Ulipristal (UPA) effects on rat ovaries: Unraveling follicle dynamics, ovulation inhibition, and safety implications for prolonged use

Ulipristal (UPA), a selective progesterone receptor modulator, has both agonistic and antagonistic effects on progesterone receptors. UPA suppresses ovulation by inhibiting the luteinizing hormone (LH) surge from the pituitary gland; however, the direct effect of UPA on ovarian tissue remains poorly studied. In the present study, we examined the effects of UPA on the ovaries of rats. Rats were treated for 28 days with UPA, and the effects of UPA on ovarian tissue were examined histologically and the expression of antioxidant genes and cell death markers were also investigated. UPA treatment increased the number of primordial follicles at each treatment group, primordial follicles increased at all dose levels, but the size/magnitude of the effect decreased with the increasing dose. The number of primary and antral follicles tended to increase with increasing UPA levels. Furthermore, the decrease in primary follicle number could be attributed to the exhaustion of follicles, but the examination of proliferation markers, oxidative stress markers, and cell death markers revealed no remarkable toxic effects on ovarian tissues. These results suggest that UPA treatment promotes follicle development at each stage but inhibits ovulation by suppressing the LH surge, resulting in an increase in atretic follicles or unruptured luteinized cysts. These results suggest that UPA may not have both toxic effects on the ovary and a direct local effect on ovarian follicles, but we should be careful about the effects of prolonged UPA treatment in patients with uterine fibroids on their future fecundity.

Progesterone modulates HSD11B1-mediated cortisol production in luteinized bovine granulosa cells

Progesterone (P4) and cortisol production increase in luteinized granulosa cells (LGCs) during the periovulatory period, but their interaction is not well established. Therefore, we investigated their interaction in cultured bovine LGCs. Granulosa cells were collected from follicles of 2-5 mm in diameter and cultured in DMEM/F-12 supplemented with 10% fetal calf serum for up to 14 days. P4 production and the expression of steroidogenic acute regulatory protein (STAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 3β-hydroxysteroid dehydrogenase type 1 (HSD3B1) rapidly increased until day 10 and remained high thereafter. No de novo production of cortisol from P4 was detected during the culture period. The expression of 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which converts cortisone to cortisol, increased dramatically on day two, decreased until day 8, and remained relatively constant. To investigate how P4 and cortisol influence each other's production, LGCs were treated with trilostane (a P4 synthesis inhibitor), nomegestrol acetate (NA, a synthetic progestogen), P4, and/or cortisol for 24 h on days 6 and 12 of culture. Trilostane suppressed P4 and STAR expression while elevating HSD11B1 and HSD3B1 expression and cortisol production. Concomitant treatment with NA or P4 dose-dependently decreased cortisol production and HSD11B1 and HSD3B1 expression but elevated STAR expression in both days 6 and 12. Conversely, cortisol treatment increased HSD11B1 and HSD3B1 expression and decreased STAR expression without influencing P4 production. These results indicate that progestogens suppress cortisol production by modulating HSD11B1 expression and that progestogens and cortisol differentially regulate STAR, HSD3B1, and HSD11B1 expression in bovine LGCs.

Spheroid formation and luteinization of granulosa cells of felids in a long-term 3D culture

In the present study, granulosa cells (GCs) from domestic cats and Persian leopard were cultured and characterized from selected days. The culture period was divided into two phases: maintenance, which lasted for 7 days, and luteinization, which followed for up to 11 days. Luteinization was performed on ultra-low attachment plates, supporting the formation of spheroids in a medium supplemented with insulin, forskolin, and luteinizing hormone (LH). GCs of domestic cat produced estradiol (E2) and progesterone (P4) during the maintenance phase. The gene expressions of some proteins involved in steroidogenesis were stable (STAR, HSD3B1) or decreased over time (CYP11A1, HSD17B1, CYP17A1, and CYP19A1), which was similar to the expressions of gonatropin receptors (LHCGR and FSHR). During the luteinization phase, P4 concentration significantly increased (P < 0.05), and E2, in contrast to the proliferation phase, was below detection range. The expression of genes of proteins involved in steroidogenesis (STAR, CYP11A1, HSD3B1, HSD17B1, CYP17A1, and CYP19A1) and of gonadotropin receptors (LHCGR and FSHR) significantly increased during the luteinization period, but some expressions exhibited a decrease at the end of the phase (LHCGR, FSHR, HSD17B1, CYP19A1). The morphology of the luteinized GCs of domestic cat resembled large luteal cells and had numerous vacuole-like structures. Also, the GCs of Persian leopard underwent luteinization, shown by increasing P4 production and HSD3B1 expression. This study confirms that GCs from felids can be luteinized in a 3D spheroid system which can be a basis for further studies on luteal cell function of felids. Additionally, we could show that the domestic cat can serve as a model species for establishing cell culture methods which can be transferred to other felids.

