The human corpus luteum: which cells have progesterone receptors?

Short communication: Photoperiod impacts ovarian extracellular matrix and metabolic gene expression in Siberian hamsters

Ovarian cyclicity is variable in adult Siberian hamsters (Phodopus sungorus), who respond to long breeding season photoperiods with follicle development and ovulation, while short photoperiods typical of the non-breeding season induce gonadal atrophy. Recent RNAseq results identified ovarian matrix components and regulators of metabolism as differentially regulated by photoperiod; however, the impact of photoperiod across a full cycle of ovarian regression and recrudescence had not been explored for additional regulators of ovarian metabolism and extracellular matrix components. We hypothesized that matrix and metabolism-related genes would be expressed differentially across photoperiods that mimic breeding and non-breeding season daylengths. Hamsters were housed in one of four photoperiod groups: long day (16 h of light per day: 8 h of dark; LD, controls), short day regressed (8 L:16D; SD, regressed), and females exposed to SD then transferred to LD to stimulate return of ovarian function for 2 (early recrudescence), or 8 (late recrudescence) weeks. Plasma leptin concentrations along with expression of ovarian versican and liver-receptor homolog-1/Nr582 mRNA decreased in SD compared to LD and late recrudescence, while vimentin mRNA expression peaked in early and late recrudescence. Ovarian expression of fibronectin and extracellular matrix protein-1 was low in LD ovaries and increased in regressed and recrudescing groups. Expression of hyaluronidase-2, nectin-2, liver-X receptors-α and-β, and adiponectin mRNA peaked in late recrudescence, with no changes noted for adiponectin receptor-1 and -2. The results offer a first look at the parallels between expression of these genes and the dynamic remodeling that occurs during ovarian regression and recrudescence.

Female Reproductive Systems: Hormone Dependence and Receptor Expression

The female reproductive system which consists of the ovaries, uterus (myometrium, endometrium), Fallopian tubes, cervix and vagina is exquisitely sensitive to the actions of steroid hormones. The ovaries play a key role in the synthesis of bioactive steroids (oestrogens, androgens, progestins) that act both within the tissue (intracrine/paracrine) as well as on other reproductive organs following release into the blood stream (endocrine action). Sex steroid receptors encoded by the oestrogen (ESR1, ESR2), progesterone (PR) and androgen (AR) receptor genes, which are members of the superfamily of ligand activated transcription factors are widely expressed within these tissues. These receptors play critical role(s) in regulation of cell proliferation, ovulation, endometrial receptivity, myometrial cell function and inflammatory cell infiltration. Our understanding of their importance has been informed by studies on human tissues and cells, which have employed immunohistochemistry as well as a wide range of molecular and genetic methods to identify which processes are dependent steroid ligand activation. The development of mice with targeted deletions of each of these receptors has provided complementary data that has extended our appreciation of cell-cell interactions in the fine tuning of reproductive tissue function. This large body of work has formed the basis of new and improved therapeutics to treat conditions such as infertility.

BMP6 increases CD68 expression by up-regulating CTGF expression in human granulosa-lutein cells

Bone morphogenetic protein 6 (BMP6) and connective tissue growth factor (CTGF) are critical growth factors required for normal follicular development and luteal function. Cluster of Differentiation 68 (CD68) is an intraovarian marker of macrophages that plays an important role in modulating the physiological regression of the corpus luteum. The aim of this study was to investigate the effect of BMP6 on the expression of CTGF and the subsequent increase in CD68 expression as well as its underlying mechanisms. Primary and immortalized (SVOG) human granulosa cells obtained from infertile women undergoing in vitro fertilization treatment were used as cell models to conduct the in vitro experiments. Our results showed that BMP6 treatment significantly increased the expression levels of CTGF and CD68. Using BMP type I receptor inhibitors (dorsomorphin, DMH-1 and SB431542), we demonstrated that both activin receptor-like kinase (ALK)2 and ALK3 are involved in BMP6-induced stimulatory effects on the expression of CTGF and CD68. Additionally, SMAD4-knock down reversed the BMP6-induced up-regulation of CTGF and CD68, indicating that the canonical SMAD signaling pathway is required for these effects. Moreover, CTGF-knock down abolished the BMP6-induced up-regulation of CD68 expression. These findings indicate that intrafollicular CTGF mediates BMP6-induced increases in CD68 expression through the ALK2/ALK3-mediated SMAD-dependent signaling pathway.

