MiRNA-143 mediates the proliferative signaling pathway of FSH and regulates estradiol production

MicroRNA miR-125b can suppress ovarian granulosa cell functions: Interrelationships with FSH

This study aimed to evaluate the involvement of miR-125b and its interrelationship with follicle-stimulating hormone (FSH) in the control of basic ovarian granulosa cell functions. The effect of miR-125b mimics on basic functions of porcine ovarian granulosa cells cultured with and without FSH, and the effect of FSH on the expression of endogenous miR-125b was examined. Expression levels of miR-125b, viability, proliferation (accumulation of PCNA and cyclin B1), apoptosis (accumulation of bax and caspase 3), the accumulation of FSH receptors (FSHR), steroid hormones, insulin-like growth factor I (IGF-I), oxytocin, and prostaglandin E2 release were analysed by reverse transcription-quantitative polymerase chain reaction, Trypan blue exclusion test, quantitative immunocytochemistry, and ELISA. Transfection of cells with miR-125b mimics inhibited cell viability, proliferation, apoptosis, the occurrence of FSHR, progesterone, testosterone, estradiol, and oxytocin release but stimulated prostaglandin E2 output. FSH promoted cell viability, proliferation, steroid hormones, IGF-I, oxytocin, and prostaglandin E2 output and reduced the expression of miR-125b and apoptosis. Furthermore, miR-125b mimics supported the effect of FSH on the release of estradiol, IGF-I, and prostaglandin E2, and inverted FSH influence on cell viability, proliferation, apoptosis, progesterone, and testosterone output. FSH supported both inhibitory and stimulatory action of miR-125b on ovarian cell functions. Present observations indicate that: miR-125b can be involved in the control of basic ovarian functions and that miR-125b and FSH are antagonists in their actions on ovarian cell functions. The ability of FSH to reduce miR-125b expression and the ability of miR-125b mimics to decrease the occurrence of FSHR and to modify FSH effects indicate the existence of the self-inhibiting FSH-miR-125b axis and that miR-125b can mediate the actions of FSH on ovarian cells.

E2/ER signaling mediates the meiotic arrest of goat intrafollicular oocytes induced by follicle-stimulating hormone

The increased production of high-quality oocytes lies at the heart of the search to accelerate the reproduction of high-quality breeding livestock using assisted reproductive technology. Follicle-stimulating hormone (FSH) maintains the arrest of oocyte meiosis during early follicular development in vivo and promotes the synchronous maturation of nucleus and cytoplasm to improve oocyte quality. However, the mechanism by which FSH maintains meiotic arrest in oocytes is still not fully understood. Oocytes spontaneously resume meiosis once released from the arrested state. In this study, we isolated goat antral follicles with a diameter of 2.0-4.0 mm, cultured them in vitro either with or without added FSH, and finally collected the oocytes to observe their meiotic state. The results showed that FSH effectively inhibited the meiotic recovery of oocytes in follicles [4 h: control (n = 84) vs. with FSH (n = 86), P = .0115; 6 h: control (n = 86) vs. FSH (n = 85), P = 0.0308; and 8 h: control (n = 95) vs. FSH (n = 101), P = 0.0039]. FSH significantly inhibited the downregulation of natriuretic peptide receptor 2 (NPR2) expression and cyclic guanosine monophosphate (cGMP) synthesis during follicular culture in vitro (P < 0.05). Further exploration found that FSH promoted the synthesis of 17β-estradiol (E2) (P = .0249 at 4 h and P = .0039 at 8 h) and maintained the expression of the estrogen nuclear receptor ERβ, but not the estrogen nuclear receptor ERα during follicle culture in vitro (P = .0190 at 2 h, and P = .0100 at 4 h). In addition, E2/ER (estrogen nuclear receptors ERα and ERβ) mediated the inhibitory effect of FSH on the downregulation of NPR2 expression and cGMP synthesis, ultimately preventing the meiotic recovery of oocytes (P < .05). In summary, our study showed that FSH-induced estrogen production in goat follicles, and the E2/ER signaling pathway, both mediated meiotic arrest in FSH-induced goat oocytes.

Identification of differentially expressed microRNAs in ovulatory and subordinate follicles in Dazu black goats

How multiple ovulations happen in prolific goats is still unknown even though studies on ovarian physiology and folliculogenesis have made extensive progress. MicroRNAs (miRNAs) are a class of endogenous regulatory factors and regulate structural gene expression mainly at the post-transcriptional level. In this study, in the follicular phase, six large follicles were collected from prolific Dazu black goat and used to generate RNA libraries for RNA sequencing. Based on the litter size and average number of ovulatory follicles in Dazu black goats, the largest three follicles were sorted as ovulatory follicles, and the remaining as subordinate ones. In total, 418 known miRNAs and 110 novel miRNAs were found, and the expression of six randomly selected miRNAs was validated by quantitative PCR analysis. Nine miRNAs were differently expressed between the ovulatory and subordinate follicles (p < 0.01). Chi-miR-582-5p, novel-130, chi-miR-214-3p, and chi-miR-500-5p were upregulated in the ovulatory group, and chi-miR-383, chi-miR-130b-5p, chi-miR-92a-3p, chi-miR-125b-5p, and novel-9 were downregulated in the same group. Chi-miR-130b-5p and chi-miR-214-3p were predicted to target at LHR (XM_013967581.1), GDF9 (NM_001285708.1), BMP15 (NM_001285588.1), and CYP19A1 (XM_013967046.1). In conclusion, nine miRNAs were differently expressed between ovulatory and subordinate follicles, and chi-miR-130b-5p and chi-miR-214-3p were predicted to regulate the expression of genes involved in gonadotropin hormone signaling and oocyte-derived growth factors. Additional studies are needed to confirm these findings.

Why Is It So Difficult To Have Competent Oocytes from In vitro Cultured Preantral Follicles?

The developmental competence of oocytes is acquired gradually during follicular development, mainly through oocyte accumulation of RNA molecules and proteins that will be used during fertilization and early embryonic development. Several attempts to develop in vitro culture systems to support preantral follicle development up to maturation are reported in the literature, but oocyte competence has not yet been achieved in human and domestic animals. The difficulties to have fertilizable oocytes are related to thousands of mRNAs and proteins that need to be synthesized, long-term duration of follicular development, size of preovulatory follicles, composition of in vitro culture medium, and the need of multi-step culture systems. The development of a culture system that maintains bidirectional communication between the oocyte and granulosa cells and that meets the metabolic demands of each stage of follicle growth is the key to sustain an extended culture period. This review discusses the physiological and molecular mechanisms that determine acquisition of oocyte competence in vitro, like oocyte transcriptional activity, follicle and oocyte sizes, and length and regulation of follicular development in murine, human, and domestic animal species. The state of art of in vitro follicular development and the challenges to have complete follicular development in vitro are also highlighted.

