Anti-Müllerian hormone production in the ovary: a comparative study in bovine and porcine granulosa cells†.

In this study, we aimed to determine the origin of the difference, in terms of anti-Müllerian hormone production, existing between the bovine and porcine ovaries. We first confirmed by quantitative real-time-Polymerase-Chain Reaction, ELISA assay and immunohistochemistry that anti-Müllerian hormone mRNA and protein production are very low in porcine ovarian growing follicles compared to bovine ones. We then have transfected porcine and bovine granulosa cells with vectors containing the luciferase gene driven by the porcine or the bovine anti-Müllerian hormone promoter. These transfection experiments showed that the porcine anti-Müllerian hormone promoter is less active and less responsive to bone morphogenetic protein stimulations than the bovine promoter in both porcine and bovine cells. Moreover, bovine but not porcine granulosa cells were responsive to bone morphogenetic protein stimulation after transfection of a plasmidic construction including a strong response element to the bone morphogenetic proteins (12 repetitions of the GCCG sequence) upstream of the luciferase reporter gene. We also showed that SMAD6, an inhibitor of the SMAD1-5-8 pathway, is strongly expressed in porcine compared to the bovine granulosa cells. Overall, these results suggest that the low expression of anti-Müllerian hormone in porcine growing follicles is due to both a lack of activity/sensitivity of the porcine anti-Müllerian hormone promoter, and to the lack of responsiveness of porcine granulosa cells to bone morphogenetic protein signaling, potentially due to an overexpression of SMAD6 compared to bovine granulosa cells. We propose that the low levels of anti-Müllerian hormone in the pig would explain the poly-ovulatory phenotype in this species.

Prenatal programming by testosterone of follicular theca cell functions in ovary.

In mammalian ovaries, the theca layers of growing follicles are critical for maintaining their structural integrity and supporting androgen synthesis. Through combining the postnatal monitoring of ovaries by abdominal magnetic resonance imaging, endocrine profiling, hormonal analysis of the follicular fluid of growing follicles, and transcriptomic analysis of follicular theca cells, we provide evidence that the exposure of ovine fetuses to testosterone excess activates postnatal follicular growth and strongly affects the functions of follicular theca in adulthood. Prenatal exposure to testosterone impaired androgen synthesis in the small antral follicles of adults and affected the expression in their theca cells of a wide array of genes encoding extracellular matrix components, their membrane receptors, and signaling pathways. Most expression changes were uncorrelated with the concentrations of gonadotropins, steroids, and anti-Müllerian hormone in the recent hormonal environment of theca cells, suggesting that these changes rather result from the long-term developmental effects of testosterone on theca cell precursors in fetal ovaries. Disruptions of the extracellular matrix structure and signaling in the follicular theca and ovarian cortex can explain the acceleration of follicle growth through altering the stiffness of ovarian tissue. We propose that these mechanisms participate in the etiology of the polycystic ovarian syndrome, a major reproductive pathology in woman.

Molecular evidence that follicle development is accelerated in vitro compared to in vivo.

In this study, we systematically compared the morphological, functional and molecular characteristics of granulosa cells and oocytes obtained by a three-dimensional in vitro model of ovine ovarian follicular growth with those of follicles recovered in vivo Preantral follicles of 200 µm diameter were recovered and cultured up to 950 µm over a 20-day period. Compared with in vivo follicles, the in vitro culture conditions maintained follicle survival, with no difference in the rate of atresia. However, the in vitro conditions induced a slight decrease in oocyte growth rate, delayed antrum formation and increased granulosa cell proliferation rate, accompanied by an increase and decrease in CCND2 and CDKN1A mRNA expression respectively. These changes were associated with advanced granulosa cell differentiation in early antral follicles larger than 400 µm diameter, regardless of the presence or absence of FSH, as indicated by an increase in estradiol secretion, together with decreased AMH secretion and expression, as well as increased expression of GJA1, CYP19A1, ESR1, ESR2, FSHR, INHA, INHBA, INHBB and FST There was a decrease in the expression of oocyte-specific molecular markers GJA4, KIT, ZP3, WEE2 and BMP15 in vitro compared to that in vivo Moreover, a higher percentage of the oocytes recovered from cultured follicles 550 to 950 µm in diameter was able to reach the metaphase II meiosis stage. Overall, this in vitro model of ovarian follicle development is characterized by accelerated follicular maturation, associated with improved developmental competence of the oocyte, compared to follicles recovered in vivo.

