Nerve growth factor production in sheep antral follicles

Seasonal expressions of nerve growth factor (NGF), and its receptor TrkA and p75 in the scent glands of muskrats (Ondatra zibethicus)

NGF, also known as nerve growth factor, is crucial for the survival and differentiation of the nervous system, in addition to being involved in a number of non-neuronal systems. The aim of this work was to investigate the immunolocalization and expression patterns of NGF, its receptor, tyrosine kinase receptor A (TrkA), and p75 in the scent glands of muskrats (Ondatra zibethicus) throughout the breeding and non-breeding seasons. The scent gland mass showed considerable seasonal variations, with higher values during the breeding season and comparatively lower levels during the non-breeding season. While no immunostaining was observed in the interstitial cells, NGF, TrkA, and p75 were immunolocalized in the scent glandular cells and epithelial cells during both breeding and non-breeding seasons. NGF, TrkA, and p75 protein and mRNA expression levels were higher in the scent glands during breeding season compared to the non-breeding season. Circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), and T in the scent gland were all significantly higher throughout the breeding season. The relative levels of the hormones in the plasma and the scent glands as well as NGF, TrkA, and p75 were positively associated with each other. Additionally, transcriptome analysis of the scent glands revealed that differentially expressed genes may be linked to steroid biosynthesis, the estrogen signaling pathway, and neurotransmitter transmembrane transporter function. These results suggest a potential role for NGF, TrkA, and p75 in controlling seasonal variations in the muskrats' scent gland functioning.

Effects of Nerve Growth Factor-β From Bull Seminal Plasma on Steroidogenesis and Angiogenic Markers of the Bovine Pre-ovulatory Follicle Wall Cell Culture

Nerve growth factor-β (NGF) is critical for ovulation in the mammalian ovary and is luteotrophic when administered systemically to camelids and cattle. This study aimed to assess the direct effects of purified bovine NGF on steroidogenesis and angiogenic markers in the bovine pre-ovulatory follicle. Holstein heifers (n = 2) were synchronized with a standard protocol, and heifers with a preovulatory follicle (≥ 12 mm) had the ovary containing the dominant follicle removed via colpotomy. Pre-ovulatory follicles were dissected into 24 pieces containing theca and granulosa cells that were randomly allocated into culture media supplemented with either purified bovine NGF (100 ng/mL) or untreated (control) for 72 h. The supernatant media was harvested for quantification of progesterone, testosterone, and estradiol concentrations, whereas explants were subjected to mRNA analyses to assess expression of steroidogenic and angiogenic markers. Treatment of follicle wall pieces with NGF upregulated gene expression of steroidogenic enzyme HDS17B (P = 0.04) and increased testosterone production (P < 0.01). However, NGF treatment did not alter production of progesterone (P = 0.81) or estradiol (P = 0.14). Consistently, gene expression of steroidogenic enzymes responsible for producing these hormones (STAR, CYP11A1, HSD3B, CYP17A1, CYP19A1) were unaffected by NGF treatment (P ≥ 0.31). Treatment with NGF downregulated gene expression of the angiogenic enzyme FGF2 (P = 0.02) but did not alter PGES (P = 0.63), VEGFA (P = 0.44), and ESR1 (P = 0.77). Collectively, these results demonstrate that NGF from seminal plasma may interact directly on the theca and granulosa cells of the bovine pre-ovulatory follicle to stimulate testosterone production, which may be secondary to theca cell proliferation. Additionally, decreased FGF2 expression in NGF-treated follicle wall cells suggests hastened onset of follicle wall cellular remodeling that occurs during early luteal development.

Seasonal Expression of NGF and Its Cognate Receptors in the Ovaries of Grey Squirrels (Sciurus carolinensis)

Simple Summary

Invasive alien species pose a significant threat to biodiversity, as once they have adapted to their new environment, they cause the reduction and even extinction of native species. In this framework, the American grey squirrel (Sciurus carolinensis) poses a serious threat to the European red species squirrel (Sciurus vulgaris), especially in the Umbria region of Italy. In fact, an invasive grey squirrel population has adapted well to the Umbrian territory, showing high reproductive success. In addition to its role in the development of the vertebrate nervous system, nerve growth factor (NGF) has recently been found to play an important role in reproduction. In order to investigate the reproductive physiology of female grey squirrels, the ovarian presence, distribution, and gene expression of NGF and its cognate receptors were evaluated during both breeding and nonbreeding seasons. The presence and gene expression of this system at the ovarian level, mainly during the breeding season, confirm the possible involvement of NGF and its receptors in the gonadal activity of this invasive grey squirrel population.

