Developmental Programming: Gestational Exposure to Excess Testosterone Alters Expression of Ovarian Matrix Metalloproteases and Their Target Proteins

Gap junctions in polycystic ovary syndrome: Implications for follicular arrest

Gap junctions are specialized intercellular conduits that provide a direct pathway between neighboring cells, which are involved in numerous physiological processes, such as cellular differentiation, cell growth, and metabolic coordination. The effect of gap junctional hemichannels in folliculogenesis is particularly obvious, and the down-regulation of connexins is related to abnormal follicle growth. Polycystic ovary syndrome (PCOS) is a ubiquitous endocrine disorder of the reproductive system, affecting the fertility of adult women due to anovulation. Exciting evidence shows that gap junction is involved in the pathological process related to PCOS and affects the development of follicles in women with PCOS. In this review, we examine the expression of connexins in follicular cells of PCOS and figure out whether such communication could have consequences for PCOS women. While along with results from clinical and related animal studies, we summarize the mechanism of connexins involved in the pathogenesis of PCOS.

Insulin regulates gap junction intercellular communication in porcine granulosa cells through modulation of connexin43 protein expression

Gap junction intercellular communication (GJIC) among granulosa cells plays an important role in folliculogenesis, and it is temporal-spatially regulated during follicular development. Connexin (Cx) proteins predominantly form the basal structure of gap junctions in granulosa cells. In our study, immunohistochemical analysis revealed that Cx43 is the most widely expressed connexin in porcine follicles, especially among the large antral follicles. With application of insulin on porcine granulosa cells, we found that insulin significantly facilitated the protein level of Cx43, not mRNA level. This process is dependent on the phosphorylated activities of AKT and Erk since selective AKT and Erk inhibitors, LY294002 and U0126, respectively, hampered the potential of insulin to up-regulate Cx43 protein expression. As a consequence, the insulin-enhanced Cx43-couple GJIC activity in porcine granulosa cells was corresponding attenuated by the administration of LY294002 and U0126. Our findings provide a new insight into the molecular mechanisms by which insulin mediates cell-cell communication in porcine granulosa cells and sheds light on nutrition-reproduction interactions.

Sheep with ovarian androgen excess have fibrosis and follicular arrest with increased mRNA abundance for steroidogenic enzymes and gonadotropin receptors

An androgen excess ovarian micro-environment may limit follicle progression in sheep. Two populations of ewes with divergent follicular fluid androstenedione (A4) were identified in a flock in Jordan: High A4; (A4) ≥ 30 ng/mL, (N = 12) or Control A4 (Control); A4 ≤ 15 ng/mL; (N = 12). We hypothesized High A4 ewes would have increased steroidogenic enzyme mRNA abundance, inflammation, and follicular arrest. Messenger RNA abundance for steroidogenic enzymes StAR, CYP17A1, CYP11A1, and HSD3B1 were increased in theca cells while CYP17A1, CYP19A1, and HSD3B1 were increased in granulosa cells in High A4 ewes compared to Control. Gonadotropin receptor mRNA expression for LHCGR was increased in theca and FSHR in granulosa in High A4 ewes. Messenger RNA expression of FOS when reduced, increases expression of CYP17A1 which was observed in High A4 granulosa cells compared to Control. Furthermore, High A4 ewes had greater numbers of primordial follicles (P < 0.001) and fewer developing follicles compared to Control before, and after 7 d of culture, indicating follicular arrest was not alleviated by cortex culture. Increased fibrosis in the ovarian cortex was detected in High A4 ewes relative to Control (P < 0.001) suggesting increased inflammation and altered extracellular matrix deposition. Thus, this High A4 ewes population has similar characteristics to High A4 cows and women with polycystic ovary syndrome suggesting that naturally occurring androgen excess occurs in multiple species and may be a causative factor in follicular arrest and subsequent female sub- or infertility.

Naturally occurring androgen excess cows are present in dairy and beef herds and have similar characteristics to women with PCOS

