Corpus Luteum In Early Pregnancy Research Articles

Clustered microRNAs: The molecular mechanism supporting the maintenance of luteal function during early pregnancy.

MicroRNAs (miRNAs) are recognized as the important regulators of ovarian function. However, little is known about the hormonal regulation of miRNA expression and the role of the specific miRNA-mRNA interactions in corpus luteum. Therefore, the present study was undertaken to determine: (a) the expression of miRNAs in the corpus luteum in early pregnancy vs regression; (b) the effect of conceptus and uterine signals in the expression of selected miRNAs; and (c) the role of specific miRNA-mRNA interactions in the molecular changes and secretory function of the corpus luteum in the pig. The results showed that the majority of miRNAs differentially expressed in the corpus luteum in early pregnancy vs regression belong to independent clusters (eg, miR-99b, miR-532), which are highly conserved among different animal species. The main conceptus signal in the pig (17β-estradiol) elevated the luteal expression of the miR-99b cluster and lowered the expression of NR4A1 and AKR1C1, the genes involved in corpus luteum regression. Furthermore, the delivery of miR-99b cluster mimics to luteal tissue concomitantly decreased NR4A1 and AKR1C1 expression and enhanced progesterone secretion. The present study demonstrated that conceptus signals can support the maintenance of luteal function during pregnancy by clustered miRNA-stimulated pathways, governing the expression of genes involved in luteal regression.

Luteal Lipids Regulate Progesterone Production and May Modulate Immune Cell Function During the Estrous Cycle and Pregnancy.

Although the corpus luteum (CL) contains high concentrations of lipid in the form of steroid hormone precursors and prostaglandins, little is known about the abundance or function of other luteal lipid mediators. To address this, 79 lipid mediators were measured in bovine CL, using ultra performance liquid chromatography-tandem mass spectrometry. CL from estrous cycle days 4, 11, and 18 were compared and, separately, CL from days 18 of the estrous cycle and pregnancy were compared. Twenty-three lipids increased as the estrous cycle progressed (P < 0.05), with nine increasing between days 4 and 11 and fourteen increasing between days 4 and 18. Overall, this indicated a general upregulation of lipid mediator synthesis as the estrous cycle progressed, including increases in oxylipins and endocannabinoids. Only 15-KETE was less abundant in the CL of early pregnancy (P < 0.05), with a tendency (P < 0.10) for four others to be less abundant. Notably, 15-KETE also increased between estrous cycle days 4 and 18. Ingenuity Pathway Analysis (IPA, Qiagen) indicated that functions associated with differentially abundant lipids during the estrous cycle included leukocyte activation, cell migration, and cell proliferation. To investigate changes in CL during maternal recognition of pregnancy, this lipid dataset was integrated with a published dataset from mRNA profiling during maternal recognition of pregnancy. This analysis indicated that lipids and mRNA that changed during maternal recognition of pregnancy may regulate some of the same functions, including immune cell chemotaxis and cell-cell communication. To assess effects of these lipid mediators, luteal cells were cultured with 5-KETE or 15-KETE. One ng/mL 5-KETE reduced luteal progesterone on day 1 of culture, only in the absence of luteinizing hormone (LH), while 1 ng/mL 15-KETE induced progesterone only in the presence of LH (10 ng/mL). On day 7 of culture, 0.1 ng/mL 15-KETE reduced prostaglandin (PG)F2A-induced inhibition of LH-stimulated progesterone production, while 1 ng/mL 15-KETE did not have this effect. Overall, these data suggest a role for lipid mediators during luteal development and early pregnancy, as regulators of steroidogenesis, immune cell activation and function, intracellular signaling, and cell survival and death.