Abstract

The grey squirrel is an invasive alien species that seriously threatens the conservation of the native red squirrel species. With the aim of characterizing the reproductive physiology of this species due to its great reproductive success, the function of the ovarian nerve growth factor (NGF) system was analyzed in a grey squirrel population living in central Italy. During the breeding and nonbreeding seasons, the ovarian presence, distribution, and gene expression of NGF, neurotrophic tyrosine kinase receptor 1 (NTRK1), and nerve growth factor receptor (NGFR), as well as NGF plasma concentrations, were evaluated in female grey squirrels. NGF was found in the luteal cells and in the thecal and granulosa cells of follicles, while NTRK1 and NGFR were only observed in follicular thecal and granulosa cells. NGF and NGFR transcripts were almost two-fold greater during the breeding season, while no seasonal differences were observed in NTRK1 gene expression. During the breeding season, NGFR was more expressed than NTRK1. Moreover, no changes were observed in NGF plasma levels during the reproductive cycle. The NGF system seems to be involved in regulating the ovarian cycle mainly via local modulation of NGF/NGFR, thus playing a role in the reproductive physiology of this grey squirrel population.

Role of nerve growth factor in the reproductive physiology of female rabbits: A review

Rabbit does are reflex ovulators such that coitus is needed to release GnRH and elicit the LH surge that triggers the ovulation of mature oocytes. However, the mechanisms eliciting ovulation in this species remain unclear. One of the most promising recently discovered candidates with a role in female reproductive physiology is nerve growth factor beta (β-NGF). This neurotrophin and its high-affinity receptor TrkA and low affinity receptor p75, is present in all compartments of the ovary, oviduct and uterus suggesting a physiologic role in ovarian folliculogenesis, steroidogenesis, ovulation, luteogenesis and embryo development. Besides, evidence exists that β-NGF found in seminal plasma could exert a modulatory role in the female hypothalamus-pituitary-ovarian axis contributing to the adrenergic and cholinergic neuronal stimulus of GnRH neurons in an endocrine manner during natural mating. Probably, the paracrine and local roles of the neurotrophin in steroidogenesis and ovulation reinforce the neuroendocrine pathway that leads to ovulation. This review updates knowledge of the role of β-NGF in rabbit reproduction, including its possible contribution to the mechanisms of action that induce ovulation, and discusses perspectives for the future applications of this neurotrophin on rabbit farms.

The effect of seminal plasma β-NGF on follicular fluid hormone concentration and gene expression of steroidogenic enzymes in llama granulosa cells

BACKGROUND

Nerve growth factor (β-NGF) from llama seminal plasma has been described as a potent ovulatory and luteotrophic molecule after intramuscular or intrauterine infusion in llamas and alpacas. We tested the hypothesis that systemic administration of purified β-Nerve Growth Factor (β-NGF) during the preovulatory stage will up-regulate steroidogenic enzymes and Vascular Endothelial Growth Factor (VEGF) gene expression in granulosa cells inducing a change in the progesterone/estradiol ratio in the follicular fluid in llamas.

METHODS

Experiment I: Female llamas (n = 64) were randomly assigned to receive an intramuscular administration of: a) 50 μg gonadorelin acetate (GnRH, Ovalyse, Pfizer Chile SA, Santiago, Chile, n = 16), b) 1.0 mg of purified llama β-NGF (n = 16), or c) 1 ml phosphate buffered saline (PBS, negative control group, n = 16). An additional group of llamas (n = 16) were mated with a fertile male. Follicular fluid and granulosa cells were collected from the preovulatory follicle at 10 or 20 h after treatment (Time 0 = administration of treatment, n = 8/treatment/time point) to determine progesterone/estradiol concentration and steroidogenic enzymes and VEGF gene expression at both time points. Experiment II: Granulosa cells were collected from preovulatory follicles from llamas (n = 24) using ultrasound-guided transvaginal follicle aspiration for in vitro culture to determine mRNA relative expression of Steroidogenic Acute Regulatory Protein (StAR) and VEGF at 10 or 20 h (n = 4 replicates) and progesterone secretion at 48 h (n = 4 replicates) after LH or β-NGF treatment.

RESULTS

Experiment I: There was a significant increase in the progesterone/estradiol ratio in mated llamas or treated with GnRH or purified β-NGF. There was a significant downregulation in the mRNA expression of Aromatase (CYP19A1/P450 Arom) for both time points in llamas mated or treated with GnRH or llama purified β-NGF with respect to the control group. All treatments except β-NGF (20 h) significantly up regulated the mRNA expression of 3-beta-hydroxysteroid dehydrogenase (HSD3B) whereas the expression of StAR and Side-Chain cleavage enzyme (CYP11A1/P450scc) where significantly up regulated only by mating (20 h), or β-NGF at 10 or 20 h after treatment. VEGF was up regulated only in those llamas submitted to mating (10 h) or treated with purified β-NGF (10 and 20 h). Experiment II: Only β-NGF treatment induced an increase of mRNA abundance of StAR from llama granulosa cells at 20 h of in vitro culture. There was a significant increase on mRNA abundance of VEGF at 10 and 20 h of in vitro culture from granulosa cells treated with β-NGF whereas LH treatment increases VEGF mRNA abundance only at 20 h of in vitro culture. In addition, there was a significant increase on progesterone secretion from llama granulosa cells 48 h after LH or β-NGF treatment.

