Application of Biomarkers in Obese Infertile Women: A Genetic Tool for a Personalized Treatment

This study investigates links between CART and leptin gene expression, FSH receptor Asn680Ser polymorphism, and reproductive hormones in morbidly obese patients under 40 years old, facing infertility, and undergoing bariatric surgery. A total of 29 women were included in this study. A hormonal profile along with detection of CART and leptin gene expression was evaluated before and after bariatric surgery. Additionally, the presence or absence of Asn680Ser of the FSHR gene was studied. Following bariatric surgery, a mean reduction in BMI (16.03 kg/m2) was observed in all women. FSH levels preoperatively varied significantly among genotypes, with medians of 8.1, 9.5, and 10.3 for individuals without polymorphism, heterozygotes, and homozygotes, respectively (p = 0.0408). Post surgery, marginal differences in FSH levels were observed (5.8, 7.1, and 8.2, respectively) (p = 0.0356). E2 and LH levels exhibited no significant genotype-based differences pre and post surgery. Presurgical E2 levels were 29.6, 29.8, and 29.6, respectively (p = 0.91634), while postsurgical levels were 51.2, 47.8, and 47 (p = 0.7720). LH levels followed similar patterns. Our findings highlight bariatric surgery's positive impact on BMI reduction and its potential connection to genetic markers, hormones, and infertility. This suggests personalized treatments and offers a valuable genetic tool for better fertility outcomes in obese individuals.

Maternal obesity and ovarian failure: is leptin the culprit?

At the time of its discovery and characterization in 1994, leptin was mostly considered a metabolic hormone able to regulate body weight and energy homeostasis. However, in recent years, a great deal of literature has revealed leptin's pleiotropic nature, through its involvement in numerous physiological contexts including the regulation of the female reproductive tract and ovarian function. Obesity has been largely associated with infertility, and leptin signalling is known to be dysregulated in the ovaries of obese females. Hence, the disruption of ovarian leptin signalling was shown to contribute to the pathophysiology of ovarian failure in obese females, affecting transcriptional programmes in the gamete and somatic cells. This review attempts to uncover the underlying mechanisms contributing to female infertility associated with obesity, as well as to shed light on the role of leptin in the metabolic dysregulation within the follicle, the effects on the oocyte epigenome, and the potential long-term consequence to embryo programming.

The Effects of Prostaglandin E2 Treatment on the Secretory Function of Mare Corpus Luteum Depends on the Site of Application: An in vivo Study

We examined the effect of prostaglandin (PG) E₂ on the secretory function of equine corpus luteum (CL), according to the application site: intra-CL injection vs. an intrauterine (intra-U) administration. Moreover, the effect of intra-CL injection vs. intra-U administration of both luteotropic factors: PGE₂ and human chorionic gonadotropin (hCG) as a positive control, on CL function was additionally compared. Mares were assigned to the groups (n = 6 per group): (1) an intra-CL saline injection (control); (2) an intra-CL injection of PGE₂ (5 mg/ml); (3) an intra-CL injection of hCG (1,500 IU/ml); (4) an intra-U saline administration (control); (5) an intra-U administration of PGE₂ (5 mg/5 ml); (6) an intra-U administration of hCG (1,500 IU/5 ml). Progesterone (P₄) and PGE₂ concentrations were measured in blood plasma samples collected at −2, −1, and 0 (pre-treatment), and at 1, 2, 3, 4, 6, 8, 10, 12, and 24 h after treatments. Moreover, effects of different doses of PGE₂ application on the concentration of total PGF_2α (PGF_2α and its main metabolite 13,14-dihydro-15-keto-prostaglandin F_2α– PGFM) was determined. The time point of PGE₂, hCG, or saline administration was defined as hour “0” of the experiment. An intra-CL injection of PGE₂ increased P₄ and PGE₂ concentrations between 3 and 4 h or at 3 and 12 h, respectively (p < 0.05). While intra-U administration of PGE₂ elevated P₄ concentrations between 8 and 24 h, PGE₂ was upregulated at 1 h and between 3 and 4 h (p < 0.05). An intra-CL injection of hCG increased P₄ concentrations at 1, 6, and 12 h (p < 0.05), while its intra-U administration enhanced P₄ and PGE₂ concentrations between 1 and 12 h or at 3 h and between 6 and 10 h, respectively (p < 0.05). An application of PGE₂, dependently on the dose, supports equine CL function, regardless of the application site, consequently leading to differences in both P₄ and PGE₂ concentrations in blood plasma.

