Expression and immunolocalisation of follicle-stimulating hormone receptors in gonads of newborn and adult female horses

Exogenous FSH/LH modulates TGF beta signaling genes in granulosa cells of Simmental heifers without affecting IVP results

Follicular wave synchronization and follicular superstimulation with FSH are commonly used in OPU-IVP programs to increase oocyte developmental competence. Factors like Growth Differentiation Factor 9 (GDF9) and Bone Morphogenetic Protein 15 (BMP15), from the TGF beta superfamily, are produced by the oocyte and modulate follicular function. The aim of this study was to analyze the FSH-induced effects on (1) embryo production in dual-purpose Simmental cattle, and (2) TGF beta-mediated effects on oocyte-granulosa cell communication. Simmental heifers (n = 12, age 484 ± 62 days) underwent two OPU-IVP cycles in a cross-over design. Follicular waves were synchronized using 0.5 mg cloprostenol on Day 0, followed by 10 μg buserelin on Day 2. Subsequently, half of the heifers were randomly assigned to receive FSH/LH (four injections of 75 IU FSHp and 75IU LHp, 12 h apart on Days 4 and 5) before the first OPU, while the remaining heifers received FSH/LH before the second OPU. At the time of OPU, i.e. 7 days after the start of synchronization, granulosa cells were collected for RT-qPCR analysis. FSH treatment did not affect the number of oocytes collected (17.3 vs. 13.3, P > 0.05), but increased the percentage of quality 1 oocytes compared to controls (45.7 % vs. 22.0 %, P < 0.001). Neither cleavage (86.4 % vs. 85.7 %), nor blastocyst (42.1 % vs. 39.3 %) rate, or the number of transferable embryos produced by IVP (4.1 vs 4.8) was influenced by FSH treatment (P > 0.05 in all cases). FSH treatment increased HIF1A and FSHR levels in granulosa cells, while STAR was decreased (P = 0.008 in all cases). FSH treatment did not affect BMP15 or GDF9 mRNA expression (P > 0.05) but appeared to modulate the expression of genes involved in the BMP signaling pathway. Transcriptional levels of BMP15 receptor (BMPR1A, P = 0.016), and its downstream signaling factor SMAD1 (P = 0.008) were affected by FSH treatment. Our results demonstrated no benefit of this FSH stimulation protocol on IVP results in Simmental heifers. Further, our results suggest that the effects of FSH on bovine oocytes during acquisition of developmental competence may be mediated through BMP, but do not involve the regulation of transcriptional availability of GDF9, providing new insights into possible paracrine effects of the oocyte on granulosa cells.

Ethanol, Carnoy, and paraformaldehyde as fixative solutions for histological evaluation of preantral follicles in equine ovarian tissue

The most adequate fixative solution for equine ovarian tissue is still to be determined as a tool to evaluate the improvement of methodological studies in assisted reproductive techniques and fertility preservation. This study aimed to evaluate a short-time ethanol 70% (ST-EtOH, 45 min) exposure as an alternative fixative compared with two classically fixatives [Carnoy's (CAR) solution and paraformaldehyde 4% (PFA)] at different fixation times (6 h, 12 h). The end points evaluated were morphology and classes of preantral follicles, follicular and stromal cell densities, and follicular and oocyte nuclear diameters in equine ovarian tissue. Ovaries (n = 6) from ovariectomized young mares were fragmented (3 × 3 × 1 mm; 20 fragments/ovary) and fixed in the tested treatments. Overall, a total of 11,661 preantral follicles were evaluated in 1444 histological slides. The ST-EtOH similarly preserved the preantral follicle morphometry and stromal cell density compared to the PFA fixative, regardless of the exposure time. Nonetheless, the CAR fixative solution had the greatest percentage of normal preantral follicles and the highest stromal cell density among all treatments. In conclusion, Carnoy's solution must be preferred compared with ST-EtOH and PFA fixatives for studies concerning the cellular morphology of equine ovarian tissue. Moreover, ST-EtOH fixative is a good alternative for equine ovarian tissue when a quick histological evaluation is required instead of more time-consuming and expensive techniques. Additional studies concerning the impact of different fixatives on the ultrastructure of cellular populations and their compatibility with IHC and molecular techniques in equine ovarian tissue are warranted.

