Dominant bovine ovarian follicular cysts express increased levels of messenger RNAs for luteinizing hormone receptor and 3 beta-hydroxysteroid dehydrogenase delta(4),delta(5) isomerase compared to normal dominant follicles

Association of Metabolic and Endocrine Disorders with Bovine Ovarian Follicular Cysts

After estrus, when mature follicles fail to ovulate, they may further develop to form follicular cysts, affecting the normal function of ovaries, reducing the reproductive efficiency of dairy cows and causing economic losses to cattle farms. However, the key points of ovarian follicular cysts pathogenesis remain largely unclear. The purpose of the current research was to analyze the formation mechanism of ovarian follicular cysts from hormone and gene expression profiles. The concentrations of progesterone (P4), estradiol (E2), insulin, insulin-like growth factor 1 (IGF1), leptin, adrenocorticotropic hormone (ACTH) and ghrelin in follicle fluid from bovine follicular cysts and normal follicles were examined using enzyme-linked immunosorbent assay (ELISA) or 125I-labeled radioimmunoassay (RIA); the corresponding receptors' expression of theca interna cells was tested via quantitative reverse transcription polymerase chain reaction (RT-qPCR), and the mRNA expression profiling was analyzed via RNA sequencing (RNA-seq). The results showed that the follicular cysts were characterized by significant lower E2, insulin, IGF1 and leptin levels but elevated ACTH and ghrelin levels compared with normal follicles (p < 0.05). The mRNA expressions of corresponding receptors, PGR, ESR1, ESR2, IGF1R, LEPR, IGFBP6 and GHSR, were similarly altered significantly (p < 0.05). RNA-seq identified 2514 differential expressed genes between normal follicles and follicular cysts. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis linked the ovarian steroidogenesis pathway, especially the STAR, 3β-HSD, CYP11A1 and CYP17A1 genes, to the formation of follicular cysts (p < 0.01). These results indicated that hormone metabolic disorders and abnormal expression levels of hormone synthesis pathway genes are associated with the formation of bovine ovarian follicular cysts.

Estrogens receptors, nuclear coactivator 1 and ligand-dependent corepressor expression are altered early during induced ovarian follicular persistence in dairy cattle

Failure of ovulation can lead to follicular persistence, one of the main components of the pathogenesis of cystic ovarian disease (COD) in dairy cattle. Follicular persistence causes the permanence of a functional follicular structure in the ovary, which alters the cyclicity of the female and causes infertility. The aim of the present study was to evaluate the expression of estrogen receptors (ESR) 1 and 2, and the coregulatory proteins NCOA1, NRIP1 and LCOR by immunohistochemistry, in antral and preovulatory/persistent follicles in a model of follicular persistence induced by low levels of progesterone, to detect incipient changes during COD development, on the expected day of ovulation (P0) and after 5 (P5), 10 (P10) and 15 (P15) days of follicular persistence. Twenty-five Holstein cows were used, which were distributed in 5 groups: control group (n = 5), group P0 (n = 5), group P5 (n = 5), group P10 (n = 5), group P15 (n = 5). ESR1 expression was lower in antral follicles of the P5 (theca), P10 and P15 (theca and granulosa) groups relative to the control group (p < 0.05), and also lower in granulosa cells of persistent follicles of the P5, P10 and P15 groups than in dominant follicles of the control group (p < 0.05), without differences in theca cells. ESR2 expression showed no differences between groups. The ESR1:ESR2 balance favored ESR2 expression along the development of persistent follicles, as from 5 days of persistence (p < 0.05). NCOA1 expression was higher in granulosa cells of both antral and persistent follicles from the P0 group relative to the P5 and P10 groups, but showed no differences with the control and P15 groups (p < 0.05). Theca cells of antral and persistent follicles showed higher expression in the P0 and P15 groups in relation to the control, P5 and P10 groups (p < 0.05). No differences were detected for NRIP1 in antral, dominant and persistent follicles between groups. LCOR expression showed a decrease in granulosa cells of antral follicles from all persistence groups relative to the control group (p < 0.05). In theca cells, antral follicles of the P10 group showed lower LCOR expression than the control group (p < 0.05). LCOR expression was similar for dominant and persistent follicles. Considering that the ESR1:ESR2 balance favored ESR2 expression along the development of persistent follicles, as well as the decreased LCOR and NCOA1 expression, we may assume that, at the early stages of persistence, there is a negative regulation of ESR transcription. This coincides with the effects of estrogens through ESR on proliferation and apoptosis among other processes that favor follicular persistence. The results obtained provide relevant information in the knowledge of local events during the development of follicular persistence that could explain the failures in the reversion of the disease through hormonal treatments and the high recurrence rates reported for COD. In addition, it contributes to the study and identification of possible therapeutic targets, for the design of new treatments.

Contribution of key elements of nutritional metabolism to the development of cystic ovarian disease in dairy cattle

The alteration of signaling molecules involved in the general metabolism of animals can negatively influence reproduction. In dairy cattle, the development of follicular cysts and the subsequent appearance of ovarian cystic disease (COD) often lead to decreased reproductive efficiency in the herd. The objective of this review is to summarize the contribution of relevant metabolic and nutritional sensors to the development of COD in dairy cows. In particular, we focus on the study of alterations of the insulin signaling pathway, adiponectin, and other sensors and metabolites relevant to ovarian functionality, which may be related to the development of follicular persistence and follicular formation of cysts in dairy cattle. The results of these studies support the hypothesis that systemic factors could alter the local scenario in the follicle, generating an adverse microenvironment for the resumption of ovarian activity and possibly leading to the persistence of follicles and to the development and recurrence of COD.

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.

ACTH administration during formation of preovulatory follicles impairs steroidogenesis and angiogenesis in association with ovulation failure in lactating cows

Ovulation failure, follicular persistence, and formation of follicular cysts are known to impair dairy cow fertility. Although the underlying mechanism is not entirely clear, stress-induced alteration in adrenal hormone secretion can cause these ovarian pathologies. Six synchronized lactating cows were scanned daily by ultrasound, and plasma samples were taken throughout the estrous cycle. Treatment cows (n = 3) were administered with ACTH analog every 12 h from day 15 to day 21 of the cycle to induce formation of follicular cysts. Ovaries were collected at the slaughterhouse on day 23 of the cycle before appearance of follicular pathologies. Control cows (n = 3) were administered placebo, resynchronized, and administered PGF2α on day 6 of the new cycle to induce development of a preovulatory follicle. Follicular fluid was aspirated from the preovulatory follicles of each group to determine their steroid milieu. Slices were taken from the follicular wall for total messenger (m) RNA isolation and semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Administration of ACTH increased (P < 0.02) plasma cortisol concentration and reduced (P < 0.01) milk production. Androstenedione and estradiol concentrations in the follicular fluids were lower (P < 0.05) in ACTH-treated follicles than those in controls. The mRNA expression of luteinizing hormone receptor, 3β-hydroxysteroid dehydrogenase, cytochrome P450 aromatase (P450arom), and cytochrome P450 17α-hydroxylase (P450c17) were lower (P < 0.02) in the ACTH-treated vs control cows. On the other hand, the expression of steroidogenic acute regulatory protein and cytochrome P450 side-chain cleavage did not differ between groups. In addition, mRNA expression of vascular endothelial growth factor (VEGF)120 and VEGF164 was higher (P < 0.01) in control than in ACTH-treated follicles, but that for angiopoietin-1 and 2 did not differ between groups. Findings indicated that ACTH administration throughout preovulatory follicle development alters follicular steroidogenesis in association with impaired angiogenesis. Such alterations might explain, in part, the mechanism underlying ovulation failure and the formation of persistent or cystic follicles under stress.

