Characterization of recombinant human growth differentiation factor-9 signaling in ovarian granulosa cells

GDF9His209GlnfsTer6/S428T and GDF9Q321X/S428T bi-allelic variants caused female subfertility with defective follicle enlargement

BACKGROUND

Antral follicles consist of an oocyte cumulus complex surrounding by somatic cells, including mural granulosa cells as the inner layer and theca cells as the outsider layer. The communications between oocytes and granulosa cells have been extensively explored in in vitro studies, however, the role of oocyte-derived factor GDF9 on in vivo antral follicle development remains elusive due to lack of an appropriate animal model. Clinically, the phenotype of GDF9 variants needs to be determined.

METHODS

Whole-exome sequencing (WES) was performed on two unrelated infertile women characterized by an early rise of estradiol level and defect in follicle enlargement. Besides, WES data on 1,039 women undergoing ART treatment were collected. A Gdf9Q308X/S415T mouse model was generated based on the variant found in one of the patients.

RESULTS

Two probands with bi-allelic GDF9 variants (GDF9His209GlnfsTer6/S428T, GDF9Q321X/S428T) and eight GDF9S428T heterozygotes with normal ovarian response were identified. In vitro experiments confirmed that these variants caused reduction of GDF9 secretion, and/or alleviation in BMP15 binding. Gdf9Q308X/S415T mouse model was constructed, which recapitulated the phenotypes in probands with abnormal estrogen secretion and defected follicle enlargement. Further experiments in mouse model showed an earlier expression of STAR in small antral follicles and decreased proliferative capacity in large antral follicles. In addition, RNA sequencing of granulosa cells revealed the transcriptomic profiles related to defective follicle enlargement in the Gdf9Q308X/S415T group. One of the downregulated genes, P4HA2 (a collagen related gene), was found to be stimulated by GDF9 protein, which partly explained the phenotype of defective follicle enlargement.

CONCLUSIONS

GDF9 bi-allelic variants contributed to the defect in antral follicle development. Oocyte itself participated in the regulation of follicle development through GDF9 paracrine effect, highlighting the essential role of oocyte-derived factors on ovarian response.

Jujuboside A Attenuates Polycystic Ovary Syndrome Based on Estrogen Metabolism Through Activating AhR-mediated CYP1A2 Expression

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women. This study aimed to investigate the therapeutic effects and mechanism of Jujuboside A on PCOS using a dehydroepiandrosterone (DHEA)-induced PCOS mouse model. Estrogen and androgen homeostasis was evaluated in serum from both clinical samples and PCOS mice. The stages of the estrous cycle were determined based on vaginal cytology. The ovarian morphology was observed by stained with hematoxylin and eosin. Moreover, we analyzed protein expression of cytochrome P450 1A1 (CYP1A1), cytochrome P450 1A2 (CYP1A2) and aryl hydrocarbon receptor (AhR) in ovary and KGN cells. Molecular docking, immunofluorescence, and luciferase assay were performed to confirm the activation of AhR by Jujuboside A. Jujuboside A effectively alleviated the disturbance of estrogen homeostasis and restored ovarian function, leading to an improvement in the occurrence and progression of PCOS. Furthermore, the protective effect of JuA against PCOS was dependent on increased CYP1A2 levels regulated by AhR. Our findings suggest that Jujuboside A improves estrogen disorders and may be a potential therapeutic agent for the treatment of PCOS.

Implication of Novel BMP15 and GDF9 Variants in Unexpected Poor Ovarian Response

Unexpected poor ovarian response (UPOR) occurs when nine or fewer oocytes are retrieved from a young patient with normal ovarian reserve. Bone morphogenetic protein15 (BMP15) and growth differentiation factor 9 (GDF9) are two oocyte-specific factors with pivotal role in folliculogenesis. The aim of this study was to assess the relation between BMP15 and GDF9 variants with UPOR. Hundred women aged ≤ 39 with AMH ≥ 1.27 IU/ml participated as UPOR and normal ovarian responders (NOR) based on their oocyte number. Each group consisted of 50 patients. After genomic DNA extraction, the entire exonic regions of BMP15 and GDF9 were amplified and examined by direct sequencing. Western blotting was performed to determine the expression levels of BMP15 and GDF9 in follicular fluid. Additionally, in silico analysis was applied to predict the effect of discovered mutations. From four novel variants of BMP15 and GDF9 genes, silent mutations (c.744 T > C) and (c.99G > A) occurred in both groups, whereas missense variants: c.967-968insA and c.296A > G were found exclusively in UPORs. The latter variants caused reduction in protein expression. Moreover, the mutant allele (T) in a GDF9 polymorphism (C447T) found to be more in NOR individuals (58% NOR vs. 37% UPOR (OR = 2.3, CI 1.32-4.11, p = 0.004).The novel missense mutations which were predicted as damaging, along with other mutations that happened in UPORs might result in ovarian resistance to stimulation. The mutant allele (T) in C447T polymorphism has a protective effect. It can be concluded that there is an association between BMP15 and GDF9 variants and follicular development and ovarian response.

Molecular forms of BMP15 and GDF9 in mammalian species that differ in litter size

Bone morphogenetic protein (BMP15) and growth differentiation factor (GDF9) are critical for ovarian follicular development and fertility and are associated with litter size in mammals. These proteins initially exist as pre-pro-mature proteins, that are subsequently cleaved into biologically active forms. Thus, the molecular forms of GDF9 and BMP15 may provide the key to understanding the differences in litter size determination in mammals. Herein, we compared GDF9 and BMP15 forms in mammals with high (pigs) and low to moderate (sheep) and low (red deer) ovulation-rate. In all species, oocyte lysates and secretions contained both promature and mature forms of BMP15 and GDF9. Whilst promature and mature GDF9 levels were similar between species, deer produced more BMP15 and exhibited, together with sheep, a higher promature:mature BMP15 ratio. N-linked glycosylation was prominant in proregion and mature GDF9 and in proregion BMP15 of pigs, and present in proregion GDF9 of sheep. There was no evidence of secreted native homo- or hetero-dimers although a GDF9 dimer in red deer oocyte lysate was detected. In summary, GDF9 appeared to be equally important in all species regardless of litter size, whilst BMP15 levels were highest in strict monovulatory species.