Review: Roles of follicle-stimulating hormone in preantral folliculogenesis of domestic animals: what can we learn from model species and where do we go from here?

The pituitary gonadotropin FSH is a glycoprotein critical for the development of ovarian follicles. Upon binding to its G protein-coupled membrane receptor located on the granulosa cells of ovarian follicles, FSH elicits a cascade of downstream intracellular responses to promote follicle growth, maturation and steroidogenic activity, leading to the acquisition of meiotic and developmental competence of the enclosed oocyte. The essential role of FSH for proper antral follicle development and fertility is indisputable; over the decades, increasing evidence has also pointed toward survival and growth-promoting effects elicited by FSH in earlier-stage preantral follicles, deeming these follicles FSH-responsive as opposed to the FSH-dependent antral follicles. Transgenic mouse models lacking GnRH1, Fshβ or Fshr clearly demonstrate this difference by showing that, morphologically, preantral follicles develop to the secondary stage without FSH signaling; however, exogenous expression or administration of FSH to hormone-deficient mice promotes preantral follicle development, with more pronounced effects seen in earlier stages (i.e., primary follicles). In hypophysectomized sheep, FSH administration also promotes the growth of primary-stage preantral follicles. However, in vivo studies in this area are more challenging to perform in domestic animals compared to rodents, and therefore most of the research to date has been done in vitro. Here, we present the existing evidence for a role of FSH in regulating the growth and survival of preantral follicles from data generated in rodents and domestic animals. We provide an overview of the process of folliculogenesis, FSH synthesis and cellular signaling, and the response to FSH by preantral follicles in vivo and in vitro, as well as interactions between FSH and other molecules to regulate preantral folliculogenesis. The widespread use of FSH in ovarian stimulation programs for assisted reproduction creates a real need for a better understanding of the effects of FSH beyond stimulation of antral follicle growth, and more research in this area could lead to the development of more effective fertility programs. In addition to its importance as an agricultural species, the cow provides a desirable model for humans regarding ovarian stimulation due to similar timing of folliculogenesis and follicle size, as well as similar ovarian architecture. The refinement of minimally invasive methods to allow the study of preantral folliculogenesis in live animals will be critical to understand the short- and long-term effects of FSH in ovarian folliculogenesis.

Bone Morphogenetic Protein 15 (BMP-15) Improves In Vitro Mouse Folliculogenesis

Multilayered secondary follicles were encapsulated in a 0.5% alginate matrix and cultured in a 3D culture system supplemented with bone morphogenetic protein 15 (BMP-15; 15 ng/mL) for 12 days. The in vitro development of ovarian follicles was evaluated. On day 12, the follicle diameter, follicle survival rate, and antrum formation rate were significantly higher for follicles cultured in BMP-15-supplemented medium than those cultured in regular medium. The percentage of ovulated metaphase II oocytes retrieved from follicles cultured in BMP-15-supplemented medium was greater than that of oocytes retrieved from follicles cultured in regular medium. The secretion of P4 was significantly higher on days 6, 8, and 10 in follicles cultured in BMP-15-supplemented medium. The result for E2 tended toward significance on day 12. Intracellular reactive oxygen species levels were higher and glutathione levels were lower in mature oocytes from the in vitro culture than in mature oocytes from an in vivo control. A 3D culture system using an alginate matrix and supplemented with BMP-15 effectively improves the outcomes of in vitro ovarian follicle culture.

