Expression of insulin-like growth factor-I and insulin-like growth factor-binding protein-1 in the rat uterus during decidualization

Effect of longevity genetic variants on the molecular aging rate

We conducted a genome-wide association study of 1320 centenarians from the New England Centenarian Study (median age = 104 years) and 2899 unrelated controls using >9 M genetic variants imputed to the HRC panel of ~65,000 haplotypes. The genetic variants with the most significant associations were correlated to 4131 proteins that were profiled in the serum of a subset of 224 study participants using a SOMAscan array. The genetic associations were replicated in a genome-wide association study of 480 centenarians and ~800 controls of Ashkenazi Jewish descent. The proteomic associations were replicated in a proteomic scan of approximately 1000 Ashkenazi Jewish participants from a third cohort. The analysis replicated a protein signature associated with APOE genotypes and confirmed strong overexpression of BIRC2 (p < 5E-16) and under-expression of APOB in carriers of the APOE2 allele (p < 0.05). The analysis also discovered and replicated associations between longevity variants and slower changes of protein biomarkers of aging, including a novel protein signature of rs2184061 (CDKN2A/CDKN2B in chromosome 9) that suggests a genetic regulation of GDF15. The analyses showed that longevity variants correlate with proteome signatures that could be manipulated to discover healthy-aging targets.

A clinical and basic study of optimal endometrial preparation protocols for patients with infertility undergoing frozen-thawed embryo transfer

The optimal protocol for endometrial preparation in patients with infertility remains unclear. Due to this, the current study retrospectively analyzed 1,589 patients with infertility and regular menstrual cycles to assess reproductive outcomes per embryo transferred and per embryo transfer (ET) cycle following the transfer of frozen-thawed embryos (FET) in a modified natural cycle (mNC) or hormone therapy cycle (HT) with or without gonadotropin-releasing hormone agonist (GnRHa)-induced pituitary suppression. The molecular mechanisms involved were also studied using tissues from endometrial biopsies. Patients who underwent FET were assigned to 5 groups as follows: Group A underwent a mNC (n=276); group B (n=338) received estradiol (E2) and progesterone (P4); group C received 1 cycle of GnRHa, E2 and P4 (n=323); group D received 2 cycles of GnRHa, E2 and P4 (n=329); and group E received 3 cycles of GnRHa, E2 and P4 (n=323). Tissues from endometrial biopsies of 91 patients performed on the day of ET were tested for endometrial receptivity marker mRNA expression and microRNA (miR)-223-3p mRNA. Furthermore, endometrial stromal cells (ESCs) were used for an in-depth study of the molecular mechanisms involved. Among the 5 groups of patients, implantation rates, clinical pregnancy rates and live birth rates were not significantly different. However, endometrial receptivity was enhanced in group E when compared with groups A-D, which was associated with endometrial leukemia inhibitory factor (LIF), osteopontin, vascular endothelial growth factor, integrin β3 and homeobox gene 10 and 11 mRNA upregulation, and miR-223-3p miRNA downregulation. Transfection of ESCs with an miR-223-3p mimic significantly reduced levels of LIF mRNA and protein. In addition, pre-treating ESCs with GnRHa upregulated mRNA and protein expression of the decidualization markers prolactin and insulin-like growth factor binding protein-1 in a time-dependent manner. In conclusion, these results indicated that HT with GnRHa may be a potential endometrial preparation protocol for FET.

TGFβ superfamily signaling and uterine decidualization

Decidualization is an intricate biological process where extensive morphological, functional, and genetic changes take place in endometrial stromal cells to support the development of an implanting blastocyst. Deficiencies in decidualization are associated with pregnancy complications and reproductive diseases. Decidualization is coordinately regulated by steroid hormones, growth factors, and molecular and epigenetic mechanisms. Transforming growth factor β (TGFβ) superfamily signaling regulates multifaceted reproductive processes. However, the role of TGFβ signaling in uterine decidualization is poorly understood. Recent studies using the Cre-LoxP strategy have shed new light on the critical role of TGFβ signaling machinery in uterine decidualization. Herein, we focus on reviewing exciting findings from studies using both mouse genetics and in vitro cultured human endometrial stromal cells. We also delve into emerging mechanisms that underlie decidualization, such as non-coding RNAs and epigenetic modifications. We envision that future studies aimed at defining the interrelationship among TGFβ signaling circuitries and their potential interactions with epigenetic modifications/non-coding RNAs during uterine decidualization will open new avenues to treat pregnancy complications associated with decidualization deficiencies.

Development of an in vitro model to study uterine functions and early implantation using rat uterine explants

This study was conducted to develop an in vitro model using rat uterine explants to explore complex uterine functions. Rat uterine explants (1-2 mm) were isolated, cultured and further characterized. Steroid hormone treatment of cultured explants showed that both Muc1 and Pr were significantly up-regulated (P < 0.05) by E2. Areg was significantly up-regulated (P < 0.05) by P4 and Igfbp1 was significantly up-regulated (P < 0.05) by the combination of E2 and P4, although, in rat, Igfbp1 is E2-dependent. In vitro decidualization of cultured explants was induced and two potential markers of decidualization, Prl8a2 and Bmp2, were examined. Real-time quantitative PCR data revealed that both Prl8a2 and Bmp2 were significantly up-regulated (P < 0.05) in MPA- and db-cAMP-treated explants compared to the control group of explants. Then, an individual hatched blastocyst and cultured explant was placed in a 96-well (round-bottom U-shaped) plate. Co-culture results showed that stable attachments were observed after 48 h, where embryos were stably attached to the explants and could not be dislodged after mild shaking and/or pipetting. The rates of attachment of embryos to the explants were increased significantly in the P4-treated group (63.6%) compared to the control group (35.5%), after steroid hormone treatment. The rates of attachment were reduced significantly in the E2-treated group (0.0%), where no stable attachments were observed. Despite the necessity of comprehensive investigation, our results suggest that the cultured rat uterine explants can be a useful in vitro model to study uterine functions and early implantation.

Murine uterine decidualization is a novel function of autoimmune regulator-beyond immune tolerance

PROBLEM

Autoimmune polyendocrinopathy, candidiasis, and ectodermal dystrophy (APECED, APS-1) patients characterized by Aire (autoimmune regulator) mutations and Aire homozygous knockouts (Aire(-/-) ) exhibit infertility. It is not clear as to what contributes to infertility in the above.

METHOD OF STUDY

This study investigates the expression of "AIRE in the uterus" and its contribution to early pregnancy of mice by using quantitative real-time PCR analysis, immunohistochemistry, Western blotting, and in vivo Aire silencing experiments.

