TGF-β1 controls porcine granulosa cell states: A miRNA-mRNA network view

Follicular fluid exosomes inhibit expression of BTG2 and promote glucose uptake in granulosa cells by delivering miR-21-5p

Glucose metabolism in granulosa cells (GCs) is essential for follicle development and oocyte maturation. Porcine follicular fluid exosomes promote the proliferation of porcine GCs and the synthesis of steroid hormones. However, their role in regulating glucose uptake in GCs is unclear. The objective of this study was to elucidate the effects of porcine follicular fluid exosomes on glucose uptake in porcine GCs and the intrinsic mechanisms involved. First, transcriptome sequencing revealed that glucose metabolism-related pathways were altered in GCs treated with follicular fluid exosomes. Next, in vitro culture experiments showed that glucose uptake was increased and the IRS1/AKT signaling pathway was activated in GCs after treatment with follicular fluid exosomes. Finally, miRNA sequencing of follicular fluid exosomes revealed that miR-21-5p was the most abundant miRNA. Subsequent investigations indicated that miR-21-5p promoted glucose uptake in GCs by targeting BTG2, which activated the IRS1/AKT signaling pathway. In conclusion, the findings of this study indicate that porcine follicular fluid exosomes promote glucose uptake in porcine GCs by delivering miR-21-5p, which inhibits the expression of BTG2, activating the IRS1/AKT signaling pathway.

Differential age-related transcriptomic analysis of ovarian granulosa cells in Kazakh horses

Introduction

The Kazakh horse, renowned for its excellence as a breed, exhibits distinctive reproductive traits characterized by early maturity and seasonal estrus. While normal reproductive function is crucial for ensuring the breeding and expansion of the Kazakh horse population, a noteworthy decline in reproductive capabilities is observed after reaching 14 years of age.

Methods

In this study, ovarian granulosa cells (GCs) were meticulously collected from Kazakh horses aged 1, 2, 7, and above 15 years old (excluding 15 years old) for whole transcriptome sequencing.

Results

The analysis identified and selected differentially expressed mRNAs, lncRNAs, miRNAs, and circRNAs for each age group, followed by a thorough examination through GO enrichment analysis. The study uncovered significant variations in the expression profiles of mRNAs, lncRNAs, miRNAs, and circRNAs within GCs at different stages of maturity. Notably, eca-miR-486-3p and miR-486-y exhibited the highest degree of connectivity. Subsequent GO, KEGG, PPI, and ceRNA network analyses elucidated that the differentially expressed target genes actively participate in signaling pathways associated with cell proliferation, apoptosis, and hormonal regulation. These pathways include but are not limited to the MAPK signaling pathway, Hippo signaling pathway, Wnt signaling pathway, Calcium signaling pathway, Aldosterone synthesis and secretion, Cellular senescence, and NF-kappa B signaling pathway-essentially encompassing signal transduction pathways crucial to reproductive processes.

Discussion

This research significantly contributes to unraveling the molecular mechanisms governing follicular development in Kazakh horses. It establishes and preliminarily validates a differential regulatory network involving lncRNA-miRNA-mRNA, intricately associated with processes such as cell proliferation, differentiation, and apoptosis and integral to the developmental intricacies of stromal follicles. The findings of this study provide a solid theoretical foundation for delving deeper into the realm of reproductive aging in Kazakh mares, presenting itself as a pivotal regulatory pathway in the context of horse ovarian development.

Transforming growth factor-β1 mediates the SMAD4/BMF pathway to regulate ovarian granulosa cell apoptosis in small tail Han sheep