18. Absence of the corpus luteum in early pregnancy increases the risk of preeclampsia

Introduction Assisted reproductive technology is associated with an increased risk of preeclampsia, but the reasons are poorly understood. The corpus luteum (CL) produces multiple vasoactive hormones in the first trimester of pregnancy which could affect initial placentation and later development of preeclampsia. Hypothesis We hypothesized that non-physiologic states present in in-vitro fertilization (IVF) such as absence of the CL could increase the risk of preeclampsia. Methods 892 infertile women were enrolled in this prospective cohort study. Four categories based on CL status were defined: (1) absence of the CL; (2) single CL; (3) multiple CL associated with ovulation induction; (4) multiple CL associated with controlled ovarian stimulation for IVF and fresh embryo transfer. Analysis focused on singleton pregnancies conceived with autologous oocytes resulting in live birth (n = 683). Multivariable logistic regression was used to control for covariates. Results Compared with conceptions occurring in the presence of one CL, conceptions occurring in the absence of a CL were associated with a higher incidence of preeclampsia (12.8% vs 4.8%, P = 0.02) and preeclampsia with severe features (9.6% vs 1.4%, P = Discussion Among singleton pregnancies after infertility resulting in live birth, those conceived in the absence of a CL were at increased risk for development of preeclampsia and preeclampsia with severe features.

Management of Ruptured Corpus Luteum with Hemoperitoneum in Early Pregnancy – a Case Report

SUMMARY – Rupture of the corpus luteum is a frequent condition in women of reproductive age. Because of abdominal pain accompanied by hemoperitoneum, ruptured corpus luteum can easily be confused with ectopic pregnancy. The management of ruptured corpus luteum depends on the symptoms and laboratory findings, and can be just observation but laparoscopy or urgent laparotomy may also be needed. Although rare, hemoperitoneum following rupture of corpus luteum in early pregnancy should always be considered in the diagnostic process. We present a patient that was admitted to our department with amenorrhea, positive ßhCG and acute abdomen. Emergency laparoscopy was performed but no ectopic pregnancy was found, just blood, coagula and a ruptured corpus luteum. The day after the surgery, intrauterine pregnancy was found on ultrasound and the pregnancy ended with term delivery.

Repertoire of noncoding RNAs in corpus luteum of early pregnancy in buffalo (Bubalus bubalis).

Aim:The present study was designed to identify other noncoding RNAs (ncRNAs) in the corpus luteum (CL) during early pregnancy in buffalo.Materials and Methods:For this study, CL (n=2) from two buffalo gravid uteri, obtained from the slaughter house, was transported to laboratory after snap freezing in liquid nitrogen (−196°C). The stage of pregnancy was determined by measuring the crown-rump region of the fetus. This was followed by isolation of RNA and deep sequencing. Post-deep sequencing, the obtained reads were checked and aligned against various ncRNA databases (GtRNA, RFAM, and deep guide). Various parameters, namely, frequency of specific ncRNAs, length, mismatch, and genomic location target in several model species were deciphered.Results:Frequency of piwi-interacting RNAs (piwi-RNAs), having target location in rodents and human genomes, were significantly higher compared to other piwi-RNAs and ncRNAs. Ribosomal RNAs (rRNAs) deduced had nucleotides (nts) ranging from 17 to 50 nts, but the occurrence of small length rRNAs was more than lengthier fragments. The target on 16S rRNA species confirms the conservation of 16S rRNA across species. With respect to transfer RNA (tRNA), the abundantly occurring tRNAs were unique with no duplication. Small nucleolar RNAs (snoRNAs), identified in this study, showed a strong tendency for coding box C/D snoRNAs in comparison to H/ACA snoRNAs. Regulatory and evolutionary implications of these identified ncRNAs are yet to be delineated in many species, including buffaloes.Conclusion:This is the first report of identification of other ncRNAs in CL of early pregnancy in buffalo.

Regulation of endothelial permeability in the primate corpora lutea: implications for ovarian hyperstimulation syndrome.

