Development of a new antibody to the human inhibin/activin βB subunit and its application to improved inhibin B ELISAs

Association of bioavailable inhibin B and oocyte yield in controlled ovarian stimulation

Objective

To determine if the biologically active or bioavailable inhibin B (bio-inhB) correlated with the oocyte yield in controlled ovarian stimulation (COS).

Design

Cross-sectional study.

Setting

Academic center.

Patient(s)

Women undergoing oocyte cryopreservation.

Intervention(s)

None.

Main Outcome Measure(s)

Serum of women were sampled to measure bio-inhB at three points: baseline (“start”); middle (“mid”); and end of COS. A validated, highly specific enzyme-linked immunosorbent assay (Ansh Labs, Webster, TX) measured bio-inhB. The Spearman tests analyzed correlations between bio-inhB and other ovarian reserve markers, including age, follicle-stimulating hormone (FSH), antral follicle count (AFC), and antimüllerian hormone (AMH), and correlations between these markers and oocyte yield.

Result(s)

A total of 144 women were included. Bioavailable inhibin B at the mid and end of COS, plus its delta, were strongly correlated with other ovarian reserve markers. As the bio-inhB concentration increased, the AFC and AMH levels also increased, whereas the FSH concentration and age decreased. Bioavailable inhibin B values, except at the start of COS, were more strongly correlated with oocyte yield than the FSH concentration (r = 0.72–0.82 vs. r = −0.44) and correlated similarly to the AFC and AMH concentration (r = 0.79 and 0.81, respectively). These correlations strengthened in those with diminished ovarian reserve, specifically age ≥35 years or AMH concentration <2 ng/mL (r = 0.71–0.86 vs. r = 0.49–0.67).

Conclusion(s)

Predicting COS outcome is imperfect. When using a highly specific enzyme-linked immunosorbent assay, bio-inhB correlated with the oocyte yield similar to or more strongly than traditionally used ovarian reserve markers. These correlations strengthened in cases of diminished ovarian reserve. Bioavailable inhibin B provides physicians with an additional clinical tool for estimating COS outcome.

Comparison of Serum Inhibin B and Follicle-Stimulating Hormone (FSH) Level between Normal and Infertile Men in Yaoundé

Objective

Hormones play a vital role in initiating and maintaining male reproductive function. The present study explores the influence and predictive ability of two reproductive hormones on semen quality among men who were partners in an infertile couple.

Design

During our cross sectional study, men were recruited from private and public hospital and laboratories for clinical evaluation of fertility status.

Methods

Fresh semen samples were assessed for quality (concentration, motility and morphology) according to the 2010 World Health Organization manual and the serum levels of hormones, including follicle-stimulating hormone (FSH), Inhibin B was measured (ELISA).

Results

We found a significant difference in the two groups regarding sperm concentration (p < 0.0001), total sperm count (p < 0.0001), total sperm count (p < 0.0001), total sperm count (p < 0.0001), total sperm count (p < 0.0001), total sperm count (

Conclusion

Consistent with other studies, our results show strong association between semen quality and FSH and Inhibin B.

In utero exposure to cigarette smoking, environmental tobacco smoke and reproductive hormones in US girls approaching puberty

BACKGROUND/AIMS

Evidence is unclear whether prenatal smoking affects age at menarche and pubertal development, and its impact upon hormones has not been well studied. We aim to identify potential pathways through which prenatal smoking and environmental tobacco smoke (ETS) affect reproductive hormones in girls approaching puberty.

METHODS

We examined the association between prenatal smoking, current ETS and luteinizing hormone (LH) and inhibin B (InB) in 6- to 11-year-old girls in the 3rd National Health and Nutrition Examination Survey, 1988-1994. Parents/guardians completed interviewer-assisted questionnaires on health and demographics at the time of physical examination. Residual blood samples were analyzed for reproductive hormones in 2008.

RESULTS

Of 660 girls, 19 and 39% were exposed to prenatal smoke and current ETS, respectively. Accounting for multiple pathways in structural equation models, prenatally exposed girls had significantly lower LH (β = -0.205 log-mIU/ml, p < 0.0001) and InB (β = -0.162, log-pg/ml, p < 0.0001). Prenatal smoking also influenced LH positively and InB negatively indirectly through BMI-for-age. ETS was positively associated with LH, but not with InB.

CONCLUSION

Exposure to maternal smoking may disrupt reproductive development manifesting in altered hormone levels near puberty.

