Molecular and cellular mechanisms for the regulation of ovarian follicular function in cows

The Effect of Prolactin on Gene Expression and the Secretion of Reproductive Hormones in Ewes during the Estrus Cycle

Prolactin (PRL) plays an important role in animal follicle development and ovulation. However, its regulatory effects on the different stages of the estrus cycle in ewes are unclear. In this study, bromocriptine (BCR, PRL inhibitor) was used to study the effect of PRL on the secretion of reproductive hormones and gene expressions in order to explore its regulatory effects on the sexual cycle of ewes. Eighty healthy ewes with the same parity and similar weights were randomly assigned to the control group (C, n = 40) and the treatment group (T, n = 40, fed bromocriptine). After estrus synchronization, thirty-one ewes with overt signs of estrus were selected from each group. Six blood samples were randomly obtained by jugular venipuncture to measure the concentration of PRL, estrogen (E2), progesterone (P4), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and gonadotropin-releasing hormone (GnRH) in the proestrus, estrus, metestrus, and diestrus. At the same time, we collected the ovaries of the six ewes in vivo after anesthesia in order to detect follicle and corpus luteum (CL) counts and measure the expression of hormone-receptor and apoptosis-related genes. The results show that PRL inhibition had no significant effects on the length of the estrus cycle (p > 0.05). In proestrus, the number of large and small follicles, the levels of E2, FSH, and GnRH, and the expressions of ER, FSHR, and the apoptotic gene Caspase-3 were increased (p < 0.05); and the number of middle follicles and the expression of anti-apoptotic gene Bcl-2 were decreased (p < 0.05) in the T group. In estrus, the number of large follicles, the levels of E2 and GnRH, and the expressions of the StAR, CYP19A1, and Bcl-2 genes were increased (p < 0.05), and the number of middle follicles was decreased (p < 0.05) in the T group. In metestrus, the number of small follicles and the expression of LHR (p < 0.05) and the pro-apoptotic gene Bax were increased (p < 0.05); the number of middle follicles was decreased (p < 0.05) in the T group. In diestrus, the number of large follicles, middle follicles, and CL, the level of P4, and the expressions of PR, 3β-HSD, StAR, Caspase-3, and Bax were increased (p < 0.05); the number of small follicles and the expression of Bcl-2 were decreased (p < 0.05) in the T group. In summary, PRL inhibition can affect the secretion of reproductive hormones, the follicle count, and the gene expression during the estrus cycle. These results provide a basis for understanding the mechanisms underlying the regulation of the ewe estrus cycle by PRL.

The Anti-Müllerian Hormone as Endocrine and Molecular Marker Associated with Reproductive Performance in Holstein Dairy Cows Exposed to Heat Stress

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10-6). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.

Heat shock proteins exhibit distinct spatiotemporal expression patterns in the domestic cat (Felis catus) ovary during the oestrous cycle

Heat shock proteins (HSP) are significant regulators of cell proliferation, differentiation and apoptosis. HSP participate in ovarian physiology through proliferative and apoptotic mechanisms and the modulation of sex steroid receptor functions. We investigated whether the expression and localisation patterns of HSP in the domestic cat ovary vary with the oestrous cycle stage. Immunohistochemical analysis revealed cell type-specific localisation patterns of HSPD1/HSP60, HSPA/HSP70, HSPC/HSP90 and HSPH/HSP105 in several ovarian cells of the domestic cat, including oocytes, follicular (granulosa and theca cells) and luteal cells, stromal and thecal interstitial cells, stromal cells, and vascular endothelial and smooth muscle cells during the anoestrous, follicular and luteal phases of the oestrous cycle. Western blot results showed that the expression of three HSP (HSPD1/HSP60, HSPA/HSP70 and HSPH/HSP105) varied with the oestrous cycle stage. While the maximal expression of HSPD1/HSP60 and HSPH/HSP105 occurred during the luteal phase, the expression of HSPA/HSP70 was minimal. The expressions of HSPA/HSP70 and HSPH/HSP105 were low during the follicular phase compared to the anoestrous phase. In conclusion, the alterations that occur in the expression of HSP in the domestic cat ovary during the different stages of the oestrous cycle imply that these proteins participate in the regulation of ovarian function under different physiological conditions.

