Altered expression of IL-1β, IL-1RI, IL-1RII, IL-1RA and IL-4 could contribute to anovulation and follicular persistence in cattle

Immunophenotypic profiles and inflammatory markers in Premature Ovarian Insufficiency

Premature Ovarian Insufficiency (POI), also known as Premature Ovarian Failure (POF), is a heterogeneous disorder characterized by the cessation of ovarian function before age 40. Clinical symptoms include menstrual disorders: amenorrhea/oligomenorrhea or symptoms of estrogen deficiency. This review aims to provide the most important summary of the immunophenotypic profile of premature ovarian failure syndrome, along with a review of the latest reports on the usefulness of inflammatory markers. The inflammatory microenvironment in POI applies to many levels. Concomitants of autoimmune ovarian inflammation and impaired cellular immune response may be a picture of impaired regulation in autoimmune ovarian disease. The serum concentration of pro-inflammatory cytokines, like IL-6, IL-8, IL-17, tumor necrosis factor α (TNF-α), and interferon-gamma (IFN-γ), tend to increase, whereas levels of the anti-inflammatory cytokine, IL-10, tend to decrease. In our review, we focus on whether the measured immunological parameters could help in the diagnosis and prognosis of the syndrome. Among the inflammatory markers, neutrophil-to-lymphocyte ratio (NLR) is noteworthy, as it is decreased in patients with POI. It is important to stress that besides case series, we need properly powered studies with randomization to answer which treatment is effective, and how to deal with concurrent autoimmunity. In this review, we emphasize the importance of the premature ovarian failure syndrome immunoprofile for a proper understanding of the complexity of this syndrome, potential diagnostic points, and therapeutic targets.

Ovarian leukocytes: Association with follicular persistence and cyst formation in dairy cows

One of the initial causes of cystic ovarian disease (COD) is a failure in the normal ovulation mechanism. This study aimed to characterize the populations of immune cells (T-lymphocytes, B-lymphocytes, monocytes-macrophages and granulocytes) present in the ovary of cows with COD and induced follicular persistence, and evaluate their relation with follicular persistence and cyst formation. The follicular persistence model was developed using a progesterone (P4) slow-release intravaginal device, to obtain subluteal concentrations of P4. Results evidenced that T-lymphocytes, B-lymphocytes and monocytes-macrophages in the cortex, medulla, and theca externa and interna of dominant follicles were higher in the control group than in the COD and all persistence groups. Granulocytes in the medulla and theca externa of dominant follicles were lower in the control group than in the COD group, and those in the cortex and medulla were lower in the control group than in the persistence groups. The presence of T-lymphocytes, B-lymphocytes and granulocytes in the follicular fluid was abundant, especially that of granulocytes, without differences between control and COD cows. These results suggest that the immune system potentially plays a role in the local mechanisms of COD pathogenesis in dairy cows. In spontaneous COD and in our follicular persistence model, the distribution of the cells studied was different from that in the control group. However, to our knowledge, this is the first report describing the presence of immune cells in bovine follicular fluid samples and the expression of steroid hormone receptors in infiltrating immune cells in the bovine ovary.

Ovulation Induced by Intrauterine Seminal Plasma Increases Total Protein, PGE2, IL-8, and IL-1β in Uterine Fluid of Llamas (Lama glama)

The establishment of a state of immunotolerance in the female reproductive tract is important for embryo development, implantation and placentation. Llamas are induced ovulators and more than 98% of pregnancies occur in the left uterine horn. The objective of this study was to determine the uterine immune response of llamas in different stages of the reproductive cycle. Adult llamas (n = 20) were examined daily by transrectal ultrasonography to determine follicular growth and then randomly assigned to four groups: Follicular phase (n = 5); Luteal phase induced by an intramuscular administration of 50 ug of GnRH analogue (n = 5); Luteal phase induced by intrauterine infusion of seminal plasma (n = 5); and Luteal phase induced by mating (n = 5). Uterine fluid was collected separately from both uterine horns by non-surgical flushing to determine the presence of cells, total proteins and concentration of IL-1β, IL-6, IL-8, IFN γ, TNF-α and PGE2. Inflammatory cells were not observed in the uterine fluid and total protein pattern and inflammatory mediators did not differ between the left and the right horn amongst groups. Llamas treated with an intrauterine infusion of seminal plasma showed the highest concentration of total proteins, inflammatory cytokines PGE2, IL-8 and IL-1β in the uterine fluid. In conclusion, seminal plasma is made up of significant numbers of signaling molecules that are able to modify the uterine immune response in llamas.