Upregulation of activin-B and follistatin in pulmonary fibrosis - a translational study using human biopsies and a specific inhibitor in mouse fibrosis models

Background

Activins are members of the TGF-ß superfamily of growth factors. First, we identified by expression array screening that activin-B and follistatin are upregulated in human idiopathic pulmonary fibrosis (IPF). Next, we wanted to clarify their specific role in lung fibrosis formation.

Methods

We used specific antibodies for activin-A and -B subunits and follistatin to measure and localize their levels in idiopathic pulmonary fibrosis and control lung biopsies. To inhibit activin signaling, we used soluble activin type IIB receptor fused to the Fc portion of human IgG1 (sActRIIB-Fc) in two different mouse models of pulmonary fibrosis.

Results

Activin-B and follistatin mRNA levels were elevated in the human IPF lung. Immunoreactivity to activin-A, -B and follistatin localized predominantly to the hyperplastic, activated alveolar epithelium, but was also seen in inflammatory cells. Mice treated with sActRIIB-Fc showed increased skeletal muscle mass and a clear reduction in alveolar cell counts in bronchoalveolar lavage fluid, but no significant antifibrotic effect in the lung was observed.

Conclusions

The upregulation of activin-B and follistatin in IPF is a novel finding. Our results indicate that activin inhibition is not an efficient tool for antifibrotic therapy, but could be useful in reducing alveolar cellular response to injury. Activin-B and follistatin levels may be useful as biomarkers of IPF.

Inhibin at 90: from discovery to clinical application, a historical review

When it was initially discovered in 1923, inhibin was characterized as a hypophysiotropic hormone that acts on pituitary cells to regulate pituitary hormone secretion. Ninety years later, what we know about inhibin stretches far beyond its well-established capacity to inhibit activin signaling and suppress pituitary FSH production. Inhibin is one of the major reproductive hormones involved in the regulation of folliculogenesis and steroidogenesis. Although the physiological role of inhibin as an activin antagonist in other organ systems is not as well defined as it is in the pituitary-gonadal axis, inhibin also modulates biological processes in other organs through paracrine, autocrine, and/or endocrine mechanisms. Inhibin and components of its signaling pathway are expressed in many organs. Diagnostically, inhibin is used for prenatal screening of Down syndrome as part of the quadruple test and as a biochemical marker in the assessment of ovarian reserve. In this review, we provide a comprehensive summary of our current understanding of the biological role of inhibin, its relationship with activin, its signaling mechanisms, and its potential value as a diagnostic marker for reproductive function and pregnancy-associated conditions.

Inhibin B response to testicular toxicants hexachlorophene, ethane dimethane sulfonate, di-(n-butyl)-phthalate, nitrofurazone, DL-ethionine, 17-alpha ethinylestradiol, 2,5-hexanedione, or carbendazim following short-term dosing in male rats

BACKGROUND

Inhibin B is a heterodimer glycoprotein that downregulates follicle-stimulating hormone and is produced predominantly by Sertoli cells. The potential correlation between changes in plasma Inhibin B and Sertoli cell toxicity was evaluated in male rats administered testicular toxicants in eight studies. Inhibin B fluctuations over 24 hr were also measured.

METHODS

Adult rats were administered one of eight testicular toxicants for 1 to 29 days. The toxicants were DL-ethionine, dibutyl phthalate, nitrofurazone, 2,5-hexanedione, 17-alpha ethinylestradiol, ethane dimethane sulfonate, hexachlorophene, and carbendazim. In a separate study plasma was collected throughout a 24-hr period via an automatic blood sampler.

RESULTS

Histomorphologic testicular findings included seminiferous tubule degeneration, round and elongate spermatid degeneration/necrosis, seminiferous tubule vacuolation, aspermatogenesis, and interstitial cell degeneration. There was a varying response of plasma Inhibin B levels to seminiferous tubule toxicity, with three studies showing high correlation, three studies with a response only at a certain time or dose, and two studies with no Inhibin B changes. In a receiver operating characteristics exclusion model analysis, where treated samples without histopathology were excluded, Inhibin B showed a sensitivity of 70% at 90% specificity in studies targeting seminiferous tubule toxicity.

CONCLUSION

Decreases in Inhibin B correlated with Sertoli cell toxicity in the majority of studies evaluated, demonstrating the value of Inhibin B as a potential biomarker of testicular toxicity. There was no correlation between decreases in Inhibin B and interstitial cell degeneration. In addition, a pattern of Inhibin B secretion could not be identified over 24 hr.

