Cystathionine beta synthase participates in murine oocyte maturation mediated by homocysteine

Hydrogen sulfide and its role in female reproduction

Hydrogen sulfide (H2S) is a gaseous signaling molecule produced in the body by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). H2S is crucial in various physiological processes associated with female mammalian reproduction. These include estrus cycle, oocyte maturation, oocyte aging, ovulation, embryo transport and early embryo development, the development of the placenta and fetal membranes, pregnancy, and the initiation of labor. Despite the confirmed presence of H2S-producing enzymes in all female reproductive tissues, as described in this review, the exact mechanisms of H2S action in these tissues remain in most cases unclear. Therefore, this review aims to summarize the knowledge about the presence and effects of H2S in these tissues and outline possible signaling pathways that mediate these effects. Understanding these pathways may lead to the development of new therapeutic strategies in the field of women's health and perinatal medicine.

The functions of hydrogen sulfide on the urogenital system of both males and females: from inception to the present

Hydrogen sulfide (H2S) is known as a chemical gas in nature with both enzymatic and non-enzymatic biosynthesis in different human organs. A couple of studies have demonstrated the function of H2S in regulating the homeostasis of the human body. Additionally, they have shown its synthesis, measurement, chemistry, protective effects, and interaction in various aspects of scientific evidence. Furthermore, many researches have demonstrated the beneficial impacts of H2S on genital organs and systems. According to various studies, it is recognized that H2S-producing enzymes and the endogenous production of H2S are expressed in male and female reproductive systems in different mammalian species. The main goal of this comprehensive review is to assess the potential therapeutic impacts of this gasotransmitter in the male and female urogenital system and find underlying mechanisms of this agent. This narrative review investigated the articles that were published from the 1970s to 2022. The review's primary focus is the impacts of H2S on the male and female urogenital system. Medline, CINAHL, PubMed, and Google scholar databases were searched. Keywords used in this review were "Hydrogen sulfide," "H2S," "urogenital system," and "urogenital tract". Numerous studies have demonstrated the therapeutic and protective effects of sodium hydrosulfide (Na-HS) as an H2S donor on male and female infertility disorders. Furthermore, it has been observed that H2S plays a significant role in improving different diseases such as ameliorating sperm parameters. The specific localization of H2S enzymes in the urogenital system provides an excellent opportunity to comprehend its function and role in various disorders related to this system. It is noteworthy that H2S has been demonstrated to be produced in endocrine organs and exhibit diverse activities. Moreover, it is important to recognize that alterations in H2S biosynthesis are closely linked to endocrine disorders. Therefore, hormones can be pivotal in regulating H2S production, and H2S synthesis pathways may aid in establishing novel therapeutic strategies. H2S possesses pharmacological effects on essential disorders, such as anti-inflammation, anti-apoptosis, and anti-oxidant activities, which render it a valuable therapeutic agent for human urogenital disease. Furthermore, this agent shows promise in ameliorating the detrimental effects of various male and female diseases. Despite the limited clinical research, studies have demonstrated that applying H2S as an anti-oxidant source could ameliorate adverse effects of different conditions in the urogenital system. More clinical studies are required to confirm the role of this component in clinical settings.

Therapeutic Potential of Hydrogen Sulfide in Reproductive System Disorders

Hydrogen sulfide (H2S), previously regarded as a toxic exhaust and atmospheric pollutant, has emerged as the third gaseous signaling molecule following nitric oxide (NO) and carbon monoxide (CO). Recent research has revealed significant biological effects of H2S in a variety of systems, such as the nervous, cardiovascular, and digestive systems. Additionally, H2S has been found to impact reproductive system function and may have therapeutic implications for reproductive disorders. This paper explores the relationship between H2S and male reproductive disorders, specifically erectile dysfunction, prostate cancer, male infertility, and testicular damage. Additionally, it examines the impact of H2S regulation on the pathophysiology of the female reproductive system, including improvements in preterm birth, endometriosis, pre-eclampsia, fetal growth restriction, unexplained recurrent spontaneous abortion, placental oxidative damage, embryo implantation, recovery of myometrium post-delivery, and ovulation. The study delves into the regulatory functions of H2S within the reproductive systems of both genders, including its impact on the NO/cGMP pathway, the activation of K+ channels, and the relaxation mechanism of the spongy smooth muscle through the ROCK pathway, aiming to broaden the scope of potential therapeutic strategies for treating reproductive system disorders in clinical settings.

