Inhibins and activins: clinical advances in reproductive medicine

INHBB is a novel prognostic biomarker and correlated with immune infiltrates in gastric cancer

Inhibin subunit beta B (INHBB) is a potential prognostic biomarker for a variety of cancers. However, its role in gastric cancer (GC) remains elusive. The differential expression data of INHBB in tumor and normal tissues were extracted from several databases and genetic alterations of INHBB were assessed by cBioPortal. Kaplan-Meier analysis was used to evaluate the survival rate of patients with GC with INHBB and association with clinical features in GC. Cox regression analysis was used to explore the prognostic value of clinical indicators and INHBB in GC, and a nomogram prognostic model was established. In addition, the predictive validity of the nomogram model was assessed by time-depended receiver operating characteristic (ROC) and calibration curves. Functional enrichment analyses were conducted to functionally annotate INHBB. Notably, we found that the quantitative assessment of immune cell subpopulation infiltration correlated with INHBB expression. INHBB expression is upregulated in GC and is correlated with several clinical features including prognostic indicators and a histological type. Genetic alterations were observed in INHBB, its DNA methylation level was negatively correlated with INHBB expression. High INHBB expression is associated with a poor prognosis and is an independent risk factor for prognosis in GC, along with age and residual tumor. The nomogram model showed a good prediction ability and was validated by time-depended ROC and calibration curves. Functional enrichment analysis indicated that INHBB-associated genes were enriched in tumor microenvironment Gene Ontology (GO) terms and were correlated with tumor-associated pathways. INHBB has a regulatory function in immune cell infiltration, especially macrophage infiltration in GC. Specifically, patients with GC with high INHBB expression and high macrophage infiltration have a worse prognosis. INHBB expression was negatively correlated with the expression of chemokines/chemokine receptors and plays a regulatory role in immunoinhibitor/immunostimulator-involved pathways. INHBB is a potential prognostic biomarker for GC and may drive the abnormal activity of critical cancer-associated pathways, potentially contributing to immune cell infiltration to promote GC development.

Serum Inhibin-A and PAPP-A2 in the prediction of pre-eclampsia during the first and second trimesters in high-risk women

OBJECTIVES

Maternal serum inhibin-A, pregnancy associated plasma protein-A (PAPP-A) and PAPP-A2 together with placental growth factor (PlGF), maternal risk factors and uterine artery pulsatility index (UtA PI) were analysed to study their ability to predict pre-eclampsia (PE).

STUDY DESIGN

Serial serum samples for the nested case-control study were collected prospectively at 12-14, 18-20 and 26-28 weeks of gestation from 11 women who later developed early-onset PE (EO PE, diagnosis < 34 + 0 weeks of gestation), 34 women who developed late-onset PE (LO PE, diagnosis ≥ 34 + 0 weeks) and 89 controls.

MAIN OUTCOME MEASURES

Gestational age -adjusted multiples of the median (MoM) values were calculated for biomarker concentrations. Multivariate regression analyses were performed to combine first trimester biomarkers, previously reported results on PlGF, maternal risk factors and UtA PI. Area under curve (AUC) values and 95% confidence intervals (CIs) for the prediction of PE and its subtypes were calculated.

RESULTS

A high first trimester inhibin-A predicted PE (AUC 0.618, 95%CI, 0.513-0.724), whereas PAPP-A and PlGF predicted only EO PE (0.701, 0.562-0.840 and 0.798, 0.686-0.909, respectively). At 26-28 weeks PAPP-A2 and inhibin-A predicted all PE subtypes. In the multivariate setting inhibin-A combined with maternal pre-pregnancy body mass index, prior PE and mean UtA PI predicted PE (0.811,0.726-0.896) and LO PE (0.824, 0.733-0.914).

CONCLUSIONS

At first trimester inhibin-A show potential ability to predict not only EO PE but also LO PE whereas PlGF and PAPP-A predict only EO PE. At late second trimester inhibin-A and PAPP-A2 might be useful for short-term prediction of PE.