Expression profile of the Kisspeptin/Kiss1r system and angiogenic and immunological mediators in the ovary of cyclic and pregnant cats

The Kisspeptin/Kiss1r system has been studied in mammalian ovaries. However, there are still no studies on the modulation of this system and its relationship with angiogenic and immunological mediators in the ovary of domestic cats, especially during pregnancy. We evaluated the expression of Kisspeptin/Kiss1r and angiogenic and immunological mediators during folliculogenesis, luteogenesis and luteal regression of cyclic and pregnant cats. The ovary exhibited moderate to intense expression for Kiss1, VEGF, Flk-1, INFγ and MIF in oocytes and the follicular wall, while Kiss1r expression was low in granulosa cells. In these cells, there was also a greater expression of Kiss1, INFγ and MIF, mainly in secondary follicles, while tertiary and preovulatory follicles exhibited greater expression of VEGF and Flk-1 in this layer. In luteogenesis, Kiss1 immunostaining was higher in mature corpora lutea (MCL) of pregnant cats compared to vacuolated CL (VCL) and corpus albicans (CA). Pregnancy also increased the luteal gene expression of Kiss1 as well as Kiss1, Kiss1r, Flk-1, and MIF immunostaining in MCL, while reduced the area of VEGF expression in VCL and luteal mRNA expression of Mif when compared to non-pregnant animals. In addition, positive gene correlation between Kiss1r and Mif was observed in the CL. Kiss1, Kiss1r, Vegf and Mif expression were lower in the CA of cats in anestrus. These findings reveal that the expression of Kisspeptin/Kiss1r and angiogenic and immunological mediators, in the ovary of domestic cats, depend on the follicular and luteal stage, and the luteal expression of these mediators is influenced by pregnancy.

Leptin Signaling in the Ovary of Diet-Induced Obese Mice Regulates Activation of NOD-Like Receptor Protein 3 Inflammasome

Obesity leads to ovarian dysfunction and the establishment of local leptin resistance. The aim of our study was to characterize the levels of NOD-like receptor protein 3 (NLRP3) inflammasome activation in ovaries and liver of mice during obesity progression. Furthermore, we tested the putative role of leptin on NLRP3 regulation in those organs. C57BL/6J female mice were treated with equine chorionic gonadotropin (eCG) or human chorionic gonadotropin (hCG) for estrous cycle synchronization and ovary collection. In diet-induced obesity (DIO) protocol, mice were fed chow diet (CD) or high-fat diet (HFD) for 4 or 16 weeks, whereas in the hyperleptinemic model (LEPT), mice were injected with leptin for 16 days (16 L) or saline (16 C). Finally, the genetic obese leptin-deficient ob/ob (+/? and −/−) mice were fed CD for 4 week. Either ovaries and liver were collected, as well as cumulus cells (CCs) after superovulation from DIO and LEPT. The estrus cycle synchronization protocol showed increased protein levels of NLRP3 and interleukin (IL)-18 in diestrus, with this stage used for further sample collections. In DIO, protein expression of NLRP3 inflammasome components was increased in 4 week HFD, but decreased in 16 week HFD. Moreover, NLRP3 and IL-1β were upregulated in 16 L and downregulated in ob/ob. Transcriptome analysis of CC showed common genes between LEPT and 4 week HFD modulating NLRP3 inflammasome. Liver analysis showed NLRP3 protein upregulation after 16 week HFD in DIO, but also its downregulation in ob/ob−/−. We showed the link between leptin signaling and NLRP3 inflammasome activation in the ovary throughout obesity progression in mice, elucidating the molecular mechanisms underpinning ovarian failure in maternal obesity.