RESULTS

Aire (Isoform 1a) is expressed in the uterus during the "window of implantation" and decidualization. In vivo Aire silencing interfered with formation of implantation sites and stromal cell transformation by regulating bone morphogenetic protein-2,4 (Bmp2, Bmp4), homeobox A10 (Hoxa10), and insulin-like growth factor-binding protein 1(Igfbp1) leading to pregnancy failure.

CONCLUSION

Our consolidated results on extrathymic uterine expression of AIRE during early pregnancy and decidualization and impaired fertility on in vivo silencing are suggestive of its importance in pregnancy via a role beyond immune tolerance.

MAP kinases and the inflammatory signaling cascade as targets for the treatment of endometriosis?

INTRODUCTION

The pathogenesis of endometriosis, a common benign disease, remains ill-defined, although it is clear that chronic inflammation plays a crucial role through mitogen-activated protein kinase (MAPK) signaling pathways. All current medical therapies for endometriosis are antigonadotropic, and therefore have a contraceptive effect. A concerted research effort is hence warranted with the aim of delivering novel therapeutics that reduces disease symptoms without blocking ovulation.

AREAS COVERED

The authors review the complex pathogenic mechanisms of chronic inflammation in endometriosis and their relationships with MAPK pathways. The authors conducted a literature search of descriptive and functional targeted validation of MAPK in the pathogenesis of endometriosis. The effects of MAPK inhibitors, which constitute potential agents for future treatments, are also described.

EXPERT OPINION

Preliminary studies have highlighted a crucial role for MAPK in driving endometriosis-related inflammation. MAPK inhibitors exhibit potent activity in terms of controlling growth of endometriosis lesions both in vitro and in animal models. As MAPK inhibitors are known to have a multitude of undesirable side effects, their use in humans has to be approached with great care. Indeed, use of these drugs would probably be limited to short exposures prior to surgery in cases involving the most severe disease phenotypes.

Prostaglandin E2: the master of endometriosis?

Endometriosis is the primary cause of infertility in women, with a prevalence rate ranging from 5% to 10%. Women with endometriosis suffer from symptoms such as chronic pelvic pain, dysmenorrhea and dyspareunia, which significantly reduce the quality of life. Endometriosis is a polygenic disease with a complex, multifactorial etiology. The mechanism responsible for the initiation and development of this disease remains largely unknown. Prostaglandin E2 (PGE2), a versatile eicosanoid that exerts numerous physiological and pathological functions, has been implicated to play critical roles in the development of endometriosis. A growing body of evidence demonstrates that PGE2 regulates many pathophysiological processes including cell proliferation, antiapoptosis, immune suppression and angiogenesis during the development of endometriosis. This review focuses on recent advances in cellular and molecular mechanisms triggered by PGE2 that contribute to the pathological processes of endometriosis.

Expression pattern of integrins and their ligands in mouse feto-maternal tissues during pregnancy

The role of integrins, the cell-surface glycoproteins involved in various cellular functions, is well documented. However, information about their role and expression profile during pregnancy is still scant. In the present study, the expression of the integrin subunits β3, α6 and α5, along with their ligands vitronectin, osteopontin, laminin and fibronectin, was investigated in mouse uterus during different stages of pregnancy, namely 6.5, 8.5 and 13.5 days post coitus (d.p.c.) by immunohistochemical localisation. Integrins β3, α6 and α5 and the extracellular matrix molecules vitronectin and osteopontin exhibited dynamic spatiotemporal changes in their expression pattern in gestational endometrium, whereas fibronectin and laminin demonstrated more-or-less ubiquitous expression. The inter-implantation sites showed localisation of most of these molecules predominantly in the luminal epithelium, whereas their expression was negligible in the stroma. The present study explores the possible role and relevance of the spatiotemporal expression of integrins and their ligands in endometrial/decidual function and the maintenance of pregnancy.

Insulin-like growth factors and their binding proteins define specific phases of myometrial differentiation during pregnancy in the rat

While the insulin-like growth factor (IGF) system is known to regulate uterine function during the estrous cycle, there are limited data on its role in myometrial growth and development during pregnancy. To address this issue, we defined the expression of the Igf hormones (1 and 2), their binding proteins (Igfbp 1-6), and Igf1r receptor genes in pregnant, laboring, and postpartum rat myometrium by real-time PCR. IGF family genes were differentially expressed throughout gestation. Igf1 and Igfbp1 mRNA levels were upregulated during proliferative phase (Days 6-12) of rat gestation. Igfbp3 gene expression also was elevated in proliferating smooth muscle cells (SMCs) and was highest at the time of transition between proliferative and synthetic phases (Days 12-15). Igfbp6 gene expression profile paralleled plasma progesterone (P4) concentrations, peaking during the synthetic phase (Days 17-19) and decreasing thereafter. Administration of P4 at late pregnancy (starting from Day 20) to maintain elevated plasma P4 concentrations blocked the onset of labor and prevented the fall in Igfbp6 mRNA levels. In contrast, the treatment of pregnant rats with the P4 receptor antagonist RU486 on Day 19 induced preterm labor and the premature decrease of Igfbp6 gene expression. Igfbp2 gene expression was transiently upregulated during the contractile phase of gestation (Days 21-23) solely in the gravid horn of unilaterally pregnant rats, but it was not affected in P4- or RU486-treated animals, supporting a role for mechanical stretch imposed by the growing fetuses. Igfbp5 gene was induced during postpartum involution. Our results suggest the importance of the IGF system in phenotypic and functional changes of myometrial SMCs throughout gestation in preparation for labor.

Prostaglandin E2 induces fibroblast growth factor 9 via EP3-dependent protein kinase Cdelta and Elk-1 signaling

Fibroblast growth factor 9 (FGF-9) is a potent mitogen that controls the proper development of many tissues and organs. In contrast, aberrant expression of FGF-9 also results in the evolution of many human diseases, such as cancers and endometriosis. Despite its vital function being reported, the cellular and molecular mechanisms responsible for the regulation of FGF-9 expression are mostly unknown. We report here that prostaglandin E2 (PGE2) induces expression of FGF-9, which promotes endometriotic stromal cell proliferation, through the EP3 receptor-activated protein kinase Cdelta (PKCdelta) signaling pathway. Activation of PKCdelta leads to phosphorylation of ERK1/2, and the transcription factor Elk-1 thereby promotes transcription of FGF-9. Two Elk-1 cis-binding sites located at nucleotides -1324 to -1329 and -1046 to -1051 of the human FGF-9 promoter are identified as crucial for mediating PGE2 actions. Collectively, we demonstrate, for the first time, that PGE2 can directly induce FGF-9 expression via a novel signaling pathway involving EP3, PKCdelta, and a member of the ETS domain-containing transcription factor superfamily in primary human endometriotic stromal cells. Our findings may also provide a molecular framework for considering roles for PGE2 in FGF-9-related embryonic development and/or human diseases.

