MicroRNAs regulate granulosa cells apoptosis and follicular development - A review

The regulatory roles of Smad2/3 protein and SMURF2 gene expression in granulosa cells of germinal vesicle and metaphase II oocytes in polycystic ovarian syndrome: A case-control study

Background

The impaired functions of granulosa cells (GCs) in the delayed development and immaturity of oocytes have been reported in polycystic ovary syndrome (PCOs). Even with ovarian stimulation, a large number of oocytes in these patients are still in the stage germinal vesicle (GV).

Objective

The levels of Smad2/3, phosphorylated Smad2/3 (P-Smad2/3), the expression of SARA, Smad4, and SMURF2 genes in the GCs surrounding metaphase II (MII) or GV oocytes in PCOs women were investigated.

Materials and Methods

GCs of MII and GV oocytes were isolated from 38 women with PCOs and the expression levels of SARA, Smad4, and SMURF2 in surrounding GCs of MII and GV oocytes were determined using reverse-transcription polymerase chain reaction. Also, Smad2/3 and P-Smad2/3 proteins were determined using western blotting.

Results

The expression level of SMURF2 was significantly higher in GCs surrounding GV oocytes compared with that of GCs encompassing MII oocytes (p < 0.001). At the same time, no significant differences were observed in SARA and Smad4 expression levels in GCs surrounding GV and MII oocytes. A lower level of P-Smad2/3 was also found in GCs GV oocytes compared with GCs of MII oocytes (p < 0.001).

Conclusion

It seems that P-Smad2/3 plays a role in oocyte development, and the downregulation of this protein is associated with a defect in the maturation of GV oocytes. On the other hand, the upregulation of the SMURF2 gene also affects the growth process of GCs and the maturation of GV oocytes.

miRNA expression in PCOS: unveiling a paradigm shift toward biomarker discovery

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder that affects a substantial percentage of women, estimated at around 9-21%. This condition can lead to anovulatory infertility in women of childbearing age and is often accompanied by various metabolic disturbances, including hyperandrogenism, insulin resistance, obesity, type-2 diabetes, and elevated cholesterol levels. The development of PCOS is influenced by a combination of epigenetic alterations, genetic mutations, and changes in the expression of non-coding RNAs, particularly microRNAs (miRNAs). MicroRNAs, commonly referred to as non-coding RNAs, are approximately 22 nucleotides in length and primarily function in post-transcriptional gene regulation, facilitating mRNA degradation and repressing translation. Their dynamic expression in different cells and tissues contributes to the regulation of various biological and cellular pathways. As a result, they have become pivotal biomarkers for various diseases, including PCOS, demonstrating intricate associations with diverse health conditions. The aberrant expression of miRNAs has been detected in the serum of women with PCOS, with overexpression and dysregulation of these miRNAs playing a central role in the atypical expression of endocrine hormones linked to PCOS. This review takes a comprehensive approach to explore the upregulation and downregulation of various miRNAs present in ovarian follicular cells, granulosa cells, and theca cells of women diagnosed with PCOS. Furthermore, it discusses the potential for a theragnostic approach using miRNAs to better understand and manage PCOS.

Bushen Tianjing Recipe inhibits human ovarian granulosa cell line KGN apoptosis induced by miR-23a through the regulation of the sirtuin family

ETHNOPHARMACOLOGICAL RELEVANCE

Bushen Tianjing Recipe (BTR) is a tonic-kidney formula of Traditional Chinese Medicine (TCM) with good therapeutic effects in clinical settings. It was mainly applied to inhibit the decrease of ovarian reserve function in patients. However, the anti-apoptosis mechanism of BTR remains unknown.

AIM OF THE STUDY

The formula of BTR is composed of prepared rehmannia root, debark peony root, carapax testudinis and asiatic cornelian cherry fruit. All four components contain the essences of nourishing yin and tonic-kidney. In the theory of TCM, the kidneys store the essence and are primarily responsible for reproduction and development. Hence, we speculated that BTR had some effect on women's reproductive system. In our research, rat serum contains BTR resolved into culture medium for incubation with miR-23a-induced KGN cells to test and determine our hypothesis.

MATERIALS AND METHODS

BTR was prepared by the traditional decoction method to collect concentrated liquids for oral administration to rats (15.00 g/kg) for 14 days. The group with miR-23a-induced KGN cells was selected as the positive control, while the mimic one was the control. Pro-apoptosis and anti-apoptosis biomarkers were detected and analyzed by western blot together with upstream transcription factors and intracellular apoptotic signal pathways.

