Stage-specific integration of maternal and embryonic peroxisome proliferator-activated receptor delta signaling is critical to pregnancy success

Embryo-derive TNF promotes decidualization via fibroblast activation

Decidualization is a process in which endometrial stromal fibroblasts differentiate into specialized secretory decidual cells and essential for the successful establishment of pregnancy. The underlying mechanism during decidualization still remains poorly defined. Because decidualization and fibroblast activation share similar characteristics, this study was to examine whether fibroblast activation is involved in decidualization. In our study, fibroblast activation-related markers are obviously detected in pregnant decidua and under in vitro decidualization. ACTIVIN A secreted under fibroblast activation promotes in vitro decidualization. We showed that arachidonic acid released from uterine luminal epithelium can induce fibroblast activation and decidualization through PGI₂ and its nuclear receptor PPARδ. Based on the significant difference of fibroblast activation-related markers between pregnant and pseudopregnant mice, we found that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium. Fibroblast activation is also detected under human in vitro decidualization. Similar arachidonic acid-PGI₂-PPARδ-ACTIVIN A pathway is conserved in human endometrium. Collectively, our data indicate that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium to induce fibroblast activation and decidualization.

Progress on the Role of Estrogen and Progesterone Signaling in Mouse Embryo Implantation and Decidualization

Embryo implantation and decidualization are key steps in establishing a successful pregnancy. Defects in embryo implantation and decidualization can cause a series of adverse chain reactions which can contribute to harmful pregnancy outcomes, such as embryo growth retardation, preeclampsia, miscarriage, premature birth, and so on. Approximately 75% of failed pregnancies are considered to be due to embryo implantation failure or defects. Decidualization, characterized by proliferation and differentiation of uterine stromal cells, is one of the essential conditions for blastocyst implantation, placental formation, and maintenance of pregnancy and is indispensable for the establishment of pregnancy in many species. Embryo implantation and decidualization are closely regulated by estrogen and progesterone secreted by the ovaries. Many cellular events and molecular signaling network pathways are involved in this process. This article reviews the recent advances in the molecular mechanisms of estrogen- and progesterone-regulating uterine receptivity establishment, blastocyst implantation, and decidualization, in order to better understand the underlying molecular mechanisms of hormonal regulation of embryo implantation and to develop new strategies for preventing or treating embryo implantation defects and improving the pregnancy rate of women.

Cannabinoid and planar cell polarity signaling converges to direct placentation

Directed trophoblast migration toward the maternal mesometrial pole is critical for placentation and pregnancy success. Trophoblasts replace maternal arterial endothelial cells to increase blood supply to the placenta. Inferior trophoblast invasion results in pregnancy complications including preeclampsia, intrauterine growth restriction, miscarriage, and preterm delivery. The maternal chemotactic factors that direct trophoblast migration and the mechanism by which trophoblasts respond to these factors are not clearly understood. Here, we show that invasive trophoblasts deficient in Vangl2, a core planar cell polarity (PCP) component, fail to invade in maternal decidua, and this deficiency results in middle-gestational fetal demise. Previously, we have shown that tightly regulated endocannabinoids via G protein-coupled cannabinoid receptor CB1 are critical to the invasion of trophoblasts called spiral artery trophoblast giant cells (SpA-TGCs). We find that CB1 directly interacts with VANGL2. Trophoblast stem cells devoid of Cnr1 and/or Vangl2 show compromised cell migration. To study roles of VANGL2 and CB1 in trophoblast invasion in vivo, we conditionally deleted Cnr1 (coding CB1) and Vangl2 in progenitors of SpA-TGCs using trophoblast-specific protein alpha (Tpbpa)-Cre. We observed that signaling mediated by VANGL2 and CB1 restrains trophoblasts from random migration by keeping small GTPases quiescent. Our results show that organized PCP in trophoblasts is indispensable for their directed movement and that CB1 exerts its function by direct interaction with membrane proteins other than its canonical G protein-coupled receptor role.

In situ imaging reveals disparity between prostaglandin localization and abundance of prostaglandin synthases

Prostaglandins are important lipids involved in mediating many physiological processes, such as allergic responses, inflammation, and pregnancy. However, technical limitations of in-situ prostaglandin detection in tissue have led researchers to infer prostaglandin tissue distributions from localization of regulatory synthases, such as COX1 and COX2. Herein, we apply a novel mass spectrometry imaging method for direct in situ tissue localization of prostaglandins, and combine it with techniques for protein expression and RNA localization. We report that prostaglandin D₂, its precursors, and downstream synthases co-localize with the highest expression of COX1, and not COX2. Further, we study tissue with a conditional deletion of transformation-related protein 53 where pregnancy success is low and confirm that PG levels are altered, although localization is conserved. Our studies reveal that the abundance of COX and prostaglandin D₂ synthases in cellular regions does not mirror the regional abundance of prostaglandins. Thus, we deduce that prostaglandins tissue localization and abundance may not be inferred by COX or prostaglandin synthases in uterine tissue, and must be resolved by an in situ prostaglandin imaging.

Duncan et al. use a mass spectrometry imaging method to assess the localization and concentration of prostaglandins (PGs) in mouse tissues during pregnancy. This study brings new biological insights into the spatial evaluation of PGs in tissues, which could reveal the functional significance of each PGs during different stages of embryo development/pregnancy.

Peroxisome Proliferator-Activated Receptors (PPAR), fatty acids and microRNAs: Implications in women delivering low birth weight babies

