The presence of VEGF and Notch2 during preantral-antral follicular transition in infantile rats: Anatomical evidence and its implications

The vascular endothelial growth factor (VEGF) system as a key regulator of ovarian follicle angiogenesis and growth

The vascular endothelial growth factor-A (VEGFA) system is a complex set of proteins, with multiple isoforms and receptors, including both angiogenic (VEGFxxx, VEGFR2) and antiangiogenic members (VEGFxxxb, VEGFR1 and soluble forms of VEGFR). The members of the VEGF system affect the proliferation, survival, and migration of endothelial and nonendothelial cells and are involved in the regulation of follicular angiogenesis and development. The production of VEGF by secondary follicles stimulates preantral follicular development by directly affecting follicular cells and promoting the acquisition of the follicular vasculature and downstream antrum formation. Additionally, the pattern of expression of the components of the VEGF system may provide a proangiogenic milieu capable of triggering angiogenesis and stimulating follicular cells to promote antral follicle growth, whereas, during atresia, this milieu becomes antiangiogenic and blocks follicular development.

NORHA, a novel follicular atresia-related lncRNA, promotes porcine granulosa cell apoptosis via the miR-183-96-182 cluster and FoxO1 axis

BACKGROUND

Follicular atresia has been shown to be strongly associated with a low follicle utilization rate and female infertility, which are regulated by many factors such as microRNAs (miRNAs), which constitute a class of noncoding RNAs (ncRNAs). However, little is known about long noncoding RNAs (lncRNAs), which constitute another ncRNA family that regulate follicular atresia.

RESULTS

A total of 77 differentially expressed lncRNAs, including 67 upregulated and 10 downregulated lncRNAs, were identified in early atretic follicles compared to healthy follicles by RNA-Sequencing. We characterized a noncoding RNA that was highly expressed in atretic follicles (NORHA). As an intergenic lncRNA, NORHA was one of the upregulated lncRNAs identified in the atretic follicles. To determine NORHA function, RT-PCR, flow cytometry and western blotting were performed, and the results showed that NORHA was involved in follicular atresia by influencing GC apoptosis with or without oxidative stress. To determine the mechanism of action, bioinformatics analysis, luciferase reporter assay and RNA immunoprecipitation assay were performed, and the results showed that NORHA acted as a 'sponge', that directly bound to the miR-183-96-182 cluster, and thus prevented its targeted inhibition of FoxO1, a major sensor and effector of oxidative stress.

CONCLUSIONS

We provide a comprehensive perspective of lncRNA regulation of follicular atresia, and demonstrate that NORHA, a novel lncRNA related to follicular atresia, induces GC apoptosis by influencing the activities of the miR-183-96-182 cluster and FoxO1 axis.

Association of Variants in Vascular Endothelial Growth Factor A Gene and VEGFA Serum Levels with the Risk of Primary Ovarian Insufficiency: A Case-Control Study

OBJECTIVE

The study aimed at investigating the association between the vascular endothelial growth factor A (VEGFA) genetic variants, the VEGFA serum level, and the primary ovarian insufficiency (POI) risk in Chinese Han women.

DESIGN

An age-matched case-control study was implemented in the West China Second Hospital of Sichuan University. Participants/Materials, Setting, Methods: Blood samples and clinical information were collected from 240 patients with POI and 261 healthy controls between December 2012 and December 2018 at the West China Second Hospital of Sichuan University. Mutations of VEGFA gene -2578C/A, -1154G/A, 936C/T, and -634C/G were identified by PCR-RFLP. Moreover, VEGFA serum levels in the 2 groups were measured by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

The -1154G>A and 936C>T variants of the VEGFA gene were significantly associated with POI (the adjusted odds ratio [OR] = 2.17 and 95% confidence interval [CI] = 1.07-4.43 for the former; the adjusted OR = 2.74 and 95% CI = 1.18-6.34 for the latter), whereas no significant difference was found in the genotype distribution of -2578C>A and -634C>G variants between patients and controls (p > 0.05). Moreover, the combined -1154G>A and 936C>T genotype was associated with a significantly increased risk of POI (the adjusted OR = 21.98, 95% CI = 2.78-173.78 among subjects carrying 3 or more variants), particularly when patients aged ≥35 years (the adjusted OR = 20.58, and 95% CI = 2.58-164.25). The POI group exhibited an obviously lower VEGFA serum level (45.15 ± 1.25 pg/mL) than the control group. Compared with the control, the expression of VEGFA was significantly decreased in the POI group (279.90 ± 5.71 pg/mL; p < 0.05). Moreover, the serum VEGFA levels are lower in the -1154AA genotype than those of AG/GG genotypes.

