Stimulatory and synergistic effects of luteinising hormone and insulin like growth factor 1 on the secretion of vascular endothelial growth factor and progesterone of cultured bovine granulosa cells

ERK1/2-SOX9/FOXL2 axis regulates ovarian steroidogenesis and favors the follicular-luteal transition

Estradiol and progesterone are the primary sex steroids produced by the ovary. Upon luteinizing hormone surge, estradiol-producing granulosa cells convert into progesterone-producing cells and eventually become large luteal cells of the corpus luteum. Signaling pathways and transcription factors involved in the cessation of estradiol and simultaneous stimulation of progesterone production in granulosa cells are not clearly understood. Here, we decipher that phosphorylated ERK1/2 regulates granulosa cell steroidogenesis by inhibiting estradiol and inducing progesterone production. Down-regulation of transcription factor FOXL2 and up-regulation of SOX9 by ERK underpin its differential steroidogenic function. Interestingly, the incidence of SOX9 is largely uncovered in ovarian cells and is found to regulate FOXL2 along with CYP19A1 and STAR genes, encoding rate-limiting enzymes of steroidogenesis, in cultured granulosa cells. We propose that the novel ERK1/2-SOX9/FOXL2 axis in granulosa cells is a critical regulator of ovarian steroidogenesis and may be considered when addressing pathophysiologies associated with inappropriate steroid production and infertility in humans and animals.

Use of new recombinant proteins for ovarian stimulation in ruminants

Currently, gonadotropin products (follicle stimulating hormone, FSH, and luteinizing hormone, LH) used in animal reproduction are produced by extraction and purification from abattoir-derived pituitary glands. This method, relying on animal-derived materials, carries the potential risk of hormone contamination and pathogen transmission. Additionally, chorionic gonadotropins are extracted from the blood of pregnant mares (equine chorionic gonadotropin; eCG) or the urine of pregnant women (human chorionic gonadotropin; hCG). However, recent advancements have introduced recombinant gonadotropins for assisted animal reproduction therapies. The traditional use of FSH for superovulation has limitations, including labor requirements and variability in superovulation response, affecting the success of in vivo (SOV) and in vitro (OPU/IVEP) embryo production. FSH treatment for superstimulation before OPU can promote the growth of a homogenous follicular population and the recovery of competent oocytes suitable for IVEP procedures. At present, a single injection of a preparation of long-acting bovine recombinant FSH (rFSH) produced similar superovulation responses resulting in the production of good-quality in vivo and in vitro embryos. Furthermore, the treatment with eCG at FTAI protocol has demonstrated its efficacy in promoting follicular growth, ovulation, and P/AI, mainly in heifers and anestrous cows. Currently, treatment with recombinant glycoproteins with eCG-like activity (r-eCG) have shown promising results in increasing follicular growth, ovulation, and P/AI in cows submitted to P4/E2 -based protocols. Bovine somatotropin (bST) is a naturally occurring hormone found in cows. Recombinant bovine somatotropin (rbST), produced through genetic engineering techniques, has shown potential in enhancing reproductive outcomes in ruminants. Treatment with rbST has been found to improve P/IA, increase donor embryo production, and enhance P/ET in recipients. The use of recombinant hormones allows to produce non-animal-derived products, offering several advantages in assisted reproductive technologies for ruminants. This advancement opens up new possibilities for improving reproductive efficiency and success rates in the field of animal reproduction.

Metabolite abundance in bovine preovulatory follicular fluid is influenced by follicle developmental progression post estrous onset in cattle

Introduction: Preovulatory follicle response to the luteinizing hormone (LH) surge leads to metabolic, molecular, and functional changes in the oocyte and somatic follicular cells from the onset of estrus to ovulation. Follicular fluid contains metabolites, miRNAs, proteins, and hormones that are byproducts of follicular metabolism and support cellular processes of oocyte, cumulus, and granulosa constituents. Numerous studies have highlighted the importance of follicular fluid composition to support fertility, but critical gaps exist toward understanding dynamic modifications in the follicular fluid metabolome from estrous onset to ovulation. The hypothesis was that abundance of follicular fluid metabolites is dependent on follicle progression post LH surge and variability in follicular fluid metabolome profiles indicate key processes required for preparation of the follicle and oocyte for optimal fertility. The objective was to generate preovulatory follicular fluid metabolome profiles and discern differences in the metabolome of preovulatory follicular fluid samples collected at onset of estrus, 11 h post estrous onset, and 18 h post estrous onset. Methods: Estrus was synchronized in non-lactating Jersey cows (n=40) and follicular fluid was collected immediately after the first observed standing mount (hr 0) or at approximately h 11 or 18 after the first standing mount. Ultra-High-Performance Liquid Chromatography-High Resolution Mass Spectrometry was performed on preovulatory follicular fluid samples (n = 9 collected at hr 0, 9 at h 11, and 10 at h 18) and a multiple linear model was performed to determine if time post estrous onset impacted metabolite abundance. Results: Metabolites influenced by time post estrous onset were tested for enrichment in KEGG pathways. Ninety metabolites were identified in follicular fluid samples. Twenty metabolites differed in abundance among timepoints post estrous onset (p ≤ 0.05). Pathways corresponding to amino acid and energy metabolism were enriched with metabolites impacted by time post estrous onset (FDR ≤ 0.10). Discussion: Results from the current study indicate early response to the LH surge to increase bioavailability of amino acids and metabolites used by the cumulus and granulosa cells for energy production and shuttled into the oocyte to support meiotic maturation. Such metabolites may later be used by the ovulatory follicle for protein production.

Age-related changes in Folliculogenesis and potential modifiers to improve fertility outcomes - A narrative review

Reproductive aging is characterized by a decline in oocyte quantity and quality, which is directly associated with a decline in reproductive potential, as well as poorer reproductive success and obstetrical outcomes. As women delay childbearing, understanding the mechanisms of ovarian aging and follicular depletion have become increasingly more relevant. Age-related meiotic errors in oocytes are well established. In addition, it is also important to understand how intraovarian regulators change with aging and how certain treatments can mitigate the impact of aging. Individual studies have demonstrated that reproductive pathways involving antimullerian hormone (AMH), vascular endothelial growth factor (VEGF), neurotropins, insulin-like growth factor 1 (IGF1), and mitochondrial function are pivotal for healthy oocyte and cumulus cell development and are altered with increasing age. We provide a comprehensive review of these individual studies and explain how these factors change in oocytes, cumulus cells, and follicular fluid. We also summarize how modifiers of folliculogenesis, such as vitamin D, coenzyme Q, and dehydroepiandrosterone (DHEA) may be used to potentially overcome age-related changes and enhance fertility outcomes of aged follicles, as evidenced by human and rodent studies.

Ovarian, uterine, and luteal vascular perfusions during follicular and luteal phases in the adult cyclic female rabbits with special orientation to their histological detection of hormone receptor

Understanding the does reproductive hemodynamic changes during the estrous cycle is crucial for improving reproductive competence and fertility potential in this species. The objective of this study is to investigate the hemodynamic variations in ovarian (OA) and uterine (UA) arteries, histological and morphometric changes in ovarian and uterine tissues throughout the follicular (FP) and luteal (LP) phases in rabbits and determine estrogen (ER), progesterone (PR) receptors, and vascular endothelial growth factor (VEGF) distributions using immunohistochemistry.

