Localization of angiotensin II in pig ovary and its effects on oocyte maturation in vitro

Transplantation of human umbilical cord-derived mesenchymal stem cells improves age-related ovarian functional decline via regulating the local renin-angiotensin system on inflammation and oxidative stress

BACKGROUND

Age-related reproductive aging is a natural and irreversible physiological process, and delaying childbearing is increasingly common all over the world. Transplantation of mesenchymal stem cells (MSCs) is considered a new and effective therapy to restore ovarian function, but the relevant mechanisms remain unclear. Recently, it has been found that there is a local Renin-angiotensin system (RAS) in human ovary and it plays a key role.

METHODS

After collecting follicular fluid from women who received oocyte retrieval for pure male factor infertility, the level of RAS components in it were detected, and the correlation analysis by linear regression. Then, the in vivo experiments on female C57BL/6 mice were designed to measure ovarian function, and the transcription and translation levels of RAS pathway were detected by molecular biology methods. Moreover, the role of RAS in regulating inflammation and oxidative stress in the co-culture system were explored in in vitro experiments on KGN cells.

RESULTS

First, a total of 139 samples of analyzable follicular fluid were obtained. The local RAS of ovary, which is independent of systemic RAS (P > 0.05), is affected by age (Pearson r < 0, P < 0.05) and related to ovarian function, inflammation, oxidative stress indexes and assisted reproduction laboratory outcomes (P < 0.05). Next, the ovary/body weight of aging mice decreased significantly and serum sex hormones levels changed significantly (P < 0.01). The number of functional follicles decreased, while the atresia follicles increased (P < 0.05). After MSCs transplantation, all the above measures have been partially recovered (P < 0.05). Although several RAS components in aging ovary changed, MSCs only improved the expression level of AT1R (P < 0.05). Furthermore, the secretion ability and mitochondrial membrane potential of aging KGN cells decreased, while the intracellular ROS level and the aging cells ratio increased (P < 0.01). All the above measures have been partially recovered when co-cultured with MSCs (P < 0.05). After Ang(1-7) were added into the co-culture system, the above have been more significantly restored compared with Ang II (P < 0.05). Nevertheless, there was no statistical difference in estradiol level no matter which one was added (P > 0.05).

CONCLUSIONS

Together, our findings indicate that a novel possible mechanism to explain how stem cells restore age-related ovarian functional decline.

Ovarian follicle transcriptome dynamics reveals enrichment of immune system process during transition from small to large follicles in cyclic Indian Ghoongroo pigs

Ovarian follicular development is a critical determinant of reproductive performance in litter bearing species like pigs, wherein economic gains depend on litter size. The study aimed to gain insight into the differentially expressed genes (DEGs) and signalling pathways regulating follicular growth and maturation in Ghoongroo pigs. Transcriptome profiling of porcine small follicles (SF) and large follicles (LF) was conducted using NovaSeq600 sequencing platform and DEGs were identified using DESeq2 with threshold of Padj. < 0.05 and log2 fold change cut off 0.58 (LF vs. SF). Functional annotations and bioinformatics analysis of DEGs were performed to find out biological functions, signalling pathways and hub genes regulating follicular dynamics. Transcriptome analysis revealed 709 and 479 genes unique to SF and LF stages, respectively, and 11,993 co-expressed genes in both the groups. In total, 507 DEGs (284 upregulated and 223 downregulated) were identified, which encoded for diverse proteins including transcription factors (TFs). These DEGs were functionally linked to response to stimulus, lipid metabolic process, developmental process, extracellular matrix organisation along with the immune system process, indicating wide-ranging mechanisms associated with follicular transition. The enriched KEGG pathways in LF stage consisted of ovarian steroidogenesis, cholesterol and retinol metabolism, cell adhesion molecules, cytokine receptor interaction and immune signalling pathways, depicting intra-follicular control of varied ovarian function. The hub gene analysis revealed APOE, SCARB1, MMP9, CYP17A1, TYROBP as key regulators of follicular development. This study identified candidate genes and TFs providing steroidogenic advantage to LFs which makes them fit for selection into the ovulatory pool of follicles.