IL-6/IL-10 and IL-1β/IL-4 ratios associated with poor ovarian response in women undergoing in-vitro fertilization

The aim of this work was to evaluate whether serum cytokines levels are associated with ovarian response in IVF. 149 patients were included in a retrospective study. Cytokines IL-2, IL-4, IL- 6, IL-8, IL-10, VEGF, IFNγ, TNFα, IL-1α, IL-1β, MCP-1 and EGF were measured by sandwich immunoassay previously to ovarian stimulation. Performing hierarchical cluster analysis, we observed that the antral follicle count, the total oocytes recovered and the MII recovered are grouped in the same cluster as the cytokines IL-2-4-6-10-1α-1β, IFNγ y TNFα. Then, we found that the ratio between IL and 6 and IL-10 was higher in low responder women (2.15 versus 1.55; p = 0.035). If we establish 0.9 as a cut-off for the IL-6/IL-10, we observed that above this value the risk of having a low response to ovarian stimulation was more than 3 times greater than below this value (22.9 % versus 6.0 %; p = 0.007). Also, the ratio IL-1β/IL-4 was higher in patients with normal or suboptimal response (0.62 versus 0.34; p = 0.034) and any patient with low response had a value greater than 0.7 (p = 0.003). As a conclusion, the IL-6/IL-10 and IL-1β/IL-4 ratios showed differences between normoresponder women and patients with low ovarian response.

Decreased Expression of EZH2 in Granulosa Cells Contributes to Endometriosis-Associated Infertility by Targeting IL-1R2

The mechanism by which endometriosis, a common gynecological disease characterized by chronic pelvic pain and infertility, causes infertility remains elusive. Luteinized unruptured follicle syndrome, the most common type of ovulatory dysfunction, is a cause of endometriosis-associated infertility involving reduced numbers of retrieved and mature oocytes. Ovulation is controlled by luteinizing hormone and paracrine signals produced within the follicle microenvironment. Generally, interleukin (IL)-1β is elevated in endometriosis follicular fluid, whereby it amplifies ovulation signals by activating extracellular-regulated kinase 1/2 and CCAAT/enhancer binding protein β pathways. However, this amplification of ovulation by IL-1β does not occur in patients with endometriosis. To illuminate the mechanism of ovulatory dysfunction in endometriosis, we analyzed the effect of oxidative stress and IL-1β expression on endometriosis follicles. We found that oxidative stress decreased EZH2 expression and reduced H3K27Me3 levels in endometriosis ovarian granulosa cells (GCs). Selective Ezh2 depletion in mice ovarian GCs reduced fertility by disturbing cumulus-oocyte complex expansion and reducing epidermal growth factor-like factor expression. Gene expression and H3K27Me3 ChIP-sequencing (ChIP-Seq) of GCs revealed IL-1 receptor 2 (IL-1R2), a high-affinity IL-1β-receptor that suppresses IL-1β-mediated inflammatory cascades during ovulation, as a crucial target gene of the EZH2-H3K27Me3 axis. Moreover, IL-1β addition did not restore ovulation upon Ezh2 knockdown, indicating a vital function of IL-1R2 in endometriosis. Thus, our findings show that reducing EZH2 and H3K27Me3 in GCs suppressed ovulatory signals by increasing IL-1R2 expression, which may ultimately contribute to endometriosis-associated infertility.