Mouse Models for the Study of Synthesis, Secretion, and Action of Pituitary Gonadotropins

Gonadotropins play fundamental roles in reproduction. More than 30years ago, Cga transgenic mice were generated, and more than 20years ago, the phenotypes of Cga null mice were reported. Since then, numerous mouse strains have been generated and characterized to address several questions in reproductive biology involving gonadotropin synthesis, secretion, and action. More recently, extragonadal expression, and in some cases, functions of gonadotropins in nongonadal tissues have been identified. Several genomic and proteomic approaches including novel mouse genome editing tools are available now. It is anticipated that these and other emerging technologies will be useful to build an integrated network of gonadotropin signaling pathways in various tissues. Undoubtedly, research on gonadotropins will continue to provide new knowledge and allow us transcend from benchside to the bedside.

Use of detergent-based buffers allows detection of precursor inhibin forms in an immunoassay format

Inhibin ELISAs are used in monitoring aspects of reproductive function, however these assays are based on the measurements of the mature 30kDa inhibin forms and not precursor forms. In conventional ELISA formats, the 105kDa unprocessed 'Pro-inhibin' forms are immunologically inactive, but the immunoactivity can be recovered in the presence of detergents. The immunoactivity of Pro-inhibin forms was assessed in the presence of a range of detergents utilising antibodies to the α-, βA- and βB-subunits of inhibin. In contrast to mature forms, unprocessed inhibin forms showed a 10-40 fold increase in inhibin A and total inhibin immunoactivities under optimised detergent (0.5% SDS/2% Triton X-100) conditions. The suppressed immunoactivity of the Pro-inhibin forms in these immunoassays was attributed to steric hindrance by the respective βA- and α-subunit prodomains. This study details a detergent-based immunoassay that allows detection of previously undetectable precursor inhibin forms.

Inhibins and activins in blood: predictors of female reproductive health?

Inhibins A and B are gonadal factors which are important in fertility. Their use as predictors of female reproductive health has centred on their application to ovarian cancer, Anorexia Nervosa, Down Syndrome and preeclampsia. Inhibin B also provides an index of the endocrine feedback relationship between the ovary and pituitary particularly when the ovarian follicle reserve is low. These applications are relevant in monitoring the onset of the menopause transition, ovarian recovery following chemotherapy and disturbances in pubertal development. Currently, these applications have only found widespread use in Down Syndrome and ovarian cancer. Activins, on the other hand, appear to have a limited application.

Activin A as a marker of intrauterine infection in women with preterm prelabour rupture of membranes

OBJECTIVE

To assess maternal serum activin A, an early phase response protein in systemic infection, as an early marker of intrauterine infection in women with preterm prelabour rupture of membranes (PPROM).

STUDY DESIGN

A prospective cohort study of women with singleton pregnancies complicated by PPROM at 24 to 34 weeks' gestation. Serum was collected for activin A and cytokine measurements. Activin A was measured using commercial enzyme-linked immunosorbent assay. Cytokines were measured using commercial multiplex assay. Pregnancy outcomes including infection were determined by case-record review.

RESULT

Eighteen women with PPROM were studied, with seven developing intrauterine infection. Serum activin A in women with and without infection did not differ. Peripheral white cell count, interleukin (IL)-6 and IL-10 were higher (P=0.03, 0.05 and 0.009, respectively) and IL-7 lower (P=0.04) 72 h before delivery in women with infection.

CONCLUSION

Activin A is not a clinically useful marker of intrauterine infection in women with PPROM.

Activin-A: a novel dendritic cell–derived cytokine that potently attenuates CD40 ligand–specific cytokine and chemokine production

Activin-A is a transforming growth factor-β (TGF-β) superfamily member that plays a pivotal role in many developmental and reproductive processes. It is also involved in neuroprotection, apoptosis of tumor and some immune cells, wound healing, and cancer. Its role as an immune-regulating protein has not previously been described. Here we demonstrate for the first time that activin-A has potent autocrine effects on the capacity of human dendritic cells (DCs) to stimulate immune responses. Human monocyte-derived DCs (MoDCs) and the CD1c+ and CD123+ peripheral blood DC populations express both activin-A and the type I and II activin receptors. Furthermore, MoDCs and CD1c+ myeloid DCs rapidly secrete high levels of activin-A after exposure to bacteria, specific toll-like receptor (TLR) ligands, or CD40 ligand (CD40L). Blocking autocrine activin-A signaling in DCs using its antagonist, follistatin, enhanced DC cytokine (IL-6, IL-10, IL-12p70, and tumor necrosis factor-α [TNF-α]) and chemokine (IL-8, IP-10, RANTES, and MCP-1) production during CD40L stimulation, but not TLR-4 ligation. Moreover, antagonizing DC-derived activin-A resulted in significantly enhanced expansion of viral antigen-specific effector CD8+ T cells. These findings establish an immune-regulatory role for activin-A in DCs, highlighting the potential of antagonizing activin-A signaling in vivo to enhance vaccine immunogenicity.

