The Anti-Müllerian Hormone Precursor (proAMH) Is Not Converted to the Receptor-Competent Form (AMHN,C) in the Circulating Blood of Mice

Determination of anti-Müllerian hormone levels in blood and urine in fertile cats

In recent years, blood anti-Müllerian hormone (AMH) levels have been investigated in female animals to diagnose many conditions, such as the presence of ovarian tissue, follicle reserve, and granulosa cell tumors. Since blood collection is an invasive method, diagnosis with a non-invasive method is important in terms of practicality and animal welfare. This study aimed to investigate the presence of AMH in cat urine and determine whether a correlation exists between blood and urine AMH levels. In addition, it was aimed at revealing whether there was a change in blood and urine AMH levels according to ovarian follicle distribution. Twenty-seven healthy, fertile female cats in the follicular phase were included. Following blood and urine sample collection, a routine ovariohysterectomy was performed. Histological analysis of the removed ovarian tissue was used to determine ovarian follicle types. While both AMH and estrogen levels were determined in blood samples, only AMH levels were investigated in urine samples. Blood AMH levels averaged 10.61 ± 0.75 ng/mL (range: 5-16 ng/mL), while urine AMH levels averaged 5.67 ± 0.91 ng/mL (range: 0.2-13 ng/mL). While urinary AMH level was <1 ng/mL in 7 cats, urinary AMH was >1 ng/mL in all remaining cats. While the study demonstrated AMH excretion in urine, no correlation was found between blood and urine AMH values. However, a significant positive correlation was observed between blood AMH levels and serum estrogen levels (P < 0.001). These findings suggest that urinary AMH may be a product of proteolytic degradation, potentially leading to inaccurate estimations of ovarian activity based solely on urine AMH levels.

Investigations of the function of AMH in granulosa cells in hens

Anti-mullerian hormone (AMH) plays a crucial role in follicle regulation in mammals by preventing premature primordial follicle activation and restricting follicle development through reduction of FSH sensitivity and inhibition of FSH-induced increase of steroidogenic enzymes. AMH is produced by granulosa cells from growing follicles and expression declines at the time of selection in both mammalian and avian species. The role of AMH in chicken granulosa cells remains unclear, as research is complicated because mammalian AMH is not bioactive in chickens and there is a lack of commercially available chicken AMH. In the current experiments, we used RNA interference to study the role of AMH on markers of follicle development in the presence and absence of FSH. Cultured chicken granulosa cells from 3-5 mm follicles and 6-8 mm follicles, the growing pool from which follicle selection is thought to occur, were used. Transfection with an AMH-specific siRNA significantly reduced AMH mRNA expression in granulosa cells from 3-5 mm and 6-8 mm follicles. Genes of interest were only measured in granulosa cells of 3-5 mm follicles due to low expression of AMH mRNA at the 6-8 mm follicle stage. Knockdown of AMH mRNA did not affect markers of follicle development (follicle stimulating hormone receptor, FSHR; steroidogenic acute regulatory protein, STAR; cytochrome P450 family 11 subfamily A member 1, CYP11A1; bone morphogenetic protein receptor type 2, BMPR2) or FSH responsiveness in granulosa cells from 3-5 mm follicles, indicating that AMH does not regulate follicle development directly by affecting markers of steroidogenesis, FSHR or BMPR2 at this follicle stage in chickens.

Functional analysis of rare anti-Müllerian hormone protein-altering variants identified in women with PCOS

Recently, rare heterozygous AMH protein-altering variants were identified in women with polycystic ovary syndrome (PCOS), causing reduced anti-Müllerian hormone (AMH) signaling. However, the exact functional mechanism remains unknown. Here, we analyzed the processing, secretion, and signaling of these AMH variants. Functional analysis of six PCOS-specific AMH variants (V12G, P151S, P270S, P352S, P362S, H506Q) and one control-specific variant (A519V) was performed in the mouse granulosa cell-line KK-1. Human (h) AMH-151S and hAMH-506Q have ∼90% decreased AMH signaling compared to wild-type (wt) AMH signaling. Coexpression of hAMH-151S or hAMH-506Q with wt-hAMH dose-dependently inhibited wt-hAMH signaling. Western blotting revealed that hAMH-151S and hAMH-506Q proteins were detected in the cell lysate but not in the supernatant. Confocal microscopy showed that HEK293 cells expressing hAMH-151S and hAMH-506Q had higher cellular AMH protein levels with endoplasmic reticulum (ER) retention compared to cells expressing wt-hAMH. Using two AMH ELISA kits, hAMH-151S was detected in the cell lysate, while only very low levels were detected in the supernatant. Both hAMH-362S and hAMH-519V were detectable using the automated AMH ELISA but showed severely reduced immunoactivity in the manual ELISA. Surprisingly, hAMH-506Q was undetectable in both the cell lysate and supernatant using either ELISA. However, in PCOS cases, heterozygous carriers of the P151S and H506Q variants still had detectable AMH in both assays. Thus, P151S and H506Q disrupt normal processing and secretion of AMH, causing ER retention. Additionally, AMH variants can impair the AMH immunoactivity. An AMH variant may be considered when serum AMH levels are relatively low in PCOS cases.