Comparative Biology of the IGF System in Endometrium, Decidua, and Placenta, and Clinical Implications for Foetal Growth and Implantation Disorders

The insulin like growth factors and their binding proteins appear to play a central role during implantation and establishment of pregnancy in all species studied. Although there are similarities among species in the cell types that express IGFs and IGFBPs and their regulation during implantation and pregnancy, there are also significant differences. Understanding of the role of the IGF system in placental function in the human is of immense clinical importance, because serious complications of pregnancy such as intrauterine growth restriction and pre-eclampsia are thought to be associated with alterations in IGF system during early pregnancy and later in gestation. Research in laboratory and domestic animals, including transgenic and gene targeting studies in mice, has significantly improved our understanding of the role of IGF system in placental and foetal development. This paper reviews the diversity in the expression and regulation of IGF system in the decidua and placenta at the foetal-maternal interface in the human and different animal species, which may benefit in directing future studies in understanding of various complications of human pregnancy.

Life Cycle of Decidual Cells

The decisive events in the development of decidual cells (DC) are presented through examples of human and rodent decidua. Human decidua is formed by large decidual cells (LDC), endometrial granulated cells (eGC), and small decidual cells. The LDC form the main type of decidual membranes, which determine the morphological characteristics of the decidua as a tissue. Immediate precursor cells of LDC are located below the basement membrane of the uterine epithelium before and during implantation. At the next stage of differentiation, LDC acquire a spindle-like shape. Rodent LDC form an epithelium-like structure with gland properties at the terminal stage of differentiation. The single-cell structure of human decidua is a derivative of the epithelial organization of rodent decidua. Spindle-like rat LDC are characterized by a high level of protein, RNA, and DNA synthesis and by intensive proliferation. At the beginning of pregnancy, a cell proliferation predominates over cell loss. By Days 12-13 of rat pregnancy LDC loss reaches 80% per day. Terminally differentiated LDC (tLDC) disappear from decidua due to apoptosis. Apoptosis of tLDC and the exhaustion of their precursors account for the disappearance of LDC in the middle of rat pregnancy. Human term decidua is composed of living cells. Human LDC (hLDC) comprise the largest part of human decidual cells (hLDC). hLDC account for 60-90% of hDC but their relative amount can decrease to 35% in the case of significant cell loss under unfavorable conditions. A decrease of LDC is not accompanied by DC proliferation. The lack of ability of decidua to compensate for DC loss suggests DC is a growing type of cell population without cambial cells. LDC function largely by blebbing and budding. Human and rat endometrial granulated cells (eGC) are characterized by a low level of natural killer (NK) activity and a high level of natural suppressor (NS) activity. The combination of NK and NS properties is characteristic of the eGC immunoregulatory function. Other functions of decidua include control of inflammation and trophoblast growth and expansion in the uterus. The life span of decidual cells is limited by pregnancy.

Possible role for insulin-like growth factor-I in the pathogenesis of cystic endometrial hyperplasia pyometra complex in the bitch

Cystic endometrial hyperplasia (CEH) is an important pathologic condition in the canine uterus and recognized as a common cause of illness and death in this species. The underlying cause and pathogenic mechanism responsible for this condition remains incompletely understood. Aberrant sex steroid hormone receptor expression in the uterus of dogs with CEH has been documented but not explained. In the dog there is an exceptionally high, progestin induced production of insulin-like growth factor-I (IGF-I) which is now generally accepted to be one of the most important growth factors with a high mitogenic effect on the uterus. Therefore, in this study the immunohistochemical staining intensity for IGF-I was compared among the uteri of 25 adult female dogs that had developed CEH and 14 healthy dogs in comparable stages of the estrus cycle. Specific staining for IGF-I was found in the cytoplasm epithelial cells and in smooth muscle cells of endometrium and myometrium. A marked increase in specific staining intensity for IGF-I was found in the surface epithelium, glandular epithelium and in the stroma of the uteri of dogs with CEH. The increase in IGF-I specific staining intensity was most prominent in the superficial endometrial stroma. Based on the known role of IGF-I in endometrial proliferation, it was concluded from the present study that high concentrations of IGF-I located in and around the epithelial cells of the endometrium in dogs with CEH, could play an important role in the development of CEH.

Endometrial mRNA expression of oestrogen receptor alpha, progesterone receptor and insulin-like growth factor-I (IGF-I) throughout the bovine oestrous cycle

This study characterized endometrial expression of mRNAs of oestrogen and progesterone receptors (ER, PR) and insulin-like growth factor-I (IGF-I) during the oestrous cycle. Seven Holstein heifers that showed standing oestrus on the same day (day 0) were selected and blood samples for oestradiol (E2) and progesterone (P4) determinations by RIA were taken daily until day 23. Endometrial samples were taken by transcervical biopsies on days 0, 5, 12 and 19 for mRNA determination by solution hybridization. The highest endometrial mRNA levels of ERalpha and PR were observed at oestrus and a decline was observed already at day 5, which then decreased progressively at the end of the luteal phase. IGF-I mRNA levels were higher at day 0 and 5 than at day 12. At day 19, mRNA levels of ERalpha, PR and IGF-I were the lowest in heifers that were at the end of their luteal phase (n=4), but were high again in heifers which P4 levels were basal (n=3). The temporal changes in mRNA endometrial expression of ERalpha, PR and IGF-I and their relation to the changes in steroid concentrations during the bovine oestrus cycle are described.

Differential expression of insulin-like growth factors in the uterine epithelium and extracellular matrix during early pregnancy

We have studied the simultaneous expression of insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) in the uterine epithelium and extracellular matrix during the time of trophoblast attachment and implantation. These studies reveal that IGF-I and IGF-II display different spatial and temporal patterns of expression during early pregnancy, and suggest a role for them in the process of attachment and implantation. Specifically, IGF-I is strongly expressed in the basal lamina which is the site of trophoblast invasion into the maternal stroma, and also in the apical epithelium, the site of initial trophoblast attachment. IGF-II is expressed to a lesser extent in the basal lamina, lateral plasma membranes and apical epithelium on day 3 but is only prominent apically at the time of implantation, suggesting a role in attachment.