Molecular aspects of bovine cystic ovarian disease pathogenesis

Cystic ovarian disease (COD) is one of the main causes of reproductive failure in cattle and causes severe economic loss to the dairy farm industry because it increases both days open in the post partum period and replacement rates due to infertility. This disease is the consequence of the failure of a mature follicle to ovulate at the time of ovulation in the estrous cycle. This review examines the evidence for the role of altered steroid and gonadotropin signaling systems and the proliferation/apoptosis balance in the ovary with cystic structures. This evidence suggests that changes in the expression of ovarian molecular components associated with these cellular mechanisms could play a fundamental role in the pathogenesis of COD. The evidence also shows that gonadotropin receptor expression in bovine cystic follicles is altered, which suggests that changes in the signaling system of gonadotropins could play a fundamental role in the pathogenesis of conditions characterized by altered ovulation, such as COD. Ovaries from animals with COD exhibit a disrupted steroid receptor pattern with modifications in the expression of coregulatory proteins. These changes in the pathways of endocrine action would trigger the changes in proliferation and apoptosis underlying the aberrant persistence of follicular cysts.

Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R251/suppl/DC1.

Effect in dedicator of cytokinesis 6 (DOCK6) on steroid production in theca cells of follicular cysts

Ovarian follicular cysts are one of the most common causes of reproductive failure in mammals. A comparative gene expression approach may aid in elucidating the causes of ovarian cyst disease. In the present study, the differential display technique was used to identify mRNA sequences that accumulate preferentially in theca cells of bovine cystic follicles. Dedicator of cytokinesis 6 (Dock6) expression was observed in the theca cells of cystic follicles. Small interfering RNA (siRNA) knockdown of Dock6 increased progesterone (P4) production and StAR expression in theca cells of high-estrogen follicular cysts, but did not affect androstenedione (A4) production. We propose that Dock6 may be a marker associated with the development of follicular cysts. Additionally, Dock6 may be involved in the development of cystic follicles by suppressing P4 production rather than increasing A4 production in theca cells.

mRNA expression pattern of gonadotropin receptors in bovine follicular cysts

Follicular growth and steroidogenesis are dependent on gonadotropin binding to their receptors in granulosa and theca cells of ovarian follicles. The aim of the present study was to evaluate the expression patterns of follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHCGR) in ovarian follicular structures from cows with cystic ovarian disease (COD) as compared with those of regularly cycling cows. Relative real-time RT-PCR analysis showed that the expression of FSHR mRNA in granulosa cells was highest in small antral follicles, then decreased significantly as follicles increased in size, and was lowest in cysts. FSHR mRNA was not detected in the theca cells of any follicular category, including cysts. LHCGR mRNA expression in granulosa cells was significantly higher in large antral follicles than in cysts, and not detected in granulosa cells of small and medium antral follicles. In theca cells, the expression level of LHCGR mRNA in medium antral follicles was higher than in small and large antral follicles, whereas that in follicular cysts it was similar to those in small and medium antral follicles, but higher than that in large antral follicles. Our findings provide evidence that there is an altered gonadotropin receptor expression in bovine cystic follicles, and suggest that in conditions characterized by altered ovulation, such as COD, changes in the signaling system of gonadotropins may play a fundamental role in their pathogenesis.

Macroscopic and histological characteristics of fluid-filled ovarian structures in dairy cows

The primary objective of this study was to use macroscopic and histological features of corpora lutea with a cavity and anovulatory cystic ovarian structures, present in 90 pairs of abattoir-derived dairy cow ovaries, as the basis to clarify the nomenclature of ovarian structures. Excluding morphologically normal ovarian fol-licles (antrum < 2 cm, wall < 1 mm), there were 27 fluid-filled ovarian structures. Ovulatory structures > 16 mm in diameter were designated as Group A (cavity ≤ 10 mm and wall > 10 mm) or Group B (cavity > 10 mm and wall < 10 mm). The volume of luteal tissue was less (P < 0.05) in Group B than in Group A, whereas that of a solid corpus luteum (CL) was intermediate (least square means ± SEM: 72 ± 1.92, 11.22 ± 1.57 and 5.84 ± 1.92 cm3, respectively). There was a greater proportion (P < 0.05) of small luteal cells in Group B compared to a solid CL, whereas Group A was intermediate (58.6 ± 5.3, 37.4 ± 5.3 and 44.0 ± 4.4%, respectively). Connective tissue was thicker (P < 0.05) in Group B than in Group A (295.4 ± 46.9 vs. 153.9 ± 38.2 μm). Based on the above-mentioned characteristics and differences, Groups A and B were designated as a CL with a cavity and a cystic CL, respectively. Furthermore, there were three groups of anovulatory ovarian structures. Structures in Group C were termed persistent/anovulatory follicles (overall diameter and wall thickness ≤ 20 and 1-3 mm, respectively). Finally, Groups D and E were designated as a follicle-fibrous cyst and a follicle-luteinised cyst (based on histological structure) for anovulatory structures with an overall diameter and wall thickness of ≥ 20 and ≤ 3 mm, and ≥ 20 and ≥ 3 mm, respectively.

Ovarian localization of 11β-hydroxysteroid dehydrogenase (11βHSD): effects of ACTH stimulation and its relationship with bovine cystic ovarian disease

Cystic ovarian disease (COD) is an important cause of infertility in cattle, and ACTH has been involved in regulatory mechanisms related to ovarian function associated with ovulation, steroidogenesis, and luteal function. Here, we examined the localization of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and 11βHSD2 proteins in the ovary of healthy cows and animals with spontaneous and ACTH-induced COD and the in vitro response of the follicular wall exposed to ACTH. After stimulation by ACTH, we documented changes in 11βHSD expression and cortisol secretion by the follicular wall of large antral and follicular cysts. Follicular cysts showed a higher constitutive expression of both enzymes, whereas ACTH induced an increase in 11βHSD1 in tertiary follicles and follicular cysts and a decrease in 11βHSD2 in follicular cysts. Moderate expression of 11βHSD1 was observed by immunohistochemistry in granulosa of control animals, with an increase (P < 0.05) from primary to secondary, tertiary, and atretic follicles. The level of immunostaining in theca interna was lower than that in granulosa. The expression of 11βHSD2 was lower in the granulosa of primary follicles than in that of secondary, tertiary, and atretic follicles and was lower in the theca interna than in the granulosa. In ACTH-induced and spontaneously occurring follicular cysts, differences from controls were observed only in the expression of 11βHSD1 in the granulosa, being higher (P < 0.05) than in tertiary follicles. These findings indicate that follicular cysts may be exposed to high local concentrations of active glucocorticoids and indicate a local role for cortisol in COD pathogenesis and in regulatory mechanisms of ovarian function.

