Follicular atresia and luteolysis. Evidence of a role for N-cadherin

Effects of indented zona pellucida on oocyte growth and development explored from changes of gene expression in cumulus cells

PURPOSE

Abnormal Zona Pellucida (ZP) of human oocytes is an extracellular oocyte abnormality leading to subfertility or infertility, among which indented ZP (iZP) is a common clinical case, and there is currently no effective clinical solution. The study aimed to find out the influence of this abnormal ZP on the growth and development of GC and further explore its influence on the growth and development of oocytes, hoping to provide new ideas for the etiology and treatment of such patients.

METHODS

In this study, we collected granulosa cells GC from oocytes with iZP(four cases) and GC from oocytes with a normal appearance of the ZP(eight cases) during ICSI treatment cycles, and submitted them to transcriptomic analysis using next-generation RNA sequencing (RNAseq).

RESULTS

177 Differentially Expressed Genes (DEG) were identified by RNAseq analysis of Granulosa Cells (GC) from oocytes with a normal ZP morphological appearance and those with iZP. Correlation analysis of these DEGs showed that the expression levels of the immune factor CD274 and the inflammatory factors IL4R and IL-7R, which are positively associated with ovulation, were significantly down-regulated in the GC of oocytes with iZP. Hippo, PI3K-AKT, Ras and calcium signaling pathways related to oocyte growth and development, NTRK2 and its ligands (BDNF and NT5E) from the neurotrophin family that are trophic to the oocyte were also significantly down-regulated in the GC of oocytes with iZP. In addition, the expression of cadherin family members CDH6, CDH12 and CDH19 were significantly down-regulated in DEGs, and the down-regulation of these proteins may affect the gap junction between Granulosa cells and oocytes.

CONCLUSION

IZP might cause obstacles to dialogue and material exchange between GC and oocytes and further affect the growth and development of oocytes.

Microcystin-LR accelerates follicular atresia in mice via JNK-mediated adherent junction damage of ovarian granulosa cells

Microcystin-LR (MC-LR), one of aquatic environmental contaminants with reproductive toxicity produced by cyanobacterial blooms, but its toxic effects and mechanisms on the ovary are not fully understood. Here, proteomic techniques and molecular biology experiments were performed to study the potential mechanism of MC-LR-caused ovarian toxicity. Results showed that protein expression profile of ovarian granulosa cells (KK-1) was changed by 17 μg/mL MC-LR exposure. Comparing with the control group, 118 upregulated proteins as well as 97 downregulated proteins were identified in MC-LR group. Function of differentially expressed proteins was found to be enriched in pathways related to adherent junction, such as cadherin binding, cell-cell junction, cell adhesion and focal adherens. Furthermore, in vitro experiments, MC-LR significantly downregulated the expression levels of proteins associated with adherent junction (β-catenin, N-cadherin, and α-catenin) as well as caused cytoskeletal disruption in KK-1 cells (P < 0.05), indicating that the adherent junction was damaged. Results of in vivo experiments have shown that after 14 days of acute MC-LR exposure (40 μg/kg), damaged adherent junction and an increased number of atretic follicles were observed in mouse ovaries. Moreover, MC-LR activated JNK, an upstream regulator of adherent junction proteins, in KK-1 cells and mouse ovarian tissues. In contrast, JNK inhibition alleviated MC-LR-induced adherent junction damage in vivo and in vitro, as well as the number of atretic follicles. Taken together, findings from the present study indicated that JNK is involved in MC-LR-induced granulosa cell adherent junction damage, which accelerated follicular atresia. Our study clarified a novel mechanism of MC-LR-caused ovarian toxicity, providing a theoretical foundation for protecting female reproductive health from environmental pollutants.

