miRNA sequencing analysis of healthy and atretic follicles of chickens revealed that miR-30a-5p inhibits granulosa cell death via targeting Beclin1

MiR-302c-3p regulates autophagy and apoptosis in ovarian granulosa cells via the LATS2/YAP axis in chickens

The degenerative process of follicular atresia in hens naturally commences in granulosa cells, significantly impacting laying hens' reproductive performance. Past studies suggested that granulosa cell autophagy and apoptosis work together to cause follicular atresia. Recent research indicates that miRNA regulates granulosa autophagy and apoptosis, which contributes to the development of follicular atresia. However, the role of miR-302c-3p in follicular atresia and development remains unclear. In this study with the RNA-seq approach, we found that miR-302c-3p expression was significantly decreased in atrophic follicles, suggesting its involvement in the follicular atresia process. Following this, we performed in vitro studies to confirm that miR-302c-3p inhibits autophagy and apoptosis in chicken granulosa cells. Mechanistically, LATS2 is considered as the putative target gene of miR-302c-3p, and it has been demonstrated that LATS2 exerts a positive regulatory role in the modulation of autophagy and apoptosis in chicken granulosa cells. Furthermore, we verified the regulatory function of miR-302c-3p in chicken granulosa cells via the LATS2-YAP signaling pathway. Our results collectively demonstrates that miR-302c-3p targets LATS2 to modulate the YAP signaling pathway, impacting autophagy and apoptosis in granulosa cells leading to follicular atresia.

MiR-223 inhibits proliferation and steroid hormone synthesis of ovarian granulosa cell via the AKT signaling pathway by targeting CRIM1 in chicken

Within the poultry industry, hens' reproductive performance is of great economic significance. The development and growth of follicles is a key aspect of hen egg production, and ovarian follicle growth and development are closely associated with granulosa cells (GCs) proliferation and the synthesis of steroid hormones. It has been confirmed by numerous studies that microRNAs (miRNAs) play important roles in the steroid hormone synthesis and proliferation of GCs. In this study, we examined the main miRNAs influencing hens' ability to reproduce, identified the miR-223 that is mainly expressed in atretic follicles based on sequencing, and investigated its role in GCs. Then, we used miR-223 mimic and inhibitor to knockdown or overexpress miR-223 expression. The result showed that miR-223 significantly inhibits both the steroid hormone synthesis and the proliferation of GCs. Subsequently, the results of the dual luciferase reporter experiment and bioinformatics prediction demonstrated that cysteine rich transmembrane BMP regulator 1 (CRIM1) was a downstream target gene of miR-223, and overexpression of miR-223 prevented CRIM1 expression. The function of CRIM1 was further investigated, and we observed a significant reduction in the synthesis of steroid hormones and the proliferation of GCs after transfection with CRIM1 siRNA. The opposite function of miR-223 was observed for CRIM1 in our study. Additionally, we demonstrated the involvement of the miR-223/CRIM1 axis in GCs through modulation of the AKT signaling pathway. Our data demonstrate the pivotal role of the miR-223 in the proliferation and steroid hormone synthesis of chicken GCs, which helps to explain how non-coding RNA (ncRNA) affects chicken reproductive function.

Chicken ovarian follicular atresia: interaction network at organic, cellular, and molecular levels

Most of follicles undergo a degenerative process called follicular atresia. This process directly affects the egg production of laying hens and is regulated by external and internal factors. External factors primarily include nutrition and environmental factors. In follicular atresia, internal factors are predominantly regulated at 3 levels; organic, cellular and molecular levels. At the organic level, the hypothalamic-pituitary-ovary (HPO) axis plays an essential role in controlling follicular development. At the cellular level, gonadotropins and cytokines, as well as estrogens, bind to their receptors and activate different signaling pathways, thereby suppressing follicular atresia. By contrast, oxidative stress induces follicular atresia by increasing ROS levels. At the molecular level, granulosa cell (GC) apoptosis is not the only factor triggering follicular atresia. Autophagy is also known to give rise to atresia. Epigenetics also plays a pivotal role in regulating gene expression in processes that seem to be related to follicular atresia, such as apoptosis, autophagy, proliferation, and steroidogenesis. Among these processes, the miRNA regulation mechanism is well-studied. The current review focuses on factors that regulate follicular atresia at organic, cellular and molecular levels and evaluates the interaction network among these levels. Additionally, this review summarizes atretic follicle characteristics, in vitro modeling methods, and factors preventing follicular atresia in laying hens.