MicroRNAs with non-additive expression in the ovary of hybrid hens target genes enriched in key reproductive pathways that may influence heterosis for egg laying traits

Heterosis has been extensively exploited in chicken breeding to improve laying traits in commercial hybrid stock. However, the molecular mechanisms underlying it remains elusive. This study characterizes the miRNAome in the pre-hierarchical follicles of purebred and hybrid laying hens, and investigate the functions of miRNAs with non-additive expression in the pre-hierarchical follicles as they modulate heterosis for egg number and clutch size. To achieve that aim, White Leghorn and Rhode Island Red chicken lines were reciprocally crossed to generate hybrids. The crossbreds demonstrated heterosis for egg number and clutch size, and pre-hierarchical follicles from 4 birds of each genotype were collected at 53 weeks of age. Mode of miRNA expression was characterized after miRNA sequencing. A total of 50 miRNAs including 30 novel ones, were found to exhibit non-additive expression. Dominance was the predominant mode of expression exhibited by majority of the miRNAs. Functional analysis of target genes of the known miRNAs with non-additive expression revealed Gene Ontology terms related to regulation of transcription, metabolic processes and gene expression. KEGG and REACTOME pathways including hedgehog, cellular senescence, wnt, TGF-β, progesterone-mediated oocyte maturation, oocyte meiosis, GnRH signaling, signal transduction and generic transcription, which can be linked to primordial follicle activation, growth and ovulation, were significantly enriched by target genes of miRNAs with non-additive expression. Majority of the genes enriched in these biological pathways were targeted by gga-miR-19a, gga-miR-19b, gga-miR-375, gga-miR-135a, and gga-miR-7 and 7b, thus, revealing their synergistic roles in enhancing processes that could influence heterosis for egg number and clutch size in hybrid hens.

Comprehensive analysis of differentially expressed profiles of mRNA, lncRNA, and miRNA of Yili geese ovary at different egg-laying stages

Background

The development of the ovaries is an important factor that affects egg production performance in geese. Ovarian development is regulated by genes that are expressed dynamically and stage-specifically. The transcriptome profile analysis on ovarian tissues of goose at different egg laying stages could provide an important basis for screening and identifying key genes regulating ovarian development.

Results

In this study, 4 ovary tissues at each breeding period of pre-laying (PP), laying (LP), and ceased-laying period (CP), respectively, with significant morphology difference, were used for RNA extraction and mRNAs, lncRNAs, and miRNAs comparison in Yili geese. CeRNA regulatory network was constructed for key genes screening. A total of 337, 1136, and 525 differentially expressed DE mRNAs, 466, 925, and 742 DE lncRNAs and 258, 1131 and 909 DE miRNAs were identified between PP and LP, between CP and LP, and between CP and PP groups, respectively. Functional enrichment analysis showed that the differentially expressed mRNAs and non-coding RNA target genes were mainly involved in the cell process, cytokine-cytokine receptor interaction, phagosome, calcium signaling pathway, steroid biosynthesis and ECM-receptor interaction. Differential genes and non-coding RNAs, PDGFRB, ERBB4, LHCGR, MSTRG.129094.34, MSTRG.3524.1 and gga-miR-145–5p, related to reproduction and ovarian development were highly enriched. Furthermore, lncRNA-miRNA-mRNA regulatory networks related to ovary development were constructed.

Conclusions

Our study found dramatic transcriptomic differences in ovaries of Yili geese at different egg-laying stages, and a differential lncRNA-miRNA-mRNA regulatory network related to cell proliferation, differentiation and apoptosis and involved in stromal follicle development were established and preliminarily validated, which could be regarded as a key regulatory pathway of ovarian development in Yili geese.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08774-4.

Regulation of vtg and VtgR in mud crab Scylla paramamosain by miR-34

BACKGROUND

Vitellogenin (Vtg) is the precursor of major yolk protein and plays a crucial role in the maturation of oocytes and the production of eggs in oviparous animals. Vitellogenin receptor (VtgR) mediates the transport of Vtg explicitly to oocytes in the membrane. In a previous study, we found that miR-34 can regulate the expression of some eyestalk genes and affect reproduction in mud crab Scylla paramamosain, one of the most important economic crabs on the coasts of southern China.

METHODS AND RESULTS

In this study, firstly, we found that miR-34 can target at 3'-UTR of Vtg and VtgR genes by using bioinformatic tools and predicted miR-34 might depress the expression of Vtg and VtgR. Secondly, the relative luciferase activity of HEK293T cells co-transfected with miRNA mimic and pmir-RB-REPORTTM-Vtg/VtgR-3'UTR was significantly lower than those of cells co-transfected with mimic NC and pmir-RB-REPORTTM-Vtg/VtgR-3'UTR. Finally, in vivo experiments showed that agomiR-34 could repress the expression of Vtg and VtgR genes, while Antigomir-34 could promote the expression of these two genes.

CONCLUSIONS

These results confirm our hypothesis and previous published results that miR-34 may indirectly regulate ovarian development by binding to the 3'-UTR of Vtg and VtgR genes and inhibiting their expression.