Alteration in localization of steroid hormone receptors and coregulatory proteins in follicles from cows with induced ovarian follicular cysts

Cystic ovarian disease (COD) is an important cause of infertility in cattle. The altered follicular dynamics and cellular differentiation observed in COD may be mediated through a disruption of the expression of steroid receptors and their associated transcriptional cofactors. The aim of this study was to determine the protein expression profiles of ESR1, ESR2, PGR, AR, NCOA3, NCOR2, and PHB2 (REA) in ovarian follicles in an experimental model of COD induced by the administration of ACTH. Ovaries were collected and follicles were dissected from heifers during the follicular phase (control) or from heifers treated with ACTH to induce the formation of ovarian follicular cysts. Ovaries were fixed, sectioned, and stained immunohistochemically for steroid receptors and the associated transcription factors. The relative expression of ESR1 was similar in follicular cysts and in tertiary follicles from both control and cystic cows and was significantly higher than in secondary follicles. The expression of ESR2 in the granulosa was higher in cystic follicles. No differences were seen for PGR. The expression of androgen receptor was significantly increased in tertiary follicles with lower immunostaining in cysts. The expression of NCOA3 was observed in the granulosa and theca with a significantly increased expression in the theca interna of cystic follicles. The highest levels of NCOR2 expression in granulosa, theca interna, and theca externa were observed in cysts. In granulosa cells, NCOR2 levels increase progressively as follicles mature and the treatment had no effect. In summary, ovaries from animals with induced COD exhibited altered steroid receptor expression compared with normal animals, as well as changes in the expression of their regulators. It is reasonable to suggest that in conditions characterized by altered ovulation and follicular persistence, such as COD, changes in the intra-ovarian expression of these proteins could play a role in their pathogenesis.

Endocrine milieu and developmental dynamics of ovarian cysts and persistent follicles in postpartum dairy cows

Ovarian follicular cysts and persistent follicles are follicular pathologies involved in reduced fertility of dairy cows. Two separate experiments were performed on high-yielding Holstein cows to characterize ovarian cyclicity and evaluate the developmental dynamics of follicle pathologies postpartum. In experiment 1, 58 cows were monitored by ultrasonography twice weekly from d 18±1 to 69±2 postpartum. First ovulation occurred 38±3, 27±2, 20±1, and 25±3 d postpartum in cows with 1 cycle (n=11), 2 cycles (n=21), 3 cycles (n=13), and 4 cycles (n=7), respectively. Follicular pathologies were developed in cows that were either acyclic (n=6) or had 1 or 2 cycles, but not in cows with more than 2 cycles. In experiment 2, 47 cows were monitored twice weekly from 10 d postpartum to second ovulation. Follicles ≥17 mm in diameter in 2 consecutive scans were aspirated, and concentrations of various hormones were measured. Cows were defined as cyclic (n=30; 64%) or with the potential to develop follicular pathology (n=17; 36%). Aspirated follicles (n=27) were classified into 3 main groups based on follicular growth rate, follicular diameter, and ovarian activity before and after follicular aspiration. Dominant follicles (n=4) were defined as large follicles (20 mm in diameter) with growth rate ≤1 mm/d and normal ovarian activity. Persistent follicles (n=6) had the same growth rate and diameter as the dominant follicles, but persisted at the same diameter for ≥10 d. Ovarian cysts (n=17) were defined as the largest follicular structures (19 to 32 mm in diameter), with abnormal growth rate (>1 mm/d) and abnormal ovarian activity. Single or turnover cysts did not differ in their growth parameters and were therefore combined and further classified according to follicular-fluid hormone concentrations. Estradiol-dominant cysts (n=7) were characterized by normal estradiol (284 to 659 ng/mL) and progesterone (20 to 113 ng/mL) concentrations, similar to those of the dominant follicle (554 to 993 ng/mL and 44 to 106 ng/mL, respectively). Progesterone-dominant cysts (n=5) were characterized by low estradiol (0.06 to 330 ng/mL) and high progesterone (586 to 3,288 ng/mL) concentrations. Low-steroidogenic active cysts (n=5) were characterized by low concentrations of both estradiol (23 to 61 ng/mL) and progesterone (17 to 205 ng/mL). Characterization of spontaneously forming cysts might enable definition of the formation of ovarian follicular pathologies in postpartum cows.

New insights into the pathogenesis of cystic follicles in cattle: microarray analysis of gene expression in granulosa cells

Ovarian follicular growth and development are regulated by extraovarian and intraovarian factors, which influence granulosa cell proliferation and differentiation. However, the molecular mechanisms that drive follicular growth are not completely understood. Ovarian follicular cysts are one of the most common causes of reproductive failure in dairy cattle. Nevertheless, the primary cause of cyst formation has not been clearly established. A gene expression comparison may aid in elucidating the causes of ovarian cyst disease. Our objective was to identify differentially expressed genes in ovarian granulosa cells between normal dominant and cystic follicles of cattle. Granulosa cells and follicular fluid were isolated from dominant and cystic follicles collected via either ultrasound-guided aspiration from dairy cows (n = 24) or slaughterhouse ovaries from beef cows (n = 23). Hormonal analysis for progesterone, estradiol, and androstenedione in follicular fluid was performed by RIA. Total RNA was extracted and hybridized to 6 Affymetrix GeneChip Bovine Genome Arrays (Affymetrix, Santa Clara, CA). Abundance of mRNA for differentially expressed selected genes was determined through quantitative real-time reverse-transcription PCR. Follicular cysts showed greater (P < 0.05) progesterone, lesser (P < 0.05) estradiol, and no differences (P > 0.10) in androstenedione concentrations compared with noncystic follicles. A total of 163 gene sequences were differentially expressed (P < 0.01), with 19 upregulated and 144 downregulated. From selected target genes, quantitative real-time reverse-transcription PCR confirmed angiogenin, PGE(2) receptor 4, and G-protein coupled receptor 34 genes as upregulated in cystic follicles, and Indian hedgehog protein precursor and secreted frizzled-related protein 4 genes as downregulated in cystic follicles. Further research is required to elucidate the role of these factors in follicular development and cyst formation.

Follicular persistence induced by adrenocorticotropic hormone administration in goats

The objective of the present study was to examine the effect of adrenocorticotropic hormone (ACTH) administration on the induction of persistent cystic follicle in the goat in order to establish a method to experimentally induce cystic follicle. Four cross-bred goats were intramuscularly administered ACTH at 0.78 and 6.25 µg/10 kg twice a day from Days 15 to 21 (Day 0 was defined as the day of last estrus). Follicular status in the ovary was monitored by ultrasound examination. The plasma concentrations of estradiol, progesterone and cortisol were measured. Treatment with ACTH at the 0.78 and 6.25 µg/10 kg levels caused persistent follicles (> 10 days delay from the expected ovulation date) in 50% of the goats in both treatment groups. In those animals, ovulation occurred 17 and 27 days and 11 and 12 days after the expected days in the 0.78 and 6.25 µg/10 kg groups, respectively. The maximum follicle diameters were 10 and 9 mm in the 0.78 and 6.25 µg/10 kg ACTH groups, respectively. In the control group, the estradiol concentration increased on Day 18 and remained at a high level for a few days. However, such an increase was not seen in both ACTH groups. The estradiol concentration increased gradually from Days 21 to 27 in the 6.25 µg/10 kg ACTH group. These results suggest the possibility that ACTH induces persistent follicles in goats, which may be related to the delay of the onset of estradiol secretion followed by its maintenance at a high concentration.