Effects of 4-vinylcyclohexene diepoxide on the cell cycle, apoptosis, and steroid hormone secretion of goat ovarian granulosa cells

4-Vinylcyclohexene diepoxide (VCD) is a potentially hazardous industrial chemical that may enter a goat's body in various ways during industrial breeding. Ovarian granulosa cells (GCs) play a critical role in supporting follicle development and hormone synthesis. However, there are few studies on the effect of VCD on goat ovarian GCs. In this study, goat ovarian GCs were isolated and treated with VCD. The results showed that treatment with VCD increased the proportion of S phase and G2/M cells, but decreased the proportion of G1 phase. VCD treatment significantly inhibited the expression of cyclin A and cyclin-dependent kinase 2 (CDK2). But the expression levels of p21 and p27 were increased. VCD could induce an apparent increase in the proportion of apoptosis and the level of cleaved caspase 3. Treatment with VCD significantly reduced the progesterone and estrogen concentration in the medium in which goat ovarian GCs were cultured. Correspondingly, the expression level of steroidogenic acute regulatory protein (STAR) was significantly downregulated. Treatment with 0.25 and 0.5 mM VCD, the protein expression level of insulin-like growth factor 1 receptor (IGF1R) and Akt were significantly decreased. Moreover, treatment with 0.25 mM VCD significantly inhibited the phosphorylation of Akt. In conclusion, VCD exposure had cytotoxic effects such as decreased cell viability, disordered cell cycle, increased apoptosis, and interference with steroid hormone synthesis on goat GCs. These cytotoxic effects of VCD on goat GCs may be due to the downregulation of IGF1R and the inhibition of IGF1R/Akt signaling pathway.

Polymorphism analysis and expression profile of the estrogen receptor 2 gene in Leizhou black duck

Our previous study on the ovarian transcriptomic analysis in Leizhou black duck revealed that the ESR2 gene was involved in hormone regulation in reproduction and the estrogen signaling pathway related to reproductive performance was enriched. This suggested that ESR2 may have a functional role in the reproductive performance of the Leizhou black duck. Thus, this study aimed at evaluating the polymorphism of the ESR2 gene and its association with egg-laying traits and the distribution pattern of ESR2 mRNA in laying and non-laying Leizhou black ducks. In this study, genomic DNA was extracted from blood samples of 101 Leizhou black ducks to identify single nucleotide polymorphisms (SNPs) of the ESR2 gene to elucidate molecular markers highly associated with egg-laying traits. Four each of laying and non-laying Leizhou black ducks were selected to collect different tissues to analyze the ESR2 gene expression. A total of 23 SNPs were identified and association analysis of the single SNP sites showed that SNPs g.56805646 T>C and exon 3-20G>A were significantly (P < 0.05) associated with egg weight. Ducks with CT and AG genotypes had significantly higher (P < 0.05) egg weights than their respective other genotypes. Haplotype association analysis of g.56805646 T>C and exon 3-20G>A showed that the haplotypes were significantly associated with egg weight. Higher egg weight was seen in individuals with H3H4 haplotypes. In the hypothalamus-pituitary-gonadal (HPG) axis, the results of qRT/PCR showed that ESR2 mRNA was significantly (P < 0.05) expressed in the ovaries of both duck groups than in the hypothalamus and pituitary. In the oviduct, ESR2 was significantly (P < 0.05) higher in the infundibulum and magnum of laying and non-laying ducks respectively. This study provides a molecular marker for selecting Leizhou black ducks for egg production. In addition, it offers theoretical knowledge for studying the related biological functions of the ESR2 gene at the cellular level.