Expression of mRNA encoding insulin-like growth factors I and II by uterine tissues and placenta during pregnancy in the rat

The uterus and the placenta synthesize insulin-like growth factors (IGFs) and insulin-like binding proteins (IGFBPs). These growth factors are implicated in processes of proliferation and differentiation that occur in the uterus. To determine the patterns of expression of IGFs during rat pregnancy we used in situ hybridization with digoxigenin labeled probes on uterus from day 7 to day 16 of pregnancy. In early gestation days (7-8) both IGF mRNAs showed similar tissue distribution with relative abundance in the stroma and circular muscle layer. On days 11 and 12 expression for IGF-I mRNA was found in the mesometrial decidua and metrial gland and in the ectoplacental cone while clear expression of IGF-II mRNA could only be found in the latter. On days 13 and 14, expression for IGF-I mRNA could be detected in the mesometrial decidua and metrial gland but no expression was observed for IGF-II mRNA. A gradient of IGF-I mRNA expression could be observed in the placenta on day 16, with the trophoblastic cells of the basal zone expressing the signal with stronger intensity than in the labyrinthine zone. For IGF-II mRNA the highest expression was associated with the labyrinthine zone. Endovascular trophoblast was positive for both mRNAs. The spatial and temporal patterns of expression suggests a role for IGFs in the process of decidualization as well as in the establishment, growth and differentiation of the various trophoblast cells of the placenta.

Insulin-like growth factors in endometrial function

Growth factors and related peptides are believed to mediate and modulate the actions of hormones at their target tissues through autocrine/paracrine mechanisms. Endometrial stromal cells produce insulin-like growth factors I and II (IGF-I and IGF-II) as well as the high-affinity IGF binding proteins (IGFBPs), whereas epithelial cells and, in a lesser amount, also stromal cells contain cell membrane receptors for IGFs. IGFs have proliferative, differentiative and metabolic effects. Estrogen stimulates IGF-I gene expression in the endometrium, and IGF-I is assumed to mediate estrogen action. IGF-II gene expression is associated with endometrial differentiation. All six high-affinity IGFBPs are expressed in human endometrium, the most abundant being IGFBP-1. This is secreted by predecidualized/decidualized endometrial stromal cells in late secretory phase endometrium and pregnancy decidua, i.e. under the action of progesterone. The primary negative regulator of IGFBP-1 expression is insulin, by inhibiting IGFBP-1 transcription. IGFBP-1 inhibits the receptor binding and biological actions of IGF-I in the endometrium and in cultured human trophoblastic cells. These findings support the view that the IGF system has autocrine and paracrine functions in the regulation of endometrial proliferation and differentiation. After implantation, decidual IGFBP-1 may regulate IGF actions at the embryo-endometrial interface, since trophoblast cells contain IGF receptors and express IGF-II, but do not express IGFBP-1. Clinical conditions that are known to increase the risk of endometrial cancer are all characterized by the absence of IGFBP-1. Thus, like unopposed estrogen, unopposed IGF-I action may also lead to uncontrolled endometrial proliferation and favor the development of endometrial cancer. The measurement of mRNAs encoding the IGF system might provide a novel tool to evaluate the endometrial response to endogenous and exogenous estrogens and progestins at the molecular level.

Characterization of insulin-like growth factor-binding proteins in the uterus and conceptus during early conceptus elongation in cattle

As a first step in determining the role that insulin-like growth factor (IGF)-binding proteins (BPs) may have in regulating initial stages of conceptus elongation in cattle, the type and relative abundance of IGFBPs in serum, uterine tissues, and uterine fluid from pregnant and noninseminated cows on Days 13 and 15 postestrus and in Day 15 conceptuses was evaluated. Uterine and serum samples contained IGFBPs 2, 3, 4, and 5 as determined by immunoprecipitation followed by Western ligand blots of precipitates. Compared with those in uterine and serum samples, IGFBPs in conceptuses and conceptus-conditioned culture media were only faintly detectable. The percentage of the total IGF-I binding activity attributed to IGFBP-3 was greater (p < 0.05) in myometrium, serum, and uterine fluid (> 50%) than in inter- (40%) and intracaruncular (37%) endometrium. Percentage of total binding attributed to IGFBP-2 was greater (p < 0.05) in endometrium and serum ( approximately 30%) than in myometrium (16%) and uterine fluid (9%). Binding activity of certain IGFBPs varied due to day of the estrous cycle or due to pregnancy status. Concentrations of IGF-I in serum were greater (p < 0.05) in nonpregnant (52 +/- 2 ng/ml) than in pregnant (40 +/- 4 ng/ml) cows. Concentration of IGF-I in uterine fluid did not differ due to pregnancy status or stage of cycle (4.4 pg IGF-I/ microg uterine protein). Northern blots revealed mRNAs for IGFBPs 1, 2, 3, 4, and 5 in uterine tissues but not in conceptuses. In situ hybridization indicated that IGFBP-1 mRNA was primarily localized in luminal epithelium of endometrium; IGFBP-2 mRNA was in luminal epithelium and dense stromal cells adjacent to endometrial epithelium; and IGFBP-3 mRNA was in vascular endothelial cells and was more prevalent in myometrium than in endometrium. Tissue specificity and changes in abundance of IGFBPs in the uterus during early conceptus elongation indicate the potential importance of IGFBP regulation of uterine IGFs during this time period.

Immunohistochemical analysis of insulin-like growth factor-binding proteins -1, -2, and -3 in implantation sites of the mouse

PURPOSE

Our purpose was to analyze potential interactions between the embryo and the maternal endometrial interface in vivo by analyzing immunolocalization of insulin-like growth factor-binding proteins (IGFBPs) -1, -2, and -3 in implantation sites of the mouse.

METHODS

Six-week-old B6D2F1 female mice underwent superovulation followed by mating and sacrifice at timed intervals. Formalin-fixed paraffin-embedded tissue was used for avidin-biotin immunocytochemical localization of IGFBPs utilizing standard methodology.

RESULTS

Immunostaining at 1.5 days post coitum revealed light staining in the epithelial glandular cells and faint staining in decidual stroma for both IGFBP-1 and IGFBP-2. At 7.5-10.5 days post coitum, there was moderate-dense immunostaining in the decidualized stromal cells at the implantation site for all three IGFBPs, whereas light immunostaining was seen in nonimplantation site decidua.

CONCLUSIONS

Compartmentalization of immunostaining for IGFBP-1, -2, and -3 within decidualized stroma suggests that these proteins may be regulated by trophoblastic and/or embryonic signals.