Differential expression of FSHR and LHR genes and proteins during development of rabbit ovarian follicles

The development of an ovarian follicle is a complex process at the cellular and molecular level that is mainly regulated by follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR). To elucidate the contribution of these receptors to ovarian follicle development, it is necessary to determine their expression profiles during this biological process. Therefore, this study aimed to investigate the relationship between ovarian development pattern and the differential ovarian expression pattern of FSHR and LHR genes as well as proteins at different developmental stages. Ovaries were collected from 30 New Zealand rabbits at day 0 (birth), week 2 (neonate), week 4 (cub), week 16 (maturity), and day 18 pregnancy. Ovarian histology, and gene as well as protein expression were determined using light microscopy, real-time PCR and western blotting, respectively. The results showed that the expression levels of FSHR mRNA and protein increased coincidently with age and the growth of ovarian follicles. The levels of LHR mRNA and protein remained low from the day of birth until week 4 and became significantly higher by week 16 coinciding with appearance of growing and antral follicles, which have a defined thecal layer. FSHR gene and protein expression decreased with pregnancy, whereas LHR increased, reaching a peak level during pregnancy. It can be concluded that changes in FSHR and LHR gene and protein expression could be related to the growth and development of follicles, indicating the regulatory role for these receptors in rabbit folliculogenesis.

Hemodynamic, endocrine, and gene expression mechanisms regulating equine ovarian follicular and cellular development

Ovulatory follicle development and associated oocyte maturation involve complex coordinated molecular and cellular mechanisms not yet fully understood. This study addresses the relationships among follicle diameter, follicle wall blood flow, follicular-fluid factors, and gene expression for follicle growth, steroidogenesis, angiogenesis, and apoptosis in granulosa/cumulus cells and oocytes during different stages from the beginning of largest/ovulatory follicle to impending ovulation in mares. The most remarkable findings were (i) a positive association between follicle development, follicle blood flow, intrafollicular follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone, and messenger RNA (mRNA) expression for FSHR and LHCGR in granulosa cells of the largest/ovulatory follicle; (ii) a plateau or decrease in follicle diameter and blood flow and granulosa cell mRNA for FSHR, LHCGR, IGF1R, VEGFR2, CYP19A1, and CASP3 at the preovulatory stage; (iii) higher StAR and BCL2 and lower CASP3 mRNA in granulosa cells at the time of impending ovulation; (iv) greater IGF1R mRNA for granulosa cells at the predeviation stage; and (v) lower FSHR, LHCGR, IGF1R, and VEGFR2 mRNA in cumulus cells and greater LHCGR and IGF1R mRNA in oocytes at the ovulatory stage. This study is a critical advance in the understanding of molecular mechanisms of follicle development and oocyte maturation and is expected to be vital for future studies targeting potential markers.

The Roles of the miRNAome and Transcriptome in the Ovine Ovary Reveal Poor Efficiency in Juvenile Superovulation

Simple Summary

Using the technology of juvenile superovulation, more follicles can be acquired in juvenile animals than in adult animals. However, oocytes derived from the follicles of juvenile animals are usually of poor quality, meaning that they have lower levels of subsequent maturation and embryonic development. In the present study, we used an exogenous hormone treatment to stimulate Hu sheep in order to compare the differences in ovarian superovulation effects and serum hormone secretion in juvenile and adult sheep. Differentially expressed microRNA (miRNA) and messenger RNA (mRNA) from the ovaries of juvenile and adult Hu sheep were then investigated using high-throughput sequencing technology to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment. We found that molecules of oar-miR-143 and follicle-stimulating hormone receptor (FSHR), among others, might regulate follicle formation, while oar-miR-485-3p, oar-miR-377-3p, and pentraxin 3 (PTX3), among others, may be associated with oocyte quality. The results will help us to identify miRNAs and mRNAs that could be used to predict ovarian superovulation potential and oocyte quality in the future.

