Interleukins' expression profile changes in granulosa cells of preovulatory follicles during the postpartum period in dairy cows

Neuregulin 1 Signaling Attenuates Tumor Necrosis Factor α-Induced Female Rat Luteal Cell Death

The corpus luteum (CL) is a transient ovarian endocrine structure that maintains pregnancy in primates during the first trimester and in rodents during the entire pregnancy by producing steroid hormone progesterone (P4). CL lifespan, growth, and differentiation are tightly regulated by survival and cell death signals through luteotrophic and luteolytic factors, including the epidermal growth factor (EGF)-like factor family. Neuregulin 1 (NRG1), a member of the EGF family, mediates its effect through ErbB2/3 receptors. However, the functional role of NRG1 in luteal cells (LCs) is unknown. Thus, this study investigated the role of NRG1 and its molecular mechanism of action in rat LC. Our experimental results suggest a strong positive correlation between steroidogenic acute regulatory protein (StAR) and NRG1 expression in mid-CL and serum P4 and estrogen (E2) production. In contrast, there was a decrease in StAR and NRG1 expression and P4 and E2 production with an increase in tumor necrosis factor α (TNFα) expression in regressing CL. Further in vitro studies in LCs showed that the knockdown of endogenous Nrg1 promoted the expression of proinflammatory and proapoptotic factors and decreased prosurvival factor expression. Subsequently, treatment with exogenous TNFα under these experimental conditions profoundly elevated proinflammatory and proapoptotic factors. Further analysis demonstrated that the phosphorylation status of ErbB2/3, PI3K, Ak strain transforming or protein kinase B (Akt), and ErK1/2 was significantly inhibited under these experimental conditions, whereas the treatment of TNFα further inhibited the phosphorylation of ErbB2/3, PI3K, Akt, and ErK1/2. Collectively, these studies provide new insights into the NRG1-mediated immunomodulatory and prosurvival role in LCs, which may maintain the function of CL.

Sheep litter size heredity basis using genome-wide selective analysis

Sheep are important herbivorous domestic animal globally, and the Chinese indigenous sheep breed has a multitude of economically significant variations due to the diverse geographical and ecological conditions. In particular, certain native breeds exhibit a visible high litter size phenotype due to the selection pressure of natural and artificial for thousands of years, offering an ideal animal model for investigating sheep's fecundity. In this study, selective signal analysis was performed on public whole-genome sequencing data from 60 sheep across eight breeds to identify candidate genes related to litter size. Results revealed that a total of 34,065,017 single-nucleotide polymorphisms (SNPs) were identified from all sheep, and 65 candidate genes (CDGs) were pinpointed from the top 1% of interacted windows and SNPs between the pairwise fixation index (FST, >0.149543) and cross-population extended haplotype homozygosity (XP-EHH, >0.701551). A total of 41 CDGs (e.g. VRTN, EYA2 and MCPH1) were annotated to 576 GO terms, of which seven terms were directly linked to follicular and embryonic development (e.g. TBXT, BMPR1B, and BMP2). In addition, 73 KEGG pathways were enriched by 21 CDGs (e.g. ENTPD5, ABCD4 and RXFP2), mainly related to Hippo (TCF4, BMPR1B and BMP2), TGF-β (BMPR1B and BMP2), PI3K-Akt (ITGB4, IL4R and PPP2R5A) and Jak-STAT signalling pathways (IL20RA and IL4R). Notably, a series of CDGs was under strong selection in sheep with high litter size traits. These findings result could improve the comprehension of the genetic underpinnings of sheep litter size. Furthermore, it provides valuable CDGS for future molecular breeding.