The secretion of insulin-like growth factor I, prolactin and insulin-like growth factor binding protein 1 by the decidua as predictors of human fetal growth

To determine if in vitro secretion of the decidual peptides insulin-like growth factor I (IGF-I), prolactin or insulin-like growth factor binding protein 1 (IGFBP-1) correlates with infant birthweight in uncomplicated, term human pregnancies, decidua from 45 pregnancies with normally distributed birthweights was cultured in defined medium for 24 h. IGF-I, prolactin and IGFBP-1 concentrations in the culture medium were measured by radioimmunoassay. Neither infant birthweight nor a normalized measure of infant birthweight (birthweight z-score) correlated with the quantity of IGF-I, prolactin or IGFBP-1 secreted by the decidua from that pregnancy. There were no differences in any of the peptide hormones assayed when the pregnancies were grouped by infant sex. IGF-I and prolactin secretion by individual decidual samples correlated positively. IGF-I and IGFBP-1 secretion also correlated positively in individual samples. A previously identified correlation between decidual IGF-I secretion and infant birthweight among a group of normal and growth restricted (IUGR) pregnancies was not confirmed in the current study. These data indicate that the decrease in decidual IGF-I and prolactin secretion seen in IUGR pregnancies is not the hormone profile of the low birthweight end of a normal population, but a distinct endocrine profile.

Binding of IGF-I to preimplantation rabbit embryos and their coats

It is known that insulin-like growth-factor I (IGF-I) promotes early embryonic development from the morula to the blastocyst stage in rabbits (28). Therefore we used autoradiography to investigate whether IGF-I binds to preimplantation embryos and its coats. From Day 3 after mating onwards, a clear binding of IGF-I to the embryos was observed. There was no difference in binding to the embryoblast or trophoblast cells. Using ligand blot, several IGF-binding proteins (IGFBP; 31 kDa, 33 kDa, 36 kDa, three overlapping bands at 40 to 55 kDa) were obvious in the embryoblast and trophoblast. A 120 to 130 kDa protein was observed exclusively in the embryoblast. Significant binding of (125)I IGF-I to the coats of embryos older than 3 d was detected, and IGF-I was bound via a 38 kDa protein, as detected by ligand blot. To investigate the origin of this protein, the patterns of IGFBP were determined in the oviductal and uterine fluids of pregnant animals (Days 0 to 6). The following binding proteins were observed regularly in the oviductal and uterine flushings: 28 kDa, 32 kDa and 3 overlapping bands in the area of 40 to 55 kDa. In the oviduct the main IGF binding protein was the 32 kDa band (38.7% to 45.9%), while in the uterus it was the 3 overlapping bands at 40 to 55 kDa (42.5% to 24.1%). Because IGF-I is produced in the oviduct and uterus (27), IGFBPs are found in oviductal and uterine fluids, IGF-I is stored in the coats, IGF-I binds to preimplantation embryos and IGF-I promotes early embryonic development (28), the IGF system seams to have a function in the maternal-embryonic interaction.

Insulin-like growth factor binding protein gene expression in the pregnant rat uterus and placenta

While the insulin-like growth factor (IGF) system plays a fundamental role in regulating embryonic and placental growth, the specific contributions of the six IGF binding proteins (IGFBPs 1-6) to these processes are not well understood. We here focus on IGFBP expression in the extraembryonic environment, which both supports and constrains embryonic growth, and have used in situ hybridization to determine sites of IGFBP mRNA synthesis in the pregnant rat uterus and placenta. We find that all IGFBPs are expressed in distinct, changing patterns in the uterine endometrium, at the decidual boundary, in the decidual vasculature, and in the myometrium during pregnancy. Within the endometrium, the most prominent change is that expression of IGFBP-1 begins in some, but not all, endometrial glands prior to implantation and then expands to include all secretory epithelia shortly after implantation. During the period of rapid decidual proliferation that follows implantation, IGFBP-3, -4, and -5 transcripts are all detected in a laminar array at the boundary between the decidua and the nondecidualized endometrium. In the decidual vasculature at Day (d) 8.0, both IGFBP-3 and IGFBP-4 mRNAs are detected in dilating blood vessels, with BP-3 most prominent in the antimesometrial plexus and BP-4 primarily at the mesometrial pole. Later (d11.5), all decidual vessels express high levels of IGFBP-3 and lower levels of IGFBP-4 mRNAs. Finally, changes in expression of several IGFBPs also occur within the myometrium during pregnancy. For example, IGFBP-2 is expressed in the inner circular layer shortly after implantation, and expression increases through late gestation. In contrast, IGFBP-5 hybridization occurs over both myometrial layers before implantation, but decreases in intensity and spatial distribution as pregnancy proceeds. Finally, and most strikingly, IGFBP-6 expression, barely detectable in the d7.0 myometrium, gradually increases until it is very strongly transcribed during the placental stages. Taken together, these observations suggest multiple roles for IGFBPs in supporting implantation, regulating the extent of decidualization, modulating local levels of vascular IGFs, and regulating uterine muscular growth.

Major secretory product of the mesometrial decidua in the rat, a variant of alpha-2-macroglobulin, binds insulin-like growth factor I via a protease-dependent mechanism

Decidualization-associated protein (DAP), the quantitatively major secretory product of the mesometrial decidua in the rat, is a pl variant of the liver-derived acute-phase reactant, alpha-2-macroglobulin (alpha 2M). Alpha 2M, a broad spectrum protease inhibitor, has been demonstrated in the human to bind a variety of cytokines and growth factors. In humans, the quantitatively major secretory product of decidual tissue is an insulin-like growth factor (IGF) binding protein. In this study, we have therefore tested the ability of liver- and decidual-derived alpha 2M in the rat to bind IGF-I. Alpha 2M purified from acute-phase plasma and DAP purified from cytosolic extracts of decidual tissue and medium from tissue incubations both bound radiolabeled IGF-I. The binding of IGF-I was principally dependent upon the coincubation of the protein with a proteinase. Therefore, it occurred during the conversion of the "slow" to the "fast" form of alpha 2M. Pretreatment with proteinase to produce the fast form before addition of the IGF-I reduced the binding. Binding was enhanced at a ratio protein:proteinase of 1:1. Results from gel electrophoretic analysis were consistent with the covalent linkage of IGF-I to alpha 2M during the cleavage of the "bait region." A saturable displacement by increasing concentrations of unlabeled IGF-I suggested high affinity interaction. Under conditions of demonstrated binding to purified proteins binding in acute-phase plasma, decidual tissue extracts and tissue incubation medium were associated with a high molecular weight species which was confirmed to represent alpha 2M and DAP, respectively. Our studies demonstrate that IGF-I may now be added to the list of regulatory peptides which alpha 2M may bind and that, in rat decidua, DAP may represent the functional homolog of decidual IGFBP-1 in the human and regulate growth factor function during placental development.