CONCLUSIONS

Systemic administration of purified β-NGF from llama seminal fluid induced a rapid shift from estradiol to progesterone production in the preovulatory follicle. Differences in gene expression patterns of steroidogenic enzymes between GnRH and mated or β-NGF-treated llamas suggest local effects of seminal components on the preovulatory follicle.

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.

Supplementation with CTGF, SDF1, NGF, and HGF promotes ovine in vitro oocyte maturation and early embryo development

The strategies for improving the in vitro maturation (IVM) of domestic animal oocytes focus on promoting nuclear and cytoplasmic maturation. The identification of paracrine factors and their supplementation in the culture medium represent effective approaches for oocyte maturation and embryo development. This study investigated the effects of paracrine factor supplementation including connective tissue growth factor (CTGF), nerve growth factor (NGF), hepatocyte growth factor (HGF), and stromal derived factor 1 (SDF1) on ovine oocytes and early parthenogenetic embryos using an in vitro culture system. First, we identified the optimal concentrations of CTGF (30 ng/mL), SDF1 (10 ng/mL), NGF (3 ng/mL), and HGF (100 ng/mL) for promoting oocyte maturation, which combined, induced nuclear maturation in 94.19% of oocytes. This combination also promoted cumulus cell expansion and inhibited oocyte/cumulus apoptosis, while enabling a larger proportion (33.04%) of embryos to develop into blastocysts than in the controls and prevented embryo apoptosis. These novel findings demonstrate that the paracrine factors CTGF, SDF1, NGF, and HGF facilitate ovine oocyte and early parthenogenetic embryo development in vitro. Thus, supplementation with these factors may help optimize the IVM of ovine oocytes and early parthenogenetic embryo development strategies.

Neurotrophins and Trk receptors in the developing and adult ovary of Coturnix coturnix japonica

NGF, BDNF, NT-3 and their specific receptors TrkA, TrkB and TrkC are known to be involved in the development and maintenance of vertebrates' nervous system. However, these molecules play a role also in non-neuronal tissue, such as in the reproductive system. In this study we investigated the presence and localization of neurotrophins and Trk receptors to unravel their potential role in the developing and adult ovary of Japanese quail, a model species well suited for reproduction studies. Western blotting analysis on ovaries of three month old quails in the period of egg laying showed the presence of pro and mature forms of neurotrophins and splice variants of Trk receptors. Immunohistochemical investigation reported that in embryonic ovaries from the 9th day of incubation to the hatching NGF and NT-3 were observed in the cortical and medullar areas respectively, whereas Trk receptors were observed in both areas. In adult ovary, all NTs were detected in glandular stromal cells, NGF and NT-3 also in the nervous component. Regarding follicle components, NGF and BDNF were observed in oocytes and follicular cells. All TrK receptors were present in nervous components and only TrkA in glandular stromal cells. In follicles, TrkA was present in oocyte cytoplasm and TrkB in theca cells. The results suggest an involvement of the neurotrophin system in the quail ovary physiology, promoting the oocyte development and follicular organization in the embryo, as well as oocyte and follicular maturation in adults.

Nerve growth factor from seminal plasma origin (spβ-NGF) increases CL vascularization and level of mRNA expression of steroidogenic enzymes during the early stage of Corpus Luteum development in llamas