In a developing human corpus luteum, a closely regulated cellular communication system exists between the luteal steroidogenic cells and endothelial cells. This system guaranties the vascularization process during luteal formation. The process is combined with rapid release of large amounts of progesterone into the bloodstream. The regulation of endothelial proliferation and permeability by LH and human chorionic gonadotropin (hCG) is integral to this process. On the cellular level, endothelial permeability is regulated by intercellular junctions, such as adherens junctions (AJ) and tight junctions (TJ), which act as zipper-like structures between interacting endothelial cells. Several cell junctional proteins are localized to the corpus luteum, including Occludin, Nectin 2, Claudin 1, and Claudin 5, as well as, vascular endothelial (VE)-Cadherin. It has been assumed that regulation of AJ- and TJ-proteins is of particular importance for permeability, and accordingly, for the functionality of the corpus luteum in early pregnancy, because treatment with hCG induces downregulation of juntional proteins in the luteal vessels. The effect of hCG on the adhesive molecules is mediated by VE growth factor (VEGF). On a functional level, the hCG-dependent and VEGF-mediated decrease in junctional proteins causes a decrease in the density of cell-cell closure and, accordingly, an increase in endothelial permeability. In doing so, the different junctional proteins are not only directly influenced by VEGF but also interact among themselves and influence each other reciprocally. Disturbances in this strictly, regulated interactions may explain the development of pathologies with increased vascular permeability, such as the ovarian hyperstimulation syndrome.

Regulation of Endothelial Permeability in the Corpus Luteum: A Review of the Literature.

The development of the human corpus luteum (yellow body) is dictated by a strictly controlled system of mutually communicating cells, the luteal steroid hormone-producing cells and endothelial cells. This cell-to-cell communication facilitates control of neoangiogenesis which is a prerequisite for the development of the corpus luteum and its function, the rapid release of large amounts of progesterone into the blood-vascular system. Preconditions for this process are the hormonal regulation of endothelial cell proliferation as well as of vascular permeability through LH and hCG. The morphological correlates of endothelial permeability are cell-to-cell adhesion molecules such as adherens junctions (AJ) and tight junctions (TJ) that open and close the gaps between mutually interacting, neighbouring endothelial cells like a "zip fastener". Various types of cell adhesion molecules have been detected in the corpus luteum such as occludin, claudin 1 and claudin 5 as well as VE-cadherin. It may be assumed that the regulation of AJ and TJ proteins is of particular importance for the permeability and thus for the function of the corpus luteum in early pregnancy since hCG treatment leads to a down-regulation of cell adhesion molecules in the luteal vessels. This effect is apparently mediated by VEGF. From a functional point of view, the hCG-dependent and VEGF-mediated down-regulation of cell adhesion molecules leads to a reduced transmissibility of cell-to-cell contacts and thus to an increased endothelial permeability. In this process the various cell adhesion molecules are not only directly regulated by VEGF but they also mutually interact and thus influence one another.

Effects of steroid ablation and progestin replacement on the transcriptome of the primate corpus luteum during simulated early pregnancy

Previous microarray analyses indicated that a portion of the transcriptome in the macaque corpus luteum (CL) of the menstrual cycle was regulated indirectly by luteinizing hormone via the local actions of steroid hormones, notably progesterone (P). The current study was designed to investigate this concept in the CL of early pregnancy by analyzing chorionic gonadotrophin (CG)-regulated genes that are dependent versus independent of local steroid action. Exogenous human chorionic gonadotropin treatment simulating early pregnancy (SEP) began on Day 9 of the luteal phase in female rhesus monkeys with and without concurrent administration of the 3-β-hydroxysteroid dehydrogenase inhibitor trilostane (TRL) with or without the synthetic progestin R5020. Compared with SEP treatment alone, TRL altered 50 mRNA transcripts on Day 10, rising to 95 on Day 15 (P<0.05, ≥2-fold change in gene expression). Steroid-sensitive genes were validated; notably effects of steroid ablation and P replacement varied by day. Expression of some genes previously identified as P-regulated in the macaque CL during the menstrual cycle were not significantly altered by steroid ablation and P replacement during CG exposure in SEP. These data indicate that the majority of CG-regulated luteal transcripts are differentially expressed independently of local steroid actions. However, the steroid-regulated genes in the macaque CL may be essential during early pregnancy, based on previous reports that TRL treatment initiates premature structural regression of the CL during SEP. These data reinforce the concept that the structure, function and regulation of the rescued CL in early pregnancy differs from the CL of the menstrual cycle in primates.