The role for the uterine insulin-like growth factor I in early embryonic loss after superovulation in the rat

OBJECTIVES

To examine possible roles of the insulin-like growth factor (IGF) system in increased early embryonic loss after superovulation.

DESIGN

Changes in the uterine IGF system were examined in superovulated rats. Insulin-like growth factor I (IGF-I) was infused to the right uterine horns to mimic enhanced IGF-I actions after superovulation. Uterine luminal fluids were collected after IGF-I infusions and embryos were cultured with uterine luminal fluids.

MAIN OUTCOME MEASURES

Steroid hormones, IGF-I, IGF binding protein (IGFBP), and IGF-I receptor levels, developmental rate, and cell numbers of embryos.

RESULTS

Elevated IGF-I levels and suppressed IGFBP levels were found from days 1 to 3 of pregnancy after superovulation. Uterine luminal fluids of the IGF-I infusion and superovulation groups impaired embryo development in vitro. Anti-IGF-I antibody infusions after superovulation reversed detrimental effects of superovulation. Dialysis of uterine luminal fluids of the IGF-I infusion and superovulation groups before culture improved embryo development.

CONCLUSIONS

Enhanced IGF-I actions in the uterus after superovulation may be responsible for the increase of early embryonic loss. The detrimental factor for embryo development seems a small molecule and is likely a local product of the uterus in which IGF-I actions are enhanced.

Production of insulin-like growth factor binding proteins (IGFBPs) by human endometrial stromal cell is stimulated by the presence of embryos

PURPOSE

To identify IGFBPs among endometrial secretory products and study their role in implantation and early embryo development.

METHODS

Two-cell CB6F1 mouse embryos were cultured alone or with human endometrial stromal cells in RPMI 1640 plus 10% fetal calf serum (FCS) with or without addition of IGF-I (20 micrograms/ml), IGF receptor antibody (0.1 microgram/ml), progesterone (P) (20 ng/ml) and relaxin (R) (20 micrograms/ml). On the designated day, the medium was changed to protein-free RPMI and incubated for 16 h. Both conditioned medium and conditioned protein-free medium were then collected for protein analysis and immunoradiometric assay. Cells were fixed with 4% paraformaldehyde for immunohistochemical staining.

RESULTS

IGFBP1 (31 kDa), IGFBP2 (36 kDa), IGFBP3 (45 kDa and 50 kDa) and an unknown IGFBP (25 kDa) were identified in conditioned medium of human endometrial stromal cells cultured alone or cocultured with mouse embryos. Secretion of IGFBPs by endometrial stromal cells was stimulated in the presence of mouse embryos as well as by P and R. IGFBP3 appears to be more responsive to embryonic signals. On the other hand, the secretion of IGFBP1 was greatly stimulated by P and R. Immunolocalization revealed that all three BPs were present in both embryonic and endometrial cells and their immunological staining was heavily increased by P and R.

CONCLUSIONS

Endometrial stromal cells were able to synthesize and secrete IGFBPs to modify IGF action on embryo development. Secretion of IGFBPs was stimulated by embryonic signals and was hormonally dependent. The fact that IGFBP3 was more responsive to embryonic signals suggests that it may be important in early implantation. On the other hand, IGFBP1 production was highly responsive to both P and R, suggesting that it may be important throughout pregnancy. In addition, the fact that IGFBPs were located in endometrial and embryonic cells may suggest that these secretory products have autocrine and/or paracrine effects on both types of cells.

Endometrial secretory proteins enhance early embryo development

PURPOSE

To evaluate the role of endometrial stromal cells and their secretory proteins in early embryo development, two-celled CB6F1 mouse embryos were cultured alone or cocultured with human endometrial stromal cells in various culture conditions.

RESULTS

The percentage of embryo blastocyst formation, hatching, and outgrowth was significantly greater in (1) coculture with endometrial stromal cells than in a cell-free control when both coculture and control were carried out in protein-free medium or in RPMI 1640 plus 10% fetal calf serum; (2) coculture with hormone (i.e., progesterone plus relaxin)-treated cells than in coculture with hormone-nontreated cells; and (3) media supplemented with isolated endometrial secretory proteins than in media supplemented with BSA (0.35%). Embryo development was not found to be significantly different in coculture and in media supplemented with endometrial secretory protein.

CONCLUSION

Our data provides credence to the theory that endometrial stromal cells enhance embryo development by secreting specific proteins that are beneficial to embryo growth in vitro.

Expression of insulin-like growth factors I and II in conceptuses from normal and diabetic mice

Insulin-like growth factors (IGF-I and IGF-II) play an important regulatory role in fetal growth and development. Alterations in expression of these growth factors may result in developmental abnormalities, macrosomia, and intrauterine growth retardation, which occur with a higher incidence in diabetic pregnancies. In situ hybridization histochemistry was employed to investigate the distribution and abundance of IGF-I and IGF-II in peri-implantation and postimplantation conceptuses from normal and streptozotocin-treated diabetic mice. Animals were sacrificed on gestational days 5, 6, 7, 8, and 9. The entire uterine horn was prepared for hybridization with antisense and sense alpha 35S-dATP labeled oligonucleotide probes for IGF-I, IGF-II, and mouse beta-actin. IGF-I transcript was apparent only in myometrium at 6 days of gestation in normal and diabetic mice. IGF-II transcripts were restricted to trophoectoderm cells within the implantation chamber on day 5. Following implantation, IGF-II transcripts were found in trophoectodermal derivatives, primitive endoderm, mesoderm, heart, walls of the foregut, and mesenchyme in normal and diabetic postimplantation conceptuses. There were no apparent differences between normal and diabetic samples in the distribution and abundance of the IGF-II transcript from gestational days 7, 8, and 9. The embryos from the diabetic mother at day 6 were growth retarded and had a significant decrease in the expression of IGF-II. These results suggest that maternal hyperglycemia may retard development of the early implanting conceptus in a narrow window around day 6 through a mechanism involving decreased IGF-II expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth factors and growth modulators in human uterine endometrium: their potential relevance to reproductive medicine

OBJECTIVE

To provide an up-to-date, comprehensive review on the presence and regulation of growth factors (GFs), GF receptors, and GF regulatory proteins in human endometrium in an effort to understand the potential roles of these proteins in endometrial cell mitosis and differentiation and in endometrial-trophoblast interactions.

