Sequential appearance of relaxin, prolactin and IGFBP-1 during growth and differentiation of the human endometrium

Relaxin as a treatment for musculoskeletal fibrosis: What we know and future directions

Fibrotic changes in musculoskeletal diseases arise from the abnormal buildup of fibrotic tissue around the joints, leading to limited mobility, compromised joint function, and diminished quality of life. Relaxin (RLX) attenuates fibrosis by accelerating collagen degradation and inhibiting excessive extracellular matrix (ECM) production. Further, RLX disrupts myofibroblast activation by modulating the TGF-β/Smads signaling pathways, which reduces connective tissue fibrosis. However, the mechanisms and effects of RLX in musculoskeletal pathologies are emerging as increasing research focuses on relaxin's impact on skin, ligaments, tendons, cartilage, joint capsules, connective tissues, and muscles. This review delineates the actions of relaxin within the musculoskeletal system and the challenges to its clinical application. Relaxin shows significant potential in both in vivo and in vitro studies for broadly managing musculoskeletal fibrosis; however, challenges such as short biological half-life and sex-specific responses may pose hurdles for clinical use.

Pathologic maternal and neonatal outcomes associated with programmed embryo transfer: potential etiologies and strategies for prevention

PURPOSE

In the first of two companion papers, we comprehensively reviewed the recent evidence in the primary literature, which addressed the increased prevalence of hypertensive disorders of pregnancy, late-onset or term preeclampsia, fetal overgrowth, postterm birth, and placenta accreta in women conceiving by in vitro fertilization. The preponderance of evidence implicated frozen embryo transfer cycles and, specifically, those employing programmed endometrial preparations, in the higher risk for these adverse maternal and neonatal pregnancy outcomes. Based upon this critical appraisal of the primary literature, we formulate potential etiologies and suggest strategies for prevention in the second article.

METHODS

Comprehensive review of primary literature.

RESULTS

Presupposing significant overlap of these apparently diverse pathological pregnancy outcomes within subjects who conceive by programmed autologous FET cycles, shared etiologies may be at play. One plausible but clearly provocative explanation is that aberrant decidualization arising from suboptimal endometrial preparation causes greater than normal trophoblast invasion and myometrial spiral artery remodeling. Thus, overly robust placentation produces larger placentas and fetuses that, in turn, lead to overcrowding of villi within the confines of the uterine cavity which encroach upon intervillous spaces precipitating placental ischemia, oxidative and syncytiotrophoblast stress, and, ultimately, late-onset or term preeclampsia. The absence of circulating corpus luteal factors like relaxin in most programmed cycles might further compromise decidualization and exacerbate the maternal endothelial response to deleterious circulating placental products like soluble fms-like tyrosine kinase-1 that mediate disease manifestations. An alternative, but not mutually exclusive, determinant might be a thinner endometrium frequently associated with programmed endometrial preparations, which could conspire with dysregulated decidualization to elicit greater than normal trophoblast invasion and myometrial spiral artery remodeling. In extreme cases, placenta accreta could conceivably arise. Though lower uterine artery resistance and pulsatility indices observed during early pregnancy in programmed embryo transfer cycles are consistent with this initiating event, quantitative analyses of trophoblast invasion and myometrial spiral artery remodeling required to validate the hypothesis have not yet been conducted.

CONCLUSIONS

Endometrial preparation that is not optimal, absent circulating corpus luteal factors, or a combination thereof are attractive etiologies; however, the requisite investigations to prove them have yet to be undertaken. Presuming that in ongoing RCTs, some or all adverse pregnancy outcomes associated with programmed autologous FET are circumvented or mitigated by employing natural or stimulated cycles instead, then for women who can conceive using these regimens, they would be preferable. For the 15% or so of women who require programmed FET, additional research as suggested in this review is needed to elucidate the responsible mechanisms and develop preventative strategies.

The role of relaxin in anterior cruciate ligament injuries: a systematic review

OBJECTIVE

Anterior cruciate ligament (ACL) tears are exceedingly common among the athletic population and are seen with higher incidence in females. Observational studies have noted peak ACL tear rates in the luteal phase of the menstrual cycle, a time in which the hormone relaxin peaks in serum concentration.

METHODS

A systematic review of the literature was performed. Inclusion criteria specified all prospective and retrospective studies which included the role of relaxin in the pathogenesis of ACL tears.

RESULTS

Six studies met inclusion criteria yielding 189 subjects from clinical studies and 51 in vitro samples. Included studies found that ACL samples exhibit selective relaxin binding. When pre-treated with estrogen prior to relaxin exposure, female ACL tissue samples exhibit increased expression of collagen degrading receptors.

CONCLUSION

Relaxin displays binding specificity to the female ACL and increased serum concentrations are correlated with increased ACL tear rates in female athletes. Further research is needed in this area.

LEVEL OF EVIDENCE

V.

Menstrual Fluid Factors Mediate Endometrial Repair

Menstruation is a process whereby the outer functionalis layer of the endometrium is shed each month in response to falling progesterone and estrogen levels in a non-conception cycle. Simultaneously with the tissue breakdown, the surface is re-epithelialized, protecting the wound from infection. Once menstruation is complete and estrogen levels start to rise, regeneration progresses throughout the proliferative phase of the cycle, to fully restore endometrial thickness. Endometrial repair is unique compared to tissue repair elsewhere in the adult, in that it is rapid, scar-free and occurs around 400 times during each modern woman's reproductive life. The shedding tissue and that undergoing repair is bathed in menstrual fluid, which contains live cells, cellular debris, fragments of extracellular matrix, activated leukocytes and their products, soluble cellular components and extracellular vesicles. Proteomic and other analyses have revealed some detail of these components. Menstrual fluid, along with a number of individual proteins enhances epithelial cell migration to cover the wound. This is shown in endometrial epithelial and keratinocyte cell culture models, in an ex vivo decellularized skin model and in pig wounds in vivo. Thus, the microenvironment provided by menstrual fluid, is likely responsible for the unique rapid and scar-free repair of this remarkable tissue. Insight gained from analysis of this fluid is likely to be of value not only for treating endometrial bleeding problems but also in providing potential new therapies for poorly repairing wounds such as those seen in the aged and in diabetics.

