Inhibin removes the inhibitory effects of activin on steroid enzyme expression and androgen production by normal ovarian thecal cells

Gonadotropin elevation is ootoxic to ovulatory oocytes and inhibits oocyte maturation, and activin decoy receptor ActRIIB:Fc therapeutically restores maturation

BACKGROUND

Elevated FSH often occurs in women of advanced maternal age (AMA, age ≥ 35) and in infertility patients undergoing controlled ovarian stimulation (COS). There is controversy on whether high endogenous FSH contributes to infertility and whether high exogenous FSH adversely impacts patient pregnancy rates.

METHODS

The senescence-accelerated mouse-prone-8 (SAMP8) model of female reproductive aging was employed to assess the separate impacts of age and high FSH activity on the percentages (%) of viable and mature ovulated oocytes recovered after gonadotropin treatment. Young and midlife mice were treated with the FSH analog equine chorionic gonadotropin (eCG) to model both endogenous FSH elevation and exogenous FSH elevation. Previously we showed the activin inhibitor ActRIIB:Fc increases oocyte quality by preventing chromosome and spindle misalignments. Therefore, ActRIIB:Fc treatment was performed in an effort to increase % oocyte viability and % oocyte maturation.

RESULTS

The high FSH activity of eCG is ootoxic to ovulatory oocytes, with greater decreases in % viable oocytes in midlife than young mice. High FSH activity of eCG potently inhibits oocyte maturation, decreasing the % of mature oocytes to similar degrees in young and midlife mice. ActRIIB:Fc treatment does not prevent eCG ootoxicity, but it restores most oocyte maturation impeded by eCG.

CONCLUSIONS

FSH ootoxicity to ovulatory oocytes and FSH maturation inhibition pose a paradox given the well-known pro-growth and pro-maturation activities of FSH in the earlier stages of oocyte growth. We propose the FOOT Hypothesis ("FSH OoToxicity Hypothesis), that FSH ootoxicity to ovulatory oocytes comprises a new driver of infertility and low pregnancy success rates in DOR women attempting spontaneous pregnancy and in COS/IUI patients, especially AMA women. We speculate that endogenous FSH elevation also contributes to reduced fecundity in these DOR and COS/IUI patients. Restoration of oocyte maturation by ActRIB:Fc suggests that activin suppresses oocyte maturation in vivo. This contrasts with prior studies showing activin A promotes oocyte maturation in vitro. Improved oocyte maturation with agents that decrease endogenous activin activity with high specificity may have therapeutic benefit for COS/IVF patients, COS/IUI patients, and DOR patients attempting spontaneous pregnancies.

FTO demethylates regulates cell-cycle progression by controlling CCND1 expression in luteinizing goat granulosa cells

In mammals, N6-methyladenosine (m6A) stands out as one of the most abundant internal mRNA modifications and plays a crucial role in follicular development. Nonetheless, the precise mechanism by which the demethylase FTO regulates the progression of the goat luteinizing granulosa cells (LGCs) cycle remains to be elucidated. In our study, we primarily assessed the protein and mRNA expression levels of genes using Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), cell proliferation via EdU, cell viability with CCK-8, and apoptosis and cell cycle progression through flow cytometry. Here, the results demonstrated that knockdown of FTO significantly enhanced apoptosis, impeded cell proliferation, and increased autophagy levels in goat LGCs. Furthermore, the silencing of FTO substantially reduced cyclin D1 (CCND1) expression through the recognition and degradation of YTHDF2, consequently prolonging the cell cycle progression. This study sheds light on the mechanism by which FTO demethylation governs cell cycle progression by controlling the expression of CCND1 in goat LGCs, underscoring the dynamic role of m6A modification in the regulation of cell cycle progression.

miR-423 sponged by lncRNA NORHA inhibits granulosa cell apoptosis

BACKGROUND

Atresia and degeneration, a follicular developmental fate that reduces female fertility and is triggered by granulosa cell (GC) apoptosis, have been induced by dozens of miRNAs. Here, we report a miRNA, miR-423, that inhibits the initiation of follicular atresia (FA), and early apoptosis of GCs.