The objectives of the study were to determine the effect of seminal plasma β-NGF on Corpus Luteum morphology and function and level of mRNA expression of steroidogenic enzymes. Llamas were assigned (n = 12/per group) to receive an intramuscular dose of: (a) 1 ml phosphate buffered saline (PBS), (b) 5 μg gonadorelin acetate (GnRH), or (c) 1.0 mg of purified llama spβ-NGF. Ovaries were examined by transrectal B-mode ultrasonography from treatment to ovulation (Day 0 = treatment). B mode/Power Doppler ultrasonography and blood samples collection were performed at Days 4, 8 and 10 (n = 3 llamas per treatment group/per time point) to determine CL diameter, vascularization and plasma progesterone concentration respectively. Plasma progesterone concentration was analyzed in all llamas at Day 0. Then females were submitted to ovariectomy at Days 4, 8 and 10 (n = 3 llamas/treatment/time), CL was removed to determine vascular area, proportion of luteal cells and CYP11A1/P450scc and STAR expression by RT-PCR. Ovulation was similar between llamas treated with GnRH or spβ-NGF and CL diameter did not differ between GnRH or spβ-NGF groups by Day 4, 8 or 10. Vascularization area of the CL was higher (P < 0.01) in llamas from the spβ-NGF than GnRH-treated group by Day 4 and 8. Plasma progesterone concentration was higher (P < 0.05) in llamas from the spβ-NGF compared to females of GnRH group by Day 4 and 8. The proportion of small and large luteal cells did not differ between GnRH or spβ-NGF groups by Day 8. CYP11A1/P450scc was upregulated 3 folds at day 4 and 10 by spβ-NGF compared to GnRH. STAR transcription was 3 folds higher at day 4 in females treated with spβ-NGF. In conclusion, the luteotrophic effect of spβ-NGF could be related to an increase of vascularization and up regulation of CYP11A1/P450scc and STAR transcripts enhancing progesterone secretion.

The dynamics of trkA expression in the bovine ovary are associated with a luteotrophic effect of ovulation-inducing factor/nerve growth factor (OIF/NGF)

BACKGROUND

Ovulation-inducing factor in semen (OIF/NGF) influences ovulation and CL form and function in camelids and, remarkably, in cows. To test the hypothesis that the luteotrophic effect of OIF/NGF is mediated by an increase in trkA receptors in the ovulatory follicle and early CL, a study was designed to characterize the spatial and temporal distribution of trkA in ovarian follicles and CL at known stages of the bovine estrous cycle.

METHODS

Sexually mature cattle (n = 14) were examined daily by transrectal ultrasonography to determine the day of ovulation (Day 0), and assigned randomly to be unilaterally ovariectomized on Day 2, 4, 6 or in the pre-ovulatory period just before or after exogenous LH treatment. After a complete interovulatory interval, the cows were re-assigned to a different day-group on which the remaining ovary was removed. Sections of ovarian tissue representing the dominant follicle, largest subordinate follicle, and the CL were processed for immunofluorescent detection and quantification of trkA receptor.

RESULTS

TrkA immuno-fluorescence in ovarian tissues was restricted to follicles and the CL (no reaction in stroma or vessels), and was restricted to the cytoplasm (no nuclear staining). The trkA staining intensity, area of staining, and proportion of cells stained was greater in both theca and granulosa layers of dominant follicles than in that of subordinate follicles (P ≤ 0.05) in all day-groups except the Pre-LH group. Among dominant follicles, a progressive reduction in the immuno-positive reaction was detected from Day 2 to Day 6. Among subordinate follicles, immuno-reactivity remained low and unchanged except a rise in the Pre-LH group. The number of immuno-positive cells was greater in early developing CL (Days 2 and 4 combined) than in mature or regressing stage CL (Day 6, Pre- and Post-LH combined; P = 0.01). The intracellular distribution of trkA was more diffuse and widespread in dominant than subordinate follicles, particularly on Day 2 and Post-LH (P < 0.05).

CONCLUSIONS

Distinct differences in trkA expression between dominant and subordinate follicles, particularly when circulating progesterone is minimal (early luteal development and after luteolysis) is consistent with a local role of OIF/NGF in follicle selection and early luteogenesis.

Testicular expression of NGF, TrkA and p75 during seasonal spermatogenesis of the wild ground squirrel (Citellus dauricus Brandt)

The nerve growth factor (NGF) not only has an essential effect on the nervous system, but also plays an important role in a variety of non-neuronal systems, such as the reproductive system. The aim of this study was to compare the quality and quantity in expression of NGF and its receptors (TrkA and p75) in testes of the wild ground squirrel during the breeding and nonbreeding seasons. Immunolocalization for NGF was detected mainly in Leydig cells and Sertoli cells in testes of the breeding and nonbreeding seasons. The immunoreactivity of TrkA was highest in the elongated spermatids, whereas p75 in spermatogonia and spermatocytes in testes of the breeding season. In the nonbreeding season testes, TrkA showed positive immunostainings in Leydig cells, spermatogonia and primary spermatocytes, while p75 showed positive signals in spermatogonia and primary spermatocytes. Consistent with the immunohistochemical results, the mean mRNA and protein level of NGF and TrkA were higher in the testes of the breeding season than in non-breeding season, and then decreased to a relatively low level in the nonbreeding season. In addition, the concentration of plasma gonadotropins and testosterone were assayed by radioimmunoassay (RIA), and the results showed a significant difference between the breeding and nonbreeding seasons with higher concentrations in breeding season. In conclusion, these results of this study provide the first evidence on the potential involvement of NGF and its receptor, TrkA and p75 in the seasonal spermatogenesis and testicular function change of the wild ground squirrel.

