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

Association between endometrial protein expression of IFN-γ and delayed conception after parturition in dairy cows

The cytokine context present in the reproductive tract of cows is closely involved in normal uterine functions, including the estrous cycle and the establishment and maintenance of pregnancy. However, the roles of some cytokines in the uterus, and their relation with reproductive performance remain to be elucidated. Thus, this study aimed to examine the protein expression of several cytokines such as TNFα, IL-6, IL-8, IFNγ, IL-4, and TGF-β3 in endometrial biopsies previous to conception, to evaluate the possible association with delayed conception in dairy cows. Protein expression levels were evaluated by immunohistochemistry. Results showed that the protein expression levels of TNFα, IL-6, IL-4 and TGF-β3 were not associated with the parturition-conception interval, whereas the high protein expression levels of IFNγ were associated with the parturition-conception interval. Finally, the low protein expression of IL-8 showed a statistical tendency to be associated with delayed conception. This is the first report about the protein expression of IFN-γ in the endometrium of dairy cows and also, this cytokine could enhance the favorable conditions to achieve an early pregnancy.

Cholecystokinin-mediated effect of insulin pathway on the steroidogenic activity of follicular granulosa cells in Camelus bactrianus: In vitro study

The current study aimed to explore the molecular mechanism by which the cholecystokinin (CCK)-mediated CCKAR and CCKBR, as well as the molecular mechanisms of CCK-mediated insulin signalling pathway, regulate oestrogen in the granulosa cells. Also, the expression of CCK in ovaries, uterus, hypothalamus and pituitary gland was investigated in Camelus bactrianus. Ovaries, uterus, hypothalamus and pituitary gland were collected from six, three before ovulation (control) and three after ovulation, slaughtered Camelus bactrianus. Ovulation was induced by IM injection of seminal plasma before slaughtering in the ovulated group. The results showed that there were differences in the transcription and protein levels of CCK in various tissues before and after ovulation (p < .05, p < .01). After transfection with p-IRES2-EGFP-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly upregulated (p < .05, p < .01), and the content of E2 was significantly upregulated (p < .01); On the contrary, after transfection with si-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly downregulated (p < .05, p < .01), and the content of E2 was significantly downregulated (p < .01). Regulating CCK can affect the mRNA levels of INS, INSR, IGF and IGF-R. In summary, regulating the expression level of CCK can activate insulin-related signalling pathways by CCKR, thereby regulating the steroidogenic activity of granulosa cells.

Altered expression of angiogenic factors in dominant preovulatory follicles of dairy cattle treated with ACTH

Studies in cows have reported that ovulation, steroidogenesis and angiogenesis are affected by stress and consequently fertility decreases. The purpose of this study was to evaluate the effects of ACTH administration during the preovulatory period on the expression of growth factors (CD-31, PDGF-A, PDGF-B, VEGFA-164, VEGFA-164b, VEGF-R1 and VEGF-R2) associated with the angiogenic process by immunohistochemistry in cows (n = 14). Results evidenced the expression of these growth factors in theca and granulosa cells from antral, atretic and dominant preovulatory follicles of ACTH-treated cows, suggesting that, under stress conditions, their expression continues to be required. VEGFA-164, VEGF-R1 and VEGF-R2 expression was greater in theca cells of dominant preovulatory follicles of the ACTH-treated group than in those of the control group. CD-31 protein expression was lower in the dominant preovulatory follicles of the ACTH-treated group than in those of the control group. PDGF-A and PDGF-B expression did not differ between groups, either in granulosa or in theca cells. These results suggest that VEGFA-164, its receptors and CD-31 are actors in the normal cycle of the ovaries and could have greater pathophysiological importance in the altered angiogenic process and other events that occur during anovulation and stress conditions. This dysregulation reinforces the importance of the angiogenic process in the pathophysiology of cystic ovarian disease in cows. This is the first report on the expression and localization of components of the VEGF and PDGF systems and CD-31 in cells from dominant preovulatory follicles after ACTH administration.