Serum and urine profiles of TGF-β superfamily members in reproductive aged women

BACKGROUND

TGF-β superfamily members are important biomarkers of reproductive health in women desiring fertility and during pregnancy. TGF-β proteins derived from the ovary and/or placenta have been detected in serum in women, but there have been very few attempts to measure them non-invasively, such as in urinary samples, and to compare them to serum concentrations.

METHODS

We measured inhibin A, inhibin B, total inhibin, AMH, activin A, activin B, activin AB, follistatin, the GDF-9/BMP-15 complex, and GDF-15 in paired serum and urine samples from healthy reproductive aged women and in pregnant (second trimester) women.

RESULTS

We detected all hormones in serum in both pregnant and non-pregnant women. Inhibin A, total inhibin, activin A, activin AB, follistatin, and GDF-15 were significantly higher in pregnant than in non-pregnant women. GDF-15 was the only hormone consistently detected in urine. We also measured, for the first time, the GDF-9/BMP-15 functional heterodimer and the GDF-15 protein harboring the H202D polymorphism.

CONCLUSIONS

We report the successful measurement of the GDF-9/BMP-15 heterodimer (its native form) in serum and the ability to measure GDF-15 non-invasively, in urinary samples. This novel GDF-15 assay also captures the antigen in the presence of a common genetic variant.

Molecular Mechanisms of AMH Signaling

Anti-Müllerian Hormone (AMH) is a secreted glycoprotein hormone with critical roles in reproductive development and regulation. Its chemical and mechanistic similarities to members of the Transforming Growth Factor β (TGF-β) family have led to its placement within this signaling family. As a member of the TGF-β family, AMH exists as a noncovalent complex of a large N-terminal prodomain and smaller C-terminal mature signaling domain. To produce a signal, the mature domain will bind to the extracellular domains of two type I and two type II receptors which results in an intracellular SMAD signal. Interestingly, as will be discussed in this review, AMH possesses several unique characteristics which set it apart from other ligands within the TGF-β family. In particular, AMH has a dedicated type II receptor, Anti-Müllerian Hormone Receptor Type II (AMHR2), making this interaction intriguing mechanistically as well as therapeutically. Further, the prodomain of AMH has remained largely uncharacterized, despite being the largest prodomain within the family. Recent advancements in the field have provided valuable insight into the molecular mechanisms of AMH signaling, however there are still many areas of AMH signaling not understood. Herein, we will discuss what is known about the biochemistry of AMH and AMHR2, focusing on recent advances in understanding the unique characteristics of AMH signaling and the molecular mechanisms of receptor engagement.

Anti-Müllerian Hormone in Female Reproduction

Anti-Müllerian hormone (AMH), also called Müllerian inhibiting substance, was shown to be synthesized by the ovary in the 1980s. This article reviews the main findings of the past 20 years on the regulation of the expression of AMH and its specific receptor AMHR2 by granulosa cells, the mechanism of action of AMH, the different roles it plays in the reproductive organs, its clinical utility, and its involvement in the principal pathological conditions affecting women. The findings in respect of regulation tell us that AMH and AMHR2 expression is mainly regulated by bone morphogenetic proteins, gonadotropins, and estrogens. It has now been established that AMH regulates the different steps of folliculogenesis and that it has neuroendocrine effects. On the other hand, the importance of serum AMH as a reliable marker of ovarian reserve and as a useful tool in the prediction of the polycystic ovary syndrome (PCOS) and primary ovarian failure has also been acknowledged. Last but not least, a large body of evidence points to the involvement of AMH in the pathogenesis of PCOS.

