Temporal expression of tenascin-C and type I collagen in response to gonadotropins in the immature rat ovary

Human TIMP1 Is a Growth Factor That Improves Oocyte Developmental Competence

Oocyte developmental competence is the ability of a mature oocyte to be fertilized and subsequently support embryonic development. Such competence is gained during folliculogenesis and is facilitated by the bidirectional communication into a compacted cumulus-oocyte complex (COC). Human tissue inhibitor of metalloproteinases-1 (TIMP1) participates in biological processes, including cell growth, differentiation, and apoptosis. This study aimed to evaluate the influence of TIMP1 as a growth factor on the in vitro maturation (IVM) culture of bovine COCs to improve oocyte developmental competence. All TIMP1 treatments (50, 100, and 150 ng/mL) favored the COCs' compaction structure (p < 0.05). TIMP1 at 150 ng/mL produced more oocytes in metaphase II compared to the other treatments (p < 0.05). The 150 ng/mL TIMP1 generated oocytes with the most (p < 0.05) cortical granules below the plasma membrane (pattern I). In a parthenogenesis assay, oocyte IVM in 50 ng/mL of TIMP1 produced the most blastocyst compared to the other treatments (p < 0.05). The Principal Component Analysis (PCA) showed that 50 ng/mL of TIMP1 was the best condition to develop oocyte competence because it was associated with the COC compact and cortical granule pattern I. TIMP1 influences the development of oocyte competence when added to the IVM culture medium of COCs.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility

BACKGROUND

Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage.

OBJECTIVE AND RATIONALE

This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility.

SEARCH METHODS

For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis.

OUTCOMES

Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI.

WIDER IMPLICATIONS

The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

The p38 signaling pathway mediates the TGF-β1-induced increase in type I collagen deposition in human granulosa cells

Type I collagen, which is mainly composed of collagen type I alpha 1 chain (COL1A1), is the most abundant extracellular matrix (ECM) protein in the mammalian ovary; and the cyclical remodeling of the ECM plays an essential role in the regulation of corpus luteum formation. Our previous studies have demonstrated that TGF-β1 is a potent inhibitor of luteinization in human granulosa-lutein (hGL) cells. Whether TGF-β1 can regulate the expression of COL1A1 during the luteal phase remains to be elucidated. The aim of this study was to investigate the effect of TGF-β1 on the regulation of COL1A1 expression and the underlying molecular mechanisms using an immortalized hGL cell line (SVOG cells) and primary hGL cells (obtained from 20 consenting patients undergoing IVF treatment). The results showed that TGF-β1 significantly upregulated the expression of COL1A1. Using inhibition approaches, including pharmacological inhibition (a specific p38 inhibitor, SB203580, and a specific ERK1/2 inhibitor, U0126) and specific siRNA-mediated knockdown inhibition, we demonstrated that TGF-β1 promoted the expression and production of COL1A1 in hGL cells, most likely via the ALK5-mediated p38 signaling pathway. Our findings provide insights into the molecular mechanisms by which TGF-β1 promotes the deposition of type I collagen during the late follicular phase in humans.

Transcriptomics of cumulus cells - a window into oocyte maturation in humans

BACKGROUND

Cumulus cells (CC) encapsulate growing oocytes and support their growth and development. Transcriptomic signatures of CC have the potential to serve as valuable non-invasive biomarkers for oocyte competency and potential. The present sibling cumulus-oocyte-complex (COC) cohort study aimed at defining functional variations between oocytes of different maturity exposed to the same stimulation conditions, by assessing the transcriptomic signatures of their corresponding CC. CC were collected from 18 patients with both germinal vesicle and metaphase II oocytes from the same cycle to keep the biological variability between samples to a minimum. RNA sequencing, differential expression, pathway analysis, and leading-edge were performed to highlight functional differences between CC encapsulating oocytes of different maturity.

RESULTS

Transcriptomic signatures representing CC encapsulating oocytes of different maturity clustered separately on principal component analysis with 1818 genes differentially expressed. CCs encapsulating mature oocytes were more transcriptionally synchronized when compared with CCs encapsulating immature oocytes. Moreover, the transcriptional activity was lower, albeit not absent, in CC encapsulating mature oocytes, with 2407 fewer transcripts detected than in CC encapsulating immature (germinal vesicle - GV) oocytes. Hallmark pathways and ovarian processes that were affected by oocyte maturity included cell cycle regulation, steroid metabolism, apoptosis, extracellular matrix remodeling, and inflammation.

CONCLUSIONS

Herein we review our findings and discuss how they align with previous literature addressing transcriptomic signatures of oocyte maturation. Our findings support the available literature and enhance it with several genes and pathways, which have not been previously implicated in promoting human oocyte maturation. This study lays the ground for future functional studies that can enhance our understanding of human oocyte maturation.

Developmental Programming: Sheep Granulosa and Theca Cell-Specific Transcriptional Regulation by Prenatal Testosterone