Immunohistochemical localization of progesterone receptors alpha (PRA) in ovary of the pseudopregnant rabbit

Progesterone plays an important role in the reproductive function and follicular development in mammals. The aim of the present study was to examine the localization of progesterone receptor alpha (PRA) in ovary of pseudopregnant rabbit by immunohistochemical methods. Samples were collected from 14 h. to 18 days of pseudopregnancy. At the first stage of pseudopregnancy (14 h.), the rabbit ovary showed moderate immunostaining of PRA in the granulosa cells and theca interna cells of preovulatory follicle and in the stroma cells. At the middle stage of pseudopregnancy (3-7 days), the rabbit ovary showed strong immunostaining of PRA in ovarian surface epithelial cells, follicular cells of the primary follicle, granulosa cells and theca interna cells of the growing and antral follicles. Moderate immunoexpression of PRA were observed in the large lutein cells and endothelial cells of the corpus haemorrhagicum and corpus luteum and in the stroma cells. At the end of pseudopregnancy (18 days) strong PRA reactions were detected in the small lutein cells of the regressed corpus luteum. Moderate to strong PRA immuno-expression were observed in the proliferated theca interna cells of the atretic antral follicles. The atretic large lutein cells of the regressed corpus luteum showed negative immunostaining for PRA. This study showed that the PRA positive small lutein cells of the regressed corpus luteum and the PRA positive proliferated theca interna cells of the atretic antral follicles were transformed into PRA positive interstitial gland cells. In conclusion, the present study had described the distribution of PRA in the ovary of pseudopregnant rabbit, which is not discussed before in the available literature. It also gives more information about follicular dynamic, formation and origin of interstitial glands, mechanism of ovulation, formation and regression of the corpus luteum.

Daytime Variation in Serum Progesterone During the Mid-Luteal Phase in Women Undergoing In Vitro Fertilization Treatment

OBJECTIVE

To investigate whether mid-luteal serum progesterone (P₄) exhibits significant fluctuations during a 12-h daytime period in women undergoing in vitro fertilization (IVF) and to explore whether the extent of these fluctuations could impact the interpretation of luteal progesterone levels in a clinical setting.

DESIGN

Explorative pilot study.

SETTING

Public hospital-based fertility unit.

PATIENTS

Ten women undergoing IVF treatment.

INTERVENTION

Seven days after oocyte pick-up, patients underwent frequent repeated blood sampling (every 60 min for 12 h and during two of these hours, every 15 min). Serum samples were analyzed for progesterone, estradiol, and luteinizing hormone (LH).

MAIN OUTCOME MEASURES

Daytime fluctuations in s-progesterone and s-estradiol.

RESULTS

There was a significant positive correlation between median P₄ levels and the magnitude of P₄ variations-women with median P₄ < 60 nmol/l had clinically stable P₄ levels throughout the day, while patients with median P₄ > 250 nmol/l exhibited periodic P₄ peaks of several hundred nanomoles per liter. These endogenous P₄ fluctuations were observed irrespective of the type of stimulation protocol or mode of triggering of final oocyte maturation and despite the fact that LH was under the detection limit at the time of measurement. Simultaneously, large fluctuations were seen in s-estradiol.

CONCLUSION

Monitoring of early to mid-luteal P₄ levels in IVF cycles may be valuable in the planning of individualized luteal phase support in the attempt to increase reproductive outcomes. The prerequisite for luteal phase monitoring is, however, that the validity of a single measured P₄ value is reliable. We show for the first time, that a single P₄ measurement in the low progesterone patient quite accurately reflects the corpus luteum function and that the measurement can be used to detect IVF patients with a need of additional exogenous luteal P₄ administration.