Low birth weight (LBW) babies are associated with neonatal morbidity and mortality and are at increased risk for noncommunicable diseases (NCDs) in later life. However, the molecular determinants of LBW are not well understood. Placental insufficiency/dysfunction is the most frequent etiology for fetal growth restriction resulting in LBW and placental epigenetic processes are suggested to be important regulators of pregnancy outcome. Early life exposures like altered maternal nutrition may have long-lasting effects on the health of the offspring via epigenetic mechanisms like DNA methylation and microRNA (miRNA) regulation. miRNAs have been recognized as major regulators of gene expression and are known to play an important role in placental development. Angiogenesis in the placenta is known to be regulated by transcription factor peroxisome proliferator-activated receptor (PPAR) which is activated by ligands such as long-chain-polyunsaturated fatty acids (LCPUFA). In vitro studies in different cell types indicate that fatty acids can influence epigenetic mechanisms like miRNA regulation. We hypothesize that maternal fatty acid status may influence the miRNA regulation of PPAR genes in the placenta in women delivering LBW babies. This review provides an overview of miRNAs and their regulation of PPAR gene in the placenta of women delivering LBW babies.Abbreviations: AA - Arachidonic Acid; Ago2 - Argonaute2; ALA - Alpha-Linolenic Acid; ANGPTL4 - Angiopoietin-Like Protein 4; C14MC - Chromosome 14 miRNA Cluster; C19MC - Chromosome 19 miRNA Cluster; CLA - Conjugated Linoleic Acid; CSE - Cystathionine γ-Lyase; DHA - Docosahexaenoic Acid; EFA - Essential Fatty Acids; E2F3 - E2F transcription factor 3; EPA - Eicosapentaenoic Acid; FGFR1 - Fibroblast Growth Factor Receptor 1; GDM - Gestational Diabetes Mellitus; hADMSCs - Human Adipose Tissue-Derived Mesenchymal Stem Cells; hBMSCs - Human Bone Marrow Mesenchymal Stem Cells; HBV - Hepatitis B Virus; HCC - Hepatocellular Carcinoma; HCPT - Hydroxycamptothecin; HFD - High-Fat Diet; Hmads - Human Multipotent Adipose-Derived Stem; HSCS - Human Hepatic Stellate Cells; IUGR - Intrauterine Growth Restriction; LA - Linoleic Acid; LBW - Low Birth Weight; LCPUFA - Long-Chain Polyunsaturated Fatty Acids; MEK1 - Mitogen-Activated Protein Kinase 1; MiRNA - MicroRNA; mTOR - Mammalian Target of Rapamycin; NCDs - NonCommunicable Diseases; OA - Oleic Acid; PASMC - Pulmonary Artery Smooth Muscle Cell; PLAG1 - Pleiomorphic Adenoma Gene 1; PPAR - Peroxisome Proliferator-Activated Receptor; PPARα - PPAR alpha; PPARγ - PPAR gamma; PPARδ - PPAR delta; pre-miRNA - precursor miRNA; RISC - RNA-Induced Silencing Complex; ROS - Reactive Oxygen Species; SAT - Subcutaneous Adipose Tissue; WHO - World Health Organization.

Role of Peroxisome Proliferator-Activated Receptors (PPARs) in Trophoblast Functions

Peroxisome proliferator-activated receptors (PPARα, PPARβ/δ, and PPARγ) belong to the transcription factor family, and they are highly expressed in all types of trophoblast during pregnancy. The present review discusses currently published papers that are related to the regulation of PPARs via lipid metabolism, glucose metabolism, and amino acid metabolism to affect trophoblast physiological conditions, including differentiation, maturation, secretion, fusion, proliferation, migration, and invasion. Recent pieces of evidence have proven that the dysfunctions of PPARs in trophoblast lead to several related pregnancy diseases such as recurrent miscarriage, preeclampsia, intrauterine growth restriction, and gestational diabetes mellitus. Moreover, the underlying mechanisms of PPARs in the control of these processes have been discussed as well. Finally, this review's purposes are to provide more knowledge about the role of PPARs in normal and disturbed pregnancy with trophoblast, so as to find PPAR ligands as a potential therapeutic target in the treatment and prevention of adverse pregnancy outcomes.

Role of Dietary Amino Acids and Nutrient Sensing System in Pregnancy Associated Disorders

Defective implantation is related to pregnancy-associated disorders such as spontaneous miscarriage, intrauterine fetal growth restriction and others. Several factors proclaimed to be involved such as physiological, nutritional, environmental and managemental that leads to cause oxidative stress. Overloading of free radicals promotes oxidative stress, and the internal body system could not combat its ability to encounter the damaging effects and subsequently leading to pregnancy-related disorders. During pregnancy, essential amino acids display important role for optimum fetal growth and other necessary functions for continuing fruitful pregnancy. In this context, dietary amino acids have received much attention regarding the nutritional concerns during pregnancy. Arginine, glutamine, tryptophan and taurine play a crucial role in fetal growth, development and survival while ornithine and proline are important players for the regulation of gene expression, protein synthesis and angiogenesis. Moreover, amino acids also stimulate the mammalian target of rapamycin (mTOR) signaling pathway which plays a central role in the synthesis of proteins in placenta, uterus and fetus. This review article explores the significances of dietary amino acids in pregnancy development, regulation of nutrient-sensing pathways such as mTOR, peroxisome proliferator-activated receptors (PPARs), insulin/insulin-like growth factor signaling pathway (IIS) and 5' adenosine monophosphate-activated protein kinase (AMPK) which exhibit important role in reproduction and its related problems. In addition, the antioxidant function of dietary amino acids against oxidative stress triggering pregnancy disorders and their possible outcomes will also be enlightened. Dietary supplementation of amino acids during pregnancy could help mitigate reproductive disorders and thereby improving fertility in animals as well as humans.

PPARs and Angiogenesis-Implications in Pathology

Peroxisome proliferator-activated receptors (PPARs) belong to the family of ligand-activated nuclear receptors. The PPAR family consists of three subtypes encoded by three separate genes: PPARα (NR1C1), PPARβ/δ (NR1C2), and PPARγ (NR1C3). PPARs are critical regulators of metabolism and exhibit tissue and cell type-specific expression patterns and functions. Specific PPAR ligands have been proposed as potential therapies for a variety of diseases such as metabolic syndrome, cancer, neurogenerative disorders, diabetes, cardiovascular diseases, endometriosis, and retinopathies. In this review, we focus on the knowledge of PPAR function in angiogenesis, a complex process that plays important roles in numerous pathological conditions for which therapeutic use of PPAR modulation has been suggested.