Local renin-angiotensin system molecular mechanisms in intrauterine adhesions formation following gynecological operations, new strategy for novel treatment

It has recently been proposed that local tissue renin-angiotensin system activation has a role in post-surgical adhesion. Intrauterine adhesions are scar tissues that form in the endometrial cavity causing the walls of the uterine to adhere together. Women, undergoing major gynecological surgery, are exposed to a high risk of adhesion formation. Post-operative uterine adhesion is associated with chronic pain and infertility that are important problems following post-operation uterine adhesion. A local renin-angiotensin system has been found in the organs of the female reproductive system, for example in the endometrium. Data about the physiological roles of local RAS in the gynecological tract are largely unknown, but dysfunctional local RAS in the endometrium may contribute to this pathological condition. Local AngII/AT1R may be over-activated after surgical injury or hypoxia leading to an up-regulation of the molecular mechanisms that may lead to a chronic immune response, oxidative stress, and increase the expression of fibrotic molecules like TGF-β to induce the risk of connective fibrotic tissues. Based on AngII/AT1R pathological potential to induce pelvic and uterine adhesions, using angiotensin receptor blockers could be a therapeutic strategy for the prevention and treatment of post-surgical adhesions.IMPACT STATEMENTWhat is already known on this subject? Intrauterine adhesions are described as fibrotic scar tissues following gynecological surgeries. It's reported that 55-100% of women are at risk of intrauterine adhesion after gynecological surgeries. Injury to tissues and hypoxia during the surgery, promote molecular mechanisms to contribute post-surgical adhesion. Recently evidence supports the existence of renin-angiotensin system components in the gynecological tract. Abnormal expression of local angiotensin II and AT1R in uterus tissue following gynecological surgeries up-regulate molecular mechanisms to induce post-operative adhesions.What do the results of this study add? Recently there has been an increased focus on the role of the local renin-angiotensin system in organ fibrosis. The results of this Mini-review article refer to the pathological roles of the local renin-angiotensin system in fibrotic bands formation after gynecological operations. Over-activation of local renin-angiotensin systems up-regulate molecular mechanisms such as inflammation and the TGF-β1 signalling pathway. TGF-β as a profibrotic molecule strongly induces the expression of some fibrotic molecules such as PAI and TIMP to increase the risk of intrauterine adhesions.What are the implications of these findings for clinical practice and/or further research? According to the biological roles of local renin-angiotensin system and AT1R following injuries to develop post-operative adhesion, the administration of ARBs may be considered as a new therapeutic strategy for the prevention of IUA.

Physiological and pathological roles of Ang II and Ang- (1-7) in the female reproductive system

The local Renin-Angiotensin System (RAS) has been demonstrated to exist in a wide range of tissues and organs, In the female reproductive system, it is mainly found in the ovary, uterus and placenta. The RAS system is made up of a series of active substances and enzymes, in addition to the circulating endocrine renin-angiotensin system. The active peptides Angiotensin II (Ang II) and Angiotensin (1-7) (Ang-(1-7)), in particular, appear to have distinct activities in the local RAS system, which also controls blood pressure and electrolytes. Therefore, in addition to these features, angiotensin and its receptors in the reproductive system seemingly get involved in reproductive processes, such as follicle growth and development, as well as physiological functions of the placenta and uterus. In addition, changes in local RAS components may induce reproductive diseases as well as pathological states such as cancer. In most tissues, Ang II and Ang- (1-7) seem to maintain antagonistic effects, but this conclusion is not always true in the reproductive system, where they play similar functions in some physiological and pathological roles. This review investigated how Ang II, Ang- (1-7) and their receptors were expressed, localized, and active in the female reproductive system. This review also summarized their effects on follicle development, uterine and placental physiological functions. The changes of local RAS components in a series of reproductive system diseases including infertility related diseases and cancer and their influence on the occurrence and development of diseases were elucidated. This article reviews the physiological and pathological roles of Ang II and Ang- (1-7) in female reproductive system,a very intricate system of tissue factors that operate as agonists and antagonists was found. Besides, the development of novel therapeutic strategies targeting components of this system may be a research direction in future.

Prostaglandin E2 involvement in mammalian female fertility: ovulation, fertilization, embryo development and early implantation

BACKGROUND

Infertility in mammalian females has been a challenge in reproductive medicine. The causes of female infertility include anovulation, ovulated oocyte defects, abnormal fertilization, and insufficient luteal support for embryo development, as well as early implantation. Ovulation induction, in vitro fertilization and luteal support regimens have been performed for decades to increase fertility rates. The identification of proteins and biochemical factors involved in female reproduction is essential to further increase female fertility rates. Evidence has shown that prostaglandins (PGs) might be involved in the female reproductive process, mainly ovulation, fertilization, and implantation. However, only a few studies on individual PGs in female reproduction have been done so far. This review aimed to identify the pivotal role of prostaglandin E2 (PGE2), a predominant PG, in female reproduction to improve fertility, specifically ovulation, fertilization, embryo development and early implantation.