LH Stimulates the Phosphorylation of Key Components of the Wnt Signaling Pathway in Bovine Steroidogenic Luteal Cells.

Luteinizing hormone (LH) stimulates progesterone synthesis in bovine corpus luteum by a cAMP/Protein kinase A (PKA)-dependent mechanism. Previous studies demonstrate that the actions of LH may intersect with glycogen synthase kinase-3B (GSK3B) and β-catenin, key components of the Wnt signaling pathway. In the canonical Wnt signaling pathway, Wnt signaling inactivates GSK3B which prevents the degradation of β-catenin and allows it to translocate to the nucleus to activate target gene expression. Evidence in fibroblast cell lines indicates that PKA can stabilize or activate β-catenin by phosphorylating β-catenin on C-terminus serine residues (S552 and S675). It is not known, however, whether LH regulates the phosphorylation and subcellular localization of β-catenin. In the present study, we tested the hypothesis that LH stimulates the phosphorylation of GSK3B(S9) and β-catenin(S552/S675). Consistent with a role for Wnt signaling components in the action of LH, we hypothesized that the LH-induced increases the phosphorylation of these proteins would be present in perinuclear and nuclear compartments in bovine luteal cells. Bovine corpora lutea of early pregnancy were obtained at slaughter. Isolated steroidogenic luteal cells were prepared and treated with LH or activators of PKA. Western blot revealed that LH (100ng/ml) rapidly stimulated the phosphorylation of GSK3B(S9) and β-catenin(S552/S675); maximal responses were attained within 5 min and phosphorylation responses were maintained for up to 60 min without alterations in the levels of GSK3B or β-catenin. Additionally, LH treatment (1-100 ng/ml for 15 min) stimulated concentration-dependent increases in the phosphorylation of these proteins. The effects of LH were mimicked by 8-Br-cAMP and forskolin, agents that increase PKA activity in luteal cells. Immunofluorescence showed that LH treatment for 15 min increased the phosphorylation of GSK3B(S9) predominantly in the Golgi apparatus and nucleus. Since the Golgi and nuclear fraction are closely associated, an experiment was performed to determine whether the Golgi has role in progesterone production in response to LH. Pretreatment of luteal cells with up to 5 μg/ml brefeldin A (BFA, which interferes with anterograde transport from the endoplasmic reticulum to the Golgi apparatus, and disrupts the Golgi) for 2h had no effect on progesterone production in response to LH treatment (100 ng/ml, 4 h). Immunofluorescence studies also showed that LH treatment for 15 min increased levels of phosphorylated β-catenin (S552 and S675) in the nucleus of luteal cells. Subcellular fractionation and Western blot analysis confirmed findings that the LH-induced increases in phospho-S552 β-catenin were predominately localized to the nucleus of luteal cells. The LH-induced increases in phospho-S675 β-catenin were observed in both cytosolic and nuclear factions of bovine luteal cells. Our findings indicate that in response to LH, key components of the Wnt signaling pathway are phosphorylated and localized to the nucleus. The presence of phosphorylated GSK3B in the Golgi apparatus imply a role in protein trafficking, but our studies with BFA rule out a role in the acute steroidogenic response to LH. The nuclear localization of phosphorylated β-catenin in response to LH may contribute to PKA- and β-catenin-regulated gene expression in steroidogenic luteal cells. Supported by the VA, USDA and the Olson Center for Women's Health.