An ex vivo ovulation system enables the discovery of novel ovulatory pathways and nonhormonal contraceptive candidates†

Ovulation is an integral part of women's menstrual cycle and fertility. Understanding the mechanisms of ovulation has broad implications for the treatment of anovulatory diseases and the development of novel contraceptives. Now, few studies have developed effective models that both faithfully recapitulate the hallmarks of ovulation and possess scalability. We established a three-dimensional encapsulated in vitro follicle growth (eIVFG) system that recapitulates folliculogenesis and produces follicles that undergo ovulation in a controlled manner. Here, we determined whether ex vivo ovulation preserves molecular signatures of ovulation and demonstrated its use in discovering novel ovulatory pathways and nonhormonal contraceptive candidates through a high-throughput ovulation screening. Mature murine follicles from eIVFG were induced to ovulate ex vivo using human chorionic gonadotropin and collected at 0, 1, 4, and 8 hours post-induction. Phenotypic analyses confirmed key ovulatory events, including cumulus expansion, oocyte maturation, follicle rupture, and luteinization. Single-follicle RNA-sequencing analysis revealed the preservation of ovulatory genes and dynamic transcriptomic profiles and signaling. Soft clustering identified distinct gene expression patterns and new pathways that may critically regulate ovulation. We further used this ex vivo ovulation system to screen 21 compounds targeting established and newly identified ovulatory pathways. We discovered that proprotein convertases activate gelatinases to sustain follicle rupture and do not regulate luteinization and progesterone secretion. Together, our ex vivo ovulation system preserves molecular signatures of ovulation, presenting a new powerful tool for studying ovulation and anovulatory diseases as well as for establishing a high-throughput ovulation screening to identify novel nonhormonal contraceptives for women.

Resolving the challenge of insoluble production of mature human growth differentiation factor 9 protein (GDF9) in E. coli using bicistronic expression with thioredoxin

Growth differentiation factor 9 (GDF9) is an oocyte-derived protein with fundamental functions in folliculogenesis. While the crucial contributions of GDF9 in follicular survival have been revealed, crystallographic studies of GDF9 structure have not yet been carried out, essentially due to the insoluble expression of GDF9 in E. coli and lack of appropriate source for structural studies. Therefore, in this study, we investigated the impact of different expression rate of bacterial thioredoxin (TrxA) using bicistronic expression constructs to induce the soluble expression of mature human GDF9 (hGDF9) driven by T7 promoter in E. coli. Our findings revealed that in BL21(DE3), the high rate of TrxA co-expression at 30 °C was sufficiently potent for the soluble expression of hGDF9 and reduction of inclusion body formation by 4 fold. We also successfully confirmed the bioactivity of the purified soluble hGDF9 protein by evaluation of follicle-stimulating hormone receptor gene expression in bovine cumulus cells derived from small follicles. This study is the first to present an effective approach for expression of bioactive form of hGDF9 using TrxA co-expression in E. coli, which may unravel the current issues regarding structural analysis of hGDF9 protein and consequently provide a better insight into hGDF9 functions and interactions.

A variant of human growth differentiation factor-9 that improves oocyte developmental competence

Growth differentiation factor-9 (GDF9) and bone morphogenetic protein-15 (BMP15) are co-expressed exclusively in oocytes throughout most of folliculogenesis and play central roles in controlling ovarian physiology. Although both growth factors exist as homodimers, recent evidence indicates that GDF9 and BMP15 can also heterodimerize to form the potent growth factor cumulin. Within the cumulin complex, BMP15 "activates" latent GDF9, enabling potent signaling in granulosa cells via type I receptors (i.e. activin receptor-like kinase-4/5 (ALK4/5)) and SMAD2/3 transcription factors. In the cumulin heterodimer, two distinct type I receptor interfaces are formed compared with homodimeric GDF9 and BMP15. Previous studies have highlighted the potential of cumulin to improve treatment of female infertility, but, as a noncovalent heterodimer, cumulin is difficult to produce and purify without contaminating GDF9 and BMP15 homodimers. In this study we addressed this challenge by focusing on the cumulin interface formed by the helix of the GDF9 chain and the fingers of the BMP15 chain. We demonstrate that unique BMP15 finger residues at this site (Arg³⁰¹, Gly³⁰⁴, His³⁰⁷, and Met³⁶⁹) enable potent activation of the SMAD2/3 pathway. Incorporating these BMP15 residues into latent GDF9 generated a highly potent growth factor, called hereafter Super-GDF9. Super-GDF9 was >1000-fold more potent than WT human GDF9 and 4-fold more potent than cumulin in SMAD2/3-responsive transcriptional assays in granulosa cells. Our demonstration that Super-GDF9 can effectively promote mouse cumulus cell expansion and improve oocyte quality in vitro represents a potential solution to the current challenges of producing and purifying intact cumulin.

Variation in zygotic CRISPR/Cas9 gene editing outcomes generates novel reporter and deletion alleles at the Gdf11 locus

Recent advances in CRISPR/Cas gene editing technology have significantly expanded the possibilities and accelerated the pace of creating genetically engineered animal models. However, CRISPR/Cas-based strategies designed to precisely edit the genome can often yield unintended outcomes. Here, we report the use of zygotic CRISPR/Cas9 injections to generate a knock-in GFP reporter mouse at the Gdf11 locus. Phenotypic and genomic characterization of founder animals from these injections revealed a subset that contained the correct targeting event and exhibited GFP expression that, within the hematopoietic system, was restricted predominantly to lymphoid cells. Yet, in another subset of founder mice, we detected aberrant integration events at the target site that dramatically and inaccurately shifted hematopoietic GFP expression from the lymphoid to the myeloid lineage. Additionally, we recovered multiple Gdf11 deletion alleles that modified the C-terminus of the GDF11 protein. When bred to homozygosity, most of these alleles recapitulated skeletal phenotypes reported previously for Gdf11 knockout mice, suggesting that these represent null alleles. However, we also recovered one Gdf11 deletion allele that encodes a novel GDF11 variant protein ("GDF11-WE") predicted to contain two additional amino acids (tryptophan (W) and glutamic acid (E)) at the C-terminus of the mature ligand. Unlike the other Gdf11 deletion alleles recovered in this study, homozygosity for the Gdf11WE allele did not phenocopy Gdf11 knockout skeletal phenotypes. Further investigation using in vivo and in vitro approaches demonstrated that GDF11-WE retains substantial physiological function, indicating that GDF11 can tolerate at least some modifications of its C-terminus and providing unexpected insights into its biochemical activities. Altogether, our study confirms that one-step zygotic injections of CRISPR/Cas gene editing complexes provide a quick and powerful tool to generate gene-modified mouse models. Moreover, our findings underscore the critical importance of thorough characterization and validation of any modified alleles generated by CRISPR, as unintended on-target effects that fail to be detected by simple PCR screening can produce substantially altered phenotypic readouts.

GDF-9 and BMP-15 direct the follicle symphony. J Assist Reprod Genet. 2018;35:1741-1750. [PMID: 30039232 DOI: 10.1007/s10815-018-1268-4]

Understanding the physiology underlying the complex dialog between the oocyte and its surrounding somatic cells within the ovarian follicle has been crucial in defining optimal procedures for the development of clinical approaches in ART for women suffering from infertility and ovarian dysfunction. Recent studies have implicated oocyte-secreted factors like growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15), members of the transforming growth factor-beta (TGFβ) superfamily, as potent regulators of folliculogenesis and ovulation. These two factors act as biologically active heterodimers or as homodimers in a synergistic cooperation. Through autocrine and paracrine mechanisms, the GDF-9 and BMP-15 system has been shown to regulate growth, differentiation, and function of granulosa and thecal cells during follicular development playing a vital role in oocyte development, ovulation, fertilization, and embryonic competence. The present mini-review provides an overview of recent findings relating GDF-9 and BMP-15 as fundamental factors implicated in the regulation of ovarian function and discusses their potential role as markers of oocyte quality in women.