CXCL12 May Drive Inflammatory Potential in the Ovine Corpus Luteum During Implantation

Adequate corpus luteum (CL) function is paramount to successful pregnancy. Structural and functional CL integrity is controlled by diverse cell types that contribute and respond to the local cytokine milieu. The chemokine ligand 12 (CXCL12) and receptor, CXCR4, are modulators of inflammation and cell survival, but little is understood about CXCL12-CXCR4 axis and CL functional regulation. Corpora lutea from control nonpregnant ewes (n = 5; day 10 estrous cycle (D10C)) and pregnant ewes (n = 5/day) on days 20 (D20P) and 30 (D30P) post-breeding were analyzed for gene and protein expression of CXCL12, CXCR4, and select inflammatory cytokines. In separate cell culture studies, cytokine production was evaluated following CXCL12 treatment. Abundance of CXCL12 and CXCR4 increased (P < 0.05) in pregnant ewes compared to nonpregnant ewes, as determined by a combination of quantitative PCR, immunoblot, and immunofluorescence microscopy. CXCR4 was detected in steroidogenic and nonsteroidogenic cells in ovine CL, and select pro-inflammatory mediators were greater in CL from pregnant ewes. In vitro studies revealed greater abundance of tumor necrosis factor (TNF) following CXCL12 administration (P = 0.05), while P4 levels in cell media were unchanged. Fully functional CL of pregnant ewes is characterized by increased abundance of inflammatory cytokines which may function in a luteotropic manner. We report concurrent increases in CXCL12, CXCR4, and select inflammatory mediators in ovine CL as early pregnancy progresses. We propose CXCL12 stimulates production of select cytokines, rather than P4 in the CL to assist in CL establishment and survival.

CHEMERIN as a modulator of angiogenesis and apoptosis processes in the corpus luteum of pigs: An in vitro study

The corpus luteum (CL) undergoes rapid changes, and its functional capabilities are influenced by processes such as angiogenesis and apoptosis. According to the literature, chemerin - a protein which participates in the regulation of energy homeostasis and the immune response, may also affect angiogenesis and apoptosis. Therefore, the aim of this study was to investigate the in vitro effect of chemerin on angiogenesis and apoptosis in porcine luteal cells (Lc) during specific phases related to CL physiology. Luteal cells were harvested from gilts during the early-, mid-, and late-luteal phases of the estrous cycle. The cells were preincubated for 48 h and incubated for 24 h with chemerin or a serum-free medium (controls). The abundance of angiogenesis- and apoptosis-related proteins was determined by ELISA in spent culture media, or by ELISA and Western Blot in protein extracts. The current study demonstrated that chemerin stimulates the production of VEGF-A and bFGF by porcine Lc and increases the protein abundance of angiogenic factors receptors (VEGFR1, VEGFR2, VEGFR3, FGFR1, FGFR2) in these cells. The study also revealed that chemerin exerts a modulatory effect (stimulatory/inhibitory, depending on the phase of the cycle) on the protein abundance of Fas, FasL, Bcl-2 and caspase-3 in porcine Lc. These results imply that chemerin may affect angiogenesis and apoptosis processes in the porcine CL, as evidenced by its modulatory effect of chemerin on the protein abundance of crucial angiogenesis- and apoptosis-related factors, observed in an in vitro study of porcine Lc.

Microvascularization and Expression of Fibroblast Growth Factor and Vascular Endothelial Growth Factor and Their Receptors in the Mare Oviduct