Endometrial DNA methylation signatures during the time of breeding in relation to the pregnancy outcome in postpartum dairy cows fed a control diet or supplemented with rumen-protected methionine

Post calving metabolic stress reduces the fertility of high producing dairy cows possibly by altering the expression of genes in the maternal environment via epigenetic modifications. Therefore, this study was conducted to identify endometrial DNA methylation marks that can be associated with pregnancy outcomes in postpartum cows at the time of breeding. For this, twelve days post-calving, cows were either offered a control diet or supplemented daily with rumen-protected methionine. Cows showing heat 50-64 days postpartum were artificially inseminated. Endometrial cytobrush samples were collected 4-8 h after artificial insemination and classified based on the pregnancy out comes as those derived from cows that resulted in pregnancy or resulted in no pregnancy. The DNAs isolated from endometrial samples were then subject to reduced representative bisulfite sequencing for DNA methylation analysis. Results showed that in the control diet group, 1,958 differentially methylated CpG sites (DMCGs) were identified between cows that resulted in pregnancy and those that resulted in no pregnancy of which 890 DMCGs were located on chr 27: 6217254-6225600 bp. A total of 537 DMCGs were overlapped with 313 annotated genes that were involved in various pathways including signal transduction, signalling by GPCR, aldosterone synthesis and secretion. Likewise, in methionine supplemented group, 3,430 CpG sites were differentially methylated between the two cow groups of which 18.7% were located on Chr27: 6217254-6225600 bp. A total of 1,781 DMCGS were overlapped with 890 genes which involved in developmental and signalling related pathways including WNT-signalling, focal adhesion and ECM receptor interaction. Interestingly, 149 genes involved in signal transduction, axon guidance and non-integrin membrane-ECM interactions were differentially methylated between the two cow groups irrespective of their feeding regime, while 453 genes involved in axon guidance, notch signalling and collagen formation were differentially methylated between cows that received rumen protected methionine and control diet irrespective of their fertility status. Overall, this study indicated that postpartum cows that could potentially become pregnant could be distinguishable based on their endometrial DNA methylation patterns at the time of breeding.

Metabolic and antioxidant status during transition is associated with changes in the granulosa cell transcriptome in the preovulatory follicle in high-producing dairy cows at the time of breeding

In this study, we hypothesized that early postpartum (pp) metabolic and oxidative stress conditions in dairy cows (particularly those with severe negative energy balance, NEB) are associated with long-term changes in granulosa cell (GC) functions in the preovulatory follicle at the time of breeding. Blood samples were collected at wk 2 and wk 8 pp from 47 healthy multiparous cows. Follicular fluid (FF) and GC were collected from the preovulatory follicle after estrous synchronization at wk 8. Several metabolic and antioxidant parameters were measured in blood and FF, and their correlations were studied. Subsequently, 27 representative GC samples were selected for RNA sequencing analysis. The GC gene expression data of LH-responsive genes and the estradiol:progesterone ratio in FF were used to identify pre- and post-LH surge cohorts. We compared the transcriptomic profile of subgroups of cows within the highest and lowest quartiles (Q4 vs. Q1) of each parameter, focusing on the pre-LH surge cohort (n = 16, at least 3 in each subgroup). Differentially expressed genes (DEG: adjusted P-value < 0.05, 5% false discovery rate) were determined using DESeq2 analysis and were functionally annotated. Blood and FF β-carotene and vitamin E concentrations at wk 2, but not at wk 8, were associated with the most pronounced transcriptomic differences in the GC, with up to 341 DEG indicative for lower catabolism, increased oxidoreductase activity and signaling cascades that are known to enhance oocyte developmental competence, increased responsiveness to LH, and a higher steroidogenic activity. In contrast, elevated blood NEFA concentrations at wk 2 (and not at wk 8) were associated with a long-term carryover effect detectable in the GC transcriptome at wk 8 (64 DEG). These genes are related to response to lipids and ketones, oxidative stress, and immune responses, which suggests persistent cellular stress and oxidative damage. This effect was more pronounced in cows with antioxidant deficiencies at wk 8 (up to 148 DEG), with more genes involved in oxidative stress-dependent responses, apoptosis, autophagy and catabolic processes, and mitochondrial damage. Interestingly, within the severe NEB cows (high blood NEFA at wk 2), blood antioxidant concentrations (high vs. low) at wk 8 were associated with up to 194 DEG involved in activation of meiosis and other signaling pathways, indicating a better oocyte supportive capacity. This suggests that the cow antioxidant profile at the time of breeding might alleviate, at least in part, the effect of NEB on GC functions. In conclusion, these results provide further evidence that the metabolic and oxidative stress in dairy cows early postpartum can have long-term effects on GC functions in preovulatory follicles at the time of breeding. The interplay between the effects of antioxidants and NEFA illustrated here might be useful to develop intervention strategies to minimize the effect of severe NEB on fertility.