Chitosan Oligosaccharides Alleviate H2O2-stimulated Granulosa Cell Damage via HIF-1α Signaling Pathway

Oocyte maturation disorder and decreased quality are the main causes of infertility in women, and granulosa cells (GCs) provide the only microenvironment for oocyte maturation through autocrine and paracrine signaling by steroid hormones and growth factors. However, chronic inflammation and oxidative stress caused by ovarian hypoxia are the largest contributors to ovarian aging and GC dysfunction. Therefore, the amelioration of chronic inflammation and oxidative stress is expected to be a pivotal method to improve GC function and oocyte quality. In this study, we detected the protective effect of chitosan oligosaccharides (COS), on hydrogen peroxide- (H₂O₂-) stimulated oxidative damage in a human ovarian granulosa cell line (KGN). COS significantly increased cell viability, mitochondrial function, and the cellular glutathione (GSH) content and reduced apoptosis, reactive oxygen species (ROS) content, and the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE), hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial-derived growth factor (VEGF) in H₂O₂-stimulated KGN cells. COS treatment significantly increased levels of the TGF-β1 and IL-10 proteins and decreased levels of the IL-6 protein. Compared with H₂O₂-stimulated KGN cells, COS significantly increased the levels of E₂ and P₄ and decreased SA-β-gal protein expression. Furthermore, COS caused significant inactivation of the HIF-1α-VEGF pathway in H₂O₂-stimulated KGN cells. Moreover, inhibition of this pathway enhanced the inhibitory effects of COS on H₂O₂-stimulated oxidative injury and apoptosis in GCs. Thus, COS protected GCs from H₂O₂-stimulated oxidative damage and apoptosis by inactivating the HIF-1α-VEGF signaling pathway. In the future, COS might represent a therapeutic approach for ameliorating disrupted follicle development.

Isolation, identification and differentiation of human spermatogonial cells on three-dimensional decellularized sheep testis

Improvement of in vitro culture methods of Spermatogonial Stem Cells (SSCs) is known to be an effective procedure for further study of the process of spermatogenesis and can offer effective therapeutic modality for male infertility. Tissue decellularization by providing natural 3D and extracellular matrix (ECM) conditions for cell growth can be an alternative procedure to enhance in vitro culture conditions. In the present study, the testicular tissues were taken from brain death donors. After enzymatic digestion, the tissue cells were isolated and cultured for four weeks. Then the identity of the SSCs was confirmed using anti-GFRα1 and anti-PLZF antibodies via immunocytochemistry (ICC). The differentiation capacity of SSCs were evaluated by culture of them on a layer of decellularized testicular matrix (DTM) prepared from sheep testis, as well as under two-dimensional (2D) culture with differentiation medium. After four and six weeks of the initiation of differentiation culture, the pre-meiotic, meiotic and post- meiotic genes at the mRNA and protein levels was examined via qPCR and ICC methods, respectively. The results showed that pre-meiotic, meiotic and post-meiotic genes expressions were significantly higher in the cells cultured in DTM substrate (P ≤ 0.01).The present study indicated that, the natural structure of ECM prepare the suitable conditions for further study of the spermatogenesis process in the in vitro and contributes to the maintenance and treatment of male infertility.

In Vitro Spermatogenesis by Three-dimensional Culture of Spermatogonial Stem Cells on Decellularized Testicular Matrix

Background

In the males, Spermatogonial Stem Cells (SSCs) contribute to the production of sex cells and fertility. In vitro SSCs culture can operate as an effective strategy for studies on spermatogenesis and male infertility treatment. Cell culture in a three-dimensional (3D) substrate, relative to a two-dimensional substrate (2D), creates better conditions for cell interaction and is closer to in vivo conditions. In the present study, in order to create a 3D matrix substrate, decellularized testicular matrix (DTM) was used to engender optimal conditions for SSCs culture and differentiation.

Materials and Methods

After, testicular cells enzymatic extraction from testes of brain-dead donors, the SSCs were proliferated in a specific culture medium for four weeks, and after confirming the identity of the colonies derived from the growth of these cells, they were cultured on a layer of DTM as well as in 2D condition with a differentiated culture medium. In the Sixth week since the initiation of the differentiation culture, the expression of pre meiotic (OCT4 & PLZF ), meiotic (SCP3 & BOULE) and post meiotic (CREM & Protamine-2) genes were measured in both groups.

Results

The results indicated that the expression of pre meiotic, meiotic and post meiotic genes was significantly higher in the cells cultured on DTM (P ≤ 0.001).

Conclusion

SSCs culture in DTM with the creation of ECM and similar conditions with in vivo can be regarded as a way of demonstrating spermatogenesis in vitro, which can be adopted as a treatment modality for male infertility.