Molecular Aspects and Clinical Relevance of GDF9 and BMP15 in Ovarian Function

Growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-secreted factors with a leading role in the control of ovarian function in female reproduction, modulating both the cell fate of the somatic granulosa cells and the quality and developmental competence of the egg. This short review aims to consolidate the molecular aspects of GDF9 and BMP15 and their integral actions in female fertility to understand particularly their effects on oocyte quality and fetal growth. The significant consequences of mutations in the GDF9 and BMP15 genes in women with dizygotic twins as well as the clinical relevance of these oocyte factors in the pathogenesis of primary ovarian insufficiency and polycystic ovary syndrome are also addressed.

Signalling pathways involved in the synergistic effects of human growth differentiation factor 9 and bone morphogenetic protein 15

Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) act synergistically to regulate granulosa cell proliferation and steroid production in several species. Several non-Sma and mothers against decapentaplegic (SMAD) signalling pathways are involved in the action of murine and ovine GDF9 and BMP15 in combination, with the pathways utilised differing between the two species. The aims of this research were to determine if human GDF9 and BMP15 also act in a synergistic manner to stimulate granulosa cell proliferation and to identify which non-SMAD signalling pathways are activated. Human GDF9 with BMP15 (GDF9+BMP15) stimulated an increase in (3)H-thymidine incorporation (P<0.001), which was greater than the increase with BMP15 alone, while GDF9 alone had no effect. The stimulation of (3)H-thymidine incorporation by GDF9+BMP15 was reduced by the addition of inhibitors to the SMAD2/3, nuclear factor-KB (NF-KB) and c-Jun N-terminal kinase (JNK) signalling pathways. Inhibitors to the SMAD1/5/8, extracellular signal-regulated kinase mitogen-activated protein kinase (ERK-MAPK) or p38-MAPK pathways had no effect. The addition of the BMP receptor 2 (BMPR2) extracellular domain also inhibited stimulation of (3)H-thymidine incorporation by GDF9+BMP15. In conclusion, human GDF9 and BMP15 act synergistically to stimulate granulosa cell proliferation, a response that also involves species-specific non-SMAD signalling pathways.

Porcine oocyte maturation in vitro: role of cAMP and oocyte-secreted factors - A practical approach

Polyspermy or the penetration of more than one sperm cell remains a problem during porcine in vitro fertilization (IVF). After in vitro culture of porcine zygotes, only a low percentage of blastocysts develop and their quality is inferior to that of in vivo derived blastocysts. It is unknown whether the cytoplasmic maturation of the oocyte is sufficiently sustained in current in vitro maturation (IVM) procedures. The complex interplay between oocyte and cumulus cells during IVM is a key factor in this process. By focusing on this bidirectional communication, it is possible to control the coordination of cumulus expansion, and nuclear and cytoplasmic maturation during IVM to some extent. Therefore, this review focuses on the regulatory mechanisms between oocytes and cumulus cells to further the development of new in vitro embryo production (IVP) procedures, resulting in less polyspermy and improved oocyte developmental potential. Specifically, we focused on the involvement of cAMP in maturation regulation and function of oocyte-secreted factors (OSFs) in the bidirectional regulatory loop between oocyte and cumulus cells. Our studies suggest that maintaining high cAMP levels in the oocyte during the first half of IVM sustained improved oocyte maturation, resulting in an enhanced response after IVF and cumulus matrix disassembly. Recent research indicated that the addition of OSFs during IVM enhanced the developmental competence of small follicle-derived oocytes, which was stimulated by epidermal growth factor (EGF) via developing EGF-receptor signaling.

Modifications of human growth differentiation factor 9 to improve the generation of embryos from low competence oocytes

Growth differentiation factor 9 (GDF9) is an oocyte-derived growth factor that plays a critical role in ovarian folliculogenesis and oocyte developmental competence and belongs to the TGF-β family of proteins. Recombinant human GDF9 (hGDF9) is secreted in a latent form, which in the case of the fully processed protein, has the proregion noncovalently associated with the mature region. In this study, we investigated a number of amino acid residues in the mature region of hGDF9 that are different from the corresponding residues in the mouse protein, which is not latent. We designed, expressed, and purified 4 forms of chimeric hGDF9 (M1-M4) that we found to be active in a granulosa cell bioassay. Using a porcine in vitro maturation model with inherent low developmental competence (yielding 10%-20% blastocysts), we tested the ability of the chimeric hGDF9 proteins to improve oocyte maturation and developmental competence. Interestingly, one of the chimeric proteins, M3, was able to significantly increase the level of embryo production using such low competence oocytes. Our molecular modeling studies suggest that in the case of hGDF9 the Gly(391)Arg mutation probably increases receptor binding affinity, thereby creating an active protein for granulosa cells in vitro. However, for an improvement in oocyte developmental competence, a second mutation (Ser(412)Pro), which potentially decreases the affinity of the mature region for the proregion, is also required.

Cumulin, an Oocyte-secreted Heterodimer of the Transforming Growth Factor-β Family, Is a Potent Activator of Granulosa Cells and Improves Oocyte Quality

Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-specific growth factors with central roles in mammalian reproduction, regulating species-specific fecundity, ovarian follicular somatic cell differentiation, and oocyte quality. In the human, GDF9 is produced in a latent form, the mechanism of activation being an open question. Here, we produced a range of recombinant GDF9 and BMP15 variants, examined their in silico and physical interactions and their effects on ovarian granulosa cells (GC) and oocytes. We found that the potent synergistic actions of GDF9 and BMP15 on GC can be attributed to the formation of a heterodimer, which we have termed cumulin. Structural modeling of cumulin revealed a dimerization interface identical to homodimeric GDF9 and BMP15, indicating likely formation of a stable complex. This was confirmed by generation of recombinant heterodimeric complexes of pro/mature domains (pro-cumulin) and covalent mature domains (cumulin). Both pro-cumulin and cumulin exhibited highly potent bioactivity on GC, activating both SMAD2/3 and SMAD1/5/8 signaling pathways and promoting proliferation and expression of a set of genes associated with oocyte-regulated GC differentiation. Cumulin was more potent than pro-cumulin, pro-GDF9, pro-BMP15, or the two combined on GC. However, on cumulus-oocyte complexes, pro-cumulin was more effective than all other growth factors at notably improving oocyte quality as assessed by subsequent day 7 embryo development. Our results support a model of activation for human GDF9 dependent on cumulin formation through heterodimerization with BMP15. Oocyte-secreted cumulin is likely to be a central regulator of fertility in mono-ovular mammals.

