the former being more abundant. High expression of the gene was found in the prostate, testis, and uterus. A weaker expression signal was found in the spleen, thymus, and small intestine, but expression of fallotein in the colon and peripheral blood leukocytes was negligible.

Horse conceptuses secrete insulin-like growth factor-binding protein 3

Insulin-like growth factor-I (IGF-I) promotes early embryonic development in several species. In the rabbit, IGF-I binds to the embryonic coats from Day 3 of development onward by a 38-kDa protein that is probably insulin-like growth factor-binding protein 3 (IGFBP3). In the present study, ligand, Western, and Northern blot analyses were used to demonstrate the presence of IGF-I-binding activity, several immunoreactive IGFBP3 proteins, and IGFBP3 mRNA in horse conceptuses with particularly large amounts of immunoreactive IGFBP3 in the conceptus capsule. In addition, immunoprecipitation of radiolabeled proteins showed that cultured horse conceptuses secreted IGFBP3 into the culture medium. Endometrial samples from mares also contained IGFBP3 mRNA and protein; but there was no evidence of secretion of IGFBP3 into the uterine lumen by ligand blot analysis, and there was evidence of only very small amounts by Western blot analysis. These results indicate that the horse conceptus secretes significant quantities of IGFBP3 toward the conceptus capsule from as early as Day 10 after ovulation. Thus, most of the IGFBP3 contained within the capsule, which binds IGF-I to this special extracellular matrix of the preimplantation horse conceptus, is likely to be embryonic in origin. IGFBP3 in the horse conceptus capsule may enhance or modulate the action of IGFs on the developing conceptus.

Tissue-specific expression of messenger ribonucleic acids for insulin-like growth factors and insulin-like growth factor-binding proteins during perinatal development of the rat uterus

Insulin-like growth factor (IGF)-I and IGF-II play a number of important roles in growth and differentiation, and IGF-binding proteins (IGFBPs) modulate IGF biological activity. IGF-I has been shown previously to be essential for normal uterine development. Therefore, we used in situ hybridization assays to characterize the unique tissue- and developmental stage-specific pattern of expression for each IGF and IGFBP gene in the rat uterus during perinatal development (gestational day [GD]-20 to postnatal day [PND]-24). IGF-I and IGFBP-1 mRNAs were expressed in all uterine tissues throughout this period. IGFBP-3 mRNA was not detectable at GD-20 but became detectable beginning at PND-5, and the signal intensity appeared to increase during stromal and muscle development. IGFBP-4 mRNA was abundant throughout perinatal development in the myometrium and in the stroma, particularly near the luminal epithelium. IGFBP-5 mRNA was abundantly expressed in myometrium throughout perinatal development. IGFBP-6 mRNA was detected throughout perinatal development in both the stroma and myometrium in a diffuse expression pattern. IGF-II and IGFBP-2 mRNAs were not detected in perinatal uteri. Our results suggest that coordinated temporal and spatial expression of IGF-I and its binding proteins (IGFBP-1,-3,-4,-5, and -6) could play important roles in perinatal rodent uterine development.

Cytokines in implantation

Implantation is a complex process which involves the 'invasion' of the maternal endometrium by the trophoblast surrounding the developing blastocyst. In response to this interaction there is a cellular reaction within the endometrium which has some features analogous to invasion by a tumour and some which are more characteristic of an inflammatory response. In addition, and also in common with cancer and inflammation, there is a release of biologically active molecules, including cytokines, at and around the implantation site. The information on cytokines is complex and often contradictory but it is recognised that they play an important role in the successful establishment of pregnancy. The evidence for this role is examined in this review.