RESULTS

We showed that miR-423 was down-regulated during sow FA, and its levels in follicles were negatively correlated with the GC density and the P4/E2 ratio in the follicular fluid in vivo. The in vitro gain-of-function experiments revealed that miR-423 suppresses cell apoptosis, especially early apoptosis in GCs. Mechanically speaking, the miR-423 targets and interacts with the 3'-UTR of the porcine SMAD7 gene, which encodes an apoptosis-inducing factor in GCs, and represses its expression and pro-apoptotic function. Interestingly, FA and the GC apoptosis-related lncRNA NORHA was demonstrated as a ceRNA of miR-423. Additionally, we showed that a single base deletion/insertion in the miR-423 promoter is significantly associated with the number of stillbirths (NSB) trait of sows.

CONCLUSION

These results demonstrate that miR-423 is a small molecule for inhibiting FA initiation and GC early apoptosis, suggesting that treating with miR-423 may be a novel approach for inhibiting FA initiation and improving female fertility.

Follicle development in pigs: State of the art

Understanding the factors and pathways involved with recruitment, atresia, and selection of follicles in the pig, may provide insight into approaches to limit fertility failures. Antral follicles depend upon FSH to the 2-3 mm stage, become codependent upon LH at 4-5 mm, and rely on LH when >5 mm. Within the follicle, gonadotropin binding, steroids, growth factors, and inhibin interact to determine the fate of the follicle. Continuous recruitment appears likely for follicles, and once >1 mm, they may have a limited period for survival, before selection or atresia. If true, then the number of healthy follicles that can respond to a hormone signal for selection, could vary by size and development stage. Which follicles are selected may depend upon their age, numbers of capillaries, granulosa and thecal cells, and FSH and LH receptors. This might also suggest that factors such as management, nutrition, and stress in prior weeks, could affect different cohorts of follicles to determine which of those from the ovarian population will be selected.

Rectifying cow infertility under heat stress by immunization against inhibin and supplementation of progesterone

This study was undertaken for the development of novel techniques that are based on immunoneutralization of inhibin bioactivity to improve Holstein cow fertility. A series of 4 experiments were carried out on 2 farms that were located in subtropical or temperate regions, to test the effects of immunization against inhibin alpha subunit on cow fertility under varying degrees of heat stress conditions. Though immunization against inhibin alone improved conception rate (CR) after TAI moderately in cows under mild heat stress conditions, the treatment plus progesterone supplementation substantially enhanced CR in the range of 25 to 35 percentages from severe heat stress to comfortable weather conditions. There existed an additive effect between immunization against inhibin and progesterone supplementation that maximally enhanced CR. Further, immunization against inhibin increased both FSH and activin A concentrations in blood during both follicular and luteal phases. It also significantly increased blood concentrations of E2 in the follicular phase but decreased P4 concentrations during the early pregnancy. However, interferon-tau concentrations in blood around the time of pregnancy recognition were doubled in the inhibin immunized cows. In conclusion, immunization against inhibin plus P4 treatment enhances ovarian follicle and the subsequent early embryo developments that help to greatly improve the fertility of Holstein dairy cows.

Synergistic Regulatory Effect of Inhibin and Anti-Müllerian Hormone on Fertility of Mice