Life or Death Decisions in the Corpus Luteum

The corpus luteum (CL) is an ephemeral endocrine organ. During its lifespan, it undergoes a period of extremely rapid growth that involves hypertrophy, proliferation and differentiation of the steroidogenic cells, as well as extensive angiogenesis. The growth phase is followed by a period in which remodelling of the tissue ceases, but it engages in unparalleled production of steroids, resulting in extraordinarily high metabolic activity within the tissue. It is during this stage that a critical juncture occurs. In the non-fertile cycle, uterine release of prostaglandin (PG)F(2α) initiates a cascade of events that result in rapid loss of steroidogenesis and destruction of the luteal tissue. Alternatively, if a viable embryo is present, signals are produced that result in rescue of the CL. This review article summarizes the major concepts related to the fate of the CL, with particular focus on recent insights into the mechanisms associated with the ability of PGF(2α) to bring about complete luteolysis. It has become clear that the achievement of luteolysis depends on repeated exposure to PGF(2α) and involves coordinated actions of heterogeneous cell types within the CL. Together, these components of the process bring about not only the loss in progesterone production, but also the rapid demise of the structure itself.

Luteal Microenvironment Directs Resident T Lymphocyte Function in Cows1

The corpus luteum (CL) is a transient endocrine organ composed of a heterogeneous mixture of cells. Functional interactions exist between peripheral T cells and luteal cells in vitro; however, the precise role of resident T cells (RTC) remains unknown. The goals of the present study were to isolate RTC from within the CL and determine if alteration of luteal function resulted in changes in RTC phenotypes. Functional lymphocyte phenotypes identified in the bovine CL by using quantitative flow cytometric analysis were clearly different from those in the peripheral circulation. The proportion of CD8(+) RTC was greater than CD4(+) RTC. These proportions were opposite in peripheral blood. The proportion of γδ(+) lymphocytes was not different in the CL compared to that in peripheral blood nor was it altered during luteal regression. There was a significant increase in CD8αα(+) and γδ(+)CD8αα(+) RTC during luteal regression. The proportion of FOXP3(+) lymphocytes in the CL was greater than that isolated from peripheral blood, and this proportion of lymphocytes was dramatically reduced by induction of luteolysis. Within the CL of early pregnancy, there was an increase in the CD8αβ(+) and γδ(+)CD8αβ(+) populations compared to those in the CL of nonpregnant animals. Based on these data, we concluded that the functional state of the CL creates a microenvironment that regulates the recruitment of or differentiation into specific lymphocyte types. Understanding the interactions between steroidogenic cells and ovarian lymphocytes within CL will not only enhance understanding of reproductive function but may provide vital clues to lymphocyte regulation within tissues.

Effect of mifepristone on the corpus luteum in early pregnancy

The antiprogestin mifepristone is widely used for medical termination of pregnancy (TOP). Previous studies have suggested that the mechanism of mifepristone is based on its action in the endometrium and myometrium. The aim of this study was to evaluate the possible effects of mifepristone on corpus luteum activity. This was a prospective, longitudinal controlled study to which 20 patients undergoing medical TOP (study group) and 20 patients with normal ongoing pregnancy (control group) were recruited. Medical TOP was induced with 200 mg of mifepristone followed by 0.8 mg of misoprostol 2 days later. Three-dimensional ultrasound examinations and hormone assays (progesterone, human chorionic gonadotropin, and 17-hydroxyprogesterone) were performed in both groups on the day of, and 2 days after, administration of mifepristone. Total volume (vascularized + non-vascularized) of the dominant (containing corpus luteum) and non-dominant ovary and serum hormone levels were measured. After administration of mifepristone, a decrease in serum progesterone levels was observed with a simultaneous decrease in the non-vascularized volume of the dominant ovary in the study group. No such changes were observed in the control group. The observations indicate that, in addition to trophoblastic tissue, the corpus luteum is also the target of mifepristone.

Angiogenesis in the human corpus luteum.

Angiogenesis is important for the formation and development of the corpus luteum and for maintenance of luteal function. Blood vessel regression is an important physiological phenomenon in the corpus luteum, which is associated with tissue involution during structural luteolysis. Angiogenesis actively occurs during the early luteal phase and is completed by the mid-luteal phase. Perivascular cells (pericytes) increase in number from the early luteal phase to the mid-luteal phase, suggesting that blood vessels are gradually stabilized until the mid-luteal phase. In the corpus luteum undergoing luteolysis, blood vessels and pericytes decrease in number, which is related to structural involution. In the corpus luteum of early pregnancy, the number of blood vessels with pericytes increases, suggesting that angiogenesis occurs again, accompanied by blood vessel stabilization. These changes in vasculature of the corpus luteum are regulated by the collaboration with vascular endothelial growth factor, which is involved in proliferation of vascular endothelial cells, and angiopoietins, which are involved in stabilization of blood vessels. This review focuses on angiogenesis, blood vessel stabilization and blood vessel regression during the divergent phases of luteal formation, luteal regression and luteal rescue by pregnancy. (Reprod Med Biol 2008; 7: 91-103).