Mechanisms of BMP-Receptor Interaction and Activation

Bone morphogenetic proteins (BMPs), together with the eponymous transforming growth factor (TGF) β and the Activins form the TGFβ superfamily of ligands. This protein family comprises more than 30 structurally highly related proteins, which determine formation, maintenance, and regeneration of tissues and organs. Their importance for the development of multicellular organisms is evident from their existence in all vertebrates as well as nonvertebrate animals. From their highly specific functions in vivo either a strict relation between a particular ligand and its cognate cellular receptor and/or a stringent regulation to define a distinct temperospatial expression pattern for the various ligands and receptor is expected. However, only a limited number of receptors are found to serve a large number of ligands thus implicating highly promiscuous ligand-receptor interactions instead. Since in tissues a multitude of ligands are often found, which signal via a highly overlapping set of receptors, this raises the question how such promiscuous interactions between different ligands and their receptors can generate concerted and highly specific cellular signals required during embryonic development and tissue homeostasis.

GDF9 is transiently expressed in oocytes before follicle formation in the human fetal ovary and is regulated by a novel NOBOX transcript

During human fetal ovary development, the process of primordial follicle formation is immediately preceded by a highly dynamic period of germ cell and somatic cell reorganisation. This is regulated by germ-cell specific transcription regulators, by the conserved RNA binding proteins DAZL and BOLL and by secreted growth factors of the TGFβ family, including activin βA: these all show changing patterns of expression preceding follicle formation. In mice, the transcription factor Nobox is essential for follicle formation and oocyte survival, and NOBOX regulates the expression of GDF9 in humans. We have therefore characterised the expression of GDF9 in relation to these known key factors during follicle formation in the human fetal ovary. mRNA levels of GDF9, BMP15 and NOBOX were quantified by qRT-PCR and showed dramatic increases across gestation. GDF9 protein expression was localised by immunohistochemistry to the same population of germ cells as those expressing activin βA prior to follicle formation but did not co-localise with either BOLL or DAZL. A novel NOBOX isoform was identified in fetal ovary that was shown to be capable of up-regulating the GDF9 promoter in reporter assays. Thus, during oogenesis in humans, oocytes go through a dynamic and very sharply demarcated sequence of changes in expression of these various proteins, even within individual germ cell nests, likely to be of major functional significance in determining selective germ cell survival at this key stage in ovarian development. Transcriptional variation may contribute to the range of age of onset of POI in women with NOBOX mutations.

Mouse GDF9 decreases KITL gene expression in human granulosa cells

Kit ligand (KITL) is an important granulosa cell-derived growth factor in ovarian folliculogenesis, but its expression and function in human granulosa cells are currently poorly understood. Based on studies performed in animal models, it was hypothesised that KITL gene expression in human granulosa cells is regulated by androgens and/or growth differentiation factor 9 (GDF9). We utilised two models of human granulosa cells, the KGN granulosa tumour cell line and cumulus granulosa cells obtained from preovulatory follicles of women undergoing assisted reproduction. Cells were treated with combinations of 5α-dihydrotestosterone (DHT), recombinant mouse GDF9, and the ALK4/5/7 inhibitor SB431542. KITL mRNA levels were measured by quantitative real-time PCR. No change in KITL mRNA expression was observed after DHT treatment under any experimental conditions, but GDF9 treatment resulted in a significant decrease in KITL mRNA levels in both KGN and cumulus cells. The effect of GDF9 was abolished by the addition of SB431542. These results indicate that KITL is not directly regulated by androgen signalling in human granulosa cells. Moreover, this study provides the first evidence that GDF9 negatively regulates KITL gene expression in human granulosa cells providing new information on the regulation of these important growth factors in the human ovary.

Bone morphogenetic protein 15 in the pro-mature complex form enhances bovine oocyte developmental competence

Developmental competence of in vitro matured (IVM) oocytes needs to be improved and this can potentially be achieved by adding recombinant bone morphogenetic protein 15 (BMP15) or growth differentiation factor (GDF9) to IVM. The aim of this study was to determine the effect of a purified pro-mature complex form of recombinant human BMP15 versus the commercially available bioactive forms of BMP15 and GDF9 (both isolated mature regions) during IVM on bovine embryo development and metabolic activity. Bovine cumulus oocyte complexes (COCs) were matured in vitro in control medium or treated with 100 ng/ml pro-mature BMP15, mature BMP15 or mature GDF9 +/− FSH. Metabolic measures of glucose uptake and lactate production from COCs and autofluorescence of NAD(P)H, FAD and GSH were measured in oocytes after IVM. Following in vitro fertilisation and embryo culture, day 8 blastocysts were stained for cell numbers. COCs matured in medium +/− FSH containing pro-mature BMP15 displayed significantly improved blastocyst development (57.7±3.9%, 43.5±4.2%) compared to controls (43.3±2.4%, 28.9±3.7%) and to mature GDF9+FSH (36.1±3.0%). The mature form of BMP15 produced intermediate levels of blastocyst development; not significantly different to control or pro-mature BMP15 levels. Pro-mature BMP15 increased intra-oocyte NAD(P)H, and reduced glutathione (GSH) levels were increased by both forms of BMP15 in the absence of FSH. Exogenous BMP15 in its pro-mature form during IVM provides a functional source of oocyte-secreted factors to improve bovine blastocyst development. This form of BMP15 may prove useful for improving cattle and human artificial reproductive technologies.

Effects of differing oocyte-secreted factors during mouse in vitro maturation on subsequent embryo and fetal development

PURPOSE

We hypothesised that varying native oocyte-secreted factor (OSF) exposure or using different recombinant OSF peptides would have differential effects on post-in vitro maturation (IVM) embryo and fetal development.

METHODS

Mouse cumulus oocyte complexes (COCs) were treated with the purified mature domain of GDF9 and/or BMP15 or were co-cultured with denuded oocytes (DOs) from 0 h or 3 h of IVM. DOs were matured for 3 h as either intact COCs+/-FSH before denuding, or as DOs + FSH. COCs were fertilised and blastocyst development was assessed on days 5 and 6, and either differentially stained for ICM numbers or vitrified/warmed embryos were transferred to recipients to assess implantation and fetal rates.

RESULTS

No improvement in embryo development was observed with the addition of GDF9 and/or BMP15 to IVM. In contrast, embryos derived from COCs co-cultured with DOs had significantly improved blastocyst rates and ICM numbers compared to controls (P < 0.05). The highest response was obtained when DOs were first added to COCs at 3 h of IVM, after being pre-treated (0-3 h) as COCs + FSH. Compared to control, co-culture with DOs from 3 h did not affect implantation rates but more than doubled fetal yield (21% vs 48%; P < 0.05). GDF9 Western blot analysis was unable to detect any differences in quantity or form of GDF9 (17 and 65 kDa) in extracts of DO at 0 h or 3 h.