Inhibin (INH) and anti-Müllerian hormone (AMH) are essential in ovarian folliculogenesis and play an inhibitory role in mammalian fertility. However, the interactive effect of INH and AMH on the animal reproduction remains unknown. This study aimed to determine the possible interaction and synergy between INH and AMH in steroidogenesis by primary granulosa cells, and investigate their synergistic effect on fertility in mice. In in vitro granulosa cell culture system, we found that the treatment of either INHA or AMH had no significant effect on basal estradiol and progesterone production, whereas both significantly attenuated FSH-induced steroid hormone secretion. Importantly, combined treatment with INHA and AMH showed additive inhibitory effect on FSH-induced estradiol and progesterone production, accompanying a significant downregulation in the expression of FSH-stimulated CYP19A1, HSD3B, CYP11A1, StAR transcripts. The interrelationship of INH and AMH combinations was further investigated through active immune neutralization strategy. Female mice were immunized against INH and AMH eukaryotic expression plasmids, and the litter size was recorded after successfully mating. We observed that both INH and AMH plasmids were able to induce either anti-AMH or anti-INH antibodies in the immunized mice. In comparison with the control group, co-immunization with INH and AMH plasmids induced higher levels of estradiol, resulting in more litter size. Moreover, there was no significant difference on the offspring's weight between each group. Collectively, the results of the present study suggest that INH and AMH have synergistic effect in regulating steroidogenesis and the litter size in mice.

INHBA transfection regulates proliferation, apoptosis and hormone synthesis in sheep granulosa cells

Inhibin subunit beta A (INHBA) participates in the synthesis of inhibin A, activin A and activin AB. Here we investigated the effect and molecular mechanism of INHBA on proliferation, apoptosis and hormone synthesis in sheep granulosa cells (GCs) using in vitro transfection. We first noticed that INHBA expression increased with follicle diameter and was widely distributed in ovarian tissue. The proliferation rate of GCs was significantly increased and decreased with overexpression and silence of INHBA, respectively, compared with the negative controls. INHBA transfection affected GC proliferation and apoptosis, regulating the expression of many cell cycle-related and apoptosis-related genes. INHBA overexpression significantly decreased activin and estradiol secretion while increasing inhibin and progesterone secretion. The expression of follicle-stimulating hormone beta subunit was significantly decreased and increased with INHBA overexpression and knockdown, respectively. Notably, silence of INHBA inhibited the expression of many transforming growth factor beta-related genes. Overall, the functional molecule of INHBA gene may be associated with follicular development via regulating proliferation, apoptosis and folliculogenesis-related hormone secretion of sheep GCs. In addition, our findings may contribute to a better understanding of the law of follicular development and thus improve the reproductive performance of female animals.

The Involvement of Granulosa Cells in the Regulation by Gonadotropins of Cyp17a1 in Theca Cells

BACKGROUND/AIM

Theca cells produce androgen by 17α-hydroxylase-17,20-lyase encoded by Cyp17a1, and conversion of androgen to estrogen in granulosa cells is regulated by gonadotropins. Women with polycystic ovarian syndrome (PCOS) exhibit elevated levels of androgens due to high Cyp17a1 expression and alterations in gene expression in granulosa cells. The aim of this study was to examine the interaction between theca and granulosa cells in PCOS-model mice.

MATERIALS AND METHODS

To produce PCOS-model mice, neonatal mice were injected with 1 μg TP for 3 days from the day of birth. Gonadotropins were injected according to the superovulation protocol to 3-month-old control mice and PCOS-model mice. Histological changes and expression of genes involved in steroidogenesis, ovulation and luteinization were investigated by immunohistochemistry and real-time RT-PCR, respectively.

RESULTS

Pregnant mare serum gonadotropin (PMSG) induced the expression of genes involved in steroidogenesis in control prepubertal mice, whereas human chorionic gonadotropin (hCG) reduced Cyp17a1 expression and induced phospho-ERK1/2 in granulosa cells. Cyp17a1 was reduced in PMSG-primed PCOS-model mice regardless of hCG injection, and PMSG induced phosphorylation of ERK1/2 in granulosa cells.

CONCLUSION

Phospho-ERK1/2 in granulosa cells can be correlated with reduced Cyp17a1 expression in theca cells, and the interaction between granulosa and theca cells may be impaired in PCOS-model mice.

Effects of bimagrumab, an activin receptor type II inhibitor, on pituitary neurohormonal axes

BACKGROUND

Bimagrumab is a human monoclonal antibody inhibitor of activin type II receptors (ActRII), with anabolic action on skeletal muscle mass by blocking binding of myostatin and other negative regulators of muscle growth. Bimagrumab is under evaluation for muscle wasting and associated functional loss in hip fracture and sarcopenia, and in obesity. Bimagrumab also blocks other endogenous ActRII ligands, such as activins, which act on the neurohormonal axes, pituitary, gonads and adrenal glands.