Simple Summary

The oviduct provides the ideal conditions for fertilization and early embryonic development. Adequate vascularization is essential for proper oviduct physiological function. In this work on the mare oviduct, differences in the oviductal artery and arterioles and their ramifications in the infundibulum, ampulla and isthmus were examined. Locally, vascularization is modulated by the action of angiogenic factors, mediated by their specific receptors. In the present study, the isthmus presented the largest vascular area and the highest number of vascular structures in the follicular phase. We have also shown that the relative abundance of angiogenic transcripts and proteins, such as fibroblast growth factor 1 (FGF1) and 2 (FGF2) and vascular endothelial growth factor (VEGF), and their respective receptors (FGFR1, FGFR2, VEGFR2 = KDR), were present in all portions of the oviduct throughout the estrous cycle. There was an increase in the transcripts of angiogenic receptors FGF1 and FGFR1 in the ampulla and isthmus, and of FGF2 and KDR in the isthmus. This was also observed in the isthmus, where the relative abundance of proteins FGFR1 and KDR was the highest. This study shows that the equine oviduct presents differences in microvascular density in its portions. The angiogenic factors VEGF, FGF1, FGF2 and their respective receptors are expressed in all studied regions of the mare oviduct, in agreement with microvascular patterns.

Abstract

The oviduct presents the ideal conditions for fertilization and early embryonic development. In this study, (i) vascularization pattern; (ii) microvascular density; (iii) transcripts of angiogenic factors (FGF1, FGF2, VEGF) and their receptors—FGFR1, FGFR2, KDR, respectively, and (iv) the relative protein abundance of those receptors were assessed in cyclic mares’ oviducts. The oviductal artery, arterioles and their ramifications, viewed by means of vascular injection-corrosion, differed in the infundibulum, ampulla and isthmus. The isthmus, immunostained with CD31, presented the largest vascular area and the highest number of vascular structures in the follicular phase. Transcripts (qPCR) and relative protein abundance (Western blot) of angiogenic factors fibroblast growth factor 1 (FGF1) and 2 (FGF2) and vascular endothelial growth factor (VEGF), and their respective receptors (FGFR1, FGFR2, VEGFR2 = KDR), were present in all oviduct portions throughout the estrous cycle. Upregulation of the transcripts of angiogenic receptors FGF1 and FGFR1 in the ampulla and isthmus and of FGF2 and KDR in the isthmus were noted. Furthermore, in the isthmus, the relative protein abundance of FGFR1 and KDR was the highest. This study shows that the equine oviduct presents differences in microvascular density in its three portions. The angiogenic factors VEGF, FGF1, FGF2 and their respective receptors are expressed in all studied regions of the mare oviduct, in agreement with microvascular patterns.

Endothelial cells and angiogenesis in the horse in health and disease-A review

The cardiovascular system is the first functional organ in the embryo, and its blood vessels form a widespread conductive network within the organism. Blood vessels develop de novo, by the differentiation of endothelial progenitor cells (vasculogenesis) or by angiogenesis, which is the formation of new blood vessels from existing ones. This review presents an overview of the current knowledge on physiological and pathological angiogenesis in the horse including studies on equine endothelial cells. Principal study fields in equine angiogenesis research were identified: equine endothelial progenitor cells; equine endothelial cells and angiogenesis (heterogeneity, markers and assessment); endothelial regulatory molecules in equine angiogenesis; angiogenesis research in equine reproduction (ovary, uterus, placenta and conceptus, testis); angiogenesis research in pathological conditions (tumours, ocular pathologies, equine wound healing, musculoskeletal system and laminitis). The review also includes a table that summarizes in vitro studies on equine endothelial cells, either describing the isolation procedure or using previously isolated endothelial cells. A particular challenge of the review was that results published are fragmentary and sometimes even contradictory, raising more questions than they answer. In conclusion, angiogenesis is a major factor in several diseases frequently occurring in horses, but relatively few studies focus on angiogenesis in the horse. The challenge for the future is therefore to continue exploring new therapeutic angiogenesis strategies for horses to fill in the missing pieces of the puzzle.

Inflammation and angiogenesis in the corpus luteum

Angiogenesis is a very important process that helps establish and maintain the normal structure and function of the corpus luteum (CL). Early luteal development can be considered a kind of physiological injury with an inflammatory response; therefore, the inflammatory response may play an important role in the luteal angiogenesis. The inflammatory response is companied by activated leukocytes and their mediators. For luteal tissue, numerous activated leukocytes such as macrophages, neutrophils and eosinophils are present in the early luteal phase and are widely involved in neovascularization. The objective of this review is to describe the role of the inflammatory factors in the angiogenesis and to discuss their mechanism. Knowledge of action and mechanism of these inflammatory factors on angiogenic activity will be beneficial for the understanding of luteal function.