Failure of Decidualization and Maternal Immune Tolerance Underlies Uterovascular Resistance in Intra Uterine Growth Restriction

Failure of uterine vascular transformation is associated with pregnancy complications including Intra Uterine Growth Restriction (IUGR). The decidua and its immune cell populations play a key role in the earliest stages of this process. Here we investigate the hypothesis that abnormal decidualization and failure of maternal immune tolerance in the second trimester may underlie the uteroplacental pathology of IUGR. Placental bed biopsies were obtained from women undergoing elective caesarian delivery of a healthy term pregnancy, an IUGR pregnancy or a pregnancy complicated by both IUGR and preeclampsia. Decidual tissues were also collected from second trimester terminations from women with either normal or high uterine artery Doppler pulsatile index (PI). Immunohistochemical image analysis and flow cytometry were used to quantify vascular remodeling, decidual leukocytes and decidual status in cases vs. controls. Biopsies from pregnancies complicated by severe IUGR with a high uterine artery pulsatile index (PI) displayed a lack of: myometrial vascular transformation, interstitial, and endovascular extravillous trophoblast (EVT) invasion, and a lower number of maternal leukocytes. Apoptotic mural EVT were observed in association with mature dendritic cells and T cells in the IUGR samples. Second trimester pregnancies with high uterine artery PI displayed a higher incidence of small for gestational age fetuses; a skewed decidual immunology with higher numbers of; CD8 T cells, mature CD83 dendritic cells and lymphatic vessels that were packed with decidual leukocytes. The decidual stromal cells (DSCs) failed to differentiate into the large secretory DSC in these cases, remaining small and cuboidal and expressing lower levels of the nuclear progesterone receptor isoform B, and DSC markers Insulin Growth Factor Binding protein-1 (IGFBP-1) and CD10 as compared to controls. This study shows that defective progesterone mediated decidualization and a hostile maternal immune response against the invading endovascular EVT contribute to the failure of uterovascular remodeling in IUGR pregnancies.

G-Protein-coupled receptors as potential drug candidates in preeclampsia: targeting the relaxin/insulin-like family peptide receptor 1 for treatment and prevention

BACKGROUND

Important roles for G-protein-coupled receptors (GPCRs) have been identified in the maternal physiological adaptations to pregnancy and in the pathogenesis of preeclampsia. On this basis, GPCRs are potential therapeutic targets for preeclampsia.

OBJECTIVES AND RATIONALE

In this review, vasopressin and apelin are initially considered in this context before the focus on the hormone relaxin and its cognate receptor, the relaxin/insulin-like family peptide receptor 1 (RXFP1). Based on both compelling scientific rationale and a promising safety profile, the relaxin ligand-receptor system is comprehensively evaluated as a potential therapeutic endpoint in preeclampsia.

SEARCH METHODS

The published literature relating to the topic was searched through January 2016 using PubMed.

OUTCOMES

Relaxin is a peptide hormone secreted by the corpus luteum; it circulates in the luteal phase and during pregnancy. Activation of RXFP1 is vasodilatory; thus, relaxin supplementation is expected to at least partly restore the fundamental vasodilatory changes of normal pregnancy, thereby alleviating maternal organ hypoperfusion, which is a major pathogenic manifestation of severe preeclampsia. Specifically, by exploiting its pleiotropic hemodynamic attributes in preeclampsia, relaxin administration is predicted to (i) reverse robust arterial myogenic constriction; (ii) blunt systemic and renal vasoconstriction in response to activation of the angiotensin II receptor, type 1; (iii) mollify the action of endogenous vasoconstrictors on uterine spiral arteries with failed remodeling and retained smooth muscle; (iv) increase arterial compliance; (v) enhance insulin-mediated glucose disposal by promoting skeletal muscle vasodilation and (vi) mobilize and activate bone marrow-derived angiogenic progenitor cells, thereby repairing injured endothelium and improving maternal vascularity in organs such as breast, uterus, pancreas, skin and fat. By exploiting its pleiotropic molecular attributes in preeclampsia, relaxin supplementation is expected to (i) enhance endothelial nitric oxide synthesis and bioactivity, as well as directly reduce vascular smooth muscle cytosolic calcium, thus promoting vasodilation; (ii) improve the local angiogenic balance by augmenting arterial vascular endothelial and placental growth factor (VEGF and PLGF) activities; (iii) ameliorate vascular inflammation; (iv) enhance placental peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PCG1α) expression, and hence, peroxisome proliferator-activated receptor gamma (PPAR-γ) activity and (v) confer cytotrophoblast and endothelial cytoprotection. Insofar as impaired endometrial maturation (decidualization) predisposes to the development of preeclampsia, relaxin administration in the late secretory phase and during early pregnancy would be anticipated to improve decidualization, and hence trophoblast invasion and spiral artery remodeling, thereby reducing the risk of preeclampsia. Relaxin has a favorable safety profile both in the non-pregnant condition and during pregnancy.

WIDER IMPLICATIONS

There is a strong scientific rationale for RXFP1 activation in severe preeclampsia by administration of relaxin, relaxin analogs or small molecule mimetics, in order to mollify the disease pathogenesis for safe prolongation of pregnancy, thus allowing time for more complete fetal maturation, which is a primary therapeutic endpoint in treating the disease. In light of recent data implicating deficient or defective decidualization as a potential etiological factor in preeclampsia and the capacity of relaxin to promote endometrial maturation, the prophylactic application of relaxin to reduce the risk of preeclampsia is a plausible therapeutic approach to consider. Finally, given its pleiotropic and beneficial attributes particularly in the cardiovascular system, relaxin, although traditionally considered as a 'pregnancy' hormone, is likely to prove salutary for several disease indications in the non-pregnant population.

The role of relaxin in mare reproductive physiology: A comparative review with other species

Relaxin is a peptide hormone best known for its action during the latter half of pregnancy, in particular for its softening effect on pelvic ligaments that aids in preparation of the birth canal for the impending delivery of the fetus. The source of relaxin during early pregnancy varies across species, with the CL being the main source in a number of species. The main source of relaxin during late equine pregnancy is the placenta. In mares with impaired placental function, circulating relaxin levels decline before abortion. During early pregnancy, relaxin promotes endometrial angiogenesis through upregulating endometrial expression of vascular endothelial growth factor. The horse is unique in that the equine conceptus expresses relaxin messenger RNA as early as 8 days after ovulation, with levels increasing as conceptus development proceeds. Although secretion of functional relaxin has not been verified, it is likely, given that the embryo also expresses transcripts coding for enzymes processing the prohormone to yield the mature hormone. Furin, an enzyme which belongs to the subtilisin-like proprotein convertase family known to process preprorelaxin, appears to be the foremost convertase expressed by equine conceptuses. Conceptus-derived relaxin could drive endometrial angiogenesis and also act in an autocrine fashion to promote the embryo's own development. Relaxin is also expressed by ovarian structures during the nonpregnant estrous cycle. In the mare, follicular expression of relaxin is comparable among follicles of varying size and has been localized to granulosa and theca cells. In women and pigs, relaxin appears to promote follicular development. In the rat, multiple lines of evidence indicate that relaxin is involved in the ovulatory process. In the mare, relaxin might play a similar role in the ovulatory process, as in equine ovarian stromal cells relaxin promotes the secretion of gelatinases and tissue inhibitors of metalloproteinases; local proteolysis of the follicular wall is integral to the ovulatory process. However, functional studies addressing the role of relaxin in the ovulatory process are missing in the mare.

Relaxin deficiency results in increased expression of angiogenesis- and remodelling-related genes in the uterus of early pregnant mice but does not affect endometrial angiogenesis prior to implantation

BACKGROUND

Extensive uterine adaptations, including angiogenesis, occur prior to implantation in early pregnancy and are potentially regulated by the peptide hormone relaxin. This was investigated in two studies. First, we took a microarray approach using human endometrial stromal (HES) cells treated with relaxin in vitro to screen for target genes. Then we aimed to investigate whether or not relaxin deficiency in mice affected uterine expression of representative genes associated with angiogenesis and uterine remodeling, and also blood vessel proliferation in the pre-implantation mouse endometrium.