AIM

To evaluate the effect of bimagrumab on the pituitary-gonadal and pituitary-adrenal axes in humans.

METHODS

Healthy men and women, aged 55 to 75 years, received bimagrumab intravenously 10 mg/kg or placebo on Day 1 and Day 29. Pituitary-gonadal and pituitary-adrenal functions were evaluated with basal hormone measurement and standard gonadotropin-releasing hormone (GnRH) and adrenocorticotropic hormone (ACTH) stimulation tests at baseline, Week 8 and at the end of study (EOS)-Week 20.

RESULTS

At Week 8, follicle-stimulating hormone (FSH) levels were reduced by 42.16 IU/L (P < .001) and luteinizing hormone (LH) levels were increased by 2.5 IU/L (P = .08) over placebo in response to bimagrumab in women but not in men. Effects that were reversible after bimagrumab was cleared. Gonadal and adrenal androgen levels were not affected by exposure to bimagrumab.

CONCLUSION

Bimagrumab alters the function of pituitary gonadotroph cells, consistent with blockade of activin on local ActRII. This effect is reversible with clearance of bimagrumab. Bimagrumab did not impact gonadal and adrenal androgen secretion.

Leydig cell insufficiency in hypospermatogenesis: a paracrine effect of activin-inhibin signaling?

Clinical findings and a variety of experimental models indicate that Leydig cell dysfunction accompanies damage to the seminiferous tubules with increasing severity. Most studies support the idea that intratesticular signaling from the seminiferous tubules to Leydig cells regulates steroidogenesis, which is disrupted when hypospermatogenesis occurs. Sertoli cells seem to play a pivotal role in this process. In this review, we summarize relevant clinical and experimental observations and present evidence to support the hypothesis that testicular activin signaling and its regulation by testicular inhibin may link seminiferous tubular dysfunction to reduced testosterone biosynthesis.

Establishment of an in vitro culture model of theca cells from hierarchical follicles in ducks

Theca cells, including theca interna cells and theca externa cells, are vital components of ovarian follicles. The aim of the present study is to identify a reliable method for the in vitro culture of theca cells from duck ovarian hierarchical (F4-F2) follicles. We improved the method for cell separation by using trypsin to further remove granular cells, and we increased the concentration of fetal bovine serum used in in vitro culture to improve cytoactivity. Cell antibody immunofluorescence (IF) showed that all inoculated cells could be stained by the CYP17A1/19A1 antibody but not by the FSHR antibody, which could stain granulosa cells. Furthermore, morphological differences were observed between the outlines of theca interna and externa cells and in their nuclei. Growth curve and CYP17A1/19A1 mRNA relative expression analyses suggested that the growth profile of theca interna cells may have been significantly different from that of theca externa cells in vitro Theca interna cells experienced the logarithmic phase on d1-d2, the plateau phase on d2-d3, and the senescence phase after d3, while theca externa cells experienced the logarithmic phase on d1-d3, the plateau phase on d3-d5, and the senescence phase after d5. Taken together, these results suggested that we have successfully established a reliable theca cell culture model and further defined theca cell characteristics in vitro.

The Steroid Metabolome in the Isolated Ovarian Follicle and Its Response to Androgen Exposure and Antagonism