CONCLUSIONS

This study provides new knowledge on means to improve oocyte quality in vitro which has the potential to significantly aid human infertility treatment and animal embryo production technologies.

Identification of a mutation in GDF9 as a novel cause of diminished ovarian reserve in young women

STUDY QUESTION

Do any mutations in growth differentiation factor 9 (GDF9) have a role in diminished ovarian reserve (DOR) in young women?

SUMMARY ANSWER

The GDF9 p.R146C mutation may be a source of DOR in some young women.

WHAT IS KNOWN ALREADY

DOR affects 10% of women under 37 years of age and is associated with accelerated expenditure of follicles. GDF9 is an oocyte-secreted factor that plays a critical role in follicular development and female fertility. Several GDF9 variants have been linked to ovarian dysfunction.

STUDY DESIGN, SIZE, DURATION

This case-control study included 139 women with DOR and 152 controls aged under 37 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All women were recruited in a Chinese tertiary center and underwent DNA sequencing of GDF9 gene. We then determined the molecular and biological properties of mutant GDF9 proteins using protein expression, structural prediction and functional analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified two mutations in the proregion of GDF9 gene: c.169T > G (p.D57Y) and c.436T > C (p.R146C). The p.R146C mutation was found in three women with DOR but was absent in the control population. This mutation was also associated with significant reductions in GDF9 mature protein secretion in cultured cells. Functional studies with human granulosa cells (GCs) showed that the p.R146C mutation reduced the abilities of GDF9 to stimulate GC proliferation and to activate the Smad2 pathway. Protein structure modeling predicted that p.R146C disrupted an α-helix in GDF9 protein. In contrast with p.R146C, the p.D57Y mutation, found in both the DOR and control groups (6 versus 2), had no obvious deleterious effects.

LIMITATIONS, REASONS FOR CAUTION

Larger studies in varying populations may validate the role of GDF9 mutation in young women with DOR.

WIDER IMPLICATIONS OF THE FINDINGS

These results may provide new insights into the pathophysiological mechanisms of early-onset DOR.

The Rho-GEF Trio regulates a novel pro-inflammatory pathway through the transcription factor Ets2

Inflammation is characterized by endothelium that highly expresses numerous adhesion molecules to trigger leukocyte extravasation. Central to this event is increased gene transcription. Small Rho-GTPases not only control the actin cytoskeleton, but are also implicated in gene regulation. However, in inflammation, it is not clear how this is regulated. Here, we show that the guanine-nucleotide exchange factor Trio expression is increased upon inflammatory stimuli in endothelium. Additionally, increased Trio expression was found in the vessel wall of rheumatoid arthritis patients. Trio silencing impaired VCAM-1 expression. Finally, we excluded that Trio-controlled VCAM-1 expression used the classical NFκB or MAP-kinase pathways, but rather acts on the transcriptional level by increasing phosphorylation and nuclear translocalization of Ets2. These data implicate Trio in regulating inflammation and provide novel targets for therapeutic purposes to treat inflammatory diseases such as rheumatoid arthritis.

Heparan sulfate proteoglycans regulate responses to oocyte paracrine signals in ovarian follicle morphogenesis

In the ovarian follicle, oocyte-secreted factors induce cumulus-specific genes and repress mural granulosa cell specific genes to establish these functionally distinct cell lineages. The mechanism establishing this precise morphogenic pattern of oocyte signaling within the follicle is unknown. The present study investigated a role for heparan sulphate proteoglycans (HSPG) as coreceptors mediating oocyte secreted factor signaling. In vitro maturation of cumulus oocyte complexes in the presence of exogenous heparin, which antagonizes HSPG signaling, prevented cumulus expansion and blocked the induction of cumulus-specific matrix genes, Has2 and Tnfaip6, whereas conversely, the mural granulosa-specific genes, Lhcgr and Cyp11a1, were strongly up-regulated. Heparin also blocked phosphorylation of SMAD2. Exogenous growth differentiation factor (GDF)-9 reversed these heparin effects; furthermore, GDF9 strongly bound to heparin sepharose. These observations indicate that heparin binds endogenous GDF9 and disrupts interaction with heparan sulphate proteoglycan coreceptor(s), important for GDF9 signaling. The expression of candidate HSPG coreceptors, Syndecan 1-4, Glypican 1-6, and Betaglycan, was examined. An ovulatory dose of human chorionic gonadotropin down-regulated Betaglycan in cumulus cells, and this regulation required GDF9 activity; conversely, Betaglycan was significantly increased in luteinizing mural granulosa cells. Human chorionic gonadotropin caused very strong induction of Syndecan 1 and Syndecan 4 in mural granulosa as well as cumulus cells. Glypican 1 was selectively induced in cumulus cells, and this expression appeared dependent on GDF9 action. These data suggest that HSPG play an essential role in GDF9 signaling and are involved in the patterning of oocyte signaling and cumulus cell function in the periovulatory follicle.

A covalently dimerized recombinant human bone morphogenetic protein-15 variant identifies bone morphogenetic protein receptor type 1B as a key cell surface receptor on ovarian granulosa cells

Genetic studies have identified bone morphogenetic protein-15 (BMP15) as an essential regulator of female fertility in humans and in sheep. Oocyte-derived BMP15 is a noncovalently linked dimeric growth factor mediating its effects to ovarian somatic cells in a paracrine manner. Although receptor ectodomains capable of binding BMP15 have previously been reported, no cell surface receptor complex involved in BMP15 signaling has previously been characterized. Here we have expressed and purified recombinant human BMP15 noncovalent and covalent dimer variants. The biological effects of these BMP15 variants were assessed in cultured human granulosa-luteal cells or COV434 granulosa cell tumor cells using BMP-responsive transcriptional reporter assays and an inhibin B ELISA. Biochemical characterization of ligand-receptor interactions was performed with affinity-labeling experiments using [(125)I]iodinated BMP15 variants. Both ligand variants were shown to form homodimers and to stimulate Smad1/5/8 signaling and inhibin B production in human granulosa cells in a similar manner. [(125)I]Iodination of both ligands was achieved, but only the covalent dimer variant retained receptor binding capacity. The [(125)I]BMP15(S356C) variant bound preferentially to endogenous BMP receptor 1B (BMPR1B) and BMPR2 receptors on COV434 cells. Binding experiments in COS cells with overexpression of these receptors confirmed that the [(125)I]BMP15(S356C) variant binds to BMPR1B and BMPR2 forming the BMP15 signaling complex. The results provide the first direct evidence in any species on the identification of specific cell surface receptors for a member of the GDF9/BMP15 subfamily of oocyte growth factors. The fact that BMP15 uses preferentially BMPR1B as its type I receptor suggests an important role for the BMPR1B receptor in human female fertility. The result is well in line with the demonstration of ovarian failure in a recently reported human subject with a homozygous BMPR1B loss-of-function mutant.