Aberrant retinoic acid production in the decidua: Implications for pre-eclampsia

Fine-tuning of the endometrium during the evanescent 'window of implantation' relies upon an array of diverse and redundant signaling molecules, particularly the ovarian steroids E2 and P4, but also growth factors, eicosanoids, and vitamins including the vitamin A compounds (retinoids). Pregnancy complications such as preeclampsia (PE) can result from aberrations in the production or function of these molecules that arise during this critical period of decidual development. Such aberrations may be reflected by incomplete decidualization, reduced spiral artery modification, and/or loss of immune tolerance to the developing fetus. Our understanding of the role of the active retinoid metabolite all-trans retinoic acid (RA) in maintaining immune balance in certain tissues, along with data describing its role in decidualization, present a compelling argument that aberrant RA signaling in the decidua can play a significant role in the etiology of PE. Recent findings that decidualization and expression of the anti-angiogenic gene product, 'soluble fms-like tyrosine kinase-1' (sFLT1) are negatively correlated and that sFLT1 expression is directly inhibited by RA, provide additional evidence of the critical role of this retinoid in regulating early vascular development in the decidua. This review provides insight into the production and function of RA in the decidua and how modifications in its metabolism and signaling might lead to certain pregnancy disorders such as PE.

Critical role of mTOR, PPARγ and PPARδ signaling in regulating early pregnancy decidual function, embryo viability and feto-placental growth

STUDY QUESTION

What are the consequences of inhibiting mTOR, the mechanistic target of rapamycin (mTOR), and the peroxisome proliferator activated receptor gamma (PPARγ) and PPARδ pathways in the early post-implantation period on decidual function, embryo viability and feto-placental growth in the rat?

SUMMARY ANSWER

mTOR inhibition from Days 7 to 9 of pregnancy in rats caused decidual PPARγ and PPARδ upregulation on Day 9 of pregnancy and resulted in embryo resorption by Day 14 of pregnancy. PPARγ and PPARδ inhibition differentially affected decidual mTOR signaling and levels of target proteins relevant to lipid histotrophic nutrition and led to reduced feto-placental weights on Day 14 of pregnancy.

WHAT IS KNOWN ALREADY

Although mTOR, PPARγ and PPARδ are nutrient sensors important during implantation, the role of these signaling pathways in decidual function and how they interact in the early post-implantation period are unknown. Perilipin 2 (PLIN2) and fatty acid binding protein 4 (FABP4), two adipogenic proteins involved in lipid histotrophic nutrition, are targets of mTOR and PPAR signaling pathways in a variety of tissues.

STUDY DESIGN, SIZE, DURATION

Rapamycin (mTOR inhibitor, 0.75 mg/kg, sc), T0070907 (PPARγ inhibitor, 0.001 mg/kg, sc), GSK0660 (PPARδ inhibitor, 0.1 mg/kg, sc) or vehicle was injected daily to pregnant rats from Days 7 to 9 of pregnancy and the studies were performed on Day 9 of pregnancy (n = 7 per group) or Day 14 of pregnancy (n = 7 per group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

On Day 9 of pregnancy, rat decidua were collected and prepared for western blot and immunohistochemical studies. On Day 14 of pregnancy, the resorption rate, number of viable fetuses, crown-rump length and placental and decidual weights were determined.

MAIN RESULTS AND THE ROLE OF CHANCE

Inhibition of mTOR in the early post-implantation period led to a reduction in FABP4 protein levels, an increase in PLIN2 levels and an upregulation of PPARγ and PPARδ in 9-day-pregnant rat decidua. Most embryos were viable on Day 9 of pregnancy but had resorbed by Day 14 of pregnancy. This denotes a key function of mTOR in the post-implantation period and suggests that activation of PPAR signaling was insufficient to compensate for impaired nutritional/survival signaling induced by mTOR inhibition. Inhibition of PPARγ signaling resulted in decreased decidual PLIN2 and FABP4 protein expression as well as in inhibition of decidual mTOR signaling in Day 9 of pregnancy. This treatment also reduced feto-placental growth on Day 14 of pregnancy, revealing the relevance of PPARγ signaling in sustaining post-implantation growth. Moreover, following inhibition of PPARδ, PLIN2 levels were decreased and mTOR complex 1 and 2 signaling was altered in decidua on Day 9 of pregnancy. On Day 14 of pregnancy, PPARδ inhibition caused reduced feto-placental weight, increased decidual weight and increased resorption rate, suggesting a key role of PPARδ in sustaining post-implantation development.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

This is an in vivo animal study and the relevance of the results for humans remains to be established.

WIDER IMPLICATIONS OF THE FINDINGS

The early post-implantation period is a critical window of development and changes in the intrauterine environment may cause embryo resorption and lead to placental and fetal growth restriction. mTOR, PPARγ and PPARδ signaling are decidual nutrient sensors with extensive cross-talk that regulates adipogenic proteins involved in histotrophic nutrition and important for embryo viability and early placental and fetal development and growth.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided by the Agencia Nacional de Promoción Científica y Tecnológica de Argentina (PICT 2014-411 and PICT 2015-0130), and by the International Cooperation (Grants CONICET-NIH-2014 and CONICET-NIH-2017) to A.J. and T.J. The authors have no conflicts of interest.

Regulation of expression and role of peroxisome proliferator-activated receptors (PPARs) in luminal epithelial and stromal cells of the porcine endometrium

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family of ligand-dependent transcription factors. PPARs are important regulators of glucose and fatty acid metabolism, apoptosis, angiogenesis, cell proliferation and differentiation, and immune response. Their possible role in the female reproductive tract was demonstrated. In the present study, cultured luminal epithelial (LE) and stromal (ST) cells of the porcine endometrium were used to examine (1) the effect of conceptus exposed medium (CEM) on mRNA and protein expression and DNA binding activity of PPARA, PPARD, and PPARG isoforms, and (2) the effect of PPARA, PPARD, and PPARG agonists on the expression of selected genes, apoptosis, and cell proliferation. The addition of CEM stimulated PPARA expression and DNA binding activity of this isoform in LE and ST cells (P < 0.05). Increased expression of PPARD mRNA in the presence of CEM was detected in ST cells (P < 0.05), while the concentration of PPARG transcripts decreased in response to CEM in both cell types (P < 0.05). LE and ST cells of the pig endometrium possess PPARA, PPARD, and PPARG proteins, with clear nuclear staining visible predominately in ST cells. In LE cells, activation of PPARG with 15-deoxy-Δ12,14-prostaglandin(PG)J2 down-regulated the expression of genes encoding amino acid transporter 1 (SLC38A1), leukemia inhibitory factor (LIF) and enzymes involved in PG synthesis (P < 0.05). In ST cells, activation of PPARD isoform with both agonists used (L-165,041 and cPGI2) and PPARG isoform with 15-deoxy-Δ12,14-PGJ2 increased vascular endothelial growth factor A (VEGFA) mRNA expression (P < 0.05). Moreover, GW9578 (PPARA agonist) and 15-deoxy-Δ12,14-PGJ2 stimulated glucose transporter 1 (SLC2A1) gene expression in ST cells. 15-deoxy-Δ12,14-PGJ2 was also effective in up-regulation of the ratio of BAX/BCL2 mRNA expression and active caspase-3 concentration in ST cells (P < 0.05). Finally, GW9578 stimulated LE and ST cell proliferation, while rosiglitazone (PPARG agonist) increased the number of viable ST but not LE cells. In conclusion, this study demonstrated that conceptus products differentially modulate PPARs expression and activity in the porcine endometrium. Activation of PPARs may in turn affect nutrient transport, PG synthesis, angiogenesis, apoptosis, or cell proliferation in this tissue. Therefore, PPAR isoforms seem to play an important role in development and function of the porcine uterus.