CircRAB11A act as miR-24-5p sponge promotes proliferation and resists apoptosis of chicken granulosa cell via EGFR/ERK1/2 and RAB11A/ PI3K/AKT pathways

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs that have been implicated in mediating granulosa cell (GC) proliferation and apoptosis. CircRAB11A was found to have a significantly higher expression in normal follicles compared to atrophic follicles. In this study, we determined that the knockdown of circRAB11A resulted in the inhibition of proliferation and promotion of apoptosis in GCs of chicken. Moreover, circRAB11A was found to act as a sponge for miR-24-5p, both member RAS oncogene family (RAB11A) and epidermal growth factor receptor (EGFR) were revealed to be targets of miR-24-5p through a dual-luciferase reporter assay. RAB11A or EGFR promoted proliferation and suppressed apoptosis in GCs through the phosphatidylinositol-kinase (PI3K)/AKT or extracellular signal-regulated kinase (ERK)1/2 pathway. These findings suggest that circRAB11A may function as a competing endogenous RNA (ceRNA) by targeting the miR-24-5p/RAB11A and miR-24-5p/EGFR axes and activating the ERK1/2 and PI3K/AKT pathways, offering a potential avenue for exploring the mechanism of follicle development.

Whole transcriptome analysis revealed the regulatory network and related pathways of non-coding RNA regulating ovarian atrophy in broody hens

Poultry broodiness can cause ovarian atresia, which has a detrimental impact on egg production. Non-coding RNAs (ncRNAs) have become one of the most talked-about topics in life sciences because of the increasing evidence of their novel biological roles in regulatory systems. However, the molecular mechanisms of ncRNAs functions and processes in chicken ovarian development remain largely unknown. Whole-transcriptome RNA sequencing of the ovaries of broodiness and laying chickens was thus performed to identify the ncRNA regulatory mechanisms associated with ovarian atresia in chickens. Subsequent analysis revealed that the ovaries of laying chickens and those with broodiness had 40 differentially expressed MicroRNA (miRNAs) (15 up-regulated and 25 down-regulated), 379 differentially expressed Long Noncoding RNA (lncRNAs) (213 up-regulated and 166 down-regulated), and 129 differentially expressed circular RNA (circRNAs) (63 up-regulated and 66 down-regulated). The competing endogenous RNAs (ceRNA) network analysis further revealed the involvement of ECM-receptor interaction, AGE-RAGE signaling pathway, focal adhesion, cytokine-cytokine receptor interaction, inflammatory mediator regulation of TRP channels, renin secretion, gap junction, insulin secretion, serotonergic synapse, and IL-17 signaling pathways in broodiness. Upon further analysis, it became evident that THBS1 and MYLK are significant candidate genes implicated in the regulation of broodiness. The expression of these genes is linked to miR-155-x, miR-211-z, miR-1682-z, gga-miR-155, and gga-miR-1682, as well as to the competitive binding of novel_circ_014674 and MSTRG.3306.4. The findings of this study reveal the existence of a regulatory link between non-coding RNAs and their competing mRNAs, which provide a better comprehension of the ncRNA function and processes in chicken ovarian development.

Circular RNA circRPS19 promotes chicken granulosa cell proliferation and steroid hormone synthesis by interrupting the miR-218-5p/INHBB axis

Ovarian follicle development is an important physiological activity for females and makes great significance in maintaining female health and reproduction performance. The development of ovarian follicle is mainly affected by the granulosa cells (GCs), whose growth is regulated by a variety of factors. Here, we identified a novel circular RNA (circRNA) derived from the Ribosomal protein S19 (RPS19) gene, named circRPS19, which is differentially expressed during chicken ovarian follicle development. Further explorations identified that circRPS19 promotes GCs proliferation and steroid hormone synthesis. Furthermore, circRPS19 was found to target and regulate miR-218-5p through a competitive manner with endogenous RNA (ceRNA). Functionals investigation revealed that miR-218-5p attenuates GCs proliferation and steroidogenesis, which is opposite to that of circRPS19. In addition, we also confirmed that circRPS19 upregulates the expression of Inhibin beta B subunit (INHBB) by binding with miR-218-5p to facilitate GCs proliferation and steroidogenesis. Overall, this study revealed that circRPS19 regulates GCs development by releasing the repression of miR-218-5p on INHBB, which suggests a novel mechanism in respect to circRNA and miRNA regulation in ovarian follicle development.

High expression circRALGPS2 in atretic follicle induces chicken granulosa cell apoptosis and autophagy via encoding a new protein

BACKGROUND

The reproductive performance of chickens mainly depends on the development of follicles. Abnormal follicle development can lead to decreased reproductive performance and even ovarian disease among chickens. Chicken is the only non-human animal with a high incidence of spontaneous ovarian cancer. In recent years, the involvement of circRNAs in follicle development and atresia regulation has been confirmed.