LUTEINIZING HORMONE (LH) STIMULATES MTOR/S6K SIGNALING PATHWAY BY DEACTIVATING GSK3 AND AMPK IN CULTURED BOVINE CORPORA LUTEAL CELLS

The corpus luteum (CL) is a transient reproductive gland that produces progesterone, a required product for the establishment and maintenance of pregnancy. Inadequate nutritional status or energy balance negatively impacts reproductive potential and reduces steroidogenesis. While it is appreciated that luteinizing hormone (LH) is a crucial factor involved in stimulating the secretion of progesterone by the CL, the cellular and molecular mechanisms that regulate the maintenance of the CL are poorly understood. Recent studies have implicated a variety of key protein kinases in cellular responses linked to cellular energy homeostasis. These include glycogen synthase kinase 3 (GSK3), AMP-activated protein kinase (AMPK), and the mammalian target of rapamycin (mTOR). While GSK3 and AMPK impair protein synthesis, mTOR stimulates protein translation via mechanisms involving the phosphorylation of the 70-kDa ribosomal S6 protein kinase (S6K) and the translation regulator eukaryotic initiation factor 4E-binding protein (4EBP1). A recent report suggests that GSK3 works in concert with AMPK to inhibit the mTOR pathway. Here, we studied the actions of LH on the regulation of mTOR/S6K signaling pathway in steroidogenic corpus luteum cells. Bovine luteal cells were derived from CL of early pregnancy. Primary cultures of luteal cells were treated and the phosphorylation status of S6K, GSK3, and AMPK was examined by western immuno-blot using phospho-specific antibodies. The activity of S6K was analyzed by an in vitro immunocomplex kinase assay using a GST-S6 peptide as substrate. Translational activation was monitored by 4EBP1 phosphorylation and the release of 4EBP1 binding in m7G cap binding assays. Treatment of luteal cells with LH (100 ng/ml), FSK (10 μM), a stimulator of adenylyl cyclase, or 8-BrcAMP (1 μM), a cAMP analogue significantly induced S6K phosphorylation and activation in a dose- and time-dependent manner. The phosphorylation of S6K1 in response to LH treatment was inhibited by a protein kinase A (PKA)-specific inhibitor Rp-8-Br-cAMP. Another cAMP analogue 8-CPT-2-Me-cAMP, which activates cAMP-guanine nucleotide exchange factors (EPAC) without activating PKA, had no effect on S6K phosphorylation. These findings suggest that LH and/or cAMP may regulate S6K phosphorylation via a PKA-dependent pathway. Treatment of luteal cells with LH also resulted in a time- and concentrationdependent inhibition of GSK3 activity by phosphorylating GSK3 at Ser9. The phosphorylation of GSK3 in response to LH was prevented by inhibitors of PKA. Deactivating GSK3 by treatment with GSK3 inhibitors, LiCl or GSKi, mimicked the stimulatory action of LH on S6K and S6 phosphorylation. Furthermore, LH treatment inhibited AMPK by phosphorylating AMPK on Thr172 residues. Pre-treatment of luteal cells with a cell-permeable AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) prevented S6K phosphorylation in response to LH. We also observed that LH activated mTOR/S6K down stream processes (i.e., 4EBP1 phosphorylation, release of 4EBP1 binding in m7G cap binding assay, and the phosphorylation of S6); and these events were inhibited by treatment with rapamycin or AICAR. In conclusion, LH and cAMP activate mTOR/S6K via a PKA-dependent signaling pathway that involves deactivating GSK3 and AMPK. We propose that mTOR/S6K integrates hormonal and energy signals to maintain CL function. Supported by VA, USDA, NIH and Olson Center for Women's Health. (platform)