BMP15 regulates the inhibin/activin system independently of ovulation rate control in sheep.

Polymorphisms in the gene encoding bone morphogenetic protein 15 (BMP15) have been associated with multiple ovulations in sheep. As BMP15 regulates inhibin expression in rodents, we assumed that the ovarian inhibin/activin system could mediate part of the effect of BMP15 mutations in the regulation of ovulation rate in sheep. To answer this question, we have studied the effects of two natural loss-of-function mutations of BMP15 on the expression of components of this system. The FecXR and the FecXGr mutations, when present respectively in Rasa Aragonesa ewes at the heterozygous state and in Grivette ewes at the homozygous state, were associated with a twofold increase in ovulation rate. There were only small differences between mutant and wild-type ewes for mRNA expression of INHA, INHBA, ACVR1B, ACVR2A, FST or TGFBR3 in granulosa cells and inhibin A or activin A concentrations in follicular fluid. Moreover, the effects of mutations differed between breeds. In cultures of granulosa cells from wild-type ewes, BMP15, acting alone or in synergy with GDF9, stimulated INHA, INHBA and FST expression, but inhibited the expression of TGFBR3 Activin A did not affect INHBA expression, but inhibited the expression of ACVR2A also. The complexity of the inhibin/activin system, including positive and antagonistic elements, and the differential regulation of these elements by BMP15 and activin can explain that the effects of BMP15 mutations differ when present in different genetic backgrounds. In conclusion, the ovarian inhibin/activin system is unlikely to participate in the increase of ovulation rate associated with BMP15 mutations in sheep.

Loss of oocytes due to conditional ablation of Murine double minute 2 (Mdm2) gene is p53-dependent and results in female sterility.

Murine double minute 2 and 4 (Mdm2, Mdm4) are major p53-negative regulators, preventing thus uncontrolled apoptosis induction in numerous cell types, although their function in the female germ line has received little attention. In the present work, we have generated mice with specific invalidation of Mdm2 and Mdm4 genes in the mouse oocyte (Mdm2(Ocko) and Mdm4(Ocko) mice), to test their implication in survival of these germ cells. Most of the Mdm2(Ocko) but not Mdm4(Ocko) mice were sterile, with a dramatic reduction of the weight of ovaries and genital tract, a strong increase in follicle-stimulating hormone and luteinizing hormone serum levels, and a reduction of anti-mullerian hormone serum levels. Histological analyses revealed an obvious decrease of the number of growing follicles beyond the primary stage in Mdm2(Ocko) ovaries in comparison to controls, with a pronounced increase in the apparition of primary atretic follicles, most being devoid of oocyte. Similar phenotypes were observed with Mdm2(Ocko) Mdm4(Ocko) ovaries, with no worsening of the phenotype. However, we failed to detect any increase in p53 level in mutant oocytes, nor any other apoptotic marker, introgression of this targeted invalidation in p53-/- mice restored the fertility of females. This study is the first to show that Mdm2, but not Mdm4, has a critical role in oocyte survival and would be involved in premature ovarian insufficiency phenotype.

The Bone Morphogenetic Protein 15 Up-Regulates the Anti-Müllerian Hormone Receptor Expression in Granulosa Cells.