METHODS

Normal HES cells were isolated and treated with recombinant human relaxin (10 ng/ml) for 24 h before microarray analysis. Reverse transcriptase PCR was used to analyze gene expression of relaxin and its receptor (Rxfp1) in ovaries and uteri; quantitative PCR was used to analyze steroid receptor, angiogenesis and extracellular matrix remodeling genes in the uteri of wild type (Rln+/+) and Rln-/- mice on days 1-4 of pregnancy. Immunohistochemistry localized endometrial endothelial cell proliferation and mass spectrometry measured steroid hormones in the plasma.

RESULTS

Microarray analysis identified 63 well-characterized genes that were differentially regulated in HES cells after relaxin treatment. Expression of some of these genes was increased in the uterus of Rln+/+ mice by day 4 of pregnancy. There was significantly higher vascular endothelial growth factor A (VegfA), estrogen receptor 1 (Esr1), progesterone receptor (Pgr), Rxfp1, egl-9 family hypoxia-inducible factor 1 (Egln1), hypoxia inducible factor 1 alpha (Hif1α), matrix metalloproteinase 14 (Mmp14) and ankryn repeat domain 37 (Ankrd37) in Rln-/- compared to Rln+/+ mice on day 1. Progesterone receptor expression and plasma progesterone levels were higher in Rln-/- mice compared to Rln+/+ mice. However, endometrial angiogenesis was not advanced as pre-implantation endothelial cell proliferation did not differ between genotypes.

CONCLUSIONS

Relaxin treatment modulates expression of a variety of angiogenesis-related genes in HES cells. However, despite accelerated uterine gene expression of steroid receptor, progesterone and angiogenesis and extracellular matrix remodeling genes in Rln-/- mice, there was no impact on angiogenesis. We conclude that although relaxin deficiency results in phenotypic changes in the pre-implantation uterus, endogenous relaxin does not play a major role in pre-implantation angiogenesis in the mouse uterus.

Relaxin family peptides and their receptors

There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.

Prospective correlation between serum relaxin concentration and anterior cruciate ligament tears among elite collegiate female athletes

BACKGROUND

The female anterior cruciate ligament may be more susceptible to injury than the male anterior cruciate ligament because of the gender-specific expression of receptors for relaxin, a collagenolytic hormone that promotes remodeling of the anterior cruciate ligament.

PURPOSE

This study was undertaken to investigate whether collegiate female athletes with elevated serum relaxin concentrations (SRC) sustain anterior cruciate ligament tears at an increased rate compared with those with lower SRC.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

From 2005 to 2010, 143 Division I female athletes from 2 universities participating in sports at high risk for anterior cruciate ligament tears (basketball, lacrosse, field hockey, soccer, gymnastics, and volleyball) were recruited to participate. Questionnaires and urine luteinizing hormone (LH) tests were used to determine participants' anterior cruciate ligament injury and menstrual history and to identify their mid-luteal phase or projected cycle days 21 to 24. Serum samples were obtained for progesterone and relaxin ELISA (enzyme-linked immunosorbent assay) analysis. Participants were monitored for anterior cruciate ligament injury over their 4-year National Collegiate Athletic Association athletic career.

RESULTS

A total of 128 participants completed the study and were eligible for data analysis. The cumulative incidence of complete anterior cruciate ligament tear over the 4-year study period was 21.9%, and varied significantly by sport (P < .001). The mean SRC for athletes with anterior cruciate ligament tears (6.0 ± 8.1 pg/mL) was significantly higher than that for those without anterior cruciate ligament tears (1.8 ± 3.4 pg/mL; P = .013). In subgroup analysis of the 46 athletes who had detectable SRC, the cumulative incidence of anterior cruciate ligament tear was 14 of 46 (30.4%); the mean SRC among athletes with anterior cruciate ligament tears (14 of 46) was 12.1 ± 7.7 pg/mL and without anterior cruciate ligament tears (32 of 46), 5.7 ± 3.6 pg/mL (P = .002). When 6.0 pg/mL was set as the SRC cutoff for screening athletes for risk of anterior cruciate ligament tear in the subgroup with detectable relaxin levels, the test had 71% sensitivity, 69% specificity, 52% positive predictive value, 88% negative predictive value, and a relative risk of 4.4. These values were significant by χ(2) test (P = .003) and receiver operating characteristic analysis (P = .002).

CONCLUSION

Elite female athletes with anterior cruciate ligament tears have higher SRC than those without tears. Those with an SRC greater than 6.0 pg/mL had over 4 times increased risk for a tear.

CLINICAL RELEVANCE

Females with higher serum relaxin levels may be at increased risk for anterior cruciate ligament tears. Further investigation of the clinical utility of SRC testing is warranted.

Trends in serum relaxin concentration among elite collegiate female athletes

PURPOSE

This study was designed to investigate the relationship between serum relaxin concentration (SRC) and menstrual history and hormonal contraceptive use among elite collegiate female athletes. Evaluation of SRC in athletes is necessary, because relaxin has been associated with increased knee joint laxity and decreased anterior cruciate ligament (ACL) strength in animal models.

METHODS

National Collegiate Athletic Association Division I female athletes participating in sports at high risk for ACL tears - basketball, field hockey, gymnastics, lacrosse, soccer, and volleyball - were invited to participate. All participants completed a questionnaire about their menstrual history and hormonal contraceptive use. Venipuncture was performed to obtain samples of serum progesterone and relaxin. Samples were obtained during the mid-luteal phase from ovulating participants, and between the actual or projected cycle days 21 to 24, from anovulatory participants. Serum concentration of relaxin and progesterone was determined by ELISA and the data were analyzed using SPSS statistical software with significance set at P = 0.05.

RESULTS

169 female athletes participated. The mean SRC among all participants was 3.08 ± 6.66 pg/mL). The mean SRC differed significantly between those participants using hormonal contraceptives (1.41 pg/mL) and those not using hormonal contraceptives (3.08 pg/mL, P = 0.002). Mean SRC was lowest among amenorrheic participants (1.02 pg/mL) and highest among oligomenorrheic participants (3.71 pg/mL) and eumenorrheic participants (3.06 pg/mL); these differences were not significant (P = 0.53). Mean serum progesterone concentration (SPC) differed significantly between those participants using hormonal contraceptives (2.80 ng/mL), and those not using hormonal contraceptives (6.99 ng/mL, P < 0.0001).

CONCLUSIONS

There is a positive correlation between serum progesterone and SRC and an attenuation of SRC with hormonal contraceptive use. Our results underscore the significant role that hormonal contraceptives can play in decreasing relaxin levels, if future investigations establish a link between relaxin levels and ligamentous injury among female athletes.

