NCBI Summary:
microRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop. [provided by RefSeq, Sep 2009]
General function
RNA binding
Comment
Human placenta-derived mesenchymal stem cells stimulate ovarian function via miR-145 and bone morphogenetic protein signaling in aged rats. Kim KH et al. (2020) Aging has detrimental effects on the ovary, such as a progressive reduction in fertility and decreased hormone production, that greatly reduce the quality of life of women. Thus, the current study was undertaken to investigate whether human placenta-derived mesenchymal stem cell (hPD-MSC) treatment can restore the decreases in folliculogenesis and ovarian function that occur with aging. Acclimatized 52-week-old female SD rats were randomly divided into four groups: single hPD-MSC (5 × 105) therapy, multiple (three times, 10-day intervals) hPD-MSC therapy, control (PBS), and non-treated groups. hPD-MSC therapy was conducted by tail vein injection into aged rats. The rats were sacrificed 1, 2, 3, and 5 weeks after the last injection. hPD-MSC tracking and follicle numbers were histologically confirmed. The serum levels of sex hormones and circulating miRNAs were detected by ELISA and qRT-PCR, respectively. TGF-β superfamily proteins and SMAD proteins in the ovary were detected by Western blot analysis. We observed that multiple transplantations of hPD-MSCs more effectively promoted primordial follicle activation and ovarian hormone (E2 and AMH) production than a single injection. After hPD-MSC therapy, the levels of miR-21-5p, miR-132-3p, and miR-212-3p, miRNAs associated with the ovarian reserve, were increased in the serum. Moreover, miRNAs (miR-16-5p, miR-34a-5p, and miR-191-5p) with known adverse effects on folliculogenesis were markedly suppressed. Importantly, the level of miR-145-5p was reduced after single- or multiple-injection hPD-MSC therapy, and we confirmed that miR-145-5p targets Bmpr2 but not Tgfbr2. Interestingly, downregulation of miR-145-5p led to an increase in BMPR2, and activation of SMAD signaling concurrently increased primordial follicle development and the number of primary and antral follicles. Our study verified that multiple intravenous injections of hPD-MSCs led to improved ovarian function via miR-145-5p and BMP-SMAD signaling and proposed the future therapeutic potential of hPD-MSCs to promote ovarian function in women at advanced age to improve their quality of life during climacterium.//////////////////
Expression Patterns and Regulatory Functions of MicroRNAs During the Initiation of Primordial Follicle Development in the Neonatal Mouse Ovary. Yang S 2013 et al.
The initiation of primordial follicle development is essential for female fertility, but the signals that trigger this process are poorly understood. Given the potentially important roles of miRNAs in the ovary, we aimed to study the expression patterns and regulatory functions of miRNAs during the initiation of primordial follicle development. miRNA expression patterns in the neonatal mouse ovary were profiled by microarray, and 24 miRNAs whose abundances differed significantly between ovaries from 3- and 5-day-old mice were identified. Pathway enrichment analysis revealed that 48 signal transduction pathways are modulated by the up-regulated miRNAs and 29 pathways are modulated by the down-regulated miRNAs (P-value and false discovery rate (FDR) < 0.001). A miRNA-mRNA regulatory network was established for TGF-beta signaling pathway-related genes. Among the miRNAs involved in this pathway, miR-145 was chosen for further analysis. Down-regulation of miR-145 using an antagomir (AT) decreased the proportion and number of the primordial follicles and increased that of the growing follicles in the cultured ovaries (P < 0.05). The mean oocyte diameter in the primordial follicles was significantly greater in the AT group relative to the antagomir negative control (AN) group (P < 0.05), whereas the mean oocyte diameter in growing follicles was smaller in the AT group than in the AN group. In addition, we confirmed that miR-145 targets Tgfbr2. The miR-145 antagomir caused an increase in TGFBR2 expression and activation of Smad signaling but did not affect the p38 MAPK or JNK pathway. These data suggest that miRNAs and the signaling pathways they modulate are involved in the initiation of primordial follicle development. miR-145 targets Tgfbr2 to regulate the initiation of primordial follicle development and maintain primordial follicle quiescence.
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MicroRNA-145 suppresses mouse granulosa cell proliferation by targeting activin receptor IB. Yan G et al. MicroRNAs (miRNAs) are a class of 21- to 25-nucleotide non-coding RNAs, some of which are important gene regulators involved in folliculogenesis. In this study, we used CCK-8, real-time PCR and Western blot assays to demonstrate that miR-145 inhibits mouse granulosa cell (mGC) proliferation. Combined with the results of luciferase reporter assays that studied the 3'-untranslated region of ACVRIB mRNA, these assays identified ACVRIB as a direct target of miR-145. The ectopic expression of miR-145 reduced the levels of both ACVRIB mRNA and protein and also interfered with activin-induced Smad2 phosphorylation. Altogether, this study revealed that miR-145 suppresses mGC proliferation by targeting ACVRIB.