Effects of bone morphogenetic protein 4, gremlin, and connective tissue growth factor on estradiol and progesterone production by bovine granulosa cells

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-β family of proteins that have been implicated in the paracrine regulation of granulosa cell (GC) function, but whether responses to BMPs change with follicular size or interact with connective tissue growth factor (CTGF) or BMP antagonists (e.g., gremlin [GREM]) to directly affect GC function of cattle is unknown. Therefore, to determine the effects of BMP4 on proliferation and steroidogenesis of GCs and its interaction with GREM or CTGF, experiments were conducted using bovine GC cultures. In vitro, BMP4 (30 ng/mL) inhibited (P < 0.05) follicle-stimulating hormone (FSH) plus insulin-like growth factor 1 (IGF1)-induced progesterone and estradiol production by large- and small-follicle GCs, but the inhibitory effect of BMP4 on estradiol production was much more pronounced in large-follicle GCs. In small-follicle GCs, BMP4 had no effect (P > 0.10) on IGF1-induced proliferation, but GREM inhibited (P < 0.05) cell proliferation and estradiol and progesterone production in IGF1 plus FSH-treated GCs. In large-follicle GCs, BMP4 (10 to 30 ng/mL) increased (P < 0.05) GC numbers and GREM (100 ng/mL) blocked this effect. In large-follicle GCs, CTGF inhibited (P < 0.05) FSH plus IGF1-induced progesterone and estradiol production, and CTGF blocked the stimulatory effect of BMP4 on GC proliferation. These results indicate that BMP4, GREM, and CTGF inhibit GC aromatase activity and progesterone production. Also, the stimulatory effect of BMP4 on GC proliferation and the inhibitory effects of BMP4 on GC steroidogenesis are more pronounced in large vs. small follicles.

The ovarian follicle of ruminants: the path from conceptus to adult

This review resulted from an international workshop and presents a consensus view of critical advances over the past decade in our understanding of follicle function in ruminants. The major concepts covered include: (1) the value of major genes; (2) the dynamics of fetal ovarian development and its sensitivity to nutritional and environmental influences; (3) the concept of an ovarian follicle reserve, aligned with the rise of anti-Müllerian hormone as a controller of ovarian processes; (4) renewed recognition of the diverse and important roles of theca cells; (5) the importance of follicular fluid as a microenvironment that determines oocyte quality; (6) the 'adipokinome' as a key concept linking metabolic inputs with follicle development; and (7) the contribution of follicle development to the success of conception. These concepts are important because, in sheep and cattle, ovulation rate is tightly regulated and, as the primary determinant of litter size, it is a major component of reproductive efficiency and therefore productivity. Nowadays, reproductive efficiency is also a target for improving the 'methane efficiency' of livestock enterprises, increasing the need to understand the processes of ovarian development and folliculogenesis, while avoiding detrimental trade-offs as greater performance is sought.

Bee pollens originating from different species have unique effects on ovarian cell functions

CONTEXT

The species-specific differences and mechanisms of action of bee pollen on reproduction have not been well studied.

OBJECTIVE

We compared the effects of bee pollen extracts from different plants on ovarian cell functions.

MATERIALS AND METHODS

We compared the effects of pollens from black alder, dandelion, maize, rapeseed, and willow at 0, 0.01, 0.1, 1, 10, or 100 µg/mL on cultured porcine ovarian granulosa cells. Cell viability was assessed with a Trypan blue test, the cell proliferation marker (PCNA), and an apoptosis marker (BAX) were assessed by immunocytochemistry. Insulin-like growth factor (IGF-I) release was measured by an enzyme-linked immunosorbent assay.

