The effect of follicle-stimulating hormone (FSH) on the expression of FSH receptor in cultured rat granulosa cells

Knockdown of Ptprn-2 delays the onset of puberty in female rats

In the present study, we evaluated how Ptprn-2 (encoding tyrosine phosphatase, receptor type, N2 polypeptide protein) affects the onset of puberty in female rats. We evaluated the expression of Ptprn-2 mRNA and protein in the hypothalamus-pituitary-ovary axis of female rats using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunofluorescence at infancy, prepuberty, puberty, peripuberty, and adulthood. We evaluated the effects of Ptprn-2 gene knockdown on different aspects of reproduction-related biology in female rats, including the expression levels of puberty-related genes in vivo and in vitro, the time to onset of puberty, the concentration of serum reproductive hormones, the morphology of ovaries, and the ultrastructure of pituitary gonadotropin cells. Our results demonstrated that PTPRN-2 was primarily distributed in the arcuate nucleus (ARC), periventricular nucleus (PeN), adenohypophysis, and the ovarian follicular theca, stroma, and granulosa cells of female rats at various stages. Ptprn-2 mRNA levels significantly varied between peripuberty and puberty (P < 0.05) in the hypothalamus and pituitary gland. In hypothalamic cells, Ptprn-2 knockdown decreased the expression of Ptprn-2 and Rfrp-3 mRNA (P < 0.05) and increased the levels of Gnrh and Kiss-1 mRNA (P < 0.05). Ptprn-2 knockdown in the hypothalamus resulted in delayed vaginal opening compared to the control group (n = 12, P < 0.01), and Ptprn-2, Gnrh, and Kiss-1 mRNA levels (P < 0.05) all decreased, while the expression of Igf-1 (P < 0.05) and Rfrp-3 mRNA (P < 0.01) increased. The concentrations of FSH and P₄ in the serum of Ptprn-2 knockdown rats were lower than in control animals (P < 0.05). Large transverse perimeters and longitudinal perimeters (P < 0.05) were found in the ovaries of Ptprn-2 knockdown rats. There were fewer large secretory particles from gonadotropin cells in adenohypophysis tissue of the Ptprn-2 knockdown group compared to the control group. This indicates that Ptprn-2 knockdown can regulate levels of Gnrh, Kiss-1, and Rfrp-3 mRNA in the hypothalamus, regulate the concentration of serum FSH and P₄, and alter the morphology of ovarian and gonadotropin cells, delaying the onset of puberty in female rats.

A deletion mutation within the goat AKAP13 gene is significantly associated with litter size

A-kinase anchoring protein 13 (AKAP13) is one of the AKAP protein family members, which is correlated with estrogen receptors (ERs) and progesterone receptor (PR) activity. Consequently, the AKAP13 gene is considered to be one of the candidate genes for regulating female fertility. Hence, the objectives of this study were to discover the potential insertion/deletion (indel) variants within the AKAP13 gene and evaluate their associations with litter size of Shaanbei white cashmere goats (SBWC) to screen candidate genes for the molecular marker-assisted selection (MAS). Ultimately, we found the 16-bp deletion of AKAP13 gene which displayed three genotypes (II, ID and DD). However, it was not confirmed to Hardy-Weinberg equilibrium (HWE) in the tested population. Statistical analysis demonstrated that this 16-bp indel locus was significantly associated with litter size in goats (p < 0.05), in which the ID genotype was a key genotype for increasing litter size in goats. Besides, independent χ² tests between different genotypes and litter size showed that high-prolific groups had higher frequency of the 'D' allele (p < 0.05). Briefly, AKAP13 gene is a candidate gene for improving fertility, and its 16-bp indel locus can be used as a valid DNA molecular marker for the MAS in goat breeding.

