Circadian desynchronization in pregnancy of Golden hamster following long time light exposure: Involvement of Akt/FoxO1 pathway

The Role of MicroRNA, Long Non-Coding RNA and Circular RNA in the Pathogenesis of Polycystic Ovary Syndrome: A Literature Review

Polycystic ovary syndrome (PCOS) is the most common endocrine-metabolic disease in females of reproductive age, affecting 4-20% of pre-menopausal women worldwide. MicroRNAs (miRNAs) are endogenous, single-stranded, non-coding, regulatory ribonucleic acid molecules found in eukaryotic cells. Abnormal miRNA expression has been associated with several diseases and could possibly explain their underlying pathophysiology. MiRNAs have been extensively studied for their potential diagnostic, prognostic, and therapeutic uses in many diseases, such as type 2 diabetes, obesity, cardiovascular disease, PCOS, and endometriosis. In women with PCOS, miRNAs were found to be abnormally expressed in theca cells, follicular fluid, granulosa cells, peripheral blood leukocytes, serum, and adipose tissue when compared to those without PCOS, making miRNAs a useful potential biomarker for the disease. Key pathways involved in PCOS, such as folliculogenesis, steroidogenesis, and cellular adhesion, are regulated by miRNA. This also highlights their importance as potential prognostic markers. In addition, recent evidence suggests a role for miRNAs in regulating the circadian rhythm (CR). CR is crucial for regulating reproduction through the various functions of the hypothalamic-pituitary-gonadal (HPG) axis and the ovaries. A disordered CR affects reproductive outcomes by inducing insulin resistance, oxidative stress, and systemic inflammation. Moreover, miRNAs were demonstrated to interact with lncRNA and circRNAs, which are thought to play a role in the pathogenesis of PCOS. This review discusses what is currently understood about miRNAs in PCOS, the cellular pathways involved, and their potential role as biomarkers and therapeutic targets.

CLOCK inhibits the proliferation of porcine ovarian granulosa cells by targeting ASB9

BACKGROUND

Clock circadian regulator (CLOCK) is a core factor of the mammalian biological clock system in regulating female fertility and ovarian physiology. However, CLOCK's specific function and molecular mechanism in porcine granulosa cells (GCs) remain unclear. In this study, we focused on CLOCK's effects on GC proliferation.

RESULTS

CLOCK significantly inhibited cell proliferation in porcine GCs. CLOCK decreased the expression of cell cycle-related genes, including CCNB1, CCNE1, and CDK4 at the mRNA and protein levels. CDKN1A levels were upregulated by CLOCK. ASB9 is a newly-identified target of CLOCK that inhibits GC proliferation; CLOCK binds to the E-box element in the ASB9 promoter.

CONCLUSIONS

These findings suggest that CLOCK inhibits the proliferation of porcine ovarian GCs by increasing ASB9 level.

Mitochondrial function and E2 synthesis are impaired following alteration of CLOCK gene expression in porcine ovarian granulosa cells

Circadian locomotor output cycles kaput (CLOCK) is a critical component of the mammalian circadian clock system and regulates ovarian physiology. However, the functions and mechanisms of CLOCK in porcine granulosa cells (GCs) are poorly understood. The present study focused on CLOCK's effects on estradiol synthesis. Similarity analysis showed that CLOCK is highly conserved between pigs and other species. The phylogenetic tree analysis indicated that porcine CLOCK was most closely related to that in Arabian camels. CLOCK significantly reduced E₂ synthesis in GCs. CLOCK reduced the expression of steroidogenesis-related genes at the mRNA and protein levels, including CYP19A1, CYP11A1, and StAR. CYP17A1 levels were significantly downregulated. We demonstrated that CLOCK dramatically decreased ATP content, mitochondrial copy number, and mitochondrial membrane potential (MMP) and increased reactive oxygen species levels in GCs. We observed that mitochondria were severely damaged with fuzzy and fractured cristae and swollen matrix. These findings suggest that mitochondrial function and E₂ synthesis are impaired following the alteration of CLOCK gene expression in porcine ovarian GCs.

Continuous light exposure influences luteinization and luteal function of ovary in ICR mice

With the rapid change of people's lifestyle, more childbearing couples live with irregular schedules (i.e., staying up late) and suffer from decreased fertility and abortion, which can be caused by luteal phase defect (LPD). We used continuous light-exposed mice as a model to observe whether continuous light exposure may affect luteinization and luteal function. We showed that the level of progesterone in serum reduced (p < .001), the number of corpus luteum (CL) decreased (p < .01), and the expressions of luteinization-related genes (Lhcgr, Star, Ptgfr, and Runx2), clock genes (Clock and Per1), and Mt1 were downregulated (p < .05) in the ovaries of mice exposed to continuous light, suggesting that continuous light exposure induces defects in luteinization and luteal functions. Strikingly, injection of melatonin (3 mg/kg) could improve luteal functions in continuous light-exposed mice. Moreover, we found that, after 2 h of hCG injection, the level of pERK1/2 in the ovary decreased in the continuous light group, but increased in the melatonin administration group, suggesting that melatonin can improve LPD caused by continuous light exposure through activating the ERK1/2 pathway. In summary, our data demonstrate that continuous light exposure affects ovary luteinization and luteal function, which can be rescued by melatonin.

Therapeutic potential of exosomes/miRNAs in polycystic ovary syndrome induced by the alteration of circadian rhythms

Polycystic ovary syndrome (PCOS) is a reproductive dysfunction associated with endocrine disorders and is most common in women of reproductive age. Clinical and/or biochemical manifestations include hyperandrogenism, persistent anovulation, polycystic ovary, insulin resistance, and obesity. Presently, the aetiology and pathogenesis of PCOS remain unclear. In recent years, the role of circadian rhythm changes in PCOS has garnered considerable attention. Changes in circadian rhythm can trigger PCOS through mechanisms such as oxidative stress and inflammation; however, the specific mechanisms are unclear. Exosomes are vesicles with sizes ranging from 30-120nm that mediate intercellular communication by transporting microRNAs (miRNAs), proteins, mRNAs, DNA, or lipids to target cells and are widely involved in the regulation of various physiological and pathological processes. Circadian rhythm can alter circulating exosomes, leading to a series of related changes and physiological dysfunctions. Therefore, we speculate that circadian rhythm-induced changes in circulating exosomes may be involved in PCOS pathogenesis. In this review, we summarize the possible roles of exosomes and their derived microRNAs in the occurrence and development of PCOS and discuss their possible mechanisms, providing insights into the potential role of exosomes for PCOS treatment.