Regulatory effects of hydrogen sulfide on the female reproductive system

Hydrogen sulfide (H2S), a colorless exhaust gas, has been traditionally considered an air pollutant. However, recent studies have revealed that H2S functions as a novel gas signaling molecule, exerting diverse biological effects on various systems, including the cardiovascular, digestive, and nervous systems. Thus, H2S is involved in various pathophysiological processes. As H2S affects reproductive function, it has potential therapeutic implications in reproductive system diseases. This review examined the role of H2S in various female reproductive organs, including the ovary, fallopian tube, vagina, uterus, and placenta. Additionally, the regulatory function of H2S in the female reproductive system has been discussed to provide useful insights for developing clinical therapeutic strategies for reproductive diseases.

Stage specific gene expression of folate mediated one-carbon metabolism enzymes and transporters in buffalo oocytes and pre-implantation embryos

DNA synthesis and methylations are crucial during pre-implantation embryonic development, and are mediated by one-carbon metabolism of folates. Folates, transported into the cells via folate receptors (FOLR1 and FOLR2) and carriers (SLC19A1), are metabolized by various enzymes involved in folate-methionine cycle. However, the variations in temporal expression of folate transporters and folate-methionine cycle enzymes during pre-implantation embryo development is obscure. Thus, the present study aimed to investigate the differential expression of the genes for folate transporters and folate-methionine cycle enzymes. We also examined the expression of folate transport proteins in different pre-implantation development stages. Immature buffalo oocytes were matured in maturation medium followed by in vitro fertilization and culture at standard culture conditions. The temporal pattern of gene expression in buffalo, when compared to previous studies, indicated an inter-specific variation. The transcripts of some enzymes and folate transporters were significantly upregulated after zygotic genome activation. The transcripts as well as proteins for FOLR1, FOLR2 and SLC19A1 were present in oocytes and all the pre-implantation embryo stages. FOLR1 was present in the nuclei of different stages of developing embryos but not in the metaphase (MII) oocytes. As a result, the present study advocates the existence of active folate transport in buffalo oocytes and pre-implantation embryos. The data provided by the analysis of differential gene expression of folate transporters and metabolic enzymes would likely contribute to a better understanding of the role of folates in embryo development as well as advancements in assisted reproductive technologies.

Unraveling the Puzzle: Oocyte Maturation Abnormalities (OMAS)

Oocyte maturation abnormalities (OMAS) are a poorly understood area of reproductive medicine. Much remains to be understood about how OMAS occur. However, current knowledge has provided some insight into the mechanistic and genetic origins of this syndrome. In this study, current classifications of OMAS syndromes are discussed and areas of inadequacy are highlighted. We explain why empty follicle syndrome, dysmorphic oocytes, some types of premature ovarian insufficiency and resistant ovary syndrome can cause OMAS. We discuss live births in different types of OMAS and when subjects can be offered treatment with autologous oocytes. As such, we present this review of the mechanism and understanding of OMAS to better lead the clinician in understanding this difficult-to-treat diagnosis.

Oocyte maturation abnormalities - A systematic review of the evidence and mechanisms in a rare but difficult to manage fertility pheneomina

A small proportion of infertile women experience repeated oocyte maturation abnormalities (OMAS). OMAS include degenerated and dysmorphic oocytes, empty follicle syndrome, oocyte maturation arrest (OMA), resistant ovary syndrome and maturation defects due to primary ovarian insufficiency. Genetic factors play an important role in OMAS but still need specifications. This review documents the spectrum of OMAS and to evaluate the multiple subtypes classified as OMAS. In this review, readers will be able to understand the oocyte maturation mechanism, gene expression and their regulation that lead to different subtypes of OMAs, and it will discuss the animal and human studies related to OMAS and lastly the treatment options for OMAs. Literature searches using PubMed, MEDLINE, Embase, National Institute for Health and Care Excellence were performed to identify articles written in English focusing on Oocyte Maturation Abnormalities by looking for the following relevant keywords. A search was made with the specified keywords and included books and documents, clinical trials, animal studies, human studies, meta-analysis, randomized controlled trials, reviews, systematic reviews and options written in english. The search detected 3,953 sources published from 1961 to 2021. After title and abstract screening for study type, duplicates and relevancy, 2,914 studies were excluded. The remaining 1,039 records were assessed for eligibility by full-text reading and 886 records were then excluded. Two hundred and twenty seven full-text articles and 0 book chapters from the database were selected for inclusion. Overall, 227 articles, one unpublished and one abstract paper were included in this final review. In this review study, OMAS were classified and extensively evaluatedand possible treatment options under the light of current information, present literature and ongoing studies. Either genetic studies or in vitro maturation studies that will be handled in the future will lead more informations to be reached and may make it possible to obtain pregnancies.