Identification of differentially expressed genes in bovine follicular cystic ovaries

Follicular cystic ovary (FCO) is one of the most frequently diagnosed ovarian diseases and is a major cause of reproductive failure in mammalian species. However, the mechanism by which FCO is induced remains unclear. Genetic alterations which affect the functioning of many kinds of cells and/or tissues could be present in cystic ovaries. In this study, we performed a comparison analysis of gene expression in order to identify new molecules useful in discrimination of bovine FCO with follicular cystic follicles (FCFs). Normal follicles and FCFs were classified based on their sizes (5 to 10 mm and ≥25 mm). These follicles had granulosa cell layer and theca interna and the hormone 17β-estradiol (E(2))/ progesterone (P(4)) ratio in follicles was greater than one. Perifollicular regions including follicles were used for the preparation of RNA or protein. Differentially expressed genes (DEG) that showed greater than a 2-fold change in expression were screened by the annealing control primer (ACP)-based PCR method using GeneFishing™ DEG kits in bovine normal follicles and FCFs. We identified two DEGs in the FCFs: ribosomal protein L15 (RPL15) and microtubule-associated protein 1B (MAP1B) based on BLAST searches of the NCBI GenBank. Consistent with the ACP analysis, semi-quantitative PCR data and Western blot analyses revealed an up-regulation of RPL15 and a down-regulation of MAP1B in FCFs. These results suggest that RPL15 and MAP1B may be involved in the regulation of pathological processes in bovine FCOs and may help to establish a bovine gene data-base for the discrimination of FCOs from normal ovaries.

Reactive oxygen species (ROS): involvement in bovine follicular cysts etiopathogenesis

Ovulation is compared to an acute inflammatory process during which vasoactive agents, prostanoids, leukotrienes and Reactive Oxygen Species (ROS) develop. The aim of this study was to evaluate the levels of ROS in cystic and follicular fluid, in order to establish their involvement in the etiopathogenesis of Cystic Ovarian Follicle (COF) in dairy cows. The study was conducted in 30 healthy cows (group C) and 30 cows affected by COF (group COF). The fluid of follicular cysts and of preovulatory follicles was drawn by means of ultrasound guided aspiration from the cows of both groups. The fluid obtained was analyzed by a photometric analytical system to detect ROS level. ROS concentration was statistically lower in the cystic fluid than in the follicular one (62.4 +/- 13.36 U.Carr vs. 84.89 +/- 26.99 U.Carr) (p<0.05), thus suggesting that an alteration of the cascade responsible for ROS production may be implicated in the complex etipathogenesis of COF.

Heat shock protein 70 and sex steroid receptors in the follicular structures of induced ovarian cysts

The purpose of this study was to estimate the expression and relative amounts of estrogen (ER) and progesterone receptors (PR) and their isoforms as well as heat shock protein 70 (HSP70) in ovaries of rats with induced cystic ovarian disease (COD). Primary, secondary, tertiary, atretic and cystic follicles were evaluated by immunohistochemistry and total ovarian proteins were analyzed by Western blot. In the granulosa layer, growing and cystic follicles in the treated group have a higher expression of ERalpha than growing follicles of control individuals. In the theca interna layer, tertiary follicles presented a significantly higher expression of ERalpha in the treated group. An increase in total ERalpha protein was detected in the treated group. Granulosa cells of all growing, atretic and cystic follicles show a lower expression of ERbeta in animals with COD, and the total protein expression of ERbeta was lower in this group. The expression of PR was lower in the granulosa cell layer of tertiary and cystic follicles in treated animals, and theca interna layer had less intense immunostaining in this group. Although there were no differences in the expression of PR-B by Western blotting, the expression of PR-A was higher and the expression of PR-C was smaller in the treated group. An intense HSP70 immunostaining was observed in the cells of cystic follicles. By Western blotting, higher protein expression of HSP70 was detected in the ovarian samples of the control group than those of the treated ones. Ovaries of animals with COD exhibited an altered steroid receptor expression and subtype balance as compared with control animals, and an increase in HSP70 immunoexpression.

Insulin-like growth factor I in sera, ovarian follicles and follicular fluid of cows with spontaneous or induced cystic ovarian disease

The objective of this research was to determine changes in IGF-I levels in serum and follicular fluid, and immunoreactivity of the follicle wall of cows with spontaneous (slaughter specimens) or ACTH-induced follicular cysts, and to compare results to normal cycling (control) cows after selection of the ovulatory follicle. Concentrations of IGF-I in serum did not differ between control and cystic animals (p=0.76). Fluid from the ovulatory follicle in control cows had 41% higher concentrations of IGF-I than that from cystic follicles collected at slaughter (spontaneous cysts; p<0.05) and 70% higher than that in induced follicular cysts (p<0.05). An intense positive immunostaining with anti-IGF-I was observed in granulosa cells (p<0.05) and in the theca interna (p<0.05) of secondary and tertiary follicles in all three groups of animals, but staining was less intense in cystic (p<0.05) and atretic follicles (p<0.05). This study provides evidence to suggest that cystic ovarian disease in cattle is associated with decreased concentrations of IGF-I in follicular fluid, but not in serum, and decreased production of IGF-I in the follicular wall. These data support the notion that IGF-I plays a role in the regulation of folliculogenesis, and may participate in the pathogenesis of cystic ovarian disease in cattle.

Intrafollicular steroids and anti-mullerian hormone during normal and cystic ovarian follicular development in the cow

Development of follicular cysts is a frequent ovarian dysfunction in cattle. Functional changes that precede cyst formation are unknown, but a role for anti-Müllerian hormone (AMH) in the development of follicular cysts has been suggested in humans. This study aimed to characterize intrafollicular steroids and AMH during follicular growth in a strain of beef cows exhibiting a high incidence of occurrence of follicular cysts. Normal follicular growth and cyst development were assessed by ovarian ultrasonography scanning during the 8 days before slaughtering. Experimental regression of cysts was followed by rapid growth of follicles that reached the size of cysts within 3-5 days. These young cysts exhibited higher intrafollicular concentrations of testosterone, estradiol-17beta, and progesterone than large early dominant follicles did in normal ovaries, but they exhibited similar concentrations of AMH. Later-stage cysts were characterized by hypertrophy of theca interna cells, high intrafollicular progesterone concentration, and high steroidogenic acute regulatory protein mRNA expression in granulosa cells. Progesterone and AMH concentrations in the largest follicles (> or =10 mm) and cysts were negatively correlated (r = -0.45, P < 0.01). Smaller follicles (<10 mm) exhibited higher intrafollicular testosterone and estradiol-17beta concentrations in ovaries with cysts compared to normal ovaries. During follicular growth, AMH concentration dropped in follicles larger than 5 mm in diameter and in a similar way in ovaries with and without cysts. In conclusion, enhanced growth and steroidogenesis in antral follicles <10 mm preceded cyst formation in cow ovaries. Intrafollicular AMH was not a marker of cystic development in the cow, but low AMH concentrations in cysts were associated with luteinization.