Essential roles of inhibin beta A in mouse epididymal coiling

Testis-derived testosterone has been recognized as the key factor for morphogenesis of the Wolffian duct, the precursor of several male reproductive tract structures. Evidence supports that testosterone is required for the maintenance of the Wolffian duct via its action on the mesenchyme. However, it remains uncertain how testosterone alone is able to facilitate formation of regionally specific structures such as the epididymis, vas deferens, and seminal vesicle from a straight Wolffian duct. In this study, we identified inhibin beta A (or Inhba) as a regional paracrine factor in mouse mesonephroi that controls coiling of the epithelium in the anterior Wolffian duct, the future epididymis. Inhba was expressed specifically in the mesenchyme of the anterior Wolffian duct at embryonic day 12.5 before the production of androgens. In the absence of Inhba, the epididymis failed to develop the characteristic coiling in the epithelium, which showed a dramatic decrease in proliferation. This loss of epididymal coiling did not result from testosterone deficiency, because testosterone production and parameters for testosterone action such as testis descent and anogenital distance remained normal. We further found that initial Inhba expression did not require testosterone as Inhba was also expressed in the anterior Wolffian duct of female embryos where no testosterone was produced. However, Inhba expression at later stages depended on testosterone. These results demonstrated that Inhba, a mesenchyme-specific gene, acts collectively with testosterone to facilitate epididymal coiling by stimulating epithelial proliferation.

Highly specific and sensitive rise in Days 14–17 pro-αC inhibin with clinical pregnancy after frozen embryo transfer with ovulatory cycles

BACKGROUND

Pro-alphaC inhibins are luteal derived analytes peaking in the maternal serum as early as Day 16 after conception. We set out to verify a previous post hoc analysis which suggested that pro-alphaC levels measured this early are extremely sensitive in predicting clinical pregnancy success after unstimulated IVF with ovulatory cycles.

METHODS

Prospective observational study of 246 women undergoing frozen embryo transfer with ovulatory cycles. Serum pro-alphaC and beta-HCG levels at 14-17 days after conception were measured by enzyme-linked immunosorbent assay and grouped according to whether a clinical pregnancy occurred (demonstrable cardiac activity at > or =6 weeks' gestation).

RESULTS

Of 34 (13.8%) women who achieved a clinical pregnancy, median (25th-75th centile) Days 14-17 pro-alphaC levels were 995 pg/ml (758-1463), 6- to 7-fold higher than levels observed in the remainder who did not fall pregnant (112.8 pg/ml (104-121); P < 0.0001). At a fixed 95% specificity, pro-alphaC was 100% sensitive in predicting clinical pregnancy. The best specificities achieved at 100% sensitivity were; 94.8% for pro-alphaC, 96.7% for beta-HCG and 98.1% when both analytes were combined.

CONCLUSIONS

Clinical pregnancy is always associated with a release of luteal derived pro-alphaC 14-17 days after conception. Pro-alphaC may play a possible biological role and be a useful clinical biomarker of luteal health.

Reproductive ageing in women

The traditional view in respect to female reproduction is that the number of oocytes at birth is fixed and continuously declines towards the point when no more oocytes are available after menopause. In this review we briefly discuss the embryonic development of female germ cells and ovarian follicles. The ontogeny of the hypothalamic-pituitary-gonadal axis is then discussed, with a focus on pubertal transition and normal ovulatory menstrual cycles during female adult life. Biochemical markers of menopausal transition are briefly examined. We also examine the effects of age on female fertility, the contribution of chromosomal abnormalities of the oocyte to the observed decline in female fertility with age and the possible biological basis for the occurrence of such abnormalities. Finally, we consider the effects of maternal age on obstetric complications and perinatal outcome. New data that have the potential to revolutionize our understanding of mammalian oogenesis and follicular formation, and of the female reproductive ageing process, are also briefly considered.