Abstract

Juvenile superovulation can provide a wealth of oocyte material for embryo production, animal cloning, and genetic modification research, but embryos derived from juvenile oocytes show poor efficiency in subsequent developmental capacity. In order to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment, differentially expressed microRNAs (miRNAs) and messenger RNAs (mRNAs) were characterized and investigated in the ovaries of lambs and adult sheep using high-throughput sequencing technology. The majority of differentially expressed miRNAs (337/358) were upregulated in lamb libraries. The expression levels of mRNAs related to hormone receptors (follicle-stimulating hormone receptor, FSHR; luteinizing hormone/choriogonadotropin receptor, LHCGR; estrogen receptor 1, ESR1), steroid hormone secretion (cytochrome P450 family 11 subfamily A member 1, CYP11A1; cytochrome P450 family 17 subfamily A member 1, CYP17A1; cytochrome P450 family 19 subfamily A member 1, CYP19A1), and oocyte quality (pentraxin 3, PTX3; BCL2 apoptosis regulator, BCL2; caspase 3, CASP3) were significantly different between the lamb and adult libraries. The miRNA aor-miR-143, which targets FSHR, was highly and differentially expressed, and PTX3 was predicted to be targeted by oar-miR-485-3p and oar-miR-377-3p in the ovine ovary. A considerable number of miRNAs were predicted to inhibit ESR1 expression in lamb ovaries. In conclusion, oar-miR-143 and FSHR molecules, among others, might regulate follicle formation, and oar-miR-485-3p, oar-miR-377-3p, and PTX3, among others, may be associated with oocyte quality. These identified miRNAs and mRNAs will be beneficial for the prediction of ovarian superovulation potential and screening of oocytes.

Follicle-stimulating hormone administration affects amino acid metabolism in mammalian oocytes†

Culture media used in assisted reproduction are commonly supplemented with gonadotropin hormones to support the nuclear and cytoplasmic maturation of in vitro matured oocytes. However, the effect of gonadotropins on protein synthesis in oocytes is yet to be fully understood. As published data have previously documented a positive in vitro effect of follicle-stimulating hormone (FSH) on cytoplasmic maturation, we exposed mouse denuded oocytes to FSH in order to evaluate the changes in global protein synthesis. We found that dose-dependent administration of FSH resulted in a decrease of methionine incorporation into de novo synthesized proteins in denuded mouse oocytes and oocytes cultured in cumulus-oocyte complexes. Similarly, FSH influenced methionine incorporation in additional mammalian species including human. Furthermore, we showed the expression of FSH-receptor protein in oocytes. We found that major translational regulators were not affected by FSH treatment; however, the amino acid uptake became impaired. We propose that the effect of FSH treatment on amino acid uptake is influenced by FSH receptor with the effect on oocyte metabolism and physiology.

Harvesting, processing, and evaluation of in vitro-manipulated equine preantral follicles: A review

The mammalian ovary is responsible for essential stages of folliculogenesis and hormonal production, regulating the female physiological functions during the menstrual/estrous cycles. The mare has been considered an attractive model for comparative studies due to the striking similarities shared with women regarding in vivo and in vitro folliculogenesis. The ovarian follicular population in horses contains a large number of oocytes enclosed in preantral follicles that are yet to be explored. Therefore, the in vitro manipulation of equine preantral follicles aims to avoid the process of atresia and promote the development of follicles with competent oocytes. In this regard, after ovarian tissue harvesting, the use of appropriate processing techniques, as well as suitable approaches to evaluating equine preantral follicles and ovarian tissue, are necessary. Although high-quality equine ovarian tissue can be obtained from several sources, some critical aspects, such as the age of the animals, ovarian cyclicity, reproductive phase, and the types of ovarian structures, should be considered. Therefore, this review will focus on providing an update on the most current advances concerning the critical factors able to influence equine preantral follicle quality and quantity. Also, the in vivo strategies used to harvest equine ovarian tissue, the approaches to manipulating ovarian tissue post-harvesting, the techniques for processing ovarian tissue, and the classical approaches used to evaluate preantral follicles will be discussed.