Interleukin 11 and activin A synergise to regulate progesterone-induced but not cAMP-induced decidualization

Blastocyst implantation, placentation and the establishment of pregnancy in the human are dependent on the adequate decidualization of endometrial stromal cells. Locally produced and temporally regulated products such as interleukin 11 (IL11), and activin A are involved in this process; however, the molecular interactions that regulate decidualization are largely unknown. Here, we investigated whether IL11 and activin A interact to promote human endometrial stromal cell (HESC) decidualization using an in vitro model. HESCs, induced to decidualize by cAMP or progesterone, were treated with IL11, activin A or IL11 plus activin A combined and decidual progress was examined using prolactin as a decidual marker. Treatment with combined IL11 plus activin A enhanced progesterone-induced decidualization above control or treatment with IL11 or activin A alone. Treatment had no effect on cAMP-decidualized HESC. Investigation of IL11 and activin A stimulation of (respectively) activin A and IL11 expression in undifferentiated HESC was by real-time PCR and ELISA. Activin A treatment induced IL11 secretion and phosphorylation of the activin A signalling component, SMAD2 (measured by ELISA). Inclusion of the TGFbeta 1 receptor inhibitor, SB431542, in the activin A treatment, reduced pSMAD2 and IL11 secretion. This study suggests that activin A is an early inducer of decidualization, regulating the secretion of IL11. This data provides insight into the processes underlying decidualization, which are important for understanding implantation and placentation and have potential clinical applications for the regulation of fertility.

Matrix metalloproteinases and their tissue inhibitors in endometrial remodelling and menstruation

The architecture of the human endometrium is extensively remodelled during the course of each normal menstrual cycle, unlike most other tissues and organs which undergo very little change during adult life. During menstruation, when loss of most of the functionalis layer occurs, there is concomitant epithelial regrowth; repair of the luminal surface is complete almost as bleeding ceases. During the proliferative phase of the cycle and under the influence of rising oestrogen levels, the stromal cells, glands and blood vessels undergo rapid proliferation which results in tissue thickening. Following ovulation (around day 14 of the idealized 28-day cycle), the secretory phase of the cycle is characterized by increasing tortuosity of the spiral arterioles and glands and increased glandular secretory activity. After about day 22, decidualization of many of the stromal fibroblasts also occurs, the resultant decidual cells having many characteristics typical of epithelial cells. Periods of tissue oedema are apparent both in mid-proliferative (days 8–11) and mid-secretory (days 20–23) endometrium. Late in the cycle, there is regression of the tissue as menstruation is initiated.

Opposite regulation of transforming growth factors-beta2 and -beta3 expression in the human endometrium

TGF-betas have been reported to mediate the repression by progesterone of several matrix metalloproteinases in the human endometrium, thereby preventing menstrual breakdown. Because of conflicting reports on the expression profiles, source, and regulation of the TGF-beta system in this tissue, we investigated by real-time RT-PCR and ELISA the expression of the three TGF-betas (total and mature forms) and their two receptors throughout the menstrual cycle, and their regulation by ovarian steroids in cultured explants including their microdissected epithelial and stromal compartments. Regulation by cAMP and MAPK was further investigated. This comprehensive study on a large collection of endometrial samples evidenced a differential regulation of TGF-beta isoforms expression, both in vivo and in explant culture. In vivo, TGF-beta2 increased by about 5-fold at the mid-late secretory phase then declined after menstruation; TGF-beta3 increased at menstruation and remained high during the proliferative phase; TGF-beta1 was maximal at menstruation. In explants cultured without ovarian steroids both TGF-beta2 and -beta3 were preferentially expressed in the stroma. Ovarian steroids strongly repressed both TGF-beta2 and -beta3 in stroma but only TGF-beta2 in glands. cAMP prevented inhibition by ovarian steroids of TGF-beta2 but not -beta3. In presence of ovarian steroids, MAPK inhibitors (p38 and ERK pathways) stimulated TGF-beta3 but inhibited TGF-beta2 expression. In conclusion, TGF-beta2 and -beta3 are differentially expressed during the menstrual cycle and regulated by progesterone in epithelial vs stromal cells. The opposite regulation of TGF-beta2 and -beta3 by cAMP and MAPK could account for their distinct expression in vivo.

Increased phosphorylation of myosin light chain prevents in vitro decidualization

Differentiation of stromal cells into decidual cells, which is critical to successful pregnancy, represents a complex transformation requiring changes in cytoskeletal architecture. We demonstrate that in vitro differentiation of human uterine fibroblasts into decidual cells includes down-regulation of alpha-smooth muscle actin and beta-tubulin, phosphorylation of focal adhesion kinase, and redistribution of vinculin. This is accompanied by varied adhesion to fibronectin and a modified ability to migrate. Cytoskeletal organization is determined primarily by actin-myosin II interactions governed by the phosphorylation of myosin light chain (MLC20). Decidualization induced by cAMP [with estradiol-17beta (E) and medroxyprogesterone acetate (P)] results in a 40% decrease in MLC20 phosphorylation and a 55% decline in the long (214 kDa) form of myosin light-chain kinase (MLCK). Destabilization of the cytoskeleton by inhibitors of MLCK (ML-7) or myosin II ATPase (blebbistatin) accelerates decidualization induced by cAMP (with E and P) but inhibits decidualization induced by IL-1beta (with E and P). Adenoviral infection of human uterine fibroblast cells with a constitutively active form of MLCK followed by decidualization stimuli leads to a 30% increase in MLC20 phosphorylation and prevents decidualization. These data provide evidence that the regulation of cytoskeletal dynamics by MLC20 phosphorylation is critical for decidualization.

IGFBP-1 inhibits EGF mitogenic activity in cultured endometrial stromal cells

The properties of the insulin-like growth factor-binding proteins (IGFBP-1 to 6) are not limited to modulation of IGF actions. IGFBP-1, which shares an Arg-Gly-Asp (RGD) motif in its C-terminal domain, modulates cell motility by binding to integrin alpha5beta1. The cross-talks between integrins and growth factor receptor signalling pathways are extensively documented, particularly in the case of the epidermal growth factor receptor (EGFR). However, whether IGFBP-1 can modulate growth factor signalling through its interaction with integrin alpha5beta1 has not yet been studied. As EGF is involved in the decidualisation of endometrial stromal cells (ESCs) and as decidualised ESCs are a source of IGFBP-1, we investigated if IGFBP-1 can modulate EGF effects on ESCs. RGD- and IGF-independent inhibition of EGF mitogenic activity and EGFR signalling by IGFBP-1 were demonstrated in ESC primary cultures, A431, cells and in mouse fibroblasts lacking IGF receptors.

Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle

This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.