Mutational analysis of BMP15 and GDF9 as candidate genes for premature ovarian failure

Mutational screening of the bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) genes in a population with premature ovarian failure (POF) identified no new mutations. However, three single nucleotide polymorphisms in the BMP15 gene, two in the 5' untranslated region (31T>G and 71C>G) and another in exon 1 (387G>A), were found to be common in both POF and control groups.

Pituitary actions of ligands of the TGF-β family: activins and inhibins

Activins, as members of the transforming growth factor-β superfamily, control and orchestrate many physiological processes and are vital for the development, growth and functional integrity of most tissues, including the pituitary. Activins produced by pituitary cells work in conjunction with central, peripheral, and other local factors to influence the function of gonadotropes and maintain a normal reproductive axis. Follistatin, also produced by the pituitary, acts as a local buffer to bind activin and modulate its bioactivity. On the other hand, inhibins of gonadal origin provide an endocrine feedback signal to antagonize activin signaling in cells that express the inhibin co-receptor, betaglycan, such as gonadotropes. This review highlights the pituitary roles of activin and the mechanisms through which these actions are modulated by inhibin and follistatin.

Sexually dimorphic regulation of inhibin beta B in establishing gonadal vasculature in mice

Sexually dimorphic differentiation of gonads is accomplished through balanced interactions between positive and negative regulators. One of the earliest features of gonadal differentiation is the divergent patterning of the vasculature. A male-specific coelomic vessel develops on the anterior to posterior of the XY gonad, whereas this vessel is absent in XX gonads. It is postulated that the testis-determining gene Sry controls formation of the coelomic vessel, but the exact molecular mechanism remains unknown. Here we reveal a novel role for inhibin beta B in establishing sex-specific gonad vasculature. In the testis, inhibin beta B contributes to proper formation of the coelomic vessel, a male-specific artery critical for testis development and, later in development, hormone transportation. On the other hand, in the ovary, inhibin beta B is repressed by WNT4 and its downstream target follistatin, leading to the absence of the coelomic vessel. When either Wnt4 or follistatin was inactivated, the coelomic vessel appeared ectopically in the XX ovary. However, when inhibin beta B was also removed in either the Wnt4-null or follistatin-null background, normal ovarian development was restored and no coelomic vessel was found. Our results indicate that the sex-specific formation of the coelomic vessel is established by positive components in the testis as well as an antagonizing pathway from the ovary. Inhibin beta B is strategically positioned at the intersection of these opposing pathways.

Chronic fetal hypoxia increases activin A concentrations in the late-pregnant sheep

OBJECTIVE

To determine whether activin A concentrations are altered in chronic fetal hypoxemia and intrauterine fetal growth restriction (IUGR).

DESIGN

In vivo animal experimental model.

SETTING

Department of Physiology, Monash University.

POPULATION

Chronically catherised fetal sheep in late pregnancy.

METHODS

Chronic fetal hypoxia and IUGR were experimentally induced by single umbilical artery ligation (SUAL) in catheterised fetal sheep. Maternal and fetal blood samples and amniotic fluid (AF) samples were collected during surgery and thereafter on alternate days, until the time of delivery for analyte measurement. Fetal blood gas parameters were measured daily.

MAIN OUTCOME MEASURES

Plasma and AF was used to analyse activin A, prostaglandin E2 (PGE2) and cortisol and fetal blood gas analysis was undertaken in whole blood.

RESULTS

SUAL produced asymmetric IUGR and non-acidaemic chronic fetal hypoxia and resulted in preterm labour (129 [3] days). AF activin A concentrations were 10-fold higher in the SUAL group than in controls whereas levels in the fetal and maternal circulations were similar between groups.

CONCLUSIONS

SUAL-induced IUGR and fetal hypoxaemia increases AF activin A. This may be an important adaptive or protective response to IUGR.