RESULTS

In the present study, we used healthy and atretic chicken follicles for circRNA RNC-seq. The results showed differential expression of circRALGPS2. It was then confirmed that circRALGPS2 can translate into a protein, named circRALGPS2-212aa, which has IRES activity. Next, we found that circRALGPS2-212aa promotes apoptosis and autophagy in chicken granulosa cells by forming a complex with PARP1 and HMGB1.

CONCLUSIONS

Our results revealed that circRALGPS2 can regulate chicken granulosa cell apoptosis and autophagy through the circRALGPS2-212aa/PARP1/HMGB1 axis.

miRNA profiling of chicken follicles during follicular development

MicroRNAs (miRNAs) play a crucial role as transcription regulators in various aspects of follicular development, including steroidogenesis, ovulation, apoptosis, and gene regulation in poultry. However, there is a paucity of studies examining the specific impact of miRNAs on ovarian granulosa cells (GCs) across multiple grades in laying hens. Consequently, this study aims to investigate the roles of miRNAs in chicken GCs. By constructing miRNA expression profiles of GCs at 10 different time points, encompassing 4 pre-hierarchical, 5 preovulatory, and 1 postovulatory follicles stage, we identified highly expressed miRNAs involved in GC differentiation (miR-148a-3p, miR-143-3p), apoptosis (let7 family, miR-363-3p, miR-30c-5p, etc.), and autophagy (miR-128-3p, miR-21-5p). Furthermore, we discovered 48 developmentally dynamic miRNAs (DDMs) that target 295 dynamic differentially expressed genes (DDGs) associated with follicular development and selection (such as oocyte meiosis, progesterone-mediated oocyte maturation, Wnt signaling pathway, TGF-β signaling pathway) as well as follicular regression (including autophagy and cellular senescence). These findings contribute to a more comprehensive understanding of the intricate mechanisms underlying follicle recruitment, selection, and degeneration, aiming to enhance poultry's reproductive capacity.

Enhanced expression of miR-204 attenuates LPS stimulated inflammatory injury through inhibiting the Wnt/β-catenin pathway via targeting CCND2

One of the most common bacterial diseases of the reproductive system in dairy cows is endometritis, which will cause huge economic loss. Here, we investigate the mechanisms of miR-204 on LPS-stimulated endometritis in vitro and in vivo. Experiments displayed that the expression of miR-204 was lower in bovine uterine tissue samples or bovine endometrial epithelial cell line (BEND) that stimulated by LPS. Compared with the negative group, miR-204 treatment significantly suppressed the production of proinflammatory factors and the Wnt/β-catenin pathway activation. Additionally, the result of the dual luciferase assay showed that miR-204 targeted cyclin D2. More importantly, up-regulation of miR-204 alleviated LPS induced uterine injury was confirmed in vivo studies. Molecular experiments indicated that the expression level of tight junctional proteins Claudin3 and cadherin1 were both enchanced by miR-204 treatment. Accordingly, miR-204 may serve as a new measure to prevent and treat endometritis caused by LPS.

MiR-134-3p targets HMOX1 to inhibit ferroptosis in granulosa cells of sheep follicles

BACKGROUND

The intricate interplay of gene expression within ovarian granulosa cells (GCs) is not fully understood. This study aimed to investigate the miRNA regulatory mechanisms of ferroptosis during the process of follicle development in lamb GCs.

METHODS

Employing transcriptome sequencing, we compared differentially expressed mRNAs (DE-mRNAs) and miRNAs (DE-miRNAs) in GCs from lambs treated with follicle-stimulating hormone (FL) to untreated controls (CL). We further screened differentially expressed ferroptosis-related genes and identified potential miRNA regulatory factors. The expression patterns of HMOX1 and miRNAs in GCs were validated using qRT‒PCR and Western blotting. Additionally, we investigated the regulatory effect of oar-miR-134-3p on HMOX1 and its function in ferroptosis through cell transfection and erastin treatment.

RESULTS

We identified a total of 4,184 DE-mRNAs and 304 DE-miRNAs. The DE-mRNAs were mainly enriched in ferroptosis, insulin resistance, and the cell cycle. Specifically, we focused on the differential expression of ferroptosis-related genes. Notably, the ferroptosis-related genes HMOX1 and SLC3A2, modulated by DE-miRNAs, were markedly suppressed in FLs. Experimental validation revealed that HMOX1 was significantly downregulated in FL and large follicles, while oar-miR-134-3p was significantly upregulated compared to that in the CLs. HMOX1 expression was regulated by the targeting effect of oar-miR-134-3p. Functional assays further revealed that modulation of oar-miR-134-3p influenced HMOX1 expression and altered cellular responses to ferroptosis induction by erastin.

CONCLUSION

This study suggested that oar-miR-134-3p and HMOX1 may be one of the pathways regulating ferroptosis in GCs. This finding provides new clues to understanding the development and regulatory process of follicles.