Follicle-stimulating hormone receptors expression in ovine corpora lutea during luteal phase: effect of nutritional plane and follicle-stimulating hormone treatment

Corpus luteum (CL), a transient endocrine gland critical for reproductive cyclicity and pregnancy maintenance, is controlled by numerous regulatory factors. Although LH is widely recognized as the major regulator, other factors may also affect luteal functions. It has been demonstrated that FSH receptors (FSHR) are expressed not only in ovarian follicles but also in other tissues within the reproductive tract, including the CL. To evaluate FSHR expression in nontreated (nonsuperovulated; experiment 1) or FSH-treated (superovulated; experiment 2) sheep fed a control (C; maintenance), excess (O; 2 × C), or restricted (U; 0.6 × C) diet, CL were collected at the early, mid and/or late luteal phases (n = 5-7 per group). Protein and messenger RNA (mRNA) expression of FSHR were detected in the CL from all groups using immunohistochemistry followed by image analysis and quantitative RT-PCR, respectively. Follicle-stimulating hormone receptor was immunolocalized to steroidogenic small and large and nonsteroidogenic luteal cells. In both experiments, FSHR protein expression was not affected by stage of luteal development or diet. In experiment 1, expression of mRNA for all FSHR variants was greater (P <0.02 to 0.0003) at the late phase than mid or early luteal phase, and in experiment 2, it was greater (P < 0.001) at the mid than early luteal phase. Plane of nutrition did not affect FSHR mRNA expression. Comparison of FSH-treated with nontreated ewes demonstrated that FSH increased FSHR protein expression by 1.5- to 2-fold (P < 0.0001) in all groups, and mRNA expression by 7- to 30-fold (P < 0.001) for (1) FSHR-1 in all groups except U at the early luteal phase, (2) FSHR-2 in C, O, and U at the mid-phase, but not early luteal phase, and (3) FSHR-3 in U at the mid-luteal phase. Our data demonstrate that (1) FSHRs are expressed in ovine CL at several stages of luteal development, (2) FSHR protein expression does not change during the luteal phase and is not affected by diet, (3) FSHR mRNA expression not only depends on the stage of the estrous cycle but also not affected by diet in nonsuperovulated or superovulated ewes, and (4) in vivo FSH treatment enhanced FSHR protein and/or mRNA expression in the CL depending on diet and phase of the estrous cycle. Presence of FSHR in the CL indicates a regulatory role of FSH in luteal function in sheep. As very little is known about the possible role of FSH and FSHR in luteal functions, further studies should be undertaken to elucidate the endocrine, molecular, and cellular mechanisms of FSH effects on the CL.

Transition to the ovulatory season in mares: An investigation of antral follicle receptor gene expression in vivo

The inability to obtain in vivo samples of antral follicle wall layers without removing the ovaries or sacrificing the animals has limited more in-depth studies on folliculogenesis. In this study, a novel ultrasound-guided follicle wall biopsy (FWB) technique was used to obtain in vivo follicle wall layers and follicular fluid samples of growing antral follicles. The expression of proliferative, hormonal, angiogenic, and pro-/antiapoptotic receptors and proteins in the follicular wall among three follicle classes were compared during the spring transitional anovulatory (SAN) and spring ovulatory (SOV) seasons in mares. The main findings observed in the granulosa, theca interna, and/or all follicle layers during the SOV season compared with the SAN season were (a) small-sized follicles (10-14 mm) had greater epidermal growth factor receptor (EGFR) and Bcl-2 expression; (b) medium-sized follicles during the expected deviation/selection diameter (20-24 mm) had greater expression of EGFR, Ki-67, luteinizing hormone receptor (LHR), and Bcl-2; and (c) dominant follicles (30-34 mm) had greater EGFR, Ki-67, vascular endothelial growth factor, LHR, and Bcl-2 expression. Estradiol related receptor alpha expression and intrafollicular estradiol concentration increased, along with an increase in follicle diameter in both seasons. In this study, the application of the FWB technique allowed a direct comparison of different receptors' expression among follicles in different stages of development and between two seasons using the same individuals, without jeopardizing their ovarian function. The successful utilization of the FWB technique and the mare as an experimental animal offer a great combination for future folliculogenesis studies on mechanisms of follicle selection, development, and ovulation in different species, including women.