DESIGN

Relevant studies were identified through a computerized bibliographic search (MEDLINE; BRS Information Technologies, a division of Maxwell Online, Inc., McLean, VA) and through manual scanning of recent relevant journals.

RESULTS

Several GFs, their receptors, and regulatory proteins have been identified in endometrium, and cellular localization and steroid-dependence of these proteins as well as action of several growth modulators on endometrial cell function have been studied. Epidermal growth factor, transforming growth factor (TGF)-alpha, platelet-derived growth factor, insulin-like growth factors (IGFs) and their binding proteins, fibroblast growth factor (FGF), TGF-beta, colony-stimulating factor (CSF)-1, and interferon-gamma regulate mitosis of endometrial cellular components in vitro. Endothelin-1 may participate in vasoconstriction and FGF may participate in angiogenesis in this tissue in vivo. Interleukins-1 and -6 are believed to be involved in endometrial T-cell activation, and TGF-beta, CSF-1, the interleukins, and the IGFs likely mediate endometrial-trophoblast interactions. The role of tumor necrosis factor in endometrium remains uncertain.

CONCLUSIONS

Current evidence supports the thesis that GFs play a central role in cyclic mitosis and differentiation of endometrial cellular components, recruitment of macrophages in decidualizing endometrium, endometrial-trophoblast interactions, early pregnancy maintenance, tissue shedding in the absence of implantation, and endometrial functionalis regeneration.

Insulin-like growth factor regulation of human endometrial stromal cell function: coordinate effects on insulin-like growth factor binding protein-1, cell proliferation and prolactin secretion

The insulin-like growth factor (IGF) autocrine/paracrine system is believed to be involved in endometrial differentiation, but there is limited information on the specific cellular functions regulated by IGFs in uterine tissues and their regulation of IGF-binding proteins (IGFBPs). We have investigated the regulation by insulin, IGF-I, and IGF-II, of IGFBP secretion in human endometrial stromal cells decidualized in vitro, and examined the interrelationship between the induced changes in IGFBP levels and the biological responses of stromal cells to IGFs. IGFBPs in conditioned media were analyzed by Western ligand blotting, and IGFBP-1 was quantified by an immunoenzymometric assay (IEMA). In the absence of peptides, decidualized stromal cells secreted 25.5 +/- 3.2 micrograms/day per 10(6) cells of IGFBP-1. Insulin caused a dose-dependent reduction of IGFBP-1 secretion (half-maximal inhibition at < 1 ng/ml) to a maximum of 1% of control values. Northern analysis using a specific cDNA probe showed the expression in decidualized stromal cells of a single 1.5 kb transcript for IGFBP-1, which was absent in insulin-treated cells. The effects of IGF-I and IGF-II on IGFBP-1 secretion were biphasic, with initial stimulation (200-250%) that peaked at 1 and 10 ng/ml, respectively, followed by inhibition at higher concentrations (half maximal inhibition at 3 ng/ml and 30 ng/ml, respectively). The decrease in IGFBP-1 levels in decidualized stromal cultures was associated with the induction of mitogenesis by IGF-I and IGF-II, while IGF effects on prolactin secretion paralleled those of IGFBP-1 secretion, with stimulation (243-324%) in the low concentration range followed by inhibition at higher concentrations. These data indicate that endometrial stromal cell IGFBP-1 is regulated by insulin, at concentrations that are compatible with insulin acting via its own receptor, while the effects of IGF-I and IGF-II on IGFBP-1 secretion, are suggestive of their acting probably through the type I IGF receptor. The present study describes distinct effects of the IGFs on stromal cell IGFBPs, that correlate with changes in the proliferative and secretory responses of decidualized stromal cells to the IGFs. Our findings suggest that complex IGF-IGFBP interactions may participate in the regulation of endometrial cell function, and support a role for IGF-II in stromal cell mitogenesis during decidualization, and as a local regulator of decidual cell function during the late secretory phase and early pregnancy.

Implantation and decidualization in rodents

This article reviews the main events of embryo-implantation and decidualization in rodents. In common laboratory rodents the embryo attaches to the uterine epithelial lining, usually on days 4 to 6 of pregnancy. A progressive degree of proximity between trophoblast and epithelium occurs until the epithelial cells undergo apoptosis and detach from the basement membrane. During the attachment stage, the spindle-shaped connective tissue cells that underlie the epithelium next to the embryos transform into polyhedral and closely packed decidual cells. Following the epithelial detachment and the breaching of the basement membrane the embryo is thus in direct contact with decidual cells. These cells accumulate organelles associated with synthesis of macro-molecules, intermediate filaments, and eventually lipid droplets and glycogen. Another remarkable feature of decidual cells is the establishment of gap and adherens intercellular junctions. Differentiation of fibroblasts into decidual cells advances antimesometrially and mesometrially, creating in the endometrium several regions of cells with different morphology. The whole phenomenon of decidualization which is normally triggered by the embryo can be artificially induced in pseudo-pregnant or hormonally-prepared animals with the use of diverse stimuli. The uterine epithelium is probably responsible for the transduction of the initial stimulus. Prostaglandins have been shown to be important in the induction of decidualization. More recently other substances such as leukotrienes, platelet-activating factor (PAF), and transforming growth factor (TGF) have been thought to play a role in induction. Much evidence points to prostaglandin production by the decidual cells. New proteins such as a luteotropic factor, desmin, and other molecules were shown to be produced after rat stromal cells undergo decidual transformation. The extracellular matrix of the mouse decidua contains very thick collagen fibrils. Mouse decidual cells are also very active in phagocytosing the thick fibrils, contributing to the remodeling and involution of the decidua that accompanies embryonic growth. Radioautographic data indicates that mouse decidual cells produce and secrete collagen and sulfated proteoglycans.

The IGFs and their binding proteins in murine development

Recent observations suggest that the diverse actions of the insulin-like growth factors (IGFs) are the result of interactions of the various components that make up the IGF system. The components of this system include IGF-I and -II and their variants, the type 1 and 2 IGF receptors and the insulin-like growth factor binding proteins (IGFBPs). Various components of the IGF system are expressed in the developing mouse embryo and the adjacent tissues of the reproductive tract in which the embryo develops. Thus there is the potential for paracrine interactions between the maternal and fetal tissues. Transcripts for the IGF receptors, IGF-I and IGF-II, have been demonstrated in the periimplantation mouse embryo. While there are now data from gene ablation experiments indicating that IGF-II is important in embryogenesis, the role of other components of the IGF system such as the IGFBPs remains unclear. The data accumulated so far are largely empirical, and there is as yet little compelling evidence that maternal IGFs derived from oviduct or uterine fluid and maternal tissues are necessary for normal fetal development. We have started to develop transgenic mice lines overexpressing IGFBPs to attempt to address the role of these binding proteins in fetal development.