Fourteen adults pluriparous New Zealand rabbits were divided into rabbits at the FP (Day − 1; n = 7) and those at the LP (Day 9; n = 7). Animals were subjected to Doppler, hormonal (estrogen [E2], progesterone [P4], insulin-like growth factor [ILGF], and VEGF), histological, and immunohistochemical analyses. In LP, OA Doppler indices were significantly increased, whereas peak systolic velocity (PSV) was decreased compared with that in FP. UA Doppler indices were significantly decreased in the LP, whereas PSV was increased (P < 0.05). E2 levels were increased in the FP, whereas P4 levels were increased in the LP. The morphometric analysis of uterine tissues during the LP revealed an increase in the mean uterine endometrium length, endometrial connective tissue area percentage (%), endometrial glands number, myometrial area (%) and thickness. Furthermore, ovarian follicles and corpus luteum (CL) displayed strong positive immunoreactivity for ER, PR, and VEGF-A during both phases. The ovarian sections displayed a substantial (P < 0.05) increase in the area % of VEGF-A in the ovarian follicles during FP while in the CL during LP. Conversely, area percentage of VEGF-A immunoreactivity in the uterine luminal and glandular epithelia during the FP and LP revealed no differences. However, the number of VEGF-A–stained blood capillaries revealed an increase during LP than FP. In conclusion, this study demonstrated for the first time the changes in both ovarian and uterine arteries during two different phases of the rabbit cycle in relation to the histo-morphometric analysis and distribution of ER, PR, and VEGF-A, which regulate uterine functions that play a role in reproduction.

Changes in fibroblast growth factor receptors-1c, -2c, -3c, and -4 mRNA in granulosa and theca cells during ovarian follicular growth in dairy cattle

The various fibroblast growth factors (FGF) regulate their function via binding to 4 main FGF receptor (FGFR) subtypes and their splice variants, FGFR1b, FGF1c, FGFR2b, FGFR2c and FGFR3c and FGFR4, but which of these FGFR are expressed in the granulosa (GC) and theca cells (TC), the 2 main cell layers of ovarian follicles, or change during follicular development is unknown. We hypothesized that FGFR1c, FGFR2c and FGFR3c (but not FGFR4) gene expression in GC (but not TC) would change with follicular development. Hence, the objective of this study was to determine if abundance of FGFR1c, FGFR2c, FGFR3c, and FGFR4 mRNA change according to follicular size, steroidogenic status, and days post-ovulation during growth of first-wave dominant follicles in Holstein cattle exhibiting regular estrous cycles. Estrous cycles of non-lactating dairy cattle were synchronized, and ovaries were collected on either d 3 to 4 (n = 8) or d 5 to 6 (n = 8) post-ovulation for GC and TC RNA extraction from small (1-5 mm), medium (5.1 to 8 mm) or large (8.1-18 mm) follicles for real-time PCR analysis. In GC, FGFR1c and FGFR2c mRNA relative abundance was greater in estrogen (E2)-inactive (ie, concentrations of E2 < progesterone, P4) follicles of all sizes than in GC from large E2-active follicles (ie, E2 > P4), whereas FGFR3c and FGFR4 mRNA abundance did not significantly differ among follicle types or days post-estrus. In TC, medium E2-inactive follicles had greater FGFR1c and FGFR4 mRNA abundance than large E2-active and E2-inactive follicles on d 5 to 6 post-ovulation whereas FGFR2c and FGFR3c mRNA abundance did not significantly differ among follicle types or day post-estrus. In vitro experiments revealed that androstenedione increased abundance of FGFR1c, FGFR2c and FGFR4 mRNA in GC whereas estradiol decreased FGFR2c mRNA abundance. Neither androstenedione nor estradiol affected abundance of the various FGFR mRNAs in cultured TC. Taken together, the findings that FGFR1c and FGFR2c mRNA abundance was less in GC of E2-active follicles and FGFR1c and FGFR4 mRNA was greater in TC of medium inactive follicles at late than at early growing phase of the first dominant follicle support an anti-differentiation role for FGF and their FGFR as well as support the idea that steroid-induced changes in FGF and their receptors may regulate selection of dominant follicles in cattle.

Factors affecting the fate of the canine corpus luteum: Potential contributors to pregnancy and non-pregnancy

The fate of the canine corpus luteum (CL) differs from that of other domestic species: beyond the extended luteal regression observed in both pregnant and non-pregnant cycles, active luteolysis is observed only in pregnant dogs. Luteal regression in the absence of pregnancy lacks a luteolytic trigger. The CL lifespan during pregnancy is around 60 days, as long as that of the cyclic CL. Although they are already available in the first half of diestrus, LH and especially prolactin (PRL) play a decisive luteotropic role from approximately day 25 post-ovulation onwards. Nevertheless, many locally-produced factors are orchestrated to ensure a fully functional CL, which in the bitch produces progesterone (P4), 17b-estradiol, and other local regulators. Recently, insulin has been described as another luteotropic factor in this species, able to increase glucose uptake in luteal cells and contribute to steroid biosynthesis. The locally-produced PGE2 is also a potent luteotropic factor in the first half of diestrus, promoting STAR expression, as are also proliferating, vasoactive- and immunomodulatory factors. These, in turn, all contribute to the formation and maintenance of the canine CL. Meanwhile PGF2a, produced by the utero-placental compartment, participates actively in triggering pre-partum luteolysis. Cytokines play different roles, either contributing as luteotropic or as acute inflammation molecules. So far, the one clinically most efficient mechanism of interrupting a pregnancy in the dog is to block P4 receptors, using an antigestagen (e.g., aglepristone) in the second half of diestrus. To enhance the chances of pregnancy, however, several luteotropic factors could be used.

Roadmap to pregnancy in the first 7 days post-insemination in the cow: Immune crosstalk in the corpus luteum, oviduct, and uterus

The first 7 days post-insemination are critical for establishment of pregnancy. The pre-ovulatory luteinizing hormone (LH) surge induces ovulation through disruption of the follicle structure that elucidates pro-inflammatory (Th1) responses. Various types of immune cells are recruited into the corpus luteum (CL) to regulate luteal angiogenesis and progesterone (P4) secretion into the circulation to establish pregnancy. The active sperm-uterine crosstalk also induces Th1 responses, mainly via Toll-like receptor (TLR) 2/4 signaling pathway in vitro. The endometrial glands serve as sensors for sperm signals, which trigger Th1 responses. Conversely, the sperm-oviduct binding generates anti-inflammatory (Th2) responses to support sperm survival until fertilization. It is well-established that embryo-maternal crosstalk starts after the embryo hatches out from the zona pellucida (ZP). However most recently, it was shown that the 16-cell stage bovine embryo starts to secrete interferon-tau (IFNT) that induces Th2 immune responses in the oviduct. Once developing embryos descend into the uterine horn, they induce Th2 responses with interferon-stimulated genes (ISGs) expression in the uterine epithelium and local immune cells mainly via IFNT release. Likewise, multiple embryos in the uterus of superovulated donor cows on D7 post-insemination induce Th2 immune responses with ISGs expressions in circulating immune cells. These findings strongly suggest that the maternal immune system reacts to the embryo during the first 7 days post-insemination to induce fetal tolerance. It became evident that the innate immunity of the developing CL, oviduct, and uterus works together to provide optimal conditions for fertilization and early embryonic development during the first 7 days post-insemination.

Contribution of the immune system to follicle differentiation, ovulation and early corpus luteum formation

Much of what we know about the involvement of the immune system in periovulatory follicle differentiation, ovulation and subsequent formation of the corpus luteum in cattle is drawn from the findings of studies in several mammalian livestock species. By integrating published histological data from cattle, sheep and pigs and referring back to the more comprehensive knowledge bank that exists for mouse and humans we can sketch out the key cells of the immune system and the cytokines and growth factors that they produce that are involved in follicle differentiation and luteinization, ovulation and early follicle development. These contributions are reviewed and the key findings, discussed.

Interferon-Tau Exerts Direct Prosurvival and Antiapoptotic Actions in Luteinized Bovine Granulosa Cells

Interferon-tau (IFNT), serves as a signal to maintain the corpus luteum (CL) during early pregnancy in domestic ruminants. We investigated here whether IFNT directly affects the function of luteinized bovine granulosa cells (LGCs), a model for large-luteal cells. Recombinant ovine IFNT (roIFNT) induced the IFN-stimulated genes (ISGs; MX2, ISG15, and OAS1Y). IFNT induced a rapid and transient (15–45 min) phosphorylation of STAT1, while total STAT1 protein was higher only after 24 h. IFNT treatment elevated viable LGCs numbers and decreased dead/apoptotic cell counts. Consistent with these effects on cell viability, IFNT upregulated cell survival proteins (MCL1, BCL-xL, and XIAP) and reduced the levels of gamma-H2AX, cleaved caspase-3, and thrombospondin-2 (THBS2) implicated in apoptosis. Notably, IFNT reversed the actions of THBS1 on cell viability, XIAP, and cleaved caspase-3. Furthermore, roIFNT stimulated proangiogenic genes, including FGF2, PDGFB, and PDGFAR. Corroborating the in vitro observations, CL collected from day 18 pregnant cows comprised higher ISGs together with elevated FGF2, PDGFB, and XIAP, compared with CL derived from day 18 cyclic cows. This study reveals that IFNT activates diverse pathways in LGCs, promoting survival and blood vessel stabilization while suppressing cell death signals. These mechanisms might contribute to CL maintenance during early pregnancy.