The emerging role of microRNAs in fish ovary: A mini review

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression primarily at the post-transcriptional levels. It is now well established that miRNAs are crucial regulators of many developmental and physiological processes, including reproduction. In teleosts, expression profiling studies have shown that miRNAs are expressed in the fish ovary and their levels are regulated during follicle development and by hormones. Using CRISPR/Cas9 mediated gene knockout strategies, several recent studies have provided strong evidence that miR-202 and miR-200s on chromosome 23 play critical roles in regulating ovarian development, oogenesis, and ovulation. In this mini review, we provide a brief overview of canonical miRNA biogenesis and functions; summarize miRNAs that are expressed in fish ovary; and discuss the emerging role of miRNAs in regulating fish ovarian functions.

miR-133b targets tagln2 and functions in tilapia oogenesis

microRNAs (miRNAs) are important components of non-coding RNAs that participate in diverse life activities by regulating gene expression at the post transcriptional level through base complementary pairing with 3'UTRs of target mRNAs. miR-133b is a member of the miR-133 family, which play important roles in muscle differentiation and tumorigenesis. Recently, miR-133b was reported to affect estrogen synthesis by targeting foxl2 in mouse, while its role in fish reproduction remains to be elucidated. In the present study, we isolated the complete sequence of miR-133b, which was highly expressed in tilapia ovary at 30 and 90 dah (days after hatching) and subsequently decreased at 120 to 150 dah by qPCR. Interestingly, only a few oogonia were remained in the antagomir-133b treated tilapia ovary, while phase I and II oocytes were observed in the ovaries of the control group. Unexpectedly, the expression of foxl2 and cyp19a1a, as well as estradiol levels in serum were increased in the treated group. Furthermore, tagln2, an important factor for oogenesis, was predicted as the target gene of miR-133b, which was confirmed by dual luciferase reporter vector experiments. miR-133b and tagln2 were co-expressed in tilapia ovaries. Taken together, miR-133b may be involved in the early oogenesis of tilapia by regulating tagln2 expression. This study enriches the understanding of miR-133b function during oogenesis and lays a foundation for further study of the regulatory network during oogenesis.

Human Granulosa Cells-Stemness Properties, Molecular Cross-Talk and Follicular Angiogenesis

The ovarian follicle is the basic functional unit of the ovary, comprising theca cells and granulosa cells (GCs). Two different types of GCs, mural GCs and cumulus cells (CCs), serve different functions during folliculogenesis. Mural GCs produce oestrogen during the follicular phase and progesterone after ovulation, while CCs surround the oocyte tightly and form the cumulus oophurus and corona radiata inner cell layer. CCs are also engaged in bi-directional metabolite exchange with the oocyte, as they form gap-junctions, which are crucial for both the oocyte’s proper maturation and GC proliferation. However, the function of both GCs and CCs is dependent on proper follicular angiogenesis. Aside from participating in complex molecular interplay with the oocyte, the ovarian follicular cells exhibit stem-like properties, characteristic of mesenchymal stem cells (MSCs). Both GCs and CCs remain under the influence of various miRNAs, and some of them may contribute to polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI) occurrence. Considering increasing female fertility problems worldwide, it is of interest to develop new strategies enhancing assisted reproductive techniques. Therefore, it is important to carefully consider GCs as ovarian stem cells in terms of the cellular features and molecular pathways involved in their development and interactions as well as outline their possible application in translational medicine.

MicroRNA-143 Sensitizes Cervical Cancer Cells to Cisplatin: a Promising Anticancer Combination Therapy

Cisplatin-based chemotherapy is commonly used for cervical cancer treatment. However, the development of chemoresistance is considered the main obstacle to the effectiveness of this therapeutic agent. MicroRNAs are illustrated to play a major role in the regulation of cancer cell chemosensitivity. Therefore, this study was aimed to investigate the potential therapeutic role of miRNA-143 in combination with cisplatin on cervical cancer cells. Then, CaSki cell line with low expression levels of miRNA-143 was selected for functional experiments. The cells were treated with miRNA-143 and cisplatin individually or in combination. The cell viability and apoptosis induction were evaluated by MTT, Annexin V-FITC/PI, and DAPI staining tests. Cell migration was further evaluated by wound healing assay. The effect of miRNA-143 and cisplatin combination on gene expression was quantified by real-time PCR. Furthermore, the combination therapy effect on cell cycle progression and autophagy induction was also evaluated by flow cytometry. Our results showed that miRNA-143 overexpression could increase cisplatin-induced apoptosis and increase the sensitivity of CaSki cells to low doses of this chemotherapeutic agent via modulating the expression of apoptosis-related genes including Bcl-2, Bax, and caspase-9. Besides, miRNA-143 and cisplatin were demonstrated to cooperatively increase the cell cycle arrest at the sub-G1 and G2-M phases, induce autophagy activation, and via downregulation of vimentin inhibit CaSki cell migration. Moreover, c-Myc as an important regulator of cell growth was downregulated in treatment groups compared to the control. In conclusion, regarding that miRNA-143 could sensitize cervical cancer cells to cisplatin, it may be considered a promising therapeutic strategy for the treatment of this malignancy.

The expression regulation of Cyclins and CDKs in ovary via miR-9c and miR-263a of Scylla paramamosain

Scylla paramamosain is an economically important cultured crab species in China. Cyclins and cyclin-dependent kinases (CDKs) play important roles in regulations of cell cycle and ovarian development. MiRNAs can negatively regulate gene expression at the post-transcriptional level through base-complementary pairing with the 3'-untranslated region (3-UTR) of the target gene. In this study, bioinformatics prediction showed that miR-9c and miR-263a identified from our group's gonad miRNAome of S. paramamosain may bind to the 3' UTR region of cyclin A, cyclin B, cyclin E, cyclin H, CDK1, and CDK2. Furthermore, the results of double luciferase reporter gene assay showed that the luciferase activities of HEK293T cells co-transfected with miR-9c mimics/miR-9c inhibitor and the 3'-UTR plasmid vectors of the five genes (cyclin A, cyclin B, cyclin H, CDK1, and CDK2) were significantly decreased/increased compared with those in the NC (negative control) and BC (blank control) groups. The results in miR-263a were similar to miR-9c, but all of the six genes could be regulated by miR-263a. In in vivo experiments, agomiR-9c (miR-9c enhancer) injection resulted in decreases of cyclin A and CDK1 expression level, and reverse effects were observed by injecting antagomiR-9c. AgomiR-263a decreased the expression of cyclin A, cyclin B, cyclin H, CDK1, and CDK2, but antagomiR-263a increased their expression. Both the in vitro and in vivo experiments confirmed functions of miR-9c and miR-263a in cell cycle progress of ovarian development by expression regulation of cyclin A, cyclin B, cyclin E, cyclin H, CDK1, and CDK2. The findings provide new insights into the reproductive regulation mechanism in mud crab and further enrich the knowledge of cell cycle and ovarian development regulation in invertebrates.