Effects of Matricaria chamomilla Extract on Growth and Maturation of Isolated Mouse Ovarian Follicles in a Three-dimensional Culture System

BACKGROUND

The aim of this study was to design and assess the effects of hydroalcoholic extract of Matricaria chamomilla (MC) on preantral follicle culture of mouse ovaries in a three-dimensional culture system.

METHODS

Isolated preantral follicles were randomly divided into three main groups: the control group containing 10% fetal bovine serum without MC extract (G1), the first experimental group supplemented with 25 μg/ml hydroalcoholic extract of chamomile (G2), and the second experimental group supplemented with 50 μg/ml hydroalcoholic extract of chamomile (G3).

RESULTS

After 12 days of culture, the survival rate (P < 0.05), antrum formation (P < 0.01), metaphase two oocytes (P < 0.01), and the expression of PCNA (P < 0.05) and FSHR (P < 0.05) genes significantly decreased in G3 as compared with G1. On the other hand, at the last day of culture (day 12), the mean diameter of follicles cultured in the medium which was supplemented with 50 μg/ml hydroalcoholic extract of chamomile significantly decreased as compared with the G1 (P < 0.05). In addition, the levels of progesterone and dehydroepiandrosterone hormones significantly increased in the medium of G3 relative to G1 (P < 0.01), while in the medium of G1, the level of 17β-estradiol was significantly higher than that of other groups (P < 0.01). Reactive oxygen species levels of metaphase II oocytes were significantly decreased in G2 as compared with G1 (P < 0.01).

CONCLUSION

Adding chamomile extract to culture media appeared to decrease follicular function and development.

In vivo antral follicle wall biopsy: a new research technique to study ovarian function at the cellular and molecular levels

BACKGROUND

In vivo studies involving molecular markers of the follicle wall associated with follicular fluid (FF) milieu are crucial for a better understanding of follicle dynamics. The inability to obtain in vivo samples of antral follicle wall (granulosa and theca cells) without jeopardizing ovarian function has restricted advancement in knowledge of folliculogenesis in several species. The purpose of this study in mares was to develop and validate a novel, minimally invasive in vivo technique for simultaneous collection of follicle wall biopsy (FWB) and FF samples, and repeated collection from the same individual, during different stages of antral follicle development. We hypothesized that the in vivo FWB technique provides samples that maintain the normal histological tissue structure of the follicle wall layers, offers sufficient material for various cellular and molecular techniques, and allows simultaneous retrieval of FF.

METHODS

In Experiment 1 (ex vivo), each follicle was sampled using two techniques: biopsy forceps and scalpel blade (control). In Experiment 2 (in vivo), FWB and FF samples from 10-, 20-, and 30-mm follicles were repeatedly and simultaneously obtained through transvaginal ultrasound-guided technique.

RESULTS

In Experiment 1, the thickness of granulosa, theca interna, and theca externa layers was not influenced (P > 0.05) by the harvesting techniques. In Experiment 2, the overall recovery rates of FWB and FF samples were 97 and 100%, respectively. However, the success rate of obtaining samples with all layers of the follicle wall and clear FF varied according to follicle size. The expression of luteinizing hormone receptor (LHR) was mostly confined in the theca interna layer, with the estradiol-related receptor alpha (ERRα) in the granulosa and theca interna layers. The 30-mm follicle group had greater (P < 0.05) LHR expression in the theca interna and ERRα in the granulosa layer compared to the other groups. The overall expression of LHR and ERRα, and the intrafollicular estradiol were higher (P < 0.05 - P < 0.0001) in the 30-mm follicle group.