RESULTS

The medium- and high-concentration of BRT greatly reduced the apoptosis of miR-23a-induced KGN cells both in mitochondria and cytoplasm. It showed the up-regulation of SIRT1 and SIRT3, the down-regulation of pro-apoptosis factor Bax and apoptotic-related proteins Caspase 3, 8, 9, and the reduction of phosphorylation of ERK1/2 and NF-κB. however, there was no consistency in the group with a low concentration of BTR, compared with those of other groups.

CONCLUSION

Our research verified that BTR had a positive effect on women's reproductive system under medium or high concentration, illuminated the intrinsic mechanism at molecular levels, and convinced its potential application values in clinical settings.

Evaluation of the potential of miR-21 as a diagnostic marker for oocyte maturity and embryo quality in women undergoing ICSI

MicroRNAs are small molecules that play a crucial role in regulating a woman's reproductive system. The present study evaluates the expression of miR-21 in the serum, follicular fluid (FF), and cumulus cells (CCs) and their association with oocyte maturity and embryo quality in women undergoing intracytoplasmic sperm injection. Women subjects were divided into the case (54 Patients with female factor infertility) and control groups (33 patients with male factor infertility). The level of miR-21 was measured using Real-Time PCR. The level of miR-21 was significantly lower in the CCs, FF, and serum in the case compared to the control group (p < 0.05). MiR-21 abundance was higher in FF and CCs samples than in serum. Furthermore, there was a significant increase in CCs to FF in the case group (p < 0.05). A significant decrease in oocyte count, MII oocytes, and percentage of mature oocytes were observed in the case group (p < 0.05). The expression of miR-21 in FF and CCs was positively related to oocyte maturation, but no correlation with embryo development was observed. This study found that miR-21 is expressed less in women with female factor infertility, and human oocytes' development is crucially affected by the expression of miR-21. Therefore, miR-21 could provide new helpful biomarkers of oocyte maturity.

miR-21, miR-125b, and let-7b contribute to the involution of atretic follicles and corpus lutea in Tibetan sheep ovaries

Follicular granulosa cells (FGCs) are crucial for ovarian follicle functions, and miRNAs are differentially expressed at various stages of follicular developments. In this study, we confirmed that miR-21, miR-125b, and let-7b were located in FGCs/luteal cells by in situ hybridization experiments. Moreover, miR-21 and miR-125b expressions were upregulated in late corpus lutea (CL) and atretic follicles (AF); let-7b expression was increased in early AF. After transfected with inhibitor or mimic of miRNAs in FGCs, we found that FGCs apoptosis was decreased in the miR-21-mi group but increased in the miR-125b-mi group using flow cytometry. mRNA and protein expression levels were determined for apoptosis-related factors (e.g., Bcl-2 and Bax), the potential target genes of miRNAs (e.g., SMAD7, SP1, and STAT3), hormone receptors (e.g., FSHR and LHR), and genes related to hormone secretion (e.g., CYP19, CYP11, and 3βHSD). The protein levels of SMAD7 were decreased in the miR-21-mi group but opposite to SP1 and FSHR. In the let-7b-mi group, Bcl-2, SMAD7, and FSHR were suppressed but not Bax, CYP11, and 3βHSD. However, hormone secretion was not changed in the supernatant of transfected FGCs. This study provides information about ovarian miRNAs to improve the fertility in Tibetan sheep.

MicroRNA-21 is involved in oocyte maturation, blastocyst formation, and pre-implantation embryo development

Follicular fluid is one source of microRNAs (miRNAs). These miRNAs originate from oocytes and their neighboring cells. The changes in the miRNAs profile in the follicular fluid could alter folliculogenesis and oocyte maturation, and lead to infertility. Polycystic ovary syndrome (PCOS) patients have increased miR-21 levels in their sera, granulosa cells, and follicular fluid, and this mi-RNA plays a role in the pathophysiology and follicular dysfunction of PCOS patients. In the current study, we intend to examine whether expression levels of miR-21 influence oocyte maturation and embryo development. We examined miR-21 over-expression and down-regulation of miR-21 by miR-off 21 during in vitro maturation (IVM) to assess its influence on oocyte maturation and embryo development in mice. Over-expression of miR-21 in cumulus cells decreased expansion, meiotic progression, Glutathione-S-transferase GSH levels, and decreased expressions of Bmpr2 and Ptx3 genes. Subsequently, we noted that in vitro fertilization, and the cleavage rate and blastocyst formation significantly increased in cumulus oocyte complexes (COCs) that over-expressed miR-21. Inhibition of miR-21 by miR-off 21 led to increased cumulus expansion and GSH levels, along with decreased cleavage rate and blastocyst formation by alterations in Cdk2ap1 and Oct4 gene expressions. However, oocyte progression from the germinal vesicle (GV) to the metaphase II (MII) stage was not significant. miR-21 altered the gene expression levels in cumulus cells and influenced cytoplasmic oocyte maturation, cumulus expansion, and subsequent embryonic development in mice.