Association of glucocorticoid receptor expression with key members of the insulin signaling pathway and heat shock proteins in the bovine ovary

Glucocorticoids (GCs) act through their receptor (GR) as regulators in different biological processes such as reproduction. In the absence of GCs, the GR remains inactive in the cytoplasm by associating with heat shock proteins (HSPs), which act as molecular chaperones, among which the most relevant are HSP90 and HSP70. Cytoplasmic GC-activated GR mediates non-genomic effects, interacting with members of signaling pathways such as PI3K/Akt, which participates in several metabolic processes, including the insulin signaling pathway. The aim of the present study was to evaluate possible associations between the cytoplasmic GR and the main intermediates of the insulin signaling pathway and HSP90 and HSP70 in ovaries of dairy cows. To this end, the protein expression of cytoplasmic GR, key members of the insulin signaling pathway, and HSPs was evaluated in ovarian preovulatory follicles of non-lactating Holstein cows in proestrus. Positive associations were observed between protein expression of GR and HSP90, IRS1, pIRS1, PI3K and pAkt (p < 0.05; β > 0) in granulosa cells of dominant follicles of dairy cows. Instead, in theca cells, no associations were observed between protein expression of GR and members of the insulin signaling pathway or HSPs. These data provide evidence of the possible association between the non-genomic mechanisms of action of the GR and the insulin signaling pathway in the bovine ovary.

ACTH impairs the migratory and secretory profile of mononuclear cells during proestrus in cattle

The aim was to evaluate the effect of ACTH on the mechanisms involved in peripheral blood mononuclear cells (PBMCs) infiltration into the ovary during dairy cattle proestrus. Regarding this, proper expression pattern of adhesion molecules must take place both in PBMCs and in endothelial cells. Argentinian Holstein cows (n = 12) were treated with 100 IU of ACTH every 12 h for 4 days before ovulation when ovariectomy was performed (day 18). Blood samples were taken on day 15 (0 h) and immediately before (72 h) and after (74 h) the last ACTH administration. In PBMCs, flow cytometry was performed to analyze CD44, CD11b and CD62-L expression along with gene expression of chemokines' receptors. Interleukin (IL)-4 and tumor necrosis factor-α (TNF-α) production was analyzed by flow cytometry after exposing PBMCs to autologous follicular fluid. In ovarian blood vessels, expression of the vascular endothelium cell adhesion-1 (VCAM-1) and the platelet endothelial cell adhesion molecule-1 was evaluated by immunohistochemistry. In T-lymphocytes, the expression of CD44 and CD11b was lower at 72 h in ACTH-treated cows (P < 0.05). In monocytes, the expression of CD11b and CD62-L was lower at 72 h in ACTH-treated cows (P < 0.05). Also, the percentage of IL-4+ cells was higher in ACTH-treated cows, meanwhile, the percentage TNF-α+ cells was lower in ACTH-treated cows (P < 0.05). Finally, in the vessels associated with the preovulatory follicle VCAM-1 immunoexpression was lower in ACTH-treated cows (P < 0.05). Here, we present novel insights into the effect of stress during the preovulatory period on the inflammatory pathway necessary for ovulation.

Matrix-free three-dimensional culture of bovine secondary follicles to antral stage: Impact of media formulation and epidermal growth factor (EGF)

Disrupted/disordered ovarian steroidogenesis is associated with several fertility disorders such as polycystic ovary syndrome in humans and cystic ovarian disease in cattle. Methods to interrogate theca cell processes as part of follicular development are necessary to further research into treatments for these types of disorders. Multilayer follicles of dairy-breed cows were placed into culture in a novel matrix-free 3D system using round bottom low-attachment plates. Follicles were first cultured in the presence of two types of media previously used for in vitro follicle maturation (basal α-MEM and basal T-199). After the optimal media was identified, impact of supplementation of epidermal growth factor (EGF) on growth and survival of bovine secondary follicles to antral stage was evaluated. No differences were observed in growth and survival of follicles cultured in basal α-MEM media or basal T-199 media, although T-199 media's high phenol red content made assessment of follicles difficult. Further studies were then performed with α-MEM media. Three cohorts of follicles were observed based on time to antrum formation: ≤ 5 days (fast), 6-19 days (slow), or survived but did not form an antrum by 21 days (no). Supplementation of EGF to the basal α-MEM media dramatically improved follicle survival rates in culture (defined as follicles that either formed an antrum or did not form an antrum but did not die during 21 day culture period) from 29% to 95.7% (Chi-square p < 0.0001). However, in follicles that survived to form an antrum there were no differences in proportion of fast, slow and no antrum follicles after addition of EGF (Chi-square p > 0.7). Fast antrum follicles treated with EGF plateaued in size earlier in culture compared to controls (p = 0.013). Slow and no antrum follicles were larger in diameter during EGF culture than controls (p's < 0.0001). Many follicles cultured in this matrix-free system that formed an antrum approached 1.5-2 mm in size, an improvement from previous single follicle culture methods used for bovine pre-antral follicles in vitro. In addition, follicles displayed functional steroidogenesis in vitro producing measureable levels of estradiol and androstenedione. This matrix-free 3D culture system provides an excellent in vitro model to explore processes associated with folliculogenesis in cattle.