Cellular and molecular maturation in fetal and adult ovine calcaneal tendons

Processes of development during fetal life profoundly transform tendons from a plastic tissue into a highly differentiated structure, characterised by a very low ability to regenerate after injury in adulthood. Sheep tendon is frequently used as a translational model to investigate cell-based regenerative approaches. However, in contrast to other species, analytical and comparative baseline studies on the normal developmental maturation of sheep tendons from fetal through to adult life are not currently available. Thus, a detailed morphological and biochemical study was designed to characterise tissue maturation during mid- (2 months of pregnancy: 14 cm of length) and late fetal (4 months: 40 cm of length) life, through to adulthood. The results confirm that ovine tendon morphology undergoes profound transformations during this period. Endotenon was more developed in fetal tendons than in adult tissues, and its cell phenotype changed through tendon maturation. Indeed, groups of large rounded cells laying on smaller and more compacted ones expressing osteocalcin, vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) were identified exclusively in fetal mid-stage tissues, and not in late fetal or adult tendons. VEGF, NGF as well as blood vessels and nerve fibers showed decreased expression during tendon development. Moreover, the endotenon of mid- and late fetuses contained identifiable cells that expressed several pluripotent stem cell markers [Telomerase Reverse Transcriptase (TERT), SRY Determining Region Y Box-2 (SOX2), Nanog Homeobox (NANOG) and Octamer Binding Transcription Factor-4A (OCT-4A)]. These cells were not identifiable in adult specimens. Ovine tendon development was also accompanied by morphological modifications to cell nuclei, and a progressive decrease in cellularity, proliferation index and expression of connexins 43 and 32. Tendon maturation was similarly characterised by modulation of several other gene expression profiles, including Collagen type I, Collagen type III, Scleraxis B, Tenomodulin, Trombospondin 4 and Osteocalcin. These gene profiles underwent a dramatic reduction in adult tissues. Transforming growth factor-1 expression (involved in collagen synthesis) underwent a similar decrease. In conclusion, these morphological studies carried out on sheep tendons at different stages of development and aging offer normal structural and molecular baseline data to allow accurate evaluation of data from subsequent interventional studies investigating tendon healing and regeneration in ovine experimental models.

Seasonal changes in expression of nerve growth factor and its receptors TrkA and p75 in the ovary of wild ground squirrel (Citellus dauricus Brandt)

The aim of this study was to investigate the presence of nerve growth factor (NGF) and its receptors tyrosine kinase A (TrkA) and p75 in the ovaries of the wild ground squirrels during the breeding and nonbreeding seasons. In the breeding period, NGF, TrkA and p75 were immunolocalized in granulosa cells, thecal cells, interstitial cells and luteal cells whereas in the nonbreeding period, both of them were detected only in granulosa cells, thecal cells and interstitial cells. Stronger immunostaining of NGF, TrkA and p75 were observed in granulosa cells, thecal cells and interstitial cells in the breeding season compared to the nonbreeding season. Corresponding for the immunohistochemical results, immunoreactivities of NGF and its two receptors were greater in the ovaries of the breeding season then decreased to a relatively low level in the nonbreeding season. The mean mRNA levels of NGF, TrkA and p75 were significantly higher in the breeding season than in the nonbreeding season. In addition, plasma gonadotropins, estradiol-17β and progesterone concentrations were significantly higher in the breeding season than in the nonbreeding season, suggesting that the expression patterns of NGF, and TrkA and p75 were correlated with changes in plasma gonadotropins, estradiol-17β and progesterone concentrations. These results indicated that NGF and its receptors, TrkA and p75 may be involved in the regulation of seasonal changes in the ovarian functions of the wild ground squirrel.

Gene expression profiling reveals new potential players of gonad differentiation in the chicken embryo

BACKGROUND

In birds as in mammals, a genetic switch determines whether the undifferentiated gonad develops into an ovary or a testis. However, understanding of the molecular pathway(s) involved in gonad differentiation is still incomplete.