The Interaction Between Nodal, Hypoxia-Inducible Factor 1 Alpha, and Thrombospondin 1 Promotes Luteolysis in Equine Corpus Luteum

The regulation of corpus luteus (CL) luteolysis is a complex process involving a myriad of factors. Previously, we have shown the involvement of Nodal in functional luteolysis in mares. Presently, we ask the extent of which Nodal mediation of luteolysis is done through regulation of angioregression. We demonstrated the interaction between Nodal and hypoxia-inducible factor 1 α (HIF1α) and thrombospondin 1/thrombospondin receptor (TSP1/CD36) systems, could mediate angioregression during luteolysis. First, we demonstrated the inhibitory effect of Nodal on the vascular marker platelet/endothelial cell adhesion molecule 1 (CD31). Also, treatment of mid CL explants with vascular endothelial growth factor A (VEGFA) showed a trend on activin-like kinase 7 (Alk7) protein inhibition. Next, Nodal was also shown to activate HIF1α and in vitro culture of mid CL explants under decreased oxygen level promoted Nodal expression and SMAD family member 3 (Smad3) phosphorylation. In another experiment, the crosstalk between Nodal and TSP1/CD36 was investigated. Indeed, Nodal increased the expression of the anti-angiogenic TSP1 and its receptor CD36 in mid CL explants. Finally, the supportive effect of prostaglandin F2α (PGF2α) on TSP1/CD36 was blocked by SB431542 (SB), a pharmacological inhibitor of Nodal signaling. Thus, we evidenced for the first time the in vitro interaction between Nodal and both HIF1α and TSP1 systems, two conserved pathways previously shown to be involved in vascular regression during luteolysis. Considering the given increased expression of Nodal in mid CL and its role on functional luteolysis, the current results suggest the additional involvement of Nodal in angioregression during luteolysis in the mare, particularly in the activation of HIF1α and TSP1/CD36.

Luteolysis and the Auto-, Paracrine Role of Cytokines From Tumor Necrosis Factor α and Transforming Growth Factor β Superfamilies

Successful pregnancy establishment demands optimal luteal function in mammals. Nonetheless, regression of the corpus luteum (CL) is absolutely necessary for normal female cyclicity. This dichotomy relies on intricate molecular signals and rapidly activated biological responses, such as angiogenesis, extracellular matrix (ECM) remodeling, or programmed cell death. The CL establishment and growth after ovulation depend not only on the luteinizing hormone-mediated endocrine signal but also on a number of auto-, paracrine interactions promoted by cytokines and growth factors like fibroblast growth factor 2, vascular endothelial growth factor A, and tumor necrosis factor α (TNF), which coordinate vascularigenesis and ECM reorganization as well as steroidogenesis. With the organ fully developed, the release of the uterine prostaglandin F2α activates luteolysis, an intricate process supported by intraluteal interactions that ensure the loss of steroidogenic function (functional luteolysis) and the involution of the organ (structural luteolysis). This chapter provides an overview of the local action of cytokines during luteal function, with particular emphasis on the role of TNF and transforming growth factor β superfamilies during luteolysis.

Nodal Promotes Functional Luteolysis via Down-Regulation of Progesterone and Prostaglandins E2 and Promotion of PGF2α Synthetic Pathways in Mare Corpus Luteum