Abnormal Expression of microRNA-296-3p in Type 2 Diabetes Patients and its Role in Pancreatic β-Cells Function by Targeting Tensin Homolog Deleted on Chromosome Ten

Diabetes mellitus (DM), a familiar disease, is characterized by high blood glucose levels owing to insulin deficiency. Researches have suggested that the incidence rate of diabetes is increasing and it has become an important global epidemic. The type 2 diabetes mellitus (T2DM) is featured with pancreatic β-cell loss and lack of insulin release. Nevertheless, the therapeutic methods that was helpful to improve pancreatic β-cell damage still unclear. Previous report have revealed that tensin homolog deleted on chromosome ten (PTEN) was remarkably enhanced in serum of patients with T2DM, and the lack of PTEN may prevent function deficiency of pancreatic β-cells in DM. However, the underlying mechanisms are rarely illustrated. Our purpose in this report was to illustrated the roles and potential mechanism of microRNA-296-3p (miR-296-3p) in uric acid (UA)-induced pancreatic β-cell injury. The direct target of miR-296-3p was predicted and verified by dual-luciferase reporter system and TargetScan assay. Moreover, Min6 cells were induced by 5 mg/dl UA and the cell proliferation, apoptosis, and insulin release were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry and glucose-stimulated insulin secretion (GSIS), respectively. Quantitative reverse transcription PCR (qRT-PCR) and western blot assay were adopted to analyze the levels of miR-296-3p, PTEN and apoptosis-related proteins. TargetScan and Dual-luciferase reporter system confirmed that PTEN directly target miR-296-3p. MiR-296-3p was downregulated in UA-induced Min6 cells and the serum of type 2 diabetes patients, while PTEN was upregulated in UA-induced Min6 cells. Upregulation of miR-296-3p by mimic dramatically promoted miR-296-3p level and decreased PTEN level. Besides, PTEN was over-expressed after PTEN-plasmid transfection. UA treatment prominently decreased cell viability, promoted apoptotic cells, enhanced Bax levels, declined Bcl-2 level as well as decreased insulin release in Min6 cells. MiR-296-3p mimic significantly alleviated UA-induced pancreatic β-cells dysfunction, and PTEN-plasmid eliminated the protective effect of miR-296-3p on insulin release, cell viability, and apoptosis of pancreatic β-cells in UA-stimulated Min6 cells. In summary, our findings revealed that upregulation of miR-296-3p protected pancreatic β-cells functions against UA-induced dysfunction by targeting PTEN, which provides a novel agent for type 2 diabetes treatment.

MicroRNA-21 inhibits ovarian granulosa cell proliferation by targeting SNHG7 in premature ovarian failure with polycystic ovary syndrome

microRNA (miRs or miRNAs) is a type of non-coding RNA which plays the role of a regulator in gene expression. A number of miRNAs has been found by the researchers for its critical role in the pathogenesis of polycystic ovary syndrome (PCOS). But there is a no clear information available about the biological role played by miR-21 in PCOS prognosis. So, the aim of the current study is to determine the role played by miR-21 in the progression of PCOS. In order to achieve this aim, the researcher examined miR-21 expression levels in ovarian tissue samples collected from PCOS patients as well as their KGN cells (human granulosa-like tumor cell line). The study results inferred downregulation in the expression levels of miR-21 in ovarian tissues of PCOS patients and KGN cells, when compared with unaffected ovarian tissues and IOSE80 (human ovarian surface epithelial cell line). With the overexpression of miR-21, the proliferation of KGN cells was prevented and apoptosis was induced among these cells. The authors used StarBase analysis for predicting the direct binding target of miR-21. As per the assay results attained from luciferase reporter assay and western blot analysis, it was found that SNHG7 acted as a target gene for miR-21 while the latter downregulated the former. To conclude, the current study revealed the contribution of miR-21/SNHG7 axis in the regulation of Granulosa Cell (GC) proliferation and apoptosis. It further suggested a new molecular mechanism for GC dysregulation while the finding presents a new promising target for PCOS treatment procedure.