Expression and regulation of Kit ligand in the ovary of the hen

Ovarian nesfatin-1 in Hemidactylus flaviviridis: Reproductive phase-dependent expression, role and hormonal regulation

Nesfatin-1 has recently emerged as a modulator of ovarian functions in mammals. Studies in non-mammalian vertebrates, though limited and majorly restricted to fishes, have evidenced a role of this peptide in the regulation of ovarian steroidogenesis and oocyte maturation. Interestingly, nesfatin-1 remains completely unexplored in reptiles. Therefore, the present study aimed to identify nesfatin-1 and elucidate its role and regulation in the ovary of Hemidactylus flaviviridis. Ovarian expression of nucb2/nesfatin-1 was highest during late recrudescence and breeding while it was lowest during regression. Follicular stage-dependent expression analysis showed significantly high expression of nucb2/nesfatin-1 in previtellogenic follicles. Further, in vitro treatment of recrudescent wall lizard ovaries with nesfatin-1 resulted in increased expression of anti-apoptotic gene, bcl-2, along with a concomitant decline in the pro-apoptotic gene, caspase-3. In addition, proliferation/differentiation markers like scf, c-kit, pcna, and bmp-15 were stimulated in ovaries incubated with the peptide. Ovarian steroidogenesis was also positively influenced by nesfatin-1 as treatment with the peptide resulted in heightened star expression as well as increased estradiol and progesterone production. Also, all concentrations of nesfatin-1 stimulated glucose uptake and metabolism in wall lizard ovary. Our observations provide the first evidence of ovarian functions of nesfatin-1 in a reptile. Further, ovarian nucb2/nesfatin-1 was differentially regulated by gonadotropin and sex steroids wherein its expression was stimulated by dihydrotestosterone (DHT) and 17β-estradiol (E2) but inhibited by follicle-stimulating hormone (FSH). In summary, this is the first report of the presence, reproductive stage-dependent expression, role, and regulation of ovarian nucb2/nesfatin-1 in H. flaviviridis.

Vitamin D3 Receptors and Metabolic Enzymes in Hen Reproductive Tissues

In recent years, vitamin D3 has been revealed as an important regulator of reproductive processes in humans and livestock; however, its role in the female reproductive system of poultry is poorly known. The aim of this study was to examine vitamin D3 receptor (VDR and PDIA3) and metabolic enzyme (1α-hydroxylase and 24-hydroxylase) mRNA transcript and protein abundances, and protein localization within the hen ovary, oviductal shell gland, pituitary, liver, and kidney. We demonstrated, for the first time, the patterns of the relative mRNA and protein abundances of examined molecules in the ovary, dependent on follicle development and the layer of follicle wall, as well as in other examined organs. Immunohistochemically, PDIA3, 1α-hydroxylase, and 24-hydroxylase are localized in follicular theca and granulosa layers, luminal epithelium and tubular glands of the shell gland, pituitary, liver, and kidney. These results indicate that reproductive tissues have both receptors, VDR, primarily involved in genomic action, and PDIA3, probably participating in the rapid, non-genomic effect of vitamin D3. The finding of 1α-hydroxylase and 24-hydroxylase expression indicates that the reproductive system of chickens has the potential for vitamin D3 synthesis and inactivation, and may suggest that locally produced vitamin D3 can be considered as a significant factor in the orchestration of ovarian and shell gland function in hens. These results provide a new insight into the potential mechanisms of vitamin D3 action and metabolism in the chicken ovary and oviduct.

An Overview of the Current Known and Unknown Roles of Vitamin D3 in the Female Reproductive System: Lessons from Farm Animals, Birds, and Fish

Recent studies have clearly shown that vitamin D₃ is a crucial regulator of the female reproductive process in humans and animals. Knowledge of the expression of vitamin D₃ receptors and related molecules in the female reproductive organs such as ovaries, uterus, oviduct, or placenta under physiological and pathological conditions highlights its contribution to the proper function of the reproductive system in females. Furthermore, vitamin D₃ deficiency leads to serious reproductive disturbances and pathologies including ovarian cysts. Although the influence of vitamin D₃ on the reproductive processes of humans and rodents has been extensively described, the association between vitamin D₃ and female reproductive function in farm animals, birds, and fish has rarely been summarized. In this review, we provide an overview of the role of vitamin D₃ in the reproductive system of those animals, with special attention paid to the expression of vitamin D₃ receptors and its metabolic molecules. This updated information could be essential for better understanding animal physiology and overcoming the incidence of infertility, which is crucial for optimizing reproductive outcomes in female livestock.