Endogenous hydrogen sulfide promotes human preimplantation embryonic development by regulating metabolism-related gene expression

Hydrogen sulfide (H₂S) as an endogenous gaseous signaling molecule had been proved to play a vital role in gametes physiology, covering meiosis, maturation and aging. However, little is known about H₂S involvement in embryonic development. The present study explored the positive effect of H₂S on human early embryonic development. Results validated that the two H₂S producing enzymes, CBS and CSE mRNA and proteins were identified in donated human cleavage and blastocyst-stage embryos. The l-cysteine incubation produced endogenous H₂S in human blastocysts. NaHS positively affected in vitro blastulation. Single-cell RNA-seq analysis identified 228 differentially expressed genes (DEGs) after NaHS treatment versus the control. The Gene Ontology (GO) enrichment analysis of DEGs showed that genes for protein modification and metabolism were significantly enriched in the NaHS treatment group. For the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, 2-oxocarboxylic acid metabolism, glycosaminoglycan biosynthesis-keratan sulfate, steroid biosynthesis, carbon metabolism, and biosynthesis of amino acids were significantly enriched. Six DEGs, including Neural EGFL like 1 (NELL1), aconitase 1 (ACO1), phosphoglycerate mutase 1 (PGAM1), TP53 induced glycolysis regulatory phosphatase (TIGAR), UDP-GlcNAc:betaGal beta-1,3-N-acetylglucosaminyltransferase 2 (B3GNT2), and carbohydrate Sulfotransferase 4 (CHST4) were validate by real-time RT-PCR. These findings suggest that H₂S is a positive regulator of early embryonic development and may alter the transcription of embryonic genes for protein modification and metabolism in human embryos.

Hydrogen Sulfide Impairs Meiosis Resumption in Xenopus laevis Oocytes

The role of hydrogen sulfide (H₂S) is addressed in Xenopus laevis oocytes. Three enzymes involved in H₂S metabolism, cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase, were detected in prophase I and metaphase II-arrested oocytes and drove an acceleration of oocyte meiosis resumption when inhibited. Moreover, meiosis resumption is associated with a significant decrease in endogenous H₂S. On another hand, a dose-dependent inhibition was obtained using the H₂S donor, NaHS (1 and 5 mM). NaHS impaired translation. NaHS did not induce the dissociation of the components of the M-phase promoting factor (MPF), cyclin B and Cdk1, nor directly impacted the MPF activity. However, the M-phase entry induced by microinjection of metaphase II MPF-containing cytoplasm was diminished, suggesting upstream components of the MPF auto-amplification loop were sensitive to H₂S. Superoxide dismutase and catalase hindered the effects of NaHS, and this sensitivity was partially dependent on the production of reactive oxygen species (ROS). In contrast to other species, no apoptosis was promoted. These results suggest a contribution of H₂S signaling in the timing of amphibian oocytes meiosis resumption.

Anethole improves blastocysts rates together with antioxidant capacity when added during bovine embryo culture rather than in the in vitro maturation medium

We performed the exposure of bovine oocytes to anethole during in vitro maturation (0 or 300 µg/ml), during in vitro embryo production (0, 30, 300 or 2000 µg/ml), or during both periods to determine the rates of 2-4 cells embryos, blastocysts rates and cells numbers, as well as the production of reactive oxygen species (ROS). Bovine ovaries (n = 240) were collected from a local abattoir after slaughter and cumulus-oocyte complexes (COCs) with homogeneous and non-dark cytoplasm, surrounded by two or more compact layers of cumulus cells, and an intact zona pellucida were selected for in vitro maturatuion (IVM). Mature oocytes were then submitted to in vitro fertilization (IVF) and in vitro embryo production (IVP) in culture medium supplemented or not with different concentrations of anethole, as described above. Although IVM medium supplementation with 300 µg/ml anethole improved the rates of bovine blastocysts formation, we demonstrated that IVP medium supplementation with 30 µg/ml anethole, regardless of IVM medium enrichment, considerably enhanced blastocysts rates. Furthermore, ROS levels were decreased only when anethole was added to the IVP medium without previous IVM medium supplementation.