Hormonal regulation of vascular endothelial growth factor A (VEGFA) gene expression in granulosa and theca cells of cattle1

Vascular endothelial growth factor A (VEGFA) stimulates angiogenesis and is associated with increased vascularity in ovarian follicles of cattle. The objectives of this study were to investigate the developmental and hormonal regulation of VEGFA expression in ovarian granulosa and theca cells (TC) of cattle. Bovine ovaries were collected from a local slaughterhouse and granulosa cells (GC) and TC were collected from small (SM; 1 to 5 mm) and large (LG; 8 to 20 mm) follicles. Cells were collected fresh or cultured in serum-free medium and treated with various factors that regulate angiogenesis and follicular development. RNA was collected for analysis of VEGFA mRNA abundance via quantitative PCR. In SM-follicle GC (SMGC), prostaglandin E2 (PGE2) and FSH decreased (P < 0.05) VEGFA mRNA abundance by 30 to 46%, whereas in LG-follicle GC (LGGC), PGE2 and FSH were without effect (P > 0.10). In SMGC, dihydrotestosterone (DHT), sonic hedgehog (SHH), and growth differentiation factor-9 (GDF9) decreased (P < 0.05) VEGFA expression by 30 to 40%. Fibroblast growth factor-9 (FGF9) and estradiol (E2) were without effect (P > 0.10) on VEGFA mRNA in both SMGC and LGGC, whereas progesterone increased (P < 0.05) VEGFA mRNA in LGGC but had no effect in LGTC. Bone morphogenetic protein-4 (BMP4), LH, and FGF9 increased (P < 0.05) abundance of VEGFA mRNA by 1.5- to 1.9-fold in LGTC. Insulin-like growth factor-1 (IGF1) was without effect (P > 0.10) on VEGFA mRNA in both TC and GC. An E2F transcription factor inhibitor, HLM0064741 (E2Fi), dramatically (i.e., 8- to 13-fold) stimulated (P < 0.01) the expression of VEGFA mRNA expression in both SMGC and LGTC. Abundance of VEGFA mRNA was greater (P < 0.05) in LGGC and SMGC than in LGTC. Also, SMTC had greater (P < 0.05) abundance of VEGFA mRNA than LGTC. In conclusion, VEGFA mRNA abundance was greater in GC than TC, and VEGFA expression decreased in TC during follicle development. Some treatments either suppressed, stimulated, or had no effect on VEGFA expression depending on the cell type. The inhibition of E2F transcription factors had the greatest stimulatory effect of all treatments evaluated, and thus, E2Fs may play an important role in regulating angiogenesis during follicle growth in cattle.

Prostaglandins in Superovulation Induced Bovine Follicles During the Preovulatory Period and Early Corpus Luteum

The aim of this study was to characterize the regulation pattern of prostaglandin family members namely prostaglandin F2alpha (PTGF), prostaglandin E2 (PTGE), their receptors (PTGFR, PTGER2, PTGER4), cyclooxygenase 2 (COX-2), PTGF synthase (PTGFS), and PTGE synthase (PTGES) in the bovine follicles during preovulatory period and early corpus luteum (CL). Ovaries containing preovulatory follicles or CL were collected by transvaginal ovariectomy (n = 5 cows/group), and the follicles were classified: (I) before GnRH treatment; (II) 4 h after GnRH; (III) 10 h after GnRH; (IV) 20 h after GnRH; (V) 25 h after GnRH, and (VI) 60 h after GnRH (early CL). In these samples, the concentrations of progesterone (P4), estradiol (E2), PTGF and PTGE were investigated in the follicular fluid (FF) by validated EIA. Relative mRNA abundance of genes encoding for prostaglandin receptors (PTGFR, PTGER2, PTGER4), COX-2, PTGFS and PTGES were quantified by RT-qPCR. The localization of COX-2 and PTGES were investigated by established immunohistochemistry in fixed follicular and CL tissue samples. The high E2 concentration in the FF of the follicle group before GnRH treatment (495.8 ng/ml) and during luteinizing hormone (LH) surge (4 h after GnRH, 574.36 ng/ml), is followed by a significant (P<0.05) downregulation afterwards with the lowest level during ovulation (25 h after GnRH, 53.11 ng/ml). In contrast the concentration of P4 was very low before LH surge (50.64 mg/ml) followed by a significant upregulation (P < 0.05) during ovulation (537.18 ng/ml). The mRNA expression of COX-2 increased significantely (P < 0.05) 4 h after GnRH and again 20 h after GnRH, followed by a significant decrease (P < 0.05) after ovulation (early CL). The mRNA of PTGFS in follicles before GnRH was high followed by a continuous and significant downregulation (P < 0.05) afterwards. In contrast, PTGES mRNA abundance increased significantely (P < 0.05) in follicles 20 h after GnRH treatment and remained high afterwards. The mRNA abundance of PTGFR, PTGER2, and PTGER4 in follicles before GnRH was high, followed by a continuous and significant down regulation afterwards and significant increase (P < 0.05) only after ovulation (early CL). The low concentration of PTGF (0.04 ng/ml) and PTGE (0.15 ng/ml) in FF before GnRH, increased continuously in follicle groups before ovulation and displayed a further significant and dramatic increase (P < 0.05) around ovulation (101.01 ng/ml, respectively, 484.21 ng/ml). Immunohistochemically, the granulosa cells showed an intensive signal for COX-2 and PTGES in follicles during preovulation and in granulosa-luteal cells of the early CL. In conclusion, our results indicate that the examined bovine prostaglandin family members are involved in the local mechanisms regulating final follicle maturation and ovulation during the folliculo-luteal transition and CL formation.

Effects of reproductive season on embryo development in the buffalo

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

The Role of Growth Hormone on Ovarian Functioning and Ovarian Angiogenesis

Although not yet well-understood, today it is clear that Growth Hormone (GH) exerts a relevant role in the regulation of ovulation and fertility; in fact, fertility is lower in women with GH deficiency (GHD), and GH receptors (GHR) and GH mRNA have been found in the ovary since the onset of follicular development in humans. However, despite the strong evidence of GH in the regulation of fertility, many aspects of GH actions at this level are still not well-established, and it is likely that some controversial data depend on the species analyzed, the dose of the hormone and the duration of use of GH. Folliculogenesis, ovulation, and corpus luteum formation and maintenance are processes that are critically dependent on angiogenesis. In the ovary, new blood vessel formation facilitates oxygen, nutrients, and hormone substrate delivery, and also secures transfer of different hormones to targeted cells. Some growth factors and hormones overlap their actions in order to control the angiogenic process for fertility. However, we still know very little about the factors that play a critical role in the vascular changes that occur during folliculogenesis or luteal regression. To promote and maintain the production of VEGF-A in granulosa cells, the effects of local factors such as IGF-I and steroids are needed; that VEGF-A-inducing effect cannot be induced by luteinizing hormone (LH) or chorionic gonadotropin (CG) alone. As a result of the influences that GH exerts on the hypothalamic-pituitary-gonadal axis, facilitating the release of gonadotropins, and given the relationship between GH and local ovarian factors such as VEGF-A, FGF-2, IGF-1, or production of sex steroids, we assume that GH has to be a necessary factor in ovarian angiogenesis, as it happens in other vascular beds. In this review we will discuss the actions of GH in the ovary, most of them likely due to the local production of the hormone and its mediators.