Expression regulated by
Growth Factors/ cytokines, GDNF
Comment
GDNF-induced down-regulation of miR-145-5p enhances human oocyte maturation and cumulus cell viability. Cui L et al. (2018) Although glial cell line-derived neurotrophic factor (GDNF) and microRNAs (miRNAs) have been shown to regulate mammalian oocyte maturation, little is known about their effects on human oocyte maturation and the underlying molecular mechanisms. To examine the effects of GDNF on both nuclear and cytoplasmic maturation in cultured immature human oocytes and to investigate the involvement of miRNAs in GDNF-induced oocyte maturation. A total of 200 human immature oocytes were used to evaluate the effects of GDNF on oocyte maturation. The involvement of miRNAs in GDNF-induced oocyte maturation were identified by comparing the miRNA expression profiles of cumulus cells either with or without GDNF stimulation. An IVF center at the Women's Hospital, Zhejiang University School of Medicine. Agilent Human miRNA (8*60K) arrays were used to examine the miRNA expression patterns of human cumulus cells (CCs) either with or without GDNF stimulation. MiR-145-5p inhibitor and mimic transfections were performed to study downstream gene expression in human CCs. During the IVM process, GDNF significantly increased the percentage of MII-stage oocytes and down-regulated the expression of miR-145-5p in cultured human CCs. Expression of MiR-145-5p in CCs is negatively correlated with oocyte maturation. miR-145-5p mimic significantly decreased the expression of GFRA1, RET, and EGFR, whereas miR-145-5p inhibitor reversed these effects. GDNF treatment inhibited cell apoptosis in cultured CCs, and this suppressive effect was reversed by transfection with the miR-145-5p mimic. Down-regulation of miR-145-5p may contribute to GDNF-induced enhancement of oocyte maturation and of cell viability against cell apoptosis.//////////////////
MicroRNA-145 protects follicular granulosa cells against oxidative stress-induced apoptosis by targeting Krüppel-like factor 4. Xu L et al. (2017) Oxidative stress-induced follicular granulosa cell (GC) apoptosis plays an essential role in abnormal follicular atresia, which may trigger ovarian dysfunction. To investigate the role of microRNA (miR)-145 in the regulation of GC apoptosis and modulation of the apoptotic pathway in the setting of oxidative stress, we employed an H2O2-induced in vitro model and a 3-nitropropionic acid (NP)-induced in vivo model of ovarian oxidative stress. We demonstrated in vitro that miR-145 expression was significantly down-regulated in KGN cells and mouse granulosa cells (mGCs) treated with H2O2, whereas miR-145 over-expression attenuated H2O2-induced apoptosis in GCs. Moreover, miR-145 protected GCs against H2O2-induced apoptosis by targeting KLF4, which promoted H2O2-induced GC apoptosis via the BAX/BCL-2 pathway. Importantly, decreased miR-145 expression in the in vivo ovarian oxidative stress model promoted apoptosis by up-regulating KLF4 expression, whereas GC-specific miR-145 over-expression attenuated apoptosis by targeting KLF4. In conclusion, miR-145 protects GCs against oxidative stress-induced apoptosis by targeting KLF4.//////////////////
Ovarian localization
Granulosa, Ovarian tumor, Follicular Fluid
Comment
Involvement of miRNAs in equine follicle development. Schauer S 2013 et al.
Previous evidence from in vitro studies suggests specific roles for a subset of miRNAs, including miR-21, miR-23a, miR-145, miR-503, miR-224, miR-383, miR-378, miR-132 and miR-212, in regulating ovarian follicle development. The objective of this study was to determine changes in the levels of these miRNAs in relation to follicle selection, maturation and ovulation in the monovular equine ovary. In Experiment 1, follicular fluid was aspirated during ovulatory cycles from the dominant (DO) and largest subordinate (S) follicles of an ovulatory wave, and the dominant (DA) follicle of a mid-cycle anovulatory wave (n=6 mares). Follicular fluid levels of progesterone and estradiol were lower (P<0.01) in S follicles than in DO follicles, whereas mean levels of IGF1 were lower (P<0.01) in S and DA follicles than in DO follicles. Relative to DO and DA follicles, S follicles had higher (P=0.01) follicular fluid levels of miR-145 and miR-378. In Experiment 2, follicular fluid and granulosa cells were aspirated from dominant follicles before (DO) and 24h after (L) administration of an ovulatory dose of hCG (n=5 mares/group). Relative to DO follicles, L follicles had higher follicular fluid levels of progesterone (P=0.05) and lower granulosa cell levels of CYP19A1 and LHCGR (P<0.005). Levels of miR-21, miR-132, miR-212 and miR-224 were increased (P<0.05) in L follicles; this was associated with reduced expression of the putative miRNA targets, PTEN, RASA1 and SMAD4. These novel results may indicate a physiological involvement of miR-21, miR-145, miR-224, miR-378, miR-132 and miR-212 in the regulation of cell survival, steroidogenesis and differentiation during follicle selection and ovulation in the monovular ovary.
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Does expression of the retrogene UTP14c in the ovary pre-dispose women to ovarian cancer? Rohozinski J et al. It has been previously shown that the spermatogenesis associated retrogene, UTP14c, is expressed in over 50% of normal human ovaries and 80% of ovarian cancers. UTP14c is located on chromosome 13 as an intronless copy of the X-linked housekeeping gene, UTP14a. Like all spermatogenesis associated retrogenes, UTP14c is expressed in the testis and is essential for sperm production. It has no known role in the female and is not normally expressed in any cells or organs outside of the gonads. By comparison the protein encoded by UTP14a is found in all cell types and has a dual function. It is primarily involved in the biosynthesis of 18S ribosomal RNA in the nucleolus where it is a component of the U3 small nucleolar RNA associated protein complex. In addition, it down regulates TP53 in both the nucleus and cytoplasm by targeting it for proteolytic degradation. By analogy, we propose that the UTP14c peptide also targets TP53 for degradation. This in turn may prevent cells expressing UTP14c from entering apoptosis. The loss of TP53 in ovarian cells can also result in the down regulation of microRNA-145 (miR-145) expression. The loss of miR-145 can result in the activation of factors that promote oncogenesis and cellular pluripotency which in turn could lead to the development of ovarian cancer. We hypothesize that women, whose ovaries express UTP14c, are predisposed to ovarian cancer due to the disruption of protective signals that normally trigger TP53-mediated apoptosis and the dysregulation of genes that promote oncogenesis, such as c-Myc, that occurs when miR-145 synthesis is disrupted.