The Roles of the miRNAome and Transcriptome in the Ovine Ovary Reveal Poor Efficiency in Juvenile Superovulation

Simple Summary

Using the technology of juvenile superovulation, more follicles can be acquired in juvenile animals than in adult animals. However, oocytes derived from the follicles of juvenile animals are usually of poor quality, meaning that they have lower levels of subsequent maturation and embryonic development. In the present study, we used an exogenous hormone treatment to stimulate Hu sheep in order to compare the differences in ovarian superovulation effects and serum hormone secretion in juvenile and adult sheep. Differentially expressed microRNA (miRNA) and messenger RNA (mRNA) from the ovaries of juvenile and adult Hu sheep were then investigated using high-throughput sequencing technology to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment. We found that molecules of oar-miR-143 and follicle-stimulating hormone receptor (FSHR), among others, might regulate follicle formation, while oar-miR-485-3p, oar-miR-377-3p, and pentraxin 3 (PTX3), among others, may be associated with oocyte quality. The results will help us to identify miRNAs and mRNAs that could be used to predict ovarian superovulation potential and oocyte quality in the future.

Abstract

Juvenile superovulation can provide a wealth of oocyte material for embryo production, animal cloning, and genetic modification research, but embryos derived from juvenile oocytes show poor efficiency in subsequent developmental capacity. In order to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment, differentially expressed microRNAs (miRNAs) and messenger RNAs (mRNAs) were characterized and investigated in the ovaries of lambs and adult sheep using high-throughput sequencing technology. The majority of differentially expressed miRNAs (337/358) were upregulated in lamb libraries. The expression levels of mRNAs related to hormone receptors (follicle-stimulating hormone receptor, FSHR; luteinizing hormone/choriogonadotropin receptor, LHCGR; estrogen receptor 1, ESR1), steroid hormone secretion (cytochrome P450 family 11 subfamily A member 1, CYP11A1; cytochrome P450 family 17 subfamily A member 1, CYP17A1; cytochrome P450 family 19 subfamily A member 1, CYP19A1), and oocyte quality (pentraxin 3, PTX3; BCL2 apoptosis regulator, BCL2; caspase 3, CASP3) were significantly different between the lamb and adult libraries. The miRNA aor-miR-143, which targets FSHR, was highly and differentially expressed, and PTX3 was predicted to be targeted by oar-miR-485-3p and oar-miR-377-3p in the ovine ovary. A considerable number of miRNAs were predicted to inhibit ESR1 expression in lamb ovaries. In conclusion, oar-miR-143 and FSHR molecules, among others, might regulate follicle formation, and oar-miR-485-3p, oar-miR-377-3p, and PTX3, among others, may be associated with oocyte quality. These identified miRNAs and mRNAs will be beneficial for the prediction of ovarian superovulation potential and screening of oocytes.

Ovarian Aging: Role of Pituitary-Ovarian Axis Hormones and ncRNAs in Regulating Ovarian Mitochondrial Activity

The number of mitochondria in the oocyte along with their functions (e.g., energy production, scavenger activity) decline with age progression. Such multifaceted functions support several processes during oocyte maturation, ranging from energy supply to synthesis of the steroid hormones. Hence, it is hardly surprising that their impairment has been reported in both physiological and premature ovarian aging, wherein they are crucial players in the apoptotic processes that arise in aged ovaries. In any form, ovarian aging implies the progressive damage of the mitochondrial structure and activities as regards to ovarian germ and somatic cells. The imbalance in the circulating hormones and peptides (e.g., gonadotropins, estrogens, AMH, activins, and inhibins), active along the pituitary-ovarian axis, represents the biochemical sign of ovarian aging. Despite the progress accomplished in determining the key role of the mitochondria in preserving ovarian follicular number and health, their modulation by the hormonal signalling pathways involved in ovarian aging has been poorly and randomly explored. Yet characterizing this mechanism is pivotal to molecularly define the implication of mitochondrial dysfunction in physiological and premature ovarian aging, respectively. However, it is fairly difficult considering that the pathways associated with ovarian aging might affect mitochondria directly or by altering the activity, stability and localization of proteins controlling mitochondrial dynamics and functions, either unbalancing other cellular mediators, released by the mitochondria, such as non-coding RNAs (ncRNAs). We will focus on the mitochondrial ncRNAs (i.e., mitomiRs and mtlncRNAs), that retranslocate from the mitochondria to the nucleus, as active players in aging and describe their role in the nuclear-mitochondrial crosstalk and its modulation by the pituitary-ovarian hormone dependent pathways. In this review, we will illustrate mitochondria as targets of the signaling pathways dependent on hormones and peptides active along the pituitary/ovarian axis and as transducers, with a particular focus on the molecules retrieved in the mitochondria, mainly ncRNAs. Given their regulatory function in cellular activities we propose them as potential diagnostic markers and/or therapeutic targets.

The role of microRNAs in ovarian function and the transition toward novel therapeutic strategies in fertility preservation: from bench to future clinical application

BACKGROUND

New therapeutic approaches in oncology have converted cancer from a certain death sentence to a chronic disease. However, there are still challenges to be overcome regarding the off-target toxicity of many of these treatments. Oncological therapies can lead to future infertility in women. Given this negative impact on long-term quality of life, fertility preservation is highly recommended. While gamete and ovarian tissue cryopreservation are the usual methods offered, new pharmacological-based options aiming to reduce ovarian damage during oncological treatment are very attractive. In this vein, advances in the field of transcriptomics and epigenomics have brought small noncoding RNAs, called microRNAs (miRNAs), into the spotlight in oncology. MicroRNAs also play a key role in follicle development as regulators of follicular growth, atresia and steroidogenesis. They are also involved in DNA damage repair responses and they can themselves be modulated during chemotherapy. For these reasons, miRNAs may be an interesting target to develop new protective therapies during oncological treatment. This review summarizes the physiological role of miRNAs in reproduction. Considering recently developed strategies based on miRNA therapy in oncology, we highlight their potential interest as a target in fertility preservation and propose future strategies to make the transition from bench to clinic.

OBJECTIVE AND RATIONALE

How can miRNA therapeutic approaches be used to develop new adjuvant protective therapies to reduce the ovarian damage caused by cytotoxic oncological treatments?

SEARCH METHODS

A systematic search of English language literature using PubMed and Google Scholar databases was performed through to 2019 describing the role of miRNAs in the ovary and their use for diagnosis and targeted therapy in oncology. Personal data illustrate miRNA therapeutic strategies to target the gonads and reduce chemotherapy-induced follicular damage.