Transcriptome profiling reveals SLC5A5 regulates chicken ovarian follicle granulosa cell proliferation, apoptosis, and steroid hormone synthesis

The egg-laying performance of hens holds significant economic importance within the poultry industry. Broody inheritance of the parent stock of chickens can result in poor options for the improvement of egg production, and is a phenomenon influenced by multiple genetic factors. However, few studies have been conducted to delineate the molecular mechanism of ovarian regression in brooding chickens. Here, we explored the pivotal genes responsible for the regulation of ovarian follicles in laying hens, using RNA-sequencing analysis on the small ovarian follicles from broody and laying chickens. Sequencing data analysis revealed the differential expression of 200 genes, with a predominant enrichment in biological processes related to cell activation and metabolism. Among these genes, we focused on solute carrier family 5 member 5 (SLC5A5), which exhibited markedly higher RNA expression levels in follicles from laying compared with broody chickens. Subsequent cellular function studies with knockdown of SLC5A5 in chicken ovarian follicle granulosa cells (GCs) led to the down-regulation of genes associated with cell proliferation and steroid hormone synthesis, and concurrent promotion of gene expression linked to apoptosis. These findings indicated that SLC5A5 deficiency led to the inhibition of proliferation, steroid hormone synthesis and secretion, and promotion of apoptosis in chicken GCs. Our study demonstrated a pivotal role for SLC5A5 in the development and function of chicken GCs, shedding light on its potential significance in the broader context of chicken ovarian follicle development, and providing a prospective target to improve the egg-laying performance of chickens via molecular marker-assisted breeding technology.

High expression of miR-22-3p in chicken hierarchical follicles promotes granulosa cell proliferation, steroidogenesis, and lipid metabolism via PTEN/PI3K/Akt/mTOR signaling pathway

MicroRNAs (miRNAs) are a class of RNA macromolecules that play regulatory roles in follicle development by inhibiting protein translation through binding to the 3'UTR of its target genes. Granulosa cell (GC) proliferation, steroidogenesis, and lipid metabolism have indispensable effect during folliculogenesis. In this study, we found that miR-22-3p was highly expressed in the hierarchical follicles of the chickens, which indicated that it may be involved in follicle development. The results obtained suggested that miR-22-3p promoted proliferation, hormone secretion (progesterone and estrogen), and the content of lipid droplets (LDs) in the chicken primary GC. The results from the bioinformatics analysis, luciferase reporter assay, qRT-PCR, and Western blotting, confirmed that PTEN was directly targeted to miR-22-3p. Subsequently, it was revealed that PTEN inhibited proliferation, hormone secretion, and the content of LDs in GC. Therefore, this study showed that miR-22-3p could activate PI3K/Akt/mTOR pathway via targeting PTEN. Taken together, the findings from this study indicated that miR-22-3p was highly expressed in the hierarchical follicles of chickens, which promotes GC proliferation, steroidogenesis, and lipid metabolism by repressing PTEN to activate PI3K/AKT/mTOR pathway.

The constructive and destructive impact of autophagy on both genders' reproducibility, a comprehensive review

Reproduction is characterized by a series of massive renovations at molecular, cellular, and tissue levels. Recent studies have strongly tended to reveal the involvement of basic molecular pathways such as autophagy, a highly conserved eukaryotic cellular recycling, during reproductive processes. This review comprehensively describes the current knowledge, updated to September 2022, of autophagy contribution during reproductive processes in males including spermatogenesis, sperm motility and viability, and male sex hormones and females including germ cells and oocytes viability, ovulation, implantation, fertilization, and female sex hormones. Furthermore, the consequences of disruption in autophagic flux on the reproductive disorders including oligospermia, azoospermia, asthenozoospermia, teratozoospermia, globozoospermia, premature ovarian insufficiency, polycystic ovarian syndrome, endometriosis, and other disorders related to infertility are discussed as well.Abbreviations: AKT/protein kinase B: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ATG: autophagy related; E2: estrogen; EDs: endocrine disruptors; ER: endoplasmic reticulum; FSH: follicle stimulating hormone; FOX: forkhead box; GCs: granulosa cells; HIF: hypoxia inducible factor; IVF: in vitro fertilization; IVM: in vitro maturation; LCs: Leydig cells; LDs: lipid droplets; LH: luteinizing hormone; LRWD1: leucine rich repeats and WD repeat domain containing 1; MAP1LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MTOR: mechanistic target of rapamycin kinase; NFKB/NF-kB: nuclear factor kappa B; P4: progesterone; PCOS: polycystic ovarian syndrome; PDLIM1: PDZ and LIM domain 1; PI3K: phosphoinositide 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns3K: class III phosphatidylinositol 3-kinase; POI: premature ovarian insufficiency; ROS: reactive oxygen species; SCs: Sertoli cells; SQSTM1/p62: sequestosome 1; TSGA10: testis specific 10; TST: testosterone; VCP: vasolin containing protein.