KLF4 overexpression decreases the viability, invasion and migration of papillary thyroid cancer cells

Kruppel-like factor 4 (KLF4) has been implicated in a number of different types of cancer; however, the role of KLF4 in papillary thyroid cancer remains elusive. The present study aimed to investigate the role of KLF4 in papillary thyroid cancer and its potential underlying molecular mechanisms. The expression of KLF4 in thyroid tumor tissue and adjacent non-cancerous tissues were detected via immunohistochemistry and western blotting. The papillary thyroid cancer cell line, KTC1, was transfected with viruses carrying KLF4 overexpression vectors. The relative expression of KLF4, E-cadherin, N-cadherin, Vimentin, matrix metalloproteinase (MMP)2, MMP9 and collagen was detected via quantitative-PCR. The viability of KTC1 cells was detected using a cell counting kit-8 assay at 24, 48 and 72 h. Cell invasion was examined via a transwell invasion assay. Cell migration was examined via a scratch migration assay at 0 and 24 h. Compared with adjacent non-cancerous tissues, the expression of KLF4 was significantly lower in thyroid tumor tissues. The expression of KLF4 in KTC1 cells were significantly increased compared with the blank or negative control groups. The expression of N-cadherin, MMP2, MMP9 and collagen was significantly decreased in the KLF4 overexpression group. The viability of KTC1 cells was markedly decreased in KLF4 overexpression group at 24, 48 and 72 h when compared with the blank or negative control groups. The invasion of KTC1 cells in the KLF4 overexpression group was markedly decreased. Compared with the negative control group, the KTC1 cell migration in the KLF4 overexpression group was markedly decreased at 24 h. The expression of KLF4 was also significantly lower in thyroid tumor tissues. The cell viability, tumor invasion and migration ability and expression levels of N-cadherin, MMP2, MMP9 and collagen in papillary thyroid cancer cells were markedly decreased with KLF4 overexpression.

Role of JNK during buccopharyngeal membrane perforation, the last step of embryonic mouth formation

BACKGROUND

The buccopharyngeal membrane is a thin layer of cells covering the embryonic mouth. The perforation of this structure creates an opening connecting the external and the digestive tube which is essential for oral cavity formation. In humans, persistence of the buccopharyngeal membrane can lead to orofacial defects such as choanal atresia, oral synechiaes, and cleft palate. Little is known about the causes of a persistent buccopharyngeal membrane and, importantly, how this structure ruptures.

RESULTS

We have determined, using antisense and pharmacological approaches, that Xenopus embryos deficient c-Jun N-terminal kinase (JNK) signaling have a persistent buccopharyngeal membrane. JNK deficient embryos have decreased cell division and increased cellular stress and apoptosis. However, altering these processes independently of JNK did not affect buccopharyngeal membrane perforation. JNK deficient embryos also have increased intercellular adhesion and defects in e-cadherin localization. Conversely, embryos with overactive JNK have epidermal fragility, increased E-cadherin internalization, and increased membrane localized clathrin. In the buccopharyngeal membrane, clathrin is colocalized with active JNK. Furthermore, inhibition of endocytosis results in a persistent buccopharyngeal membrane, mimicking the JNK deficient phenotype.

CONCLUSIONS

The results of this study suggest that JNK has a role in the disassembly adherens junctions by means of endocytosis that is required during buccopharyngeal membrane perforation. Developmental Dynamics 246:100-115, 2017. © 2016 Wiley Periodicals, Inc.

Hormone-dependent bacterial growth, persistence and biofilm formation--a pilot study investigating human follicular fluid collected during IVF cycles

Human follicular fluid, considered sterile, is aspirated as part of an in vitro fertilization (IVF) cycle. However, it is easily contaminated by the trans-vaginal collection route and little information exists in its potential to support the growth of microorganisms. The objectives of this study were to determine whether human follicular fluid can support bacterial growth over time, whether the steroid hormones estradiol and progesterone (present at high levels within follicular fluid) contribute to the in vitro growth of bacterial species, and whether species isolated from follicular fluid form biofilms. We found that bacteria in follicular fluid could persist for at least 28 weeks in vitro and that the steroid hormones stimulated the growth of some bacterial species, specifically Lactobacillus spp., Bifidobacterium spp. Streptococcus spp. and E. coli. Several species, Lactobacillus spp., Propionibacterium spp., and Streptococcus spp., formed biofilms when incubated in native follicular fluids in vitro (18/24, 75%). We conclude that bacteria aspirated along with follicular fluid during IVF cycles demonstrate a persistent pattern of growth. This discovery is important since it can offer a new avenue for investigation in infertile couples.