High doses of FSH induce autophagy in bovine ovarian granulosa cells via the AKT/mTOR pathway

Follicle-stimulating hormone (FSH) plays a critical role in follicular growth and granulosa cell function; however, the mechanism by which the aggressive stimulation of FSH leads to poorer oocyte quality and embryo development potential is unclear. In this study, bovine ovarian granulosa cells (BGCs) were challenged with FSH doses (vehicle, 0.1, 1, 10 and 100 ng/ml) to investigate the effects of FSH on BGCs. The results indicated that the relative viability of BGCs was significantly increased in cells challenged with 1 ng/ml FSH, whereas the viability was significantly decreased with 100 ng/ml FSH treatment. The mRNA abundance of FSHR, CYP19, StAR and BAX was significantly upregulated with 1, 10 and 100 ng/ml of FSH, while the BCL-2 mRNA level was downregulated with higher concentrations of FSH (10 and 100 ng/ml). Furthermore, BGC autophagy was detected in cells treated with 10 and 100 ng/ml FSH by MDC staining, and the mRNA abundance of LC3, BECN1, BNIP3, ATG3 and ATG7 was upregulated with increasing FSH concentration. Meanwhile, the protein expression of LC3 was increased in cells treated with 10 and 100 ng/ml FSH. 1 and 10 ng/ml FSH significantly increased E2 production, whereas 10 and 100 ng/ml FSH significantly increased P4 production. FSH significantly inhibited the phosphorylation of AKT in cells treated with higher concentrations (1, 10 and 100 ng/ml), while activating mTOR phosphorylation at concentrations of 10 and 100 ng/ml of FSH. In summary, we can conclude that higher doses of FSH (10 and 100 ng/ml) induce BGC autophagy via the AKT/mTOR signalling pathway.

Expression of FSH receptor in the hamster ovary during perinatal development

FSH plays an important role in ovarian follicular development, and it functions via the G-protein coupled FSH receptor. The objectives of the present study were to determine if full-length FSHR mRNA and corresponding protein were expressed in fetal through postnatal hamster ovaries to explain the FSH-induced primordial follicle formation, and if FSH or estrogen (E) would affect the expression. A full-length and two alternately spliced FSHR transcripts were expressed from E14 through P20. The level of the full-length FSHR mRNA increased markedly through P7 before stabilizing at a lower level with the formation and activation of primordial follicles. A predicted 87 kDa FSHR protein band was detected in fetal through P4 ovaries, but additional bands appeared as ovary developed. FSHR immunosignal was present in undifferentiated somatic cells and oocytes in early postnatal ovaries, but was granulosa cells specific after follicles formed. Both eCG and E significantly up-regulated full-length FSHR mRNA levels. Therefore, FSHR is expressed in the hamster ovary from the fetal life to account for FSH-induced primordial follicle formation and cAMP production. Further, FSH or E regulates the receptor expression.

Maternal malnutrition during lactation affects folliculogenesis, gonadotropins, and leptin receptors in adult rats

OBJECTIVE

The goal of this study was to evaluate if maternal malnutrition during lactation could possibly program folliculogenesis, the ovarian expression of gonadotropins, leptin, and their receptors.

METHODS

At parturition, dams were randomly assigned to a control group (C), with free access to a standard laboratory diet containing 23% protein, and a protein-energy-restricted group (PER), with free access to an iso-energy and protein-restricted diet containing 8% protein. After weaning, all female pups had free access to the standard laboratory diet until 90 d of age when they were euthanized in the diestrum stage.

RESULTS

Maternal malnutrition caused decreases in the number of primordial (C 6.60 ± 0.24, PER 5.20 ± 0.20, P = 0.01), primary (C 5.80 ± 0.66, PER 4.00 ± 0.31, P = 0.04), and Graafian (C 2.18 ± 0.29, PER 1.08 ± 0.37, P = 0.05) follicle numbers. Maternal malnutrition led to a significant decrease in the aromatase mRNA expression (C 0.536 ± 0.008, PER 0.353 ± 0.041, P = 0.01) follicle-stimulating hormone receptor (C 1.25 ± 0.17, PER 0.75 ± 0.02, P = 0.04), luteinizing hormone receptor (C 0.93 ± 0.09, PER 0.54 ± 0.10, P = 0.03), leptin (C 0.55 ± 0.03, PER 0.42 ± 0.03, P = 0.04), Ob-R (C 1.05 ± 0.12, PER 0.64 ± 0.07, P = 0.03), and Ob-Rb (C 1.34 ± 0.21, PER 0.47 ± 0.10, P = 0.02) transcripts when compared with C.