Whole transcriptome analysis reveals the key genes and noncoding RNAs related to follicular atresia in broilers

Broodiness, a maternal behavior, is accompanied by the atresia of follicles and the serious degradation of poultry reproductive performance. The comparison of follicles between brooding and laying hens is usually an ideal model for exploring the regulation mechanism of follicle atresia. In this study, we selected three brooding hens and three laying hens to collect their follicles for whole transcriptome sequencing. The results demonstrated different expression patterns between the follicles of brooding hens and laying hens. In the top 10 differentially expressed genes with the highest expression, MMP10 was relatively low expressed in the follicles of brooding hens, but other nine genes were relatively highly expressed, including LRR1, RACK1, SPECC1L, ABHD2, COL6A3, RPS17, ATRN, BIRC6, PGAM1 and SPECC1L. While miR-21-3p, miR-146a-5p, miR-142-5p and miR-1b-3p were highly expressed in the follicles of brooding hen, miR-106-5p, miR-451, miR-183, miR-7, miR-2188-5p and miR-182-5p were lowly expressed in brooding hen. In addition, we identified 124 lncRNAs specifically expressed in the follicles of brooding hens and 147 lncRNAs specifically expressed in the follicles of laying hens. Our results may provide a theoretical basis for further exploration of the molecular mechanism of broodiness in broilers.

Exploring the role of miRNAs in early chicken embryonic development and their significance

In the early stages of embryonic development, a precise and strictly controlled hierarchy of gene expression is essential to ensure proper development of all cell types and organs. To better understand this gene control process, we constructed a small RNA library from 1- to 5-day-old chick embryos, and identified 2,459 miRNAs including 827 existing, 695 known, and 937 novel miRNAs with bioinformatic analysis. There was absolute high expression of a number of miRNAs in each stage, including gga-miR-363-3p (Em1d), gga-miR-26a-5p (Em2d and Em3d), gga-miR-10a-5p (Em4d), and gga-miR-199-5p (Em5d). We evaluated enriched miRNA profiles, identifying VEGF, Insulin, ErbB, MAPK, Hedgehog, TLR and Hippo signaling pathways as primary regulatory mechanisms enabling complex morphogenetic transformations within tight temporal constraints. Pathway analysis revealed miRNAs as pivotal nodes of interaction, coordinating cascades of gene expression critical for cell fate determination, proliferation, migration, and differentiation across germ layers and developing organ systems. Weighted Gene Co-Expression Network Analysis (WGCNA) generated hub miRNAs whose modular connections spanned regulatory networks, including: gga-miR-181a-3p (blue module), coordinating immunegenesis and myogenesis; gga-miR-126-3p (brown module), regulating vasculogenesis and angiogenesis; gga-miR-302c-5p (turquoise module), enabling pluripotency and self-renew; and gga-miR-429-3p (yellow module), modulating neurogenesis and osteogenesis. The findings of this study extend the knowledge of miRNA expression in early embryonic development of chickens, providing insights into the intricate gene control process that helps ensure proper development.

Deposition and bioconversion law of β-carotene in laying hens after long-term supplementation under adequate vitamin A status in the diet

β-Carotene, because it is the precursor of vitamin A and has versatile biological roles, has been applied as a feed additive in the poultry industry for a long time. In this study, we investigated the deposition and bioconversion of β-carotene in laying hens. A total of 600 Hy-line brown laying hens at 40 wk of age were randomly divided into 5 dietary treatments, each group's dietary supplemental levels of β-carotene were 0, 15, 30, 60, 120 mg/kg feed, and the vitamin A levels were all 8,000 IU/kg. After 14-wk trial, samples were collected, then carotenoids and different forms of vitamin A were detected using the novel method developed by our laboratory. We found that dietary β-carotene treatment had no significant effects on laying hens' production performance and egg quality (P > 0.05), except the yolk color. The deposition of β-carotene in the body gradually increased (P < 0.01) with the supplemental dose, whereas the contents of lutein and zeaxanthin decreased (P < 0.05). When the β-carotene supplemental level was above 30 mg/kg in the diet, the different forms of vitamin A in in serum, liver, ovary, and yolks were increased compared to the control group (P < 0.05). However, these indicators decreased when the additional dose was 120 mg/kg. Moreover, the mRNA levels of the genes involved in β-carotene absorption, bioconversion, and negative feedback regulation in duodenal mucosa and liver were upregulated after long-term feeding (P < 0.05). Histological staining of the ovaries indicated that the deposition of β-carotene led to a lower rate of follicle atresia (P < 0.05), and this positive effects may be related to the antioxidant function of β-carotene, which caused a reduction of oxidation products in the ovary (P < 0.05). Altogether, β-carotene could accumulate in laying hens intactly and exert its biological functions in tissue. Meanwhile, a part of β-carotene could also be converted into vitamin A but this bioconversion has an upper limit and negative feedback regulation.