METHODOLOGY/PRINCIPAL FINDINGS

With the aim of improving characterization of the molecular pathway(s) involved in gonad differentiation in the chicken embryo, we developed a large scale real time reverse transcription polymerase chain reaction approach on 110 selected genes for evaluation of their expression profiles during chicken gonad differentiation between days 5.5 and 19 of incubation. Hierarchical clustering analysis of the resulting datasets discriminated gene clusters expressed preferentially in the ovary or the testis, and/or at early or later periods of embryonic gonad development. Fitting a linear model and testing the comparisons of interest allowed the identification of new potential actors of gonad differentiation, such as Z-linked ADAMTS12, LOC427192 (corresponding to NIM1 protein) and CFC1, that are upregulated in the developing testis, and BMP3 and Z-linked ADAMTSL1, that are preferentially expressed in the developing ovary. Interestingly, the expression patterns of several members of the transforming growth factor β family were sexually dimorphic, with inhibin subunits upregulated in the testis, and bone morphogenetic protein subfamily members including BMP2, BMP3, BMP4 and BMP7, upregulated in the ovary. This study also highlighted several genes displaying asymmetric expression profiles such as GREM1 and BMP3 that are potentially involved in different aspects of gonad left-right asymmetry.

CONCLUSION/SIGNIFICANCE

This study supports the overall conservation of vertebrate sex differentiation pathways but also reveals some particular feature of gene expression patterns during gonad development in the chicken. In particular, our study revealed new candidate genes which may be potential actors of chicken gonad differentiation and provides evidence of the preferential expression of BMPs in the developing ovary and Inhibin/Activin subunits in the developing testis.

Expression of nerve growth factor and its receptors, TrkA and p75, in porcine ovaries

The cellular localization of nerve growth factor (NGF) and its receptors (TrkA, p75) was investigated during the estrous cycle in gilts. Also, the levels of expression of these factors in walls of tertiary follicles and corpora lutea (CLs) were determined using Western blot. The ovaries from days 3, 7, 16 and 20 of the cycle revealed the presence of NGF and its receptors in oocytes of secondary and tertiary follicles, follicular cells of primary and secondary follicles, thecal and granulosa cells of tertiary follicles and steroidogenic cells of CLs. In wall cells of primary follicles, NGF, TrkA and p75 staining was strongest on day 16, while in secondary follicles, only p75 was more intensely stained on day 16 and 20. In walls of small (to 3 mm in diameter) and medium (4-6 mm in diameter) follicles, NGF staining was lower on day 16, and the p75 reaction was strongest on day 20. On day 20, NGF staining in large follicles (7-10 mm in diameter) was higher than in smaller follicles. The levels of NGF and p75 in small and medium follicles were highest on day 20. The contents of NGF and TrkA in large follicles on day 20 were higher than in smaller follicles. NGF and TrkA contents in CLs were highest on day 7. Our study demonstrates that NGF, TrkA and p75 are expressed in the ovary during the estrous cycle in gilts. These results suggest that NGF and its receptors may be important for ovarian function in cycling gilts.

Excessive ovarian production of nerve growth factor facilitates development of cystic ovarian morphology in mice and is a feature of polycystic ovarian syndrome in humans

Although ovarian nerve growth factor (NGF) facilitates follicular development and ovulation, an excess of the neurotrophin in the rodent ovary reduces ovulatory capacity and causes development of precystic follicles. Here we show that ovarian NGF production is enhanced in patients with polycystic ovarian syndrome (PCOS) and that transgenically driven overproduction of NGF targeted to the ovary results in cystic morphology, when accompanied by elevated LH levels. NGF levels are increased in the follicular fluid from PCOS ovaries and in the culture medium of granulosa cells from PCOS patients, as compared with non-PCOS patients. Ovaries from transgenic mice carrying the NGF gene targeted to thecal-interstitial cells by the 17alpha-hydroxylase gene promoter produce more NGF than wild-type (WT) ovaries and are hyperinnervated by sympathetic nerves. Antral follicle growth is arrested resulting in accumulation of intermediate size follicles, many of which are apoptotic. Peripubertal transgenic mice respond to a gonadotropin challenge with a greater increase in plasma 17-hydroxyprogesterone, estradiol, and testosterone levels than WT controls. Transgenic mice also exhibit a reduced ovulatory response, delayed puberty, and reduced fertility, as assessed by a prolonged interval between litters, and a reduced number of pups per litter. Sustained, but mild, elevation of plasma LH levels results in a heightened incidence of ovarian follicular cysts in transgenic mice as compared with WT controls. These results suggest that overproduction of ovarian NGF is a component of polycystic ovarian morphology in both humans and rodents and that a persistent elevation in plasma LH levels is required for the morphological abnormalities to appear.