RESULTS

Addition of any bee pollen reduced cell viability, promoted accumulation of both proliferation and apoptosis markers, and promoted IGF-I release. The ability of various pollens to suppress cell viability ranked as follows: rapeseed > dandelion > alder > maize > willow. The biological activity of bee pollens regarding their stimulatory action on ovarian cell proliferation ranked as follows: dandelion > willow > maize > alder > rapeseed. Cell apoptosis was promoted by pollens as follows: range > dandelion > alder > rapeseed > willow > maize. The ability of the pollens to stimulate IGF-I output are as follows: willow > dandelion > rapeseed > maize > alder.

DISCUSSION

Bee pollen can promote ovarian cell proliferation by promoting IGF-I release, but it induces the dominance of apoptosis over proliferation and the reduction in ovarian cell viability in a species-specific manner.

CONCLUSIONS

This is the first demonstration of adverse effects of bee pollen on ovarian cell viability and of its direct stimulatory influence on proliferation, apoptosis, and IGF-I release. The biological potency of bee pollen is dependent on the plant species.

Plasma IGF1 and 17β-Estradiol Concentrations During the Follicular Wave in Llamas

The aim of this study was to characterize the temporal association between follicular waves and circulating concentrations of 17β-estradiol (E2) and IGF1 in llamas. Follicular waves could be clearly divided in three phases: growth, plateau and regression; with a mean duration of 18.8 ± 0.32 days. All follicular waves showed overlapping, so that as one dominant follicle was regressing, another one was growing. E2 plasma concentration showed a wavelike pattern, similar to that followed by the dominant follicle; reaching its maximum concentration at the end of the growth phase and decreasing at the end of the plateau phase. IGF1 also showed variations during the follicular wave. It tended to increase during the growth phase and decreased toward Days 14 and 16. IGF1 reached its maximum concentration before E2 did (5 ± 0.8 vs. 7.2 ± 0.5 days after wave emergence) and before the maximum follicular diameter was attained (10.2 ± 0.46 days after wave emergence). Both hormones started to rise again in coincidence with the development of a new follicular wave. The observed profiles allow to suggest that IGF1 could have a role on folliculogenesis and ovarian steroideogenesis in llamas, as reported for other species.

Ovarian transcriptomic analysis and follicular development of Leizhou black duck

This study investigated the factors that caused the differences in egg production during the development of ovarian follicles in Leizhou black ducks. Leizhou black ducks population was divided into 2 groups as high-yield group (HG) and low-yield group (LG). The number of eggs (NE), age at first egg (AFE), weight at first egg, and egg weight (EW) of both groups were recorded, and differences were analyzed using the t test. The logistic model was used to simulate the egg production curves to analyze the production rules. The ovarian follicles of both duck groups were collected to count the number of different grades sized follicles, weigh the ovaries, and observe follicular sections to analyze the developmental differences. Ovarian transcriptomic sequencing was performed to investigate differentially expressed genes and signal pathways in both duck groups. The results revealed a significant difference (P < 0.01) in the NE laid, AFE, and EW between both groups. Comparatively, HG had significantly more (P < 0.01) large yellow follicles (LYF) than LG. The density of medullary layer cells of the follicle section was greater in HG than LG ducks. Transcriptome sequencing revealed a total of 1,027 differentially expressed genes between the HG and LG ducks of which 495 genes were upregulated, and 532 genes were downregulated. Fifty genes were related to reproduction and reproductive processes. Kyoto Encyclopedia of Genes and Genomes–enriched signaling pathways revealed 274 signal pathways enriched in these differentially expressed genes of which the steroid biosynthesis pathway was significantly enriched. Analysis (Q < 0.05) showed that HSD3β → gonadotropin-releasing hormone (GnRH) and estrogen receptor (ESR) → LHβ/ERK1/2 were enriched in the steroid biosynthesis signal pathway. Follicle-stimulating hormone signal pathway mediated by HSD3β → GnRH and ESR → LHβ/ERK1/2 may be involved in ovarian follicle development to regulate LYF reserve process and affect its ovulation cycle, which in turn influence the egg production of Leizhou black ducks.