CONCLUSION

The in vivo technique developed in this study can be repeatedly and simultaneously used to provide sufficient FWB and FF samples for various cellular and molecular studies without jeopardizing the ovarian function, and has the potential to be translated to other species, including humans.

Follicle stimulating hormone receptor protein is expressed in ovine uterus during the estrous cycle and utero-placenta during early pregnancy: An immunohistochemical study

Follicle stimulating hormone (FSH) is a well characterized gonadotropin that controls primarily development and functions of ovarian follicles in mammalian species. FSH binds to a specific G protein-coupled receptor (FSHR) belonging to the glycoprotein hormone receptor family that plays an essential role in reproduction. Although the primary location of FSHR is in the gonads (mainly in ovarian follicles), FSHR protein and/or mRNA have also been detected in extragonadal female reproductive tissues including embryo, placenta, endometrium, cervix, ovarian cancer tissues, and/or endometriotic lesions in several species. To determine the pattern of FSHR expression in the uterus and placenta, uterine tissues were collected at the early, mid- and/or late luteal phases of the estrous cycle from non-treated or FSH-treated ewes, and utero-placental tissues were collected during early pregnancy followed by immunohistochemistry and image generation. FSHR was immunolocalized to several uterine and utero-placental compartments including luminal epithelium, endometrial glands and surrounding stroma, myometrium, and endothelium and vascular smooth muscle cells in endometrium, myometrium and mesometrium. Intensity of staining and distribution of FSHR in selected compartments differed and seems to depend on the stage of the estrous cycle or pregnancy, and FSH-treatment. These novel data demonstrate differential expression of FSHR protein indicating that FSH plays a specific role in regulation of uterine and utero-placenta functions in sheep.

Anti-Müllerian hormone profiling in prepubertal horses and its relationship with gonadal function

Anti-Müllerian hormone (AMH) has gained increasing interest as a biomarker for assessment of gonadal activity. The ability to predict the ovarian follicular reserve of prepubertal female horses (fillies) or to identify stallions with testicular pathologies already during their prepubertal life has not been analyzed so far. Both would help to select fertile horses and reduce costs associated with keeping animals. The objectives of the present study were to (1) assess AMH, LH, FSH, progesterone (females) and testosterone (males) dynamics in prepubertal horses from birth onwards and (2) determine whether AMH concentrations detected in plasma of prepubertal female and male horses are correlated with postpubertal gonadal development. Warmblood foals (n = 30, 14 females, 10 normal males and 6 males with abnormal testicular development) born between February and May of two consecutive years (n = 28 in the first year and n = 2 the next year), were included in the study. Information on gestational length, parity of the dam and placental weight was collected for all foals. Blood samples for hormone analysis were collected from birth onwards every four weeks up to the age of one year. At two years, blood samples were collected on the day when antral follicle count (AFC) and total testicular volume (TTV) were assessed. AMH was detectable in the plasma of all animals from birth onwards and its concentration was significantly higher (P < .001) in males than in females, regardless of testicular development. In males, AMH and testosterone concentration were similar for all animals during the first year of life, regardless of testicular development. At two years, AMH concentration was higher (P < .05) in males with abnormal testicular development than in those with normal testes. In females, AMH concentration at two years was correlated with AMH concentration at birth (P < .05) and with AFC (P < .001). At birth, LH concentration was lower (P < .05) in stallions with abnormal testes (0.3 ± 0.2 ng/ml) than in controls (0.6 ± 0.2 ng/ml). A high negative correlation between AMH concentration and gestation length was observed in males during the first eight weeks of life (P < .01, r = -0.64 to -0.71). Elevated progesterone concentrations over 1 ng/ml were observed in several females starting with 20 weeks of age. This was paralleled by an increase in AMH concentration and was preceded by FSH and LH increases. In conclusion, AMH determination can be reliably used from two years onwards to identify stallions with abnormal testicular development, but it is inconclusive before puberty. In female horses, determination of AMH concentration at a prepubertal age allows for prediction of AMH and AFC after puberty. We suggest that premature luteinisation occurs before the onset of puberty in female horses and that LH secretion in the perinatal period is involved in testicular development and descent in the horse.