The ovarian follicle is a major site of steroidogenesis, crucially required for normal ovarian function and female reproduction. Our understanding of androgen synthesis and metabolism in the developing follicle has been limited by the sensitivity and specificity issues of previously used assays. Here we used liquid chromatography-tandem mass spectrometry to map the stage-dependent endogenous steroid metabolome in an encapsulated in vitro follicle growth system, from murine secondary through antral follicles. Furthermore, follicles were cultured in the presence of androgen precursors, nonaromatizable active androgen, and androgen receptor (AR) antagonists to assess effects on steroidogenesis and follicle development. Cultured follicles showed a stage-dependent increase in endogenous androgen, estrogen, and progesterone production, and incubations with the sex steroid precursor dehydroepiandrosterone revealed the follicle as capable of active androgen synthesis at early developmental stages. Androgen exposure and antagonism demonstrated AR-mediated effects on follicle growth and antrum formation that followed a biphasic pattern, with low levels of androgens inducing more rapid follicle maturation and high doses inhibiting oocyte maturation and follicle growth. Crucially, our study provides evidence for an intrafollicular feedback circuit regulating steroidogenesis, with decreased follicle androgen synthesis after exogenous androgen exposure and increased androgen output after additional AR antagonist treatment. We propose that this feedback circuit helps maintain an equilibrium of androgen exposure in the developing follicle. The observed biphasic response of follicle growth and function in increasing androgen supplementations has implications for our understanding of polycystic ovary syndrome pathophysiology and the dose-dependent utility of androgens in in vitro fertilization settings.

Hallmarks of Human Small Antral Follicle Development: Implications for Regulation of Ovarian Steroidogenesis and Selection of the Dominant Follicle

Regulation of human ovarian steroidogenesis differs from other species and precise knowledge on how human small antral follicles (hSAF) develop and acquire competence for continued growth and steroid output is still incomplete. The present study has characterized almost 1,000 normal hSAF collected in connection with cryopreservation of ovarian tissue for fertility preservation. The antral follicles (ranging from 3 to 13 mm) were generally aspirated from one ovary surgically removed during the natural cycle, and the follicular fluid (FF) and the granulosa cells (GC) were isolated and snap-frozen. In FF, the following hormones were measured: inhibin-B, inhibin-A, AMH, follistatin, PAPP-A, estradiol, progesterone, testosterone, and androstenedione. In GC, mRNA gene expressions using q-PCR were measured for the following genes: FSHR, AMH, CYP19, and AR. All samples in which one of the abovementioned parameters was measured were included, but typically multiple parameters were measured. Highly significant differences in concentration and follicular content in relation to follicular diameter were found for all measured hormones despite massive variability in-between follicles for any given diameter. The results demonstrate that profound changes take place in the hormonal microenvironment around follicular diameters of 8-11 mm corresponding to when follicular selection occurs. At this point, inhibin-B and inhibin-A showed distinct peaks concomitant with a significant reduction in both AMH protein and mRNA expression. Concentrations of inhibins, androgens, FSHR, and AR were intimately associated, and it is suggested that inhibin-B in combination with PAPP-A and thereby IGF2 activity exerts important paracrine signaling at follicular selection. At the same time upregulation of estradiol synthesis and CYP19 mRNA expression increased steroid output profoundly. Furthermore, the highly significant association between FSHR and AR mRNA gene expression enforces important functions of androgens in follicular development. Collectively, these data reintroduce the understanding of the follicular phase as two parted in which regulation of steroidogenesis differs. The profound changes taking place around follicular selection highlight important paracrine actions of TGF-β family members and IGFs for securing dominance of the selected follicle.

Inhibin-B secretion and FSH isoform distribution may play an integral part of follicular selection in the natural menstrual cycle

The aim of the present paper is to expand the concept on how follicular selection takes place in the follicular phase of the natural menstrual cycle. It is suggested that inhibin-B exerts a more intimate role in this process than previously understood. Inhibin-B shows a peak in the circulation around cycle day 7, simultaneous with selection of the dominant follicle, whereas levels of estradiol and inhibin-A only start to increase a few days later suggesting that inhibin-B is mainly responsible for downregulating pituitary FSH release. New data now demonstrate that the circulatory peak of inhibin-B is reflected by peak production of inhibin-B, in contrast to inhibin-A, in the selected follicle with a diameter of 10-12 mm, where concentrations are one thousand times higher than in the circulation. This high inhibin-B concentration also exerts paracrine effects, stimulating theca cell androgen production in concert with LH. New data now suggest that in the corresponding granulosa cells androgens upregulate FSH receptor (FSHR) and LH receptor (LHR) mRNA expression, which in turn stimulate CYP19a mRNA expression providing the follicles which most effectively undertake these processes with the best chance of becoming selected. Inhibin-B production is stimulated by FSH and it appears that the acidic isoforms of FSH induce inhibin-B secretion most efficiently thereby, for the first time, placing the changing FSH isoform profile during the follicular phase in a physiological context. Collectively, it appears that inhibin-B is an integral part of follicular selection in the normal menstrual cycle, exerting both endocrine and paracrine effects and facilitating continued growth of the selected follicle.