An altered expression of components of the IGF system could contribute to follicular persistence in Holstein cows

In dairy cows, reproductive diseases such as cystic ovarian disease (COD) represent a major problem that impacts on dairy production. It has been postulated that the insulin-like growth factor (IGF) system may contribute to follicular persistence and development of COD. Thus, the aim of the present study was to analyze relevant members of the IGF system in a critical period immediately after the expected time of ovulation, to obtain information about their role in follicular persistence in dairy cows. Proteins of the IGF system were evaluated at 0 (expected day of ovulation), 5, 10 and 15 days of follicular persistence to determine whether the changes previously detected in cows with COD occur early in COD pathogenesis. The serum concentration of IGF1 was higher in cows with 10 and 15 days of follicular persistence than in control cows. IGF1 expression in granulosa cells was similar in the follicles analyzed. In contrast, in theca cells, persistent follicles of days 5 and 10 showed the lowest IGF1 expression. IGF binding protein (IGFBP) 2 and 3 expression was lower in persistent follicles than in dominant follicles of the control group. Although IGF receptor (IGFR) 1 expression was similar in the groups analyzed, p-IGFR1 expression was significantly higher in dominant follicles of the control group than in persistent follicles. These data suggest alterations in the IGF system at the early stages of follicular persistence. The evidences obtained allow supporting that the IGF system could plays a key role in dairy cattle reproduction.

Interleukin-4 activates the PI3K/AKT signaling to promote apoptosis and inhibit the proliferation of granulosa cells

The inflammatory microenvironment has been demonstrated to play a role in folliculogenesis, ovulation and premature ovarian failure (POF), as well as infertility. In this study, we aimed to explore the role of inflammation in modulating growth and apoptosis in granulosa cells (GCs), the main components of ovarian follicles. ELISA was used to analyze the levels of inflammatory factors (IL-1β, IL-4, IL-6 and IL-10) in follicular fluid samples and GCs derived from POF patients and healthy normal individuals. CCK-8, flow cytometry and TUNEL assays were used to assess the effect of IL-4 on GC growth and apoptosis. Western blotting was used to examine the effect of IL-4 on the activation of PI3K/Akt, Erk1/2 and Jnk signaling. The results showed that IL-4, IL-1β and IL-6 levels were increased in follicular fluid samples and GCs derived from POF patients compared with those from healthy individuals. GC growth was weakened when cells were treated with IL-4, while apoptosis was increased. In addition, IL-4 increased the level of p-Akt/Akt in GCs. In addition, LY294002, an inhibitor of PI3K, abolished the effect of IL-4 by inhibiting GC growth and promoting apoptosis. In summary, this study demonstrated that IL-4 levels were increased in POF samples and that IL-4 could inhibit GC growth and induce GC apoptosis by activating PI3K/Akt signaling.

Active immunization against GnRH as an alternative therapeutic approach for the management of Bos indicus oocyte donors diagnosed with chronic cystic ovarian disease

The aim of this study was to evaluate the effect of active immunization against GnRH in Nelore (Bos indicus) cows repeatedly used as oocyte donors that developed chronic cystic ovarian disease (COD). In the first experiment, ovarian and uterine features were first compared between COD cows (n = 15) and healthy cows (n = 22, cycling control group) from the same breed and herd. Cows with COD had a greater number of large (P < 0.0001) and medium follicles (P < 0.01) but lesser small follicles (P < 0.05) than cycling controls. Mucometra was diagnosed in 73.3% of COD cows, but in none of the controls. No difference in average thickness of the endometrium was detected between groups; however, endometrial thickness and mucometra score were negatively correlated (R = -0.73, P = 0.0029) in COD cows. In the second experiment, COD cows were randomly allocated into two experimental groups, which received two 1.0 mL SC injections of either an anti-GnRH vaccine (COD immunized group, n = 8) or saline (COD control group, n = 7), given 28 days apart. Cows were examined weekly by transrectal ultrasonography during nine consecutive weeks after the first injection to evaluate the number and distribution of follicles among size classes, endometrial thickness, and presence of clinical mucometra. Vaccination against GnRH resulted in a progressive suppression of follicle growth and a reduction in the average size of the largest follicle, as well as in the number of large follicles (P < 0.01) in COD immunized cows compared with COD controls from week 7 onwards. Conversely, the number of small follicles in the COD immunized group increased after week 5 and was greater (P = 0.0023) than controls on week 9. Endometrial thickness and mucometra score were not affected (P > 0.05) by immunization against GnRH. In the third experiment, the COD immunized cows with effective suppression of follicle growth four weeks after the 2nd injection (n = 6) were submitted to three consecutive ovum pick-up (OPU) sessions (weeks 10, 11, and 12) for in vitro embryo production (IVEP). Cumulus-oocyte complexes (COC) collected from slaughterhouse ovaries were used as controls for IVEP. COD cows with produced 25.0 ± 3.8 COC per OPU session with no apparent detrimental effect of anti-GnRH vaccine on oocyte developmental potential in vitro, i.e., we observed similar cleavage rate (P = 0.5914) and greater blastocyst rate (P = 0.0177) in immunized cows compared with COC from slaughterhouse controls. Finally, in the fourth experiment wave emergence and follicular dynamics after follicle ablation were compared between COD immunized cows with effective suppression of follicle growth and a subset (n = 6) of the cycling, control group. No follicles grew beyond 4 mm diameter after follicle ablation in the COD immunized group, whereas a normal follicular wave emergence occurred in cycling controls. Antral follicle count was similar between cycling controls and COD immunized groups at 24 h and 96 h post-follicle ablation (P > 0.05), but greater in cycling controls at 48 h and 72 h post-follicle ablation (P < 0.05). In summary, our results suggest that active immunization against GnRH is effective to induce the regression of follicular cysts as well as increase the number of small follicles growing on the ovaries, in oocyte donors diagnosed with chronic COD, with no apparent negative effect on oocyte developmental potential in vitro.