OUTCOMES

This review outlines the importance of miRNAs as gene regulators and emphasizes the fact that insights in oncology can inspire new adjuvant strategies in the field of onco-fertility. Recent improvements in nanotechnology offer the opportunity for drug development using next-generation miRNA-nanocarriers.

WIDER IMPLICATIONS

Although there are still some barriers regarding the immunogenicity and toxicity of these treatments and there is still room for improvement concerning the specific delivery of miRNAs into the ovaries, we believe that, in the future, miRNAs can be developed as powerful and non-invasive tools for fertility preservation.

MIR143 Inhibits Steroidogenesis and Induces Apoptosis Repressed by H3K27me3 in Granulosa Cells

The granulosa cell growth factor and apoptotic factor are two factors to determine follicular apoptosis. Whether ssc-miR-143-3p (MIR143) plays as an apoptosis factor in porcine granulosa cells (pGCs) remain unclear. This study tries to investigate what function of MIR143 is and how MIR143 gets these functions in pGCs from 3 to 5 mm medium-sized follicles. Firstly, 5' RACE was used to identify the structure of MIR143, and in situ hybridization, qPCR, and DNA pull-down were employed to exhibit the spatio-temporal expression and transcriptional regulation of MIR143. Furthermore, ELISA, Western blotting, and flow cytometry were adopted to explore the functions of MIR143 in pGCs. It was found that MIR143 was an exonic miRNA located in host gene LOC100514340 with an increasing expression during follicular growth. Moreover, MIR143 suppressed steroidogenesis related genes of HSD17β4, ER1, and PTGS2, negatively regulating estrogen, androgen, progesterone, and prostaglandin. MIR143 induced the apoptosis via activation of BAX-dependent Caspase 3 signaling. Furthermore, H3K27me3 influenced the recruitment of transcription factors and binding proteins to repress MIR143 transcription. At last, H3K27me3 agonist with MIR143 inhibition activated steroidogenesis but repressed apoptosis. These findings suggest that H3K27me3-mediated MIR143 inhibition play a critical role in follicular atresia by regulating cell apoptosis and steroidogenesis, which will provide useful information for further investigations of H3K27me3-miediated MIR143 epigenetic regulation in follicular growth in mammals.

Seasonal effects on miRNA and transcriptomic profile of oocytes and follicular cells in buffalo (Bubalus bubalis)

Season clearly influences oocyte competence in buffalo (Bubalus bubalis); however, changes in the oocyte molecular status in relation to season are poorly understood. This study characterizes the microRNA (miRNA) and transcriptomic profiles of oocytes (OOs) and corresponding follicular cells (FCs) from buffalo ovaries collected in the breeding (BS) and non-breeding (NBS) seasons. In the BS, cleavage and blastocyst rates are significantly higher compared to NBS. Thirteen miRNAs and two mRNAs showed differential expression (DE) in FCs between BS and NBS. DE-miRNAs target gene analysis uncovered pathways associated with transforming growth factor β (TGFβ) and circadian clock photoperiod. Oocytes cluster in function of season for their miRNA content, showing 13 DE-miRNAs between BS and NBS. Between the two seasons, 22 differentially expressed genes were also observed. Gene Ontology (GO) analysis of miRNA target genes and differentially expressed genes (DEGs) in OOs highlights pathways related to triglyceride and sterol biosynthesis and storage. Co-expression analysis of miRNAs and mRNAs revealed a positive correlation between miR-296-3p and genes related to metabolism and hormone regulation. In conclusion, season significantly affects female fertility in buffalo and impacts on oocyte transcriptomic of genes related to folliculogenesis and acquisition of oocyte competence.

Identification and Comparison of microRNAs in the Gonad of the Yellowfin Seabream (Acanthopagrus Latus)

Yellowfin seabream (Acanthopagrus latus) is a commercially important fish in Asian coastal waters. Although natural sex reversal has been described in yellowfin seabream, the mechanisms underlying sexual differentiation and gonadal development in this species remain unclear. MicroRNAs (miRNAs) have been shown to play crucial roles in gametogenesis and gonadal development. Here, two libraries of small RNAs, constructed from the testes and ovaries of yellowfin seabream, were sequenced. Across both gonads, we identified 324 conserved miRNAs and 92 novel miRNAs: 67 ovary-biased miRNAs, including the miR-200 families, the miR-29 families, miR-21, and miR-725; and 88 testis-biased miRNAs, including the let-7 families, the miR-10 families, miR-7, miR-9, and miR-202-3p. GO (Gene Ontology) annotations and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses of putative target genes indicated that many target genes were significantly enriched in the steroid biosynthesis pathway and in the reproductive process. Our integrated miRNA-mRNA analysis demonstrated a putative negatively correlated expression pattern in yellowfin seabream gonads. This study profiled the expression patterns of sex-biased miRNAs in yellowfin seabream gonads, and provided important molecular resources that will help to clarify the miRNA-mediated post-transcriptional regulation of sexual differentiation and gonadal development in this species.

The Role of MicroRNAs in Mammalian Fertility: From Gametogenesis to Embryo Implantation

The genetic codes inscribed during two key developmental processes, namely gametogenesis and embryogenesis, are believed to determine subsequent development and survival of adult life. Once the embryo is formed, its further development mainly depends on its intrinsic characteristics, maternal environment (the endometrial receptivity), and the embryo–maternal interactions established during each phase of development. These developmental processes are under strict genetic regulation that could be manifested temporally and spatially depending on the physiological and developmental status of the cell. MicroRNAs (miRNAs), one of the small non-coding classes of RNAs, approximately 19–22 nucleotides in length, are one of the candidates for post-transcriptional developmental regulators. These tiny non-coding RNAs are expressed in ovarian tissue, granulosa cells, testis, oocytes, follicular fluid, and embryos and are implicated in diverse biological processes such as cell-to-cell communication. Moreover, accumulated evidences have also highlighted that miRNAs can be released into the extracellular environment through different mechanisms facilitating intercellular communication. Therefore, understanding miRNAs mediated regulatory mechanisms during gametogenesis and embryogenesis provides further insights about the molecular mechanisms underlying oocyte/sperm formation, early embryo development, and implantation. Thus, this review highlights the role of miRNAs in mammalian gametogenesis and embryogenesis and summarizes recent findings about miRNA-mediated post-transcriptional regulatory mechanisms occurring during early mammalian development.