Beef cows with excess androstenedione (A4; High A4) in follicular fluid (FF) and secreted by the ovarian cortex have been reported from the University of Nebraska-Lincoln physiology herd displaying characteristics reminiscent of polycystic ovary syndrome (PCOS). Thus, we hypothesized that naturally occurring High A4 cows were present in other dairy and beef herds. Fourteen Jordan (Amman, Jordon) dairy heifers and 16 U.S. Meat Animal Research Center beef heifers were classified by FF (High A4: A4 > 40 ng/mL and Control: A4 < 20 ng/mL) and/or cortex culture media (High A4 > 1 ng/mL/d or Control < 1 ng/mL/d). High A4 dairy heifers (n = 6) had greater A4 concentrations (7.6-fold) in FF and (98-fold) greater in ovarian cortex culture media with greater numbers of primordial and fewer later-stage follicles than Controls (n = 8) even after 7 d of culture. Also, the ovarian cortex had greater staining for Picro Sirius red in High A4 dairy heifers compared with Controls indicating increased fibrosis. Thecal cells from High A4 dairy heifers had greater STAR, LHCGR, CYP17A, CD68, and PECAM mRNA expression with increased mRNA abundance of CYP17A1 and CD68 in the ovarian cortex cultures compared with Control dairy heifers. Similarly, cortex culture media from High A4 beef heifers (n = 10) had increased A4 (290-fold; P ≤ 0.001), testosterone (1,427-fold; P ≤ 0.001), and progesterone (9-fold; P ≤ 0.01) compared with Control heifers with increased primordial follicles and decreased later-stage follicles even after 7 d of culture, indicating abnormal follicular development. High A4 ovarian cortex cultures from beef heifers also had increased fibrosis markers and greater expression of PECAM (P = 0.01) with a tendency for increased vascular endothelial cadherin compared with Controls (n = 6). These two trials support our hypothesis that naturally occurring androgen excess cows are present in other dairy and beef herds. The ability to identify these females that have excess A4 ovarian microenvironments may allow for their use in understanding factors causing abnormal follicle development linked to androgen excess and inflammation.

miR-130b regulates gap junctional intercellular communication through connexin 43 in granulosa cells from patients with polycystic ovary syndrome

MicroRNAs (miRNAs) are small, noncoding RNAs that negatively regulate gene expression post-transcriptionally. We explored whether connexin 43 (Cx43) was differently expressed in luteinized granulosa cells from women with polycystic ovary syndrome (PCOS) compared with luteinized granulosa cells from women with a normal menstrual cycle, and whether certain miRNAs regulate the Cx43 level and gap junctional intercellular communication (GJIC). The miRNA profile was investigated in ovarian cortex tissues from five women with PCOS and five women without PCOS using a miRNA microarray. The levels of miR-130b and Cx43 mRNA were measured using real-time PCR in human luteinized granulosa cells from 20 women with PCOS and 25 women without PCOS. Protein and mRNA expression analysis and luciferase assays were conducted to confirm the substrate of miR-130b. PCOS ovarian cortex showed differential expression of miRNAs compared with non-PCOS ovarian cortex. Furthermore, miR-130b levels were increased in PCOS ovarian cortex and in luteinized granulosa cells compared with those in women with normal menstrual cycles, whereas the level of Cx43 mRNA, the identified target of miR-130b, was decreased in granulosa cells from patients with PCOS. Overexpression of miR-130b in a granulosa cell line resulted in reduced Cx43 protein levels and inhibited GJIC using scrape loading and dye transfer assay. Meanwhile, inhibition of miR-130b increased the Cx43 level. In conclusion, miR-130b was increased in PCOS granulosa cells, where it targets Cx43 to affect GJIC. The results of the present study suggested that miR-130b, via post-transcriptional regulation of Cx43, is involved in the pathophysiology of PCOS, which provides new insight into the pathological mechanism of PCOS.

Developmental programming of the female reproductive system-a review

Exposures to adverse conditions in utero can lead to permanent changes in the structure and function of key physiological systems in the developing fetus, increasing the risk of disease and premature aging in later postnatal life. When considering the systems that could be affected by an adverse gestational environment, the reproductive system of developing female offspring may be particularly important, as changes have the potential to alter both reproductive capacity of the first generation, as well as health of the second generation through changes in the oocyte. The aim of this review is to examine the impact of different adverse intrauterine conditions on the reproductive system of the female offspring. It focuses on the effects of exposure to maternal undernutrition, overnutrition/obesity, hypoxia, smoking, steroid excess, endocrine-disrupting chemicals, and pollutants during gestation and draws on data from human and animal studies to illuminate underlying mechanisms. The available data indeed indicate that adverse gestational environments alter the reproductive physiology of female offspring with consequences for future reproductive capacity. These alterations are mediated via programmed changes in the hypothalamic-pituitary-gonadal axis and the structure and function of reproductive tissues, particularly the ovaries. Reproductive programming may be observed as a change in the timing of puberty onset and menopause/reproductive decline, altered menstrual/estrous cycles, polycystic ovaries, and elevated risk of reproductive tissue cancers. These reproductive outcomes can affect the fertility and fecundity of the female offspring; however, further work is needed to better define the possible impact of these programmed changes on subsequent generations.