Involvement of Plasma Progesterone, Oestradiol-17? and Cortisol in Ovulatory Response to Gonadotropin-releasing Hormone in Dairy Cows with Cystic Follicles

The aim of the present study was to examine the plasma concentrations of progesterone, oestradiol-17beta and cortisol in the cows with cystic follicle and to examine its relationship with the ovulatory response to gonadotropin-releasing hormone (GnRH). Eighty-five post-partum Holstein-Friesian cows with cystic follicles regardless of the presence of corpus luteum were studied. Follicular size, presence of corpus luteum and occurrence of ovulation were checked by palpation per rectum. Blood collection and palpation per rectum were conducted on days 0, 7 and 14. Gonadotropin-releasing hormone was administered at day 7. Plasma concentrations of progesterone, oestradiol-17beta and cortisol were determined. Progesterone concentrations of <3.2, 3.2-4.8 and >4.8 nmol/l were defined as low, intermediate and high, respectively. Sixty-three (74.1%) of 85 cows showed low (<3.2 nmol/l =1 ng/ml) progesterone concentrations on day 0. Only 40 (47.1%) of them showed low-low pattern of progesterone at days 0 and 7. In 27 (31.8%) of them, progesterone concentration had increased by day 14. Of 22 cows having high progesterone concentration (>/=4.8 nmol/l) on day 0, corpus luteum was not detected in 18 cows (21.2%). Only in 10 cows, cystic follicle disappeared after GnRH administration. However, only one of 27 cows in which progesterone pattern was low-low-high at days 0, 7 and 14 experienced ovulation of the cystic follicle. Significantly lower oestradiol-17beta concentration was found on day 7 in cows showing a low-low-low pattern than a low-low-high pattern of progesterone (43.0 +/- 4.6 vs 55.8 +/- 2.8 pmol/l, p < 0.05). There was no significant difference in cortisol concentration on any days (days 0, 7 and 14) between cows showing a low-low-low and low-low-high pattern of progesterone. These results suggest that approximately one-fifth of cows diagnosed to have ovarian cysts possess luteal cysts and that a high oestradiol-17beta concentration at the time of GnRH administration is involved in the subsequent ovulation of the follicle, although ovulated follicle may not be cystic.

Estrogen receptors alpha and beta and progesterone receptors in normal bovine ovarian follicles and cystic ovarian disease

The purpose of this study was to determine by immunohistochemistry the expression of estrogen and progesterone receptors in ovarian follicular structures from cows with cystic ovarian disease (COD) and to compare these with normal ovarian structures. Secondary, tertiary, atretic, and cystic follicles were evaluated. The follicular cysts of animals with COD presented a significantly higher expression of estrogen receptor alpha in all follicular layers than secondary, tertiary, and atretic follicles in both groups (P < .05). The intensity of estrogen receptor beta in the granulosa cell layer was stronger in tertiary than in secondary and atretic follicles in normal animals (P < .05) and in growing and cystic follicles in animals with COD (P < .05). Theca cells were scarcely stained in the 2 groups. Growing follicles and cysts from COD animals were less stained than tertiary follicles from normal animals (P < .05). Differences did not exist between the 2 groups with regard to the progesterone receptor. Ovaries of animals with COD exhibited altered estrogen receptors expression compared with that in normal animals.

Implication of cortisol and 11β-hydroxysteroid dehydrogenase enzymes in the development of porcine (Sus scrofa domestica) ovarian follicles and cysts

This study investigated cortisol inactivation by 11β-hydroxysteroid dehydrogenase (11β HSD) enzymes in porcine granulosa cells from antral follicles at different developmental stages and in ovarian cysts. In granulosa cells, cortisol oxidation increased threefold with antral follicle diameter (P< 0.001). This trend was paralleled by a threefold increase in NADP+-dependent 11β-dehydrogenase activity in granulosa cell homogenates with follicle diameter. Intact granulosa cells from ovarian cysts exhibited significantly lower enzyme activities than cells from large antral follicles. Neither intact cells norcell homogenates displayed net 11-ketosteroid reductase activities. Since porcine follicular fluid (FF) from large antral follicles and ovarian cysts contains hydrophobic inhibitors of glucocorticoid metabolism by type 1 11β HSD, this studyalso investigated whether levels of 11β HSD inhibitors changed during follicle growth and could affect cortisol metabolism in granulosa cells. The extent of inhibition of 11β HSD1 activity in rat kidney homogenates decreased progressively from 50 ± 8% inhibition by FF from small antral follicles (P< 0.001) to 23 ± 6% by large antral FF (P< 0.05). Cyst fluid inhibited 11β HSD1 activity by 59 ± 4% (P< 0.001). Likewise, net cortisol oxidation in granulosa cells was significantly decreased by large antral FF (35–48% inhibition,P< 0.05) and cyst fluid (45–75% inhibition,P< 0.01). We conclude that inactivation of cortisol by 11β HSD enzymes in porcine granulosa cells increases with follicle development but is significantly decreased in ovarian cysts. Moreover, changes in ovarian cortisol metabolism are accompanied by corresponding changes in the levels of paracrine inhibitors of 11β HSD1 within growing ovarian follicles and cysts, implicating cortisol in follicle growth and cyst development.

Deficient Proliferation and Apoptosis in the Granulosa and Theca Interna Cells of the Bovine Cystic Follicle

The aim of the present study was to examine the frequencies of cell proliferation and death of granulosa and theca interna layers during development of cystic follicles in order to understand the mechanisms of cystic follicle formation. Paraffin sections of cystic follicles were immunostained with antibodies against proliferating cell nuclear antigen (PCNA) and cleaved caspase-3 in order to observe proliferating and apoptotic cells, respectively. The concentrations of estradiol-17beta and progesterone in the follicular fluid of these follicles were measured by ELISA. The granulosa and theca interna layers contained both PCNA- and caspase-3-positive cells, although their numbers were limited. There was significant negative correlation between the estradiol-17beta and progesterone concentrations in the follicular fluid. Regression analysis revealed no significant correlation, except for that between the PCNA-positive cells in the theca interna and the caspase-3-positive cells in the granulosa layer. These results indicate that the granulosa and theca interna cells of the cystic follicle show weak proliferative activity and low apoptotic frequency; this implies that the cystic follicle grows slowly and then maintains a static condition without degeneration, which leads to long-term persistence of the follicle.