miR-26b promotes granulosa cell apoptosis by targeting ATM during follicular atresia in porcine ovary

More than 99% of ovarian follicles undergo atresia in mammals, but the mechanism of follicular atresia remains to be elucidated. In this study, we explored microRNA (miRNA) regulation of follicular atresia in porcine ovary. A miRNA expression profile was constructed for healthy, early atretic, and progressively atretic follicles, and the differentially expressed miRNAs were selected and analyzed. We found that miR-26b, which was upregulated during follicular atresia, increased the number of DNA breaks and promoted granulosa cell apoptosis by targeting the ataxia telangiectasia mutated gene directly in vitro.

Expression of mRNA for cell adhesion molecules in the bovine corpus luteum during the estrous cycle and PGF2alpha-induced luteolysis

Cell-to-cell interaction via cell contact-dependent pathway is essentially important for maintenance and regulation of corpus luteum (CL) integrity and its physiological actions. The objective of the present study was to evaluate the mRNA expression of the cell adhesion molecules (CAMs) that are constituent factors of gap junctions [connexin (Cx) 43] and adherence junctions (VE-, E-, N-cadherin) in two types of endothelial cells from the mid CL and in CL tissue during the estrous cycle and PGF(2alpha)-induced luteolysis in the cow. Specific mRNA expression for Cx43 and N-cadherin was detected in cytokeratin-positive (CK+) and cytokeratin-negative (CK-) luteal endothelial cells (EC) and fully luteinized granulosa cells (LGC). E-cadherin mRNA was expressed in CK+EC and LGC, but not in CK-EC. VE-cadherin mRNA was expressed in both CK+ and CK-EC. During the estrous cycle, Cx43 mRNA expression was significantly lower in the regressing CL. VE-cadherin expression also tended to increase in the mid CL and increased significantly in the regressing CL. E-cadherin mRNA expression was higher in the early and late CL than in the mid- and regressing CL. N-cadherin mRNA expression gradually increased from the early to late CL followed by a decrease in the regressing CL. During PGF(2alpha)-induced luteolysis, Cx43 mRNA expression appeared to increase, and VE-cadherin and E-cadherin mRNA significantly increased at 24 h. N-cadherin mRNA expression decreased 2 and 4 h after PGF(2alpha) administration. Collectively, expression of the mRNAs for CAMs was different in the two types of luteal endothelial cells and fully luteinized granulosa cells and changed independently in the CL during the estrous cycle and PGF(2alpha)-induced luteolysis in the cow. The results suggest that CAMs play physiological roles in cell-to-cell communication to regulate both gap and adherence junctions during CL development and regression in the cow.

Luteogenic hormones act through a vascular endothelial growth factor-dependent mechanism to up-regulate alpha 5 beta 1 and alpha v beta 3 integrins, promoting the migration and survival of human luteinized granulosa cells

The formation of the corpus luteum (CL) is critical for the establishment of a successful pregnancy. After ovulation, the CL develops from the remnants of the ovulated ovarian follicle. This process, which involves varying cell-matrix interactions, is poorly characterized. To understand the role and potential regulation of cell-matrix interactions in the formation of the CL, we investigated the expression and activity of the matrix protein fibronectin (FN) and several of its integrin receptors on luteinized granulosa cells (GCs). In situ, FN and several FN-binding integrins were detected around luteinizing GCs during the early luteal phase, although expression declined in the late luteal phase. In vitro, GCs released FN, and stimulation of these cells with human chorionic gonadotropin increased the surface expression of FN, alpha(5)beta(1), and alpha(v)beta(3). Up-regulation of these proteins on GCs was reproduced by stimulation with vascular endothelial growth factor (VEGF) and was inhibited by anti-VEGF antibody. Lastly, expression of alpha(5)beta(1) and alpha(v)beta(3) mediated adhesion to FN, facilitated migration, and prevented apoptosis. These data suggest that in vivo luteogenic hormones, in part through a VEGF-dependent mechanism, stimulate selected integrin-matrix adhesive interactions that promote the motility and survival of GCs and thus contribute to the formation and preservation of the CL.