Expression of insulin-like growth factor 1 and its receptor in preovulatory follicles and in the corpus luteum in the bitch

In the bitch, ovarian follicular and corpus luteum (CL) development and function are regulated by gonadotropins as well as local factors, the role of which is especially important during the early CL phase of relative gonadotrophic independence. We assumed that insulin-like growth factor 1 (IGF1) has a paracrine/autocrine regulatory role in ovarian follicular and luteal function in the dog. To address our hypothesis, we studied gene and protein expression of IGF1 and its receptor (IGF1R) in preovulatory follicles and in the CL of pregnant and non-pregnant dogs, and following antigestagen (aglepristone, progesterone receptor blocker) treatment in mid-gestation. Ovaries in the follicular phase were collected from five bitches. CL were collected on pregnancy Days 8-12 (pre-implantation), 18-25 (post-implantation), 35-40 (mid-gestation), at prepartum luteolysis, and 24 h and 72 h after aglepristone treatment in mid-gestation (n = 3-5 per group). From non-pregnant bitches, CL were collected on Days 5, 15, 25, 35, 45, 65 after ovulation (n = 4-5 per group). Semi-quantitative real-time (TaqMan) PCR and immunohistochemistry were applied. IGF1 immunostaining in preovulatory follicles seemed stronger in theca interna than granulosa cells. IGF1R signals appeared more intense in granulosa cells at the apical part of mural folds. In pregnant dogs, luteal IGF1 mRNA expression decreased significantly from pre-implantation to prepartum luteolysis, while IGF1R expression increased at prepartum luteolysis. Aglepristone treatment in mid-gestation had no effect on IGF1 and IGF1R mRNA levels. In non-pregnant bitches, highest IGF1 mRNA concentrations were found in the early CL and decreased by Days 45 and 65, while IGF1R expression did not change. In the CL of pregnant bitches, signals for IGF1 and IGF1R in luteal cells were strongest at pre- and post-implantation and weakest at prepartum luteolysis. IGF1 and IGF1R immunostaining was also detected in macrophages and in blood vessels. In conclusion, IGF1 may have a paracrine or autocrine role in granulosa and theca interna cells in preovulatory follicles. As IGF1 was highest represented in early luteal stages in pregnant and non-pregnant bitches, this may support a role for IGF1 in steroid synthesis, angiogenesis and cell proliferation as well as in immune function in the early canine CL. The unaffected mRNA levels after aglepristone treatment may support that IGF1 is not directly regulated by local progesterone in an auto- or paracrine manner.

Systemic and intrafollicular components of follicle selection in mares

Mares are superb models for study of follicle selection owing to similarities between mares and women in relative follicle diameters at specific events during the follicular wave and follicle accessibility for experimental sampling and manipulation. Usually, only 1 major follicular wave with a dominant follicle (DF) greater than 30 mm develops during the 22 to 24 d of the equine estrous cycle and is termed the primary or ovulatory wave. A major secondary wave occasionally (25%) develops early in the cycle. Follicles of the primary wave emerge at 6 mm on day 10 or 11 (day 0 = ovulation). The 2 largest follicles begin to deviate in diameter on day 16 when the future DF and largest subordinate follicle (SF) are 23 mm and 20 mm, respectively. The deviation process begins the day before diameter deviation as indicated in the future DF but not in the future SF by (1) increase in prominence of an anechoic layer and vascular perfusion of the wall and (2) increase in follicular-fluid concentrations of IGF1, vascular endothelial growth factor, estradiol, and inhibin-A. A systemic component of the deviation process is represented by suppression of circulating FSH from secretion of inhibin and estradiol from the developing DF. Production of inhibin is stimulated by IGF1 and LH, and estradiol is stimulated by LH and not by IGF1 in mares. A local intrafollicular component involves the production of IGF1, which apparently increases the responsiveness of the future DF to FSH. The roles of the IGF system have been well studied in mares, but the effect of IGF1 on increasing the sensitivity of the follicle cells to FSH is based primarily on studies in other species. The greater response of the future DF than the SF to the low concentrations of FSH is the essence of selection. During the common growth phase that precedes deviation, diameter of the 2 largest follicles increases in parallel on average when normalized to emergence or retrospectively to deviation. Study of individual waves indicates that (1) the 2 follicles change ranks (relative diameters) during the common growth phase in about 30% of primary waves and (2) after ablation of 1, 2, or 3 of the largest follicles at the expected beginning of deviation, the next largest retained follicle becomes the DF indicating that several follicles have the capacity for dominance; therefore, it is proposed that the deviation process represents the entire mechanism of follicle selection in mares.

A potential role of endoplasmic reticulum stress in development of ovarian hyperstimulation syndrome

Vascular endothelial growth factor A (VEGFA) is crucial for ovarian angiogenesis, but its excess production induces ovarian hyperstimulation syndrome (OHSS). The aim of this study was to determine whether endoplasmic reticulum (ER) stress regulates VEGFA expression in granulosa cells, and whether its activation is involved in OHSS development. The expression of the spliced form of X-box-binding protein 1 [XBP1(S)], induced by ER stress, in cumulus cells from OHSS patients was higher than that in cumulus cells from non-OHSS patients. The ER stress inducer tunicamycin increased human chorionic gonadotropin-induced VEGFA production in human granulosa cells through the induction of XBP1(S), and pretreatment with the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) abrogated the effect of tunicamycin. In OHSS model rats, TUDCA administration prevented the OHSS development, reducing ovarian VEGFA production. Our findings suggest ER stress upregulates hCG-induced VEGFA production in granulosa cells, indicating that ER stress might be involved in OHSS development.

Insulin Receptor Substrate 1, the Hub Linking Follicle-stimulating Hormone to Phosphatidylinositol 3-Kinase Activation

The ubiquitous phosphatidylinositol 3-kinase (PI3K) signaling pathway regulates many cellular functions. However, the mechanism by which G protein-coupled receptors (GPCRs) signal to activate PI3K is poorly understood. We have used ovarian granulosa cells as a model to investigate this pathway, based on evidence that the GPCR agonist follicle-stimulating hormone (FSH) promotes the protein kinase A (PKA)-dependent phosphorylation of insulin receptor substrate 1 (IRS1) on tyrosine residues that activate PI3K. We report that in the absence of FSH, granulosa cells secrete a subthreshold concentration of insulin-like growth factor-1 (IGF-1) that primes the IGF-1 receptor (IGF-1R) but fails to promote tyrosine phosphorylation of IRS1. FSH via PKA acts to sensitize IRS1 to the tyrosine kinase activity of the IGF-1R by activating protein phosphatase 1 (PP1) to promote dephosphorylation of inhibitory Ser/Thr residues on IRS1, including Ser(789). Knockdown of PP1β blocks the ability of FSH to activate PI3K in the presence of endogenous IGF-1. Activation of PI3K thus requires both PKA-mediated relief of IRS1 inhibition and IGF-1R-dependent tyrosine phosphorylation of IRS1. Treatment with FSH and increasing concentrations of exogenous IGF-1 triggers synergistic IRS1 tyrosine phosphorylation at PI3K-activating residues that persists downstream through protein kinase B (AKT) and FOXO1 (forkhead box protein O1) to drive synergistic expression of genes that underlies follicle maturation. Based on the ability of GPCR agonists to synergize with IGFs to enhance gene expression in other cell types, PP1 activation to relieve IRS1 inhibition may be a more general mechanism by which GPCRs act with the IGF-1R to activate PI3K/AKT.

Ghrelin Decreases Angiogenesis, HIF-1α and VEGF Protein Levels in Chronic Hypoxia in Lung Tissue of Male Rats

PURPOSE

Hypoxia is a condition of decreased availability of oxygen. When cells are exposed to a low oxygen environment, they impel the hypoxia responses to adapt to new situation. The hypoxia response leads to the activation of various cellular signaling pathways. The aim of this study was to evaluate the effect of ghrelin on angiogenesis, Hypoxia-Inducible-Factor-1α (HIF-1) and Vascular endothelial growth factor (VEGF) levels in normobaric hypoxia situation.