Lactate-induced effects on bovine granulosa cells are mediated via PKA signaling

L-lactate acts as a signaling molecule in bovine granulosa cells (GCs). The initiated alterations depend on the transport of L-lactate into the cells via monocarboxylate transporters. In the present study, we further elucidated the intracellular actions of L-lactate and tested whether the PKA signaling pathway is involved. Therefore, we treated cultured bovine GCs with L-lactate and PKA inhibitors H-89 and KT5720, and with an activator of PKA, 6-Bnz-cAMP. L-lactate treatment resulted in decreased estradiol production and downregulation of CYP19A1, FSHR, and LHCGR as well as in the upregulation of the markers of early luteinization PTX3, RGS2, and VNN2. These specific L-lactate effects were almost completely abolished by pre-treatment of the GCs with both inhibitors of PKA signaling. In addition, also the L-lactate-induced upregulation of LDHA and of the monocarboxylate transporters SLC16A1 and SLC16A7 was abolished after PKA inhibition. An activation of the PKA with 6-Bnz-cAMP revealed similar effects on the gene expression like L-lactate alone. In summary, the presented data demonstrate that L-lactate-induced effects on GCs are mediated via PKA signaling thus supporting the role of L-lactate as signaling molecule during the folliculo-luteal transition.

Transcriptome analysis reveals transforming growth factor-β1 prevents extracellular matrix degradation and cell adhesion during the follicular-luteal transition in cows

Ovarian angiogenesis is an extremely rapid process that occurs during the transition from follicle to corpus luteum (CL) and is crucial for reproduction. It is regulated by numerous factors including transforming growth factor-β1 (TGFB1). However, the regulatory mechanism of TGFB1 in ovarian angiogenesis is not fully understood. To address this, in this study we obtained high-throughput transcriptome analysis (RNA-seq) data from bovine luteinizing follicular cells cultured in a system mimicking angiogenesis and treated with TGFB1, and identified 455 differentially expressed genes (DEGs). Quantitative real-time PCR results confirmed the differential expression patterns of the 12 selected genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified that the MAPK and ErbB pathways, cell adhesion molecules (CAMs), and extracellular matrix (ECM)-receptor interactions may play pivotal roles in TGFB1-mediated inhibition of CL angiogenesis. TGFB1 phosphorylated ERK1/2 (MAPK1/3) and Akt, indicating that these pathways may play an important role in the regulation of angiogenesis. Several genes with specific functions in cell adhesion and ECM degradation were identified among the DEGs. In particular, TGFB1-induced upregulation of syndecan-1 (SDC1) and collagen type I alpha 1 chain (COL1A1) expression may contribute to the deposition of type I collagen in luteinizing follicular cells. These results indicate that TGFB1 inhibits cell adhesion and ECM degradation processes involving ERK1/2, ErbB, and PI3K/Akt signaling pathways, and leads to inhibition of angiogenesis during the follicular-luteal transition. Our results further reveal the molecular mechanisms underlying the actions of TGFB1 in early luteinization.

Ultrasound-guided aspiration of dominant follicles (≥25 mm) followed by luteinization and progesterone production during the estrous cycle in mares

The present study was designed to evaluate luteinization rates subsequent to aspiration of dominant follicles (≥25 mm) in the absence of a functional CL (progesterone <1 ng/mL) and characterize the temporal changes in plasma concentrations of progesterone following aspiration-induced luteinization during the estrous cycle in mares. A total of 29 estrous cycles involving 15 mares in a cross-over design were randomly assigned to five groups: 1) ASP-F≥25 mm (n = 6; follicle aspiration 25-29 mm), 2) ASP-F≥30 mm (n = 6; follicle aspiration 30-34 mm), 3) ASP-F≥35 mm (n = 6; follicle aspiration 35-40 mm), 4) ASP-F≥40 (n = 6; follicle aspiration ≥40), and 5) Control (n = 5; spontaneous ovulation or no follicle aspiration). Subsequent to ovulation (Day 0), PGF was administered to all groups on Day 5, blood samples were collected daily and aspiration of the dominant follicle was done using ultrasound-guided transvaginal follicle needle puncture. Among the follicle aspirations groups 25-29, 30-34, 35-39, and ≥40 mm, the luteinization rates were not different (P > 0.05) at 83, 67, 83, and 100%, respectively. Correspondingly, progesterone concentrations increased (>2 ng/mL) by approximately 6, 7, 5, and 4 d after aspiration, respectively, which were delayed (P < 0.05) in the 25-29 and 30-34 mm follicle aspiration groups compared to 2 d after ovulation in the control group. Thereafter, progesterone reached maximal concentrations (10-11 ng/mL) as averaged over all aspiration groups but were lower (P < 0.05) compared to the mean maximal concentration (18 ng/mL) in the control group. Subsequently, there was a decrease in progesterone concentrations (<2 ng/mL) in response to luteolysis, which was delayed (P < 0.05) in the aspiration groups over Days 16-20 compared to Day 15 in the control group. Despite this discrepancy, the mean length of the interovulatory intervals were not different (P > 0.05) among groups on Day 23. Thus, the present study provided novel information that the luteinization rate is relatively high (83%) and consistent following aspiration of dominant follicles (≥25 mm) in the absence of a functional CL and that the increase in progesterone reaches sustainable progestational concentrations (≥2 ng/mL) in accord with the length of the estrous cycle that may potentially support development and maintenance of early pregnancy in recipient mares involved in an embryo transfer program.