Progesterone regulation of human granulosa/luteal cell viability by an RU486-independent mechanism

CONTEXT

Progesterone (P4) inhibits human granulosa/luteal cell apoptosis by an unknown mechanism.

OBJECTIVE

Our objective was to assess the role of the nuclear P4 receptor (PGR) and PGR membrane component 1 (PGRMC1) in mediating P4's antiapoptotic action in human granulosa/luteal cells.

DESIGN, SETTING, AND PATIENTS

In vitro laboratory studies were designed in which human granulosa/luteal cells were harvested from in vitro fertilization patients from 2004-2006.

MAIN OUTCOME MEASURE

Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assays and DNA staining. Protein expression was observed by Western blot and immunocytochemistry.

RESULTS

PGR was detected in 20% of the human granulosa/luteal cells, and 25 and 50 microM RU486 induced at least 70% of the cells to undergo apoptosis. Five micromolar RU486 neither induced apoptosis nor attenuated the antiapoptotic action of 1 microM P4. PGRMC1 and its binding partner, plasminogen activator inhibitor RNA-binding protein-1 (PAIRBP1), were detected in human granulosa/luteal cells. Antibodies to either PGRMC1 or PAIRBP1 completely attenuated P4's action.

CONCLUSIONS

PGR does not exclusively mediate P4's action because 1) 5 microM RU486 should have been able to override the antiapoptotic action of 1 microM P4 because RU486 binds to the PGR at a greater affinity than P4; 2) 25 and 50 microM RU486 induce three to four times more cells to undergo apoptosis than express PGR; 3) P4 must be continuously present to prevent apoptosis, which implies a rapid, possibly membrane-initiated mechanism of action; and 4) expression and blocking antibody studies suggest that PGRMC1 and PAIRBP1 account in part for P4's action in human granulosa/luteal cells.

Novel trends in follicular development, atresia and corpus luteum regression: a role for apoptosis

During ovarian follicular development in humans, only a limited number of follicles mature and ovulate. The vast majority of follicles stop developing after the formation of an antrum and then undergo atresia. The few that are selected to become ovulatory follicles are transformed into corpora lutea following ovulation. The lifespan of the corpus luteum is also limited. In each oestrus/menstrual cycle, corpora lutea regress and are eliminated by a progress called luteolysis. During atresia and luteolysis, granulosa and lutein cells undergo apoptosis. It is believed that there are many signal transduction pathways that control apoptosis in order to suppress full maturation of too many follicles and to protect the dominant follicle from the apoptotic process prior the ovulation. Such interplay between different factors, some of them produced in the ovary, may modulate apoptosis of corpus luteum cells, in order to preserve the function of the corpus luteum during pregnancy or to eliminate the old corpora lutea of the previous cycle. The present review reports a number of factors that regulate follicular atresia and corpus luteum regression, via apoptotic pathways. Elucidation of apoptotic mechanisms may lead to prevention of female infertility or other pathological conditions.

Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Expression of osteopontin (OPN) mRNA in bovine ovarian follicles and corpora lutea

The matricellular protein osteopontin (OPN) plays a role in various physiological processes, including angiogenesis and tissue remodelling. As these processes are essential for the maintenance of ovarian physiology, the aim of the study was to investigate the expression of OPN (mRNA) in ovarian cells and to evaluate whether it can be regulated by gonadotrophins. Using conventional RT-PCR and real-time PCR, we have detected and quantified OPN mRNA as well as glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA expression in bovine granulosa, theca and luteal cells. In all cells examined, both genes were found in equal amounts and no striking variations in the expression could be observed between granulosa, theca and luteal cells. Furthermore, no effect on either OPN or GAPDH mRNA expression was evident after culturing ovarian cells in the presence of gonadotrophic hormones, although the cells were still highly responsive in terms of cAMP formation. Although neither variations between different cell types nor a regulation of OPN mRNA expression by gonadotrophic hormones could be detected, the high and unambiguous mRNA expression in steroidogenic cells suggests that OPN should be added to the growing list of intraovarian factors which may be involved in ovarian physiology.