Activation of PPARG inhibits dominant follicle development in cattle

gga-miR-6634-5p Affects the proliferation and steroid hormone secretion of chicken (Gallus Gallus) granulosa cells by targeting MMP16

MiRNAs are typically reported to play a negative regulatory role in post-transcriptional expression of target genes and are widely involved in a variety of biological processes such as growth, metabolism and reproduction. However, research on the role of miRNAs in the ovulation process of chicken ovaries is still insufficient compared to that in mammals. Here, we investigated the regulatory mechanisms of gga-miR-6634-5p in the growth and steroid hormone secretion of chicken granulosa cells (GCs) by targeting MMP16. We found that gga-miR-6634-5p significantly down-regulated the mRNA levels of proliferation-related genes (CCND1, CDK1, and CDK6), decreased cell viability, the number of EdU-labelled positive cells, and the percentage of S-phase cells, as analysed by quantitative real time PCR (qRT-PCR), cell counting kit-8 (CCK-8), 5-ethynyl-2'deoxyuridine (EdU) and flow cytometry analyses (P < 0.01 or P < 0.05). qRT-PCR and enzyme-linked immunosorbent assay (ELISA) results demonstrated that gga-miR-6634-5p up-regulated the expression of steroid synthesis-related genes (CYP19A1, 3β-HSD, StAR and FSHR) (P < 0.01 or P < 0.05), as well as the secretion of estradiol (E2) and progesterone (P4) (P < 0.01 or P < 0.05). Furthermore, we found that MMP16 protein and gene expression can be down-regulated by gga-miR-6634-5p and demonstrated that MMP16 is a target gene of gga-miR-6634-5p by dual luciferase reporter assay (P < 0.05). In addition, we found that MMP16 stimulated the proliferation of GCs, significantly inhibited the expression of steroid synthesis related genes (CYP19A1, StAR, 3β-HSD and FSHR), and decreased the secretion of E2 and P4 (P < 0.01 or P < 0.05), which was consistent with the inhibitory effect of gga-miR-6634-5p. It was further found by functional enrichment analysis, qRT-PCR, western blot (WB) and ELISA that MMP16 may play a regulatory role in GCs proliferation as well as steroid hormone secretion through the mTOR signaling pathway and PPAR signaling pathway. Therefore, this study demonstrates that gga-miR-6634-5p modulates the proliferation of chicken GCs and the secretion of steroid hormones by targeting MMP16, which may contribute to a better understanding of the functional mechanisms of miRNAs in the ovarian development of laying hens.

tsRNA-00764 Regulates Estrogen and Progesterone Synthesis and Lipid Deposition by Targeting PPAR-γ in Duck Granulosa Cells

Transfer RNA-derived small RNAs (tsRNAs) are novel regulatory small non-coding RNAs that have been found to modulate many life activities in recent years. However, the exact functions of tsRNAs in follicle development remain unclear. Follicle development is a remarkably complex process that follows a strict hierarchy and is strongly associated with reproductive performance in ducks. The process of converting small yellow follicles into hierarchal follicles is known as follicle selection, which directly determines the number of mature follicles. We performed small RNA sequencing during follicle selection in ducks and identified tsRNA-00764 as the target of interest based on tsRNA expression profiles in this study. Bioinformatics analyses and luciferase reporter assays further revealed that peroxisome proliferator-activated receptor-γ (PPAR-γ) was the target gene of tsRNA-00764. Moreover, tsRNA-00764 knockdown promoted estrogen and progesterone synthesis and lipid deposition in duck granulosa cells, while a PPAR-γ inhibitor reversed the above phenomenon. Taken together, these results demonstrate that tsRNA-00764, differentially expressed in pre-hierarchal and hierarchy follicles, modulates estrogen and progesterone synthesis and lipid deposition by targeting PPAR-γ in duck granulosa cells, serving as a potential novel mechanism of follicle selection. Overall, our findings provide a theoretical foundation for further exploration of the molecular mechanisms underlying follicle development and production performance in ducks.