Effects of metformin on bovine granulosa cells steroidogenesis: possible involvement of adenosine 5' monophosphate-activated protein kinase (AMPK)

In mammals, IGFs are important for the proliferation and steroidogenesis of ovarian cells. Metformin is an insulin sensitizer molecule used for the treatment of the infertility of women with polycystic ovary syndrome. It is, however, unclear whether metformin acts on ovarian cells. Adenosine 5' monophosphate-activated protein kinase (AMPK) is involved in metformin action in various cell types. We investigated the effects of metformin on bovine granulosa cell steroidogenesis in response to IGF1 and FSH, and studied AMPK in bovine ovaries. In granulosa cells from small follicles, metformin (10 mM) reduced production of both progesterone and estradiol and decreased the abundance of HSD3B, CYP11A1, and STAR proteins in presence or absence of FSH (10(-8) M) and IGF1 (10(-8) M). In cows, the different subunits of AMPK are expressed in various ovarian cells including granulosa and theca cells, corpus luteum, and oocytes. In bovine granulosa cells from small follicles, metformin, like AICAR (1 mM) a pharmaceutical activator of AMPK, increased phosphorylation of both Thr172 of AMPK alpha and Ser 79 of ACACA (Acetyl-CoA Carboxylase). Both metformin and AICAR treatment reduced progesterone and estradiol secretion in presence or absence of FSH and IGF1. Metformin decreased phosphorylation levels of MAPK3/MAPK1 and MAPK14 in a dose- and time-dependent manner. The adenovirus-mediated production of dominant negative AMPK abolished the effects of metformin on secretion of progesterone and estradiol and on MAPK3/MAPK1 phosphorylation but not on MAPK14 phosphorylation. Thus, in bovine granulosa cells, metformin decreases steroidogenesis and MAPK3/MAPK1 phosphorylation through AMPK activation.

Supra-basal progesterone concentrations during the follicular phase are associated with development of cystic follicles in dairy cows

The objective of this study was to test the hypothesis that supra-basal concentrations of progesterone during the follicular phase are associated with the development of follicular cysts. Twenty-five non-lactating dairy cows were used in the study, which was performed over five identical replicate trials. Luteolysis was induced during the mid-luteal phase. Transrectal ultrasonography was performed daily to determine the occurrence/timing of ovulation. Plasma samples were collected for progesterone, oestradiol and luteinizing hormone (LH) analysis. Three cows failed to ovulate (cystic anovulatory) but did ovulate in a subsequent replicate (cystic ovulatory). Eight cows from the appropriate replicates were used as control cows (normal group). Follicular growth patterns and plasma oestradiol concentrations were similar between the three groups. However, the plasma progesterone concentrations during the follicular phase were twofold higher in the cystic anovulatory group (P < 0.01). Furthermore, no LH surge was detected in these animals. While LH pulse amplitude was similar between groups, LH pulse frequency in the cystic anovulatory group was attenuated (P < 0.05). In conclusion, the formation of follicular cysts were preceded by elevated plasma progesterone concentrations and the suppression of the LH surge.

Effect of a single injection of progesterone on ovarian follicular cysts in lactating dairy cows

The objective of this experiment was to evaluate the effect of a single injection of progesterone on the lifespan of ovarian follicular cysts and to examine the fate of follicles that mature following treatment. Lactating Holstein and Jersey cows with ovarian follicular cysts were identified by rectal palpation. The ovaries of cystic cows were then examined by transrectal ultrasonography three times weekly to monitor formation of new follicular cysts. Cows with newly formed follicular cysts were treated either with a single injection of progesterone (200 mg, IM, n = 11) or corn oil vehicle (n = 7). Venous blood samples were collected daily for quantification of progesterone. Blood sampling and ultrasonography continued until ovulation or a new follicular cyst formed. Treatment reduced the lifespan of the cyst by 12 days, from 29.8 +/- 2.3 days in control cows to 17.2 +/- 1.8 days in progesterone-treated cows (P = 0.01). Progesterone treatment also tended to alter the frequency of subsequent follicular events. Ovulation occurred in 4/11 cows that were treated with progesterone whereas none of the vehicle treated cows ovulated (P = 0.07). In conclusion, a single injection of 200mg of progesterone, administered early in the life of an ovarian follicular cyst, shortened its lifespan and in some cases was followed by ovulation of a new follicle.

Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

Cystic ovarian follicles (COF) are an important ovarian dysfunction and a major cause of reproductive failure in dairy cattle. Due to the complexity of the disorder and the heterogeneity of the clinical signs, a clear definition is lacking. A follicle becomes cystic when it fails to ovulate and persists on the ovary. Despite an abundance of literature on the subject, the exact pathogenesis of COF is unclear. It is generally accepted that disruption of the hypothalamo-pituitary-gonadal axis, by endogenous and/or exogenous factors, causes cyst formation. Secretion of GnRH/LH from the hypothalamus-pituitary is aberrant, which is attributed to insensitivity of the hypothalamus-pituitary to the positive feedback effect of oestrogens. In addition, several factors can influence GnRH/LH release at the hypothalamo-pituitary level. At the ovarian level, cellular and molecular changes in the growing follicle may contribute to anovulation and cyst formation, but studying follicular changes prior to cyst formation remains extremely difficult. Differences in receptor expression between COF and dominant follicles may be an indication of the pathways involved in cyst formation. The genotypic and phenotypic link of COF with milk yield may be attributed to negative energy balance and the associated metabolic and hormonal adaptations. Altered metabolite and hormone concentrations may influence follicle growth and cyst development, both at the level of the hypothalamus-pituitary and the ovarian level.

Microvascular distribution and vascular endothelial growth factor expression in bovine cystic follicles

The aim of this study was to examine the distribution of microvessels in the theca and the expression of vascular endothelial growth factor (VEGF) in the theca and granulosa of cystic follicles. Paraffin sections of cystic follicles were stained with Bandeiraea simplicifolia-I (BS-I) to visualize the endothelial cells of microvessels. The other sections were immunostained with anti-VEGF antibody. The mRNA expression of VEGF in the theca interna of cystic and healthy follicle was determined by RT-PCR. In the theca interna, cystic follicles with granulosa cells had significantly greater microvessel number density (the number of microvessels per given field) and area (area occupied by microvessels per given area) than healthy follicles in various sizes (<3, 4-8, >9 mm). Loss of granulosa cells from cystic follicles resulted in a similar number density, but significantly smaller area of microvessels in the theca interna. There was no significant difference in the microvessel number density and area of the theca externa between the types of follicle. VEGF protein was expressed in the granulosa and theca interna of healthy and cystic follicles. These results demonstrate that cystic follicles have a highly developed vasculature network in the theca interna, especially in cystic follicles containing granulosa cells. It is also suggested that VEGF is highly expressed in the cystic follicle as well as healthy follicle, which may be associated with advanced vasculature and the accumulation of follicular fluid in cystic follicles.

Studies on substantially increased proteins in follicular fluid of bovine ovarian follicular cysts using 2-D PAGE and MALDI-TOF MS

BACKGROUND

The objective of this study was to identify substantially increased proteins in bovine cystic follicular fluid (FF) in order to clarify the pathology and etiology of bovine ovarian follicular cysts (BOFC).

METHODS

Proteins in normal and cystic FF samples were subjected to two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and were compared using silver stained gel images with PDQuest image analysis software. Peptides from these increased spots were analyzed by matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), and were identified based on the NCBI database by a peptide mass fingerprinting method.

RESULTS

Comparative proteomic analysis showed 8 increased protein spots present in cystic FF. MS analysis and database searching revealed that the increased proteins in cystic FF were bovine mitochondrial f1-atpase (BMFA), erythroid associated factor (EAF), methionine synthase (MeS), VEGF-receptor, glyceraldehydes 3-phosphate dehydrogenase (GAPDH), heat shock protein 70 (HSP70), beta-lactoglobulin (BLG) and succinate dehydrogenase Ip subunit (SD).