METHODS

Twenty four animals were divided into 4 groups (n=6): control (C), ghrelin (Gh), hypoxia (H), and hypoxic animals that received ghrelin (H+Gh). Hypoxia (11%) was induced by an Environmental Chamber System GO2 Altitude. Animals in ghrelin groups received a subcutaneous injection of ghrelin (150 μg/kg/day) for 14 days.

RESULTS

Our results showed that hypoxia significantly (p<0.05) increased angiogenesis without any significant changes on HIF-1 and VEGF levels, whereas ghrelin significantly (p<0.05) decreased angiogenesis, expression of HIF-1 and VEGF in this condition. Ghrelin administration did not show any significant changes in normal conditions.

CONCLUSION

Ghrelin had no effect on angiogenesis, expression of HIF-1 and VEGF in normal oxygen conditions but it reduced angiogenesis process in lung tissue with reducing the level of HIF and VEGF in hypoxic condition. Therefore, effect of ghrelin on angiogenesis could be related to blood oxygen level.

Innate immunity and inflammation of the bovine female reproductive tract in health and disease

Mammalian reproductive physiology and the development of viviparity co-evolved with inflammation and immunity over millennia. Many inflammatory mediators contribute to paracrine and endocrine signalling, and the maintenance of tissue homeostasis in the female reproductive tract. However, inflammation is also a feature of microbial infections of the reproductive tract. Bacteria and viruses commonly cause endometritis, perturb ovarian follicle development and suppress the endocrine activity of the hypothalamus and pituitary in cattle. Innate immunity is an evolutionary ancient system that orchestrates host cell inflammatory responses aimed at eliminating pathogens and repairing damaged tissue. Pattern recognition receptors on host cells bind pathogen-associated molecular patterns and damage-associated molecular patterns, leading to the activation of intracellular MAPK and NFκB signalling pathways and the release of inflammatory mediators. Inflammatory mediators typically include the interleukin cytokines IL1β and IL6, chemokines such as IL8, interferons and prostaglandins. This review outlines the mechanisms of inflammation and innate immunity in the bovine female reproductive tract during health and disease condition.

Luteinizing hormone, insulin like growth factor-1, and epidermal growth factor stimulate vascular endothelial growth factor production in cultured bubaline granulosa cells

The objective of this study was to characterize in vitro expression and secretion of vascular endothelial growth factor (VEGF) in bubaline granulosa cells (GC), grown in serum containing media supplemented with luteinizing hormone (LH), insulin like growth factor-1 (IGF-1), and epidermal growth factor (EGF) at three different doses and time durations. GCs were collected from ovarian follicles of varying diameters [Gp-I (small), 4-6 mm; Gp-II (medium), 7-9 mm; Gp-III (large), 10-13 mm; Gp-IV (pre-ovulatory), >13 mm]. In general, each of the three treatments resulted in a dose as well as time dependent increase in the mRNA expression and secretion of VEGF in the cultured GCs of Gp-IV follicles. These results were well supported by our observations on immunocytochemistry in Gp IV granulosa cell culture (GCC). We also looked into the expression dynamics of an anti-apoptotic factor--proliferating cellular antigen (PCNA) and a pro-apoptotic factor--Bcl-2-associated X protein (BAX) in GCs of Gp IV follicles on treatments with LH, IGF-1, and EGF to evaluate their cytoprotective/anti-apoptotic property. Relative expressions of PCNA and BAX showed a mutually opposite trend with the PCNA expression increasing and BAX expression decreasing with increase in dose and time to reach the zenith (P<0.05) and nadir (P<0.05) at the highest dose(s) at the maximum time duration (72 h) for PCNA and BAX respectively on treatment with all the three factors. Thus, it can be concluded that LH, IGF-1, and EGF treatments have a cytoprotective/anti-apoptotic effect and stimulate VEGF production in granulosa cells of bubaline pre-ovulatory follicles.

CELL BIOLOGY SYMPOSIUM: perspectives: possible roles of polymorphonuclear neutrophils in angiogenesis and lymphangiogenesis in the corpus luteum during development and early pregnancy in ruminants

The establishment of pregnancy requires well-balanced regulation of the endocrine and immune systems and involves interactions among the conceptus, oviduct-uterus, and corpus luteum (CL). In particular, a rapid increase in plasma progesterone during the first week after ovulation is critical for the growth of the conceptus and successful pregnancy in cattle. Events involved in maternal recognition of pregnancy (MRP) may commence within 1 wk from AI, when interferon-stimulated gene expression in circulating polymorphonuclear neutrophils (PMN) increases in pregnant cows. To regulate optimal endocrine conditions within this time, the CL must develop rapidly, with active angiogenesis and lymphangiogenesis. The major angiogenic factors, vascular endothelial growth factor and fibroblast growth factor 2, contribute to the development of the CL but may also act as chemoattractants for PMN. Indeed, the number of PMN is greatest in the new CL, where PMN together with IL-8 induce active angiogenesis and lymphangiogenesis. During MRP, the conceptus secretes interferon tau (IFNT), which prevents CL regression by inhibiting luteolytic release of PGF2α from uterine endometrium. In addition, IFNT and PGE2 reach the CL and may contribute to desensitizing the CL to the luteolytic effects of PGF2α. In the bovine CL, lymphangiogenesis, stimulated by IFNT, may occur during MRP, and thus a shift of local immunity might occur at this timing. The aforementioned evidence supports the possible involvement of PMN in the establishment of pregnancy via CL regulation. Further investigation could expand our understanding of the communication between zygotes, PMN, and reproductive organs during early pregnancy. This should provide new insight into the contribution of neutrophils to CL function and immune tolerance during early pregnancy in ruminants.

Impact of angiogenic and innate immune systems on the corpus luteum function during its formation and maintenance in ruminants

The corpus luteum (CL) is formed from an ovulated follicle, and grows rapidly to secrete progesterone (P4) thereby supporting implantation and maintenance of pregnancy. It is now evident that angiogenesis is necessary to form the structure of the developing CL as well as to acquire the steroidogenic capacity to secrete large amounts of P4. It is of interest that the increases in CL size, plasma P4 concentration and luteal blood flow are occurring in parallel during the first seven days after ovulation. Angiogenic factors, such as vascular endothelial growth factor-A (VEGFA) and basic fibroblast growth factor (FGF2), play a central role in promoting cell proliferation and angiogenesis in the developing CL. Angiopoietins regulate the stability of blood vessels, which directly affects angiogenesis or angiolysis via angiogenic factors. Vasohibin-1 is a novel negative feedback regulator, which inhibits VEGF-based vasculogenesis. It became evident that the immune cells, i.e., macrophages, eosinophils and neutrophils are recruited into the CL - using the innate immune system - just after ovulation which is accompanied by bleeding. The immune cells support active angiogenesis and thus the growth of the CL. In cows, the lymphatic system, but not blood vascular system, is reconstituted during early pregnancy, and embryonic trophoblast-derived interferon tau could play a crucial role in inducing lymphangiogenesis. This novel phenomenon may support a maternal recognition of pregnancy in shifting the local systems in such a way that they ensure a long-term supply of P4 over the period of pregnancy. Overall, the current findings support the concept that several major components involved in the regulation of the CL development and maintenance overlap in stimulating steroidogenesis, angiogenesis, vascular function and the innate immune system.

Qualidade do corpo lúteo e do embrião de ovelhas Santa Inês superovuladas com FSH associado à rbST

Avaliou-se o efeito da somatotropina bovina recombinante (rbST) sobre a qualidade do corpo lúteo e do embrião e sobre a concentração de progesterona (P4), em ovelhas da raça Santa Inês doadoras de embriões. Foram utilizadas 13 doadoras, distribuídas aleatoriamente em dois grupos, G1 (n=7) e G2 (n=6). Em ambos os grupos, as doadoras foram sincronizadas com implante vaginal por 14 dias, receberam 100µg de PGF2α (Ciosin®) no sétimo dia e foram superovuladas, a partir do 12º dia, com 250UI de FSH (Folltopin-V®) em seis doses decrescentes. No dia da retirada do implante, as doadoras do G2 receberam 125mg de rbST (Boostin®) e foram cobertas por macho Santa Inês a cada 12 horas até o final do estro. No sexto dia após a primeira cobrição, foram avaliadas, por laparoscopia, a resposta superovulatória e a quantidade e a qualidade dos corpos lúteos. Após as avaliações, as colheitas embrionárias foram realizadas por laparotomia. A administração da rbST no protocolo de superovulação promoveu aumento significativo (P<0,05) no número de corpos lúteos do tipo I (9,00 x 5,28) e na qualidade embrionária (4,33 x 2,00).