Alternations in the expression of selected matrix metalloproteinases (MMP-2, -9, -10, and -13) and their tissue inhibitors (TIMP-2 and -3) and MMP-2 and -9 activity in the chicken ovary during pause in laying induced by fasting

Matrix metalloproteinases (MMPs) are a large group of proteolytic enzymes involved in extracellular matrix turnover in the ovary. Under physiological conditions, the activity of MMPs is controlled by specific tissue inhibitors of MMPs (TIMPs). Information concerning the role and regulation of MMPs in the chicken ovary is scarce. This study was undertaken to examine the expression of selected MMPs and their TIMPs in the chicken ovary during a pause in egg laying induced by feed deprivation. The activities of MMP-2 and MMP-9 were investigated as well. Real-time polymerase chain reaction and Western blot analyses showed changes in the expression of gelatinases (MMP-2, MMP-9), stromelysin (MMP-10), collagenase (MMP-13), TIMP-2, and TIMP-3 on mRNA and/or protein levels in the prehierarchical white (WFs) and yellowish (YFs) follicles, as well as in the largest yellow preovulatory (F3-F1) follicles. In feed-deprived hens, the occurrence of ovarian regression was accompanied by (1) a pronounced decrease in mRNA expression of the examined MMPs and TIMP-3 in all tissues except the YFs where the expression of MMP-13 was higher than in the control hen ovary; (2) an increase in the transcript abundance of TIMP-2 in the yellow atretic follicles; (3) a decrease or no changes in MMP-2 and MMP-9 protein expression in all tissues; (4) an increase in the total activity of gelatinases in the YFs and theca layer of F3; and (5) a decrease in the activity of MMP-2 in F3-F1 follicles and MMP-9 in the theca of F3. In summary, the results of the current study suggest that the selected MMPs and TIMPs may not be involved in the regulation of the advanced stages of atresia of the largest yellow preovulatory follicles in the chicken ovary. This event may require different cell signaling pathways.

Effect of two prostaglandin injections on days 5 and 6 in a timed AI protocol after estrus expression on pregnancy outcomes in dairy cows during cold or hot seasons of the year

The objective of this study was to test whether prostaglandin (PG) injection on day 30 postpartum (pp) and detection of estrus can affect the efficacy of injecting PG on days 5 and 6 in the timed artificial insemination (TAI) protocol on pregnancy rate in a large dairy herd in hot or cold seasons. Out of 2235 cows, 1998 received an injection of PG at 30±3 d pp and estrus was observed. Cows that displayed estrus during the estrous observation period after PG injection were classified as estrus (E), while those that did not show estrus were classified as nonestrus (NE). Cows in each group were assigned to two treatments: CO-72 (control treatment) (ECO-72 and NECO-72) (day 44 GnRH, day 51 PGF2α, day 54 GnRH+TAI) or PG–PG (EPG–PG and NEPG–PG) (day 44 GnRH, day 49 PGF2α, day 50 PGF2α, day 52 GnRH+TAI). Pregnancy was diagnosed on days 33 and 47 after artificial insemination (AI). The proportion of cows in estrus on the day of TAI was higher (P≤0.05) for cows that received two PG than for cows that received one PG. Pregnancies per AI (P/AI) on days 33 and 47 for cows inseminated during and after a voluntary waiting period in the NEPG–PG treatment had higher rates than for cows in the EPG–PG, ECO-72 and NECO-72 treatments. Moreover, P/AI were significantly (P≤0.05) affected by parity. Primiparous had higher P/AI (37.0 %) than multiparous cows (31.6 %). Cows inseminated in cold months had higher P/AI and reduced PL (35.6 % and 20.8 %) than cows inseminated in hot months (29.1 % and 30.6 %, respectively). In conclusion, treatments with PG on days 5 and 6 after the first GnRH injection increased P/AI. Estrus detection before the beginning of TAI protocol did not affect fertility. To maximize P/AI cows exhibiting heat at any time during the synchronization protocol should be inseminated.

Developmental Programming: Contribution of Epigenetic Enzymes to Antral Follicular Defects in the Sheep Model of PCOS

Prenatal testosterone (T)-treated sheep, similar to women with polycystic ovary syndrome (PCOS), manifest oligo-/anovulation, hyperandrogenism, and polyfollicular ovary. The polyfollicular ovarian morphology, a result of persistence of antral follicles, arises, in part, by transcriptional changes in key mediators of follicular development that, in turn, are driven by epigenetic mechanisms. We hypothesized that prenatal T excess induces, in a cell-specific manner, transcriptional changes in key mediators of follicular development associated with relevant changes in epigenetic machinery. Expression levels of key mediators of follicular development, DNA methyltransferases (DNMTs), and histone de-/methylases and de-/acetylases were determined in laser-capture microdissection-isolated antral follicular granulosa and theca and ovarian stromal cells from 21 months of age control and prenatal T-treated sheep (100 mg IM twice weekly from gestational day 30 to 90; term: 147 days). Changes in histone methylation were determined by immunofluorescence. Prenatal T treatment induced the following: (i) cell-specific changes in gene expression of key mediators of follicular development and steroidogenesis; (ii) granulosa, theca, and stromal cell-specific changes in DNMTs and histone de-/methylases and deacetylases, and (iii) increases in histone 3 trimethylation at lysine 9 in granulosa and histone 3 dimethylation at lysine 4 in theca cells. The pattern of histone methylation was consistent with the expression profile of histone de-/methylases in the respective cells. These findings suggest that changes in expression of key genes involved in the development of the polyfollicular phenotype in prenatal T-treated sheep are mediated, at least in part, by cell-specific changes in epigenetic-modifying enzymes.