CONCLUSION

Maternal malnutrition during lactation modulates folliculogenesis and the expression of the different isoforms of leptin and gonadotropin receptors and the aromatase enzyme. This probably is a consequence of alterations in perinatal leptin concentrations that may play a crucial role in determining the occurrence of long-term metabolic changes.

Effect of estrogen on the expression of luteinizing hormone-human chorionic gonadotropin receptor messenger ribonucleic acid in cultured rat granulosa cells

Estrogen has been considered to enhance FSH actions in the ovary, including the induction of the LH receptor (LHR). In this study, we elucidated the mechanism underlying the effect of estrogen on the induction of LHR by FSH in rat granulosa cells. Estradiol clearly enhanced the FSH-induced LHR mRNA increase in a time- and dose-dependent manner, with a maximum increase of approximately 3.5-fold at 72 h, compared with the level of LHR mRNA solely induced by FSH. We then investigated whether the effect of estrogen on LHR mRNA was due to increased transcription and/or altered mRNA stability. A luciferase assay with the plasmid containing the LHR 5'-flanking region did not show that estradiol increased the promoter activity induced by FSH. In contrast, the decay curves for LHR mRNA showed a significant increase in half-life with FSH and estradiol, suggesting that the increased stability of LHR mRNA is at least responsible for the regulation of LHR mRNA by estrogen. Recently mevalonate kinase (Mvk) was identified as a trans-factor that binds to LHR mRNA and alters LHR mRNA stability in the ovary. We found that estradiol, with FSH, decreased Mvk mRNA levels in rat granulosa cell culture, resulting in up-regulation of LHR mRNA that was inversely correlated to Mvk mRNA expression. Furthermore, the augmentation of FSH-induced LHR expression in the presence of estrogen was erased with the overexpression of Mvk by transient transfection. Taken together, these data indicate that LHR mRNA is up-regulated due to increased stability when estrogen negatively controls Mvk.

Zebrafish gonadotropins and their receptors: I. Cloning and characterization of zebrafish follicle-stimulating hormone and luteinizing hormone receptors--evidence for their distinct functions in follicle development

In the present study, we cloned and characterized zebrafish FSH receptor (Fshr) and LH receptor (Lhr). Both fshr and lhr were abundantly expressed in the zebrafish gonads; however, they could also be detected in the kidney and liver, respectively. When overexpressed in mammalian cell lines together with a cAMP-responsive reporter gene, zebrafish Fshr responded to goldfish pituitary extract but not hCG, whereas Lhr could be activated by both. It was further demonstrated that Fshr was specific to bFSH, while Lhr could be stimulated by both bovine FSH and LH. Low level of fshr expression could be detected in the immature ovary, but the level steadily increased during vitellogenesis of the first cohort of developing follicles. In contrast, the expression of lhr could barely be detected in the immature ovary, but it became detectable at the beginning of vitellogenesis and steadily increased afterward with the peak level reached at the full-grown stage. At the follicle level, the expression of fshr was very weak in the follicles of primary growth stage but significantly increased with the follicles entering vitellogenesis. However, after reaching the maximal level in the midvitellogenic follicles, the level of fshr expression dropped slightly but significantly at the full-grown stage. In comparison, the expression of lhr obviously lagged behind that of fshr. Its expression became detectable only when the follicles started to accumulate yolk granules, but the level rose steadily afterward and reached the peak at the full-grown stage before oocyte maturation. These results suggest differential roles for Fshr and Lhr in zebrafish ovarian follicle development.