Transforming growth factor (TGF)-β1 is an important multifunctional cytokine in the TGF-β signaling pathway, which is involved in the molecular regulation of multiple activities, including follicle development and ovulation in female reproductive physiology. However, the biological function of TGF-β1 in follicular development and in regulating the proliferation or apoptosis of granulosa cells in small tail Han sheep remain unclear. In this study, we analyzed the expression levels of TGF-β1 in the ovary at the follicular stage in small tail Han sheep. We further examined the effects of TGF-β1 on the viability, proliferation, and apoptosis of granulosa cells. Differential expression of TGF-β1 at the mRNA and protein levels was detected in the ovaries between the beginning of estrus and at preovulation. Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine (EdU) labeling, and flow cytometry assays showed that adding 5 and 10 ng/mL TGF-β1 could improve the viability and growth rate, reduce the apoptosis rate, and reduce the expression level of the pro-apoptotic factor Bcl-2-modifying factor (BMF) in granulosa cells. Treatment of 10 ng/mL TGF-β1 at all time points (except 72 h) significantly increased the positive rate of EdU labeling compared to that of the control group. RNA interference of SMAD4 reversed the decreased apoptosis rate caused by stimulation with 10 ng/mL TGF-β1, accompanied by a corresponding increase in the BMF expression level. Collectively, these results indicate that TGF-β1 plays a role in the ovarian follicular-phase activity of small tail Han sheep by inhibiting the apoptosis of sheep granulosa cells through the SMAD4/BMF pathway to promote proliferation and vitality. This study provides new insight into the molecular mechanism underlying TGF-β1 function regulation in granulosa cells, suggests a new target for the regulation of follicle development, and expands the new field of animal reproduction regulation technology.

Growth factors and female reproduction in vertebrates

Female reproductive efficiency is influenced by the outcomes of various processes, including folliculogenesis, apoptosis, response to gonadotropin signaling, oocyte maturation, and ovulation. The role of hormones in regulating these processes and other reproductive activities has been well established. It is becoming increasingly evident that in addition to well-characterized hormones, growth factors play vital roles in regulating some of these reproductive activities. Growth factors and their receptors are widely distributed in vertebrate ovaries at different stages of ovarian development, indicating their involvement in intraovarian reproductive functions. In the ovary, cell surface receptors allow growth factors to regulate intraovarian reproductive activities. Understanding these actions in the reproductive axis would provide a tool to target growth factors and/or their receptors to yield desirable reproductive outcomes. These include enrichment of in vitro maturation and fertilization culture media, and management of infertility. This review discusses some widely characterized growth factors belonging to the TGF, EGF, IGF, FGF, and BDNF family of peptides and their role in female reproduction in vertebrates, with a focus on mammals.

Estrogen Receptor Gene 1 (ESR1) Mediates Lipid Metabolism in Goose Hierarchical Granulosa Cells Rather than in Pre-Hierarchical Granulosa Cells

(1) Background: The role of estrogen receptor gene 1 (ESR1) in female reproduction and lipid metabolism has been extensively investigated. However, its contribution to lipid metabolism during the development of poultry follicles remains unclear. (2) Methods: This study aimed to explore the function of ESR1 via overexpressing (ESR1^ov) and interfering (ESR1^si) with its expression in pre-hierarchical granulosa cells (phGCs) and hierarchical granulosa cells (poGCs). (3) Results: We successfully cloned and obtained an 1866 bp segment of the full-length CDS region of the Sichuan white goose ESR1 gene. In phGCs of the ESR1^ov and ESR1^si groups, there were no significant changes compared to the control group. However, in poGCs, the ESR1^ov group exhibited decreased lipid deposition, triglycerides, and cholesterol compared to the control group, while the ESR1^si group showed increased lipid deposition, triglycerides, and cholesterol. The expression of APOB and PPARα was significantly reduced in the ESR1^ov group compared to the ESR1^ov-NC group. Moreover, significant changes in the expression of ACCα, DGAT1, SCD, CPT1, and ATGL were observed between the ESR1^si and ESR1^si-NC group. (4) Conclusions: These findings shed light on the function and molecular mechanism of ESR1 in lipid metabolism in goose poGCs, providing a better understanding of the physiological process of goose follicular development.

MiR-202-5p Regulates Geese Follicular Selection by Targeting BTBD10 to Regulate Granulosa Cell Proliferation and Apoptosis