The localization and expression of epidermal growth factor and epidermal growth factor receptor in bovine ovary during oestrous cycle

Epidermal growth factor (EGF) is one of the important regulatory factors of EGF family. EGF has been indicated to effectively inhibit the apoptosis of follicular cells, to promote the proliferation of granulosa cells and the maturation of oocytes, and to induce ovulation process via binding to epidermal growth factor receptor (EGFR). However, little is known about the distribution and expression of EGF and EGFR in cattle ovary especially during oestrous cycle. In this study, the localization and expression rule of EGF and EGFR in cattle ovaries of follicular phase and luteal phase at different time points in oestrous cycle were investigated by using IHC and real-time qPCR. The results showed that EGF and EGFR in cattle ovary were mainly expressed in granulosa cells, cumulus cells, oocytes, zona pellucida, follicular fluid and theca folliculi externa of follicles. The protein and mRNA expression of EGF/EGFR in follicles changed regularly with the follicular growth wave both in follicular and in luteal phase ovaries. In follicular phase ovaries, the protein expression of EGF and EGFR was higher in antral follicles than that of those in other follicles during follicular growth stage, and the mRNA expression of EGFR was also increased in stage of dominant follicle selection. However, in luteal phase ovaries, the growth of follicles was impeded during corpus luteum development under the action of progesterone secreted by granular lutein cell. The mRNA and protein expressions of EGF and EGFR in ovarian follicles during oestrous cycle indicate that they play a role in promoting follicular development in follicular growth waves and mediating the selection process of dominant follicles.

Association among lipopolysaccharide, the transforming growth factor-beta superfamily, follicular growth, and transcription factors in spontaneous bovine ovarian cysts

The aim of this study was to investigate some of the growth and transcriptional factors originating from oocytes and granulosa cells in follicular fluid and to identify the relationships between the basic blood metabolite-metabolic hormones and intrafollicular lipopolysaccharide (LPS) concentrations. Thirty cows included in the study were allocated into 2 groups comprising 15 cows with healthy preovulatory follicles (cyclic cows) and 15 cows with confirmed cystic follicles. The ovaries and uteri of all cows were assessed by transrectal ultrasonographic examination. Blood serum samples were collected at 15, 25, 35, 45, and 55 d after calving for analysis of nonesterified fatty acids, β-hydroxybutyrate, insulin, glucose, IGF-I, ACTH, and cortisol. Ovaries and uteri were examined using transrectal ultrasound. Vaginal discharge was evaluated on the same days. Follicular fluid was also aspirated on days 35-55 from the healthy preovulatory follicles and cystic follicles using a transvaginal ovum pickup method. The densitometric levels of inhibin-α, growth and differentiation factor (GDF-9), bone morphogenetic protein (BMP-6), and GATA-4 and GATA-6 proteins were analyzed by the Western blotting technique; the concentrations of antimullerian hormone (AMH), IGF-I, estradiol-17 beta (E2), and progesterone (P4) were determined by ELISA; and the concentrations of LPS in the follicular fluid were measured by the Limulus amebocyte lysate test. The serum insulin, ACTH, and cortisol concentrations were higher in cystic cows than cyclic cows, but serum IGF-I concentrations were lower in cystic cows. The IGF-I concentrations of cystic follicular fluids were lower, whereas AMH levels were significantly greater than those of healthy preovulatory follicular fluids. The cystic follicles had significantly lower expression levels of GDF-9, BMP-6, GATA-4, and GATA-6; in contrast, inhibin-α expression and LPS concentrations were significantly higher than in healthy preovulatory follicles. The proportion of pathologic vaginal discharge within 25 d postpartum in cystic cows were higher than in the cyclic group. In conclusion, it is suggested that intrafollicular dysregulation of the transforming growth factor-β superfamily, growth, and transcriptional factors is affected by high intrafollicular LPS concentrations and systemic metabolic changes and these disturbances may be responsible for the generation of ovarian cysts.