CONTEXT: Anti-Müllerian hormone (AMH) is produced by the granulosa cells (GCs) of growing follicles and inhibits follicular development. OBJECTIVE: This study aimed to investigate the regulation of the AMH-specific type 2 receptor (AMHR2) gene expression in GCs by bone morphogenetic protein (BMP)15, BMP4 and growth differentiation factor (GDF)9. DESIGN, SETTING, AND PATIENTS: Their effects on AMHR2 and AMH mRNAs were studied in luteinized human GCs and in ovine GCs (oGCs) from small antral follicles. The effects of BMPs on human AMHR2 and AMH promoter reporter activities were analyzed in transfected oGCs. The in vivo effect of BMP15 on GCs AMHR2 and AMH expression was investigated by using Lacaune and Rasa Aragonesa hyperprolific ewes carrying loss-of-function mutations in BMP15. MAIN OUTCOME MEASURES: mRNAs were quantified by real-time RT-PCR. Promoter reporter constructs activities were quantified by the measurement of their luciferase activity. RESULTS: BMP15 and BMP4 enhanced AMHR2 and AMH expression in human GCs and in oGCs, whereas GDF9 had no effect. In oGCs, GDF9 increased BMP15 effect on AMH expression. Consistent with these results, BMP15 and BMP4, but not GDF9, enhanced AMHR2 promoter activity in oGCs, whereas GDF9 increased BMP15 effect on AMH promoter activity. Moreover, oGCs from both BMP15 mutant ewes had reduced AMHR2 mRNA levels but unchanged AMH expression compared with wild-type ewes. CONCLUSIONS: Altogether, these results suggest that the mechanisms of action of BMP15 on AMHR2 and AMH expression are different, and that by stimulating AMHR2 and AMH expression in GCs BMP15 enhances AMH inhibitory actions in GCs.

Anti-Müllerian hormone regulation by the bone morphogenetic proteins in the sheep ovary: deciphering a direct regulatory pathway.

In the ovary, anti-Müllerian hormone (AMH) is produced by the granulosa cells of growing follicles and can modulate the recruitment of primordial follicles and the FSH-dependent development of follicles. However, the regulation of its production remains poorly understood. Recently, a stimulating effect of the bone morphogenetic proteins (BMPs) on AMH production by granulosa cells has been shown in vitro, but the molecular mechanisms implicated in this regulation and its physiological importance in ovarian function have not yet been established. In the hyperprolific Booroola ewes carrying the FecB(B) partial loss-of-function mutation in the fecundity gene encoding the FecB/BMP receptor, type 1B, the granulosa cells of antral follicles expressed and secreted low AMH amounts, resulting in low AMH concentrations in blood, despite high numbers of AMH-secreting follicles in ovaries. The presence of the FecB(B) mutation impaired the granulosa cell response to the stimulating action of BMP4 on AMH production, indicating a crucial role of the BMP receptor, type 1B in AMH regulation. In ovine granulosa cells, BMP4 enhanced the transcriptional activity of the human AMH promoter, and this action depended on the presence of SMAD1, acting on a promoter sequence located between -423 and -202 bp upstream of the AMH transcription start site. SMAD1 and SF1 acted in concert to mediate BMP4 action on the AMH promoter. Among the 2 SF1 binding sites present on the AMH promoter, the most proximal site, located at -92 bp upstream of the AMH transcription start site, was found to be critical for ensuring the response of the AMH promoter to BMP4. In conclusion, AMH could mediate the actions of BMPs in regulating follicular development and contributing to the determination of ovulation numbers. A molecular model of regulation of the AMH promoter transactivation by BMP signaling is proposed.

Regulation of anti-Müllerian hormone production in domestic animals.

In mammals, anti-Müllerian hormone (AMH) expression is detected in the granulosa cells of all growing follicles and is highest in healthy small antral follicles, which contribute most significantly to AMH endocrine levels. AMH is a reliable endocrine marker of this population of gonadotrophin-responsive follicles in ruminants and, over the longer term, plasma AMH concentrations are characteristic of individual animals. In the cow, plasma AMH concentrations follow specific dynamic profiles throughout the prepubertal period, the oestrous cycle and the change from gestation to the post partum period, with the alterations most likely reflecting numerical changes in the population of high AMH-producing follicles. In granulosa cells, bone morphogenetic proteins (BMP) enhance AMH gene expression and AMH synthesis, with these effects antagonised by FSH. BMP could both support follicular growth and contribute significantly to the induction and/or maintenance of AMH expression in small growing follicles. AMH expression decreases sharply in large follicles when they become oestrogenic, suggesting a role for FSH and/or oestradiol in these changes, but the underlying mechanisms remain hypothetical. A better understanding of the factors and mechanisms regulating AMH production is needed to propose new strategies for managing the reserve of primordial and small growing follicles, as well as for improving embryo production.