The regulation of granulosa cells (GCs) proliferation and apoptosis is the key step in follicular selection which determines the egg production performance of poultry. miR-202-5p has been reported to be involved in regulating the proliferation and apoptosis of mammalian ovarian GCs. However, its role in regulating the proliferation and apoptosis of goose GCs is still unknown. In the present study, the GCs of pre-hierarchical follicles (phGCs, 8-10 mm) and those of hierarchical follicles (hGCs, F2-F4) were used to investigate the role of miR-202-5p in cell proliferation and apoptosis during follicle selection. In phGCs and hGCs cultured in vitro, miR-202-5p was found to negatively regulate cell proliferation and positively regulate cell apoptosis. The results of RNA-seq showed that BTB Domain Containing 10 (BTBD10) is predicted to be a key target gene for miR-202-5p to regulate the proliferation and apoptosis of GCs. Furthermore, it is confirmed that miR-202-5p can inhibit BTBD10 expression by targeting its 3'UTR region, and BTBD10 was revealed to promote the proliferation and inhibit the apoptosis of phGCs and hGCs. Additionally, co-transfection with BTBD10 effectively prevented miR-202-5p mimic-induced cell apoptosis and the inhibition of cell proliferation. Meanwhile, miR-202-5p also remarkably inhibited the expression of Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Beta (PIK3CB) and AKT Serine/Threonine Kinase 1 (AKT1), while it was significantly restored by BTBD10. Overall, miR-202-5p suppresses the proliferation and promotes the apoptosis of GCs through the downregulation of PIK3CB/AKT1 signaling by targeting BTBD10 during follicular selection. Our study provides a theoretical reference for understanding the molecular mechanism of goose follicular selection, as well as a candidate gene for molecular marker-assisted breeding to improve the geese' egg production performance.

SDNOR, a Novel Antioxidative lncRNA, Is Essential for Maintaining the Normal State and Function of Porcine Follicular Granulosa Cells

Increasing evidence shows that lncRNAs, an important kind of endogenous regulator, are involved in the regulation of follicular development and female fertility, but the mechanism remain largely unknown. In this study, we found that SDNOR, a recently identified antiapoptotic lncRNA, is a potential multifunctional regulator in porcine follicular granulosa cells (GCs) through RNA-seq and multi-dimension analyses. SDNOR-mediated regulatory networks were established and identified that SOX9, a transcription factor inhibited by SDNOR, mediates SDNOR's regulation of the transcription of downstream targets. Functional analyses showed that loss of SDNOR significantly impairs GC morphology, inhibits cell proliferation and viability, reduces E2/P4 index, and suppresses the expression of crucial markers, including PCNA, Ki67, CDK2, CYP11A1, CYP19A1, and StAR. Additionally, after the detection of ROS, SOD, GSH-Px, and MDA, we found that SDNOR elevates the resistance of GCs to oxidative stress (OS) and also inhibits OS-induced apoptosis. Notably, GCs with high SDNOR levels are insensitive to oxidative stress, leading to lower apoptosis rates and higher environmental adaptability. In summary, our findings reveal the regulation of porcine GCs in response to oxidative stress from the perspective of lncRNA and demonstrate that SDNOR is an essential antioxidative lncRNA for maintaining the normal state and function of GCs.

TGF-β1 regulates the lncRNA transcriptome of ovarian granulosa cells in a transcription activity-dependent manner

OBJECTIVES

Transforming growth factor β1 (TGF-β1), an essential cytokine belongs to TGF-β superfamily, is crucial for female fertility. Increasing evidence show that long noncoding RNAs (lncRNAs) influence the state of granulosa cells (GCs). This study aimed to detect the effects of TGF-β1 on the lncRNA transcriptome, and investigate whether lncRNAs mediate the functions of TGF-β1 in GCs.

MATERIAL AND METHODS

RNA-seq and bioinformatics analyses were performed to identify and characterize the differentially expressed lncRNAs (DElncRNAs). The regulatory mechanism of TGF-β1 to lncRNA transcriptome was analyzed by chromatin immunoprecipitation. The effects of lncRNAs on the antiapoptotic and proproliferative functions of TGF-β1 were examined by morphological analysis, fluorescence-activated cell sorting, Cell Counting Kit-8, and Western blot.

RESULTS

A total of 72 DElncRNAs highly sensitive to TGF-β1 were identified with the criteria of |log₂ (fold chage)| ≥ 3 and false discovery rate < 0.05. Functional assessment showed that DElncRNAs were enriched in TGF-β, nuclear factor kappa B, p53, and Hippo pathways which are crucial for the normal state and function of GCs. Importantly, SMAD4 is essential for the regulation of TGF-β1 to lncRNA transcriptome. In vitro studies confirmed that TGF-β1 induced TEX14-IT1 transcription in a SMAD4-dependent manner, and TEX14-IT1 mediated the antiapoptotic and proproliferative effects of TGF-β1 in GCs.