Secretion of prolactin and insulin-like growth factor I by decidual explant cultures from pregnancies complicated by intrauterine growth retardation

OBJECTIVES

Prolactin and insulin-like growth factor I secretion elsewhere in the uterus have been shown to decrease when tissue-specific growth is limited. We investigated their secretion by decidual explant cultures from pregnancies complicated by fetal intrauterine growth retardation.

STUDY DESIGN

Explant cultures from 13 pregnancies complicated by intrauterine growth retardation and 12 control pregnancies were established in minimal essential medium and media was harvested after 24 hours of culture. Prolactin and insulin-like growth factor I concentrations were determined by radioimmunoassay. Total protein in the media was also measured. Data were analyzed by analyses of variance and linear regression.

RESULTS

Decidual prolactin secretion in the pregnancies with intrauterine growth retardation was reduced to 109 +/- 31 ng/100 mg tissue per 24 hours compared with 254 +/- 51 ng in the controls (p = 0.01). Insulin-like growth factor I secretion was reduced to 1.9 +/- 0.6 ng/100 mg tissue per 24 hours from 7.1 +/- 0.9 ng/100 mg in the controls (p < 0.0001). Total protein secretion did not differ between the two groups. Decidual prolactin and insulin-like growth factor I secretion had a highly significant positive correlation (r = 0.71, p = 0.0001).

CONCLUSIONS

Our data show that two protein hormones secreted by the maternal decidua are dramatically reduced in intrauterine growth retardation and warrant further investigation into their roles in the intrauterine environment.

The effect of growth hormone supplementation on in vitro fertilization outcome: a prospective randomized placebo-controlled double-blind study

OBJECTIVE

To determine the effect of growth hormone (GH) supplementation to a long gonadotropin-releasing hormone agonist (GnRH-a)/human menopausal gonadotropin (hMG) treatment protocol, on ovarian response, embryo quality, and clinical outcome in in vitro fertilization (IVF).

DESIGN

Growth hormone or placebo were administered in a prospective randomized double-blind manner.

PATIENTS

Forty-two normal ovulatory, women who were 38 years of age or less with mechanical factor infertility and a normal male factor were selected for this study.

INTERVENTIONS

Gonadotropin-releasing hormone agonist, 0.5 mg/d, was initiated in the midluteal phase of the preceding cycle and continued until the day of human chorionic gonadotropin (hCG) administration. Ovulation induction with hMG was started 14 days after pituitary down regulation (17 beta-estradiol [E2] serum level less than 30 pg/mL). Growth hormone (12 IU/d) or placebo were administered on days 1, 3, 5, and 7 of hMG treatment.

RESULTS

Breaking the code at the completion of the study revealed that 20 women received GH and 22 placebo. The age and duration of infertility did not differ between the two groups. Follicular phase duration, hMG ampules used, serum E2, and number of follicles (greater than or equal to 14 mm) on day of hCG as well as number of oocytes and embryos achieved were similar in both groups. Embryo morphology and rate of cleavage were also similar. Insulin-like growth factor-I (IGF-I) serum levels did not change after pituitary down regulation and increased significantly both after GH/hMG and placebo/hMG ovulation induction treatment. Clinical pregnancy rate (PR) per embryo transfer and implantation rate were 40% versus 32% and 17.9% versus 11.3% in the GH and placebo groups, respectively, and were not statistically different.

CONCLUSIONS

In normo-ovulatory women undergoing ovulation induction for IVF, GH supplementation to hMG after GnRH-a pituitary down regulation does not seem to augment ovarian response or improve embryo quality. The effect of this regimen on actual PRs and implantation rates needs further clarification.

Similar distribution of insulin-like growth factor binding proteins-1, -2, -3 in human fetal tissues

The actions of insulin-like growth factors (IGFs) are modulated by several specific binding proteins (IGF BPs). Since the anatomical distribution of IGF BPs is likely to dictate IGF bioavailability we used immunocytochemistry to localize IGF BP-1, -2, and -3 in early second trimester human fetal tissues. Primary antisera were directed against hIGF BP-1, bIGF BP-2 and hIGF BP-3 respectively, and showed less than 5% cross-reaction with heterologous IGF BP species. The distribution of immunopositive staining was similar for each IGF BP in many tissues being prominent in the epithelial lining of the gut, kidney and lung; in epidermis, adrenal cortex and pancreatic endocrine tissue; and in association with membranes of skeletal muscle fibres and cardiocytes. Unlike IGF BP-1 -2, IGF BP-3 was barely detectable in liver and absent from epiphyseal chondrocytes. Conversely, IGF BP-3 alone was visualized within neurons of the cerebral cortex. The co-distribution of IGF BPs in many human fetal tissues suggests that they may co-ordinately regulate IGF bioavailability in target tissues and modify IGF: receptor interactions.

Growth factors in the uterus: steroidal regulation and biological actions

Rapid progress has been made within the last 5-6 years in characterizing polypeptide growth factors in uterine tissues and fluids. There is convincing evidence that their synthesis and/or secretion is regulated by steroid hormones. The possibility that these growth factors play a central role in growth and development of the uterus or placenta is suggested by the presence of their receptors on uterine or placental cells and their stimulatory effects on these cells in vitro. Since growth factors interact synergistically and also have non-mitogenic functions, the presence of a variety of these factors in the uterus suggests that they probably regulate various aspects of uterine function through complex autocrine and paracine pathways. However, experimental models need to be designed that will permit a more detailed analysis of the actual role of these factors in utero. Fruitful approaches may be to administer neutralizing antibodies or blocking peptides so as to antagonize uterine growth factor action, or to develop appropriate transgenic animals. These and other lines of study should help us to understand the role of growth factors in development of the immature uterus, growth of the placenta or gravid uterus, repair and angiogenesis of the endometrium, and uterine pathology.

Estrogen induction of insulin-like growth factors and myc proto-oncogene expression in the uterus

In contrast to the effects observed in vivo, isolated uterine cells cultured in vitro demonstrate little proliferative response to estrogens. Estrogen induced uterine proliferation involves a carefully orchestrated, sequential activation of genes which encode a variety of biologically active molecules. These include nuclear transcription factors, growth factors and growth factor receptors. Expression of these proteins serve to amplify the effect of estrogen through cellular, autocrine and paracrine mechanisms. In this review the effects of estrogen on uterine expression of the myc family of oncogenes and the insulin-like growth factors are discussed.