A new insertion/deletion fragment polymorphism of inhibin-α gene associated with follicular cysts in Large White sows

Ovarian follicular cysts are anovulatory follicular structures that lead to infertility. Hormones play key roles in the formation and persistence of cysts. Inhibins are heterodimeric gonadal glycoprotein hormones that belong to the transforming growth factor-β superfamily. These hormones suppress the secretion of follicle-stimulating hormone. In this report, partial fragment of inhibin-α (INHA) subunit gene of Large White pig was detected from the genomic DNA by polymerase chain reaction. The sequence showed a 283 bp fragment insertion/deletion (I/D) polymorphism in INHA subunit gene. A total of 49 Large White sows with cystic follicles and 152 normal sows were screened for this polymorphism. The relationship of INHA I/D polymorphisms with follicular cysts was investigated. The distribution of I/D was significantly different between cystic and normal sows, thereby suggesting that the INHA subunit gene might be a potential biological marker for breeding programs in pig.

Downregulation of the expression of inhibin α subunit and betaglycan in porcine cystic follicles

Inhibins, as members of the transforming growth factor beta (TGF-β) superfamily, downregulate the synthesis and secretion of follicle-stimulating hormone (FSH) in an endocrine manner. The role of inhibin/betaglycan in the ovary regulation recently gained attention. To date, no data exist on the function of inhibin α subunit and betaglycan in cystic follicles. In this study, the expressions of inhibin α subunit and betaglycan in cystic follicles were investigated using immunohistochemistry, real-time PCR and Western blot analysis. Both inhibin α subunit and betaglycan immunoreactivities were mainly localized in the granulosa cells of follicles. Expression of inhibin α subunit and betaglycan was inferior in cystic follicles compared with that in normal large follicles. However, the result of enzyme-linked immunosorbent assay showed no significant difference in the decreasing in concentration of inhibin α subunit in cystic follicular fluid compared with the control (P>0.05). In this study, we explored the effects of FSH on betaglycan expression in granulosa cells in vitro. As expected, a significant increase in the expressions of betaglycan mRNA and protein in granulosa cells was observed in response to exogenous FSH (30 ng/ml) (P<0.05) compared with the control. Consequently, this study provides evidence that the expressions of inhibin α subunit and betaglycan are inferior in cystic follicles, and this may be caused by the decrease in FSH in the presence of a cystic follicle.

Low-dose gold nanoparticles exert subtle endocrine-modulating effects on the ovarian steroidogenic pathway ex vivo independent of oxidative stress

Gold nanoparticles (GNPs) have gained considerable attention for application in science and industry. However, the untoward effects of such particles on female fertility remain unclear. The objectives of this study were to (1) examine the effects of 10-nm GNPs on progesterone and estradiol-17β accumulation by rat ovaries ex vivo and (2) to identify the locus/loci whereby GNPs modulate steroidogenesis via multiple-reference gene quantitative real-time RT-PCR. Regression analyses indicated a positive relationship between both Star (p < 0.05, r(2) = 0.278) and Cyp11a1 (p < 0.001, r(2) = 0.366) expression and P4 accumulation upon exposure to 1.43 × 10(6) GNPs/mL. Additional analyses showed that E2 accumulation was positively associated with Hsd3b1 (p < 0.05, r(2) = 0.181) and Cyp17a1 (p < 0.01, r(2) = 0.301) expression upon exposure to 1.43 × 1(3) and 1.43 × 10(9) GNPs/mL, respectively. These results suggest a subtle treatment-dependent impact of low-dose GNPs on the relationship between progesterone or estradiol-17β and specific steroidogenic target genes, independent of oxidative stress or inhibin.