Impact of short nutrient stimuli with different energy source on follicle dynamics and quality of oocyte from hormonally stimulated goats

The aim of this study was to verify the effect of the energy source for a short-term diet supplementation on follicular dynamics, ovarian response and oocyte recovery in goats. Thirty Anglo Nubian crossbred does received a diet for 4 weeks to satisfy the nutritional requirements of breeding for adult non-dairy goats. Seven days prior to oocyte recovery (OR), a group of does (n = 10) was supplemented with ground full-fat linseed in the diet (Diet A), whereas a second group of does (n = 10) received crude glycerine in the diet (Diet B). The total mixed ration (TMR) diet was maintained as the Control Diet (n = 10). All animals were oestrous-synchronized by the use of a progesterone insert for 12 days prior to OR. Follicles were stimulated by using pFSH (five 40-mg/ml doses) during the supplementation time. At OR, follicles were counted and recovered oocytes were classified as viable or degenerated. Follicular dynamics was monitored by ultrasonography, and plasma glucose, cholesterol and triglyceride levels were measured during supplementation. Glucose was higher in Diet B and cholesterol in Diet A. Diet B had a lower proportion of small (<3 mm) and large follicles (≥3 mm; p = 0.01). The follicular growth rate was higher in Diet A (p < 0.01), with follicles emerging in the 5th day of supplementation. No differences were observed for follicles counted and oocytes recovered. Thus, the type of energy source supplemented for a short term was capable to alter the follicular dynamics, without affecting the proportion of morphologically viable oocytes upon recovery.

Effects of reproductive season on embryo development in the buffalo

Interest in buffalo farming is increasing worldwide due to the critical role played by buffaloes as sources of animal protein in tropical and subtropical environments. However, reproductive seasonality negatively affects the profitability of buffalo farming. Buffaloes tend to be short-day breeders, with seasonality patterns increasing with greater distances from the Equator. Although ovarian cyclic activity may occur throughout the year, seasonal anoestrus and cycles in calving and milk production are recorded. When buffaloes are forced to mate during the unfavourable season, to meet market demand, they may undergo a higher incidence of embryo mortality. This review addresses the effects of the reproductive season on embryo development in the buffalo, analysing the different factors involved in determining embryo mortality during the unfavourable season, such as impaired luteal function, oocyte competence and sperm quality. The review then focuses on strategies to control the photoperiod-dependent annual fluctuations in conception and embryo mortality in the female buffalo.

The local regulation of folliculogenesis by members of the transforming growth factor superfamily and its relevance for advanced breeding programmes

Regulation of the growth and maturation of the ovarian follicle is critical for normal reproductive function. Alterations in this growth can lead to pathological conditions, such as cystic follicles, reduced oocyte quality, or an abnormal endocrine environment leading to poor fertility. Alterations in follicular growth also influence the number of follicles ovulating and thus can change litter size. Both endocrine factors, such as follicle stimulating hormone and luteinizing hormone, as well as local factors, are known to regulate follicular growth and development. This review will focus on the role of local factors in regulation of ovarian follicular growth in ruminants, with a focus on members of the transforming growth factor superfamily. The potential role of these factors in regulating proliferation, apoptosis, steroidogenesis and responsiveness to gonadotrophins will be considered.

Changes in DNA integrity and gene expression in ovarian follicular cells of lipopolysaccharide-treated female mice

BACKGROUND

Lipopolysaccharide (LPS), the endotoxin of gram-negative bacteria, can impair female reproductive function. However, there is a little information about genotoxic stress in ovarian follicular cells as well as about the changes in oocyte developmental potential under endotoxemia. So the aim of our study was to investigate in vitro oocyte maturation, the DNA damage and expression of some developmental competence-related genes in follicular cells of mice treated with LPS.