Implantation and Pregnancy Following In Vitro Fertilization and the Effect of Recombinant Human Relaxin Administration in Macaca fascicularis1

Implantation and early pregnancy, and the potential effects of the reproductive-hormone relaxin, were examined in the cynomolgus macaque (Macaca fascicularis) following in vitro fertilization and embryo transfer. Mature oocytes were collected from regularly cycling, female cynomolgus monkeys subjected to ovarian superovulation using recombinant human FSH and hCG. Oocytes fertilized in vitro were cultured to the 4- to 8-cell stage, slow-cooled, and stored in liquid nitrogen before thawing and embryo transfer. Regularly cycling recipients were administered recombinant human relaxin or vehicle for 21 days through the peri-implantation period (Day 0 = pump implantation), during which time the thawed embryos were transferred (Day 7). Endometrial thickness and the number of gestational sacs were monitored by ultrasound at three time points (Days 7, 21, and 28). The number of days of placental sign (implantation bleeding) in pregnant females and menses in nonpregnant females were also recorded. Implantation (gestational sacs/embryo transferred) and multiple pregnancy (multiple gestations/ pregnant recipient) rates were slightly higher in relaxin-treated recipients compared to vehicle-treated recipients. Administration of relaxin was associated with increased implantation bleeding in pregnant females. Endometrial thickness was increased in relaxin-treated recipients at Days 7 and 28 compared to Day 0, but these differences were not observed at the same time points in vehicle-treated females. Systemic administration of recombinant human relaxin in an in vitro fertilization/embryo transfer setting was associated with effects consistent with a role for this hormone in endometrial physiology in primates.

Cellular localisation of insulin-like growth factor binding protein-2 (IGFBP-2) during development of the marine fish, Sparus aurata

The spatial localisation of insulin-like growth-factor-binding protein-2 (IGFBP-2) and its mRNA was investigated during larval and post-larval developmental stages of the gilthead seabream ( Sparus aurata) by immunohistochemistry and in situ hybridisation with specific antisera and riboprobes. During larval development, immunoreactivity was found in skin, muscle, gills, pharynx, intestine, liver and olfactory epithelium. After metamorphosis, immunoreactivity was found in the oesophageal epithelium (the strongest reaction) and in red skeletal muscle, heart muscle, the thymus and the epithelium of renal tubules. In the adult, immunostaining with IGFBP-2 antibody was also found in the saccus vasculosus, ovary and testis. IGFBP-2 mRNA was detected by in situ hybridisation mainly in the intestine, skeletal musculature and ovary. These results show that IGFBP-2 protein and mRNA are expressed in a variety of seabream tissues, suggesting that IGFBP-2 regulates the actions of IGFs on these tissues during development and growth.

Immunohistological localization of insulin-like growth factor binding protein-1 in primary implantation sites and trauma-induced deciduomal tissues of the rhesus monkey

We have earlier demonstrated that there is a close similarity in the temporo-spatial pattern in the onset of oedema, epithelial-plaque transformation, stromal decidualization and influx of granulated lymphocytes in artificially trauma-induced deciduomal endometrium with such events in maternal endometrium at the primary implantation site during early stages of pregnancy in the rhesus monkey. In the present study, we have immunohistochemically examined whether the pattern of insulin-like growth factor-binding protein 1 (IGFBP-1) protein expression in conceptus tissue and maternal endometrium during lacunae and villous placenta stages of gestation in the rhesus monkey is developmental stage-specific and whether a discernible difference exists in the temporo-spatial characteristics of IGFBP-1 protein expression between conceptus associated implantation-decidualization and trauma induced deciduoma in the rhesus monkey. Trophoblast cells failed to exhibit IGFBP-1 immunopositive staining at any stage of implantation-placentation studied. Epithelial cells in plaque acini, endothelial cells, and vascular smooth muscle also did not show any immunopositive staining for IGFBP-1 in samples of primary implantation sites and trauma-induced deciduoma. Maternal endometrial epithelial and stromal-decidual cells however exhibited a temporal and spatial pattern of IGFBP-1 expression in cell-type specific manner and clear distinctions were observed between conception and deciduoma samples. Our results suggest that IGFBP-1 expression is highly tissue and development-specific and that conceptus-derived signals are necessary to initiate the glandular expression of IGFBP-1 during the early stage of gestation.

Biology of primate relaxin: a paracrine signal in early pregnancy?

Relaxin is a peptide hormone that exerts numerous effects in a variety of tissues across a broad range of species. Although first identified more than 75 years ago interest in relaxin biology has waxed and waned over the years consistent with peaks and troughs of new experimental data on its wide-ranging biological effects and advances in relaxin enabling technologies. Recent insights into species-dependent differences in relaxin biology during pregnancy have once again stimulated a relative surge of interest in the study of relaxin's reproductive biology. Identification and pharmacological characterization of orphaned relaxin receptors and exploration of its paracrine effects on pregnancy using genomic and proteomic technologies have succeeded in fueling current interest in relaxin research. Primates and non-primate vertebrates exhibit very disparate profiles of relaxin genomics, proteomics and functional biology. Non-human primates appear to exhibit a very close similarity to humans with respect to relaxin reproductive biology but the similarities and subtle differences are only just beginning to be understood. We, and others, have shown that relaxin produces significant changes to the non-human primate endometrium during the peri-implantation period that are consistent with relaxin's long perceived role as a paracrine modulator of pregnancy. The purpose of this review is to summarize the reproductive biology of relaxin in non-human primates with a specific emphasis on the paracrine role of ovarian and endometrial relaxin during embryo implantation and early pregnancy.

Relaxin's physiological roles and other diverse actions

Relaxin has vital physiological roles in pregnant rats, mice, and pigs. Relaxin promotes growth and softening of the cervix, thus facilitating rapid delivery of live young. Relaxin also promotes development of the mammary apparatus, thus enabling normal lactational performance. The actions of relaxin on the mammary apparatus vary among species. Whereas relaxin is required for development of the mammary nipples in rats and mice, it is essential for prepartum development of glandular parenchyma in pregnant pigs. During pregnancy relaxin also inhibits uterine contractility and promotes the osmoregulatory changes of pregnancy in rats. Recent studies with male and nonpregnant female rodents revealed diverse therapeutic actions of relaxin on nonreproductive tissues that have clinical implications. Relaxin has been reported to reduce fibrosis in the kidney, heart, lung, and liver and to promote wound healing. Also, probably through its vasodilatory actions, relaxin protects the heart from ischemia-induced injury. Finally, relaxin counteracts allergic reactions. Knowledge of the diverse physiological and therapeutic actions of relaxin, coupled with the recent identification of relaxin receptors, opens numerous avenues of investigation that will likely sustain a high level of research interest in relaxin for the foreseeable future.

Action of mifepristone on the expression of insulin-like growth factor binding protein-1 mRNA and protein during the early luteal phase in the human oviduct

OBJECTIVE

To investigate the effects of the antiprogestin mifepristone on the expression of insulin-like growth factor binding protein-1 (IGFBP-1) mRNA and protein during the early luteal phase in the human oviduct.

DESIGN

Prospective case-control study.

SETTING

University hospital.

PATIENT(S)

Fourteen healthy women with regular menstrual cycles who were admitted to the hospital for voluntary sterilization by the laparoscopic technique.

INTERVENTION(S)

Treatment with 200 mg of mifepristone was administered on day LH+2. Fallopian tube samples were obtained on days LH+4 to LH+6.

MAIN OUTCOME MEASURE(S)

Expression of IGFBP-1 was identified using immunhistochemistry, and mRNA levels were determined with semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULT(S)

Immunoreactivity for IGFBP-1 was primarily localized to the cytoplasm of the oviductal epithelial cells. Messenger RNA for IGFBP-1 was identified in total RNA extracted from the same fallopian tube samples. There was a significant increase in the expression of IGFBP-1 immunostaining and mRNA after treatment with mifepristone.