Sohlh1 and Lhx8 are prominent biomarkers to estimate the primordial follicle pool in mice

Efficient evaluation of the primordial follicle pool (PFP) of mammalian models is an essential subject in biomedical research relating to ovarian physiology and pathogenesis. Our recent study has identified a gene signature including Sohlh1, Nobox, Lhx8, Tbpl2, Stk31, Padi6, and Vrtn strongly correlated with ovarian reserve by using bioinformatics analysis. Aimed to investigate the validity of these candidate biomarkers for evaluating the PFP, we utilized an OR comparison model to decode the relationship between the numbers of PFP and candidate biomarkers in the present study. Our results suggest that these biomarkers Sohlh1, Nobox, Lhx8, Tbpl2, Stk31, Padi6, and Vrtn possess independent potential to evaluate the number of the PFP. And the combination of Sohlh1 and Lhx8 can be used as the optimal biomarkers for rapid assessment of the PFP in the murine ovary. Our findings provide a new perspective for evaluating the PFP of the ovary in animal studies and the clinic.

miR-128-3p regulates chicken granulosa cell function via 14-3-3β/FoxO and PPAR-γ/LPL signaling pathways

MicroRNAs (miRNAs) are class of 22 nt short RNA sequences which inhibit protein translation through binding to the 3'UTR of its target genes. The continuous ovulatory property of chicken follicle makes it a perfect model for studying granulosa cell (GC) functions. In this study, we found that large number of miRNAs including miR-128-3p, were differentially expressed in the GCs of F1 and F5 follicles of chicken. Subsequently, the results revealed that miR-128-3p inhibited proliferation, the formation of lipid droplets, and hormone secretion in chicken primary GCs through directly targeting YWHAB and PPAR-γ genes. To determine the effects of 14-3-3β (encoded by YWHAB) protein on GCs functions, we overexpressed or inhibited the expression of YWHAB, and the results showed that YWHAB inhibited the function of FoxO proteins. Collectively, we found that miR-128-3p was highly expressed in the chicken F1 follicles compared to the F5 follicles. In addition, the results indicated that miR-128-3p promoted GC apoptosis through 14-3-3β/FoxO pathway via repressing YWHAB, and inhibited lipid synthesis by impeding the PPAR-γ/LPL pathway, as well as reduced the secretion of progesterone and estrogen. Taken together, the results showed that miR-128-3p plays a regulatory role in chicken granulosa cell function via 14-3-3β/FoxO and PPAR-γ/LPL signaling pathways.

Contribution of key elements of nutritional metabolism to the development of cystic ovarian disease in dairy cattle

The alteration of signaling molecules involved in the general metabolism of animals can negatively influence reproduction. In dairy cattle, the development of follicular cysts and the subsequent appearance of ovarian cystic disease (COD) often lead to decreased reproductive efficiency in the herd. The objective of this review is to summarize the contribution of relevant metabolic and nutritional sensors to the development of COD in dairy cows. In particular, we focus on the study of alterations of the insulin signaling pathway, adiponectin, and other sensors and metabolites relevant to ovarian functionality, which may be related to the development of follicular persistence and follicular formation of cysts in dairy cattle. The results of these studies support the hypothesis that systemic factors could alter the local scenario in the follicle, generating an adverse microenvironment for the resumption of ovarian activity and possibly leading to the persistence of follicles and to the development and recurrence of COD.

Supplementation of oleic acid, stearic acid, palmitic acid and β-hydroxybutyrate increase H3K9me3 in endometrial epithelial cells of cattle cultured in vitro