Neuregulin-1 signaling regulates cytokines and chemokines expression and secretion in granulosa cell

BACKGROUND

Granulosa cells (GCs) are multilayered somatic cells within the follicle that provide physical support and microenvironment for the developing oocyte. In recent years, the role of Neuregulin-1 (NRG1), a member of the EGF-like factor family, has received considerable attention due to its neurodevelopmental and cardiac function. However, the exact physiological role of NRG1 in GC is mainly unknown. In order to confirm that NRG1 plays a regulatory role in rat GC functions, endogenous NRG1-knockdown studies were carried out in GCs using RNA interference methodology.

RESULTS

Knockdown of NRG1 in GCs resulted in the enhanced expression and secretion of the cytokines and chemokines. In addition, the phosphorylation of PI3K/Akt/ERK1/2 was significantly low in GCs under these experimental conditions. Moreover, in vitro experimental studies suggest that tumor necrosis factor-α (TNFα) treatment causes the physical destruction of GCs by activating caspase-3/7 activity. In contrast, exogenous NRG1 co-treatment of GCs delayed the onset of TNFα-induced apoptosis and inhibited the activation of caspase-3/7 activity. Furthermore, current experimental studies suggest that gonadotropins promote differential expression of NRG1 and ErbB3 receptors in GCs of the antral follicle. Interestingly, NRG1 and ErbB3 were intensely co-localized in the mural and cumulus GCs and cumulus-oocyte complex of pre-ovulatory follicles in the estrus stage.

CONCLUSIONS

The present studies suggest that gonadotropins-dependent NRG1-signaling in GCs may require the balance of the cytokines and chemokines expression and secretion, ultimately which may be supporting the follicular maturation and oocyte competence for ovulation and preventing follicular atresia.

MERTK-Mediated LC3-Associated Phagocytosis (LAP) of Apoptotic Substrates in Blood-Separated Tissues: Retina, Testis, Ovarian Follicles

Timely and efficient elimination of apoptotic substrates, continuously produced during one’s lifespan, is a vital need for all tissues of the body. This task is achieved by cells endowed with phagocytic activity. In blood-separated tissues such as the retina, the testis and the ovaries, the resident cells of epithelial origin as retinal pigmented epithelial cells (RPE), testis Sertoli cells and ovarian granulosa cells (GC) provide phagocytic cleaning of apoptotic cells and cell membranes. Disruption of this process leads to functional ablation as blindness in the retina and compromised fertility in males and females. To ensure the efficient elimination of apoptotic substrates, RPE, Sertoli cells and GC combine various mechanisms allowing maintenance of tissue homeostasis and avoiding acute inflammation, tissue disorganization and functional ablation. In tight cooperation with other phagocytosis receptors, MERTK—a member of the TAM family of receptor tyrosine kinases (RTK)—plays a pivotal role in apoptotic substrate cleaning from the retina, the testis and the ovaries through unconventional autophagy-assisted phagocytosis process LAP (LC3-associated phagocytosis). In this review, we focus on the interplay between TAM RTKs, autophagy-related proteins, LAP, and Toll-like receptors (TLR), as well as the regulatory mechanisms allowing these components to sustain tissue homeostasis and prevent functional ablation of the retina, the testis and the ovaries.