Exploring differentially expressed key genes related to development of follicle by RNA-seq in Peking ducks (Anas Platyrhynchos)

Duck follicles enter different reproductive phases throughout life, and follicle gene expression patterns differ according to these phases. In particular, differentially expressed genes and related to development of follicle (mRNAs) play an important role to explore the key genes in this process; however, the expression profiles of these genes remain unclear. In this study, transcriptome sequencing was used to investigate the expression levels of duck ovarian genes, and comparative transcriptional analysis was carried out to identify differential genes, and cluster them into groups and function identification. The results showed differential expression of 593 coding genes between young and laying ducks, and of 518 coding genes between laying and old ducks. In further GO analysis, 35 genes from the comparison between old ducks and laying ducks have significant been changed involved in hormones related to follicle development. They include up-regulated genes StAR, CYP17, EPOX, 3β-HSD, CYP1B1 CYP19A1 and down-regulated genes SR-B1 in laying ducks hormone synthesis than old ducks. Among which EPOX is a key gene for time special highly expression during egg laying stage, and other key regulatory genes' highly expression showed in young and laying stage, and lower expression showing with follicular development stopping. Therefore, EPOX is a key regulator for duck follicle development in laying period, its expression level increase 100 times higher than in youth and decrease 98% than stop laying period in duck life cycle.

Di(2-ethylhexyl) phthalate (DEHP) influences follicular development in mice between the weaning period and maturity by interfering with ovarian development factors and microRNAs

Although studies have shown that di(2-ethylhexyl) phthalate (DEHP) can disrupt ovarian function, few reports have focused on follicular development in mice between the weaning period and maturity, especially with respect to microRNA (miRNA) expression. In this study, 21-day-old ICR mice were administered DEHP at doses of 0, 100, 400, and 1600 mg/(kg d) for 6 weeks by gavage. After DEHP administration, a significant decrease in the expression of follicle development-related factors (including c-kit, kitl, gdf9, and atm) was observed by quantitative real-time PCR (RT-PCR), but no significant difference in the proteins encoded by these genes was observed by Western blot. Bisulfite sequencing suggested that the total methylation percentages of promoter regions of these genes were not notably altered after DEHP exposure. However, RT-PCR revealed a significantly increased expression of ovarian miRNAs (let-7b, miR-17-5p miR-181a, and miR-151), which inhibit follicular granulosa cell proliferation. Overall, this study showed that DEHP administration from weaning to maturity could suppress the mRNA expression of follicular development factors, and this effect was not achieved through changes in the methylation of DNA in CpG islands of development factors. In addition, DEHP was shown to induce miRNAs to inhibit the proliferation of follicular granulosa cells and the anti-apoptosis function of KITL and GDF9 while increasing bax/bcl₂ expression to further promote the apoptosis of granulosa cells.

Differential regulation of Kit ligand A expression in the ovary by IGF-I via different pathways

Kit ligand (KITL) plays indispensable roles both in primordial follicle activation and in the maintenance of meiotic arrest of the oocyte. The regulation of KITL expression in the ovary, however, remains largely unknown. In the zebrafish, there are 2 paralogues of KITL, kitlga and kitlgb, and 2 Kit receptors, kita and kitb. Consistent with the situation in mammals, kitlga is only expressed in the ovarian follicle cells, and its cognate receptor kita is expressed in the oocyte. In the present study, we demonstrated that the expression of kitlga was promoted by IGF-I through its receptor IGF-IR. The stimulation involved transcription but not translation, suggesting that the kitlga gene is likely a direct downstream target of IGF-I signaling. Further experiments showed that the stimulatory effect of IGF-I was mediated by phosphatidyl inositol 3-kinase (PI3K)-Akt pathway. IGF-I also activated MEK-ERK pathway; however, this pathway suppressed kitlga expression. The regulation of kitlga expression by IGF-I appeared to depend on the stage of follicle development with a greater induction at early stage than late stage. This may be related to changes in IGF-I signaling pathways and/or local paracrine environment. In support of this were the differential expression of IGF-I receptors (igf1ra and igf1rb) and responsiveness of IGF-I signaling pathways, especially the PI3K-Akt pathway. Furthermore, the IGF-I-induced kitlga expression was inhibited by epidermal growth factor, an oocyte-derived paracrine factor in the zebrafish follicle. This study provides evidence for a controlling mechanism underlying the regulation of KITL expression in the ovary.