Activin receptor expression and induction of apoptosis in rat blastocysts in vitro

BACKGROUND

Apoptosis, a process of normal embryonic development, is enhanced in blastocyst from diabetic rats. Nevertheless, glucose seems not to be the only factor involved. Activin A, a TGF-beta family member, is also increased in maternal serum from diabetic pregnancy.

METHODS

Flushing medium, blastocysts and uterine cells were obtained from 5 day old pregnant rats. The presence of activin A in flushing medium was investigated by western blotting. RT-PCR was used to test for the presence of activin betaA subunit mRNA in cultured uterine cells. Blastocysts were stained by immunohistochemistry for activin receptor types IIA and IIB, and chromatin degradation (apoptosis) was investigated by terminal transferase-mediated dUTP nick end labelling in blastocysts exposed in vitro to activin.

RESULTS

In this study, we demonstrate the presence of activin A protein in fluid from rat uterine horns at day 5 of pregnancy, as well as the presence of activin A receptors type IIB in the trophectoderm and inner cell mass and activin A receptor type IIA in trophectoderm cells only. Activin A increases the chromatin degradation level in vitro.

CONCLUSIONS

Activin A protein was found in fluid from uterine horns, and mRNA expression of betaA activin subunit in cultured uterine cells suggests probable secretion from decidual cells. Moreover, activin A increases specifically the apoptosis level in rat blastocyst in vitro.

Activin A: From sometime reproductive factor to genuine cytokine

The growth factor, activin A, was initially characterized as a putative reproductive hormone but is now known to have many other divergent roles. One of these is during inflammation. Following intravenous injection of bacterial lipopolysaccharide (LPS) into sheep, activin A is released extremely rapidly into the circulation. The release of activin A appears to be independent of fever, prostaglandins or other key proinflammatory cytokines such as TNF-alpha or IL-1beta. While the precise roles and function of this factor in inflammation are yet to be elucidated, the activin response occurs in other mammalian species besides the sheep and elevated activin has been documented for a number of clinical inflammatory conditions. Activin A therefore seems to be part of the regulatory component of the innate immune response.

Hormone therapy and Alzheimer’s disease: benefit or harm?

Alzheimer's disease (AD) is the most common cause of dementia. After menopause, circulating levels of oestrogens decline markedly and oestrogen influences several brain processes predicted to modify AD risk. For example, oestrogen reduces the formation of beta-amyloid, a biochemical hallmark of AD. Oestrogen effects on oxidative stress and some effects on inflammation and the cerebral vasculature might also be expected to ameliorate risk. However, AD pathogenesis is incompletely understood and other oestrogen actions could be deleterious. Limited clinical trial evidence suggests that oestrogen therapy, begun after the onset of AD symptoms, is without substantial benefit or harm. Observational studies have associated oestrogen-containing hormone therapy with reduced AD risk. However, in the Women's Health Initiative Memory Study - a randomised, placebo-controlled trial of women 65 - 79 years of age - oral oestrogen plus progestin doubled the rate of dementia, with heightened risk appearing soon after treatment was initiated. Based on current evidence, hormone therapy is thus not indicated for the prevention of AD. Discrepancies between observational studies and the Women's Health Initiative clinical trial may reflect biases and unrecognised confounding factors in observational reports. Other explanations for divergent findings should be considered in future research, including effects of unopposed oestrogen or different hormone therapy preparations and the intriguing theoretical possibility that effects of hormone therapy on AD risk may be modified by the timing of use (e.g., initiation during the menopausal transition or early postmenopause versus initiation during the late postmenopause).

Fertility in female cancer survivors: pathophysiology, preservation and the role of ovarian reserve testing