Determination of anti-Müllerian hormone concentrations in blood as a tool to select Holstein donor cows for embryo production: from the laboratory to the farm.

High between-animal variability in the number of embryos produced by multiple ovulation and embryo transfer (MOET) and ovum pick-up and in vitro production (OPU-IVP) methods remains a major limit to the development of embryo biotechnologies in cattle. The measurement of anti-Müllerian hormone (AMH) endocrine concentrations in cows can help to predict their follicular and ovulatory responses to gonadotrophin treatment. The present study aimed to provide practical information for a simple prognostic method based on AMH measurement in Holstein cows. Accurate AMH concentrations could be measured with ELISA in blood or plasma. In cows undergoing repeated OPU protocols over 1 year, the AMH concentrations measured in plasma samples collected before each gonadotrophin treatment were found to be highly repeatable and were tightly correlated with follicular responses. From data obtained at both an experimental station and farm settings, it was possible to propose AMH cut-off values to identify low-responding cows. Gonadotrophin-stimulated cows producing fewer than 15 large follicles at oestrus and fewer than 10 embryos in MOET protocols could be discarded efficiently with plasma AMH concentrations below 87 and 74 pg mL(-1), respectively. In conclusion, we propose a prognostic method based on a single AMH measurement to improve the results of embryo biotechnologies.

Anti-Mullerian hormone as a predictive endocrine marker for embryo production in the goat.

Recently, we demonstrated the relationship between anti-Müllerian hormone (AMH) circulating concentrations, ovarian follicles, and embryo production in cattle. However, they have not yet been established in a species with a seasonal breeding activity. Thus, goats were subjected to repeated in vivo embryo production during the breeding season, at the end of the breeding season, and at the end of the anestrus season. Embryo production after FSH treatment was highly repeatable for each goat. Plasma AMH concentrations, measured before the first FSH treatment, were highly correlated with the number of collected, transferable, and freezable embryos, resulting from the three sessions of embryo production. Plasma AMH concentrations transiently decreased after each exogenous FSH treatment, but they showed little change with season, and no relationship was observed between AMH and endogenous FSH concentrations during seasonal transitions. Follicles of 1-5 mm in diameter were the main target of the FSH treatment and were major contributors to circulating AMH concentrations. Granulosa cell AMH expression decreased as the follicle approached terminal development, while the expression of maturation markers (CYP19A1 and FSHR) increased. In conclusion, circulating AMH concentrations can be predictive of the capacity of a donor goat to produce high or low numbers of high-quality embryos. This prediction could be accurately made from a single blood measurement of AMH during either breeding or anestrus seasons. Variability in the number of gonadotropin-responsive follicles of 1-5 mm in diameter between individuals resulted in the differences in circulating AMH concentrations measured between individuals.

Regulation of anti-Müllerian hormone production in the cow: a multiscale study at endocrine, ovarian, follicular, and granulosa cell levels.

Anti-Müllerian hormone (AMH) is an endocrine marker that can help predict superovulatory responses to treatments administered to cows for embryo production. However, the optimal time of the estrous cycle at which a blood test should be performed for a highly reliable prognosis has not yet been established. Moreover, little is known about the regulation of AMH production. To answer these questions, a study was designed to investigate the regulation of AMH production in cows selected for their high or low ovulatory responses to superovulation. At the granulosa cell level, AMH production was inhibited by follicle-stimulating hormone but enhanced by bone morphogenetic proteins. At the follicular level, the expression of AMH within the follicle was dependent on the stage of follicular development. At the ovarian level, the size of the pool of small antral growing follicles determined ovarian AMH production. At the endocrine level, AMH followed a specific dynamic profile during the estrous cycle, which occurred independently of the follicular waves of terminal follicular development. Cows selected for their high or low responses to superovulation did not differ in the regulation of AMH production, but cows with higher responses had higher plasma AMH concentrations throughout the cycle. The optimal period of the estrous cycle at which to measure AMH concentrations with the aim of selecting the best cows for embryo production was found to be at estrus and after Day 12 of the cycle. Based on this multiscale study, we propose a model that integrates the different regulatory levels of AMH production.