Transcriptome-wide m6A methylation profiling of Wuhua yellow-feathered chicken ovary revealed regulatory pathways underlying sexual maturation and low egg-laying performance

RNA N6-melthyladenosine (m6A) can play an important role in regulation of various biological processes. Chicken ovary development is closely related to egg laying performance, which is a process primarily controlled by complex gene regulations. In this study, transcriptome-wide m6A methylation of the Wuhua yellow-feathered chicken ovaries before and after sexual maturation was profiled to identify the potential molecular mechanisms underlying chicken ovary development. The results indicated that m6A levels of mRNAs were altered dramatically during sexual maturity. A total of 1,476 differential m6A peaks were found between these two stages with 662 significantly upregulated methylation peaks and 814 downregulated methylation peaks after sexual maturation. A positive correlation was observed between the m6A peaks and gene expression levels, indicating that m6A may play an important role in regulation of chicken ovary development. Functional enrichment analysis indicated that apoptosis related pathways could be the key molecular regulatory pathway underlying the poor reproductive performance of Wuhua yellow-feathered chicken. Overall, the various pathways and corresponding candidate genes identified here could be useful to facilitate molecular design breeding for improving egg production performance in Chinese local chicken breed, and it might also contribute to the genetic resource protection of valuable avian species.

Lipid Deposition and Progesterone Synthesis Are Increased by miR-181b-5p through RAP1B/ERK1/2 Pathway in Chicken Granulosa Cells

Steroid hormones secreted by granulosa cells are essential for maintaining normal development of chicken follicles. Our previous sequencing data indicated that miR-181b-5p and RAS-related protein 1B (RAP1B) appeared to function in chicken granulosa cells, which was further explored in this study. The results suggested that miR-181b-5p facilitated the aggregation of lipid droplets and the synthesis of progesterone. In contrast, RAP1B astricted lipid deposition and progesterone secretion. Cotransfection of the RAP1B overexpression vector with miR-181b-5p mimic eliminated the promoting effect of miR-181b-5p. Dual-luciferase reporter assay confirmed that miR-181b-5p bound directly to the 3' untranslated region (3' UTR) of RAP1B. We also found that miR-181b-5p and RAP1B reduced and enhanced the phosphorylation levels of extracellular signal-regulated kinases 1 and 2 (ERK1/2), respectively. The application of ERK1/2 activators and inhibitors demonstrated that ERK1/2 is a negative regulator of lipid deposition and progesterone synthesis. In conclusion, we revealed that miR-181b-5p accelerated lipid deposition and progesterone synthesis through the RAP1B/ERK1/2 pathway in chicken granulosa cells. miR-181b-5p and RAP1B may serve as new biomarkers in breeding to improve chicken reproductive performance and prevent ovary-related diseases.

Mechanisms of and Potential Medications for Oxidative Stress in Ovarian Granulosa Cells: A Review

Granulosa cells are essential for follicle initiation and development, and their abnormal function or apoptosis is a crucial factor leading to follicular atresia. A state of oxidative stress occurs when the balance between the production of reactive oxygen species and the regulation of the antioxidant system is disturbed. Oxidative stress is one of the most important causes of the abnormal function and apoptosis of granulosa cells. Oxidative stress in granulosa cells causes female reproductive system diseases, such as polycystic ovary syndrome and premature ovarian failure. In recent years, studies have confirmed that the mechanism of oxidative stress in granulosa cells is closely linked to the PI3K-AKT signaling pathway, MAPK signaling pathway, FOXO axis, Nrf2 pathway, NF-κB signaling pathway, and mitophagy. It has been found that drugs such as sulforaphane, Periplaneta americana peptide, and resveratrol can mitigate the functional damage caused by oxidative stress on granulosa cells. This paper reviews some of the mechanisms involved in oxidative stress in granulosa cells and describes the mechanisms underlying the pharmacological treatment of oxidative stress in granulosa cells.

miR-140-3p promotes follicle granulosa cell proliferation and steroid hormone synthesis via targeting AMH in chickens

Granulosa cells (GCs) are the ovary's most critical cells since they undergo cell differentiation and hormone synthesis changes closely associated with follicle development. While micro RNA 140-3p (miRNA-140-3p) has an apparent cell signaling role, particularly in cell proliferation, its biological role in chicken ovarian follicle growth and development remains elusive. This study explored miR-140-3p's effects on chicken GC proliferation and steroid hormone synthesis. MiR-140-3p dramatically increased GC proliferation, prevented apoptosis, increased progesterone synthesis, and enhanced gene expression related to steroid hormone synthesis. In addition, the anti-Müllerian hormone (AMH) gene was identified as a direct miR-140-3p target. MiR-140-3p abundance correlated negatively with AMH mRNA and protein levels in GCs. Our findings show that miR-140-3p influences chicken GC proliferation and steroid hormone synthesis by suppressing AMH expression.