Diverse endometrial mRNA signatures during the window of implantation in patients with repeated implantation failure

High endometrial receptivity in the window of implantation (WOI) is essential for successful implantation. However, a diagnostic tool with high specificity for impaired endometrial receptivity remains to be developed. We collected endometrium specimens during the WOI from patients with RIF and women who conceived after one IVF/ICSI attempt. We conducted mRNA microarray on the samples followed by relevant comparative and functional analysis. Microarray analysis revealed 357 dysregulated mRNAs between the two groups. The majority of these mRNAs were found to encode membrane proteins by Gene Ontology (GO) analysis. The major functional biological pathways associated with the down-regulated mRNAs were cytokine-cytokine receptor interaction, the p53 signalling pathway and the complement and coagulation cascades. Up-regulated mRNAs were found mainly to participate in pathways such as PPAR signalling, hematopoietic cell lineage, phosphatidylinositol signalling system, ECM-receptor interaction and notch signalling. AQP3, DPP4 and TIMP3 whose expression patterns were down-regulated in RIF patients both by microarray and real-time PCR had a high correspondence with previous studies demonstrating that these genes may contribute to the defects in endometrial receptivity in RIF patients. Overall, these RIF-associated mRNAs may help devise new diagnostic tools for endometrial receptivity.

The peroxisome proliferator-activated receptors under epigenetic control in placental metabolism and fetal development

The placental metabolism can adapt to the environment throughout pregnancy to both the demands of the fetus and the signals from the mother. Such adaption processes include epigenetic mechanisms, which alter gene expression and may influence the offspring's health. These mechanisms are linked to the diversity of prenatal environmental exposures, including maternal under- or overnutrition or gestational diabetes. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that contribute to the developmental plasticity of the placenta by regulating lipid and glucose metabolism pathways, including lipogenesis, steroidogenesis, glucose transporters, and placental signaling pathways, thus representing a link between energy metabolism and reproduction. Among the PPAR isoforms, PPARγ appears to be the main modulator of mammalian placentation. Certain fatty acids and lipid-derived moieties are the natural activating PPAR ligands. By controlling the amounts of maternal nutrients that go across to the fetus, the PPARs play an important regulatory role in placenta metabolism, thereby adapting to the maternal nutritional status. As demonstrated in animal studies, maternal nutrition during gestation can exert long-term influences on the PPAR methylation pattern in offspring organs. This review underlines the current state of knowledge on the relationship between environmental factors and the epigenetic regulation of the PPARs in placenta metabolism and offspring development.

Sustained Endocannabinoid Signaling Compromises Decidual Function and Promotes Inflammation-induced Preterm Birth

Recent studies provide evidence that premature maternal decidual senescence resulting from heightened mTORC1 signaling is a cause of preterm birth (PTB). We show here that mice devoid of fatty acid amide hydrolase (FAAH) with elevated levels ofN-arachidonyl ethanolamide (anandamide), a major endocannabinoid lipid mediator, were more susceptible to PTB upon lipopolysaccharide (LPS) challenge. Anandamide is degraded by FAAH and primarily works by activating two G-protein-coupled receptors CB1 and CB2, encoded by Cnr1 and Cnr2, respectively. We found thatFaah(-/-)decidual cells progressively underwent premature senescence as marked by increased senescence-associated β-galactosidase (SA-β-Gal) staining and γH2AX-positive decidual cells. Interestingly, increased endocannabinoid signaling activated MAPK p38, but not p42/44 or mTORC1 signaling, inFaah(-/-)deciduae, and inhibition of p38 halted premature decidual senescence. We further showed that treatment of a long-acting anandamide in wild-type mice at midgestation triggered premature decidual senescence utilizing CB1, since administration of a CB1 antagonist greatly reduced the rate of PTB inFaah(-/-)females exposed to LPS. These results provide evidence that endocannabinoid signaling is critical in regulating decidual senescence and parturition timing. This study identifies a previously unidentified pathway in decidual senescence, which is independent of mTORC1 signaling.

The effect of neuronal conditional knock-out of peroxisome proliferator-activated receptors in the MPTP mouse model of Parkinson's disease

Activation of peroxisome proliferator-activated receptors (PPARs), namely PPARγ and PPARδ, has been shown to provide neuroprotection in a number of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease (PD). The observed neuroprotective effects in experimental models of PD have been linked to anti-oxidant and anti-inflammatory actions. This study aimed to analyze the full influence of these receptors in neuroprotection by generating a nerve cell-specific conditional knock-out of these receptors and subjecting these genetically modified mice to the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin to model dopaminergic degeneration. Mice null for both receptors show the lowest levels of tyrosine hydroxylase (TH)-positive cell bodies following MPTP administration. Presence of one or both these receptors show a trend toward protection against this degeneration, as higher dopaminergic cell immunoreactivity and striatal monoamine levels are evident. These data supplement recent studies that have elected to use agonists of the receptors to regulate immune responses. The results place further importance on the activation of PPARs and the neuroprotective roles these have in inflammatory processes linked to neurodegenerative processes.