Adrenomedullin2 (ADM2)/intermedin (IMD) in rat ovary: changes in estrous cycle and pregnancy and its role in ovulation and steroidogenesis

Adrenomedullin2 (ADM2) is reported to facilitate embryo implantation and placental development. Therefore, the current study was undertaken to identify if ADM2 has a functional role in ovary to facilitate its reproductive actions. This study shows that the expression of ADM2 is differentially regulated in rat estrous cycle and that ADM2 increases the synthesis and secretion of 17beta-estradiol accompanied with an increase in the expression of steroidogenic factor 1 (Sf1), estrogen receptor Esr1, and enzymes involved in steroidogenesis in equine chorionic gonadotropin (eCG)-treated rat ovaries. In addition, inhibition of endogenous ADM2 function in eCG-treated immature rats caused impaired ovulation. Furthermore, the mRNA expression of Adm2 and receptor activity modifying protein 3 is higher in the ovary on Day 18 compared to nonpregnant and pregnant rats on Day 22. ADM2-like immunoreactivity is localized in granulosa cells, blood vessels, oocytes, cumulous oophorus, and corpus luteum of pregnant ovaries, suggesting a potential role for ADM2 in the ovary. This is supported by the presence of ADM2-like immunoreactivity in the corpus luteum during pregnancy and a decline in aromatase immunoreactivity in corpus luteum on Day 9 of gestation in rats infused with ADM2 antagonist during implantation and decidualization phase. Taken together, this study suggests a potential involvement of ADM2 in the rat ovary in regulating synthesis of estradiol to support ovulation and facilitate efficient implantation and placental development for a successful pregnancy.

Progesterone receptor in the vascular endothelium triggers physiological uterine permeability preimplantation

Vascular permeability is frequently associated with inflammation and is triggered by a cohort of secreted permeability factors such as vascular endothelial growth factor (VEGF). Here, we show that the physiological vascular permeability that precedes implantation is directly controlled by progesterone receptor (PR) and is independent of VEGF. Global or endothelial-specific deletion of PR blocks physiological vascular permeability in the uterus, whereas misexpression of PR in the endothelium of other organs results in ectopic vascular leakage. Integration of an endothelial genome-wide transcriptional profile with chromatin immunoprecipitation sequencing revealed that PR induces an NR4A1 (Nur77/TR3)-dependent transcriptional program that broadly regulates vascular permeability in response to progesterone. Silencing of NR4A1 blocks PR-mediated permeability responses, indicating a direct link between PR and NR4A1. This program triggers concurrent suppression of several junctional proteins and leads to an effective, timely, and venous-specific regulation of vascular barrier function that is critical for embryo implantation.