Differential gene expression of granulosa cells after ovarian superstimulation in beef cattle

Microarray analysis was used to compare the gene expression of granulosa cells from dominant follicles with that of those after superstimulatory treatment. Cows were allocated randomly to two groups (superstimulation and control, n=6/group). A new follicular wave was induced by ablation of follicles ≥5 mm in diameter, and a progesterone-releasing device controlled internal drug release (CIDR) was placed in the vagina. The superstimulation group was given eight doses of 25 mg FSH at 12-h intervals starting from the day of wave emergence (day 0), whereas the control group was not given FSH treatment. Both groups were given prostaglandin F2α twice, 12 h apart, on day 3 and the CIDR was removed at the second injection; 25 mg porcine luteinizing hormone (pLH) was given 24 h after CIDR removal, and cows were ovariectomized 24 h later. Granulosa cells were collected for RNA extraction, amplification, and microarray hybridization. A total of 190 genes were downregulated and 280 genes were upregulated. To validate the microarray results, five genes were selected for real-time PCR (NTS, FOS, THBS1, FN1, and IGF2). Expression of four genes increased significantly in the three different animals tested (NTS, FOS, THBS1, and FN1). The upregulated genes are related to matrix remodeling (i.e. tissue proliferation), disturbance of angiogenesis, apoptosis, and oxidative stress response. We conclude that superstimulation treatment i) results in granulosa cells that lag behind in maturation and differentiation (most of the upregulated genes are markers of the follicular growth stage), ii) activates genes involved with the NFE2L2 oxidative stress response and endoplasmic reticulum stress response, and iii) disturbs angiogenesis.

Cytokines and angiogenesis in the corpus luteum

In adults, physiological angiogenesis is a rare event, with few exceptions as the vasculogenesis needed for tissue growth and function in female reproductive organs. Particularly in the corpus luteum (CL), regulation of angiogenic process seems to be tightly controlled by opposite actions resultant from the balance between pro- and antiangiogenic factors. It is the extremely rapid sequence of events that determines the dramatic changes on vascular and nonvascular structures, qualifying the CL as a great model for angiogenesis studies. Using the mare CL as a model, reports on locally produced cytokines, such as tumor necrosis factor α (TNF), interferon gamma (IFNG), or Fas ligand (FASL), pointed out their role on angiogenic activity modulation throughout the luteal phase. Thus, the main purpose of this review is to highlight the interaction between immune, endothelial, and luteal steroidogenic cells, regarding vascular dynamics/changes during establishment and regression of the equine CL.

Fibroblast growth factor 2 induces the precocious development of endothelial cell networks in bovine luteinising follicular cells

The transition from follicle to corpus luteum represents a period of intense angiogenesis; however, the exact roles of angiogenic factors during this time remain to be elucidated. Thus, the roles of vascular endothelial growth factor (VEGF) A, fibroblast growth factor (FGF) 2 and LH in controlling angiogenesis were examined in the present study. A novel serum-free luteinising follicular angiogenesis culture system was developed in which progesterone production increased during the first 5 days and was increased by LH (P < 0.01). Blockade of signalling from FGF receptors (SU5402; P < 0.001) and, to a lesser extent, VEGF receptors (SU1498; P < 0.001) decreased the development of endothelial cell (EC) networks. Conversely, FGF2 dose-dependently (P < 0.001) induced the precocious transition of undeveloped EC islands into branched networks associated with a twofold increase in the number of branch points (P < 0.001). In contrast, VEGFA had no effect on the area of EC networks or the number of branch points. LH had no effect on the area of EC networks, but it marginally increased the number of branch points (P < 0.05) and FGF2 production (P < 0.001). Surprisingly, progesterone production was decreased by FGF2 (P < 0.01) but only on Day 5 of culture. Progesterone production was increased by SU5402 (P < 0.001) and decreased by SU1498 (P < 0.001). These results demonstrate that FGF and VEGF receptors play a fundamental role in the formation of luteal EC networks in vitro, which includes a novel role for FGF2 in induction of EC sprouting.

Progesterone and insulin-like growth factor I levels in blood of Boer goats during puerperium out-of-season in a mild climate region

The aims of this study were to compare insulin-like growth factor-I (IGF-I) and progesterone concentrations as indicators of cycle activity in the blood of Boer goats during puerperium out-of-season in mild climate conditions and to investigate the influence of parity and litter size on the concentration of IGF-I and progesterone in serum during the study period. Twenty Boer (8 primiparous and 12 pluriparous) goats were examined in this study. Blood samples were taken every 4 days starting on the 3rd day and up to the 40th day of puerperium. IGF-I and progesterone (P4) blood levels were determined using radio immune assay (RIA). Results indicated cyclic ovarian activity outside the breeding season in 18 of 20 Boer goats. IGF-I levels in blood sera followed oestrus and cyclic ovarian activity. IGF-I concentrations correlated significantly with P4 concentrations. The IGF-I peak preceded the P4 peak by approximately 8 days in cycling goats. IGF-I and P4 blood levels were not influenced by parity or litter size. Changes in blood serum P4 and IGF-I concentrations levels during puerperal period can assist in the evaluation of reproductive status of goats.

Expression of vascular endothelial growth factor A during ligand-induced down-regulation of luteinizing hormone receptor in the ovary

Vascular endothelial growth factor A (VEGF-A) is one of the most important regulators of ovarian angiogenesis. In this study, we examined the temporal relationship between VEGF-A and luteinizing hormone receptor (LHR) mRNA expression during ligand-induced down-regulation of LHR. Immature female rats were treated with pregnant mare's serum gonadotropin followed by 25 IU hCG 56 h later (day 0). On day 5, treatment with hCG (50 IU) to down-regulate LHR showed a temporal decrease in VEGF-A mRNA and protein levels in parallel with decreasing LHR mRNA. This effect was specific since the expression of CYP11A1 mRNA showed no decline. Examination of VEGF-A mRNA expression, using in situ hybridization histochemistry with (35)S-labeled antisense VEGF-A mRNA probe, showed intense signal in the corpora lutea on day 5. Treatment with 50 IU hCG to down-regulate LHR mRNA showed a decline in the intensity of VEGF-A mRNA in the corpora lutea. VEGF-A mRNA expression returned to control level 53 h later when the expression of LHR mRNA also recovered. These results show that the transient down-regulation of VEGF-A mRNA and protein closely parallels the ligand-induced down-regulation of LHR mRNA. The present study establishes a close association between VEGF-A and LHR mRNA expression, suggesting the possibility that VEGF-A-induced vascularization of the ovary is dictated by the expression of LHR and this might play a regulatory role in ovarian physiology.

Workflow comparison for label-free, quantitative secretome proteomics for cancer biomarker discovery: method evaluation, differential analysis, and verification in serum

The cancer cell secretome has emerged as an attractive subproteome for discovery of candidate blood-based biomarkers. To choose the best performing workflow, we assessed the performance of three first-dimension separation strategies prior to nanoLC-MS/MS analysis: (1) 1D gel electrophoresis (1DGE), (2) peptide SCX chromatography, and (3) tC2 protein reversed phase chromatography. 1DGE using 4-12% gradient gels outperformed the SCX and tC2 methods with respect to number of identified proteins (1092 vs 979 and 580, respectively), reproducibility of protein identification (80% vs 70% and 72%, respectively, assessed in biological N = 3). Reproducibility of protein quantitation based on spectral counting was similar for all 3 methods (CV: 26% vs 24% and 24%, respectively). As a proof-of-concept of secretome proteomics for blood-based biomarker discovery, the gradient 1DGE workflow was subsequently applied to identify IGF1R-signaling related proteins in the secretome of mouse embryonic fibroblasts transformed with human IGF1R (MEF/Toff/IGF1R). VEGF and osteopontin were differentially detected by LC-MS/MS and verified in secretomes by ELISA. Follow-up in serum of mice bearing MEF/Toff/IGF1R-induced tumors showed an increase of osteopontin levels paralleling tumor growth, and reduction in the serum of mice in which IGF1R expression was shut off and tumor regressed.