The role of miRNAs in regulating adrenal and gonadal steroidogenesis

miRNAs are endogenous noncoding single-stranded small RNAs of ~22 nucleotides in length that post-transcriptionally repress the expression of their various target genes. They contribute to the regulation of a variety of physiologic processes including embryonic development, differentiation and proliferation, apoptosis, metabolism, hemostasis and inflammation. In addition, aberrant miRNA expression is implicated in the pathogenesis of numerous diseases including cancer, hepatitis, cardiovascular diseases and metabolic diseases. Steroid hormones regulate virtually every aspect of metabolism, and acute and chronic steroid hormone biosynthesis is primarily regulated by tissue-specific trophic hormones involving transcriptional and translational events. In addition, it is becoming increasingly clear that steroidogenic pathways are also subject to post-transcriptional and post-translational regulations including processes such as phosphorylation/dephosphorylation, protein‒protein interactions and regulation by specific miRNAs, although the latter is in its infancy state. Here, we summarize the recent advances in miRNA-mediated regulation of steroidogenesis with emphasis on adrenal and gonadal steroidogenesis.

The Role of microRNAs in Ovarian Granulosa Cells in Health and Disease

The granulosa cell (GC) is a critical somatic component of the ovary. It is essential for follicle development by supporting the developing oocyte, proliferating and producing sex steroids and disparate growth factors. Knowledge of the GC's function in normal ovarian development and function, and reproductive disorders, such as polycystic ovary syndrome (PCOS) and premature ovarian failure (POF), is largely acquired through clinical studies and preclinical animal models. Recently, microRNAs have been recognized to play important regulatory roles in GC pathophysiology. Here, we examine the recent findings on the role of miRNAs in the GC, including four related signaling pathways (Transforming growth factor-β pathway, Follicle-stimulating hormones pathway, hormone-related miRNAs, Apoptosis-related pathways) and relevant diseases. Therefore, miRNAs appear to be important regulators of GC function in both physiological and pathological conditions. We suggest that targeting specific microRNAs is a potential therapeutic option for treating ovary-related diseases, such as PCOS, POF, and GCT.

Identification of Novel MicroRNAs and Characterization of MicroRNA Expression Profiles in Zebrafish Ovarian Follicular Cells

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression primarily at the post-transcriptional levels and thereby play important roles in regulating many physiological and developmental processes. Oocyte maturation in fish is induced by hormones produced from the hypothalamus, pituitary, and ovary. Gonadotropin-releasing hormone (GnRH) stimulates the secretion of luteinizing hormone (LH), which in turn, induces the secretion of maturation-inducing hormone (MIH) from the ovary. It is documented that small early vitellogenic (or stage IIIa) follicles are unable to undergo oocyte maturation whereas oocytes in mid- to late vitellogenic (stage IIIb) follicles can be induced by LH and MIH to become mature. To determine whether miRNAs may be involved in the growth and acquisition of maturational competency of ovarian follicles, we determined the miRNA expression profiles in follicular cells collected from stage IIIa and IIIb follicles using next-generation sequencing. It was found that miRNAs are abundantly expressed in the follicular cells from both stages IIIa and IIIb follicles. Furthermore, bioinformatics analysis revealed the presence of 214 known, 31 conserved novel and 44 novel miRNAs in zebrafish vitellogenic ovarian follicular cells. Most mature miRNAs in follicular cells were found to be in the length of 22 nucleotides. Differential expression analysis revealed that 11 miRNAs were significantly up-regulated, and 13 miRNAs were significantly down-regulated in the stage IIIb follicular cells as compared with stage IIIa follicular cells. The expression of four of the significantly regulated miRNAs, dre-miR-22a-3p, dre-miR-16a, dre-miR-181a-3p, and dre-miR-29a, was validated by real-time PCR. Finally, gene enrichment and pathway analyses of the predicted targets of the significantly regulated miRNAs supported the involvement of several key signaling pathways in regulating ovarian function, including oocyte maturation. Taken together, this study identifies novel zebrafish miRNAs and characterizes miRNA expression profiles in somatic cells within the zebrafish ovarian follicles. The differential expression of miRNAs between stage IIIa and IIIb follicular cells suggests that these miRNAs are important regulators of zebrafish ovarian follicle development and/or oocyte maturation.

miR-34 regulates reproduction by inhibiting the expression of MIH, CHH, EcR, and FAMeT genes in mud crab Scylla paramamosain

Mud crab Scylla paramamosain is a commercially important species widely cultured in China. It is well known that the eyestalk regulates reproductive activities in crustaceans. In our previous research, we found that the miR-34 expression level in male eyestalk was significantly higher than that in females. Thus, we assumed that it may play an important role in regulating reproduction. In this study, we used bioinformatic tools to identify the target genes of miR-34 in eyestalk. Six reproduction-related genes with an intact 3'-untranslated region (UTR), including molt-inhibiting hormone (MIH), crustacean hyperglycemic hormone (CHH), vitellogenesis-inhibiting hormone, red pigment concentrating hormone, ecdysone receptor (EcR), and farnesoic acid methyltransferase (FAMeT) were identified. When the 3'-UTR plasmid vectors of the six genes were cotransfected with miR-34 mimics into 293FT cells, respectively, the luciferase activities of four genes (MIH, CHH, EcR, and FAMeT) were significantly decreased compared with that in the control group; on the contrary, when the six plasmid vectors were cotransfected with the miR-34 inhibitor respectively, the luciferase activities of four genes (MIH, CHH, EcR, and FAMeT) were significantly higher than that in the control group. When agomiR-34 and antagomiR-34 were injected into the eyestalk respectively in vivo, the expression levels of the MIH, CHH, EcR, and FAMeT genes were detected by a quantitative real-time polymerase chain reaction. The results showed that agomiR-34 suppressed the expression of the four genes, whereas antagomiR-34 enhanced their expression. These experimental results confirmed our hypothesis that miR-34 may indirectly regulate reproduction via binding to the 3'-UTRs of MIH, CHH, EcR, and FAMeT genes and suppressing their expression.