Ovarian follicular dynamics: from basic science to clinical practice

The management of low responders (LR) to ovarian stimulation in cycles of assisted reproduction (AR) is a difficult challenge. Aging of the ovary and LR are coincidental in many situations, but LR is also present in young patients undergoing AR. In fact, today it is a recognized cause of infertility. When the aged ovary is considered, there is evidence that the functioning of the granulosa cells as well as the quality of the oocytes and resulting embryos are affected. Similarly, in young LR, the production of inhibin is affected. However, there is no evidence that the quality of the oocyte and/or the resulting embryo is affected. In this study, we have retrospectively analyzed our files and observed that the quality of the oocytes and embryos was similar between younger and older LR and normal responders (NR). Studies using color Doppler vaginal ultrasound have shown that the pulsatility index (PI) and the resistance index (RI) were increased in LR as compared with NR, suggesting that there was some degree of vascular resistance to flow. Treatment of LR is also a difficult challenge. Ovum donation is a successful treatment for LR, since cumulative birth rates are > 85% with four attempts of embryo transfer. The future may be promising for LR once new technologies are introduced into clinical practice. The use of recombinant gonadotropins and genetically engineered human gonadotropin derivatives may be of considerable help for LR. Similarly, non-gonadotropin hormones, such as cytokines or growth factors, may be shown to play a role in the stimulation of the ovary in the near future, and may therefore open new frontiers for treatment of LR.

Leukodystrophy in patients with ovarian dysgenesis

We describe clinical, biochemical, pathological, and spectroscopic findings in 4 women, aged 15 to 29 years, from three unrelated families who had a unique combination of a central nervous system white matter disease and primary ovarian failure. All had normal initial development but 3 had borderline low IQ and academic difficulties in primary school. Puberty did not develop in 2 patients and was arrested in a third patient. The fourth patient had premature ovarian failure at the age of 13 years. Head magnetic resonance imaging showed diffuse white matter disease, with frontal cortical atrophy in the most clinically advanced patient. All patients had normal karyotype and normal findings on extensive evaluations for known leukodystrophies, for other metabolic diseases, and for causes of ovarian failure. Proton magnetic resonance spectroscopic imaging showed reduction of choline-containing compounds in the affected white matter in all patients and reduction of N-acetylaspartate in the unaffected frontal white matter of 2 patients. All patients had evidence of primary gonadal insufficiency with a normal hypothalamic-hypophyseal axis. Pathological analysis showed streak ovaries in 1 patient and signs of hypomyelination, and gliosis on brain biopsy in another patient. In conclusion, we present a novel group of patients who have in common leukodystrophy, primary ovarian dysfunction, and magnetic resonance spectroscopic abnormalities.

Insulin-like growth factor-I in the porcine endometrium and placenta: localization and concentration in relation to steroid influence during early pregnancy

To initiate the establishment of an epitheliochorial placenta, the developing porcine conceptuses contact the maternal endometrium on its mesometrial side. The porcine conceptuses secrete estrogens which, together with circulating maternal hormones, govern variations in the structure as well as expression and levels of steroid receptors and growth factors during early pregnancy. Mesometrial samples of endometrium or placenta were collected from 15 early pregnant (8-30 days after the onset of estrus) and six cycling (days 1-14) gilts. The variations in tissue morphology and immunohistochemical localization of insulin-like growth factor-I (IGF-I) were related to the tissue levels (by enzyme immunoassay) of receptors for estrogen (ER) and progesterone (PR), as well as mRNA (by solution hybridization) concentrations for the two receptors and IGF-I. IGF-I immunoreactivity was present in samples from all animals, being principally located in maternal epithelium, trophoblast, endothelium and vascular smooth muscle; the latter showing the strongest labeling. The levels of receptor proteins, as well as mRNAs, were highest in the non-pregnant animals at estrus and metestrus. The pregnant animals showed decreasing concentrations to consistently low levels after day 14. Temporal changes in the studied parameters were clearly coincidental with the peak (days 13-14) in conceptus estrogen secretion, e.g. the more uniform IGF-I immunolabeling in the uterine glands (days 8-13) compared with the later stages studied; the conspicuous accumulation and release of secretory vesicles in the endometrial glands (days 8-13), marking the change in secretory quality and quantity, leading to a gradual shift from histotrophic to hemotrophic nutrition of the conceptuses, and finally, the peaking level of IGF-I mRNA in the pregnant endometrium (days 12-13) which decreased considerably thereafter. It is concluded that IGF-I activity in the porcine uterus changes with the early development of the placenta.