METHODS

LPS (3mg/kg) was intraperitoneally injected into the mice for 24h, and in vitro maturation of mouse oocyte was determined. The expression levels of genes in cumulus cells were detected by reverse transcriptase polymerase chain reaction. DNA damage in granulosa cells was assessed by the alkaline comet assay.

RESULTS

LPS injection caused an impairment of oocyte maturation in vitro: the percentage of oocytes reaching metaphase I and metaphase II decreased markedly compared to vehicle control mice. At the same time we observed strong DNA damage in granulosa cells of LPS-treated animals. The endotoxemia resulted in significantly reduced mRNA expression levels for hyaluronan synthase 2 (HAS2), cyclooxygenase 2 (COX2) and Gremlin-1 (GREM1) genes compared with control.

CONCLUSIONS

Our results obtained in a mouse model of endotoxin-induced female reproductive dysfunction suggest that LPS may affect oocyte quality through the induction of DNA damage and decreasing the cumulus expression of genes associated with cumulus expansion and oocyte maturation, such as HAS2, COX2 and GREM1.

Analysis of protein-protein interaction network based on transcriptome profiling of ovine granulosa cells identifies candidate genes in cyclic recruitment of ovarian follicles

After pubertal, cohort of small antral follicles enters to gonadotrophin-sensitive development, called recruited follicles. This study was aimed to identify candidate genes in follicular cyclic recruitment via analysis of protein-protein interaction (PPI) network. Differentially expressed genes (DEGs) in ovine granulosa cells of small antral follicles between follicular and luteal phases were accumulated among gene/protein symbols of the Ensembl annotation. Following directed graphs, PTPN6 and FYN have the highest indegree and outdegree, respectively. Since, these hubs being up-regulated in ovine granulosa cells of small antral follicles during the follicular phase, it represents an accumulation of blood immune cells in follicular phase in comparison with luteal phase. By contrast, the up-regulated hubs in the luteal phase including CDK1, INSRR and TOP2A which stimulated DNA replication and proliferation of granulosa cells, they known as candidate genes of the cyclic recruitment.

Effects of GnRH, a progesterone-releasing device, and energy balance on an oestrus synchronisation program in anoestrous dairy cows

OBJECTIVE

The aim of this research was to study the roles of the day 0 energy balance and gonadotrophin-releasing hormone (GnRH) and progesterone levels on dominant follicle (DF) and corpus luteum (CL) development during the first 7 days of a gonadotrophin-prostaglandin-gonadotrophin (GPG) + progesterone (P4) program in anoestrous dairy cows.

METHODS

Cows (n = 81) were allocated to one of the three treatments: (1) GPG + P4 (days 0 and 9, 100 µg GnRH; day 0-7, intravaginal P4 device; day 7, 500 µg PGF_2α ); (2) GPG (as for treatment 1 but excluding the P4 device) and (3) prostaglandin + GnRH + P4 (as for treatment 1, but excluding day 0 GnRH). DF and CL size, plasma concentrations of insulin, insulin-like growth factor-I (IGF-I) and non-esterified fatty acid (NEFA) were measured on days 0 and 7.

RESULTS

The proportion of cows with a CL on day 7 was significantly different between groups (GPG: 78%, GPG+P4: 69%, PGF_2α + GnRH + P4: 42%, P = 0.02). The CL volume on day 7 was significantly associated with treatment, treatment by time postpartum and plasma concentrations of insulin, IGF-I and NEFA.

CONCLUSION

In cows without a CL present on day 0 of an oestrus synchronisation program, removal of the day 0 GnRH treatment led to reduced CL development; however, no effect of adding progesterone was found. In contrast, in cows with a CL present on day 0 inclusion of a progesterone device led to a higher CL volume, but removal of the first GnRH injection had no effect. Response to the treatment was affected by plasma concentrations of insulin, IGF-I and NEFA.