A novel method for purification of biologically active C-terminal fragment of human recombinant anti-mullerian hormone

Anti-mullerian hormone (AMH) is one of the least studied members of transforming growth factor beta superfamily showing pro-apoptotic activity against cells positive for hormone type II receptor overexpressed by malignant cells in many cancer cases. Here, we propose an improved method for isolation of recombinant C-terminal AMH fragment (C-rAMH) to obtain homogeneous preparations of this protein with high biological activity. In contrast to our previously developed C-rAMH purification technology based on reversed-phase HPLC, the key stage of the new approach is hydrophobic interaction chromatography using Toyopearl Butyl-650S resin performed under more benign conditions. This modification of the previously developed method allowed highly purified C-rAMH to be obtained that is characterized by twice the specificity estimated as the ability to bind to the recombinant analog of AMH type II receptor and by significantly higher biological activity, that is, the ability to induce the death of target cells. Thus, we made the purification technology even more cost-effective and suitable for the production of drug forms based on C-rAMH.

[The study of interaction of different forms of human recombinant anti-mullerian hormone with a chimeric analogue of the AMH type II]

The homodimeric glycoprotein, anti-mullerian hormone (AMH), described over 70 years ago by A. Jost, is the least studied member of the transforming growth factor beta superfamily. Despite the antitumor activity of AMH discovered at the end of the last century, the creation of effective drugs based on AMH is hindered primarily by the lack of information on the mechanism of various AMH forms interaction with a specific type II receptor (MISRII). Previously, we have shown that not only the full-length activated hormone but also its C-terminal fragment (C-rAMH) could bind to MISRII. In this work, using the surface plasmon resonance technique, we compared the interaction of three forms of recombinant AMH (rAMH) with the MISRII analogue - the chimeric protein MISRII-Fc containing AMH type II receptor and a Fc-fragment of the human IgG1 heavy chain. Comparison of the binding of MISRII-Fc, immobilized on a chip with group specificity for human immunoglobulins, to C-rAMH, to intact rAMH (pro-rAMH), and to rAMH containing one uncleaved monomer (hc-rAMH), showed that the KD of the complexes increased: 1.7 nM, 88 nM and 110 nM, respectively. Thus, we have shown that C-terminal fragment of AMH has the maximum affinity for the recombinant MISRII analogue, which indicates the prospects for the development of drugs based on this hormone derivative.

[Mullerian inhibiting substance type II receptor as a potential target for antineoplastic therapy]

The review considers properties of the type II anti-Mullerian hormone receptor (mullerian inhibiting substance receptor type II, MISRII), a transmembrane sensor with its own serine/threonine protein kinase activity, triggering apoptosis of the Mullerian ducts in mammalian embryogenesis and providing formation of the male type reproductive system. According to recent data, MISRII overexpression in the postnatal period is found in cells of a number of ovarian, mammary gland, and prostate tumors, and anti-Mullerian hormone (AMH) has a pro-apoptotic effect on MISRII-positive tumor cells. This fact makes MISRII a potential target for targeted anti-cancer therapy. Treatment based on targeting MISRII seems to be a much more effective alternative to the traditional one and will significantly reduce the drug dose. However, the mechanism of MISRII-AMH interaction is still poorly understood, so the development of new anticancer drugs is complicated. The review analyzes MISRII molecular structure and expression levels in various tissues and cell lines, as well as current understanding of the AMH binding mechanisms and data on the possibility of using MISRII as a target for the action of AMH-based antineoplastic drugs.

Müllerian inhibiting substance/anti-Müllerian hormone as a fertility preservation agent

PURPOSE OF REVIEW

The nascent field of oncofertility is quickly gaining traction as novel experimental treatments are being developed, driving a renewed interest in Müllerian inhibiting substance (MIS) as an ovarian fertoprotectant.

RECENT FINDINGS

MIS is unique in its mechanisms of ovarian protection by virtue of acting directly on granulosa cells of primordial follicles and for being a benign reproductive hormone, with few side effects. We will explore in this review how it may be utilized to protect the ovary from chemotherapy, or to enhance ovarian tissue cryopreservation therapy. We will also examine potential mechanisms of action of MIS across multiple cell types, as well as current limitations in our understanding of the pharmacology of recombinant MIS.

SUMMARY

The usefulness of MIS as a fertoprotectant may be dependent on the mechanisms of gonadotoxicity of each chemotherapeutic. Further investigation is needed to determine how to best deliver and combine MIS treatment to existing fertility management strategies.