Timing of early resynchronization protocols affects subsequent pregnancy outcome in dairy cows

The aim of this study was to evaluate the outcomes of an early resynchronization protocol (Resynch) initiated at different timepoints after timed artificial insemination (TAI) and with unknown pregnancy status. Holstein cows (n = 164) were submitted to the following TAI protocol: D0, insertion of an intravaginal progesterone (P4) device and 2 mg im estradiol benzoate (EB); D8, removal of P4 device and treatment with 0.5 mg im sodium cloprostenol (PGF); D9, 0.1 mg im Lecirelin (LEC); and D10, TAI1. Cows were then randomly assigned to Resynch protocols starting either on day 20 (Resynch20D, n = 82) or 25 after TAI1 (Resynch25D, n = 82) with the insertion of a new P4 device and EB treatment. In both groups, P4 device was removed on day 8 after the beginning of Resynch, the same day of pregnancy diagnosis by ultrasonography. In pregnant cows there was no further action. Non-pregnant cows were treated with 0.5 mg im PGF, had a blood sample collected for serum P4 analysis and we measured and recorded the size of the largest follicle and the presence or absence of a corpus luteum (CL). One day later, cows were treated with 0.1 mg im LEC and TAI2 occurred 12-14 h later. The diameter of the largest follicle and serum P4 were compared between groups by ANOVA for the main effects of treatment, presence of a CL, and their interaction, whereas pregnancy per artificial insemination (P/AI) and the percentage of cows with a CL on the day of ultrasonography were analyzed using the Chi-square test. Follicle diameter on day 8 of Resynch was greater for cows in the Resynch20D group compared with Resynch25D (15.9 ± 3.9 vs 12.2 ± 2.5 mm, respectively; P = 0.046). The Resynch25D group had a greater percentage of cows with a CL (51.9 vs 18.9%, respectively; P = 0.0008) and higher serum P4 (2.8 ± 1.1 vs 1.7 ± 0.8 ng/mL; P = 0.041) at the end of the protocol compared with Resynch20D. P/AI at TAI1 was 35.4 and 36.6% (P > 0.10) for cows enrolled in Resynch20D and Resynch25D groups, respectively. P/AI to TAI2, after Resynch protocols, was greater in Resynch25D than Resynch20D (44.2 vs 22.6%, respectively; P < 0.05). In conclusion, starting an early resynchronization protocol 25 days after TAI increases P/AI compared with starting 20 days after TAI, and this was associated with a presumed greater proportion of cows with a functional CL at the moment of P4 device removal.

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

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Interleukin (IL) 4 expression was significantly altered during the postpartum period.

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IL8 and IL15 were the most significantly induced during the postpartum period.

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Correlation between increased BHB levels and induction of proinflammatory cytokines.

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Interleukins analyzed were differentially regulated during follicular development.