MiR-31 and miR-143 affect steroid hormone synthesis and inhibit cell apoptosis in bovine granulosa cells through FSHR

The regulatory role of microRNAs (miRNAs) has been explored in ovarian cells, and the effects of miRNAs on gonadal development, apoptosis, ovulation, and steroid production have been reported. In this study, we analyzed the effects of follicle stimulating hormone (FSH) on miR-31 and miR-143 expression levels in bovine granulosa cells (GCs). Our results demonstrated that the FSH receptor (FSHR) is a common target gene of miR-31 and miR-143 in bovine GCs. We further analyzed the roles of miR-31 and miR-143 in bovine GCs by transfecting miR-31 and miR-143 mimics and inhibitors. The Western blot and RT-PCR results showed that miR-31 and miR-143 reduced the mRNA and protein expression levels of FSHR. Moreover, miR-31 overexpression decreased the secretion of progesterone (P4), and miR-143 overexpression decreased both the synthesis of P4 and the secretion of estrogen (E2). In contrast, miR-31 inhibition increased the secretion of progesterone (P4), and miR-143 inhibition increased both the synthesis of P4 and the secretion of E2. Finally, we analyzed the possible effects of miR-31 and miR-143 on bovine GC apoptosis. The results showed that transfection with miR-31 and miR-143 mimics promoted GC apoptosis and that miR-143 and miR-31 inhibition reduced the rate of apoptosis in bovine GCs. Taken together, our results indicate that miR-31 and miR-143 decrease steroid hormone synthesis and inhibit bovine GC apoptosis by targeting FSHR.

A gender specific improved survival related to stromal miR-143 and miR-145 expression in non-small cell lung cancer

Micro RNAs (miRNA) are small non-coding RNAs that post-transcriptionally regulate gene expression. Dysregulation of miRNA cluster 143/145 has been reported in several malignancies, but their role in non-small cell lung cancer (NSCLC) remains elusive. This study investigates the prognostic impact of miR-143 and miR-145 in primary tumors and metastatic lymph nodes in NSCLC tissue. Tissue from 553 primary tumors and 143 matched metastatic lymph nodes were collected and tissue microarrays were constructed. In situ hybridization was used to evaluate miR-143 and miR-145 expression in tumor epithelial cells and stromal cells in the primary tumors and lymph nodes. In vivo data was supplemented with functional studies of cell lines in vitro to evaluate the role of miR-143 and miR-145 in NSCLC tumorigenesis. In our cohort, stromal miR-143 (S-miR-143) and miR-145 (S-miR-145) expression in primary tumor tissue were independent prognosticators of improved disease-specific survival (DSS) in female (S-miR-143, HR: 0.53, p = 0.019) and male patients (S-miR-145, HR: 0.58, p = 0.021), respectively. Interesting correlations between the miR cluster 143/145 and previously investigated steroid hormone receptors from the same cohort were identified, substantiating their gender dependent significance.

MiR-181a inhibits vascular inflammation induced by ox-LDL via targeting TLR4 in human macrophages

Atherosclerosis is a kind of chronic inflammation disease with lipid accumulation in in blood vessel linings. Increasing evidence has reported that microRNAs can exert crucial roles in atherosclerosis. In previous study, miR-181a has been implicated to be abnormally expressed in atherosclerosis mice, however its detailed function in atherosclerosis remains uninvestigated. Hence, in our current study, we focused on the biological role of miR-181a in atherosclerosis progression. Ox-LDL has been commonly identified as an important atherosclerosis regulator. We observed that ox-LDL induced THP-1 cell apoptosis dose-dependently and time- dependently. Meanwhile, 25 µg/ml ox-LDL can promote foam cell formation and increased miR-181a expression significantly. CD36 has been involved in atherosclerosis progression and it was found that overexpression of miR-181a inhibited its protein levels. Moreover, miR-181a mimics repressed foam cell formation, TC and TG levels induced by ox-LDL dramatically. In addition, miR-181a mimics were able to reverse THP-1 cell apoptosis, increased IL-6, IL-1β, and TNF-α protein expression triggered by 25 µg/ml ox-LDL. TLR4 has been linked to various inflammation-associated diseases. In our present study, TLR4 was indicated as miR-181a target and the binding correlation between them was validated by dual-luciferase reporter assay. In conclusion, these results improves the understanding of atherosclerosis modulated by miR-181a/TLR4 and can contribute to development of new approaches for atherosclerosis.

Regulation of FSH expression by differentially expressed miR-186-5p in rat anterior adenohypophyseal cells

Follicle-stimulating hormone (FSH) has key roles in animal reproduction, including spermatogenesis and ovarian maturation. Many factors influence FSH secretion. However, despite the broad functions of microRNAs (miRNAs) via the regulation of target genes, little is known about their roles in FSH secretion. Our previous results suggested that miR-186-5p targets the 3′ UTR of FSHb; therefore, we examined whether miR-186-5p could regulate FSH secretion in rat anterior adenohypophyseal cells. miR-186-5p was transfected into rat anterior pituitary cells. The expression of FSHb and the secretion of FSH were examined by RT-qPCR and ELISA. A miR-186-5p mimic decreased the expression of FSHb compared with expression in the control group and decreased FSH secretion. In contrast, both the mRNA levels and secretion of FSH increased in response to miR-186-5p inhibitors. Our results demonstrate that miR-186-5p regulates FSH secretion by directly targeting the FSHb 3′ UTR, providing additional functional evidence for the importance of miRNAs in the regulation of animal reproduction.

miR-1275 controls granulosa cell apoptosis and estradiol synthesis by impairing LRH-1/CYP19A1 axis

miR-1275 is one of the microRNAs (miRNAs) that are differentially expressed during follicular atresia in pig ovaries, as identified by a miRNA microarray assay in our previous study [1]. However, its functions in follicular atresia remain unknown. In this study, we showed that miR-1275 promotes early apoptosis of porcine granulosa cells (pGCs) and the initiation of follicular atresia, and inhibits E2 release and expression of CYP19A1, the key gene in E2 production. Bioinformatics and luciferase reporter assays revealed that liver receptor homolog (LRH)-1, not CYP19A1, is a direct functional target of miR-1275. In vitro overexpression and knockdown experiments showed that LRH-1 significantly repressed apoptosis and induced E2 secretion and CYP19A1 expression in pGCs. LRH-1, whose expression was regulated by miR-1275, prevented apoptosis in pGCs. Furthermore, luciferase and chromatin immunoprecipitation assays demonstrated that LRH-1 protein bound to the CYP19A1 promoter and increased its activity. Our findings suggest that miR-1275 attenuates LRH-1 expression by directly binding to its 3'UTR. This prevents the interaction of LRH-1 protein with the CYP19A1 promoter, represses E2 synthesis, promotes pGC apoptosis, and initiates follicular atresia in porcine ovaries.