CONCLUSION(S)

These data further illustrate the complex actions of mifepristone and support the view that changes in the oviductal environment after treatment with mifepristone may be detrimental to normal gamete transport and function and contribute to the contraceptive action of mifepristone.

Expression pattern of metalloproteinases and tissue inhibitors of matrix-metalloproteinases in cycling human endometrium

The cyclic growth, differentiation, and cell death of endometrium represents the most dynamic example of steroid-driven tissue turnover in human adults. Key effectors in these processes-matrix metalloproteinases (MMPs) and their specific inhibitors (TIMPs)-are regulated by ovarian steroids and, locally, by cytokines. We used reverse transcription-polymerase chain reaction to evaluate the expression of both transcriptionally regulated molecules such as estrogen receptor-alpha, progesterone receptor, and prolactin and a large array of MMPs and TIMPs (MMP-1, -2, -3, -7, -8, -9, -11, -12, -19, -26, MT1-MMP, MT2-MMP, MT3-MMP, TIMP-1, -2, -3). Altogether, three distinct patterns of MMP and two patterns of TIMP expression were detected in cycling endometrium: 1). MMPs restricted to the menstrual period (MMPs-1, -3, -8, -9, -12); 2). MMPs and TIMPs expressed throughout the cycle (MMP-2, MT1-MMP, MT2-MMP, MMP-19, TIMP-1, and TIMP-2); 3). MMPs predominantly expressed during the proliferative phase (MMP-7, MMP-11, MMP-26, and MT3-MMP); and 4). TIMP-3, which, contrary to the other TIMPs, shows significant modulations, with maximum expression during the late secretory and menstrual phases. These specific patterns of MMP expression associated with each phase of the cycle may point to specific roles in the processes of menstruation, housekeeping activities, angiogenesis, tissue growth, and extracellular matrix remodeling.

Complex regulation of decidualization: a role for cytokines and proteases--a review

Decidualization of the endometrial stroma is a precondition for successful establishment of pregnancy. While the local molecular mechanisms driving decidualization are still largely unknown, a number of autocrine/paracrine factors have been identified as differentiation factors in this process. These include the cytokines, interleukin 11, activin A and monoclonal non-specific suppressor factor beta (MNSFbeta). Furthermore, locally produced proteases, including proprotein convertase 6 and matrix metalloproteinases, enable expansion of the tissue and processing of regulatory molecules. This article reviews recent work from our laboratory on the roles of these factors in decidualization.

Leukemia inhibitory factor and interleukin-11: cytokines with key roles in implantation

Members of the interleukin-6 family of cytokines include leukaemia inhibitory factor (LIF), interleukin-6, interleukin-11, cardiotrophin, ciliary neurotropic growth factor, oncostatin M and the recently discovered cardiotropin-like cytokine (NNT-1). These ligands signal via heterodimeric receptors composed of ligand-specific alpha chains and the common signal-transducing subunit gp130. Gene targeting in mice provided the first indication of a role for interleukin 6 family cytokines in implantation with the generation of mice with a null mutation of the gene encoding LIF. LIF null female mice were infertile because of failure of blastocyst implantation. More recently, interleukin-11 signalling has been shown to be required for the uterine decidualization response. This review describes the insights into the role of interleukin-6 family cytokines in female fertility that have come from gene targeting experiments in mice.

Relaxin peptides are new global players

Relaxin (RLX) has come of age. From being one of the earliest hormones described with a very specific function in parturition, recent research has now shown that it is involved in a variety of roles, from endometrial differentiation during embryo implantation, to being a response factor in infarct and wound situations. It ameliorates fibrosis, and might also be involved in tumour growth and progression. And it is not alone: two other closely related peptide hormones have recently been identified, one specific for the brain, the other with roles in testicular descent and ovarian apoptosis. Finally, the recent cloning of the RLX receptors now provides the basis for a new molecular pharmacology for these peptide hormones, and preliminary studies suggest that their signal transduction is both interesting and unusual.

Relaxin gene and protein expression and its regulation of procollagenase and vascular endothelial growth factor in human endometrial cells

Extensive evidence demonstrates pronounced effects of relaxin on the differentiation of human endometrial cells in vitro. In vivo data in rhesus monkeys suggest a role for relaxin in the development of endometrial vascular architecture. In women, pregnancy can be established and maintained in the absence of circulating relaxin. Thus, local synthesis by the endometrium is necessary if relaxin plays a physiological role in human endometrial function. Although relaxin protein and the prorelaxin C peptide have been localized to human endometrium, no data for relaxin synthesis have been provided to date. We therefore assessed relaxin mRNA and protein levels in cultured, defined human endometrial cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were used to demonstrate the presence of relaxin mRNA in human stromal and glandular epithelial cells. Secretion of the protein into the media of cultured cells of both types was also detected. Relaxin stimulated the expression of vascular endothelial growth factor in glandular epithelial and stromal cells that were isolated from tissue that had been taken during the secretory phase of the cycle. Relaxin inhibited the expression of procollagenase from both glandular epithelial cells, with a more marked inhibition demonstrated from cells that were isolated from tissue that had been taken during the secretory phase, and from stromal cells. These data demonstrate that human endometrial cells synthesize relaxin, and they support the concept that relaxin fosters endometrial conditions that are required for implantation in women.

A dynamic shift of VEGF isoforms with a transient and selective progesterone-induced expression of VEGF189 regulates angiogenesis and vascular permeability in human uterus

A key mechanism underlying physiological angiogenesis of the human endometrium is its ability to regenerate the vascular capillary network and to perform vascular remodeling (i.e., development of spiral arteries). Vascular endothelial growth factor (VEGF) is associated with angiogenesis and capillary permeability in this tissue. VEGF is expressed as several spliced variants, its main human isoforms contain 121 and 165 aa; 17beta-estradiol (E(2)) increases endometrial VEGF, possibly in all isoforms. Here we show that progesterone (P) selectively increases the expression of the VEGF(189) (V(189)) isoform in the human uterus. V(189) is identified in the conditioned medium of stromal cells treated with E(2) + P; its presence in this in vitro model of decidual stromal cells is detected after 6-8 days, using ELISA, and after 8-10 days, using Western blot analysis with different antibodies, including one specific for V(189). The secretion pattern of V(189) parallels that of the decidual protein IGFBP-1. V(189) is secreted as a native isoform, as compared with the migration of recombinant V(189) by SDS/PAGE. In situ hybridization and immunocytochemistry(,) performed on the same biopsies, suggest that decidual cells express V(189) during the mid-late secretory phase of the menstrual cycle and early gestation. Finally, using an in vivo permeability assay, we show that native V(189) increases capillary permeability. These observations demonstrate that P regulates V(189) expression in decidual cells, which could have important implications for understanding uterine vascular remodeling and implantation, and may be relevant in a range of disease states such as edema and irregular bleeding.