The expression of angiogenic growth factors and their receptors in ovarian follicles throughout the estrous cycle in the ewe

Healthy follicles are highly vascularized whereas those undergoing atresia have poor vascularity, suggesting a relationship between follicular vascularization and follicular function. Vascularization is regulated by angiogenic factors, and among them vascular endothelial growth factor (VEGF) and angiopoietin-Tie (Ang-Tie) systems are of central importance. The objectives of this study were to determine if VEGF, VEGF receptor-2 (VEGFR-2), and components of the Ang-Tie system are expressed in ovarian follicles at both the protein and mRNA levels and to explore if their expression is related to the stage of the estrous cycle in the ewe. Ovaries from cyclic ewes were collected during the luteal phase (n=5) or before (n=5), during (n=4), and after (n=4) the preovulatory luteinizing hormone (LH) surge. After fixation, ovaries were wax-embedded, serially sectioned, and analyzed for both protein and mRNA expression of VEGF, VEGFR-2, angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), Tie-1 (mRNA only), and Tie-2. mRNA was studied by in situ hybridization using digoxigenin-11-UTP-labeled ovine riboprobes. A similar pattern of expression was observed for mRNA and protein for all of the factors. Both mRNA and protein expression of VEGF, VEGFR-2, Ang-1, Ang-2, Tie-1 (mRNA only), and Tie-2 in the granulosa and theca cells of follicles >or=2mm in diameter was significantly different among the stages of the estrous cycle, with the highest expression detected at the post-LH surge stage. Theca cells expressed significantly greater levels of the six angiogenic factors compared with granulosa cells at all stages of the estrous cycle. Expression levels in granulosa and theca cells were comparable between small (2.0 to 2.5mm) and medium (2.5 to 4.0mm) follicles, but large follicles (>4.0mm) expressed higher mRNA and protein levels (all P<0.05) for all factors at all stages of the estrous cycle. These data show (i) that VEGF, VEGFR-2, and the Ang-Tie system are present in both granulosa and theca cells of the ovarian follicle, (ii) that thecal cells consistently express greater levels of all of these factors compared with granulosa cells, and (iii) that their levels of expression are related to the stage of the estrous cycle and to follicle size.

Angiogenesis and vascular function in the ovary

Ovarian function is dependent on the establishment and continual remodelling of a complex vascular system. This enables the follicle and/or corpus luteum (CL) to receive the required supply of nutrients, oxygen and hormonal support as well as facilitating the release of steroids. Moreover, the inhibition of angiogenesis results in the attenuation of follicular growth, disruption of ovulation and drastic effects on the development and function of the CL. It appears that the production and action of vascular endothelial growth factor A (VEGFA) is necessary at all these stages of development. However, the expression of fibroblast growth factor 2 (FGF2) in the cow is more dynamic than that of VEGFA with a dramatic upregulation during the follicular–luteal transition. This upregulation is then likely to initiate intense angiogenesis in the presence of high VEGFA levels. Recently, we have developed a novel ovarian physiological angiogenesis culture system in which highly organised and intricate endothelial cell networks are formed. This system will enable us to elucidate the complex inter-play between FGF2 and VEGFA as well as other angiogenic factors in the regulation of luteal angiogenesis. Furthermore, recent evidence indicates that pericytes might play an active role in driving angiogenesis and highlights the importance of pericyte–endothelial interactions in this process. Finally, the targeted promotion of angiogenesis may lead to the development of novel strategies to alleviate luteal inadequacy and infertility.

Histological and immunohistochemical characterization of equine anovulatory haemorrhagic follicles (AHFs)

Anovulatory haemorrhagic follicles (AHFs) are often the reason for ovulation failure in the mare. As the underlying factors that lead to AHF development are not well understood, it was of interest to investigate the vascularization of AHFs compared with normal follicles and corpora lutea (controls). In the present study, the ovarian cell populations investigated immunohistochemically included granulosa and luteal cells as well as various vascular structures. None of these cell types showed differences in the expression of vascular endothelial growth factor A (VEGF-A) between control ovaries containing normal follicles and corpora lutea and ovaries with AHFs. In contrast, a considerable reduction in the proportion of Flk-1-expressing cells, together with a decreased intensity of staining, was apparent in the AHFs. This greatly reduced expression of Flk-1 in the luteinized cells and the vascular structures of AHFs may lead to a distinct decrease in the potential pro-angiogenic activity of VEGF-A in these structures compared with the situation in normal follicles and corpora lutea. Furthermore, the authors suspect that the distinct expression of angiopoietin2 and VEGF-A seen in the cells within the inner fibrous layers of the AHFs was caused by hypoxia resulting from deficient vascularization, as suggested by the irregularity of the capillaries present in the luteinized wall of the AHF. In addition, whereas LH-receptor (LH-R) expression occurred uniformly in all stages of development of the corpora lutea in normal control ovaries, there was highly variable labelling for LH-R in all the AHFs examined, thereby indicating a possible numerical deficiency of LH-receptors in AHFs. The authors concluded that, despite the apparent expression of sufficient VEGF-A in the AHFs allows ovulation and corpus luteum formation, a relative lack of receptor, Flk-1, effects the pro-angiogenic activity of VEGF-A which could be a reason for ovulation failure associated with AHF formation.

A novel physiological culture system that mimics luteal angiogenesis

Luteal inadequacy is a major cause of poor embryo development and infertility. Angiogenesis, the formation of new blood vessels, is an essential process underpinning corpus luteum (CL) development and progesterone production. Thus, understanding the factors that regulate angiogenesis during this critical time is essential for the development of novel strategies to alleviate luteal inadequacy and infertility. This study demonstrates the development of a physiologically relevant primary culture system that mimics luteal angiogenesis. This system incorporates all luteal cell types (e.g. endothelial, steroidogenic cells, fibroblasts and pericytes). Using this approach, endothelial cells, identified by the specific marker von Willebrand factor (VWF), start to form clusters on day 2, which then proliferate and develop thread-like structures. After 9 days in culture, these tubule-like structures lengthen, thicken and form highly organized intricate networks resembling a capillary bed. Development of the vasculature was promoted by coating wells with fibronectin, as determined by image analysis (P<0.001). Progesterone production increased with time and was stimulated by LH re-enforcing the physiological relevance of the model in mimicking in vivo luteal function. LH also increased the area stained positively for VWF by twofold (P<0.05). Development of this endothelial cell network was stimulated by fibroblast growth factor 2 and vascular endothelial growth factor A, which increased total area of VWF positive staining on day 9, both independently (three- to fourfold; P<0.01) and in combination (tenfold; P<0.001). In conclusion, the successful development of endothelial cell networks in vitro provides a new opportunity to elucidate the physiological control of the angiogenic process in the developing CL.