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.

miR-27b-3p inhibits estrogen secretion of goose granulosa cells by targeting CYP1B1 through the AMPK signaling pathway

Although miR-27b-3p has been evidenced to regulate the proliferation, apoptosis, and differentiation of a variety of mammalian cell types, its actions and mechanisms on ovarian cell steroidogenesis remains largely unknown in both mammalian and avian species. In this study, we aimed to determine the expression profiles of miR-27b-3p in granulosa cell layers during goose ovarian follicle development and to reveal its actions on estrogen (E₂) secretion of goose granulosa cells as well as the underlying regulatory mechanisms. It was observed that miR-27b-3p was ubiquitously expressed throughout follicle development but exhibited much higher levels in hierarchical- than in prehierarchical follicles. In cultured granulosa cells from the fourth through second largest preovulatory (F4-F2) follicles of goose, up- and downregulation of miR-27b-3p by using its mimic and inhibitor significantly decreased and increased E₂ secretion, respectively. Meanwhile, the mRNA levels of STAR and CYP19A1 were significantly reduced while those of CYP11A1 and 3βHSD were elevated in the mimic-transfected granulosa cells. By comparison, downregulation of miR-27b-3p enhanced the mRNA levels of STAR but had no significant effects on those of CYP19A1, CYP11A1, and 3βHSD. Results from bioinformatic prediction and luciferase reporter assay demonstrated that CYP1B1 was a downstream target of miR-27b-3p. Although the siRNA-mediated downregulation of CYP1B1 did not significantly change E₂ secretion by goose granulosa cells, it reduced the mRNA levels of STAR and CYP19A1 as well as those of LKB1 and AMPKα, which are involved in the AMPK signaling pathway. Taken together, these data suggest that miR-27b-3p plays an inhibitory role in E₂ secretion by goose F4-F2 granulosa cells, at least in part, by targeting CYP1B1 through the AMPK signaling pathway.

Untargeted Metabolomics Revealed Potential Biomarkers of Small Yellow Follicles of Chickens during Sexual Maturation

Sexual maturation provides economically important traits in poultry production. Research on the initiation mechanism of sexual maturity is of great significance for breeding high-yield laying hens. However, the underlying mechanisms are not fully clear. Here, one hundred and fifty Chahua No. 2 laying hens (the CH2 group, which has precocious puberty) and one hundred and fifty Wu Liang Shan black-bone laying hens (the WLS group, a late-maturing chicken breed) with similar weights and ages were randomly selected. ELISA was used to determine the secretion levels of luteinizing hormone (LH), estradiol (E2), and progesterone (P4) in 150-day-old serum and small yellow follicle (SYF) tissues. A histology examination, immunohistochemistry, and quantitative real-time PCR (qPCR) were used to explore the molecular mechanism of how some genes related to oxidative stress affect sexual maturation. The results showed that the secretion levels of LH, E2, and P4 in the CH2 group serum and SYF were higher than those in the WLS group. The results of the real-time PCR of all genes showed that the expression levels of cytochrome P450 family 11 subfamily A member 1, steroidogenic acute regulatory protein, follicle-stimulating hormone receptor, and cytochrome P450 family 19 subfamily A member 1 in the CH2 group were significantly higher than those in the WLS groups (p < 0.001). Untargeted metabolomics combined with multivariate statistical analysis was used to identify biomarkers of SYF tissues in the CH2 and WLS groups. A trajectory analysis of the principal component analysis (PCA) results showed that the samples within the group were clustered and that the samples were dispersed between the CH2 and the WLS groups, indicating that the results of the measured data were reliable and could be used for further research. Further analysis showed that a total of 319 metabolites in small yellow follicles of the CH2 and WLS groups were identified, among which 54 downregulated differential metabolites were identified. These 54 metabolites were found as potential CH2 biomarkers compared with WLS at 150 days, and the different expressions of L-arginine, L-prolinamide, (R)-4-hydroxymandelate, glutathione, and homovanillic acid were more significant. Twenty metabolic pathways were found when significantly differential metabolites were queried in the KEGG database. According to the impact values of the metabolic pathways, eighteen differential metabolites belonged to the mTOR signaling pathway, glutathione metabolism, ABC transporters, the cell ferroptosis pathway, and D-arginine and D-ornithine metabolism. Interestingly, we identified that the cell ferroptosis pathway played an important role in chicken follicle selection for the first time. The histology and immunohistochemistry of SYF showed that the number of granulosa cells increased in the CH2 groups and the expression levels of glutathione peroxidase 4, tumor protein p53, ribosomal protein S6 kinase, and sterol regulatory element binding protein 1 in the granulosa cell layer were upregulated in the CH2 group at the time of sexual maturation. Furthermore, we also speculated that the antioxidant system may play an indispensable role in regulating sexual maturity in chickens. Overall, our findings suggest differentially expressed metabolites and metabolic pathways between CH2 and WLS chickens, providing new insights into the initiation mechanism of sexual maturation.