Circulating ovarian steroids and endometrial matrix metalloproteinases (MMPs)

Recent studies strongly suggest that matrix metalloproteinases (MMPs) play a key role in the initiation of menstrual bleeding in the human endometrium upon the fall of ovarian steroid serum concentrations by inducing the degradation of the extracellular matrix of this mucosa. MMPs are also involved in abnormal endometrial bleeding and have been identified in endometriotic foci. In all cases, they are associated with areas of extracellular matrix breakdown. This paper reviews the literature on the regulation by estradiol and progesterone of the expression and activation of MMPs, and of the expression of their tissue inhibitors (TIMPs), (i) in the endometrium in situ during normal cycle, (ii) during artificial cycles in spayed monkeys, and (iii) in cultures of endometrial explants or purified cells. Whereas progesterone consistently decreases the activity of endometrial MMPs, its effects vary in intensity, duration, and pattern between MMPs as well as among experimental systems. The contribution and limitations of the various investigations are therefore discussed. The focal heterogeneity points to additional local controls of the expression and activation of MMPs in human endometrium, acting beyond the general inhibitory role of progesterone, for example, by cytokines. Focal changes in type or abundance of sex steroid receptors also could be responsible for spatial variation in the expression of MMPs in the endometrium and endometriotic lesions.

The role of insulin-like growth factor binding protein-1 phosphoisoforms in pregnancies with impaired placental function identified by doppler ultrasound

This study was performed to investigate the hypothesis that insulin-like growth factor binding protein-1 (IGFBP-1) is involved in the pathogenesis of trophoblast invasion and impaired placentation in human pregnancy. The role of total and non-phosphorylated IGFBP-1 in women with fetal growth restriction and in high risk pregnancies identified by uterine artery Doppler ultrasound screening was examined. This was a prospective study of women booked for antenatal care having second trimester anomaly scans and Doppler screening between 22-26 weeks gestation. Women were divided into three groups and compared: normal uterine artery Doppler and normal fetal growth (control group, n = 10); abnormal Doppler and normal fetal growth [bilateral uterine artery notches (BN; n = 16); abnormal Doppler and intrauterine growth restriction (IUGR; n = 8)]. Maternal serum was collected, stored and assayed simultaneously for total and non-phosphorylated IGFBP-1. There was elevated total and non-phosphorylated IGFBP-1 (mean 44.99 +/- 12.19 and 29.61 +/- 10.38 microg/l respectively) in the IUGR group compared with controls (mean 17.96 +/- 3.24 and 12.18 +/- 1.55 microg/l, P < 0.05). This finding suggests that the various IGFBP-1 isoforms, the degree of phosphorylation and the ratios of these different forms locally may be important during trophoblast invasion and may be implicated in clinical manifestations of impaired placentation later in the second trimester.

Menstruation: induction by matrix metalloproteinases and inflammatory cells

Menstruation occurs at the end of a normal reproductive cycle in the human female, following the fall in progesterone resulting from the demise of the corpus luteum. Current data support a central role for the matrix metalloproteinases in menstruation but their focal pattern of expression within peri-menstrual and menstrual endometrium suggests local rather than hormonal regulation. This review emphasizes the similarities between menstruation and an inflammatory process and examines the relationship between cells of hemopoietic lineage, particularly mast cells, eosinophils, neutrophils and macrophages, and the local production and activation of matrix metalloproteinases within the endometrium. It proposes a complex of critical regulatory circuits, initially activated by the withdrawal of progesterone, which provide interactions between the migratory cells that produce a myriad of important regulatory molecules and endometrial stromal and epithelial cells which produce both chemokines and matrix metalloproteinases. These mechanisms could account for the focal nature of the tissue degradation at menstruation.

Transcription factors Ets1, Ets2, and Elf1 exhibit differential localization in human endometrium across the menstrual cycle and alternate isoforms in cultured endometrial cells

To better understand the transcriptional regulation of human endometrial remodeling, the localization of three members of the Ets family of transcription factors was examined at different stages of the menstrual cycle. Elf1 was found by immunohistochemistry to be predominantly localized to the glandular epithelium. In contrast, Ets1 and Ets2 were found at lower intensities in both glandular epithelial and stromal cells. Low expression during the menstrual phase of the cycle, and high expression and intensity of staining in decidualized stromal cells of the late secretory phase were common to Ets1, Ets2, and Elf1. These localization patterns were confirmed in cultured human endometrial stromal and epithelial cells by Western blotting, which also demonstrated different isoforms and phosphorylation products of Ets1 and Ets2 in the two cell types. This study has shown for the first time that members of the Ets family of transcription factors, previously found predominantly during development and in hematopoietic cells, are expressed in the human endometrium and display cell and cycle-stage specificity. Expression of Elf1 predominantly in the glandular epithelium may indicate that Elf1 plays a unique role in epithelium-specific gene regulation in the endometrium.

N5 endometrial stromal cell line: a model system to study decidual prolactin gene expression

Prolactin gene expression in extrapituitary tissues, such as decidua and lymphocytes, is regulated by a distinct promoter approximately 6 kb upstream of the pituitary prolactin gene transcription start site. Here we describe studies in a human endometrial stromal cell line, N5, that was immortalized by transfection with an SV40 mutant and which expresses the prolactin gene driven by the extrapituitary promoter. The N5 cells have phenotypic features of primary cultures of decidualized human endometrial stromal cells and secrete low levels of prolactin and insulin-like growth factor binding protein-1 (IGFBP-1), both of which are markers of decidualized endometrial stromal cells. As in primary cultures of endometrial stromal cells, treatment of N5 cells with progesterone and estradiol alone or in combination with prostaglandin E2 stimulated the synthesis and release of prolactin. Transient transfection of the N5 cells with an expression vector containing - 2927/ + 66 bp of the decidual prolactin promoter coupled to a luciferase reporter gene resulted in a 20 to 25-fold increase in luciferase activity, a magnitude similar to that which occurs in primary cultures of endometrial stromal cells decidualized in vitro by treatment with progesterone and estradiol. Luciferase expression levels were similar in untreated N5 cells and N5 cells treated with progesterone and estradiol. Taken together, these results indicate that the N5 human endometrial stromal cell line has phenotypic characteristics of normal decidualized stromal cells and is a useful model to study regulation of decidual prolactin gene expression.

Relaxin secretion by human granulosa cell culture is predictive of in-vitro fertilization-embryo transfer success

We have developed a cell culture system for human luteinizing granulosa cells which supports the timely and dynamic secretion of oestrogen, progesterone and relaxin in patterns that mimic serum concentrations of these hormones during the luteal phase of the menstrual cycle. There was a wide variation in the amount of relaxin secreted by the cultured cells for the 69 patients studied. As relaxin production was generally maximal by day 10 of culture, comparisons were made at this time point. It was observed that most of the conceptions occurred in patients with higher relaxin secretion in vitro. All cycles with relaxin > 800 pg/ml on day 10 had a term pregnancy while only 13% of cycles with relaxin < 200 pg/ml had term pregnancies. A limited number of cycles from donor/recipient cycles did not show similar results. Steroid concentrations were not predictive of conception. These results demonstrated that in-vitro production of relaxin is predictive of implantation success in in-vitro fertilization (IVF)-embryo transfer cycles. This supports the hypothesis that relaxin may be involved in implantation and that lowered relaxin concentrations may be a partial cause of poor pregnancy rates after IVF.