Expression of inhibin/activin proteins and receptors in the human hypothalamus and basal forebrain

The inhibin/activin family of proteins is known to have a broad distribution of synthesis and expression in many species, as well as a variety of functions in reproductive and other physiological systems. Yet, our knowledge regarding the production and function of inhibin and activin in the central nervous system is relatively limited, especially in humans. The present study aimed to explore the distribution of inhibin/activin protein subunits and receptors in the adult human brain. The human hypothalamus and surrounding basal forebrain was examined using post-mortem tissues from 29 adults. Immunocytochemical studies were conducted with antibodies directed against the inhibin/activin α, βA, and βB subunits, betaglycan and the activin type IIA and IIB receptors. An immunoassay was also utilised to measure dimeric inhibin A and B levels in tissue homogenates of the infundibulum of the hypothalamus. Robust βA subunit immunoreactivity was present in the paraventricular, supraoptic, lateral hypothalamic, infundibular, dorsomedial and suprachiasmatic nuclei of the hypothalamus, in the basal ganglia, and in the nucleus basalis of Meynert. A similar staining distribution was noted for the βB subunit, betaglycan and the type II receptor antibodies, whereas α subunit staining was not detected in any of the major anatomical regions of the human brain. Inhibin B immunoreactivity was present in all tissues, whereas inhibin A levels were below detectable limits. These studies show for the first time that the inhibin/activin protein subunits and receptors can be co-localised in the human brain, implicating potential, diverse neural functions.

Effect of a DNA vaccine harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats

The objective was to investigate the effects of a novel DNA vaccine (pcISI) harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats. Female Wistar rats (n=18 per group) were immunized (twice, 4 wk apart) with 10, 50, or 100 μg (T1, T2 and T3, respectively), of the pcISI plasmid. At 4 wk after the second immunization, plasma antibody titers were higher (P<0.05) in T3 than in either T1 or T2 (0.341±0.123, 0.236±0.068, and 0.251±0.077, respectively, mean±SD). Concurrrently, plasma concentrations of FSH and estradiol were highest (P<0.05) in T3, and were higher (P<0.05) in T1 and T2 than in control groups. For antibody-positive rats, there was a correlation (P<0.01) between antibody titer and FSH concentrations after two pcISI immunizations. The number of mature follicles in the T3 group (46.00±4.65) was higher (P<0.05) than in two control groups (29.25±3.72 and 27.92±3.48), and also higher (P<0.05) than in T1 and T2 (37.17±4.99 and 38.75±7.09). Antibody-positive rats had more mature ovarian follicles than negative rats (46.75±4.23 vs. 35.60±3.38, P<0.05). Moreover, litter size and number of placentas were increased (P<0.05) in the pcISI immunization groups, except for the T1 group, compared to the control groups. In conclusion, the pcISI DNA vaccine successfully induced a humoral immune response, improved reproductive hormone concentrations, stimulated follicular development, and increased number of placentas and litter size. Furthermore, 100 μg yielded the best immune response.

The bioactivity of human bone morphogenetic protein-15 is sensitive to C-terminal modification: characterization of the purified untagged processed mature region

Oocyte-derived bone morphogenetic protein-15 (BMP15) is critical for the regulation of mammalian fertility. Previously we have found that a C-terminal His(6)-tag destroys the bioactivity of growth differentiation-9 (GDF9, a homolog of BMP15). In this study we found that recombinant human BMP15 is produced by HEK-293T cells in an active form, but the bioactivity is lost by C-terminal modification, specifically, fusion to a Flag tag. After purification the mature BMP15 wt is active in transcriptional reporter assays specific for Smad1/5/8 in human granulosa-luteal (hGL) and COV434 granulosa tumor cells, whereas BMP15 with a carboxy-terminal Flag tag remains inactive. Using these same cell models we found that treatment with purified mature BMP15 wt causes a rapid phosphorylation of Smad1. The purified BMP15 wt is a potent stimulator of rat granulosa cell DNA synthesis, which could be antagonized by the BMPRII ectodomain-Fc fusion molecule, whereas the BMP15C-Flag was completely inactive. Further, the BMP15 wt form is a potent stimulator of inhibin B production in hGL cells. We found that the purified BMP15 wt consists of P16 and -17, both of which are post-translationally modified forms. This is the first characterization of a purified untagged human BMP15 mature region, which is stable and highly bioactive in human and rodent granulosa cells and as such is of importance for studies on human fertility.