Downregulation of Follicle-Stimulating Hormone (FSH)-Receptor Messenger RNA Levels in the Hamster Ovary: Effect of the Endogenous and Exogenous FSH1

Although gonadotropins have been reported to downregulate FSH-receptor (FSHR) mRNA levels in the ovaries of female rats, the effect of the gonadotropin surge, particularly FSH, on hamster follicular FSHR mRNA levels warrants further examination. The objectives of the present study were to clone and determine the complete FSHR cDNA sequence of the hamster and to delineate the effects of endogenous and exogenous FSH on the steady-state levels of ovarian FSHR mRNA. Complete FSHR cDNA was derived from hamster ovarian total RNA by the strategy of 3'- and 5'-rapid amplification of cDNA ends. Ovaries were obtained before and after the endogenous gonadotropin surge or exogenous FSH administration, and the steady-state levels of FSHR mRNA were assessed by Northern blot hybridization. Cloned FSHR cDNA consists of a reading frame corresponding to exons 1-10 of the human FSHR gene and the 5'- and 3'-untranslated regions. The nucleic acid and amino acid sequences of the reading frame were at least 87% and 92% identical, respectively, to that of human, rat, and mouse FSHR. Furthermore, the amino acid sequence contained seven transmembrane domains characteristic of the FSHR. The steady-state levels of FSHR mRNA increased from estrus (Day 1) to reach a peak on proestrus (Day 4) noon; however, significant attenuation was noted following the gonadotropin surge, which was blocked by phenobarbital. Exogenous FSH also downregulated, both dose- and time-dependently, ovarian FSHR mRNA levels. These data indicate that the nucleic acid sequence of hamster FSHR has been identified and that FSH modulates FSHR mRNA levels in the hamster ovary.

Overcompensation stimulation: a mechanism for hormetic effects

Whether hormetic responses result from a direct or an overcompensation type of stimulatory response has been an unresolved and contentious issue in both radiation and chemical toxicology. The goal of the present article is to identify numerous examples of overcompensation stimulation in the biological/biomedical literature and to evaluate their descriptive and quantitative features. The findings provide support for the hypothesis that hormetic dose-response relationships from a broad array of biological models can occur after an initial disruption in homeostasis. The finding also demonstrates the significant role of temporal factors in the assessment of dose response relationships.

Control of the expression of luteinizing hormone receptor by local factors in rat granulosa cells

To identify the mechanisms underlying the hormone-dependent induction and maintenance of luteinizing hormone receptor (LH-R) in rat granulosa cells, the effect of follicle-stimulating hormone (FSH) and local factors on the LH-R mRNA levels were studied. LH-R mRNA levels of the cells incubated with FSH decreased rapidly after medium removal, and readdition of FSH with the fresh medium did not restore these levels. On the other hand, 8-bromoadenosine 3,5-cyclic monophosphate significantly enhanced the expression of LH-R mRNA after medium removal, while the level of LH-R mRNA was lower than that of the cells replaced by original medium including FSH. In addition, the incubation with 8-Br-cAMP produced dose-dependent responses for LH-R mRNAs and enhanced the activity of 1379 bp of the LH-R 5'-flanking region, while the level of LH-R mRNA decreased 3 days after medium removal. Further studies were undertaken to assess the role of factors in maintaining the LH receptor once induced by FSH. Since FSH and cAMP increase follistatin production in granulosa cells, we examined the effect of follistatin on LH-R induction in the presence of activin and FSH. Activin induced LH-R in the presence of FSH significantly, and follistatin antagonized this effect in a dose-dependent manner. However, insulinlike growth factor-I (IGF-I) induced LH-R mRNA in the presence of FSH even after medium change. IGF-I might be one of the important factors that act in the medium to maintain LH-R levels in granulosa cells.