Identification of CXCR4 as a new nitric oxide-regulated gene in human CD34+ cells.

As an intracellular second messenger, nitric oxide (NO) is increasingly implicated in the control of transcriptional machinery and gene expression. Here, we show that cell surface expression of CXCR4 on CD34(+) cells was increased in a dose- and time-dependent manner in response to NO donors. Augmented surface expression was correlated with an increase in CXCR4 mRNA level. A specific NO scavenger prevented the elevation in CXCR4 mRNA caused by NO donors, suggesting a direct signaling action mediated by NO on CXCR4 transcription. NO treatment had no significant effect on CXCR4 mRNA stability. However, induction of CXCR4 mRNA by NO was still observed in conditions in which initiation of translation was inhibited, suggesting that the NO effect must be mediated by a pre-existing protein. CXCR4 mRNA induction did not involve cGMP (guanosine 3', 5'-cyclic monophosphate) generation but was most likely mediated via oxidation of intracellular protein thiols. Finally, CD34(+) cells pretreated with NO donors exhibited an increased chemotactic response. This study demonstrates that the NO pathway can modulate CXCR4 expression in human CD34(+) cells and suggests that NO may play a critical role in the trafficking of hematopoietic progenitors.

BCR-ABL activates STAT3 via JAK and MEK pathways in human cells.

Chronic myeloid leukaemia (CML) is characterised by a progression from a chronic towards an acute phase. We previously reported that signal transducer and activator of transcription 3 (STAT3), a major oncogenic signalling protein, is the target of p210-BCR-ABL in a murine embryonic stem (ES) cell model and in primary CD34+ CML cells. This activation was associated with inhibition of differentiation in ES cells. The present study found that BCR-ABL greatly phosphorylated STAT3 Ser727 residue and, to a lesser extent, Tyr705 residue in BCR-ABL-expressing cell lines (UT7-p210, MO7E-p210, and K562) and in primary CD34+ CML cells. Using BCR-ABL mutants, it was shown that BCR-ABL tyrosine kinase activity and its Tyr177 residue were necessary for STAT3 Ser727 phosphorylation. Constitutive STAT3 Tyr705 phosphorylation was associated with constitutive phosphorylation of Janus kinase (JAK)1 and JAK2, and was inhibited by the JAK inhibitor AG490, suggesting the involvement of JAK proteins in this process. Specific MEK [mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (ERK) kinase] inhibitors PD98056 and UO126, as well as the use of a dominant-negative form of MEK1 abrogated STAT3 Ser727 phosphorylation, suggesting involvement of MAP-Kinase/Erk pathway. Inhibition of BCR-ABL with imatinib mesylate led to a dose-dependent downregulation of total STAT3 protein and mRNA, suggesting that BCR-ABL is involved in the transcriptional regulation of STAT3. Targeting JAK, MEK and STAT3 pathways could therefore be of therapeutic value, especially in advanced stage CML.

Reduced retention of radioprotective hematopoietic cells within the bone marrow microenvironment in CXCR4-/- chimeric mice.

The physiologic role of CXCR4 on hematopoietic stem/progenitor cells (HSPCs) is not fully understood. Here, we show that radioprotection of lethally irradiated mice by embryonic day 14.5 (E14.5) CXCR4-/- fetal liver (FL) cells was markedly impaired when compared with CXCR4+/+ counterparts, but this defect was rescued when hosts were engrafted with high cell numbers. This quantitative defect contrasted with a similar content in hematopoietic colony-forming cells (CFCs), splenic colony-forming units (CFUs-S), and Lin- Sca-1+ c-kit+ cells in E14.5 CXCR4-/- and CXCR4+/+ livers. In addition, the homing of HSPCs in the bone marrow was not altered as detected with a CFSE-staining assay. In contrast, a 30-fold increase in CFCs was seen in the circulation of mice stably reconstituted with CXCR4-/- FL cells and this increment was already observed before hematopoiesis had reached a steady-state level. Together, the data strongly suggest that impaired retention may, at least in short-term hematopoietic reconstitution, lead to a diminution in the number of available progenitors required for radioprotection.