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ILs induced during the post-partum period were also induced 24 h post-hCG injection.

The postpartum period in dairy cows is associated with a state of temporary negative energy balance and could induce functional changes into ovarian granulosa cells (GC) resulting in significant impact on the ovarian function and fertility. Yet, the regulation of interleukin receptors (ILRs) in GC as well as ILs expression profile during the postpartum period have not been fully investigated. We hypothesized that the postpartum period is associated with changes in ILs expression profile that could affect follicular development and ovulation rate. First, we aimed to investigate the expression and regulation of different IL and IL receptors in GC at different stages of follicular development and then analyse the changes in target ILs expression profile induced during the postpartum period. In the first objective, normal cycling cows were selected and GC were collected from small follicles (SF), dominant follicles at day 5 of the estrous cycle (DF), and ovulatory follicles, 24 h following hCG injection (OF). In the second objective, dairy cows between 50 and 70 days postpartum were randomly selected, and β-hydroxybutyrate (BHB) concentrations were measured in blood samples in order to assign cows to the BHB⁺ group (>1.4 mmol/L) or BHB⁻ group (<1.2 mmol/L). GC were collected from preovulatory follicles by transvaginal aspiration. Total RNA was extracted from GC of all groups for analysis of target ILs and ILRs expression. Steady-state mRNA levels of IL4R was strongest in the DF, while IL15R expression was greatest in the OF, and IL21R showed increased steady-state mRNA levels in the corpus luteum as compared to the different groups of follicles. Overall, expression of IL1A, IL1B, IL8, IL15, IL23 and TNFα was stronger in OF as compared to DF, while IL4 and IL10 expression was stronger in SF than in DF. Similarly, expression of IL1A, IL1B, IL8, IL15, IL23, and TNFα were significantly stronger in GC of BHB⁺ cows than in the control, while IL4 expression was significantly reduced in BHB⁺ as compared to control cows. We have established an IL expression profile, which suggest a correlation with BHB levels during the postpartum period. Additionally, we have demonstrated a differential regulation of target ILRs in GC at different stages of follicular development. Overall, these data provide a better understanding of the changes that could affect follicular development and ovulation during the postpartum period and lay the ground for further investigations.

Steroidogenic, Metabolic, and Immunological Markers in Dairy Cows Diagnosed With Cystic Ovarian Follicles at Early and Mid-Late Lactation

The etiology of cystic ovarian follicles (COF) remains a conundrum with steroidogenic, immunological, and metabolic dysfunctions linked to its development. Studies suggest that COF development may occur as a result of disruption of the insulin signaling pathway and the severity of a negative energy balance in dairy cows, but mid to late lactation cows diagnosed with COF are unlikely to have issues with energy metabolism. Herein, we characterized the mRNA expression of steroidogenic (LHCGR, StAR, CYP11A1, 3β-HSD, CYP19A), immunological (IL-1β, IL-6, IL-8, TLR-4, TNF), and metabolic markers (IGF-1, IRS1) in follicular fluid; and plasma and follicular fluid levels of E2, IL-1β, glucose, and NEFA in early and mid-late lactation COF cows. Lactating dairy cows were diagnosed as having COF (n = 11, follicle >20 mm persistent for 7 days, absence of corpus luteum, and flaccid uterus) while 11 herdmates cycling with a dominant follicle were classified as the control cows. Cows diagnosed with COF were classified as early lactation (COF-E, n = 5) cows, <35 days in milk (DIM); or mid-late lactation (COF-M/L, n = 6), ≥118 DIM cows. Results revealed that mRNA expression StAR was greater (P < 0.01) in COF-E cows than COF-M/L cows and the control cows. The mRNA expression CYP19A1 was lower (P < 0.01) in COF-E cows and COF-M/L cows than in the control cows. The mRNA expression IL-6 and IRS-1 tended to be greater and lower, respectively, in COF-M/L cows compared to the control cows. The mRNA expression IGF-1 was greater (P < 0.01) in COF-E and COF-M/L cows than in the control cows. The plasma and follicular fluid concentration of NEFA was greater (P < 0.05) in COF-E cows than in COF-M/L and the control cows. Cows with COF-E had disturbances in steroidogenic and metabolic markers, while cows with COF-M/L had steroidogenic, immunological, and metabolic dysregulations, suggesting that COF pathogenesis may vary between early and mid-late lactation dairy cows.