FSH up-regulates angiogenic factors in luteal cells of buffaloes

Follicle-stimulating hormone has been widely used to induce superovulation in buffaloes and cows and usually triggers functional and morphologic alterations in the corpus luteum (CL). Several studies have shown that FSH is involved in regulating vascular development and that adequate angiogenesis is essential for normal luteal development. Angiogenesis is regulated by many growth factors, of which vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) have an established central role. Therefore, we have used a combination of in vitro and in vivo studies to assess the effects of FSH on the expression of VEGF and FGF2 and their receptors in buffalo luteal cells. The in vivo model consisted of 12 buffalo cows, divided into control (n = 6) and superovulated (n = 6) groups, and CL samples were collected on day 6 after ovulation. In this model, we analyzed the gene and protein expression of FGF2 and its receptors and the protein expression of VEGFA systems with the use of real-time PCR, Western blot analysis, and immunohistochemistry. In the in vitro model, granulosa cells were collected from small follicles (diameter, 4-6 mm) of buffaloes and cultured for 4 d in serum-free medium with or without FSH (10 ng/mL). To induce in vitro luteinization, LH (250 ng/mL) and fetal bovine serum (10%) were added to the medium, and granulosa cells were maintained in culture for 4 d more. The progesterone concentration in the medium was measured at days 4, 5, and 8 after the beginning of cell culture. Cells were collected at day 8 and subjected to real-time PCR, Western blot analysis, and immunofluorescence for assessment of the expression of FGF2, VEGF, and their receptors. To address the percentage of steroidogenic and growth factor-expressing cells in the culture, flow cytometry was performed. We observed that in superovulated buffalo CL, the FGF2 system mRNA expression was decreased even as protein expression was increased and that the VEGF protein was increased (P < 0.05). In vitro experiments with granulosa cells showed an increase in the mRNA expression of VEGF and FGF2 and its receptors 1 and 2 and protein expression of VEGF, kinase insert domain receptor, FGF receptor 2, and FGF receptor 3 in cells treated with FSH (P < 0.05), in contrast to the in vivo experiments. Moreover, the progesterone production by FSH-treated cells was elevated compared with untreated cells (P < 0.05). Our findings indicate that VEGF, FGF2, and their receptors were differentially regulated by FSH in vitro and in vivo in buffalo luteal cells, which points toward a role of CL environment in modulating cellular answers to gonadotropins.

Selective suppression of endothelial cytokine production by progesterone receptor

Steroid hormones are well-recognized suppressors of the inflammatory response, however, their cell- and tissue-specific effects in the regulation of inflammation are far less understood, particularly for the sex-related steroids. To determine the contribution of progesterone in the endothelium, we have characterized and validated an in vitro culture system in which human umbilical vein endothelial cells constitutively express human progesterone receptor (PR). Using next generation RNA-sequencing, we identified a selective group of cytokines that are suppressed by progesterone both under physiological conditions and during pathological activation by lipopolysaccharide. In particular, IL-6, IL-8, CXCL2/3, and CXCL1 were found to be direct targets of PR, as determined by ChIP-sequencing. Regulation of these cytokines by progesterone was also confirmed by bead-based multiplex cytokine assays and quantitative PCR. These findings provide a novel role for PR in the direct regulation of cytokine levels secreted by the endothelium. They also suggest that progesterone-PR signaling in the endothelium directly impacts leukocyte trafficking in PR-expressing tissues.

Physiology and Endocrinology Symposium: role of immune cells in the corpus luteum

The immune system is essential for optimal function of the reproductive system. The corpus luteum (CL) is an endocrine organ that secretes progesterone, which is responsible for regulating the length of the estrous cycle, and for the establishment and maintenance of pregnancy in mammals. This paper reviews literature that addresses 2 areas; i) how immune cells are recruited to the CL, and ii) how immune cells communicate with luteal cells to affect the formation, development, and regression of the CL. Immune cells, primarily recruited to the ovulatory follicle from lymphoid organs after the LH surge, facilitate ovulation and populate the developing CL. During the luteal phase, changes in the population of macrophages, eosinophils, neutrophils, and T lymphocytes occur at critical functional stages of the CL. In addition to their role in facilitating ovulation, immune cells may have an important role in luteal function. Evidence shows that cytokines secreted by immune cells modulate both luteotropic and luteolytic processes. However, the decision to pursue either function may depend on the environment provided by luteal cells. It is suggested that understanding the role immune cells play could lead to identification of new strategies to improve fertility in dairy cattle and other species.

New approaches to making the microenvironment of the female reproductive tract hostile to HIV

The studies presented in this review explore three distinct areas with potential for inhibiting HIV infection in women. Based on emerging information from the physiology, endocrinology and immunology of the female reproductive tract (FRT), we propose unique 'works in progress' for protecting women from HIV. Various aspects of FRT immunity are suppressed by estradiol during the menstrual cycle, making women more susceptible to HIV infection. By engineering commensal Lactobacillus to secrete the anti-HIV molecule Elafin as estradiol levels increase, women could be protected from HIV infection. Selective estrogen response modifiers enhance barrier integrity and enhance secretion of protective anti-HIV molecules. Finally, understanding the interactions and regulation of FRT endogenous antimicrobials, proteases, antiproteases, etc., all of which are under hormonal control, will open new avenues to therapeutic manipulation of the FRT mucosal microenvironment. By seeking new alternatives to preventing HIV infection in women, we may finally disrupt the HIV pandemic.