The synthesis and secretion of inhibins

Inhibin A and B, dimeric glycoproteins comprising an α- and β((A/B))-subunit, negatively regulate follicle stimulating hormone (FSH) synthesis by the pituitary. The expression of α- and β-subunits within Sertoli cells of the testis and granulosa cells of the ovary is controlled by a range of transcription factors, including CREB, SP-1, Smads, and GATA factors. The inhibin α- and β-subunits are synthesized as precursor molecules consisting of an N-terminal propeptide and a C-terminal mature domain. Recently, we showed that hydrophobic residues within the propeptides of the α- and β-subunits interact noncovalently with their mature domains, maintaining the molecules in a conformation competent for dimerization. Dimeric precursors are cleaved by proprotein convertases and mature inhibins are secreted from the cell noncovalently associated with their propeptides. Propeptides may increase the half-life of inhibin A and B in circulation, but they are readily displaced in the presence of the high-affinity receptors, betaglycan, and ActRII.

Luteinizing hormone, testosterone and inhibin B levels in the peripubertal period and racial/ethnic differences among boys aged 6-11 years: analyses from NHANES III, 1988-1994

OBJECTIVE

To determine whether the initial physical findings of puberty are accompanied by hormonal evidence of pubertal activation of the hypothalamic-pituitary-gonadal (HPG) axis and whether racial/ethnic differences exist, we have analysed hormone levels in relation to age, onset of puberty and race/ethnicity.

DESIGN

Cross-sectional analysis of luteinizing hormone (LH), testosterone (T) and inhibin B from banked sera from a representative sample of US boys aged 6·0-11·99 years who participated in the National Health and Nutrition Examination Survey (NHANES) III.

PATIENTS

Eight hundred and twenty-eight boys having sera including 228 non-Hispanic white (NHW), 266 non-Hispanic black (NHB), 288 Mexican-American (MA) and 46 'other'.

MEASUREMENTS

Using analysis of variance and linear regression techniques, concentrations of LH, T and inhibin B were compared by race/ethnicity for all boys and pubertal status (Tanner's Staging 1, 2 and 3+) for boys aged 8 years and older. Receiver operating curves were utilized to identify cut-points predictive of pubertal HPG status.

RESULTS

Mean hormones levels progressively increased with age. Receiver operating characteristic (ROC) curves indicate hormones are consistent with pubertal onset as indicated by Tanner stage 2, except for T and genital stage 2. Inhibin B and LH levels increased significantly by genital stage after adjusting for age and race/ethnicity, while LH and T concentrations increased significantly across pubic hair stages. Levels of inhibin B were significantly higher for NHB boys compared with other racial/ethnic groups.

CONCLUSIONS

In these cross-sectional findings, hormone levels rise gradually as boys approach the peripubertal age, whereas an abrupt rise was not associated with the onset of physical changes of puberty.

Development of a second generation Inhibin B ELISA

Inhibins are heterodimeric protein hormones secreted by the granulosa cells of the ovary in the female and the Sertoli cells of the testis in the male. Published research studies have assessed Inhibin B levels in Sertoli cell function, ovarian reserve and granulosa cell tumors. A two-step sandwich-type enzymatic microplate assay to measure Inhibin B levels within 3.5h is reported, and sample pre-treatment is not required. The assay measures Inhibin B in 50 μL of serum or Li-Hep plasma sample against Inhibin B calibrators (10-1000 pg/mL). The highly characterized antibody pair used in the assay measures 100% Inhibin B and no response was detected above the sensitivity of the assay with Inhibin A, Activin A, Activin B, Activin AB, AMH, FSH, LH or Follistatin 315 at the concentrations tested. The second generation Inhibin B assay was compared against two commercially available assays using 60 male and 60 female samples, ranging in age from 20 to 50 years. The assay showed significant positive linear correlations to Oxford Brooks Innovation (OBI) and Diagnostics Systems Laboratories (DSL) assays (r=0.99; P<0.0001; and r=0.97; P<0.0001), respectively. Method comparison to OBI and DSL resulted in the following slope and intercept (Gen II=1.03 OBI-6.77 pg/mL and Gen II=1.57 DSL+11.29 pg/mL), respectively. Matched serum and Li-Hep plasma samples (n=120) showed a correlation coefficient of >0.99 and a slope of 0.97 with zero intercept. Total imprecision calculated on three samples and two controls over 40 runs, three replicates per run, using NCCLS EP5-A guidelines was 6.8% at 19.34 pg/mL, 4.4% at 76.03 pg/mL, 4.3% at 275.3 pg/mL, 5.4% at 99.88 pg/mL, and 5.7% at 363.9 pg/mL. The LoQ for the assay at 20% CV was 4.8 pg/mL. Dilution and spiking studies showed an average recovery of 90-110%. A highly specific, sensitive, simplified and reproducible microplate Inhibin B assay has been developed to measure Inhibin B in serum and Li-Hep plasma. The performance of the assay is ideal for investigation into the physiologic role of Inhibin B in both men and women.