CONCLUSIONS

Our findings demonstrate that TGF-β1 alters lncRNA transcriptome in a SMAD4-dependent manner, and highlight that lncRNAs mediate the functions of TGF-β1 in GCs, which contribute to a better understanding of the epigenetic regulation of female fertility.

The TGF-β/SMAD Signaling Pathway Prevents Follicular Atresia by Upregulating MORC2

In mammals, female fertility is determined by the outcome of follicular development (ovulation or atresia). The TGF-β/SMAD signaling pathway is an important regulator of this outcome. However, the molecular mechanism by which the TGF-β/SMAD signaling pathway regulates porcine follicular atresia has not been fully elucidated. Microrchidia family CW-type zinc finger 2 (MORC2) is anovel epigenetic regulatory protein widely expressed in plants, nematodes, and mammals. Our previous studies showed that MORC2 is a potential downstream target gene of the TGF-β/SMAD signaling pathway. However, the role of MORC2 in porcine follicular atresia is unknown. To investigate this, qRT-PCR, western blotting, and TdT-mediated dUTP nick-end labeling were performed. Additionally, the luciferase activity assay was conductedto confirm that the TGF-β/SMAD signaling pathway regulates MORC2. Our results demonstrate that MORC2 is animportant anti-apoptotic molecule that prevents porcine follicular atresia via a pathway involving mitochondrial apoptosis, not DNA repair. Notably, this studyrevealsthat the TGF-β/SMAD signaling pathway inhibits porcine granulosa cell apoptosis by up-regulating MORC2. The transcription factor SMAD4 regulated the expression of MORC2 by binding to its promoter. Our results will help to reveal the mechanism underlying porcine follicular atresia and improve the reproductive efficiency of sows.

Integrative analysis of transcriptome complexity in pig granulosa cells by long-read isoform sequencing

Background

In intensive and large-scale farms, abnormal estradiol levels in sows can cause reproductive disorders. The high incidence rate of reproductive disturbance will induce the elimination of productive sows in large quantities, and the poor management will bring great losses to the pig farms. The change in estradiol level has an important effect on follicular development and estrus of sows. To solve this practical problem and improve the productive capacity of sows, it is significant to further clarify the regulatory mechanism of estradiol synthesis in porcine granulosa cells (GCs). The most important function of granulosa cells is to synthesize estradiol. Thus, the studies about the complex transcriptome in porcine GCs are significant. As for precursor-messenger RNAs (pre-mRNAs), their post-transcriptional modification, such as alternative polyadenylation (APA) and alternative splicing (AS), together with long non-coding RNAs (lncRNAs), may regulate the functions of granulosa cells. However, the above modification events and their function are unclear within pig granulosa cells.

Methods

Combined PacBio long-read isoform sequencing (Iso-Seq) was conducted in this work for generating porcine granulosa cells' transcriptomic data. We discovered new transcripts and possible gene loci via comparison against reference genome. Later, combined Iso-Seq data were adopted to uncover those post-transcriptional modifications such as APA or AS, together with lncRNA within porcine granulosa cells. For confirming that the Iso-Seq data were reliable, we chose four AS genes and analyzed them through RT-PCR.

Results

The present article illustrated that pig GCs had a complex transcriptome, which gave rise to 8,793 APA, 3,465 AS events, 703 candidate new gene loci, as well as 92 lncRNAs. The results of this study revealed the complex transcriptome in pig GCs. It provided a basis for the interpretation of the molecular mechanism in GCs.

Discovery of Differentially Expressed MicroRNAs in Porcine Ovaries With Smaller and Larger Litter Size

The number of live births in a litter is an important reproductive trait, and is one of the main indicators which reflect the production level and economic benefit of a pig farm. The ovary is an important reproductive organ of the sow, and it undergoes a series of biological processes during each estrous cycle. A complex transcriptional network containing coding and non-coding RNAs in the ovary closely regulates the reproductive capability of sows. However, the molecular regulation mechanisms affecting sow litter size are still unclear. We investigated the expression profiles of microRNAs (miRNAs) in porcine ovaries from sows with smaller than average litter sizes (SLS) and those with larger litter sizes (LLS). In total, 411 miRNAs were identified, and of these 17 were significantly down-regulated and 16 miRNAs were up-regulated when comparing sows with LLS and SLS, respectively. We further characterized the role of miR-183 which was one of the most up-regulated miRNAs. CCK-8, EdU incorporation and western blotting assays demonstrated that miR-183 promoted the proliferation of granulosa cells (GCs) in pig ovaries. Moreover, miR-183 inhibited the synthesis of estradiol in GCs and promoted the synthesis of progesterone. These results will help in gaining understanding of the role of miRNAs in regulating porcine litter size.