Expression of mRNA and proteins for GnRH I and II and their receptors in primate corpus luteum during menstrual cycle

The differential expression of mRNA and protein of GnRH I, II and their receptors (RI and RII) in the monkey corpus luteum (CL) were measured during different stages of the luteal phase of the menstrual cycle as an initial step towards considering the role and regulation of GnRH (I and II) system during luteinization and luteolysis in primates. RT-PCR confirmed the sequence identity of PCR products and real time PCR quantified specific mRNA expressions. Proteins were localized by immunohistochemistry (IHC). Changes in mRNA expression patterns of GnRH I and II (increased) and GnRH RII (decreased) were maximal at mid-late to late stages, that is, at CL regression, where as GnRH RI was low during the entire luteal phase. However, RT-PCR and IHC studies confirmed the presence of GnRH RI at both mRNA and protein levels, respectively. IHC results showed the presence of GnRH I, II and their receptors in steroidogenic cells (granulose-luteal cells and thecal-luteal cells) across the luteal phase. Hence, GnRH I and II systems may have a role on both luteinization (from early to mid stages of CL) and luteolysis (from mid-late to very-late stages of CL). These novel findings suggest that monkey luteal GnRH system may have a role in fertility regulation in paracrine and/or autocrine manner.

HCG up-regulates hypoxia inducible factor-1 alpha in luteinized granulosa cells: implications for the hormonal regulation of vascular endothelial growth factor A in the human corpus luteum

Vascular endothelial growth factor (VEGF)-dependent angiogenesis is essential for normal luteal development. Although it is believed that hypoxia is the primary inducer of VEGF, in the corpus luteum it is up-regulated by human chorionic gonadotrophin (hCG). As hypoxia-inducible factor (HIF)1A has been shown to regulate VEGFA under ligand-stimulated conditions, we hypothesized that the effect of hCG on luteal VEGFA was mediated through HIF1A. We studied the effect of hCG on VEGFA and HIF1A expression in human luteinized granulosa cells in vitro and in human corpora lutea in vivo. HCG up-regulated VEGFA (P < 0.05) and HIF1A (P < 0.001) in vitro and VEGFA (P < 0.05) and HIF1A (P < 0.05) in vivo. There was a correlation between HIF1A and VEGFA in vivo (P < 0.005) and in vitro (P < 0.05). Nuclear HIF1A in granulosa-lutein cells was highest during luteal formation and absent from the fully functional corpus luteum (P < 0.05). Both VEGFA (P < 0.001) and HIF1A (P < 0.01) were up-regulated by dibutyryl-cAMP, through a PKA pathway. Hypoxia increased VEGFA (P < 0.001) and HIF1A (P < 0.05) expression and hCG further augmented VEGFA (P < 0.001) and HIF1A (P < 0.01) under hypoxic conditions. However, progesterone increased hCG-stimulated VEGFA but had no effect on HIF1A expression. The expression of HIF1A is therefore hormonally regulated in luteal cells in vitro and in vivo and may regulate VEGFA expression under normoxic and hypoxic conditions. However, the differential effects of progesterone suggest that not all regulation of VEGFA is associated with an up-regulation of HIF1A.