LIMITATIONS

The main limitation is that all participants enrolled in this study were Chinese. As genotype and allelotype frequencies tend to differ between ethnic populations, extrapolation of the results to other ethnic groups should be cautiously considered.

CONCLUSIONS

Our study indicates an association between the VEGFA -1154G/A, 936C/T variants, and susceptibility to POI in Chinese Han women. Reduced levels of VEGFA may be a potential mechanism for the de-velopment of POI.

Morphology and morphometry of preantral follicles, and immunolocalization of angiogenic factors in ovarian tissue from the neotropical primateSapajus apella

Ovarian biopsies from five health adult monkeys were collected by exploratory laparotomy. Preantral follicles (primordial, primary, and secondary) were classified as normal or degenerated and submitted to morphometric analysis in which granulosa cell counts and the areas of follicles, oocytes, and oocyte nuclei were measured. Ovarian fragments were also immunolabelled for the quantitative analysis of VEGFA and CD31 protein expression in the ovarian tissue and in the preantral follicles. In total, 213 preantral follicles was examined for morphometry and morphological classification. From this total, 20 (9.4%) were follicles enclosing two or more oocytes, i.e. multi-oocyte follicles (MOFs). From the 193 follicles enclosing only one oocyte, 46.3% were classified as primordial, 24,1% as transition, 23.3% as primary, and 6.3% as secondary follicles. The mean number of granulosa cells surrounding primordial, transition, primary, and secondary follicles was 9.2, 12.1, 18.7, and 45.3, respectively. Increase in oocyte diameter was observed from primary to secondary follicles, while the oocyte nucleus increased only when follicles reached the secondary stage. The expression of CD31 was strong in vessels, corpus luteum, and in normal oocytes and granulosa cells from preantral follicles at all developmental stages. Likewise, VEGFA expression was observed in vessels and preantral follicles (granulosa cells, the oocyte and the oocyte nucleus). We characterized the morphology, and morphometry and expression of angiogenic factors in normal and atretic preantral follicles fromSapajus apella. This description can support the analysis of follicular quality and survival after procedures such as transplantation and cryopreservation.

Transcriptomic Analysis for Differentially Expressed Genes in Ovarian Follicle Activation in the Zebrafish

In teleosts, the onset of puberty in females is marked by the appearance of the first wave of pre-vitellogenic (PV) follicles from the pool of primary growth (PG) follicles (follicle activation) in the ovary during sexual maturation. To understand the mechanisms underlying follicle activation and therefore puberty onset, we undertook this transcriptomic study to investigate gene expression profiles in the event. Our analysis revealed a total of 2,027 up-regulated and 859 down-regulated genes during the PG-PV transition. Gene Ontology (GO) analysis showed that in addition to basic cellular functions such as gene transcription, cell differentiation, and cell migration, other biological processes such as steroidogenesis, cell signaling and angiogenesis were also enriched in up-regulated genes; by comparison, some processes were down-regulated including piRNA metabolism, gene silencing and proteolysis. Further Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified a variety of signaling pathways that might play pivotal roles in PG-PV transition, including MAPK, TGF-β, Hedgehog, FoxO, VEGF, Jak-STAT, and phosphatidylinositol signaling pathways. Other pathways of particular interest included endocytosis and glycosaminoglycan biosynthesis. We also analyzed expression changes of genes expressed in different compartments viz. oocytes and follicle cells. Interestingly, most oocyte-specific genes remained unchanged in expression during follicle activation whereas a great number of genes specifically expressed in the follicle cells showed significant changes in expression. Overall, this study reported a comprehensive analysis for genes, biological processes and pathways involved in follicle activation, which also marks female puberty onset in the zebrafish when occurring for the first time in sexual maturation.