OC98: How mifepristone affects corpus luteum in early pregnancy; a prospective, controlled study

OC98: How mifepristone affects corpus luteum in early pregnancy; a prospective, controlled study

Angiogenesis in the Human Corpus Luteum: Changes in Expression of Angiopoietins in the Corpus Luteum throughout the Menstrual Cycle and in Early Pregnancy

Blood vessel stabilization is regulated by angiopoietins and important for angiogenesis in the corpus luteum. To study angiogenesis and blood vessel stabilization in the human corpus luteum, changes in expression of angiopoietin (Ang)-1, Ang-2, and their specific receptor, Tie-2, together with the number of blood vessels and pericytes were examined in the corpus luteum throughout the menstrual cycle and in early pregnancy. The number of blood vessels and pericytes was determined by immunohistochemistry for CD34 and alpha-smooth muscle actin, respectively. Ang and Tie-2 expression were examined by immunohistochemistry or RT-PCR. The number of blood vessels increased during the early luteal phase, whereas the number of pericytes was small in the early luteal phase and increased in the midluteal phase, suggesting that angiogenesis is undergoing during the early luteal phase and blood vessels are stabilized in the midluteal phase. Blood vessels and pericytes decreased in number during the late luteal phase. The increased number of both blood vessels and pericytes seen in the corpus luteum of early pregnancy suggests that angiogenesis is undergoing accompanied by blood vessel stabilization. Ang-2 expression with low Ang-1 expression was found during the early luteal phase. Thereafter, increasing Ang-1 expression during the midluteal phase, declining Ang-1 expression with continued Ang-2 expression during the late luteal phase, and relatively high Ang-1 expression in early pregnancy were observed. The change in Ang expression is closely associated with angiogenesis, blood vessel stabilization, and blood vessel regression during the divergent phases of luteal formation, luteal regression, and luteal rescue by pregnancy.

Antioxidant enzymatic defence systems in sheep corpus luteum throughout pregnancy

The activities of copper, zinc-superoxide dismutase (SOD1), manganese SOD (SOD2), glutathione peroxidase (GPX), glutathione reductase (GSSG-R) and glutathione S-transferase (GST) were studied in sheep corpora lutea (CL) obtained on days 15, 40, 60, 80 and 128 of pregnancy. Maintained enzymatic activity of SOD1, SOD2, GPX, GSSG-R and GST were found in the sheep CL throughout pregnancy. Enzymatic activity of SOD1, GPX and GST increased significantly from day 15 to day 40 of pregnancy, and thereafter remained constant until day 128. SOD2 and GSSG-R activities were not different between any days of pregnancy examined. Apoptotic luteal cells identified by the terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick-end labelling were very rarely observed, and their incidence (less than 0.5%) was not different between days of pregnancy. These results showed that the activities of antioxidant enzymes in the sheep CL are subject to major changes during early pregnancy, suggesting that the CL of early pregnancy may be rescued from luteolysis through increasing activities of key antioxidant enzymes and inhibition of apoptosis. Maintained levels of antioxidant enzymes in the CL throughout pregnancy may be linked to reactive oxygen species continuously generated in the steroidogenically active luteal cells, and may be involved in the maintenance of luteal steroidogenic activity and cellular integrity.

Role of Ultrasonography and Color Doppler in Identification of the Corpus Luteum of Early Pregnancy

A prospective study was conducted in 49 first-trimester pregnancies—39 with live intrauterine pregnancies and 10 with missed abortions. Transvaginal sonography and color Doppler recorded size, sonographic appearance, color flow pattern, peak systolic velocity, and resistance index of each corpus luteum. Gray-scale sonographic appearances revealed thick-walled cysts, hypoechoic to isoechoic rounded structures, thin-walled cysts, and bilocular thick-walled cysts in patients with live intrauterine pregnancies. In patients with missed abortions, the most common pattern was thick-walled cysts, followed by hypoechoic areas and simple cysts. It was concluded that the corpus luteum, a well-identified structure in one of the ovaries in early pregnancy, has a wide range of sonographic morphologies. Better delineation is possible with color Doppler and color power angiography. Knowledge of the various morphological patterns on sonogram and color Doppler can help differentiate the corpus luteum from true ovarian pathologies.