The endogenous hydrogen sulfide generating system regulates ovulation

The generation of free-radicals such as nitric oxide has been implicated in the regulation of ovarian function, including ovulation. Tissues that generate nitric oxide typically generate another free-radical gas, hydrogen sulfide (H₂S), although little is known about the role of H₂S in ovarian function. The hypothesis of this study was that H₂S regulates ovulation. Treatment with luteinizing hormone (LH) increased the levels of mRNA and protein of the H₂S generating enzyme cystathionine γ-lyase (CTH) in granulosa cells of mice and humans in vivo and in vitro. Pharmacological inhibition of H₂S generating enzymes reduced the number of follicles ovulating in mice in vivo and in vitro, and this inhibitory action was reversed by cotreatment with a H₂S donor. Addition of a H₂S donor to cultured mouse granulosa cells increased basal and LH-dependent abundance of mRNA encoding amphiregulin, betacellulin and tumor necrosis alpha induced protein 6, proteins important for cumulus expansion and follicle rupture. Inhibition of CTH activity reduced abundance of mRNA encoding matrix metalloproteinase-2 and -9 and tissue-type plasminogen activator, and cotreatment with the H₂S donor increased the levels of these mRNA above those stimulated by LH alone. We conclude that the H₂S generating system plays an important role in the propagation of the preovulatory cascade and rupture of the follicle at ovulation.

Hydrogen Sulfide Facilitates Vaginal Lubrication by Activation of Epithelial ATP-Sensitive K(+) Channels and Cystic Fibrosis Transmembrane Conductance Regulator

INTRODUCTION

Hydrogen sulfide (H2S) plays a large role in female and male sexual responses characterized by a smooth muscle relaxant effect. Moreover, H2S is a novel pro-secretory neuromodulator that modulates epithelial ion transport. However, whether H2S has a role in regulating vaginal epithelial ion transport and fluid secretion has not been extensively studied.

AIM

To identify the effects of H2S on vaginal epithelial ion transport and lubrication in an exploratory investigation.

METHODS

The mRNA, protein expression, and localization of cystathionine γ-lyase (CSE) and H2S production in vaginal epithelium were examined by reverse transcriptase polymerase chain reaction, Western blot, H2S synthesizing activity assay, and immunohistochemistry, respectively. The effect of H2S on vaginal epithelial ion transport, vaginal fluid secretion, and ionic concentration was investigated using a short-circuit current (ISC), a measurement of vaginal lubrication, and ion chromatography, respectively.

MAIN OUTCOME MEASURES

The mRNA, protein expression, and localization of CSE, H2S formation, changes of ISC responses, vaginal lubrication, and K(+) and Cl(-) concentrations were studied.

RESULTS

CSE mRNA and protein were predominantly expressed in vaginal epithelium. Sodium hydrosulfide hydrate (NaHS) caused concentration-dependent changes in ISC across isolated rat vaginal epithelium, which consisted of an initial decrease phase and then an increase phase. The increase phase in ISC was mainly Cl(-) dependent and abolished by cystic fibrosis transmembrane conductance regulator inhibitor, whereas the decrease phase was sensitive to the adenosine triphosphate-sensitive K(+) (KATP) channel blocker. Furthermore, intravaginal treatment of NaHS significantly enhanced vaginal lubrication in vivo, and this effect was prevented by cystic fibrosis transmembrane conductance regulator and KATP channel inhibitors. In addition, the ionic concentrations of K(+) and Cl(-) in rat vaginal fluid were significantly increased by NaHS treatment.

CONCLUSION

The CSE-H2S pathway participates in the regulation of vaginal epithelial K(+) and Cl(-) ion transport to modulate lumen fluid secretion.

Improvement of gamete quality by stimulating and feeding the endogenous antioxidant system: mechanisms, clinical results, insights on gene-environment interactions and the role of diet

Oxidative damage triggers extensive repair in gametes and thereafter in the zygote but it results in clinically relevant damage when affecting the maturation of the gametes chromatin, i.e. padlocking and epigenetic marking. It associates with defective DNA methylation and/or with oxidation of the methyl marks leading to derangement of gamete epigenetics, defects of chromatin condensation and aneuploidy. A proper feed to the one carbon cycle has the potential to stimulate the endogenous antioxidant defences, i.e. gluthatione synthesis, and to activate compensative homeostatic mechanisms restoring both the oxy-redox balance and DNA methylation, which are indeed strictly cross-regulated. This has been shown to produce measurable clinical improvements of male reproductive potential in pilot studies herein summarised. However, the effects of dietary habits and of supplementations are variable according to the individual genetic substrate, as genetic variants of several of the concerned enzymes occur with high frequency. Individual risk assessments and personalised interventions are still difficult to implement, in the meantime, a very varied diet may facilitate metabolic compensation in the majority of the cases. This review aims to report on the mechanisms of damage, on the opportunities to modulate the physiologic oxy-redox homeostasis by means of a varied diet or dietary supplements and on the open issues related to the genetic variability of the population.