RESULTS

Prostaglandin E2 (PGE2) was shown to play a relevant role in the ovulatory cascade, including meiotic maturation, cumulus expansion and follicle rupture, through inducing ovulatory genes, such as Areg, Ereg, Has2 and Tnfaip6, as well as increasing intracellular cAMP levels. PGE2 reduces extracellular matrix viscosity and thereby optimizes the conditions for sperm penetration. PGE2 reduces the phagocytic activity of polymorphonuclear neutrophils (PMNs) against sperm. In the presence of PGE2, sperm function and binding capacity to oocytes are enhanced. PGE2 maintains luteal function for embryo development and early implantation. In addition, it induces chemokine expression for trophoblast apposition and adhesion to the decidua for implantation.

CONCLUSION

It has been shown that PGE2 positively affects different stages of female fertility. Therefore, PGE2 should be taken into consideration when optimizing reproduction in infertile females. We suggest that in clinical practice, the administration of non-steroidal anti-inflammatory drugs, which are PGE2 synthesis inhibitors, should be reasonable and limited in infertile women. Additionally, assessments of PGE2 protein and receptor expression levels should be taken into consideration.

Expression of angiotensin II receptors in the caprine ovary and improvement of follicular viability in vitro

This study aimed to evaluate mRNA levels of angiotensin II (ANG II) receptors (AGTR1 and AGTR2) in caprine follicles and to investigate the influence of ANG II on the viability and in vitro growth of preantral follicles. Real-time polymerase chain reaction (PCR) was used to quantify AGTR1 and AGTR2 mRNA levels in the different follicular stages. For culture, caprine ovaries were collected, cut into 13 fragments and then either directly fixed for histological and ultrastructural analysis (fresh control) or placed in culture for 1 or 7 days in α-minumum essential medium plus (α-MEM+) with 0, 1, 5, 10, 50 or 100 ng/ml ANG II. Then, the fragments were destined to morphological, viability and ultrastructural analysis. The results showed that primordial follicles had higher levels of AGTR1 and AGTR2 mRNA than secondary follicles. Granulosa/theca cells from antral follicles had higher levels of AGTR1 mRNA than their respective cumulus-oocyte complex (COCs). After 7 days of culture, ANG II (10 or 50 ng/ml) maintained the percentages of normal follicles compared with α-MEM+. Fluorescence and ultrastructural microscopy confirmed follicular integrity in ANG II (10 ng/ml). In conclusion, a high expression of AGTR1 and AGTR2 is observed in primordial follicles. Granulosa/theca cells from antral follicles had higher levels of AGTR1 mRNA. Finally, 10 ng/ml ANG II maintained the viability of caprine preantral follicles after in vitro culture.

Angiotensin-converting enzymes play a dominant role in fertility

According to the World Health Organization, infertility, associated with metabolic syndrome, has become a global issue with a 10%-20% incidence worldwide. An accumulating body of evidence has shown that the renin-angiotensin system is involved in the fertility problems observed in some populations. Moreover, alterations in the expression of angiotensin-converting enzyme-1, angiotensin-converting enzyme-2, and angiotensin-converting enzyme-3 might be one of the most important mechanisms underlying both female and male infertility. However, as a pseudogene in humans, further studies are needed to explore whether the abnormal angiotensin-converting enzyme-3 gene could result in the problems of human reproduction. In this review, the relationship between angiotensin-converting enzymes and fertile ability is summarized, and a new procedure for the treatment of infertility is discussed.

Local Renin-Angiotensin system in the reproductive system

The renin-angiotensin system (RAS) is well known as regulator of electrolytes and blood pressure. Besides this function, there are numerous studies supporting the idea of a local tissue RAS. This system controls the local activity of the different RAS family members, especially of the functional proteins Angiotensin II and Angiotensin (1-7). Those antagonistically acting proteins have been described to be expressed in different organ systems including the human reproductive tract. Therefore, this local RAS has been suspected to be involved in the control and regulation of physiological and pathological conditions in the female reproduction tract. This review of the available literature summarizes the physiological influence of the RAS on the follicular development, ovarian angiogenesis, and placental- and uterine function. In addition, in the second part the role of the RAS concerning ovarian- and endometrial cancer becomes elucidated. This section includes possible novel therapeutic strategies via inhibition of RAS-mediated tumor growth and angiogenesis. Looking at a very complex system of agonistic and antagonistic tissue factors, it may be supposed that the RAS in the female reproduction tract will be of rising scientific interest in the upcoming years.