CONCLUSION

Our results suggest that these proteins are overexpressed in BOFC, and that they may play important roles in the pathogenesis of BOFC. Furthermore, these proteins in the FF could be useful biomarkers for BOFC.

Gonadotropin requirements for dominant follicle selection in GnRH agonist-treated cows

A study was conducted to examine the effects of gonadotropins on ovarian follicular development and differentiation in GnRH agonist (GnRHa)-treated cattle. Holstein cows were allotted into two pre-treatment groups: controls (n = 5) and GnRHa-treated (n = 9). Ovaries were removed from control cows on day 5 following a synchronized estrus. Treatment with GnRHa resulted in follicular arrest at <5 mm. Following follicular arrest, GnRHa-treated cows received a constant infusion of FSH for 96 h (GnRHa/FSH), with a randomly selected subset receiving hourly pulses of LH in addition to FSH during the last 48 h of infusion (GnRHa/FSH + LH). At the end of infusion, ovaries were removed, follicles were counted and measured, and follicular fluid samples were collected from large follicles (>10 mm). Differences in expression of mRNA for LH receptor, FSH receptor, cytochrome P450 side-chain cleavage, 3β-hydroxysteroid dehydrogenase, cytochrome P450 17α-hydroxylase (P450c17) and cytochrome P450 aromatase were determined in large follicles using in situ hybridization. The number of large follicles did not differ between GnRHa/FSH-treated and GnRHa/FSH + LH-treated cows (P = 0.64), but was greater than control animals (P ≤ 0.004). Follicular fluid concentrations of estradiol-17β and androstenedione were highest in GnRHa/FSH + LH-treated cows (P ≤ 0.04), intermediate in control cows, and lowest in GnRHa/FSH-treated cows. Hybridization intensity of P450c17 was greater in GnRHa/FSH + LH-treated versus control or GnRHa/FSH-treated cows (P ≤ 0.03). These results indicate that while FSH can support bovine follicular growth >10 mm, LH increases androgen production and expression of P450c17.

An Update on Cystic Ovarian Degeneration in Cattle

Cystic ovarian degeneration (COD) is considered to be one of the most important causes of reproductive failure in cattle. There is a severe economic loss to dairy industry because COD increases days-open in the postpartum period and the culling rates. The disease process is a consequence of a mature follicle that fails to ovulate at the appointed time of ovulation in the oestrous cycle. This anovulatory follicular structure either regresses or persists as a follicular or luteal cyst depending upon its structural/functional characteristics. The cells lining the follicular cyst synthesize oestrogen that, in certain instances, forces the animal to exhibit clinical signs of nymphomania. Besides oestrogen production, as per recent findings, they are also capable of secreting varying amount of progesterone which may dictate their fate. The animals that carry a luteal cyst may tend to be in anoestrus as the higher amount of progesterone secreted by this luteinized structure may change the pattern of gonadotrophins' secretion. Present findings suggest that perturbation of the hypothalamo-hypophyseal-ovarian (HHO) axis, due to many exogenous and endogenous factors, as the cause for anovulation. For example, it has been suggested that lack of hypothalamic or hypophyseal response to the positive feedback effect of oestrogens that are secreted by the dominant follicle as one of the many causes. The non-physiological changes that occur in the receptor expression of the HHO axis for the hormones involved in maturation, deviation, dominance and ovulation of the follicle may be yet another cause. The changes that occur at the cellular and molecular level in the ovary (in response to the factors mentioned above) that contribute to anovulation remain to be documented. This approach would allow us to completely understand the disease process. Hitherto, hormonal preparations that release luteinizing hormone from the anterior pituitary or have luteinizing hormone-like action are used to treat follicular cysts. GnRH belongs to the former group and human chorionic gonadotrophin (hCG) hormone forms the latter group. Treatment with a luteolytic agent, prostaglandin F2alpha (PGF2alpha), is successful if a luteal cyst is diagnosed properly. Many agents may be developed in the future if the cellular and molecular pathways of the disease process are delineated. This article will review recent advances in our understanding of the pathogenesis of COD and suggest direction for future studies to completely understand the disease mechanism. This review will also discuss the existing method of treatments for cysts and methods proposed for treatment of cysts that tend to be refractory in nature.

Distribution of cytochrome P450-side chain cleavage in the theca interna layers of bovine small antral and cystic follicles

Cystic follicle is anovulatory follicular structure that is caused by an endocrine imbalance. The activity of cytochrome P450-side chain cleavage (P450scc) is essential for the initiation of steroidogenesis in the follicle. The present study was designed to compare the frequency of cells containing P450scc between healthy and atretic small antral follicles, and among several types (I, II and III, classified based on the presence of granulosa layer) of cystic follicles. Paraffin sections of healthy (2-5 mm in diameter), atretic (2-5 mm) and cystic follicles (>25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine P450scc. The P450scc-positive cells were counted in four different regions of the follicles from the apical to the basal side. In small antral follicles and cystic follicles, P450scc-positive cells were localized in the theca interna layers but not granulosa layers. The P450scc-positive cell populations decreased in the late atretic follicles compared with the early and advanced atretic follicles at all the regions of follicle. Type III cystic follicles showed significantly lower frequencies of P450scc-positive cells than those in the types I and II cystic follicles. These results suggest that in both small and cystic follicles in cows, total loss of granulosa cells may be associated with the reduction of frequency of P450scc-positive cells in theca interna layer.

Ovarian modulators of 11beta-hydroxysteroid dehydrogenase (11beta HSD) activity in follicular fluid from bovine and porcine large antral follicles and spontaneous ovarian cysts

In the ovary, cortisol is oxidized to cortisone by 11beta-hydroxysteroid dehydrogenase (11betaHSD). The present study investigated whether follicular fluid (FF) from large antral follicles and spontaneous ovarian cysts, isolated from bovine and porcine ovaries, contained modulators of 11betaHSD activity. Whereas FF from antral follicles had no significant effect over 1 h on NADP+-dependent 11betaHSD activity in rat kidney homogenates, enzyme activity was inhibited by FF from bovine and porcine ovarian cysts (80.5% +/- 2.3% and 72.8% +/- 3.4% of control, respectively). Following C18 reverse-phase chromatography, the hydrophilic fractions of FF from bovine and porcine antral follicles stimulated NADP+-dependent 11betaHSD activities (111.5% +/- 21.6% and 55.2% +/- 5.7% respectively). Hydrophobic compounds inhibited NADP+-dependent cortisol oxidation by 58.2% +/- 5.1% (bovine) and 45.7% +/- 2.0% (porcine). In both species, FF from ovarian cysts appeared to contain less of the hydrophilic stimuli to 11betaHSD activity and more of the hydrophobic inhibitors. The FF from antral follicles and ovarian cysts, and the C18 fractions thereof, had no significant effect on NAD+-dependent cortisol oxidation. The ovarian modulators of NADP+-dependent 11betaHSD activities did not coelute with cortisol, cortisone, estradiol, testosterone, progesterone, pregnenolone, and cholesterol. However, the 11betaHSD stimuli in porcine FF from both antral follicles and cysts coeluted with prostaglandin (PG) E2 and PGF2alpha. We conclude that large antral follicles and spontaneous ovarian cysts, in both the cow and the pig, contain ovarian modulators of the NADP+-dependent 11betaHSD activity. Moreover, FF from spontaneous ovarian cysts, because of decreased content of the 11betaHSD stimulus accompanied by increased content of the 11betaHSD inhibitors, exerts a net inhibitory effect on 11betaHSD activity.