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.

Alterations in the insulin signaling pathway in bovine ovaries with experimentally induced follicular persistence

Reproductive diseases in dairy cows as cystic ovarian disease (COD) represent a major problem that impacts on dairy production. COD is characterized by anovulation, persistence of the dominant follicle, and interruption of normal estrous cycles. Anovulation is attributable to a failure in the LH surge, due to endocrine imbalances and alterations in local factors, such as the insulin signaling pathway. Thus, the aim of this study was to examine the expression of critical nodes of the insulin pathway, including insulin receptor (IR), IR substrate (IRS), phosphatidylinositol-3-kinase (PI3K), and protein kinase B (also known as Akt or pan-Akt), in ovarian follicular structures of cows during the development of follicular persistence induced by long-term progesterone administration. Immunoexpression of IR, p-IR, IRS1, p-IRS1, PI3K, pan-Akt and p-pan-Akt was evaluated in situ by immunohistochemistry and the concentration of insulin in serum and follicular fluid was determined by radioimmunoassay. p-IR, p-IRS1, PI3K and p-pan-Akt expression was decreased in follicles at different times of persistence in relation to the control dominant follicles, in both granulosa and theca cells, whereas IR and IRS1 immunoexpression was decreased in persistent follicles at 5 and 15 days of persistence in granulosa cells. Serum and follicular fluid insulin concentration was higher in cows with persistent follicles than in control cows. These results show that decreased expression and/or activation of the receptors and other intermediates of the insulin signaling pathway in persistent follicles indicates that reduced response/resistance to insulin rather than the concentration of insulin per se may be one of the important molecular mechanisms in the development of persistent follicles in dairy cows.

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.

Lectin histochemical pattern on the normal and cystic ovaries of sows

The lectin histochemical pattern (LHP) was characterized and compared in normal and cystic ovaries of sows. Six biotinylated lectins (PNA, SBA, WGA, RCA-1, DBA and UEA-1) were used on tissue sections. In the normal ovaries, the reaction to UEA-1 and SBA was mild to moderate in mesothelial and endothelial cells. RCA-1 staining was mild to moderate in theca interna of growing follicles, corpora luteum and mesothelium. In addition, this lectin presented strong reaction in endothelial cells, granulosa cells of atretic follicles, zona pellucida of growing follicles and plasma. DBA showed strong intensity in mesothelial and endothelial cells. There was mild to moderate reactivity to WGA in granulosa cells, corpus luteum and theca interna of follicles in development, and moderate in zona pellucida, in granulosa cells of atretic follicles and mesothelium. PNA staining was mild to moderate in oocytes and in the adventitia and media of medullary arteries. Changes in the LHP of the cystic ovaries were noted; however, there were no differences in these findings between the follicular and luteinized cysts. UEA-1 reactivity in the cystic ovaries was moderately reduced in the mesothelial and endothelial cells, whereas there was mild reduction in the DBA staining in the granulosa cells. Reaction to RCA-1 and WGA in the cysts also was decreased in theca interna, zona pellucida and granulosa cells of atretic follicles. Furthermore, endothelium and theca interna in the cystic ovaries presented mild reduction of marcation to SBA, whereas there was decreased reactivity to PNA in the oocytes and adventitia and media layers of the medullary arteries. The results of the current study show that cysts modify the LHP in swine ovaries. These changes of glycoconjugates in many ovarian structures could modify diverse process and may be one of the reasons for decreased fertility in sows.