Peroxisome proliferator-activated receptorβ/δ activation is essential for modulating p-Foxo1/Foxo1 status in functional insulin-positive cell differentiation

Peroxisome proliferator-activated receptors (PPARs) participate in energy homeostasis and play essential roles in diabetes therapy through their effects on non-pancreas tissues. Pathological microenvironment may influence the metabolic requirements for the maintenance of stem cell differentiation. Accordingly, understanding the mechanisms of PPARs on pancreatic β-cell differentiation may be helpful to find the underlying targets of disrupted energy homeostasis under the pancreatic disease condition. PPARs are involved in stem cell differentiation via mitochondrial oxidative phosphorylation, but the subtype member activation and the downstream regulation in functional insulin-positive (INS⁺) cell differentiation remain unclear. Here, we show a novel role of PPARβ/δ activation in determining INS⁺ cell differentiation and functional maturation. We found PPARβ/δ expression selectively upregulated in mouse embryonic pancreases or stem cells-derived INS⁺ cells at the pancreatic mature stage in vivo and in vitro. Strikingly, given the inefficiency of generating INS⁺ cells in vitro, PPARβ/δ activation displayed increasing mouse and human ES cell-derived INS⁺ cell numbers and insulin secretion. This phenomenon was closely associated with the forkhead box protein O1 (Foxo1) nuclear shuttling, which was dependent on PPARβ/δ downstream PI3K/Akt signaling transduction. The present study reveals the essential role of PPARβ/δ activation on p-Foxo1/Foxo1 status, and in turn, determining INS⁺ cell generation and insulin secretion via affecting pancreatic and duodenal homeobox-1 expression. The results demonstrate the underlying mechanism by which PPARβ/δ activation promotes functional INS⁺ cell differentiation. It also provides potential targets for anti-diabetes drug discovery and hopeful clinical applications in human cell therapy.

Effects of maternal dietary olive oil on pathways involved in diabetic embryopathy

Maternal diabetes induces a pro-oxidant/pro-inflammatory intrauterine environment related to the induction of congenital anomalies. Peroxisome proliferator activated receptors (PPARs) are transcription factors that regulate antioxidant and anti-inflammatory pathways. We investigated whether maternal diets supplemented with olive oil, enriched in oleic acid, a PPAR agonist, can regulate the expression of PPAR system genes, levels of lipoperoxidation and activity of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) in embryos and decidua from diabetic rats. The embryos and decidua from diabetic rats showed reduced expression of PPARs and increased concentration of lipoperoxidation, MMPs and TIMPs, whereas the maternal treatments enriched in olive oil increased PPARδ in embryos and PPARγ and PPARγ-coactivator-1α expression in decidua, and increased TIMPs concentrations and decreased lipoperoxidation and MMPs activity in both tissues. Thus, maternal diets enriched in olive oil can regulate embryonic and decidual PPAR system genes expression and reduce the pro-oxidant/pro-inflammatory environment during rat early organogenesis.

Role of Peroxisome Proliferator-Activated Receptor (PPAR)δ in Embryonic Stem Cell Proliferation

The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear receptor family. It is well known that PPARs function as regulators of lipid and lipoprotein metabolism and glucose homeostasis, as well as influence cellular proliferation, differentiation and apoptosis. However, the role of the PPARs with regard to embryonic stem (ES) cells remains unknown. We will review the function of the PPARδ, one of the three PPAR isoforms, α, δ (also called β/δ), and γ, in ES cells and its role in embryo development. In addition, pluripotent mouse ES cells can be expanded in large numbers in vitro due to the process of symmetrical self-renewal. Here we describe how PPARδ sustains ES cell proliferation.

Towards an understanding of the molecular mechanism of endometriosis: unbalancing epithelial-stromal genetic conflict

OBJECTIVES

Despite the high incidence of endometriosis, the etiology is poorly understood. Much work has been carried out to elucidate the genetic basis of endometriosis owing to the advent of genomic analysis and new network-based analysis methods.

METHODS

This article reviews the English literature for (epi)genome-wide profiling and association studies on the pathogenesis and pathophysiology of endometriosis.

RESULTS

The characteristic 82 up- and 45 down-regulated unique genes in endometriosis included genes encoding cell cycle, growth factors, signal transduction, transcription factors, hormones, cytokines, chemokines and (pro)inflammation, proteases, cell adhesion and motility, stress response and detoxification, immune response, metabolism and others. There appear to be at least two types of genes: some genes (n = 50) may evolve mainly for the benefit of the endometrial growth, and the other genes (n = 55) evolve as a protective mechanism for the endometrial decidualization. The present review has shed new light on the overlapping genetic signatures between endometriosis development and decidualization process.

CONCLUSION

In conclusion, insufficient decidualization due to unbalancing epithelial-stromal genetic conflict may result in future endometriosis.

PPAR activation as a regulator of lipid metabolism, nitric oxide production and lipid peroxidation in the placenta from type 2 diabetic patients

Peroxisome proliferator activated receptors (PPARs) are ligand activated transcription factors with crucial functions in lipid homeostasis, anti-inflammatory processes and placental development. Maternal diabetes induces a pro-inflammatory environment and alters placental development. We investigated whether PPARs regulate lipid metabolism and nitric oxide (NO) production in placental explants from healthy and type 2 diabetic (DM2) patients. We found decreased PPARα and PPARγ concentrations, no changes in PPARδ concentrations, and increased lipids, lipoperoxides and NO production in placentas from DM2 patients. PPARα agonists reduced placental concentrations of triglycerides and both PPARα and PPARδ agonists reduced concentrations of phospholipids, cholesteryl esters and cholesterol. PPARγ agonists increased lipid concentrations in placentas from DM2 patients and more markedly in placentas from healthy patients. Endogenous ligands for the three PPAR isotypes reduced NO production and lipoperoxidation in placentas from DM2 patients. We conclude that PPARs play a role in placental NO and lipid homeostasis and can regulate NO production, lipid concentrations and lipoperoxidation in placentas from DM2 patients.

Role of nuclear receptors in blastocyst implantation

The regulation of blastocyst implantation in the uterus is orchestrated by the ovarian hormones estrogen and progesterone. These hormones act via their nuclear receptors to direct the transcriptional activity of the endometrial compartments and create a defined period in which the uterus is permissive to embryo implantation termed the "window of receptivity". Additional members of the nuclear receptor family have also been described to have a potential role in endometrial function. Much of what we know about the function of these nuclear receptors during implantation we have learned from the use of mouse models. Transgenic murine models with targeted gene ablation have allowed us to identify a complex network of paracrine signaling between the endometrial epithelium and stroma. While some of the critical molecules have been identified, the mechanism underlying the intricate communication between endometrial compartments during the implantation window has not been fully elucidated. Defining this mechanism will help identify markers of a receptive uterine environment, ultimately providing a useful tool to help improve the fertility outlook for reproductively challenged couples. The aim of this review is to outline our current understanding of how nuclear receptors and their effector molecules regulate blastocyst implantation in the endometrium.