A new 'total' activin B enzyme-linked immunosorbent assay (ELISA): development and validation for human samples

BACKGROUND AND OBJECTIVE

There are currently no sensitive and specific assays for activin B that could be utilized to study human biological fluids. The aim of this project was to develop and validate a 'total' activin B ELISA for use with human biological fluids and establish concentrations of activin B in the circulation and fluids from the reproductive organs.

DESIGN

The new ELISA was validated and then used to measure activin B levels in the circulation of healthy participants, IVF patients, pregnant women and in ovarian follicular fluid and seminal plasma.

PATIENTS AND MEASUREMENTS

Healthy adult subjects (n = 143), subjects from an IVF clinic (n = 27) and pregnancy groups (n = 29) were sampled.

RESULTS

The sensitivity of the assay was 0.019 ng/ml. Validation of the activin B ELISA showed good recovery (90.7 +/- 9.8%) and linearity in biological fluid and cell culture media and low cross-reactivity with related analytes (inhibin B = 0.077% and activin A = 0.0034%). There was a negative correlation between activin B concentration (r = -0.281, P < 0.011) and females with increasing age. Patients attending IVF clinics had significantly lower levels of activin B compared with gender-matched control subjects. Ovarian follicular fluid and seminal plasma had 50-80 fold higher levels of activin B (mean = 5.35 and 3.66 ng/ml respectively) than sera (mean = 0.071 ng/ml).

CONCLUSIONS

This fully validated ELISA for activin B offers a tremendous utility for measuring this protein in a variety of normal physiological processes and in various clinical pathologies.

Endometrial inhibin/activin beta-B subunit expression is related to decidualization and is reduced in tubal ectopic pregnancy

CONTEXT

Ectopic pregnancy is common but remains difficult to diagnose accurately. There is no serum test to differentiate ectopic from intrauterine gestation.

OBJECTIVE

Our objective was to investigate differential gene expression in decidualized endometrium of ectopic pregnancy.

DESIGN

Tissue and serum analysis informed by microarray study was performed.

SETTING

The study was performed at a large United Kingdom teaching hospital.

PATIENTS OR OTHER PARTICIPANTS

Women undergoing surgical termination of pregnancy (n = 8), evacuation of uterus for miscarriage (n = 6), and surgery for tubal ectopic pregnancy (n = 11) were included in the study. Endometrium was collected from normally cycling women undergoing hysterectomy.

INTERVENTIONS

Decidualized endometrium was subjected to microarray analysis, morphological assessment, and immunohistochemistry. Endometrial stromal fibroblasts were cultured in the presence of decidualizing stimuli.

MAIN OUTCOME MEASURES

Differential expression of potentially secreted molecules was calculated.

RESULTS

Inhibin/activin beta-B expression was lower in decidualized endometrium from ectopic pregnancies when compared with that of ongoing pregnancies (P < 0.01) or miscarriages (P < 0.01). The localization of the beta-B subunit was more marked in decidualized than nondecidualized stroma. Decidualization of stromal fibroblasts in vitro was associated with increased beta-B expression (P < 0.05). Endometrial stroma of ectopic pregnancies was less decidualized morphologically (P < 0.05), with lower prolactin (P < 0.01) and IGF binding protein-1 (P < 0.005) expression. Serum activin B was lower in ectopic pregnancies (P < 0.005) than in intrauterine pregnancies, whereas there was no difference in progesterone concentrations.

CONCLUSIONS

Despite similar concentrations of progesterone, the endometrium of ectopic pregnancies is less decidualized than intrauterine pregnancies. Expression of the beta-B subunit is related to decidualization and can be detected in the circulation as activin B. Serum activin B concentrations are lower in ectopic pregnancy.