Prenatal testosterone (T)-treated sheep, similar to polycystic ovarian syndrome women, manifest reduced cyclicity, functional hyperandrogenism, and polycystic ovary (PCO) morphology. The PCO morphology results from increased follicular recruitment and persistence of antral follicles, a consequence of reduced follicular growth and atresia, and is driven by cell-specific gene expression changes that are poorly understood. Therefore, using RNA sequencing, cell-specific transcriptional changes were assessed in laser capture microdissection isolated antral follicular granulosa and theca cells from age 21 months control and prenatal T-treated (100 mg intramuscular twice weekly from gestational day 30 to 90; term: 147 days) sheep. In controls, 3494 genes were differentially expressed between cell types with cell signaling, proliferation, extracellular matrix, immune, and tissue development genes enriched in theca; and mitochondrial, chromosomal, RNA, fatty acid, and cell cycle process genes enriched in granulosa cells. Prenatal T treatment 1) increased gene expression of transforming growth factor β receptor 1 and exosome component 9, and decreased BCL6 corepressor like 1, BCL9 like, and MAPK interacting serine/threonine kinase 2 in both cells, 2) induced differential expression of 92 genes that included increased mitochondrial, ribosome biogenesis, ribonucleoprotein, and ubiquitin, and decreased cell development and extracellular matrix-related pathways in granulosa cells, and 3) induced differential expression of 56 genes that included increased noncoding RNA processing, ribosome biogenesis, and mitochondrial matrix, and decreased transcription factor pathways in theca cells. These data indicate that follicular function is affected by genes involved in transforming growth factor signaling, extracellular matrix, mitochondria, epigenetics, and apoptosis both in a common as well as a cell-specific manner and suggest possible mechanistic pathways for prenatal T treatment-induced PCO morphology in sheep.

Ovarian Follicular Theca Cell Recruitment, Differentiation, and Impact on Fertility: 2017 Update

The major goal of this review is to summarize recent exciting findings that have been published within the past 10 years that, to our knowledge, have not been presented in detail in previous reviews and that may impact altered follicular development in polycystic ovarian syndrome (PCOS) and premature ovarian failure in women. Specifically, we will cover the following: (1) mouse models that have led to discovery of the derivation of two precursor populations of theca cells in the embryonic gonad; (2) the key roles of the oocyte-derived factor growth differentiation factor 9 on the hedgehog (HH) signaling pathway and theca cell functions; and (3) the impact of the HH pathway on both the specification of theca endocrine cells and theca fibroblast and smooth muscle cells in developing follicles. We will also discuss the following: (1) other signaling pathways that impact the differentiation of theca cells, not only luteinizing hormone but also insulinlike 3, bone morphogenic proteins, the circadian clock genes, androgens, and estrogens; and (2) theca-associated vascular, immune, and fibroblast cells, as well as the cytokines and matrix factors that play key roles in follicle growth. Lastly, we will integrate what is known about theca cells from mouse models, human-derived theca cell lines from patients who have PCOS and patients who do not have PCOS, and microarray analyses of human and bovine theca to understand what pathways and factors contribute to follicle growth as well as to the abnormal function of theca.

Gq/11-Dependent Changes in the Murine Ovarian Transcriptome at the End of Gestation

Parturition in rodents is highly dependent on the engagement of the luteal prostaglandin F2 alpha receptor, which, through activation of the G_q/11 family of G proteins, increases the expression of Akr1c18, leading to an increase in progesterone catabolism. To further understand the involvement of G_q/11 on luteolysis and parturition, we used microarray analysis to compare the ovarian transcriptome of mice with a granulosa/luteal cell-specific deletion of Galpha_q/11 with their control littermates on Day 18 of pregnancy, when mice from both genotypes are pregnant, and on Day 22, when mice with a granulosa/luteal cell-specific deletion of Galpha_q/11 are still pregnant but their control littermates are 1–2 days postpartum. Ovarian genes up-regulated at the end of gestation in a Galpha_q/11 -dependent fashion include genes involved in focal adhesion and extracellular matrix interactions. Genes down-regulated at the end of gestation in a Galpha_q/11-dependent manner include Serpina6 (which encodes corticosteroid-binding globulin); Enpp2 (which encodes autotaxin, the enzyme responsible for the synthesis of lysophosphatidic acid); genes involved in protein processing and export; reproductive genes, such as Lhcgr; the three genes needed to convert progesterone to estradiol (Cyp17a1, Hsd17b7, and Cyp19a1); and Inha. Activation of ovarian G_q/11 by engagement of the prostaglandin F2 alpha receptor on Day 18 of pregnancy recapitulated the regulation of many but not all of these genes. Thus, although the ovarian transcriptome at the end of gestation is highly dependent on the activation of G_q/11, not all of these changes are dependent on the actions of prostaglandin F2 alpha.

Identifying a novel role for X-prolyl aminopeptidase (Xpnpep) 2 in CrVI-induced adverse effects on germ cell nest breakdown and follicle development in rats

Environmental exposure to endocrine-disrupting chemicals (EDCs) is one cause of premature ovarian failure (POF). Hexavalent chromium (CrVI) is a heavy metal EDC widely used in more than 50 industries, including chrome plating, welding, wood processing, and tanneries. Recent data from U.S. Environmental Protection Agency indicate increased levels of Cr in drinking water from several American cities, which potentially predispose residents to various health problems. Recently, we demonstrated that gestational exposure to CrVI caused POF in F1 offspring. The current study was performed to identify the molecular mechanism behind CrVI-induced POF. Pregnant rats were treated with 25 ppm of potassium dichromate from Gestational Day (GD) 9.5 to GD 14.5 through drinking water, and the fetuses were exposed to CrVI through transplacental transfer. Ovaries were removed from the fetuses or pups on Embryonic Day (ED) 15.5, ED 17.5, Postnatal Day (PND) 1, PND 4, or PND 25, and various analyses were performed. Results showed that gestational exposure to CrVI: 1) increased germ cell/oocyte apoptosis and advanced germ cell nest (GCN) breakdown; 2) increased X-prolyl aminopeptidase (Xpnpep) 2, a POF marker in humans, during GCN breakdown; 3) decreased Xpnpep2 during postnatal follicle development; and 4) increased colocalization of Xpnpep2 with Col3 and Col4. We also found that Xpnpep2 inversely regulated the expression of Col1, Col3, and Col4 in all the developmental stages studied. Thus, CrVI advanced GCN breakdown and increased follicle atresia in F1 female progeny by targeting Xpnpep2.