Multispecies study: low-dose tributyltin impairs ovarian theca cell cholesterol homeostasis through the RXR pathway in five mammalian species including humans

Tributyltin (TBT), an organotin chemical used as a catalyst and biocide, can stimulate cholesterol efflux in non-steroidogenic cells. Since cholesterol is the first limiting step for sex hormone production, we hypothesized that TBT disrupts intracellular cholesterol transport and impairs steroidogenesis in ovarian theca cells. We investigated TBT's effect on cholesterol trafficking, luteinization, and steroidogenesis in theca cells of five species (human, sheep, cow, pig, and mice). Primary theca cells were exposed to an environmentally relevant dose of TBT (1 or 10 ng/ml) and/or retinoid X receptor (RXR) antagonist. The expression of RXRα in sheep theca cells was knocked down using shRNA. Steroidogenic enzymes, cholesterol transport factors, and nuclear receptors were measured by RT-qPCR and Western blotting, and intracellular cholesterol, progesterone, and testosterone secretion by ELISA. TBT upregulated StAR and ABCA1 in ovine cells, and SREBF1 mRNA in theca cells. TBT also reduced intracellular cholesterol and upregulated ABCA1 protein expression but did not alter testosterone or progesterone production. RXR antagonist and RXRα knockdown demonstrates that TBT's effect is partially through RXR. TBT's effect on ABCA1 and StAR expression was recapitulated in all five species. TBT, at an environmentally relevant dose, stimulates theca cell cholesterol extracellular efflux via the RXR pathway, triggers a compensatory upregulation of StAR that regulates cholesterol transfer into the mitochondria and SREBF1 for de novo cholesterol synthesis. Similar results were obtained in all five species evaluated (human, sheep, cow, pig, and mice) and are supportive of TBT's conserved mechanism of action across mammalian species.

Effects of gonadotropin-releasing hormone agonist on human chorionic gonadotropin activity in granulosa cells of immature female rats

Although the expression of gonadotropin-releasing hormone (GnRH) in the ovaries is well established, its physiological role remains unknown. The aim of this study was to determine whether ovarian GnRH mediates the actions of human chorionic gonadotropin (hCG) in the granulosa cells of immature female rats. Follicular growth was induced by administration of pregnant mare serum gonadotropin (PMSG, 15 IU/0.15 ml) on day 25 after birth, and hCG (20 IU/0.2 ml) was administered on day 27 revealing the increase of plasma progesterone level. Primary cultures of granulosa cells were established from large follicles 2 days after PMSG treatment. Progesterone synthesis was augmented by hCG in a dose-dependent manner. Annexin A5 (ANXA5), a biomarker of GnRH, was expressed in the granulosa-luteal cells after hCG treatment, as shown by immunohistochemistry, suggesting that hCG treatment induced GnRH action. The GnRH mRNA level was increased by hCG, and treatment with GnRH agonist (GnRHa) increased ANXA5 mRNA levels in the primary cultures of granulosa cells. Concomitant incubation of GnRH (10^–7 M) or GnRHa (fertirelin acetate, 10^–8 M) with hCG suppressed progesterone synthesis during a 3 h incubation period. The mRNA expression of luteinizing hormone receptor (LHR) and follicle-stimulating hormone receptor (FSHR) was synergistically stimulated and suppressed by hCG and GnRHa, respectively. GnRHa stimulated p21 expression, and GnRHa and hCG synergistically reduced the mRNA expression levels of p27 and FOXO1. These data suggest that GnRH induced by LH may have a role for the LH-mediated luteinization of granulosa cells. In addition, ANXA5 may be involved in GnRH action. GnRH-ANXA5 would be an important mechanism in cell differentiation.