BMP2, 4 and 6 and BMPR1B are altered from early stages of bovine cystic ovarian disease development

Cystic ovarian disease (COD) is an important cause of subfertility in dairy cattle. Bone morphogenetic proteins (BMPs), mainly BMP2, BMP4 and BMP6, play a key role in female fertility. In this study, we hypothesized that an altered BMP system is associated with ovarian alterations contributing to COD pathogenesis. Therefore, we examined the expression of BMP2, BMP4 and BMP6 and BMP receptor 1B (BMPR1B) in the ovaries of animals with spontaneous or ACTH-induced COD, as well as during the development of the disease, in a model of follicular persistence induced by low doses of progesterone (at 5, 10 and 15 days of follicular persistence). Results showed changes in BMP2, BMP4 and BMP6 expression during folliculogenesis, in granulosa and theca cells in the COD groups, as well as at different stages of follicular persistence. Results also showed changes in BMPR1B expression in developing follicles in animals with COD, and at the initial stages of follicular persistence (P5). Comparison between groups showed significant differences, mainly in BMP4 and BMP6 expression, in granulosa and theca cells of different follicular categories. The expression of these BMPs also increased in cystic and persistent follicles, in relation to antral follicles of the control group. BMPR1B showed high expression in cystic follicles. Together, these results may indicate an alteration in BMPs, especially in BMP4 and BMP6, as well as in BMPR1B, which occurs early in folliculogenesis and incipiently during the development of COD, which could be a major cause of recurrence of this disease in cattle.

Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/152/4/333.abstract.

Role of Glucocorticoids in Cystic Ovarian Disease: Expression of Glucocorticoid Receptor in the Bovine Ovary

The aim of this study was to characterize the expression of glucocorticoid receptor (GR) in the components of normal bovine ovary and in animals with cystic ovarian disease (COD). Changes in the protein and mRNA expression levels were determined in control cows and cows with COD by immunohistochemistry and real-time PCR. GR protein expression in granulosa cells was higher in cysts from animals with spontaneous COD and adrenocorticotropic hormone-induced COD than in tertiary follicles from control animals. In theca interna cells, GR expression was higher in cysts from animals with spontaneous COD than in tertiary follicles from control animals. The increase in GR expression observed in cystic follicles suggests a mechanism of action for cortisol and its receptor through the activation/inactivation of specific transcription factors. These factors could be related to the pathogenesis of COD in cattle.

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.

Characterization of persistent follicles induced by prolonged treatment with progesterone in dairy cows: an experimental model for the study of ovarian follicular cysts

Cystic ovarian disease (COD) is a major factor contributing to poor reproductive efficiency of lactating dairy cows. The objective of the present study was to analyze the endocrine profile, growth dynamics, and histologic characteristics of persistent ovarian follicles-cysts developing in response to long-term administration of intermediate levels of progesterone. To this end, after synchronization of cows, a low dose of progesterone was administered for 5, 10, and 15 days after the expected day of ovulation in treated cows (groups P5, P10, and P15, respectively), using an intravaginal progesterone-releasing device. A significant increase in diameter was detected on Day 11 of progesterone treatment and thereafter (P < 0.05), and at Day 15 of persistence, the diameter of the persistent follicle reached a mean of 23 ± 0.6 mm. Microscopically, the persistent follicles had a complete granulosa, an intensely vascularized theca interna, and a collagenous theca externa layer. Temporal changes in the serum concentrations of estradiol, progesterone, and FSH were detected (effects of time, P < 0.01). Progesterone treatment completely inhibited the LH preovulatory surge in treated cows and affected the basal concentration of LH. The pulse frequency remained high at 5 and 10 days of persistence and declined (P < 0.05) after 15 days of persistence. The LH pulse concentration and pulse amplitude had a significant reduction (P < 0.05) during follicular persistence. Changes in the serum levels of estradiol, progesterone, 17-hydroxyprogesterone, and testosterone in serum and follicular fluid were also observed. In serum, estradiol increased gradually from proestrus to Day 10 of follicular persistence (P < 0.05), progesterone showed an increase (P < 0.05) at Day 5 of follicular persistence, 17-hydroxyprogesterone showed a significant decrease at 5 days of follicular persistence in relation to proestrus, and testosterone showed a significant increase (P < 0.05) from proestrus and Day 5 of persistence through Day 15 of follicular persistence. Correlation between serum and follicular fluid steroid concentrations was significant for testosterone (P < 0.0001) and not significant for estradiol and progesterone. These findings indicate that ovarian cysts in COD are similar in many ways to the persistent follicles induced by progesterone, with an analogous hormonal and morphologic context, thus confirming a local role of subluteal levels of progesterone in COD pathogenesis and in the regulatory mechanisms of the ovarian function.