Follicular structures of cows with cystic ovarian disease present altered expression of cytokines

Ovulation is considered an inflammatory, cytokine-mediated event. Cytokines, which are recognized as growth factors with immunoregulatory properties, are involved in many cellular processes at the ovarian level. In this sense, cytokines affect fertility and are involved in the development of different ovarian disorders such as bovine cystic ovarian disease (COD). Because it has been previously demonstrated that ovarian cells represent both sources and targets of cytokines, the aim of this study was to examine the expression of several cytokines, including IL-1β, IL-1RA, IL-1RI, IL-1RII, IL-4 and IL-8, in ovarian follicular structures from cows with spontaneous COD. The protein expression of these cytokines was evaluated by immunohistochemistry. Additionally, IL-1β, IL-4 and IL-8 concentrations in follicular fluid (FF) and serum were determined by enzyme-linked immunosorbent assay (ELISA). In granulosa and theca cells, IL-1RI, IL-1RII, IL-1RA and IL-4 expression levels were higher in cystic follicles than in the control dominant follicles. The serum and FF concentrations of IL-1β and IL-4 showed no differences between groups, whereas IL-8 concentration was detected only in FF of cysts from cows with COD. The FF and serum concentrations of IL-1β and IL-8 showed no significant differences, whereas IL-4 concentration was higher in FF than in serum in both the control and COD groups. These results evidenced an altered expression of cytokines in ovaries of cows with COD that could contribute to the pathogenesis of this disease.

Hemodynamic changes detected by Doppler ultrasonography in the ovaries of cattle during early development of cystic ovarian disease

A common reproductive disease in dairy cattle is Cystic Ovarian Disease. To study its development, there was use of an experimental model of follicular persistence to detect hemodynamic changes occurring in ovaries by using Doppler ultrasonography. After estrous synchronization, control cows received no additional treatment and were evaluated at proestrus (CG), whereas treated cows (PG) received sub-luteal doses of progesterone for 15 days and were evaluated at proestrus, and after 0, 5, 10 and 15 days of follicular persistence. Spectral Doppler was used to evaluate blood flow in the ovarian artery, and power Doppler for evaluation of blood flow in the ovarian parenchyma and follicular wall of persistent and dominant preovulatory follicles. Findings using power Doppler signals indicated there were no differences between groups in the parenchyma of both right (P =  0.455) and left (P =  0.762) ovaries. In contrast, power Doppler signals of blood flow were less in walls of persistent follicles from day 0 to 15 when there was follicular persistence than in dominant follicles of the CG (P <  0.001). Blood flow in ovarian arteries was less (P <  0.05) in diastolic velocity and time averaged maximum velocity in all PG groups than in the CG. Peak systolic velocity was less (P <  0.05) in all PG than in the CG, with the exception of P15 (P >  0.05). These findings indicate there are marked changes in blood irrigation area of walls of persistent follicles during the 15 days of follicular persistence.

Association of RBP-4 gene polymorphisms with follicular cysts in large white sows

Follicular cysts, which is a common infertility disease, can cause financial losses in pig breeding programmes. The pathogenesis and mechanisms of the formation of follicular cysts are not understood clearly. In our previous study, the concentration of retinol-binding protein 4 (RBP-4) in the follicular fluid (FF) of the ovary with follicular cysts was found to be significantly higher than that of normal ovary, thereby suggesting that RBP-4 may be a candidate biomarker for porcine follicular cysts. To study the association of RBP-4 and follicular cysts further, we detected the polymorphisms of the RBP-4 gene and the presence of follicular cysts by PCR-Restriction fragment length polymorphism (RFLP) assay. In this study, we screened the mutations of RBP-4 gene in 79 sows with follicular cysts and 100 normal sows without cysts. Results showed that +249-63G>C polymorphisms were significantly associated with follicular cysts, and sows with CC genotype in RBP-4 gene had a high risk of developing follicular cysts. Hence, our findings further proved that RBP-4 may be a novel biomarker for follicular cysts, which may be valuable for the diagnosis of follicular cysts and molecular breeding of pigs.