lmmunohistochemical Localization of 3.BETA.-Hydroxysteroid Dehydrogenase in the Granulosa and Theca Interna Layers of Bovine Cystic Follicles

The aim of the present study was to determine whether the alteration of population of cells containing 3beta-hydroxysteroid dehydrogenase (3beta-HSD) is responsible for the formation of cystic follicles. Paraffin sections of healthy (2 to 5 mm in diameter), atretic (2 to 5 mm) and cystic follicles (more than 25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine 3beta-HSD. The 3beta-HSD-positive cells were counted in 4 different regions of the follicles from the apical to the basal side. The frequencies of 3beta-HSD-positive granulosa cells in cystic follicles were significantly higher than those in the healthy follicles (P<0.05), although the number of 3beta-HSD-positive granulosa cells in the cystic follicle were fewer than half the cells (30 to 40%) and was much smaller than that in preovulatory follicles (Conley et al., 1995). The frequencies of 3beta-HSD-positive cells were higher in the granulosa layer and lower in the theca interna layer of the cystic follicles than the atretic follicles. These results suggest that the differentiation of granulosa cells to express 3beta-HSD might be insufficient in cystic follicles and accordingly they fail to ovulate. The differences of frequencies of 3beta-HSD-positive cells in the granulosa and theca interna layers between cystic and atretic follicles may be one of the reasons why regression is delayed in cystic follicles.

Perturbation of estradiol-feedback control of luteinizing hormone secretion by immunoneutralization induces development of follicular cysts in cattle

We used immunoneutralization of endogenous estradiol to investigate deficiencies in the estradiol-feedback regulation of LH secretion as a primary cause of follicular cysts in cattle. Twenty-one cows in the prostaglandin (PG) F(2alpha)-induced follicular phase were assigned to receive either 100 ml of estradiol antiserum produced in a castrated male goat (n = 11, immunized group) or the same amount of castrated male goat serum (n = 10, control group). The time of injection of the sera was designated as 0 h and Day 0. Five cows in each group were assigned to subgroups in which we determined the effects of estradiol immunization on LH secretion and follicular growth during the periovulatory period. The remaining six estradiol-immunized cows were subjected to long-term analyses of follicular growth and hormonal profiles, including evaluation of pulsatile secretion of LH. The remaining five control cows were used to determine pulsatile secretion of LH on Day 0 (follicular phase) and Day 14 (midluteal phase). The control cows exhibited a preovulatory LH surge within 48 h after injection of the control serum, followed by ovulation of the dominant follicle that had developed during the PGF(2alpha)-induced follicular phase. In contrast, the LH surge was not detected after treatment with estradiol antiserum. None of the 11 estradiol-immunized cows had ovulation of the dominant follicle, which had emerged before estradiol immunization and enlarged to more than 20 mm in diameter by Day 10. Long-term observation of the six immunized cows revealed that five had multiple follicular waves, with maximum follicular sizes of 20-45 mm at 10- to 30-day intervals for more than 50 days. The sixth cow experienced twin ovulations of the initial persistent follicles on Day 18. The LH pulse frequency in the five immunized cows that showed the long-term turnover of cystic follicles ranged from 0.81 +/- 0.13 to 0.97 +/- 0.09 pulses/h during the experiment, significantly (P < 0.05) higher than that in the midluteal phase of the control cows (0.23 +/- 0.07). The mean LH concentration in the immunized cows was also generally higher than that in the luteal phase of the control cows. However, the LH pulse and mean concentration of LH after immunization were similar to those in the follicular phase of the control cows. Plasma concentrations of total inhibin increased (P < 0.01) concomitant with the emergence of cystic follicles and remained high during the growth of cystic follicles, whereas FSH concentrations were inversely correlated with total inhibin concentrations. In conclusion, neutralization of endogenous estradiol resulted in suppression of the preovulatory LH surge but a normal range of basal LH secretion, and this circumstance led to an anovulatory situation similar to that observed with naturally occurring follicular cysts. These findings provide evidence that lack of LH surge because of dysfunction in the positive-feedback regulation of LH secretion by estradiol can be the initial factor inducing formation of follicular cysts.

Ovarian follicular cysts in dairy cows: an abnormality in folliculogenesis

Ovarian follicular cysts are a major reproductive problem in lactating dairy cows. The primary physiological defect leading to the formation of ovarian follicular cysts is a failure of the hypothalamus to trigger the preovulatory surge of luteinizing hormone (LH) in response to estradiol. The factor responsible for this hypothalamic defect may be progesterone. Intermediate levels of progesterone have been shown to prevent ovulation and promote persistence of dominant follicles in normal cycling cows. Recently, we found that 66% of cows with ovarian follicular cysts had progesterone concentrations in an unusual, intermediate range (0.1-1.0 ng/mL) at the time of their detection. A majority of new follicles (76%) that develop in the presence of these intermediate progesterone concentrations became cysts. Only 10% ovulated. Based on these observations, a novel model for the formation and turnover of ovarian follicular cysts is proposed.

Expression of the bovine oestrogen receptor-beta (bERbeta) messenger ribonucleic acid (mRNA) during the first ovarian follicular wave and lack of change in the expression of bERbeta mRNA of second wave follicles after LH infusion into cows

In a previous study, the ERbeta cDNA protein-coding region was utilised to clone bovine ERbeta. The objectives in this study were to examine (1) ERbeta mRNA expression in ovarian follicles throughout the bovine first follicular wave, and (2) effect of LH infusion into cows on bERbeta mRNA expression during the second follicular wave. In experiment 1, heifers (4-5 per time point) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, 96, 144, or 216 h after emergence of the first follicular wave after oestrus. In experiment 2, saline or LH was pulsed hourly (computer-controlled syringe pump) into cows (n = 31; 5-6 per treatment) at wave emergence for 2 or 4 days: wave 1-saline (W1S), wave 2-saline (W2S), or wave 2-LH (25 microg/h; W2LH). Ovaries were removed on day 2 or day 4 after wave emergence. Follicles, 2-19mm in size, were dissected, frozen, and stored at -80 degrees C for in situ hybridisation with two bERbeta cRNA probes. Expression of bERbeta mRNA was localised in granulosa cells of healthy follicles. In experiment 1, bERbeta mRNA expression did not change with time points of the wave showing no association of bERbeta mRNA expression with follicular selection and dominance. However, bERbeta mRNA expression decreased with increase in size of all follicles. Expression of bERbeta mRNA was greater in very small follicles (2-4 mm) than in large (> or = 9 mm) follicles. In experiment 2, expression of bERbeta mRNA in follicles did not differ either between W1S and W2S or between W2S and W2LH. In summary, bERbeta mRNA expression decreased with increasing follicular size. However, neither stage of the wave (selection or dominance), nor pulsatile infusion of LH influenced bERbeta mRNA expression.