DNA methylation in the pathogenesis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the leading endocrine and metabolic disorder in premenopausal women characterized by hyperandrogenism and abnormal development of ovarian follicles. To date, the PCOS etiology remains unclear and has been related to insulin resistance, obesity, type 2 diabetes mellitus, cardiovascular disease and infertility, among other morbidities. Substantial evidence illustrates the impact of genetic, intrauterine and environmental factors on the PCOS etiology. Lately, epigenetic factors have garnered considerable attention in the pathogenesis of PCOS considering that changes in the content of DNA methylation, histone acetylation and noncoding RNAs have been reported in various tissues of women with this disease. DNA methylation is changed in the peripheral and umbilical cord blood, as well as in ovarian and adipose tissue of women with PCOS, suggesting the involvement of this epigenetic modification in the pathogenesis of the disease. Perhaps, these defects in DNA methylation promote the deregulation of genes involved in inflammation, hormone synthesis and signaling and glucose and lipid metabolism. Research on the role of DNA methylation in the pathogenesis of PCOS is just beginning, and several issues await investigation. This review aims to provide an overview of current research focused on DNA methylation and PCOS, as well as discuss the perspectives regarding this topic.

Ovarian and Extra-Ovarian Mediators in the Development of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous endocrine disorder affecting women of reproductive age. The origin of PCOS is still not clear and appears to be a function of gene x environment interactions. This review addresses the current knowledge of the genetic and developmental contributions to the etiology of PCOS, the ovarian and extra-ovarian mediators of PCOS and the gaps and key challenges that need to be addressed in the diagnosis, treatment and prevention of PCOS.

Developmental Programming of Ovarian Functions and Dysfunctions

The pathophysiological mechanisms underlying the origin of several ovarian pathologies remain unclear. In addition to the genetic basis, developmental insults are gaining attention as a basis for the origin of these pathologies. Such early insults include maternal over or under nutrition, stress, and exposure to environmental chemicals. This chapter reviews the development and physiological function of the ovary, the known ovarian pathologies, the developmental check points of ovarian differentiation impacted by developmental insults, the role played by steroidal and metabolic factors as mediaries, the epigenetic mechanisms via which these mediaries induce their effects, and the knowledge gaps for targeting future studies to ultimately aid in the development of improved treatments.

Intrauterine Reprogramming of the Polycystic Ovary Syndrome: Evidence from a Pilot Study of Cord Blood Global Methylation Analysis

Polycystic ovary syndrome (PCOS) affects 5-15% of women. PCOS is a heterogeneous disorder displaying endocrine, metabolic, and reproductive dysfunction and cardiovascular risk manifestations. Evidence of heritability exists, but only a portion of the genetic transmission has been identified by genome-wide association studies and linkage studies, suggesting epigenetic phenomena may play a role. Evidence implicates intrauterine influences in the genesis of PCOS. This was a pilot study that aimed at identifying an epigenetic PCOS reprogramming signature by profiling the methylation of the DNA extracted from umbilical cord blood (UCB) from 12 subjects undergoing in vitro fertilization. Six subjects were anovulatory PCOS women diagnosed by Rotterdam criteria and six ovulatory non-PCOS women matched for age and body mass index. UCB was collected at delivery of the placenta; the DNA was extracted and submitted to methylation analysis. A differential methylation picture of prevalent hypomethylation affecting 918 genes was detected. Of these, 595 genes (64.8%) carried single or multiple hypomethylated CpG dinucleotides and 323 genes (35.2%) single or multiple hypermethylated CpG dinucleotides. The Ingenuity Pathway Analysis (IPA) online platform enlisted 908 of the 918 input genes and clustered 794 of them into 21 gene networks. Key features of the primary networks scored by IPA included carbohydrate and lipid metabolism, neurotransmitter signaling, cardiovascular system development and function, glycosaminoglycan signaling regulation and control of amino acid biosynthesis. Central to the network activities were genes controlling hormonal regulation (ESR1), mitochondrial activity (APP, PARK2), and glucose metabolism (INS). Regulatory pathways such as G-protein coupled receptor signaling, inositol metabolism, and inflammatory response were also highlighted. These data suggested the existence of a putative "PCOS epigenomic superpathway" with three main components: glucotoxic, lipotoxic, and inflammatory. If our results are confirmed, they hint at an epigenetic at risk PCOS "signature" may thus exist that may be identifiable at birth. Additional studies are needed to confirm the results of this pilot study.