Changes in gene expression of histone modification enzymes in rat granulosa cells undergoing luteinization during ovulation

Background

The ovulatory LH surge rapidly alters the expression of steroidogenesis-related genes such as steroidogenic acute regulatory protein (StAR) in granulosa cells (GCs) undergoing luteinization. We recently reported that histone modifications contribute to these changes. Histone modifications are regulated by a variety of histone modification enzymes. This study investigated the changes in gene expression of histone modification enzymes in rat GCs undergoing luteinization after the induction of ovulation. The extracellular regulated kinase (ERK)-1/2 is a mediator in the intracellular signaling pathway stimulated by the ovulatory LH surge and regulates the expression of a number of genes in GCs. We further investigated whether ERK-1/2 is involved in the regulation of the histone modification at the StAR promoter region in GCs undergoing luteinization.

Results

GCs were obtained from rats treated with equine chorionic gonadotropin (CG) before (0 h) and after human (h) CG injection. The expressions of 84 genes regulating histone modifications or DNA methylation were measured using a PCR array. Five genes (HDAC4, HDAC10, EZH2, SETDB2, and CIITA) were identified as histone acetylation- or histone methylation-related genes, and were significantly altered after hCG injection. None of the genes were related to DNA methylation. mRNA levels of EZH2, SETDB2, HDAC4, and HDAC10 decreased and CIITA mRNA levels increased 4 or 12 h after hCG injection.

GCs isolated after eCG injection were incubated with hCG for 4 h to induce luteinization. StAR mRNA levels were significantly increased by hCG accompanied by the increase in H3K4me3 of the StAR promoter region. StAR mRNA expression was inhibited by the ERK inhibitor with the significant decrease of H3K4me3. These results suggest that hCG increases StAR gene expression through the ERK-1/2-mediated signaling which is also associated with histone modification of the promoter region.

Conclusions

Gene expressions of histone modification enzymes change in GCs undergoing luteinization after ovulation induction. This change may play important roles in regulating the expression of various genes during the early stage of luteinization, which may be critical for the subsequent corpus luteum formation.

Effect of Lipopolysaccharide on Progesterone Production during Luteinization of Granulosa and Theca cells In Vitro

The aim of this study is to examine the effect of lipopolysaccharide (LPS) on progesterone production during luteinization of granulosa and theca cells isolated from bovine large follicles. Granulosa and theca cells isolated from large follicles of bovine ovaries were exposed to LPS under appropriate hormone conditions in vitro. Progesterone (P4) production in theca cells, but not granulosa cells, was decreased by long-term exposure of LPS. Long-term exposure of LPS suppressed the gene expression of luteinizing hormone receptor in theca cells. Although long-term exposure of LPS did not affect the expression of steroidogenic acute regulatory protein (StAR) and 3β-hydroxy-steroid dehydrogenase (3β-HSD) genes, it did inhibit the protein expression of StAR and 3β-HSD in theca cells. These findings suggest that theca cells, rather than granulosa cells, are susceptible to LPS during luteinization and that LPS inhibits P4 production by decreasing protein levels of StAR during luteinization of theca cells.

The Impact of Serum Progesterone Levels on the Results of In Vitro Fertilization Treatments: A Literature Review

The aim of this review is to analyze the relationship between preovulatory progesterone (P) rise and in vitro fertilization (IVF) pregnancy outcomes. It also investigates the sources and effects of rises in progesterone levels, including the underlying mechanisms and potential strategies in preventing its elevation during ovarian stimulation. Progesterone is produced in the early follicular phase in the adrenal gland, which shifts toward the ovaries prior to ovulation. Several factors contribute to the etiology of P level increase including the number of multiple follicles, the overdose of gonadotropins and poor ovarian response. Nowadays, the influence of the preovulatory P rise on IVF outcome remains controversial. Several authors have failed to demonstrate any negative impact, while others reported a detrimental effect associated with the rise of P. It seems that P rise (1.5 ng/ml or 4.77 nmol/l) may have deleterious effects on endometrial receptivity, namely, accelerating the endometrial maturation process that subsequently narrows the period for implantation and thus decreases pregnancy rates. Recent studies have proposed different cutoffs according to the ovarian response, which may be a little high in patients with high response in relation to those of normal response or low response. To prevent a P rise, it might be preferable to use milder stimulation protocols, earlier trigger of ovulation, cryopreservation of all embryos and transfer in the natural cycle.