Role of luteal glucocorticoid metabolism during maternal recognition of pregnancy in women

The human corpus luteum (hCL) is an active, transient, and dynamic endocrine gland. It will experience extensive tissue and vascular remodeling followed by 1) demise of the whole gland without any apparent scarring or 2) maintenance of structural and functional integrity dependent on conceptus-derived human chorionic gonadotropin (hCG). Because cortisol has well-characterized roles in tissue remodeling and repair, we hypothesized that it may have a role in controlling luteal dissolution during luteolysis and would be locally produced toward the end of the luteal cycle. Glucocorticoid-metabolizing enzymes [11beta-hydroxysteroid dehydrogenase (11betaHSD) types 1 and 2] and the glucocorticoid receptor (GR) were assessed in hCL and cultures of luteinized granulosa cells (LGC) using immunofluorescence and quantitative RT-PCR. Furthermore, the effect of cortisol on steroidogenic cell survival and fibroblast-like cell activity was explored in vitro. The hCL expressed 11betaHSD isoenzymes in LGC and nuclear GR in several cell types. hCG up-regulated the expression and activity of 11betaHSD type 1 (P < 0.05) and down-regulated type 2 enzyme (P < 0.05) in vitro and tended to do the same in vivo. Cortisol increased the survival of LGC treated with RU486 (P < 0.05) and suppressed the activity of a proteolytic enzyme associated with luteolysis in fibroblast-like cells (P < 0.05). Our results suggest that, rather than during luteolysis, it is luteal rescue with hCG that is associated with increased local cortisol generation by 11betaHSD type 1. Locally generated cortisol may therefore act on the hCL through GR to have a luteotropic role in the regulation of luteal tissue remodeling during maternal recognition of pregnancy.

In vitro evidence suggests activin-A may promote tissue remodeling associated with human luteolysis

Luteolysis in women is associated with an up-regulation of the expression and activity of matrix metalloproteinase-2 (MMP-2), which is inhibited by human chorionic gonadotropin (hCG) during maternal recognition of pregnancy. Because the primary source of MMP-2 is fibroblasts that do not express LH/hCG receptors, we aimed to investigate the regulation of MMP-2. Women with regular cycles having hysterectomy for nonmalignant conditions and women undergoing oocyte retrieval for assisted conception were used in this current study. Novel primary cultures and cocultures of luteinized granulosa cells and fibroblast-like cells in conjunction with human corpora lutea from different stages of the luteal phase were used to investigate the role of activin-A in the corpus luteum. The effect of hCG, activin-A, and follistatin on MMP-2 activity and expression was assessed by gelatin zymography and quantitative RT-PCR in primary cell cultures. Confirmation of signaling pathways involved in the activation of MMP-2 was assessed by immunofluorescence, RT-PCR, and quantitative RT-PCR. In primary cell culture, steroidogenic cells secrete activin-A and its inhibitors, inhibin-A and follistatin. Follistatin expression is up-regulated by hCG (P < 0.05). The fibroblast-like cells producing MMP-2 have the machinery for activin reception, expressing both type I and type II activin receptors and Smad proteins. Activin-A up-regulated both activity and expression of MMP-2 in fibroblast-like cells (P < 0.05). This activity was inhibited in cocultures of luteinized granulosa cells and fibroblast-like cells in the presence of hCG (P < 0.05) or follistatin (P < 0.01). Activin-A is an excellent candidate for an effector molecule in human luteolysis whose paracrine action is inhibited during maternal recognition of pregnancy.

Binding of progesterone to cell surfaces of human granulosa-lutein cells

Progesterone is produced by granulosa cells under the influence of luteinizing hormone. Nuclear progesterone receptors have been found in rat granulosa cells. Human granulosa-lutein cells rapidly respond to progesterone with an increase in intracellular calcium suggesting the existence of a nongenomic mechanism. This study was conducted to determine whether binding of progesterone to granulosa cells could occur at the membrane. Granulosa cells were obtained from an in vitro fertilization program and examined immunohistochemically with an antiserum to membrane progesterone receptors. Approximately 14-70% of freshly harvested or cultured granulosa cells of six patients showed a positive reaction to the antiserum, limited to the cell membrane. Western blot analysis of homogenates of granulosa cells and a granulosa cell tumour confirmed the presence of progesterone receptors A, B and C and low amounts of a putative membrane receptor. These results demonstrate that the plasma membranes of human granulosa cells possess binding components for progesterone which may be involved in its nongenomic mechanism of action.