Involvement of PAPP-A and IGFR1 in Cystic Ovarian Disease in Cattle

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra-ovarian factors, such as members of the insulin-like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy-associated plasma protein A (PAPP-A). The aim of this study was to determine IGFR1 and PAPP-A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP-A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP-A present in the follicular fluid from these follicles showed no differences. Although no PAPP-A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle.

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.

Identificação imuno-histoquímica de VEGF e IGF-1 em ovários de cadelas no anestro e estro

Com o objetivo de verificar a presença de VEGF e IGF-1 nos ovários de cadelas, foram realizadas análises imuno-histoquímicas do estroma cortical; teca e granulosa de folículos secundários, terciários e terciários pré-ovulatórios luteinizados; e ovócitos de folículos primários, secundários e terciários de ovários de cinco cadelas em anestro (Anest) e cinco em estro (Est). A identificação das fases do ciclo estral foi realizada por citologia vaginal associada a dosagem plasmática de progesterona. Os ovários foram submetidos a tratamento imuno-histoquímico para identificação de VEGF (anticorpo primário PU 360-UP, Biogenex, USA; diluição 1:30) e IGF-1 (anticorpo primário PabCa, Gro-Pep, Austrália; diluição 1:100). Determinou-se um índice de imunomarcação (IM), para cada tecido avaliado, pela razão entre a área positivamente marcada dividida pela área total analisada. Para os ovócitos, verificou-se imunomarcação positiva ou negativa. As comparações de IM entre tecidos foram realizadas pelo teste de Wilcoxon (diferentes tecidos em mesmo grupo) ou Mann-Whitney (mesmo tecido entre diferentes grupos), todas no nível de 5% de significância. VEGF e IGF-1 foram identificados, de forma semelhante (P>0,05), em todas as estruturas avaliadas em ambos os grupos experimentais. Conclui-se que esses fatores de crescimento estão presentes em cadelas no anestro e estro, no estroma cortical ovariano, folículos em diferentes estádios de desenvolvimento e ovócitos.

Cytoskeletal proteins in the follicular wall of normal andcystic ovaries of sows

The expression of cytoskeletal proteins was evaluated immunohistochemically in 36 normal ovaries sampled from 18 sows and 44 cystic ovaries sampled from of 22 sows, was evaluated. All sows had history of reproductive problems, such as infertility or subfertility. The immunohistochemically stained area (IHCSA) was quantified through image analysis to evaluate the expression of these proteins in the follicular wall of secondary, tertiary, and cystic follicles. Cytokeratins (CK) immunoreactivity was strong in the granulosa cell layer (GC) and mild in the theca interna (TI) and externa (TE) of the normal follicles. There was severe reduction of the reaction to CK in the GC in the cystic follicles, mainly in the luteinized cysts. The immunoreactivity for vimentin was higher in the GC from normal and cystic follicles in contrast with the other follicular structures. In the luteinized cysts, the IHCSA for vimentin was significantly higher in TI and in both observed cysts, the labeling was more accentuated in TE. Immunohistochemical detection of desmin and α-SMA was restricted to the TE, without differences between the normal and cystic follicles. The results of the current study show that the development of ovarian cysts in sows is associated to changes in the expression of the cytoskeletal proteins CK and vimentin.

Role of activin, inhibin, and follistatin in the pathogenesis of bovine cystic ovarian disease

Cystic ovarian disease (COD) is an important cause of infertility in dairy cattle. Although many researchers have focused their work on the endocrine changes related to this disease, evidence indicates that intraovarian components play an important role in follicular persistence. Activin, inhibin, and follistatin participate as intraovarian regulatory molecules involved in follicular cell proliferation, differentiation, steroidogenesis, oocyte maturation, and corpus luteum function. Given the importance of these factors in folliculogenesis, we examined the expression and immunolocalization of activin/inhibin βA-subunit, inhibin α-subunit, and follistatin in the ovaries of healthy estrus-synchronized cows and in those of cows with spontaneous or adrenocorticotropic hormone (ACTH)-induced COD. We also studied inhibin B (α βB) levels in serum and follicular fluid. We found an increased expression of the βA-subunit of activin A/inhibin A, the α-subunit of inhibin, and follistatin in granulosa cells of spontaneous follicular cysts by immunohistochemistry, and decreased concentrations of inhibin B (α βB) in the follicular fluid of spontaneous follicular cysts. These results, together with those previously obtained, indicate that the expression of the components of the activin-inhibin-follistatin system is altered. This could lead to multiple alterations in important functions in the ovary like the balance between pro- and anti-apoptotic factors, follicular proliferation/apoptosis, and steroidogenesis, which may contribute to the follicular persistence and endocrine changes found in cattle with COD.