The improved long-term survival of adolescents and young women treated for cancer has resulted in an increased focus on the effects of chemotherapy on ovarian function and its preservation. These women may seek advice and treatment regarding their reproductive status, including ways of preserving their fertility and preventing a premature menopause--factors that can have a profound impact on their quality of life. This article comprehensively reviews ovarian reserve testing (ORT) in general. Special emphasis is placed on patients with cancer, including the pathophysiology of gonadal damage following chemotherapy, fertility preservation and the potential role of ORT. Baseline parameters of ovarian reserve [FSH LH, estradiol, inhibin B and anti-Mullerian hormone (AMH)] have not yet performed sufficiently well in predicting poor outcome in assisted reproduction, but biochemical markers of ovarian reserve appear to be better than chronological age. Inhibin B and AMH show potential for future use. Dynamic testing appears to show much promise, especially stimulated levels of inhibin B and estradiol. The most promising tests of ovarian reserve are the biophysical markers, where total antral follicle count was found to be most discriminatory followed by ovarian volume. Combination of biochemical, biophysical and clinical markers of ovarian reserve may also improve predictive capacity. However, there is a lack of data pertinent to ORT in cancer. As yet there is no single clinically useful test to predict ovarian reserve accurately. Patients with cancer represent a distinct cohort who have particular concerns about their future fertility and the possibility of a premature menopause, they can benefit greatly from knowledge of their functional ovarian reserve. Large, prospective, randomized, adequately controlled studies specific to different geographical areas are required in a control population of comparable reproductive age to determine the potential role of ORT in clinical practice.

Fetal activin A: associations with labour, umbilical artery pH and neonatal outcome

OBJECTIVE

To define the ontogeny of umbilical artery activin A at term and to evaluate activin A as a potential marker of perinatal hypoxia.

DESIGN

A cohort study.

SETTING

A university teaching hospital delivery suite.

POPULATION

A convenience sample of 141 term pregnancies.

METHODS

At delivery, umbilical artery and vein bloods were collected for blood gas measurements and subsequent measurement of activin A. Activin A levels were correlated with blood gas measurements and with labour and neonatal outcomes.

MAIN OUTCOME MEASURES

Umbilical arterial activin A and pH.

RESULTS

The median (95% CI) umbilical arterial activin A level at delivery was 1.38 (1.34-1.70) ng/mL. Levels varied significantly across gestation (P= 0.03), increasing from 36 to 38 weeks, thereafter decreasing to a nadir at 41 weeks. In 60 matched samples, the median (95% CI) venous and arterial activin A levels were 0.89 (0.81-1.06) ng/mL and 1.38 (1.21-1.61) ng/mL, respectively (P < 0.0001). Mean umbilical arterial pH was 7.20 (7.06-7.38; 5-95th centiles) and was not significantly correlated with log10 activin A (r=- 0.01; P= 0.68). Compared with healthy controls, there was no difference in arterial activin A in neonates identified as having suffered significant intrapartum asphyxia (P= 0.96). Fetal activin A levels were significantly lower in cases delivered by emergency caesarean section for complications during the first stage of labour compared with cases delivered vaginally (P= 0.003).

CONCLUSIONS

Umbilical artery activin A does not appear to be a sensitive marker of fetal oxygenation or of risk of hypoxic-ischaemic encephalopathy.

First trimester levels of inhibins and activin A in normal and failing pregnancies

OBJECTIVE

Miscarriage is the commonest complication of human pregnancy. We undertook this study to assess whether inhibin A, pro-alphaC inhibin and/or activin A, products of the corpus luteum and placenta, might be useful in either the prediction or diagnosis of miscarriage.

DESIGN

Case-control study.

PATIENTS

Ninety-eight asymptomatic women at 6-13 weeks gestation who subsequently had a miscarriage and 198 gestation-matched women with a normal singleton pregnancy.

MEASUREMENTS

Maternal serum levels of inhibin A, pro-alphaC inhibin, activin A and human chorionic gonadotrophin (hCG) were measured.

RESULTS

Inhibin A, pro-alphaC and hCG, expressed as multiples of the normal median (MoM; +/-95% confidence intervals) in the miscarriage cases were significantly lower than in the viable controls, 0.56 (0.48-0.69) MoM vs. 1.00 (0.98-1.13) MoM, 0.55 (0.51-0.84) MoM vs. 1.0 (0.86-1.22) MoM and 0.34 (0.23-0.36) MoM vs. 1.00 (0.94-1.08) MoM, respectively (P < 0.0001 for all). Of the three analytes, hCG was the most discriminating between cases and controls. Levels of activin A in the miscarriage cases were not significantly different from controls, 0.96 (0.86-1.07) vs. 1.0 (0.95-1.08).

CONCLUSIONS

These data suggest that inhibin A, pro-alphaC inhibin and activin A will not be useful in either the prediction or diagnosis of early pregnancy miscarriage.