Interacting Networks of the Hypothalamic-Pituitary-Ovarian Axis Regulate Layer Hens Performance

Egg production is a vital biological and economic trait for poultry breeding. The 'hypothalamic-pituitary-ovarian (HPO) axis' determines the egg production, which affects the layer hens industry income. At the organism level, the HPO axis is influenced by the factors related to metabolic and nutritional status, environment, and genetics, whereas at the cellular and molecular levels, the HPO axis is influenced by the factors related to endocrine and metabolic regulation, cytokines, key genes, signaling pathways, post-transcriptional processing, and epigenetic modifications. MiRNAs and lncRNAs play a critical role in follicle selection and development, atresia, and ovulation in layer hens; in particular, miRNA is known to affect the development and atresia of follicles by regulating apoptosis and autophagy of granulosa cells. The current review elaborates on the regulation of the HPO axis and its role in the laying performance of hens at the organism, cellular, and molecular levels. In addition, this review provides an overview of the interactive network regulation mechanism of the HPO axis in layer hens, as well as comprehensive knowledge for successfully utilizing their genetic resources.

MiR-34a-5p promotes autophagy and apoptosis of ovarian granulosa cells via the Hippo-YAP signaling pathway by targeting LEF1 in chicken

Follicular atresia is a natural physiological phenomenon in poultry reproduction. It is well known that follicular atresia is caused by both autophagy and apoptosis of granulosa cells. In current experiment, we evaluated the function of miR-34a-5p on autophagy and apoptosis in chicken follicular atresia. First, the follicular atresia model of chicken was successfully constructed by subcutaneous injection of tamoxifen (TMX), and found the expression of miR-34a-5p in the atresia follicles obviously increased. Then, we confirmed that miR-34a-5p accelerates autophagy and apoptosis of chicken granulose cells in vitro, and miR-34a-5p could induce apoptosis by mediating autophagy. Mechanistically, lymphoid enhancer binding factor 1 (LEF1) was deemed as a target gene for miR-34a-5p. On the contrary, LEF1 overexpression attenuated the autophagy and apoptosis of chicken granular cells. In addition, it was confirmed that the miR-34a-5p/LEF1 axis plays a regulatory role in chicken granulosa cells by mediating the Hippo-YAP signaling pathway. Taken together, this study demonstrated that miR-34a-5p contributes to autophagy and apoptosis of chicken follicular granulosa cells by targeting LEF1 to mediate the Hippo-YAP signaling pathway.

miR-10a-5p inhibits chicken granulosa cells proliferation and Progesterone(P4) synthesis by targeting MAPRE1 to suppress CDK2

The proliferation and steroid hormone synthesis of granulosa cells (GCs) are essential for ovarian follicle growth and ovulation, which are necessary to support the normal function of the follicle. Numerous studies suggest that miRNAs play key roles in this process. In this study, we report a novel role for miR-10a-5p that inhibits ovarian GCs proliferation and progesterone (P4) synthesis in chicken. Specifically, we found that miR-10a-5p significantly decreased the P4 secretion by quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot. Moreover, we observed that miR-10a-5p can inhibit the proliferation of chicken GCs through the investigation of cell proliferation gene expression, cell counting kit 8 (CCK-8), cell cycle progression, and 5-ethynyl-2'-deoxyuridine (EdU) assay. Then we screened a target gene MAPRE1 of miR-10a-5p, which can promote P4 synthesis and proliferation of GCs. To explore how miR-10a-5p affects cell cycle by MAPRE1, we investigated the interaction between MAPRE1 and cyclin-dependent kinase 2 (CDK2) by Co-Immunoprecipitation (Co-IP), and then we found that MAPRE1 can form a complex with CDK2. In addition, miR-10a-5p was found to inhibit CDK2 expression by repressing the expression of MAPRE1. Overall, our results indicate that miR-10a-5p regulates the proliferation and P4 synthesis of chicken GCs by targeting MAPRE1 to suppress CDK2.