Current concepts of the mechanisms of menstruation: a normal process of tissue destruction

Current data support the contention that menstruation is the consequence of the actions of matrix metalloproteinases (MMPs) in the endometrium, and that these enzymes are stimulated by the products of an inflammatory process. A number of MMPs, capable of degrading both interstitial matrix and basement membrane components, have been localized to perimenstrual endometrium, and the focal nature of their production suggests local regulation. Emphasis is placed on important relationships between cells of the immune system (specifically, mast cells, eosinophils, neutrophils and macrophages), and the local production and activation of MMPs, whose degradative actions lead to loss of integrity of blood vessels, destruction of endometrial interstitial matrix and the resultant bleeding characteristic of menstruation.

Paracrine actions of insulin-like growth factors and IGF binding protein-1 in non-pregnant human endometrium and at the decidual-trophoblast interface

Insulin-like growth factors, IGF-I, IGF-II, and IGF binding protein (IGFBP-1) appear to play major roles in endometrial development during the menstrual cycle and in the process of implantation. The mitogenic, differentiative, and anti-apoptotic properties of these growth factors, as well as their spatial and temporal expression in cycling endometrium, suggest that they may participate in endometrial growth, differentiation, inhibition of apoptosis, and perhaps angiogenesis. IGFBP-1 is a major protein product of non-pregnant endometrium during the mid-late secretory phase and occurs in abundance in decidua. Its roles as an IGF-binding protein and as a trophoblast integrin ligand suggest that it may have multiple roles in endometrial development and in interactions between the decidua and the invading trophoblast. Precise elucidation of the mechanisms underlying IGF and IGFBP-1 action at the decidual-trophoblast interface in early pregnancy awaits further investigation. The future also awaits elucidation of the potential predictive utility of IGFBP-1 in serum and in decidua in, for example, pre-eclampsia and perhaps implantation failure.

Differentiation-dependent and cell-specific regulation of the hIGFBP-1 gene in human endometrium

We analyzed IGFBP-1 gene promoter activity by transient transfection during the progressive decidualization of human endometrial stromal cells. A time study over a 13-day culture period showed that the promoter activity increased exponentially to > 10(4) fold in cells treated with MPA and RLX correlating with the secretion rate and steady-state mRNA levels of the endogenous gene. Deletion analysis showed that two regions in the IGFBP-1 gene promoter are responsible for the activation of the IGFBP-1 gene. The basal promoter region between -1 and -300 bp contains multiple sections of functional elements homologous either to CRE, PRE, or CCAAT. The major difference of IGFBP-1 gene activation in endometrium and the hepatic system lies in the distal promoter region, between -2.6 and -3.4 kb, which mediates 95% of the total promoter activity derived from -3.3 kb to +68 bp. Functional and binding analysis in the distal promoter region showed that multiple Sp1 elements interacting with a novel Sp3 transcription factor activates the hIGFBP-1 gene promoter.

Multifaceted roles for IGFBP-1 in human endometrium during implantation and pregnancy

IGFBP-1 is a major protein product of nonpregnant endometrium during the mid-late secretory phase and occurs in abundance in decidua. Its roles as an IGF-binding protein and as a trophoblast integrin ligand suggest that it may have multiple roles in endometrial development and in interactions between the decidua and the invading trophoblast. IGFBP-1 in vaginal/cervical secretions has already had clinical application as a predictor of premature rupture of fetal membranes. The future awaits elucidation of the potential utility of IGFBP-1 in serum and in decidua in predicting fetal growth restriction and preeclampsia and perhaps implantation failure.

Progesterone receptor (PR) inhibits expression of insulin-like growth factor-binding protein-1 (IGFBP-1) in human endometrial cell line HEC-1B: characterization of the inhibitory effect of PR on the distal promoter region of the IGFBP-1 gene

Progestin has been shown to have both stimulatory and inhibitory effects on the expression of insulin-like growth factor binding protein-1 (IGFBP-1) in human endometrial cells. In this study, progestin was found to reduce levels of secreted IGFBP-1 and IGFBP-1 messenger RNA and IGFBP-1 promoter activity after stably transfecting a progesterone receptor (PR; B form) expression vector into HEC-1B cells. Deletion analysis of the IGFBP-1 promoter revealed that PR specifically inhibited promoter activity derived from a 59-bp distal BsaHI/RsaI fragment. It was concluded that PR inhibited the promoter activity through protein-protein interactions based on the facts that 1) no progesterone-responsive element was revealed by a series block mutation in the BsaHI/RsaI fragment; 2) PR bound by the antiprogesterone ZK98299 inhibited IGFBP-1 promoter activity; 3) a DNA-binding mutant of PR inhibited the IGFBP-1 promoter activity; and 4) in an in vivo competition assay, the DNA-binding domain of PR did not release the inhibitory effect of intact PR. Analysis of PR deletion mutants indicated that both transcriptional activation domains of PR (TAF-1 and TAF-2) were involved in the inhibition of IGFBP-1 expression. Thus, our data may explain the superinduction of IGFBP-1 in human endometrial cells after progestin withdrawal or progestin replacement with antiprogestin.

The role of relaxin in glycodelin secretion

Glycodelin is a glycoprotein named for its unique carbohydrate structure. Glycodelin is produced by the secretory endometrium during the late luteal phase and returns to baseline during menses of the ensuing cycle, whereas in conceptive cycles it rapidly increases. Although progesterone and possibly estradiol are required for glycodelin production, they are not directly involved in the synthesis and release of this protein. Their role may be development of the endometrial secretory glandular elements, whereas other factors are required to initiate and maintain glycodelin secretion. The pattern of relaxin secretion during the luteal phase and early pregnancy is similar to that of glycodelin, but their profiles have not been determined simultaneously. To investigate the relationship of relaxin and glycodelin, two studies were conducted. In the first study, relaxin, glycodelin, and ovarian steroids were measured in daily serum samples from nonconceptive and conceptive natural cycles. Profiles of relaxin and glycodelin were closely associated, with the onset of relaxin preceding glycodelin secretion by 1-2 days in nonconceptive cycles, and the pregnancy-associated increases in each hormone differing by about 2 days. The second study tested the hypothesis that relaxin stimulates glycodelin secretion. Samples were obtained from patients injected with human relaxin for 28 days. In subjects demonstrating ovarian cyclicity, glycodelin secretion was elevated, but it was not detected in subjects without ovarian cyclicity or in placebo-treated control subjects. This study reveals a close temporal and quantitative relationship between relaxin and glycodelin profiles in the late luteal phase and early pregnancy. It also demonstrates that relaxin administration can stimulate glycodelin production from a developed endometrium. This is the first report of a nonsteroidal ovarian factor that controls glycodelin secretion, and these results suggest a function for relaxin during early pregnancy. Glycodelin is a potent inhibitor of sperm zona pellucida binding by virtue of its extensive carbohydrate structure, but it is normally at a nadir in the periovulatory period. The data demonstrate that relaxin can stimulate glycodelin secretion throughout the menstrual cycle, including the periovulatory period, when relaxin-induced glycodelin secretion could have a contraceptive effect.