The Role of PPARs in Placental Immunology: A Systematic Review of the Literature

Pregnancy is a state of immunotolerance, and pregnancy outcome is strongly linked to the correct activation and balancing of the maternal immune system. Besides abortion as possible result of improper early pregnancy development, other pregnancy associated conditions like preeclampsia (PE), intrauterine growth retardation (IUGR), preterm labour, or gestational diabetes mellitus (GDM) are linked to immunologic overactivation and dysregulation. Both the innate and the adaptive immune system, and therefore B and T lymphocytes, natural killer cells (NK), macrophages and dendritic cells (DCs) are all involved in trophoblast invasion, pregnancy maintenance, and development of pregnancy disorders. Peroxisome proliferator activated receptors (PPARs) are nuclear transcription factors with three known isotypes: PPARα, PPARβ/δ, and PPARγ. They are expressed in most human organs and their function extends from regulating metabolism, homeostasis, and carcinogenesis to immune response. In the recent years, PPARs have been identified in most reproductive tissues and in all lines of immune cells. Only in few cases, the role of PPARs in reproductive immunology has been elucidated though the role of PPARs in immune answer and immunotolerance is evident. Within this paper we would like to give an update on today's knowledge about PPARs and immune cells in reproduction and highlight interesting interferences in regard of future therapeutic targets.

A peroxisome proliferator-activated receptor-δ agonist provides neuroprotection in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease

Peroxisome proliferator-activated receptor (PPAR)-γ and PPARα have shown neuroprotective effects in models of Parkinson's disease (PD). The role of the third, more ubiquitous isoform PPARδ has not been fully explored. This study investigated the role of PPARδ in PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to model the dopaminergic neurodegeneration of PD. In vitro administration of the PPARδ antagonist GSK0660 (1 μM) increased the detrimental effect of 1-methyl-4-phenylpyridinium iodide (MPP⁺) on cell viability, which was reversed by co-treatment with agonist GW0742 (1 μM). GW0742 alone did not affect MPP⁺ toxicity. PPARδ was expressed in the nucleus of dopaminergic neurons and in astrocytes. Striatal PPARδ levels were increased (over two-fold) immediately after MPTP treatment (30 mg/kg for 5 consecutive days) compared to saline-treated mice. PPARδ heterozygous mice were not protected against MPTP toxicity. Intra-striatal infusion of GW0742 (84 μg/day) reduced the MPTP-induced loss of dopaminergic neurons (5036±195) when compared to vehicle-infused mice (3953±460). These results indicate that agonism of PPARδ provides protection against MPTP toxicity, in agreement with the effects of other PPAR agonists.

Mechanisms of implantation: strategies for successful pregnancy

Physiological and molecular processes initiated during implantation for pregnancy success are complex but highly organized. This review primarily highlights adverse ripple effects arising from defects during the peri-implantation period that perpetuate throughout pregnancy. These defects are reflected in aberrations in embryo spacing, decidualization, placentation and intrauterine embryonic growth, manifesting in preeclampsia, miscarriages and/or preterm birth. Understanding molecular signaling networks that coordinate strategies for successful implantation and decidualization may lead to approaches to improve the outcome of natural pregnancy and pregnancy conceived from in vitro fertilization.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Deciphering the molecular basis of uterine receptivity

Uterine receptivity is defined as a limited time period during which the uterus enters into an appropriately differentiated state that is ready for the initiation of implantation by competent blastocysts. Although various cellular aspects and molecular pathways involved in uterine receptivity have been identified by gene expression studies and genetically engineered mouse models, a comprehensive understanding of the window of uterine receptivity is still missing. This review focuses on the recent progress in this area, with particular focus on the molecular basis of stromal-epithelial dialogue and crosstalk between the blastocyst and the uterus during implantation. A better understanding of the underlying mechanisms governing the window of uterine receptivity is hoped to generate new strategies to correct implantation failure and to improve pregnancy rates in women.

Silencing or amplification of endocannabinoid signaling in blastocysts via CB1 compromises trophoblast cell migration

Endocannabinoid signaling plays key roles in multiple female reproductive events. Previous studies have shown an interesting phenomenon, that mice with either silenced or elevated endocannabinoid signaling via Cnr1 encoding CB(1) show similar defects in several pregnancy events, including preimplantation embryo development. To unravel the downstream signaling of this phenomenon, microarray studies were performed using RNAs collected from WT, Cnr1(-/-), and Faah(-/-) mouse blastocysts on day 4 of pregnancy. The results indicate that about 100 genes show unidirectional changes under either silenced or elevated anandamide signaling via CB(1). Functional enrichment analysis of the microarray data predicted that multiple biological functions and pathways are affected under aberrant endocannabinoid signaling. Among them, genes enriched in cell migration are suppressed in Cnr1(-/-) or Faah(-/-) blastocysts. Cell migration assays validated the prediction of functional enrichment analysis that cell mobility and spreading of either Cnr1(-/-) or Faah(-/-) trophoblast stem cells are compromised. Either silenced or elevated endocannabinoid signaling via CB(1) causes similar changes in downstream targets in preimplantation embryos and trophoblast stem cells. This study provides evidence that a tightly regulated endocannabinoid signaling is critical to normal preimplantation embryo development and migration of trophoblast stem cells.