Perturbations in Lineage Specification of Granulosa and Theca Cells May Alter Corpus Luteum Formation and Function

Anovulation is a major cause of infertility, and it is the major leading reproductive disorder in mammalian females. Without ovulation, an oocyte is not released from the ovarian follicle to be fertilized and a corpus luteum is not formed. The corpus luteum formed from the luteinized somatic follicular cells following ovulation, vasculature cells, and immune cells is critical for progesterone production and maintenance of pregnancy. Follicular theca cells differentiate into small luteal cells (SLCs) that produce progesterone in response to luteinizing hormone (LH), and granulosa cells luteinize to become large luteal cells (LLCs) that have a high rate of basal production of progesterone. The formation and function of the corpus luteum rely on the appropriate proliferation and differentiation of both granulosa and theca cells. If any aspect of granulosa or theca cell luteinization is perturbed, then the resulting luteal cell populations (SLC, LLC, vascular, and immune cells) may be reduced and compromise progesterone production. Thus, many factors that affect the differentiation/lineage of the somatic cells and their gene expression profiles can alter the ability of a corpus luteum to produce the progesterone critical for pregnancy. Our laboratory has identified genes that are enriched in somatic follicular cells and luteal cells through gene expression microarray. This work was the first to compare the gene expression profiles of the four somatic cell types involved in the follicle-to-luteal transition and to support previous immunofluorescence data indicating theca cells differentiate into SLCs while granulosa cells become LLCs. Using these data and incorporating knowledge about the ways in which luteinization can go awry, we can extrapolate the impact that alterations in the theca and granulosa cell gene expression profiles and lineages could have on the formation and function of the corpus luteum. While interactions with other cell types such as vascular and immune cells are critical for appropriate corpus luteum function, we are restricting this review to focus on granulosa, theca, and luteal cells and how perturbations such as androgen excess and inflammation may affect their function and fertility.

The presence of two ovulatory follicles at timed artificial insemination influences the ovulatory response to GnRH in high-producing dairy cows

This study sought to examine the impact of the presence of two co-dominant (ovulatory) follicles at the time of artificial insemination (AI) on the ovulatory response to GnRH given in a fixed-time AI protocol. The study population comprised 622 lactating dairy cows: 306 (49.2%) with a single follicle, 198 (31.8%) with two bilateral follicles (one follicle per ovary) and 118 (19%) with two unilateral follicles (same ovary). Based on odds ratios, cows with two bilateral or unilateral follicles were less likely (by factors of 0.09 and 0.11, respectively) to undergo ovulation failure compared with cows with one follicle (P = 0.01 and P = 0.02, respectively); the likelihood of ovulation failure decreased 0.75 times with every one-mm increase in follicle diameter for cows with a single follicle, whereas individual follicle diameter was not related to ovulation failure in cows with two bilateral follicles (P = 0.001). The likelihood of double ovulation decreased 0.7 times with every one-mm diameter difference between the larger and smaller follicle for all cows with two follicles (P = 0.001), whereas cows with two unilateral follicles showed a higher (P < 0.05) double ovulation rate than cows with two bilateral follicles. In 116 (58.6%) of the cows with two bilateral follicles, only the larger follicle ovulated in 59.5% cows, whereas only the smaller one ovulated in the remaining 40.5% cows. In these cows, a one-mm size difference between the larger and the smaller follicle gave rise to a 1.12-fold increase in the ovulation failure rate for the larger follicles (P = 0.0001). Cows with two bilateral follicles were more likely (by a factor of 1.5) to conceive than cows with one follicle (P = 0.001). Significant right-left differences were not found in cows with two bilateral follicles, whereas the right ovary was more active than the left in the remaining cows. Our results indicate that cows with two co-dominant follicles at AI show different ovulation patterns to those with one dominant follicle. A higher rate of ovulation failure was observed among cows with one follicle than cows with two follicles, whereas the conception rate was higher for cows with two bilateral follicles than for the remaining cows. In cows with two follicles, double ovulations along with ovulation of the smaller follicle were related to the least size difference between the larger and smaller follicle.