RGS16 is a negative regulator of SDF-1-CXCR4 signaling in megakaryocytes.

Regulators of G-protein signaling (RGS) constitute a family of proteins involved in the negative regulation of signaling through heterotrimeric G protein-coupled receptors (GPCRs). Several RGS proteins have been implicated in the down-regulation of chemokine signaling in hematopoietic cells. The chemokine stromal-cell-derived factor 1 (SDF-1) activates migration of hematopoietic progenitors cells but fails to activate mature megakaryocytes despite high levels of CXC chemokine receptor 4 (CXCR4) receptor expression in these cells. This prompted us to analyze RGS expression and function during megakaryocyte differentiation. We found that RGS16 and RGS18 mRNA expression was up-regulated during this process. Overexpressing RGS16 mRNA in the megakaryocytic MO7e cell line inhibited SDF-1-induced migration, mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) activation, whereas RGS18 overexpression had no effect on CXCR4 signaling. Knocking down RGS16 mRNA via lentiviral-mediated RNA interference increased CXCR4 signaling in MO7e cells and in primary megakaryocytes. Thus, our data reveal that RGS16 is a negative regulator of CXCR4 signaling in megakaryocytes. We postulate that RGS16 regulation is a mechanism that controls megakaryocyte maturation by regulating signals from the microenvironment.

p210BCR-ABL inhibits SDF-1 chemotactic response via alteration of CXCR4 signaling and down-regulation of CXCR4 expression.

It has been shown that p210(BCR-ABL) significantly impairs CXCR4 signaling. We report here that the migratory response to SDF-1 was profoundly altered in blast crisis, whereas chronic-phase CD34(+) cells migrated normally to this chemokine. This migratory defect was associated with a low CXCR4 membrane expression. In vitro STI-571 treatment of CD34(+) cells from patients in blast crisis markedly increased the CXCR4 transcript and CXCR4 membrane expression. Because p210(BCR-ABL) frequently increases with disease progression, we determined the effects of high and low p210(BCR-ABL) expression on CXCR4 protein in the granulocyte macrophage colony-stimulating factor-dependent human cell line MO7e. p210(BCR-ABL) expression distinctly alters CXCR4 protein through two different mechanisms depending on its expression level. At low expression, a signaling defect was detected with no modification of CXCR4 expression. However, higher p210(BCR-ABL) expression induced a marked down-regulation of CXCR4 that is related to its decreased transcription. The effect of p210(BCR-ABL) required its tyrosine kinase activity. Collectively, these data indicate that p210(BCR-ABL) could affect CXCR4 by more than one mechanism and suggest that down-regulation of CXCR4 may have important implications in chronic myelogenous leukemia pathogenesis.

Intracellular localization and constitutive endocytosis of CXCR4 in human CD34+ hematopoietic progenitor cells.

CXCR4, the stromal cell-derived factor-1 receptor, plays an important role in the migration of hematopoietic progenitor/stem cells. The surface and cytoplasmic expression of CXCR4 on human hematopoietic CD34(+) cells was investigated. We show that its surface expression is low, whereas a large part of CXCR4 protein is sequestered intracellularly. Using confocal microscopy, we demonstrated that CXCR4 is colocalized with EEA-1, Rab5, Rab4, and Rab11, which are localized in early and recycling endosomes. No significant colocalization of CXCR4 with lysosomal markers CD63 and Lamp-1 was detected. Using antibody feeding experiments, we report a role for CXCR4 constitutive endocytosis in subcellular localization in stably transduced UT7-CXCR4-GFP and CD34(+) cells. Agonist-independent endocytosis of CXCR4 occurs through clathrin-coated vesicles. These data implicate a constitutive endocytosis in the regulation of CXCR4 membrane expression and suggest that constitutive endocytosis may be involved in the regulation of trafficking the human hematopoietic progenitor/stem cells to and in the bone marrow microenvironment.