Establishment and validation of a model for non-luteinized human mural granulosa cell culture

Cell culture techniques of human mural granulosa cells (MGCs) serve as a major in vitro tool. However, the use of luteinized MGCs has major limitations due to their luteinized state. Our aim was to establish a standardized protocol for the culture of MGCs as a model for different stages of folliculogenesis. We showed that early-non-luteinized, preovulatory-non-luteinized and luteal-MGCs have distinct gene expression pattern. After 4 days of incubation of luteinized-MGCs, ovulatory genes mRNA's achieve expression levels similar to the early non-luteinized follicles. FSH stimulation for 48 h of these 4 days cultured MGCs showed ovulatory genes mRNA's expression similar to the pre-ovulatory non-luteinized follicles. These FSH-stimulated cells responded to hCG stimulation in a pattern similar to the response of pre-ovulatory follicles. This novel model may provide a standardized research tool for delineation of the molecular processes occurring during the latter stages of follicular development in the human ovary.

Molecular mechanisms of luteinization

Dynamic changes in steroidogenesis occur in ovarian granulosa cells during ovulation after the LH surge. The ovulatory LH surge induces rapid up-regulation of steroidogenic acute regulatory (StAR) protein and rapid down-regulation of aromatase (Cyp19a1) in granulosa cells undergoing luteinization during ovulation. These rapid changes in StAR and Cyp19a1 gene expression after the LH surge efficiently facilitate progesterone production, which plays a crucial role in ovulation and the following luteinization. Recently, it has become clear that epigenetic regulation such as histone modifications and DNA methylation play a key role in gene expression through the chromatin remodeling of the promoter region. This study reports the in vivo evidence that epigenetic mechanisms including histone modifications, DNA methylation and chromatin remodeling are involved in the rapid changes of StAR and Cyp19a1 gene expression in granulosa cells undergoing luteinization during ovulation.

Endocrine and local control of the primate corpus luteum

The primate corpus luteum is a transient endocrine gland that differentiates from the ovulatory follicle midway through the ovarian (menstrual) cycle. Its formation and limited lifespan is critical for fertility, as luteal-derived progesterone is the essential steroid hormone required for embryo implantation and maintenance of intra-uterine pregnancy until the placenta develops. It is well-established that LH and the LH-like hormone, CG, are the vital luteotropic hormones during the menstrual cycle and early pregnancy, respectively. Recent advances, particularly through genome analyses and cellular studies, increased our understanding of various local factors and cellular processes associated with the development, maintenance and repression of the corpus luteum. These include paracrine or autocrine factors associated with angiogenesis (e.g., VEGF), and that mediate LH/CG actions (e.g., progesterone), or counteract luteotropic effects (i.e., local luteolysis; e.g., PGF2α). However, areas of mystery and controversy remain, particularly regarding the signals and events that initiate luteal regression in the non-fecund cycle. Novel approaches capable of gene "knockdown" or amplification", in vivo as well as in vitro, should identify novel or underappreciated gene products that are regulated by or modulate LH/CG actions to control the functional lifespan of the primate corpus luteum. Further advances in our understanding of luteal physiology will help to improve or control fertility for purposes ranging from preservation of endangered primate species to designing novel ovary-based contraceptives and treating ovarian disorders in women.

Induction of Ski Protein Expression upon Luteinization in Rat Granulosa Cells

Ski protein is implicated in proliferation/differentiation in a variety of cells. We had previously reported that Ski protein is present in granulosa cells of atretic follicles, but not in preovulatory follicles, suggesting that Ski has a role in apoptosis of granulosa cells. The alternative fate of granulosa cells other than apoptosis is to differentiate to luteal cells; however, it is unknown whether Ski is expressed and has a role in granulosa cells undergoing luteinization. Thus, the aim of the present study was to locate Ski protein in the rat ovary during luteinizationto predict the possible role of Ski. In order to examine the expression pattern of Ski protein along with the progress of luteinization, follicular growth was induced by administration of equine chorionic gonadtropin to immature female rats, and luteinization was induced by human chorionic gonadtropin treatment to mimic luteinizing hormone (LH) surge. While no Ski-positive granulosa cells were present in preovulatory follicle, Ski protein expression was induced in response to LH surge, and was maintained after the formation of the corpus luteum (CL). Though Ski protein is absent in granulosa cells of preovulatory follicle, its mRNA (c-Ski) was expressed and the level was unchanged even after LH surge. Taken together, these results demonstrated that Ski protein expression is induced in granulosa cells upon luteinization, and suggests that its expression is regulated post-transcriptionally.