Progesterone as a mediator of gonadotrophin action in the corpus luteum: beyond steroidogenesis.

Studies using newer, potent GnRH antagonists and pure gonadotrophins have clarified the importance of: (i) the strength-duration of the midcycle surge of pituitary gonadotrophins (LH, FSH) in follicle rupture and conversion to the corpus luteum; (ii) the continued requirement for pituitary LH throughout development and the functional lifespan of the primate corpus luteum in the menstrual cycle; and (iii) the exponential secretion of chorionic gonadotrophin (CG) by the developing placenta to extend the functional lifespan of the primate corpus luteum in early pregnancy. Although studies continue to increase current understanding of the cellular and molecular actions of LH/CG to stimulate luteal steroidogenesis, knowledge of the processes whereby these gonadotrophins promote the development and maintenance of the functional corpus luteum remains limited. This review summarizes evidence that the primate ovulatory follicle and corpus luteum is a target for the primary steroid produced by luteinizing/luteal tissue (i.e. progesterone). With evidence for dynamic expression of genomic progesterone receptors (PRA/B), and possibly other progesterone-receptor systems, recent studies addressed the hypothesis that progesterone is a critical 'local luteotrophin' that promotes luteal development and sustains luteal structure-function during the menstrual cycle and early pregnancy. Specific progesterone actions to regulate tissue remodelling (via protease expression), health (anti-apoptotic effects) and sensitivity to other local factors (e.g. via estrogen receptor expression) are discussed. The collective data suggest that there are gonadotrophin-stimulated, progesterone-dependent processes that promote luteotrophic and suppress luteolytic pathways in the primate corpus luteum. However, further studies are needed to verify their role in normal ovarian function and relevance to possible ovarian defects in natural and assisted reproduction technique-related cycles.

Angiogenesis in the corpus luteum of early pregnancy in the marmoset and the effects of vascular endothelial growth factor immunoneutralization on establishment of pregnancy.

This study investigated vascular and molecular changes in the corpus luteum (CL) of early pregnancy in the marmoset. Ovaries were studied on Days 21 (n = 6) and 28 (n = 6) of pregnancy and compared with corpora lutea from Day 21 (late luteal) of the nonconception cycle (n = 8). Endothelial cell proliferation was measured by immunocytochemical detection of incorporated bromodeoxyuridine. Endothelial cell and pericyte area were assessed by quantitative immunocytochemistry for CD31 and alpha-smooth muscle actin, respectively. Vascular endothelial growth factor (VEGF) and its receptors, kinase insert domain-containing region (KDR) and fms-like tyrosine kinase (Flt) mRNA, were localized and quantified in in situ hybridization. In addition, the effects of immunoneutralization of VEGF on establishment and maintenance of pregnancy were investigated by administering a VEGF neutralizing antibody on Days 0-10 of the luteal phase during potentially fertile cycles (n = 10) and compared with fertile controls (n = 6). No differences in the cellular or morphological parameters were found between pregnant and structurally intact nonpregnant corpora lutea. No major differences were found in expression of VEGF, Flt, or KDR in these CL. VEGF immunoneutralization markedly suppressed plasma progesterone secretion during treatment, but pregnancy rate was not significantly reduced. Thus, a role for VEGF in early pregnancy in the marmoset remains to be established. These results show that, by the late luteal phase in the marmoset, the corpus luteum has established a mature vascular system and the molecular capacity to synthesize VEGF and its receptors. A pregnancy-induced spurt of angiogenesis or gene expression does not appear to take place; rather, maintenance of the existing vasculature is all that is required for the establishment of pregnancy.