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.

Acute dietary restriction in heifers alters expression of genes regulating exposure and response to gonadotrophins and IGF in dominant follicles

Dietary restriction in growing cattle and severe negative energy balance in lactating cows have been associated with altered gonadotropin secretion, reduced follicle diameter, reduced circulating oestradiol concentrations and anovulation. Therefore, we hypothesised that acute dietary restriction would influence the fate and function of the dominant follicle by altering the expression for genes regulating gonadotrophin and IGF response in ovarian follicles. Newly selected dominant follicles were collected 7-8 days after prostaglandin F(2α) (PGF) administration from heifers (n=25) that were individually fed a diet supplying 1.2 maintenance (M; control, n=8) or 0.4 M (restricted, n=17) for a total duration of 18-19 days. Heifers within 0.4 M were ovulatory (n=11) or anovulatory (n=6) depending on whether the dominant follicle present at PGF ovulated or became atretic following luteolysis. Control animals were all ovulatory. Acute dietary restriction decreased IGF-I (P<0.001) and insulin (P<0.05) in circulation; oestradiol (P<0.01) and IGF-I (P<0.01) in follicular fluid; and mRNA for FSHR (P<0.01) in granulosa cells but increased mRNA for IGFBP2 (P<0.05) in theca cells of the newly selected dominant follicle. However, this only led to anovulation when dietary restriction also decreased mRNA for CYP19A1 (P<0.05), IGF2 (P<0.01) and IGF1R (P<0.05) in granulosa cells and LHCGR (P<0.05) in theca cells of follicles collected from heifers fed 0.4 M. These results suggest that the catabolic environment induced by dietary restriction may ultimately cause anovulation by reducing oestradiol synthesis, FSH-responsiveness and IGF signaling in granulosa, and LH-responsiveness in theca cells of dominant follicles.

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.

In vitro study on the effects of lead and mercury on porcine ovarian granulosa cells

The heavy metals lead (Pb) and mercury (Hg) pose potential risks to sustainability of environment and thus to our future generations. General objective of this in vitro study was to examine the secretory activity of porcine ovarian granulosa cells after Pb and Hg administration and to outline the potential intracellular mediators of its effects. For this purpose, release of insulin-like growth factor I (IGF-I) and steroid hormone progesterone (P(4)), expression of proliferation- related (cyclin B1) and apoptosis-related (caspase-3) peptides was examined in porcine ovarian granulosa cells after heavy metals administration. Obtained data indicate Pb-induced inhibition of IGF-I release at lower doses (0.063 mg/mL and 0.046 mg/mL) by ovarian granulosa cells. However, P(4) release was not influenced by Pb addition, while the expression of cyclin B1 and caspase-3 was induced by Pb addition. These results indicate that Pb can affect the pathway of proliferation and apoptosis of porcine ovarian granulosa cells through intracellular substances such as cyclin B1 and caspase-3. On the other hand, the P(4) release by ovarian granulosa cells of pregnant gilts was stimulated by experimental Pb administration at doses of 0.25 mg/mL and 0.063 mg/mL and experimental Hg administration at doses 0.25 mg/mL and 0.083 mg/mL. P(4) release by ovarian cells of pregnant gilts was not influenced by a combinatory dose of FSH (1.0 ng/mL) + Pb (0.083 mg/mL) + Hg (0.083 mg/mL) but it was inhibited by experimental administration of FSH (10 ng/mL) + Pb (0.25 ng/mL) + Hg (0.25 ng/mL). Possible involvement of heavy metals - Pb and Hg and pituitary hormone FSH, in the regulation of P(4) release by porcine ovarian granulosa cells of pregnant gilts was noted. Data obtained from in vitro studies suggest the dose dependent association of heavy metals administration with the hormonal release by porcine ovarian granulosa cells. This association also depended on pregnancy of the gilts.