Leucine and arginine regulate trophoblast motility through mTOR-dependent and independent pathways in the preimplantation mouse embryo

Uterine implantation is a critical element of mammalian reproduction and is a tightly and highly coordinated event. An intricate and reciprocal uterine-embryo dialog exists to synchronize uterine receptivity with the concomitant activation of the blastocyst, maximizing implantation success. While a number of pathways involved in regulating uterine receptivity have been identified in the mouse, less is understood about blastocyst activation, the process by which the trophectoderm (TE) receives extrinsic cues that initiate new characteristics essential for implantation. Amino acids (AA) have been found to regulate blastocyst activation and TE motility in vitro. In particular, we find that arginine and leucine alone are necessary and sufficient to induce TE motility. Both arginine and leucine act individually and additively to propagate signals that are dependent on the activity of the mammalian target of rapamycin complex 1 (mTORC1). The activities of the well-established downstream targets of mTORC1, p70S6K and 4EBP, do not correlate with trophoblast motility, suggesting that an independent-rapamycin-sensitive pathway operates to induce trophoblast motility, or that other, parallel amino acid-dependent pathways are also involved. We find that endogenous uterine factors act to induce mTORC1 activation and trophoblast motility at a specific time during pregnancy, and that this uterine signal is later than the previously defined signal that induces the attachment reaction. In vivo matured blastocysts exhibit competence to respond to an 8-hour AA stimulus by activating mTOR and subsequently undergoing trophoblast outgrowth by the morning of day 4.5 of pregnancy, but not on day 3.5. By the late afternoon of day 4.5, the embryos no longer require any exposure to AA to undergo trophoblast outgrowth in vitro, demonstrating the existence and timing of an equivalent in vivo signal. These results suggest that there are two separate uterine signals regulating implantation, one that primes the embryo for the attachment reaction and another that activates mTOR and initiates invasive behavior.

Reduced signaling through the hedgehog pathway in the uterine stroma causes deferred implantation and embryonic loss

The role of the hedgehog (HH) signaling pathway in implantation was studied in mice in which the HH signal transducer, smoothened (SMO), was conditionally deleted in the stromal compartment of the uterus, using CRE recombinase expressed through the Amhr2cre allele. In Amhr2cre/+Smonull/flox-mutant mice, Smo mRNA in uterine stroma was reduced 49% compared to that in Amhr2+/+Smonull/flox control mice, while levels in the luminal epithelium were not different. Litter size was reduced 60% in mutants compared with controls, but ovulation rate and the number of implantation sites on day 7 of pregnancy did not differ. The number of corpora lutea was equivalent to the number of implantation sites, indicating that most ovulations resulted in implanted embryos. However, on days 13 to 15, the rate of embryo resorption was elevated in mutants. In control mice, on day 5, implantation sites were present and blastocysts were well-attached. In contrast, blastocysts were readily flushed from uteri of mutant mice on day 5 and implantation sites were rare. On days 5.5 and 6, implantation sites were present in mutant mice, and by day 6 embryos could not be flushed from the uterus. The weight of implantation sites on day 7 was decreased by 42% in mutant mice, consistent with delayed development. Signaling through SMO in the endometrial stroma is required for optimal timing of implantation, and deferred implantation leads to defective embryo development and subsequent pregnancy loss.

Activation of peroxisome proliferators-activated receptor δ (PPARδ) promotes blastocyst hatching in mice

Prostaglandins participate in a variety of female reproductive processes, including ovulation, fertilization, embryo implantation and parturition. In particular, maternal prostacyclin (PGI(2)) is critical for embryo implantation and the action of PGI(2) is not mediated via its G-protein-coupled membrane receptor, IP, but its nuclear receptor, peroxisome-proliferator-activated receptor δ (PPARδ). Recently, several studies have shown that PGI(2) enhances blastocyst development and/or hatching rate in vitro, and subsequently implantation and live birth rates in mice. However, the mechanism by which PGI(2) improves preimplantation embryo development in vitro remains unclear. Using molecular, pharmacologic and genetic approaches, we show that PGI(2)-induced PPARδ activation accelerates blastocyst hatching in mice. mRNAs for PPARδ, retinoid X receptor (heterodimeric partners of PPARδ) and PGI(2) synthase (PGIS) are temporally induced after zygotic gene activation, and their expression reaches maximum levels at the blastocyst stage, suggesting that functional complex of PPARδ can be formed in the blastocyst. Carbaprostacyclin (a stable analogue of PGI(2)) and GW501516 (a PPARδ selective agonist) significantly accelerated blastocyst hatching but did not increase total cell number of cultured blastocysts. Whereas U51605 (a PGIS inhibitor) interfered with blastocyst hatching, GW501516 restored U51605-induced retarded hatching. In contrast to the improvement of blastocyst hatching by PPARδ agonists, PPAR antagonists significantly inhibited blastocyst hatching. Furthermore, deletion of PPARδ at early stages of preimplantation mouse embryos caused delay of blastocyst hatching, but did not impair blastocyst development. Taken together, PGI(2)-induced PPARδ activation accelerates blastocyst hatching in mice.

Uterine disorders and pregnancy complications: insights from mouse models

Much of our knowledge of human uterine physiology and pathology has been extrapolated from the study of diverse animal models, as there is no ideal system for studying human uterine biology in vitro. Although it remains debatable whether mouse models are the most suitable system for investigating human uterine function(s), gene-manipulated mice are considered by many the most useful tool for mechanistic analysis, and numerous studies have identified many similarities in female reproduction between the two species. This Review brings together information from studies using animal models, in particular mouse models, that shed light on normal and pathologic aspects of uterine biology and pregnancy complications.

Uterine-specific p53 deficiency confers premature uterine senescence and promotes preterm birth in mice

Many signaling pathways that contribute to tumorigenesis are also functional in pregnancy, although they are dysregulated in the former and tightly regulated in the latter. Transformation-related protein 53 (Trp53), which encodes p53, is a tumor suppressor gene whose mutation is strongly associated with cancer. However, its role in normal physiological processes, including female reproduction, is poorly understood. Mice that have a constitutive deletion of Trp53 exhibit widespread development of carcinogenesis at early reproductive ages, compromised spermatogenesis, and fetal exencephaly, rendering them less amenable to studying the role of p53 in reproduction. To overcome this obstacle, we generated mice that harbor a conditional deletion of uterine Trp53 and examined pregnancy outcome in females with this genotype. These mice had normal ovulation, fertilization, and implantation; however, postimplantation uterine decidual cells showed terminal differentiation and senescence-associated growth restriction with increased levels of phosphorylated Akt and p21, factors that are both known to participate in these processes in other systems. Strikingly, uterine deletion of Trp53 increased the incidence of preterm birth, a condition that was corrected by oral administration of the selective COX2 inhibitor celecoxib. We further generated evidence to suggest that deletion of uterine Trp53 induces preterm birth through a COX2/PGF synthase/PGF(2alpha) pathway. Taken together, our observations underscore what we believe to be a new critical role of uterine p53 in parturition.