Anti-Müllerian hormone overexpression restricts preantral ovarian follicle survival

Anti-Müllerian hormone (AMH) is an ovarian regulator that affects folliculogenesis. AMH inhibits the developmental activation of the dormant primordial follicles and the oocyte within. In more mature follicles, AMH reduces granulosa cell sensitivity to follicle-stimulating hormone (FSH). We examined the effects of AMH overexpression on the stages of ovarian folliculogenesis, and the development of embryos, with a transgenic mouse that overexpresses human AMH in central nervous system neurons under the control of the mouse Thy1.2 promoter (Thy1.2-AMHTg mice). These mice are severely sub-fertile, despite relatively normal ovulation rates. The embryos of Thy1.2-AMHTg females exhibited delayed preimplantation development and extensive mid-gestation fetal resorption. Young Thy1.2-AMHTg mouse ovaries exhibited only a slight reduction in the rate of primordial follicle activation but large declines in the number of developing follicles surviving past the primary stage. It was expected that Thy1.2-AMHTg mice would retain more primordial follicles as they aged, but at 5 months, their number was significantly reduced relative to wild-type females. These data indicate that moderate elevations in AMH levels can severely restrict reproductive output and the number of developing follicles in the ovary. This evidence suggests that early antral follicles are a target for AMH signaling, which may regulate early follicle survival.

The mechanisms underlying the effects of AMH on Müllerian duct regression in male mice

Anti-Müllerian hormone (AMH) produced in the developing testis induces the regression of the Müllerian duct, which develops into the oviducts, uterus and upper vagina. In our true hermaphrodite mouse with an ovary on one side and a testis on the other (O/T), the oviduct and uterus are present only on the ovary side, and nothing derived from the Müllerian duct is present on the testis side. Here, we investigate the mechanism underlying the unilateral Müllerian duct regression and the mode of AMH signaling, by performing immunohistology, Western blotting, and organ culture analyses. The histological analysis revealed that during the start of the Müllerian duct regression, the duct in the O/T mice was clearly regressed on the AMH-positive testis side compared to the AMH-negative ovary side. The immunohistochemistry showed a diffuse immunoreaction of AMH in the interstitium surrounding the testis cord and boundary region between the testis and mesonephros, especially in the cranial portion. Western blotting revealed that the amount of AMH in the cranial half of the mesonephros was larger than that in the caudal half. AMH injected into the gonads in organ culture induced the regression of the Müllerian duct via the interstitium of the organ. These results suggest that AMH acts on the Müllerian duct in male mice by exuding into the interstitium surrounding the testis cord and infiltrating through the cranial region from the testis to the mesonephros.

Relative levels of the proprotein and cleavage-activated form of circulating human anti-Müllerian hormone are sexually dimorphic and variable during the life cycle

Anti‐Müllerian hormone (AMH) is a gonadal hormone, which induces aspects of the male phenotype, and influences ovarian follicular recruitment. AMH is synthesized as a proprotein (proAMH), which is incompletely cleaved to the receptor‐competent AMH_N,C. AMH ELISAs have not distinguished between proAMH and AMH_N,C; consequently, the physiological ranges of circulating proAMH and AMH_N,C are unknown. A novel proAMH ELISA has been used to assay serum proAMH in humans. Total AMH was also measured, enabling the AMH_N,C concentration to be calculated. Stored serum from 131 boys, 80 younger, and 106 older men were examined, with serum from 14 girls and 18 women included for comparison. The mean levels of proAMH and AMH_N,C in pM were respectively: boys (253, 526), men (7.7, 36), elderly men (5.7, 19), girls (3.3, 15), and women (5.2, 27) (boys vs. men, P < 0.001; girls vs. women, P = 0.032). The proportion of proAMH as a percentage of total AMH (API) was approximately twofold higher in boys than men (P < 0.001) with little overlap between the ranges, with girls also exhibiting lesser cleavage of their AMH than women (P < 0.001). The API varied within each population group. In young men, the API did not correlate with circulating levels of the other testicular hormones (testosterone, InhB, and INSL3). In conclusion, the cleavage of circulating AMH varies extensively within the human population, with most individuals having significant levels of proAMH. The physiological and clinical relevance of circulating proAMH needs to be established.