Innate and adaptive immunity in female genital tract: cellular responses and interactions

The mucosal immune system in the female reproductive tract (FRT) has evolved to meet the unique requirements of dealing with sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and the immunologically distinct fetus. Analysis of the FRT indicates that the key cells of the innate and adaptive immune systems are present and functionally responsive to antigens. Acting through Toll-like receptors in the Fallopian tubes, uterus, cervix, and in the vagina, epithelial cells, macrophages, natural killer cells, and neutrophils confer protection through the production of chemokines and cytokines, which recruit and activate immune cells, as well as bactericidal and virucidal agents, which confer protection at times when adaptive immunity is downregulated by sex hormones to meet the constraints of procreation. The overall goal of this paper is to define the innate immune system in the FRT and, where possible, to define the regulatory influences that occur during the menstrual cycle that contribute to protection from and susceptibility to potential pathogens. By understanding the nature of this protection and the ways in which innate and adaptive immunity interact, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Connective tissue growth factor expression in the human corpus luteum: paracrine regulation by human chorionic gonadotropin

CONTEXT

The molecular mechanisms of luteolysis and its inhibition during maternal recognition of pregnancy remain unclear.

OBJECTIVE

The objective of this study was to investigate the differential regulation of connective tissue growth factor (CTGF) expression in human corpora lutea using in vivo and in vitro models.

DESIGN

Corpora lutea from different stages of the luteal phase and after luteal rescue with human chorionic gonadotropin (hCG) were studied. Primary cultures and cocultures of luteinized granulosa cells and luteal fibroblast-like cells were performed.

SETTING

This study was performed at the research center of a university teaching hospital.

PATIENTS

Women with regular cycles having hysterectomy for nonmalignant conditions and women undergoing oocyte collection for assisted conception were studied.

INTERVENTIONS

CTGF localization was determined by in situ hybridization, and expression by quantitative RT-PCR.

OUTCOMES

The outcome measures were the effect of hCG on the expression and localization of CTGF mRNA in human corpora lutea and the effect of hCG on CTGF expression in primary cultures of luteinized granulosa cells and luteal fibroblast-like cells.

RESULTS

Luteal rescue reduced CTGF expression compared with that in the late luteal phase (P < 0.05). CTGF expression was localized to fibroblast-like cells and endothelial cells of larger blood vessels, not to steroidogenic cells. The expression of CTGF by fibroblast-like cells in vitro was not regulated by hCG. When cocultured with luteinized granulosa cells, fibroblast-like cell CTGF expression was inhibited by hCG (P < 0.001). This effect was independent of stimulated progesterone concentrations and was not blocked by follistatin or indomethacin. Both IL-1alpha (P < 0.05) and cAMP (P < 0.001) inhibited CTGF expression in fibroblast-like cells.

CONCLUSIONS

These results provide evidence for negative regulation of CTGF by hCG during luteal rescue mediated by paracrine signals.

Difference in progesterone-receptor isoforms ratio between early and late first-trimester human trophoblast is associated with differential cell invasion and matrix metalloproteinase 2 expression

The expression profile of the progesterone-receptor isoforms and progesterone regulation of matrix metalloproteinase 2 (MMP2) were investigated in early and late first-trimester trophoblast cells. Human trophoblast cells were obtained from legal abortions (6-12 wk of gestation). Purity of 95-98% was verified using immunohistochemistry with specific antibodies. Evaluation of cell count was performed with XTT Reagent kit, and invasion was tested using Matrigel invasion assay. Zymography was used to detect proteolytic activity, and Western blot immunoassay was used to study protein concentration. Gene expression of PGRB, PGR, and MMP2 was studied using reverse transcription-polymerase chain reaction with the housekeeping gene GAPDH used for normalization. Promoter activity was determined using luciferase reporter assay. Differential progesterone-receptor profile was documented with the dominance of PGRB in early trophoblast and the dominance of PGRA in late trophoblast. This differential profile is compatible with the inverse effect of progesterone on the two cell populations, decreasing invasion and gelatinase expression in the early first-trimester trophoblast and increasing invasion and gelatinase expression in the late first-trimester trophoblast. A decrease in MMP2 promoter activity in early trophoblast cells exposed to progesterone suggests that MMP2 expression is regulated by progesterone at the transcriptional level as well. Early trophoblast cells transfected with expressing vector for PGR encoding PGRA revealed less MMP2 activity and reversal of its response to progesterone similar to the effect observed in late trophoblast cells.