Activation of latent human GDF9 by a single residue change (Gly 391 Arg) in the mature domain

Growth differentiation factor 9 (GDF9) controls granulosa cell growth and differentiation during early ovarian folliculogenesis and regulates cumulus cell function and ovulation rate in the later stages of this process. Similar to other TGF-β superfamily ligands, GDF9 is secreted from the oocyte in a noncovalent complex with its prodomain. In this study, we show that prodomain interactions differentially regulate the activity of GDF9 across species, such that murine (m) GDF9 is secreted in an active form, whereas human (h) GDF9 is latent. To understand this distinction, we used site-directed mutagenesis to introduce nonconserved mGDF9 residues into the pro- and mature domains of hGDF9. Activity-based screens of the resultant mutants indicated that a single mature domain residue (Gly(391)) confers latency to hGDF9. Gly(391) forms part of the type I receptor binding site on hGDF9, and this residue is present in all species except mouse, rat, hamster, galago, and possum, in which it is substituted with an arginine. In an adrenocortical cell luciferase assay, hGDF9 (Gly(391)Arg) had similar activity to mGDF9 (EC(50) 55 ng/ml vs. 28 ng/ml, respectively), whereas wild-type hGDF9 was inactive. hGDF9 (Gly(391)Arg) was also a potent stimulator of murine granulosa cell proliferation (EC(50) 52 ng/ml). An arginine at position 391 increases the affinity of GDF9 for its signaling receptors, enabling it to be secreted in an active form. This important species difference in the activation status of GDF9 may contribute to the variation observed in follicular development, ovulation rate, and fecundity between mammals.

Signalling pathways mediating specific synergistic interactions between GDF9 and BMP15

Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are two proteins selectively expressed in the oocyte which are essential for normal fertility. Both of these proteins are members of the transforming growth factor beta (TGF-β) superfamily and as such are produced as pre-proproteins, existing after proteolytic processing as a complex of the respective pro and mature regions. Previous work has shown that these two proteins interact both at the genetic and cellular signalling levels. In this study, our aim was to determine if the purified mature regions of GDF9 and BMP15 exhibit synergistic interactions on granulosa cells and to determine if such interactions are specific to these two proteins. We have used primary cultures of murine granulosa cells and [(3)H]-thymidine incorporation or transcriptional reporter assays as our readouts. We observed clear synergistic interactions between the mature regions of GDF9 and BMP15 when either DNA synthesis or SMAD3 signalling were examined. GDF9/BMP15 synergistic interactions were specific such that neither factor could be replaced by an analogous TGF-β superfamily member. The GDF9/BMP15 synergistic signalling response was inhibited by the SMAD2/3 phosphorylation inhibitor SB431542, as well as inhibition of the mitogen-activated protein kinase or rous sarcoma oncogene (SRC) signalling pathways, but not the nuclear factor kappa B pathway. In this study, we show that purified mature regions of GDF9 and BMP15 synergistically interact in a specific manner which is not dependent on the presence of a pro-region. This synergistic interaction is targeted at the SMAD3 pathway, and is dependent on ERK1/2 and SRC kinase signalling.

Recent insights into oocyte-follicle cell interactions provide opportunities for the development of new approaches to in vitro maturation

The last 5-10 years of research in ovarian and oocyte biology has delivered some major new advances in knowledge of the molecular and cellular processes regulating oocyte maturation and oocyte developmental competence. These new insights include, among others: (1) the knowledge that oocytes regulate granulosa and cumulus cell differentiation, ovulation rate and fertility via the secretion of soluble paracrine growth factors; (2) new perspectives on the participation of cyclic nucleotides, phosphodiesterases and gap junctions in the regulation of oocyte meiotic arrest and resumption; and (3) the new appreciation of the mechanisms of LH-induced oocyte maturation and ovulation mediated by the follicular cascade of epidermal growth factor (EGF)-like peptides, the EGF receptor and their intracellular second messengers. These recent insights into oocyte-follicle cell interactions provide opportunities for the development of new approaches to oocyte in vitro maturation (IVM). Laboratory IVM methodologies have changed little over the past 20-30 years and IVM remains notably less efficient than hormone-stimulated IVF, limiting its wider application in reproductive medicine and animal breeding. The challenge for oocyte biologists and clinicians practicing IVM is to modernise clinical IVM systems to benefit from these new insights into oocyte-follicle cell interactions in vivo.

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.

Integral role of GDF-9 and BMP-15 in ovarian function

The oocyte plays an important role in regulating and promoting follicle growth, and thereby its own development, by the production of oocyte growth factors that predominantly act on supporting granulosa cells via paracrine signaling. Genetic studies in mice demonstrated critical roles of two key oocyte-derived growth factors belonging to the transforming growth factor-β (TGF-β) superfamily, growth and differentiation factor-9 (GDF-9) and bone morphogenetic protein-15 (BMP-15), in ovarian function. The identification of Bmp15 and Gdf9 gene mutations as the causal mechanism underlying the highly prolific or infertile nature of several sheep strains in a dosage-sensitive manner also highlighted the crucial role these two genes play in ovarian function. Similarly, large numbers of mutations in the GDF9 and BMP15 genes have been identified in women with premature ovarian failure and in mothers of dizygotic twins. The purpose of this article is to review the genetic studies of GDF-9 and BMP-15 mutations identified in women and sheep, as well as describing the various knockout and overexpressing mouse models, and to summarize the molecular and biological functions that underlie the crucial role of these two oocyte factors in female fertility.

The role of oocyte-secreted factors GDF9 and BMP15 in follicular development and oogenesis

Ovarian physiology is controlled by endocrine and paracrine signals, and the transforming growth factor β (TGFβ) superfamily has a pivotal role in this control. The Bone morphogenetic protein 15 (BMP15) and Growth differentiation factor 9 (GDF9) genes are relevant members of the TGFβ superfamily that encode proteins secreted by the oocytes into the ovarian follicles. Through a paracrine signalling pathway, these factors induce the follicular somatic cells to undergo mitosis and differentiation during follicular development. These events are controlled by a mutually dependent and coordinated fashion during the formation of the granulosa cell layers. Many studies have contributed to our knowledge concerning the paracrine factors acting within the follicular environment, especially regarding GDF9 and BMP15. We aimed to review the relevant contributions of these two genes to animal reproductive physiology.