Expression of nerve growth factor and its receptors trkA and p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters

Characteristic daily increases in the plasma levels of luteinizing hormone (LH) are present every afternoon during lactation in golden hamsters. The objective of this study was to investigate the effect of the diurnal rhythm of increases in LH on expression of nerve growth factor (NGF), its receptors trkA and p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters. Both lactating and non-lactating groups of postpartum golden hamsters were used in this study. The expression of NGF, its receptors trkA and p75 and inhibin alpha-subunit were determined by immunohistochemistry. Positive staining of NGF, trkA and p75 was found in the interstitial cells of the lactating group, and no immunoreactivity for NGF, trkA or p75 was observed in the ovarian interstitial cells of the non-lactating group. In addition, immunostaining of inhibin alpha-subunit was also observed in the interstitial cells of the lactating group but not in those of the non-lactating group. Immunostaining of the inhibin/activin beta(A)- and beta(B)-subunits was observed in the granulosa cells of antral follicles, but not in the interstitial cells of the lactating and non-lactating animals. These results suggest that the diurnal rhythm increases in LH can induce expression of NGF, trkA, p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters and that NGF, its receptors trkA and p75 and inhibin alpha-subunit may have the capacity for autocrine or paracrine modulation of interstitial cell differentiation in golden hamsters.

Effects of nerve growth factor (NGF) on blood vessels area and expression of the angiogenic factors VEGF and TGFbeta1 in the rat ovary

BACKGROUND

Angiogenesis is a crucial process in follicular development and luteogenesis. The nerve growth factor (NGF) promotes angiogenesis in various tissues. An impaired production of this neurotrophin has been associated with delayed wound healing. A variety of ovarian functions are regulated by NGF, but its effects on ovarian angiogenesis remain unknown. The aim of this study was to elucidate if NGF modulates 1) the amount of follicular blood vessels and 2) ovarian expression of two angiogenic factors: vascular endothelial growth factor (VEGF) and transforming growth factor beta 1 (TGFbeta1), in the rat ovary.

RESULTS

In cultured neonatal rat ovaries, NGF increased VEGF mRNA and protein levels, whereas TGFbeta1 expression did not change. Sectioning of the superior ovarian nerve, which increases ovarian NGF protein content, augmented VEGF immunoreactivity and the area of capillary vessels in ovaries of prepubertal rats compared to control ovaries.

CONCLUSION

Results indicate that NGF may be important in the maintenance of the follicular and luteal vasculature in adult rodents, either indirectly, by increasing the expression of VEGF in the ovary, or directly via promoting the proliferation of vascular cells. This data suggests that a disruption on NGF regulation could be a component in ovarian disorders related with impaired angiogenesis.

Dopamine receptors in equine ovarian tissues

Dopamine (DA) agonist and antagonist treatments can affect ovarian reproductive events in the mare. To support our theory that DA produces these effects by acting directly on the ovary, we analyzed equine ovarian tissues for the presence of dopamine receptor-1 (D1r) and dopamine receptor-2 (D2r) mRNA by reverse transcription polymerase chain reaction (RT-PCR) and D1r and D2r proteins by Western blot and immunohistochemistry (IHC). RT-PCR was performed on RNA isolated from ovarian cortex, medulla, granulosa/theca or corpus luteum (CL) tissues and from pituitary (D2r control) and renal artery (D1r control). D1r and D2r specific primers were designed from partial DNA sequences known for the horse (D2r) or conserved sequences from other species (D1r). Western blot analyses were conducted on CL, cortex and granulosa/theca samples and IHC was performed on CL tissues using D1r or D2r specific antibodies. The incidence of positive D2r mRNA was high in CL and ovarian cortex, low in granulosa/theca, and not detectable in ovarian medulla. Dopamine D1r mRNA incidence was high (50%) only in CL tissues. D1r and D2r antibody staining was positive for each tissue type analyzed by Western blot procedures. All CL tissues prepared by IHC showed positive staining for D1r and D2r proteins. Both DA receptor proteins appeared uniformly distributed throughout the CL tissue. These results indicate that equine ovarian tissues do possess D1r and D2r, and suggests that DA can act directly on ovarian tissues through its interaction with DA receptors.

Immunolocalization of Nerve Growth Factor (NGF) and Its Receptors (TrkA and p75LNGFR) in the Reproductive Organs of Shiba Goats

The objective of this study was to determine the immunolocalization of NGF and its receptors (TrkA and p75LNGFR) in the reproductive tract of the Japanese Shiba goats. Five adult goats were used in this study and sections of ovaries, uteri and oviducts were immunostained by the avidin-biotin-peroxidase complex method (ABC). The results showed that NGF and its receptors (TrkA and p75LNGFR) were expressed in granulosa cells, theca cells, interstitial cells and lutein cells in ovaries. Immunoreactions for NGF, TrkA and p75LNGFR were also detectable in epithelial cells and muscle cells of the ampulla and isthmus of the oviduct, and in epithelial cells and uterine glands of the uterus. These results strongly suggest autocrine and paracrine regulation of reproductive function by NGF in the reproductive tract of female Shiba goats.