Transcriptome profiling of the theca interna in transition from small to large antral ovarian follicles

The theca interna layer of the ovarian follicle forms during the antral stage of follicle development and lies adjacent to and directly outside the follicular basal lamina. It supplies androgens and communicates with the granulosa cells and the oocyte by extracellular signaling. To better understand developmental changes in the theca interna, we undertook transcriptome profiling of the theca interna from small (3-5 mm, n = 10) and large (9-12 mm, n = 5) healthy antral bovine follicles, representing a calculated >7-fold increase in the amount of thecal tissue. Principal Component Analysis and hierarchical classification of the signal intensity plots for the arrays showed no clustering of the theca interna samples into groups depending on follicle size or subcategories of small follicles. From the over 23,000 probe sets analysed, only 76 were differentially expressed between large and small healthy follicles. Some of the differentially expressed genes were associated with processes such as myoblast differentiation, protein ubiquitination, nitric oxide and transforming growth factor β signaling. The most significant pathway affected from our analyses was found to be Wnt signaling, which was suppressed in large follicles via down-regulation of WNT2B and up-regulation of the inhibitor FRZB. These changes in the transcriptional profile could have been due to changes in cellular function or alternatively since the theca interna is composed of a number of different cell types it could have been due to any systematic change in the volume density of any particular cell type. However, our study suggests that the transcriptional profile of the theca interna is relatively stable during antral follicle development unlike that of granulosa cells observed previously. Thus both the cellular composition and cellular behavior of the theca interna and its contribution to follicular development appear to be relatively constant throughout the follicle growth phase examined.

Effects of granulosa cells on steroidogenesis, proliferation and apoptosis of stromal cells and theca cells derived from the goat ovary

The aim of this study was to investigate the effect of granulosa cells from small antral follicles on steroidogenesis, proliferation and apoptosis of goat ovarian stromal and theca cells in vitro. Using Transwell co-culture system, we evaluated androgen production, LH responsiveness, cell proliferation and apoptosis and some molecular expression regarding steroidogenic enzyme and apoptosis-related genes in stromal and theca cells. The results indicated that the co-culture with granulosa cells increased steroidogenesis, LH responsiveness and bcl-2 gene expression as well as decreased apoptotic bax and bad expressions in stromal and theca cells. Thus, granulosa cells had a capacity of promoting steroidogenesis in stromal cell and LH responsiveness in cortical stromal cells, maintaining steroidogenesis in theca cells, inhibiting apoptosis of cortical stromal cells and improving anti-apoptotic abilities of stromal and theca cells.

Culture of bovine ovarian follicle wall sections maintained the highly estrogenic profile under basal and chemically defined conditions

Follicle cultures reproduce in vitro the functional features observed in vivo. In a search for an ideal model, we cultured bovine antral follicle wall sections (FWS) in a serum-free defined medium (DM) known to induce 17β-estradiol (E2) production, and in a nondefined medium (NDM) containing serum. Follicles were sectioned and cultured in NDM or DM for 24 or 48 h. Morphological features were determined by light microscopy. Gene expression of steroidogenic enzymes and follicle-stimulating hormone (FSH) receptor were determined by RT-PCR; progesterone (P4) and E2 concentrations in the media were measured by radioimmunoassay. DM, but not NDM, maintained an FWS morphology in vitro that was similar to fresh tissue. DM also induced an increase in the expression of all steroidogenic enzymes, except FSH receptor, but NDM did not. In both DM and NDM, there was a gradual increase in P4 throughout the culture period; however, P4 concentration was significantly higher in NDM. In both media, E2 concentration was increased at 24 h, followed by a decrease at 48 h. The E2:P4 ratio was higher in DM than in NDM. These results suggest that DM maintains morphological structure, upregulates the expression of steroidogenic enzyme genes, and maintains steroid production with a high E2:P4 ratio in FWS cultures.