In the present work, we investigated the role of Nodal, an embryonic morphogen from the TGFβ superfamily in corpus luteum (CL) secretory activity using cells isolated from equine CL as a model. Expression pattern of Nodal and its receptors activin receptor A type IIB (ACVR2B), activin receptor-like kinase (Alk)-7, and Alk4, as well as the Nodal physiological role, demonstrate the involvement of this pathway in functional luteolysis. Nodal and its receptors were immune localized in small and large luteal cells and endothelial cells, except ACVR2B, which was not detected in the endothelium. Nodal mRNA in situ hybridization confirmed its transcription in steroidogenic and endothelial cells. Expression analysis of the aforementioned factors evidenced that Nodal and Alk7 proteins peaked at the mid-CL (P < .01), the time of luteolysis initiation, whereas Alk4 and ACVR2B proteins increased from mid- to late CL (P < .05). The Nodal treatment of luteal cells decreased progesterone and prostaglandin (PG) E2 concentrations in culture media (P < .05) as well as mRNA and protein of secretory enzymes steroidogenic acute regulatory protein, cholesterol side-chain cleavage enzyme, cytosolic PGE2 synthase, and microsomal PGE2 synthase-1 (P < .05). Conversely, PGF2α secretion and gene expression of PG-endoperoxidase synthase 2 and PGF2α synthase were increased after Nodal treatment (P < .05). Mid-CL cells cultured with PGF2α had increased Nodal protein expression (P < .05) and phosphorylated mothers against decapentaplegic-3 phosphorylation (P < .05). Finally, the supportive interaction between Nodal and PGF2α on luteolysis was shown to its greatest extent because both factors together more significantly inhibited progesterone (P < .05) and promoted PGF2α (P < .05) synthesis than Nodal or PGF2α alone. Our results neatly pinpoint the sites of action of the Nodal signaling pathway toward functional luteolysis in the mare.

Physiological Capillary Regression is not Dependent on Reducing VEGF Expression

Investigations into physiologically controlled capillary regression report the provocative finding that microvessel regression occurs in the face of persistent elevation of skeletal muscle VEGF expression. TSP-1, a negative angiogenic regulator, is increasingly being observed to temporally correlate with capillary regression, suggesting that increased TSP-1 (and not reduction in VEGF per se) is needed to initiate, and likely regulate, capillary regression. Based on evidence being gleaned from physiologically mediated regression of capillaries, it needs to be recognized that capillary regression (and perhaps capillary rarefaction with disease) is not simply the reversal of factors used to stimulate angiogenesis. Rather, the conceptual understanding that angiogenesis and capillary regression each have specific and unique requirements that are biologically constrained to opposite sides of the balance between positive and negative angioregulatory factors may shed light on why anti-VEGF therapies have not lived up to the promise in reversing angiogenesis and providing the cure that many had hoped toward fighting cancer. Emerging evidence from physiological controlled angiogenesis suggest that cases involving excessive or uncontrolled capillary expansion may be best treated by therapies designed to increase expression of negative angiogenic regulators, whereas those involving capillary rarefaction may benefit from inhibiting negative regulators (like TSP-1).

Expression of angiogenic factors and luteinizing hormone receptors in the corpus luteum of mares induced to ovulate with deslorelin acetate

The effects of deslorelin acetate use in inducing ovulation need to be clarified to improve the results of equine embryo transfer. The mRNA abundance for angiogenic factors and LH receptor (LHR) in corpus luteum (CL) was studied in mares with natural (control group [CG]) and induced ovulation with deslorelin acetate (treatment group [TG]; follicles: ≥ 35 mm). Transrectal ultrasonography was used to verify the ovulation day, and on Days 4, 8, and 12 after ovulation (Day 0), CL samples were obtained through ultrasound-guided biopsy. The messenger RNA expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and LHR genes were analyzed by real-time polymerase chain reaction. A positive correlation was observed between VEGF and LHR (P < 0.00001, r = 0.78), and it was possible to detect higher LHR expression in the TG than in the CG on Day 4 (P < 0.05). Moreover, this expression was higher on Days 4 and 8 than on Day 12 in the TG. Basic fibroblast growth factor was also expressed in luteal tissue on all days for both groups; however, these differences were not significant. In conclusion, deslorelin acetate was effective for the induction of ovulation in mares, resulting in higher expression of LHR, especially on the fourth day after ovulation. In addition, VEGF expression was influenced by induced ovulation, with a lower level on Day 12, which is expected in nonpregnant mares.