Anti-Muellerian hormone, inhibin A, gonadotropins, and gonadotropin receptors in bull calves after partial scrotal resection, orchidectomy, and Burdizzo castration

Eight-week-old calves were either castrated by partial scrotal resection (SR) without removing the testes (n = 10), Burdizzo (BZ) clamp (n = 10), orchidectomy (OR; n = 10), or were left gonad intact as controls (CO; n = 10). Concentrations of anti-Muellerian hormone (AMH), inhibin A, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in plasma were determined from 16 to 48 weeks of age. At 18 months, testes of SR, BZ, and CO bulls were obtained and the immunolocalization of LH and FSH receptors and AMH analyzed. Concentration of AMH in plasma of CO and SR bulls decreased with increasing age (P < 0.001). A similar AMH profile in CO and SR indicates that SR did not induce a true cryptorchid state. In groups OR and BZ, AMH was undetectable. Plasma inhibin concentration was higher in groups CO and SR than BZ and OR (P < 0.001). Plasma LH and FSH concentrations decreased over time (P < 0.001) and were higher in groups BZ and OR than SR and CO (P < 0.001). In the testes, immunolabeling for AMH existed in Sertoli cells of CO and SR but not BZ bulls. FSH receptors were localized in Sertoli cells, Leydig cells, spermatocytes, and the epididymis of CO and SR animals, whereas LH receptors were restricted to Leydig cells. In BZ animals, FSH and LH receptors and AMH were absent, indicating complete testicular degeneration. In conclusion, AMH is a more reliable marker for the presence of testicular tissue in bulls than inhibin. Scrotal resection did not induce a true inguinal cryptorchid state but affected testicular responsiveness to gonadotropic stimulation.

The Orthology Clause in the Next Generation Sequencing Era: Novel Reference Genes Identified by RNA-seq in Humans Improve Normalization of Neonatal Equine Ovary RT-qPCR Data

BACKGROUND

Vertebrate evolution is accompanied by a substantial conservation of transcriptional programs with more than a third of unique orthologous genes showing constrained levels of expression. Moreover, there are genes and exons exhibiting excellent expression stability according to RNA-seq data across a panel of eighteen tissues including the ovary (Human Body Map 2.0).

RESULTS

We hypothesized that orthologs of these exons would also be highly uniformly expressed across neonatal ovaries of the horse, which would render them appropriate reference genes (RGs) for normalization of reverse transcription quantitative PCR (RT-qPCR) data in this context. The expression stability of eleven novel RGs (C1orf43, CHMP2A, EMC7, GPI, PSMB2, PSMB4, RAB7A, REEP5, SNRPD3, VCP and VPS29) was assessed by RT-qPCR in ovaries of seven neonatal fillies and compared to that of the expressed repetitive element ERE-B, two universal (OAZ1 and RPS29) and four traditional RGs (ACTB, GAPDH, UBB and B2M). Expression stability analyzed with the software tool RefFinder top ranked the normalization factor constituted of the genes SNRPD3 and VCP, a gene pair that is not co-expressed according to COEXPRESdb and GeneMANIA. The traditional RGs GAPDH, B2M, ACTB and UBB were only ranked 3rd and 12th to 14th, respectively.

CONCLUSIONS

The functional diversity of the novel RGs likely facilitates expression studies over a wide range of physiological and pathological contexts related to the neonatal equine ovary. In addition, this study augments the potential for RT-qPCR-based profiling of human samples by introducing seven new human RG assays (C1orf43, CHMP2A, EMC7, GPI, RAB7A, VPS29 and UBB).