Endogenously produced hydrogen sulfide is involved in porcine oocyte maturation in vitro

Hydrogen sulfide, one of three known gasotransmitters, is involved in physiological processes, including reproductive functions. Oocyte maturation and surrounding cumulus cell expansion play an essential role in female reproduction and subsequent embryonic development. Although the positive effects of exogenous hydrogen sulfide on maturing oocytes are well known, the role of endogenous hydrogen sulfide, which is physiologically released by enzymes, has not yet been described in oocytes. In this study, we observed the presence of Cystathionine β-Synthase (CBS), Cystathionine γ-Lyase (CTH) and 3-Mercaptopyruvate Sulfurtransferase (3-MPST), hydrogen sulfide-releasing enzymes, in porcine oocytes. Endogenous hydrogen sulfide production was detected in immature and matured oocytes as well as its requirement for meiotic maturation. Individual hydrogen sulfide-releasing enzymes seem to be capable of substituting for each other in hydrogen sulfide production. However, meiosis suppression by inhibition of all hydrogen sulfide-releasing enzymes is not irreversible and this effect is a result of M-Phase/Maturation Promoting Factor (MPF) and Mitogen-Activated Protein Kinase (MAPK) activity inhibition. Futhermore, cumulus expansion expressed by hyaluronic acid (HA) production is affected by the inhibition of hydrogen sulfide production. Moreover, quality changes of the expanded cumuli are indicated. These results demonstrate hydrogen sulfide involvement in oocyte maturation as well as cumulus expansion. As such, hydrogen sulfide appears to be an important cell messenger during mammalian oocyte meiosis and adequate cumulus expansion.

Hydrogen sulfide donor protects porcine oocytes against aging and improves the developmental potential of aged porcine oocytes

Porcine oocytes that have matured in in vitro conditions undergo the process of aging during prolonged cultivation, which is manifested by spontaneous parthenogenetic activation, lysis or fragmentation of aged oocytes. This study focused on the role of hydrogen sulfide (H₂S) in the process of porcine oocyte aging. H₂S is a gaseous signaling molecule and is produced endogenously by the enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (MPST). We demonstrated that H₂S-producing enzymes are active in porcine oocytes and that a statistically significant decline in endogenous H₂S production occurs during the first day of aging. Inhibition of these enzymes accelerates signs of aging in oocytes and significantly increases the ratio of fragmented oocytes. The presence of exogenous H₂S from a donor (Na₂S.9H₂O) significantly suppressed the manifestations of aging, reversed the effects of inhibitors and resulted in the complete suppression of oocyte fragmentation. Cultivation of aging oocytes in the presence of H₂S donor positively affected their subsequent embryonic development following parthenogenetic activation. Although no unambiguous effects of exogenous H₂S on MPF and MAPK activities were detected and the intracellular mechanism underlying H₂S activity remains unclear, our study clearly demonstrates the role of H₂S in the regulation of porcine oocyte aging.

Dual effects of hydrogen sulfide donor on meiosis and cumulus expansion of porcine cumulus-oocyte complexes

Hydrogen sulfide (H₂S) has been revealed to be a signal molecule with second messenger action in the somatic cells of many tissues, including the reproductive tract. The aim of this study was to address how exogenous H₂S acts on the meiotic maturation of porcine oocytes, including key maturation factors such as MPF and MAPK, and cumulus expansion intensity of cumulus-oocyte complexes. We observed that the H₂S donor, Na₂S, accelerated oocyte in vitro maturation in a dose-dependent manner, following an increase of MPF activity around germinal vesicle breakdown. Concurrently, the H₂S donor affected cumulus expansion, monitored by hyaluronic acid production. Our results suggest that the H₂S donor influences oocyte maturation and thus also participates in the regulation of cumulus expansion. The exogenous H₂S donor apparently affects key signal pathways of oocyte maturation and cumulus expansion, resulting in faster oocyte maturation with little need of cumulus expansion.