Expression of Nerve Growth Factor (NGF), and Its Receptors trkA and p75 in Ovaries of the Cyclic Golden Hamster (Mesocricetus auratus) and the Regulation of Their Production by Luteinizing Hormone

In the present study, changes in localization of nerve growth factor (NGF) and its receptors, trkA and p75 in the ovary were investigated during the estrous cycle of the golden hamster. The effect of LH surge on changes in localization of NGF, trkA and p75 in the ovary was also investigated. NGF and its receptors trkA and p75 were localized in oocytes, granulosa cells and theca cells of various stages of follicles throughout the estrous cycle. NGF and its two receptors were also present in numerous interstitial cells and luteal cells. The number of interstitial cells staining positively for NGF and its two receptors was greater in ovaries of day 1 (day 1=day of ovulation) than the other days during the estrous cycle. Treatment with the antiserum against luteinizing hormone releasing hormone (LHRH-AS) at 1100 h on day 4 completely blocked ovulation. There were few positive reactions for NGF and its two receptors in interstitial cells 24 hr after LHRH-AS injection. The effect of LHRH-AS treatment was blocked by a single injection of 10 IU human chorionic gonadotropin. The distinct widespread distribution of NGF and its two receptors in the ovary of golden hamsters suggest that NGF may be an important growth factor for regulation of ovarian function. Furthermore, the LH surge may be an important factor for inducing production of NGF and its two receptors in interstitial cells of the cyclic golden hamster.

Preovulatory rise of NGF in ovine follicular fluid: possible involvement in the control of oocyte maturation

Since nerve growth factor (NGF) is produced in vitro by granulosa cells after gonadotropin stimulation, the present research has been designed to investigate whether this neurotropin is involved in the events triggered by the gonadotropin surge that lead the follicle to ovulate a mature oocyte. To this aim, NGF levels in follicular fluid, collected before or 20 hours after the gonadotropin surge, was measured by ELISA. To evaluate whether NGF may have a non-neurotropic effect on follicle cells, the presence of NGF receptors was investigated by immunohistochemistry and further evaluated by analysing the tyrosine-phosphorylation pattern after NGF stimulation in vitro. The effect of NGF on the degree of cumulus expansion, cumulus-oocyte metabolic coupling, and meiotic maturation was finally studied by using the culture of follicle-enclosed oocyte. The results demonstrate that GnRH causes a dramatic rise of NGF in large follicles. Immunohistochemistry revealed a discrete positivity for trkA receptors localised in cumulus cells. Tyrosine phosphorylation pattern confirms that somatic cells are capable to transduce NGF signal. By contrast, all the oocytes examined were negative for trkA and did not change the phosphorylation pattern after NGF. In vitro NGF (100 ng/ml) induced a marked cumulus expansion and a progressive cumulus-oocyte uncoupling similar to that produced by gonadotropins. The addition of NGF also caused the resumption of meiosis in more than 70% of the oocytes analysed with an effect that is only slightly less pronounced than that of gonadotropins (80%). The increase in NGF secretion following gonadotropin surge suggests that this neurotropin may be involved in the control of oocyte maturation.

Follicle activation involves vascular endothelial growth factor production and increased blood vessel extension

The authors evaluated the relationship between vascular endothelial growth factor (VEGF) production, blood vessel extension, and steroidogenesis in small (<4 mm), medium (4-5 mm), and large (>5 mm) follicles isolated from gilts treated with eCG. VEGF and estradiol levels were measured in follicular fluid by an enzyme immunoassay and radioimmunoassay, respectively, and then each follicle wall was used to evaluate VEGF mRNA content and for the immunohistochemical analysis of blood vessels. VEGF production was low in small follicles (<3 ng/ml), high in large follicles (>10 ng/ml), and markedly differentiated in medium follicles; 44% exhibited values up to 15 ng/ml, whereas the levels never exceeded 3 ng/ml in the remaining aliquot. Medium follicles were then used as a model to investigate angiogenesis. Reverse transcription-polymerase chain reaction for VEGF mRNA demonstrated that granulosa cells represent the main component involved in the production of VEGF. The follicle wall, which presents two distinct concentric vessel networks, showed a vascular area (positive stained area/percent of field area) that was significantly wider in high VEGF follicles than in low VEGF follicles (2.54% +/- 0.58% vs. 1.29% +/- 0.58%, respectively). Medium follicles with high VEGF levels and extensive vascularization accumulated high estradiol levels (150-300 ng/ml), whereas follicles with low VEGF levels had basal estradiol levels that never exceeded 30 ng/ml. Early atretic medium-size follicles had undetectable levels of VEGF and estradiol paralleled by a marked reduction in blood vessel. The data presented propose an improved model for follicle dynamics in which the production of VEGF, stimulated by gonadotropin, creates the vascular conditions required for follicle growth and activity.