The effect of human chorionic gonadotrophin on the expression of progesterone receptors in human luteal cells in vivo and in vitro

The human corpus luteum expresses genomic progesterone receptors (PRs) suggesting that progesterone may have an autocrine or paracrine role in luteal function. We hypothesised that the reduction in luteal PR reported in the late-luteal phase augmented progesterone withdrawal and had a role in luteolysis. We therefore tested the hypothesis that luteal rescue with human chorionic gonadotrophin (hCG) would maintain PR expression. PR was immunolocalised to different cell types in human corpora lutea (n = 35) from different stages of the luteal phase and after luteal rescue with exogenous hCG. There was no change in the staining intensity of theca-lutein cell or stromal cell PR throughout the luteal phase or after luteal rescue. In the late-luteal phase, granulosa-lutein cell PR immunostaining was reduced (P < 0.05) but the trend to reduction was also seen after luteal rescue with hCG (P = 0.055). To further investigate the effect of hCG on granulosa-lutein cell PR expression, an in vitro model system of cultured human luteinised granulosa cells was studied. Cells were cultured for 12–13 days exposed to different patterns of hCG and aminoglutethamide to manipulate progesterone secretion (P < 0.0001). Expression of PR A/B and PR B isoforms was examined by quantitative real-time RT-PCR. PR A/B mRNA was lower (P < 0.05) after 11–13 days of culture than after 7 days of culture. This reduction could not be prevented by hCG in the presence (P < 0.05) or absence (P < 0.05) of stimulated progesterone secretion. The expression of PR B mRNA showed a similar pattern (P = 0.054). Simulated early pregnancy in vivo and hCG treatment of luteinised granulosa cells in vitro did not appear to prevent the down-regulation of PR seen during luteolysis.

Non-genomic action of estradiol and progesterone on cytosolic calcium concentrations in primary cultures of human granulosa-lutein cells

BACKGROUND

The present study examined whether the sex steroids, estradiol and progesterone, could alter cytoplasmic calcium concentrations ([Ca(2+)](cyt)) in human granulosa-lutein cells.

METHODS

Human granulosa cells were obtained at the time of oocyte retrieval for IVF and cultured for 3-7 days. Cells were loaded with Fura-2 AM and changes in [Ca(2+)](cyt) of single cells were studied using a dynamic digital Ca(2+) imaging system.

RESULTS

Both estradiol and progesterone stimulated elevations of [Ca(2+)](cyt) in Ca(2+)-containing medium within seconds of exposure of the granulosa-lutein cells to the steroid, but only estradiol caused an increase in [Ca(2+)](cyt) in Ca(2+)-free medium. Both ICI-182780 and RU 486 stimulated [Ca(2+)](cyt) increases and inhibited the effects of estradiol and progesterone, respectively. Tamoxifen also induced transient increases in [Ca(2+)](cyt) concentrations but inhibited the effects of both estradiol and progesterone. The inhibitory effects of tamoxifen, ICI-182780 and RU 4486 on [Ca(2+)](cyt) responses to estradiol and progesterone could be reversed with higher concentrations of estradiol and progesterone, respectively. The [Ca(2+)](cyt) effects induced with tamoxifen could not be eliminated by prior treatment with RU 486 or ICI-182780.

CONCLUSION

These results provide strong evidence that both estradiol and progesterone as well as the steroid antagonists, tamoxifen, RU 486 and ICI-182780, can act on human granulosa-lutein cells through a non-genomic mechanism.