Gene expression during successful implantation in a natural cycle

OBJECTIVE

To determine the human endometrial transcriptome during embryonic implantation.

DESIGN

Case report.

SETTING

Tertiary fertility center.

PATIENT(S)

A 24-year-old woman who inadvertently became pregnant during an endometrial biopsy procedure.

INTERVENTION(S)

An endometrial biopsy was performed with a Pipelle device during the midluteal phase (days 19-21) of the cycle; blood samples for hormonal assessments were collected and a transvaginal ultrasound was performed.

MAIN OUTCOME MEASURE(S)

Gene expression analysis of the endometrium during the window of implantation (during the implantation of an embryo) in a natural cycle. Localization of selected genes in endometrial tissue with immunohistochemistry.

RESULT(S)

A total of 394 probe sets were differentially expressed in the pregnant sample when compared with the midsecretory phase nonpregnant endometrial samples. Different gene networks were involved, and selected genes from these signaling pathways were confirmed at the protein level.

CONCLUSION(S)

Endometrial gene expression of a pregnant patient in a natural cycle is significantly different from nonpregnant patients during the midsecretory phase.

The Potential Applications of Peroxisome Proliferator-Activated Receptor delta Ligands in Assisted Reproductive Technology

Peroxisome proliferator-activated receptor δ (PPARδ, also known as PPARβ) has ubiquitous distribution and extensive biological functions. The reproductive function of PPARδ was first revealed in the uterus at the implantation site. Since then, PPARδ and its ligand have been discovered in all reproductive tissues, including the gametes and the preimplantation embryos. PPARδ in preimplantation embryos is normally activated by oviduct-derived PPARδ ligand. PPARδ activation is associated with an increase in embryonic cell proliferation and a decrease in programmed cell death (apoptosis). On the other hand, the role of PPARδ and its ligand in gamete formation and function is less well understood. This review will summarize the reproductive functions of PPARδ and project its potential applications in assisted reproductive technology.

Expression patterns and role of prostaglandin-endoperoxide synthases, prostaglandin E synthases, prostacyclin synthase, prostacyclin receptor, peroxisome proliferator-activated receptor delta and retinoid x receptor alpha in rat endometrium during artificially-induced decidualization

To determine if changes in endometrial expression of the enzymes and receptors involved in prostaglandin (PG) synthesis and action might provide insights into the PGs involved in the initiation of decidualization, ovariectomized steroid-treated rats at the equivalent of day 5 of pseudopregnancy were given a deciduogenic stimulus and killed at various times up to 32 h thereafter. The expression of PG-endoperoxide synthases (PTGS1 and PTGS2), microsomal PGE synthases (PTGES and PTGES2), cytosolic PGE synthase (PTGES3), prostacyclin synthase (PTGIS), prostacyclin receptor, peroxisome proliferator-activated receptor delta (PPARD) and retinoid x receptor alpha (RXRA) in endometrium was assessed by semiquantitative RT-PCR, western blot analyses and immunohistochemistry. In addition, to determine which PG is involved in mediating decidualization, we compared the ability of PGE(2), stable analogues of PGI(2), L165041 (an agonist of PPARD), and docasahexanoic acid (an agonist of RXRA) to increase endometrial vascular permeability (EVP, an early event in decidualization), and decidualization when infused into the uterine horns of rats sensitized for the decidual cell reaction (DCR). EVP was assessed by uterine concentrations of Evans blue 10 h after initiation of infusions. DCR was assessed by the uterine mass 5 days after the initiation of the infusions. Because enzymes associated with the synthesis of PGE(2), including PTGS2, are up-regulated in response to a deciduogenic stimulus and because PGE(2) was more effective than the PGI(2) analogues and PPARD and RXRA agonists in increasing EVP and inducing decidualization, we suggest that PGE(2) is most likely the PG involved in the initiation of decidualization in the rat.

Deficiency of immunophilin FKBP52 promotes endometriosis

Endometriosis is a common gynecological disease that affects approximately 10% of women of childbearing age. It is characterized by endometrial growth outside the uterus and often results in inflamed lesions, pain, and reduced fertility. Although heightened estrogenic activity and/or reduced progesterone responsiveness are considered to be involved in the etiology of endometriosis, neither the extent of their participation nor the underlying mechanisms are clearly understood. Heterogeneous uterine cell types differentially respond to estrogen and progesterone (P(4)). P(4), primarily acting via its nuclear receptor (PR), activates gene transcription and impacts many reproductive processes. Deletion of Fkbp52, an immunophilin cochaperone for PR, results in uterine-specific P(4) resistance in mice, creating an opportunity to study the unique aspects of P(4) signaling in endometriosis. Here we explored the roles of FKBP52 in this disease using Fkbp52(-/-) mice. We found that the loss of FKBP52 encourages the growth of endometriotic lesions with increased inflammation, cell proliferation, and angiogenesis. We also found remarkable down-regulation of FKBP52 in cases of human endometriosis. Our results provide the first evidence corroborated by genetic studies in mice for a potential role of an immunophilin cochaperone in the etiology of human endometriosis. This investigation is highly relevant for clinical application, particularly because P(4) resistance is favorably indicated in endometriosis and other gynecological diseases.

PPAR-gamma signaling pathway in placental development and function: a potential therapeutic target in the treatment of gestational diseases

BACKGROUND

PPAR-gamma is a target for the treatment of metabolic disorders, as Pioglitazone and Rosiglitazone are already used against type 2 diabetes. Pleiotropic functions, such as antiproliferative and anti-inflammatory effects against several pathological states, including cardiovascular disease and cancer, are currently being explored in clinical studies.

OBJECTIVE

Evidence indicates that PPAR-gamma is expressed in the placenta, playing a crucial role in placental development and function, while PPAR-gamma ligands appear to modulate fetal membrane signals. Thus, in the last few years, the pivotal role of PPAR-gamma in placental biology has been the focus of extensive research, as diabetes appears to be the most common metabolic dysfunction in pregnancy.

METHODS

We aim to present data concerning the expression of PPAR-gamma in animal and human placenta, underlining its significance in normal placental development and several gestational diseases. The effects of PPAR-gamma ligands as modulators of placental biology in normal and certain pathological conditions are also discussed.

RESULTS/CONCLUSION

Current research provides substantial evidence that PPAR-gamma plays a pivotal role in placental biology and may reveal new perspectives in the treatment of gestational diseases.