An imbalance between apoptosis and proliferation contributes to follicular persistence in polycystic ovaries in rats

BACKGROUND

Cystic ovarian disease is an important cause of infertility that affects bovine, ovine, caprine and porcine species and even human beings. Alterations in the ovarian micro-environment of females with follicular cysts could alter the normal processes of proliferation and programmed cell death in ovarian cells. Thus, our objective was to evaluate apoptosis and proliferation in ovarian cystic follicles in rats in order to investigate the cause of cystic follicle formation and persistence.

METHODS

We compared the number of in situ apoptotic cells by TUNEL assay, expression of active caspase-3 and members of Bcl-2 family by immunohistochemistry; and cell proliferation by the expression of the proliferation markers: PCNA and Ki-67.

RESULTS

The proliferation index was low in granulosa of tertiary and cystic follicles of light exposed rats when compared with tertiary follicles of control animals, while in theca interna only cystic follicles presented low proliferation index when compared with tertiary follicles (p < 0.05). The granulosa of cysts exhibited a similar cell DNA fragmentation to early atretic follicles. In the granulosa and theca interna, active caspase-3 shown similar immunostaining levels in tertiary and cystic follicles (p < 0.05). The granulosa cells presented high expression of Bcl-2, Bcl-xL and Bcl-w in the tertiary and cystic follicles with diminishing intensity in the atretic follicles, except with Bcl-w where the intensity was maintained in the atretic follicles (p < 0.05). The expression of Bax was weak in the healthy and cystic follicles. In the theca interna, Bcl-2 expression was the same as the pattern found in the granulosa; no differences were found between tertiary and cystic follicles from both groups for Bcl-xL and Bcl-w. The expression of Bax in this layer was higher in the tertiary follicles of the treated animals (p < 0.05) while the values for cystic follicles were similar to those in the tertiary follicles of controls. The theca externa showed low expression of the pro and anti-apoptotic proteins.

CONCLUSION

These results show that the combination of weak proliferation indices and low apoptosis observed in follicular cysts, could explain the cause of the slow growth of cystic follicles and the maintenance of a static condition without degeneration, which leads to their persistence. These alterations may be due to structural and functional modifications that take place in these cells and could be related to hormonal changes in animals with this condition.

The role of IGF1 in the in vivo production of bovine embryos from superovulated donors

IGF1 plays an important role in bovine follicular growth, acquisition of oocyte competence and embryo viability. Current data also indicate a critical role for IGF1 in both the ovarian response and the embryo yield following the superovulatory treatments. IGF1 can have either positive or negative effects on embryo viability which is related to the concentration of IGF1 induced by superovulation treatment. These effects impact either on oocyte competence or directly on the embryo. Concentrations in the physiological range appear to result in the production of higher quality embryos, mainly due to the mitogenic and the anti-apoptotic activities of IGF1. However, high superovulatory responses are associated with decreased embryo viability and a concomitant increase in apoptosis. Studies in mice suggest that this increase in apoptosis is related to the downregulation of the IGF1 receptor in the embryo associated with high IGF1 concentrations. Strategies capable of controlling the IGF1 concentrations could be one approach to improve superovulation responses. A range of possible approaches for research within the IGF system in gonadotrophin-stimulated cattle is discussed in this review, including the possible use of superovulated female cattle as an alternative animal experimental model for research on reproductive disorders in humans associated with abnormal IGF1 concentrations.

The role of endocrine insulin-like growth factor-I (IGF-I) in female bovine reproduction

Insulin-like growth factor-I (IGF-I) plays a pivotal role in cattle fertility, acting as a monitoring signal that allows reproductive events to occur when nutritional conditions for successful reproduction are reached. However, endocrine IGF-I is not a predictor of reproductive events, but rather an indirect estimator of the suitability of the animal to achieve the reproductive event in question. Although measuring circulating IGF-I concentrations might not have any clinical application in the cattle industry, endocrine IGF-I screening will continue to be important for the study of interactions between nutrition and reproduction. In addition, endocrine IGF-I screening could be used as an ancillary test for the selection of cattle for high reproductive potential, especially in herds of high genetic merit for milk production, in which a decline in fertility has been identified.