There is growing evidence that greater than homeostatic blood concentrations of nonesterified fatty acids (NEFAs) and β-hydroxybutyrate (BHBA) have negative consequences on dairy cow's fertility, but effects on cell homeostasis in the reproductive system is not completely understood. In this study, lipids accumulation, reactive oxygen species (ROS) concentrations, abundance of gene transcripts, and immunofluorescence signal of H3K4me3 and H3K9me3 were evaluated in endometrial epithelial cells of cattle cultured with NEFAs (Oleic (OA), Stearic (SA) and Palmitic (PA) acids), BHBA, NEFAs + BHBA or each of the three NEFAs alone. The cellular lipids were in greater concentrations as a result of NEFAs + BHBA, NEFAs, SA or OA supplementation, but not by BHBA or PA. The ROS concentrations were greater when there were treatments with NEFAs + BHBA, NEFAs or BHBA. The relative mRNA abundance for genes involved in the regulation of apoptosis (XIAP), glucose transport (GLUT3), and DNA methylation (DNMT1) were greater when there were NEFAs + BHBA, but not NEFAs, BHBA, OA, SA or PA treatments. The immunofluorescence signal for H3K9me3 was greater when there were NEFAs + BHBA, NEFAs or PA, but not by BHBA, OA or SA treatments. These findings indicate that NEFAs and BHBA have an additive effect on endometrial cells of cattle by altering epigenetic markers and the expression of genes controlling important cellular pathways. Furthermore, there was cellular lipid accumulation and increased H3K9me3 in cultured bovine endometrial cells that was mainly induced by OA and PA treatments, respectively.

Integration of transcriptomics and non-targeted metabolomics reveals the underlying mechanism of follicular atresia in Chinese buffalo

Follicular atresia is a complex physiological process, which results in the waste of follicles and oocytes from the ovary. Elucidating the physiological mechanism of follicular atresia will hopefully reverse the fate of follicles, thereby improve the reproductive efficiency of female animals. However, there are still many gaps to be filled during the follicular atresia process. In this study, we first comprehensively summarized and compared a variety of methods to classify Chinese buffalo follicles with different extent of atresia. Then follicular fluid and granulosa cells from the corresponding follicles with different extent of atresia were collected for non-targeted metabolomics and transcriptomics analysis, respectively. After the detection and analysis of 129 follicles, a reasonable classification standard was formed: on the basis of morphological classification, the relative concentrations of estradiol (E2) and progesterone (PROG) in the follicular fluid were determined, follicles with an estradiol-to-progesterone (E2/PROG) ratio >5 were classified as healthy follicles (HF), 1≤ E2/PROG ≤5 as early atretic follicles (EF) and E2/PROG <1 as late atretic follicles (LF). Correspondingly, follicles with granulosa cells apoptosis rate less than 15 % were divided into HF, 15%-25% were classified as EF and more than 25 % were classified as LF. The integration analysis of non-targeted metabolomics and transcriptomics highlights the following three aspects: (1) Atresia seriously damaged the lipid metabolism homeostasis of follicle, in which PPARγ play important roles. (2) Energy metabolism and nucleotide metabolism of atretic follicles were inhibited. (3) Bilirubin is involved in follicular atresia, and it may be the main force to prevent lipid peroxidation in follicular cells. In summary, results of this study provide new understanding of the molecular mechanisms of Chinese buffalo follicular atresia.

Intrafollicular injection of nonesterified fatty acids impaired dominant follicle growth in cattle

Dairy cows frequently undergo a state of negative energy balance (NEB) after parturition and some have impaired ovarian functions that result in delayed resumption of estrous cyclicity and development of follicles without ovulation occurring. During the postpartum period, cows undergo body-fat store losses, hormonal changes, fat mobilization and increases in nonesterified fatty acid (NEFAs) concentrations in blood and follicular fluid. The effect of NEFAs on follicular development and function of follicular cells, however, is not fully understood. The aim of this study, therefore, was to study the effect of an intrafollicular injection of a mixture of oleic, stearic and palmitic NEFAs on dominant follicle development and function of granulosa cells in cows that were not in a NEB state. Follicular size was less at 24 and 48 h after administration of NEFAs compared to that of control follicles injected with vehicle only. At 24 h after intrafollicular injection, the relative mRNA transcript abundance for proteins involved in steroidogenesis (CYP19A1, 3BHSD, STAR, FSHR), metabolism (GLUT1, GLUT3, INSR, IRS1, IRS2, SLC27A1, PPARG), and cell proliferation and apoptosis (CCND2; XIAP) in granulosa cells, as well as estradiol concentrations in follicular fluid were similar in control and NEFA-treated follicles. In conclusion, the results of this study indicate increased intrafollicular concentrations of NEFAs in cows that are not in a NEB state has a detrimental effect on follicle development. We propose intrafollicular injection is a useful approach to further investigate the local effects of NEFAs on the function of follicular cells.