SMAD4-induced knockdown of the antisense long noncoding RNA BRE-AS contributes to granulosa cell apoptosis

Antisense long noncoding RNAs (AS-lncRNAs), a sub-class of lncRNAs, are transcribed in the opposite direction from their overlapping protein-coding genes and are implicated in various physiological and pathological processes. However, their role in female reproduction remains largely unknown. Here, we report that BRE-AS, an AS-lncRNA transcript from intron 10 of the protein-coding gene BRE, is involved in granulosa cell (GC) apoptosis. Based on our previous RNA sequencing data, we identified 28 AS-lncRNAs as important in the initiation of porcine follicular atresia, with BRE-AS showing the most significant upregulation in early atretic follicles. In this study, gain- and loss-of-function assays demonstrated that BRE-AS induces early apoptosis in GCs. Mechanistically, BRE-AS acts in cis to suppress the expression of BRE, an anti-apoptotic factor, via direct interaction with the pre-mRNA transcript of the latter, inducing increased GC apoptosis. Notably, we also found that BRE-AS was upregulated in SMAD4-silenced GCs. SMAD4 was identified as a transcriptional repressor of BRE-AS because it inhibits BRE-AS expression and BRE-AS-mediated GC apoptosis. In conclusion, we not only identified a novel AS-lncRNA related to the early apoptosis of GCs and initiation of follicular atresia but also described a novel regulatory pathway, SMAD4/BRE-AS/BRE, coordinating GC function and female fertility.

miR-135a Suppresses Granulosa Cell Growth by Targeting Tgfbr1 and Ccnd2 during Folliculogenesis in Mice

The success of female reproduction relies on high quality oocytes, which is determined by well-organized cooperation between granulosa cells (GCs) and oocytes during folliculogenesis. GC growth plays a crucial role in maintaining follicle development. Herein, miR-135a was identified as a differentially expressed microRNA in pre-ovulatory ovarian follicles between Large White and Chinese Taihu sows detected by Solexa deep sequencing. We found that miR-135a could significantly facilitate the accumulation of cells arrested at the G1/S phase boundary and increase apoptosis. Mechanically, miR-135a suppressed transforming growth factor, beta receptor I (Tgfbr1) and cyclin D2 (Ccnd2) expression by targeting their 3′UTR in GCs. Furthermore, subcellular localization analysis and a chromatin immunoprecipitation-quantitative real-time PCR (ChIP-qPCR) assay demonstrated that the TGFBR1-SMAD3 pathway could enhance Ccnd2 promoter activity and thus upregulate Ccnd2 expression. Finally, estrogen receptor 2 (ESR2) functioned as a transcription factor by directly binding to the miR-135a promoter region and decreasing the transcriptional activity of miR-135a. Taken together, our study reveals a pro-survival mechanism of ESR2/miR-135a/Tgfbr1/Ccnd2 axis for GC growth, and also provides a novel target for the improvement of female fertility.

SMAD4 Inhibits Granulosa Cell Apoptosis via the miR-183-96-182 Cluster and FoxO1 Axis

The miR-183-96-182 cluster is a polycistronic miRNA cluster necessary for ovarian functions in mammals. However, its transcriptional regulation in the ovary is largely unclear. In this study, we characterized the promoter region of the porcine miR-183-96-182 cluster, and showed that SMAD4 may function as a transcriptional activator of the miR-183-96-182 cluster in GCs through direct binding to SBE motifs in its promoter. SMAD4 may inhibit GC apoptosis via suppression of FoxO1, an effector of GC apoptosis and a direct target of the miR-183-96-182 cluster, by inducing the miR-183-96-182 cluster, and this process may be regulated by the TGF-β/SMAD signaling pathway. Our findings uncovered the regulatory mechanism of miR-183-96-182 cluster expression in GCs and demonstrated that TGF-β1/SMAD4/miR-183-96-182 cluster/FoxO1 may be a potential pathway for regulating follicular atresia and female reproduction.