Impaired production of BMP-15 and GDF-9 mature proteins derived from proproteins WITH mutations in the proregion

Mutations in the bone morphogenetic protein-15 (BMP-15) and growth and differentiation factor-9 (GDF-9) genes have been identified in women with primary ovarian insufficiency (POI) and mothers of dizygotic twins. Here, we show that biological activities of the conditioned media from human embryonic kidney 293F cells transfected with two representative BMP-15 and GDF-9 mutants identified in the affected women have significantly reduced biological activities compared with the corresponding wild-type. Moreover, this difference is due to decreased production of the mature proteins, attributed most likely to impaired posttranslational processing of the proprotein. As genetic studies of the BMP-15 and/or GDF-9 genes in ewes established that a reduction of these proteins is associated with an increased ovulation rate, it is conceivable that women affected with these mutations may have an increased probability of bearing dizygotic twins during active reproductive ages before diagnosis with POI at later ages due to an earlier exhaustion of ovarian reserve.

Transcription factors and ovarian functions

This study represents a first review of contemporarily knowledge concerning involvement of transcription factors in control of different ovarian functions. After introduction of basic functions and classification of transcription factors, the available data concerning involvement of transcription factors in control of the following ovarian events are present: follicular development and selection, ovarian cell proliferation and cancerogenesis, ovarian cell apoptosis, ovarian secretory activity, oocyte/cumulus maturation, ovulation and luteogenesis, mediation effect of hormones, growth factors, and cytokines. The importance of transcription factors of Smad family, of forkhead transcription factor (Fox) family, of breast cancer-associated genes/transcription factor, hypoxia-induced transcription factors and of other transcription factors in control of these processes has been demonstrated.

Assessment of the quality and structural integrity of a complex glycoprotein mixture following extraction from the formulated biopharmaceutical drug product

Biological drugs represent an important and rapidly growing class of therapeutics useful in the treatment of a variety of disorders ranging from cancer to inflammation to infectious diseases. Unlike single chemical entities, the recombinant production of these drugs in living cells confers considerable structural and chemical heterogeneity to the biologically derived protein product that constitutes the active pharmaceutical ingredient (API). In mammalian based expression systems, much of this diversity is conferred through heterogeneous protein glycosylation. These post-translational modifications can have significant effects on the structure, biological function, and pharmacological properties of the API. In addition, the bulk proteins that comprise the API are further formulated through the use of multiple excipients designed to ensure product stability, solubility, and lot-to-lot consistency. Unfortunately, these matrices can interfere with commonly available analytical methods used in the thorough chemical characterization of the biological drug product. At the same time, a demonstration of the suitable extraction of the bulk drug substance in a manner and form that does not destabilize the active ingredient or introduce any structural bias with direct reference to the original drug product is both critical and necessary. Here, we use recombinant human follicle stimulating hormone (follitropin alpha for injection) from a pharmaceutical source as an example to illustrate a suitable purification strategy to effectively extract the bulk drug substance from the formulated drug product with high purity and yield. We assess the suitability of this extraction method in preserving the structural integrity and overall quality of the drug substance relative to the formulated drug product, placing a particular emphasis on glycosylation as a key product attribute. In so doing, we demonstrate that it is possible to effectively extract the active pharmaceutical ingredient from a formulated biological drug product in a manner that is consequently sufficient for its use in comparability studies.

Inhibin and premature ovarian failure

BACKGROUND

Elucidation of the causes of premature ovarian failure (POF) is difficult due to the heterogeneity of the condition. Inhibin is a potential candidate gene for POF based on its dual actions on FSH secretion by the pituitary and gametogenesis in the gonads. A missense mutation in the inhibin alpha subunit gene (INHA G769A) is associated with POF in several populations. However, there is phenotypic heterogeneity in INHA G769A mutation carriers.

METHODS

Relevant studies were identified by searching PubMed and mutational frequencies combined for meta-analysis.

RESULTS

Meta-analysis of published studies revealed a risk difference of 0.04 (-0.030 to 0.11). The occurrence of asymptomatic carriers in populations suggests incomplete penetrance and/or a multi-genetic cause of POF. We propose that a decline in inhibin bioactivity caused by the mutation could increase FSH levels; and in a susceptible individual, the heightened sensitivity to gonadotrophins causes POF. Impaired paracrine effects of inhibin could impact folliculogenesis due to reduced antagonism of activin, bone morphogenetic protein 15 and growth differentiation factor 9. Functional studies of this mutation indicate normal production of dimeric inhibin A and B and impaired bioactivity of inhibin B.

CONCLUSIONS

The identification of an autosomal mutation in the inhibin alpha subunit gene that is significantly linked to POF in certain ethnic populations highlights the role of inhibin in the regulation of ovarian biology and fertility. Although the reduction of inhibin B bioactivity by the INHA G769A mutation is clearly not the only cause, evidence suggests that this change may serve as a susceptibility factor, increasing the likelihood of POF.

Inhibition of oocyte growth factors in vivo modulates ovarian folliculogenesis in neonatal and immature mice

Growth differentiation factor-9 (GDF9) and bone morphogenetic protein-15 (BMP15) are among the key regulators transmitting the signaling between the oocyte and the surrounding granulosa cells. Previously, it has been shown that a recombinant BMP type II receptor ectodomain-Fc fusion protein (BMPR2ecd-Fc) is able to inhibit the actions of GDF9 and BMP15 in vitro. Here, we have produced bioactive BMPR2ecd-Fc, which was injected i.p. into neonatal mice. Early folliculogenesis was first studied by injecting mice five times with various doses of BMPR2ecd-Fc during the postnatal days 4-12. Folliculogenesis was affected dose dependently, as evidenced by a decreased mitogenesis of granulosa cells of the growing follicles. Furthermore, we also noticed a decrease in the number of secondary and tertiary follicles as well as an increase in the oocyte size. Electron microscopic analysis revealed that the ultrastructure of the granulosa cells of the primary follicles was not affected by the BMPR2ecd-Fc treatment. A second study was conducted to investigate whether a longer treatment with 12 injections during postnatal days 4-28 would inhibit folliculogenesis. Similar effects were observed in the two studies on the early follicular developmental stages. However, in the long-term study, later stages of folliculogenesis were not blocked but rather increased numbers of antral follicles, preovulatory follicles, and corpora lutea were found. We conclude that BMPR2ecd-Fc is a potent modulator of ovarian folliculogenesis in vivo, and thus, is a valuable tool for studying the physiology and downstream effects of oocyte-derived growth factors in vivo.