SGTA: a new player in the molecular co-chaperone game

Small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA) is a steroid receptor molecular co-chaperone that may substantially influence hormone action and, consequently, hormone-mediated carcinogenesis. To date, published studies describe SGTA as a protein that is potentially critical in a range of biological processes, including viral infection, cell division, mitosis, and cell cycle checkpoint activation. SGTA interacts with the molecular chaperones, heat shock protein 70 (HSP70) and HSP90, and with steroid receptor complexes, including those containing the androgen receptor. Steroid receptors are critical for maintaining cell growth and differentiation in hormonally regulated tissues, such as male and female reproductive tissues, and also play a role in disease states involving these tissues. There is growing evidence that, through its interactions with chaperones and steroid receptors, SGTA may be a key player in the pathogenesis of hormonally influenced disease states, including prostate cancer and polycystic ovary syndrome. Research into the function of SGTA has been conducted in several model organisms and cell types, with these studies showing that SGTA functionality is cell-specific and tissue-specific. However, very few studies have been replicated in multiple cell types or experimental systems. Although a broad range of functions have been attributed to SGTA, there is a serious lack of mechanistic information to describe how SGTA acts. In this review, published evidence linking SGTA with hormonally regulated disease states is summarized and discussed, highlighting the need for future research to more clearly define the biological function(s) of this potentially important co-chaperone.

Engineered multilayer ovarian tissue that secretes sex steroids and peptide hormones in response to gonadotropins

Although hormone replacement therapy is an option for the loss of ovarian function, hormone delivery through pharmacological means results in various clinical complications. The present study was designed to deliver sex steroids by a functional construct fabricated using encapsulation techniques. Theca and granulosa cells isolated from ovaries of 21-day old rats were encapsulated in multilayer alginate microcapsules to recapitulate the native follicular structure. Cells encapsulated in two other schemes were used as controls to assess the importance of the multilayer structure. The endocrine functions of the encapsulated cells were assessed in vitro for a period of 30 days. Encapsulated cells showed sustained viability during long-term in vitro culture with those encapsulated in multilayer capsules secreting significantly higher and sustained concentrations of 17 β-estradiol (E(2)) than the two other encapsulation schemes (p < 0.05, n = 6) in response to follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In addition, cells in the multilayer microcapsules also secreted activin and inhibin in vitro. In contrast, when granulosa and theca cells were cultured in 2D culture, progesterone (P(4)) secretion increased while E(2) secretion decreased over a 30-day period. In summary, we have designed a multilayer engineered ovarian tissue that secretes sex steroids and peptide hormones and responds to gonadotropins, thus demonstrating the ability to recapitulate native ovarian structure ex vivo.

Immunohistochemical localization of inhibin/activin subunits in the wild ground squirrel (Citellus dauricus Brandt) ovary

The intraovarian function of gonadally produced inhibin and activin has been extensively studied in experimental models for decades, yet their presence and function have been rarely reported in wild rodents. With our seasonal breeding model, the wild ground squirrel, we aimed to investigate the possible roles of these peptides in the seasonal folliculogenesis. Immunohistochemical staining and Western blotting have been used to detect the cellular localization and expression patterns of inhibin/activin subunits (α, β(A) and β(B)). In the breeding season ovary, all three subunits were present in granulosa cells, theca cells of antral follicles and interstitial cells, with the strongest immunostaining in granulosa cells. Following ovulation, the corpora lutea become a major site of inhibin/activin synthesis. In the nonbreeding season ovary, inhibin/activin α and β(A) subunits were weakly immunopositive in granulosa cells of early stage follicles, while β(B) subunit was undetectable. The expression level of inhibin/activin subunit proteins were generally higher in the ovaries of the breeding season, and then decreased to a relatively low level during the nonbreeding season. The dynamic expression of inhibin/activin subunits indicated that they might play important paracrine and/or autocrine roles during the seasonal folliculogenesis of the wild ground squirrel.