Changes in Circulating ProAMH and Total AMH during Healthy Pregnancy and Post-Partum: A Longitudinal Study

Circulating Anti-Müllerian hormone (AMH) is derived from the gonads, and is a mixture of the prohormone (proAMH), which does not bind to AMH receptors, and receptor-competent AMH. The functions of a hormone are partially defined by the factors that control its levels. Ovarian reserve accounts for 55~75% of the woman-to-woman variation in AMH level, leaving over 25% of the biological variation to be explained. Pregnancy has been reported to decrease circulating AMH levels, but the observations are inconsistent, with the effect of pregnancy on the bioactivity of AMH being unknown. We have therefore undertaken a longitudinal study of circulating proAMH and total AMH during pregnancy. Serum samples were drawn at 6–8 gestational time-points (first trimester to post-partum) from 25 healthy women with prior uneventful pregnancies. The total AMH and proAMH levels were measured at each time-point using ELISA. The level of circulating total AMH progressively decreased during pregnancy, in all women (p<0.001). On average, the percentage decline between the first trimester and 36–39 weeks’ gestation was 61.5%, with a standard deviation of 13.0% (range 30.4–81.2%). The percentage decline in total AMH levels associated with maternal age (R = -0.53, p = 0.024), but not with the women’s first trimester AMH level. The postpartum total AMH levels showed no consistent relationship to the woman’s first trimester values (range 31–273%). This raises the possibility that a fundamental determinant of circulating AMH levels is reset during pregnancy. The ratio of proAMH to total AMH levels exhibited little or no variation during pregnancy, indicating that the control of the cleavage/activation of AMH is distinct from the mechanisms that control the total level of AMH.

Variation in circulating antimüllerian hormone precursor during the periovulatory and acute postovulatory phases of the human ovarian cycle

OBJECTIVE

To determine whether the relative quantity of circulating AMH precursor (proAMH) declines relative to levels of the active form (AMH_N,C) in the periovulatory phase of the ovarian cycle.

DESIGN

Longitudinal study.

SETTING

Local community.

PATIENT(S)

Sixteen women aged between 18 to 30 years with regular menstrual cycles between 25 to 35 days long.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Serum concentrations of proAMH and total AMH (proAMH and AMH_N,C combined) measured by immunoassay, with relative levels of proAMH expressed as the AMH prohormone index (API = [ProAMH]/[Total AMH] × 100).

RESULT(S)

The mean API in the 11 eligible women fell from 20.7 during the luteinizing hormone (LH) surge period to 18.7 during the acute postsurge period. No statistically significant differences in the API were observed among samples taken at single time points in the early follicular, midfollicular, midluteal, and late luteal phases.

CONCLUSION(S)

This study suggests that activation of AMH by proteolytic enzymes is largely stable throughout the ovarian cycle. However, there is a subtle but robust decrease in the level of proAMH relative to AMH_N,C in the acute postovulatory period. This may indicate that periovulatory increases in prohormone convertases cause increases in proAMH cleavage rates. Alternatively, rapid changes in the hierarchy of follicle developmental stages during ovulation may result in changes in the relative ratios of proAMH and AMH_N,C.

Anti-Müllerian hormone: a new actor of sexual dimorphism in pituitary gonadotrope activity before puberty

Anti-Müllerian hormone (AMH) contributes to male sexual differentiation and acts on gonads of both sexes. Identification of AMH receptivity in both pituitary and brain has led to the intriguing idea that AMH participates to the hypothalamic-pituitary control of reproduction, however in vivo experimental evidence is still lacking. We show that AMH stimulates secretion and pituitary gene expression of the gonadotropin FSH in vivo in rats. AMH action is sex-dependent, being restricted to females and occurring before puberty. Accordingly, we report higher levels of pituitary AMH receptor transcripts in immature females. We show that AMH is functionally coupled to the Smad pathway in LβT2 gonadotrope cells and dose-dependently increases Fshb transcript levels. Furthermore, AMH was shown to establish complex interrelations with canonical FSH regulators as it cooperates with activin to induce Fshb expression whereas it reduces BMP2 action. We report that GnRH interferes with AMH by decreasing AMH receptivity in vivo in females. Moreover, AMH specifically regulates FSH and not LH, indicating that AMH is a factor contributing to the differential regulation of gonadotropins. Overall, our study uncovers a new role for AMH in regulating gonadotrope function and suggests that AMH participates in the postnatal elevation of FSH secretion in females.