The luteotrophic function of galectin-1 by binding to the glycans on vascular endothelial growth factor receptor-2 in bovine luteal cells

The corpus luteum (CL) is a temporary endocrine gland producing a large amount of progesterone, which is essential for the establishment and maintenance of pregnancy. Galectin-1 is a β-galactose-binding protein that can modify functions of membrane glycoproteins and is expressed in the CL of mice and women. However, the physiological role of galectin-1 in the CL is unclear. In the present study, we investigated the expression and localization of galectin-1 in the bovine CL and the effect of galectin-1 on cultured luteal steroidogenic cells (LSCs) with special reference to its binding to the glycans on vascular endothelial growth factor receptor-2 (VEGFR-2). Galectin-1 protein was highly expressed at the mid and late luteal stages in the membrane fraction of bovine CL tissue and was localized to the surface of LSCs in a carbohydrate-dependent manner. Galectin-1 increased the viability in cultured LSCs. However, the viability of LSCs was decreased by addition of β-lactose, a competitive carbohydrate inhibitor of galectin-1 binding activity. VEGFR-2 protein, like galectin-1, is also highly expressed in the mid CL, and it was modified by multi-antennary glycans, which can be recognized by galectin-1. An overlay assay using biotinylated galectin-1 revealed that galectin-1 directly binds to asparagine-linked glycans (N-glycans) on VEGFR-2. Enhancement of LSC viability by galectin-1 was suppressed by a selective inhibitor of VEGFR-2. The overall findings suggest that galectin-1 plays a role as a survival factor in the bovine CL, possibly by binding to N-glycans on VEGFR-2.

The contribution of the maternal immune system to the establishment of pregnancy in cattle

Immune cells play an integral role in affecting successful reproductive function. Indeed, disturbed or aberrant immune function has been identified as primary mechanisms behind infertility. In contrast to the extensive body of literature that exists for human and mouse, studies detailing the immunological interaction between the embryo and the maternal endometrium are quite few in cattle. Nevertheless, by reviewing the existing studies and extrapolating from sheep, pig, mouse, and human data, we can draw a reasonably comprehensive picture. Key contributions of immune cell populations include granulocyte involvement in follicle differentiation and gamete transfer, monocyte invasion of the peri-ovulatory follicle and their subsequent role in corpus luteum formation and the pivotal roles of maternal macrophage and dendritic cells in key steps of the establishment of pregnancy, particularly, the maternal immune response to the embryo. These contributions are reviewed in detail below and key findings are discussed.

Opposing roles of leptin and ghrelin in the equine corpus luteum regulation: an in vitro study

Metabolic hormones have been associated with reproductive function modulation. Thus, the aim of this study was: (i) to characterize the immunolocalization, mRNA and protein levels of leptin (LEP), Ghrelin (GHR) and respective receptors LEPR and Ghr-R1A, throughout luteal phase; and (ii) to evaluate the role of LEP and GHR on progesterone (P₄), prostaglandin (PG) E₂ and PGF_2α, nitric oxide (nitrite), tumor necrosis factor-α (TNF); macrophage migration inhibitory factor (MIF) secretion, and on angiogenic activity (BAEC proliferation), in equine corpus luteum (CL) from early and mid-luteal stages. LEPR expression was decreased in late CL, while GHR/Ghr-R1A system was increased in the same stage. Regarding secretory activity, GHR decreased P₄ in early CL, but increased PGF_2α, nitrite and TNF in mid CL. Conversely, LEP increased P₄, PGE₂, angiogenic activity, MIF, TNF and nitrite during early CL, in a dose-dependent manner. The in vitro effect of LEP on secretory activity was reverted by GHR, when both factors acted together. The present results evidence the presence of LEP and GHR systems in the equine CL. Moreover, we suggest that LEP and GHR play opposing roles in equine CL regulation, with LEP supporting luteal establishment and GHR promoting luteal regression. Finally, a dose-dependent luteotrophic effect of LEP was demonstrated.