Stable expression and characterization of N-terminal tagged recombinant human bone morphogenetic protein 15

Oocyte-derived growth factors are critically involved in multiple ovarian processes via paracrine actions. Although recombinant proteins have been applied to dissect the physiological functions of these factors, variation of activities among different protein preparations remains an issue. To further elucidate the roles of one of these growth factors, bone morphogenetic protein 15 (BMP15), in mediating oocyte-regulated molecular and cellular events and to explore its potential clinical application, we engineered the human BMP15 sequence to efficiently produce bioactive recombinant human BMP15 (rhBMP15). The proteolytic cleavage site of the hBMP15 precursor was optimized to facilitate the production of the mature protein, and a FLAG-tag was placed at the N-terminus of the mature region to ease purification and avoid potential interference of the tag with the cystine knot structure. The rhBMP15 protein was purified using anti-FLAG M2 affinity gel. Our results demonstrated that the N-terminal tagged rhBMP15 was efficiently processed in HEK-293 cells. Furthermore, the purified rhBMP15 could activate SMAD1/5/8 and induce the transcription of genes encoding cumulus expansion-related transcripts (Ptx3, Has2, Tnfaip6 and Ptgs2), inhibitory SMADs (Smad6 and Smad7), BMP antagonists (Grem1 and Fst), activin/inhibin betaA (Inhba) and betaB (Inhbb) subunits, etc. Thus, our rhBMP15 containing a genetically modified cleavage sequence and an N-terminal FLAG-tag can be efficiently produced, processed and secreted in a mammalian expression system. The purified rhBMP15 is also biologically active and very stable, and can induce the expression of a variety of mouse granulosa cell genes.

Bone morphogenetic proteins in orthopaedic surgery

Bone healing is a predictable process that has a high rate of success. For some patients, and in certain clinical settings, this process can be delayed or completely inhibited. This leads to significant morbidity and may also result in time lost from work, costs related to prolonged medical treatment, and continued pain at the site of nonunion or failed spinal fusion. Several growth factors, specifically BMP-2 and BMP-7, have been approved in several countries for specific indications. The use of these products and potential complications of their use are reviewed.

Oocyte peptides as paracrine tools for ovarian stimulation and oocyte maturation

Recent studies report the production and isolation of a stable bioactive recombinant human bone morphogenetic protein 15 (rhBMP15) that is appropriately processed in HEK-293 cells and activates the SMAD 1/5/8 pathway in mouse granulosa cell cultures. Further, the purified rhBMP15 induces the expression of genes associated with cumulus expansion. Thanks to recent research, we have a greater understanding of the importance of the dialogue that occurs between the oocyte and the granulosa cell layer with regard to regulating folliculogenesis and the acquisition of oocyte developmental competence and maturation. BMP15 is one of the critical components of these intra-follicular communication pathways. The production of recombinant human BMP15 is important for understanding the biochemistry of this specific pathway and for also fully understanding its functional contributions to mediating oocyte development. The production of a stable recombinant human BMP15 is also important for use in experiments aimed at optimizing ovarian stimulation protocols and in vitro oocyte maturation methods. This is required to improve oocyte and embryonic developmental competence and increase our ability to effectively use in vitro methods for animal production and the treatment of human infertility.

Oocyte-specific genes: role in fertility and infertility

Genetic determinations of oocyte and ovarian follicle growth are still not well understood. Genes specifically expressed on oocytes seem to play an important role in these processes. Oocyte-specific genes are also involved in ovulation and early embryogenesis processes. Studies on the identification and characterization of new oocyte-specific genes can help in our understanding of cardinal fertility and infertility mechanisms. They can also be candidate genes for reproductive disorders such as polycystic ovary syndrome, premature ovarian failure and infertility. Infertility is an important worldwide problem affecting around 15% of couples. Approximately 20% of infertility is referred as idiopathic infertility. Studies on these genes could improve the diagnostic and therapeutic procedures of human infertility.

[Signal transduction of BMP/Smad and its relationship with mammalian folliculogenesis]

BMPs belong to the transforming growth factor-b superfamily. BMPs have been proved to have extensive biological functions in mammals, including growth regulation, cell proliferation and differentiation. More and more evidence has shown that BMPs play a key role in fertility, especially in folliculogenesis in female mammals. Smad proteins are intra-cellular signaling transduction molecules of BMP family, which can transduce the BMP signal from the cell membrane to the nucleus. In this review, BMPs, BMP/Smad-related signal transduction and the regulation of BMP activity were summarized, and the regulatory roles of BMP/Smad signal transduction pathway in folliculogenesis were discussed.

Gonadal transcriptome alterations in response to dietary energy intake: sensing the reproductive environment

Reproductive capacity and nutritional input are tightly linked and animals' specific responses to alterations in their physical environment and food availability are crucial to ensuring sustainability of that species. We have assessed how alterations in dietary energy intake (both reductions and excess), as well as in food availability, via intermittent fasting (IF), affect the gonadal transcriptome of both male and female rats. Starting at four months of age, male and female rats were subjected to a 20% or 40% caloric restriction (CR) dietary regime, every other day feeding (IF) or a high fat-high glucose (HFG) diet for six months. The transcriptional activity of the gonadal response to these variations in dietary energy intake was assessed at the individual gene level as well as at the parametric functional level. At the individual gene level, the females showed a higher degree of coherency in gonadal gene alterations to CR than the males. The gonadal transcriptional and hormonal response to IF was also significantly different between the male and female rats. The number of genes significantly regulated by IF in male animals was almost 5 times greater than in the females. These IF males also showed the highest testosterone to estrogen ratio in their plasma. Our data show that at the level of gonadal gene responses, the male rats on the IF regime adapt to their environment in a manner that is expected to increase the probability of eventual fertilization of females that the males predict are likely to be sub-fertile due to their perception of a food deficient environment.

The proregion of mouse BMP15 regulates the cooperative interactions of BMP15 and GDF9

Bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) are secreted by the mammalian oocyte and are essential for ovarian follicular development, ovulation, and fertility. However, the secreted forms of the BMP15 and GDF9 proteins and the nature of cooperative molecular interactions between BMP15 and GDF9 previously reported have not been fully characterized. In this study, we found that recombinant mouse BMP15 and GDF9 are secreted as cleaved mature and proregion proteins, with BMP15 also secreted as uncleaved promature protein. Noncovalent interactions were identified between the mature and proregion proteins of each growth factor. Moreover, GDF9 mature protein was found to coimmunoprecipitate with the BMP15 proregion, suggestive of a heteromeric association between BMP15 and GDF9. Mouse GDF9 was found to exist mostly as a dimer of mature protein, in both the presence and absence of BMP15. In contrast, BMP15 formed mostly multimers of proregion and mature protein when combined with GDF9, providing further evidence for heteromeric interaction. Mouse BMP15 was found to act cooperatively with GDF9 in a rat granulosa cell thymidine incorporation bioassay and to signal through the BMPR2 and ACVR1B/TGFBR1/ACVR1C receptor-mediated pathways. Immunoneutralization experiments using GDF9 mature protein antibody indicated that these cooperative interactions are species specific. Additionally, immunoneutralization with proregion antibodies highlighted the involvement of the BMP15 proregion in BMP15/GDF9 cooperative interactions. Taken together, these findings support a novel hypothesis where the extracellular cooperative interactions of recombinant mouse BMP15 and GDF9 are multimeric, involving the proregion of BMP15, and may well be species specific.