Effect of the luteinising hormone surge on regulation of vascular endothelial growth factor and extracellular matrix-degrading proteinases and their inhibitors in bovine follicles

The aim of the present study was to evaluate the pattern of regulation of vascular endothelial growth factor (VEGF)-A (isoforms 121, 165, 189), VEGF receptor tyrosine kinases (VEGF-R1 and VEGF-R2), matrix metalloproteinase (MMP)-1, MMP-2, MMP-14, MMP-19, tissue-specific inhibitor of metalloproteinases (TIMP)-1, TIMP-2, tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), urokinase plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) in time-defined follicle classes before (0 h) and after the application of gonadotrophin-releasing hormone (GnRH). Bovine ovaries containing periovulatory follicles or new corpora lutea (CL; Days 1-2) were collected 0, 4, 10, 20 and 25 h (follicles) or 60 h (CL) after the injection of GnRH. Transcripts of VEGF isoforms (VEGF(121), VEGF(165), VEGF(189)) were upregulated 4 h after GnRH injection (during the luteinising hormone (LH) surge) and decreased thereafter to lowest levels around ovulation. All VEGF isoforms and their receptors were upregulated again after ovulation. The VEGF peptide concentration in follicular fluid decreased 20 h after GnRH injection, followed by an increase in follicles 25 h after GnRH. Expression of MMP-1 mRNA increased rapidly 4 h after GnRH injection and remained high during the entire experimental period. In contrast, MMP-19 mRNA increased significantly only after ovulation. Expression of TIMP-1 mRNA increased 4 h after GnRH and again after ovulation. Expression of tPA mRNA increased 4 h after GnRH and remained high during the entire experimental period, whereas expression of uPA transcripts increased significantly only after ovulation. Both uPAR and PAI-1 mRNA levels increased in follicles 4 h after GnRH and again after ovulation. The amount of MMP-1 protein (immunolocalisation) increased in follicles 10 h after GnRH: additional staining was observed in the granulosa cell layer. In conclusion, the temporal and spatial pattern of regulation of VEGF and extracellular matrix-degrading proteinases during periovulation suggests they are important mediators of the LH-dependent rupture of bovine follicles and for early CL formation (angiogenesis).

Expression of vascular endothelial growth factor and receptor tyrosine kinases in cardiac ischemia/reperfusion injury

INTRODUCTION

Vascular endothelial growth factor (VEGF) expression is regulated by hypoxia and cytokines, including insulin-like growth factor (IGF)-1. We examined the influence of ischemia/reperfusion (I/R) on IGF-1, VEGF, fetal liver kinase (flk-1), fms-like tyrosine kinase-1 (flt-1), and laminin using an isolated hemoperfused working porcine heart model of acute ischemia (2 h) and reperfusion (4 h).

METHODS

Twenty-three porcine hearts were randomized into the following groups: five nonischemic control hearts (Group C), five I/R hearts with occlusion of the ramus circumflexus; three I/R hearts treated with quinaprilat, a potent angiotensin-converting enzyme (ACE) inhibitor (Group Q); five I/R hearts treated with angiotensin I (Group Ang I), and 5 I/R hearts treated with Ang I and quinaprilat (Group QA).

RESULTS

Compared to C, VEGF mRNA and protein contents were significantly increased in I/R and Ang I hearts. flk-1 and flt-1 were increased in I/R (2.2-/1.95-fold) and further elevated by Ang I (3.2-/3.4-fold) compared with C. Quinaprilat application attenuated the amount of VEGF significantly and of flk-1 slightly but not that of flt-1. In contrast, IGF-1 and IGF-1 receptor (IGF-1R) proteins were elevated in I/R hearts (3-/1.4-fold vs. C) and further increased in the presence of Q. These findings were accompanied by an elevation of laminin mRNA and protein levels. Moreover, we observed an increase in collagen Type IV and chondroitin sulfate content in I/R (2.9-/1.4-fold) and Ang I (3.5-/1.5-fold) hearts. Quinaprilat significantly reduced laminin and chondroitin sulfate proteins.

CONCLUSION

These data suggest that the VEGF/VEGF receptor and IGF-1-IGF-1R systems are activated by I/R. The benefits of ACE inhibition in attenuation of cardiac remodeling may be mediated by IGF-1.

Fibroblast Growth Factor 2 Is More Dynamic than Vascular Endothelial Growth Factor A During the Follicle-Luteal Transition in the Cow1

Luteal inadequacy is a major cause of infertility in a number of species. During the early luteal phase, progesterone production requires the rapid growth of the corpus luteum (CL), which is in turn dependent on angiogenesis. In the present study, we examined the temporal changes in vascular endothelial growth factor A (VEGFA), fibroblast growth factor 2 (FGF2) and secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) during the follicular-luteal transition and CL development in the cow. Luteal VEGFA concentrations increased as the CL developed but were lower in the regressing CL. Conversely, luteal FGF2 concentrations were highest immediately postovulation in the collapsed follicle and declined as the CL developed. Furthermore, three FGF2 isoforms were present in the collapsed follicle, but only one isoform was detected in older CL. Interestingly, FGF2 concentrations increased in the regressing CL. Western blot analysis for SPARC showed the presence of two isoforms, which were constitutively expressed throughout CL development. Further studies investigated the regulation of FGF2 by LH, which showed that FGF2 concentrations in preovulatory follicular fluid were higher in those animals that had experienced an LH surge. Moreover, LH stimulated FGF2 production in dispersed luteal cells. Conversely, the LH surge had no effect on follicular fluid VEGFA concentrations. In conclusion, FGF2 was more dynamic than VEGFA and SPARC during the follicular-luteal transition, which suggests that FGF2 plays a key role in the initiation of angiogenesis at this time. Furthermore, it is likely that this is stimulated by the LH surge. The results also suggest that VEGFA and SPARC have a more constitutive, but essential, role in the development of the CL vasculature.

Follicle selection in cattle and horses: role of intrafollicular factors

The eminent event in follicle selection during a follicular wave in monovular species is diameter deviation, wherein one follicle continues to grow (developing dominant) and other follicles (subordinates) begin to regress. In cattle, the IGF system, oestradiol and LH receptors are involved in the intrafollicular events initiating deviation as indicated by the following: (1) concentrations of free IGF-I and oestradiol in the follicular fluid and number of LH receptors in the follicular wall increase more dramatically in the future dominant follicle than in the future subordinate follicles before the beginning of deviation and (2) ablation of the largest follicle (LF) or injection of recombinant human IGF (rhIGF)-I into the second LF at the expected beginning of deviation increases the concentrations of oestradiol in second LF before the expected beginning of deviation between second LF and third LF. In horses, an increase in free IGF-I, oestradiol, inhibin-A and activin-A is greater in the future dominant follicle than in other follicles before the beginning of deviation. However, free IGF-I is the only one of these four factors needed for the initiation of deviation in horses as indicated by the following: (1) ablation of LF at the expected beginning of deviation increases the concentrations of free IGF-I in second LF before the beginning of deviation between second LF and third LF but does not increase the other factors; (2) injection of rhIGF-I into second LF at the expected beginning of deviation causes second LF to continue to grow and become a codominant follicle and (3) injection of IGF-binding protein-3 into LF at the expected beginning of deviation causes LF to regress and second LF to become dominant. Thus, the dramatic changes in the IGF system in LF compared to other follicles before the beginning of deviation play a crucial role in the events that lead to the beginning of diameter deviation in both cattle and horses. Oestradiol and LH receptors also play a role in cattle. These intrafollicular events prepare the selected follicle for the decreasing availability of FSH and increasing availability of LH. The other follicles of the wave have the same future capability but do not have adequate time to attain a similar preparatory stage.

The gonadotropins: tissue-specific angiogenic factors?

The gonadotropins, whose members are human chorionic gonadotropin (hCG), lutenizing hormone (LH) and follicle-stimulating hormone (FSH) are a well characterized hormone family known to regulate reproductive functions in both females and males. Recent studies indicate that they can modulate the vascular system of reproductive organs. It was shown that gonadotropins not only influence the expression of vascular endothelial growth factor (VEGF) and both its receptors VEGFR-1 and -2, but also modulate other ubiquitously expressed angiogenic factors like the angiopoietins and their receptor Tie-2, basic fibroblast growth factor or placental-derived growth factor. Some recent data indicates a possible direct action of gonadotropins on endothelial cells. Thus, the gonadotropins act as tissue-specific angiogenic factors providing an optimal vascular supply during the menstrual cycle and early pregnancy in the female reproductive tract as well as in testis. In pathological conditions (e.g. preeclampsia, intrauterine growth restriction, ovarian hyperstimulation or endometriosis), these tightly regulated interactions between the gonadotropins and the ubiquitous angiogenic factors appear to be disturbed. The intent of this short manuscript is to review the current knowledge of the regulatory role of the gonadotropins in vasculo- and angiogenesis. We also review angiogenic actions of thyroid-stimulating hormone (TSH), a glycoprotein closely related to gonadotropins, which display strong gonodal actions.