The thrombospondin-1 receptor CD36 is an important mediator of ovarian angiogenesis and folliculogenesis

BACKGROUND

Ovarian angiogenesis is a complex process that is regulated by a balance between pro- and anti-angiogenic factors. Physiological processes within the ovary, such as folliculogenesis, ovulation, and luteal formation are dependent upon adequate vascularization and anything that disrupts normal angiogenic processes may result in ovarian dysfunction, and possibly infertility. The objective of this study was to evaluate the role of the thrombospondin-1 (TSP-1) receptor CD36 in mediating ovarian angiogenesis and regulating ovarian function.

METHODS

The role of CD36 was evaluated in granulosa cells in vitro and ovarian morphology and protein expression were determined in wild type and CD36 null mice.

RESULTS

In vitro, CD36 inhibition increased granulosa cell proliferation and decreased apoptosis. Granulosa cells in which CD36 was knocked down also exhibited an increase in expression of survival and angiogenic proteins. Ovaries from CD36 null mice were hypervascularized, with increased expression of pro-angiogenic vascular endothelial growth factor (VEGF) and its receptor VEGFR-2. Ovaries from CD36 null mice contained an increase in the numbers of pre-ovulatory follicles and decreased numbers of corpora lutea. CD36 null mice also had fewer number of offspring compared to wild type controls.

CONCLUSIONS

The results from this study demonstrate that CD36 is integral to the regulation of ovarian angiogenesis by TSP-1 and the expression of these family members may be useful in the control of ovarian vascular disorders.

Role of tumor necrosis factor-α, interferon-γ and Fas-ligand on in vitro nitric oxide activity in the corpus luteum

Normal reproductive function involves the expression of inflammatory mediators. Regarding the corpus luteum (CL), cytokines promote the cross-talk between immune, vascular and steroidogenic cells, among others. Moreover, TNF, IFNG and FASL were shown to regulate equine CL establishment and regression. We hypothesized that cytokines action on equine CL may be mediated by nitric oxide (NO), through the regulation of endothelial NO synthase (eNOS) expression. TNF increased eNOS mRNA level and NO metabolite (nitrite) production during CL growth. Cytokines combined action (TNF+IFNG+FASL) promoted eNOS protein upregulation in mid-CL and nitrite production in mid and late-CL. However, in late-CL, TNF alone decreased nitrite secretion. These results indicate that in equine CL, cytokines TNF, IFNG and FASL regulate NO activity, via eNOS expression modulation.

Cytokines and angiogenesis in the corpus luteum

In adults, physiological angiogenesis is a rare event, with few exceptions as the vasculogenesis needed for tissue growth and function in female reproductive organs. Particularly in the corpus luteum (CL), regulation of angiogenic process seems to be tightly controlled by opposite actions resultant from the balance between pro- and antiangiogenic factors. It is the extremely rapid sequence of events that determines the dramatic changes on vascular and nonvascular structures, qualifying the CL as a great model for angiogenesis studies. Using the mare CL as a model, reports on locally produced cytokines, such as tumor necrosis factor α (TNF), interferon gamma (IFNG), or Fas ligand (FASL), pointed out their role on angiogenic activity modulation throughout the luteal phase. Thus, the main purpose of this review is to highlight the interaction between immune, endothelial, and luteal steroidogenic cells, regarding vascular dynamics/changes during establishment and regression of the equine CL.

Common pathophysiological mechanisms involved in luteal phase deficiency and polycystic ovary syndrome. Impact on fertility

Luteal phase deficiency (LPD) is a consequence of the corpus luteum (CL) inability to produce and preserve adequate levels of progesterone. This is clinically manifested by short menstrual cycles and infertility. Abnormal follicular development, defects in neo-angiogenesis or inadequate steroidogenesis in the lutein cells of the CL have been implicated in CL dysfunction and LPD. LPD and polycystic ovary syndrome (PCOS) are independent disorders sharing common pathophysiological profiles. Factors such as hyperinsulinemia, AMH excess, and defects in angiogenesis of CL are at the origin of both LPD and PCOS. In PCOS ovulatory cycles, infertility could result from dysfunctional CL. The aim of this review was to investigate common mechanisms of infertility in CL dysfunction and PCOS.