Is there a role of the local tissue RAS in the regulation of physiologic and pathophysiologic conditions in the reproductive tract?

The renin-angiotensin system is well known as a systemic endocrine pathway that regulates blood pressure and salt-water metabolism. In addition to the systemic renin-angiotensin system there is evidence in different species for the presence of a local tissue renin-angiotensin system, which allows local production of the bioactive peptides angiotensin II and angiotensin (1-7). The local renin-angiotensin system has been found in a variety of tissues including tissue of the human reproductive tract. Thus, it was suspected that it may have important functions in the local hormonal microenvironment. Here, a systematic literature search was undertaken to review whether there is evidence for regulatory functions of the local tissue renin-angiotensin system in the human reproductive tract under physiological and pathological conditions.

Effect of angiotensin II with follicle cells and insulin-like growth factor-I or insulin on bovine oocyte maturation and embryo development

The objective was to evaluate the effects of angiotensin II (Ang II), insulin-like growth factor-I (IGF-I) and insulin on the nuclear and cytoplasmic maturation of bovine oocytes in the presence of follicular cells. Cumulus-oocyte complexes (COCs) were cultured for 22h in the presence of follicular cells (control with cells) and Ang II, IGF-I or insulin (treatments), or in the absence of follicular cells (control without cells). Using these five groups, Experiment 1 was conducted with and without the addition of gonadotrophins. Only oocytes in the Ang II group resumed meiosis at rates (88.2+/-1.8% and 90.7+/-4.3% for oocytes cultured in the absence or presence of LH/FSH, respectively) similar to those observed for oocytes cultured in the absence of follicular cells (89.7+/-0.3% and 92.6+/-2.6%; P<0.01). In Experiment 2, the effect of Ang II alone and in combination with IGF-I or insulin on oocyte maturation for 7h (germinal vesicle breakdown), 12h (metaphase I) and 22h (metaphase II) was evaluated in a design similar to that of the first experiment. Ang II plus IGF-I or insulin induced the resumption of meiosis, irrespective of the presence of gonadotrophins (P<0.01). Experiment 3 used groups similar Experiment 2 to determine the rate of subsequent embryo development, using fetal calf serum (FCS) in the culture medium. The COCs were cultured in maturation medium for 1h (1+23h), 12h (12+12h) or 24h in the presence of follicular cells and the respective treatments and for the remaining period in the absence of follicular cells to complete 24h. In Experiment 4, BSA was used in lieu of serum in the maturation medium in a 12+12h maturation system. Oocytes matured using the 12+12h system with BSA or FCS in the presence of Ang II+IGF-I had higher rates of blastocyst formation than the other treatments (P<0.05). In conclusion, Ang II reversed the inhibitory effect of follicular cells on nuclear maturation of bovine oocytes, irrespective of the presence of gonadotrophins, IGF-I and insulin. However, oocyte cytoplasmatic maturation (i.e., subsequent embryo development), was higher when Ang II and IGF-I were present in the maturation medium containing follicular cells cultured for 12+12h.

Localisation of renin-angiotensin system (RAS) components in breast

Angiotensin II has mitogenic and angiogenic effects and its receptors are widespread, particularly in epithelial tissue. Tissue renin angiotensin systems (tRASs) may be a local source of angiotensin II that has specific paracrine functions. To investigate the presence of a tRAS in normal human breast and tumours. Immunocytochemistry, and quantitative RT–PCR was used to establish: (i) the presence and localisation of RAS components, (ii) the possibility of their involvement in cancer. (1) mRNA coding for angiotensinogen, prorenin, angiotensin converting enzyme (ACE), and both AT1 and AT2 receptors was demonstrated in normal and diseased breast tissues. (2) (pro)renin was identified in epithelial cells in both normal and diseased tissue, but in invasive carcinoma, its distribution was mostly confined to fibroblasts or could not be detected at all. (3) Angiotensin converting enzyme was shown in epithelial cells in both normal and malignant tissue. The results are consistent with the hypothesis that a tRAS is present in the breast, and is disrupted in invasive cancer.