Identification and expression analysis of microRNAs in medaka gonads

Gonad development is a highly regulated, coordinated biological process and increasing evidences have indicated that microRNA (miRNA) may be involved in this dynamic program. Medaka (Oryzias latipes) is a good model for reproductive research as it has distinct sex determining genes, however, research in gonadal miRNAs is lacked. In this study, two small RNA libraries from the ovaries and testes were constructed and sequenced. A total of 285 conserved and 388 novel miRNAs were obtained, among which 142 mature miRNAs were significantly (> two-fold change) up or down regulated in the testis compared to the ovary. Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) analysis showed that miR-430c, miR-26a and miR-202-5p were expressed in a gonad-specific or sex-biased pattern. Fluorescence in situ hybridization (FISH) indicated that miR-202-5p was present throughout spermatogenesis and was only detected at the early stages of oogenesis, this sex biased expression pattern suggested that miR-202-5p might be a crucial candidate in male differentiation and development. Our study provides the repertoire, a comprehensive annotation of miRNAs from gonads and a reference for functional studies of miRNAs in medaka.

MicroRNAs: tiny molecules with a significant role in mammalian follicular and oocyte development

The genetic regulation of female fertility (follicular development, oocyte maturation and early preimplantation embryo development) involves the spatio-temporal regulation of those genes that play key roles in various stages of the female reproductive axis. MicroRNAs (miRNAs), a class of small non-coding RNAs, are known to regulate the expression of a large proportion of such genes. In recent decades, multiple studies have aimed to determine the roles of these non-coding RNAs in mammalian follicular development, oocyte growth and embryo development. These studies have applied a variety of approaches, including conditional knockout of miRNA biogenesis genes, high-throughput sequencing technologies for pattern recognition in miRNA expression and loss- and gain-of-function of miRNAs in various animal models. In addition to the cellular miRNAs, a large variety of RNAs are found in circulation, being coupled with extracellular vesicles, proteins and lipids. Because of their potential as diagnostic markers for abnormal physiologies, there is increasing interest in the identification of extracellular miRNAs in various biological fluids and spent in vitro culture media. This review focuses on studies addressing the expression and potential role of cellular and extracellular miRNAs in mammalian follicular cell physiology and subsequent ovarian functionality and oocyte maturation.

Profile of MicroRNA Expression in Endometrial Cell during In Vitro Culture According to Progesterone Concentration

Artificial uterus using endometrium implant can be a novel treatment strategy for infertile women with refractory endometrial dysfunction. At early pregnancy, the function of uterine endometrial cells for the communication between the conceptus of pre-implantation period and maternal reproductive system is essential. MicroRNA (miR) expression profile of endometrial cells according to progesterone, a crucial pregnancy-maintaining hormone, provides important data for in vitro endometrial cell culture strategy that is useful for engineering artificial uteri using endometrial implants. The present study aimed to evaluate the miR expression profile of in vitro cultured endometrial cells under hormonal milieu mimicking early pregnancy period in terms of progesterone concentration. We cultured murine uterine endometrial cells, human uterine endometrial carcinoma cells, and immortalized human uterine endometrial cells using different progesterone concentrations, and analyzed the expression of miRs critical for early pregnancy. The expression of miR-20a, -21, -196a, -199a, and -200a was differently regulated according to progesterone concentration in different endometrial cell lines. The analysis of candidate target genes showed that the expression of phosphatase and tensin homolog, mucin 1 (MUC1), progesterone receptor, transforming growth factor β receptor II, matrix metallopeptidase-9 was up-regulated by progesterone treatment in mouse and human endometrial cell lines. These results indicate that physiological concentration range (10-7 and 10-9 M) of progesterone affect the survival and target gene expression via modulating miR expression. Taken together, progesterone can be a crucial factor in regulating miR expression on in vitro cultured endometrial cells.

MiR-362-3p inhibits the proliferation and migration of vascular smooth muscle cells in atherosclerosis by targeting ADAMTS1

Atherosclerosis is a progressive condition of the large arteries that can cause coronary artery disease (CAD). Growing amounts of evidence have indicated that microRNAs (miRNAs, miRs) can be used as diagnostic biomarkers in many cellular processes associated with CAD. MiR-362-3p has been implicated in many biological cellular functions. However, little is known about the role of miR-362-3p during atherosclerosis. In the present study, significant downregulation of miR-362-3p was observed in 110 atherosclerotic CAD patients and not in the 84 controls. The upregulation of miR-362-3p was demonstrated to inhibit vascular smooth muscle cell (VSMC) proliferation and migration, and impede the G1/S cell cycle transition. Bioinformatics analysis indicated that a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) was a direct target of miR-362-3p. Subsequent experiments demonstrated that miR-362-3p binds to the 3'-untranslated region (UTR) of ADAMTS1 and decreases its levels of mRNA and protein expression. Overexpression of ADAMTS1 partially restored the miR-362-3p-mediated inhibition of VSMC proliferation, cell cycle, and migration. Upregulation of ADAMTS1 in plasma samples was detected in atherosclerotic CAD patients. Taken together, our findings suggested that miR-362-3p inhibits the proliferation and migration of VSMCs by directly targeting ADAMTS1, which might provide novel insight into the molecular mechanisms underlying the action of miR-362-3p in atherosclerosis.

Endocrine Regulation in the Ovary by MicroRNA during the Estrous Cycle

Hormonal control of the estrous cycle that occurs in therian mammals is essential for the production of a functional egg. Supporting somatic cell types found within the ovary, such as granulosa and theca cells, respond to endocrine signals to support oocyte maturation and ovulation. Following the release of the egg, now available for fertilization, coordinated hormonal signaling between the mother and putative embryo are required for the establishment of pregnancy. If no conception occurs, both the ovary and uterus are "reset" in preparation for another cycle. The complex molecular changes that occur within cells in response to hormone signaling include a network of non-coding microRNAs (miRNAs) that posttranscriptionally regulate gene expression. They are thus able to fine-tune cellular responses to hormones and confer robustness in gene regulation. In this review, we outline the important roles established for miRNAs in regulating female reproductive hormone signaling during estrus, with a particular focus on signaling pathways in the ovary. Understanding this miRNA network can provide important insights to improving assisted reproductive technologies and may be useful in the diagnosis of female reproductive disorders.