C. elegans aging is modulated by hydrogen sulfide and the sulfhydrylase/cysteine synthase cysl-2

Exogenous hydrogen sulfide (H2S) administration and endogenous H2S metabolism were explored in the nematode C. elegans. Chronic treatment with a slow-releasing H2S donor, GYY4137, extended median survival by 17-23% and increased tolerance towards oxidative and endoplasmic reticulum (ER) stress. Also, cysl-2, a sulfhydrylase/cysteine synthase in C. elegans, was transcriptionally upregulated by GYY4137 treatment and the deletion of cysl-2 resulted in a significant reduction in lifespan which was partially recovered by the supplementation of GYY4137. Likewise, a mammalian cell culture system, GYY4137 was able to protect bovine aortic endothelial cells (BAECs) from oxidative stress and (H2O2)-induced cell death. Taken together, this provides further support that H2S exerts a protective function which is consistent with the longevity dividend theory. Overall, this study underlines the therapeutic potential of a slow-releasing H2S donor as regulators of the aging and cellular stress pathways.

Endogenous folates and single-carbon metabolism in the ovarian follicle, oocyte and pre-implantation embryo

Maternal B-vitamin status at conception can affect fertility and the health of offspring. This study details transcript expression for genes encoding key enzymes in the linked methionine/folate cycles in the bovine oocyte, somatic cells of the ovarian follicle and pre-implantation embryo. Transcripts for all 12 enzymes that were studied and for the two folate receptors (FOLR1 and FOLR2) and reduced folate carrier (SLC19A1) were expressed in liver cells, but transcripts for betaine-homocysteine methyltransferase and methionine adenosyl transferase 1A were absent in all ovarian cells, and transcripts for FOLR2 were absent in embryonic cells. Transcripts for glycine methyltransferase were also absent/weak in cumulus and granulosa cells. The absence of these enzymes could have a profound effect on single-carbon metabolism within the ovary and pre-implantation embryo. Immunocytochemical analysis revealed SLC19A1 protein expression on the plasma and basal-lateral membranes of the pre-implantation embryo. The folate antagonist methotrexate (MTX) enters the cell via SLC19A1, and in the current study, MTX inclusion in bovine/ovine culture media at either 1 or 10 microM from the 1-cell stage inhibited embryo development beyond the 8-cell stage. Hypoxanthine and thymidine (100 microM) increased the proportion of embryos that developed to blastocysts, but the cell number was reduced by 20%. The reduced uptake of [(35)S] methionine into intra-cellular S-adenosylmethionine and S-adenosylhomocysteine pools, together with reduced uptake of glutamate and tryptophan, was consistent with depleted intra-cellular pools of reduced folates. These data provide an insight into the importance of maternal dietary folate/B-vitamin status during the peri-conceptional period.

B-vitamin and homocysteine status determines ovarian response to gonadotropin treatment in sheep

Maternal B-vitamin status and homocysteinemia can affect fertility and pregnancy establishment, although the direct effects on ovarian follicle and oocyte development are not known. We report on the effects of restricting the supply of vitamin B(12) and methionine from the diet of mature female sheep on ovarian folliculogenesis following follicle-stimulating hormone (FSH) stimulation. The study was split into three batches and involved 76 animals. Surprisingly, the number of growing, estrogen-active antral follicles following FSH treatment was enhanced (P = 0.005) following this dietary intervention. This increase occurred even in the presence of modest live-weight loss (batch 1 only) and depressed plasma insulin concentrations, suggesting a breakdown in the regulation of follicular responsiveness to FSH. This dietary intervention also increased plasma homocysteine concentrations. Physiological concentrations of homocysteine increased granulosa cell proliferation (P < 0.001), estradiol production (P = 0.05), and FSHR transcript expression (P = 0.017) during culture. Transcript levels for growth differentiation factor 9 and bone morphogenetic protein 15 in oocytes from treated ewes were increased (P < 0.05) in the first two batches. Furthermore, regression of BMP receptor 2 (BMPR2) transcript expression and diet on follicle number revealed a significant interaction (P = 0.01); BMPR2 transcript expression was associated with follicle number only in vitamin B(12)/methionine-restricted animals. Because FSHR transcript expression also was positively (P = 0.007) related to follicle number, the effects of diet may have arisen through enhanced FSH and BMP signaling. Although this remains to be confirmed, the data support an intraovarian impact of vitamin B(12)/methionine-deficient diets.