Growth factors in ovarian function

The Concept of Growth Hormone Deficiency Affecting Clinical Prognosis in IVF

The current understanding of human growth hormone (hGH; here GH) action is that the molecule is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by the somatotroph cells within the lateral wings of the anterior pituitary gland. It can be classified as a protein (comprising more than 50 amino acids) but true proteins have tertiary and quaternary chains creating a more complex structure, hence GH is usually classified as a polypeptide. GH is normally secreted at night during sleep and promotes skeletal, visceral and general body growth through the action of somatomedins or IGFs, notably IGF-1. In some tissues, GH action is directed via specific receptors GHRs; these are most abundant in liver, adipose and muscle tissues but have also been shown in granulosa cells, testicular tissues and on the oocyte, as well as in glandular cells of the luteal phase endometrium and decidua; such findings being recent and minimally researched to now. Following engagement with its receptor, the transduction process activates multiple signaling proteins. These all lead to extensive metabolic and mitogenic (growth promoting) responses. Clinically, GH is known to have an important role in pubertal development and is a key hormone for the vigor associated with adolescence and early adult life stages but has a faded presence and role for later adulthood, beyond age 30 years, and is minimally detected in advanced age, beyond 40 years. In association with the rapidly increasing trend for delaying reproduction beyond age 35 years, GH is being widely researched now as a potential adjuvant for infertility treatment in this group who, studies consistently show, have a poorer prognosis than younger females when relying on autologous oocytes. The idea that the age-related reduction in fertility prognosis is a feature of growth hormone deficiency is supported by our studies showing an elevated binding protein IGFBP-3/IGF-1 ratio and this can be reduced to a normal range (matching younger, good prognosis women) by the administration of GH as an adjuvant.

Mouse models to study polycystic ovary syndrome: a possible link between metabolism and ovarian function?

Polycystic ovary syndrome (PCOS) is the most common cause of female infertility affecting 6-8% of women worldwide. PCOS is characterized by two of the following three criteria: clinical or biochemical hyperandrogenism, oligo- or amenorrhea, and polycystic ovaries (PCO). In addition, women with PCOS are often obese and insulin resistant, and are at risk for type 2 diabetes and cardiovascular disease. The etiology of PCOS remains unknown. Therefore, several animal models for PCOS have been generated to gain insight into the etiology and development of the PCOS-associated phenotypes. Androgens are considered the main culprit of PCOS, and therefore, androgenization of animals is the most frequently used approach to induce symptoms that resemble PCOS. Prenatal or prepubertal androgen treatment results in many characteristics of human PCOS, including anovulation, cyst-like follicles, elevated luteinizing hormone (LH) levels, increased adiposity, and insulin insensitivity. However, PCOS has a heterogeneous presentation, and therefore it is difficult to generate a model that exactly reproduces the reproductive and metabolic phenotypes observed in women with PCOS. In this review, we discuss several mouse models for PCOS, and compare the reproductive and/or metabolic phenotypes observed in several androgen-induced models as well as in several genetic models.

Follicle populations, ovulation rates and profiles of gonadotropins, inhibin and insulin-like growth factor-1 of heifers actively immunized against androstenedione and inhibin, separately or in combination

Four groups of 20 Simmental cross heifers were actively immunized against human serum albumin (control, (C), androstenedione (A), a 30 amino acid synthetic fragment of porcine inhibin alpha (I) or A and I in combination (AI). At the time of the third and final antigen injection and again 2 weeks later, all animals were injected with synthetic prostaglandin F2α (PG) to synchronize oestrus. Concentrations of LH, FSH, insulin-like growth factor-1 (IGF-1) and inhibin (C and A heifers only) in serum samples collected twice daily during 3 days before the second PG injection and at 15-min intervals from 24 to 32 h after PG injection were determined. Two weeks later, all heifers were administered PG and ovariectomized 24 h later. Ovarian follicles were dissected from the stroma, measured and cultured in medium 199 for 2h at 37°C. Numbers of small (3·0 to 7·9 mm diameter) and large (>8·0 mm diameter) follicles were not significantly altered by any of the immunization treatments. Intrafollicular concentrations and secretion rates of oestradiol, testosterone, progesterone and inhibin, determined in vitro, were not affected by immunization. Intrafollicular IGF-1 concentrations were not affected; this hormone was not detectable in the culture medium. Intrafollicular concentrations of oestrogen and testosterone and secretion rates of all three steroids were greater (P < 0·05) in animals which had regressing corpora lutea at the time of ovariectomy. Of the animals that had dominant follicles, one of 17, one of 13, four of 19 and six of 15 in the C, A, I and AI groups, respectively, had two or more. Only the difference between AI and C cows in the incidence of dominant follicles was statistically significant (P < 0·05). Mean circulating concentrations of LH, and inhibin (C and A groups only) and mean LH pulse frequency and pulse amplitude were unaffected by treatment but FSH concentrations were higher in A (P < 0·001) and lower in AI and I heifers (P < 0·001) compared with C animals while IGF-1 concentrations were lower in A heifers (P < 0·001) and higher in AI heifers (P < 0·05) compared with C heifers. It is concluded that immunization against inhibin, either alone or in combination with immunization against androstenedione increased the incidence of multiple dominant follicles in heifers but did not increase their ovulation rate.

Growth hormone supplementation improves implantation and pregnancy productivity rates for poor-prognosis patients undertaking IVF

In a sequential crossover study of IVF conducted from 2002 to 2006, growth hormone (GH) supplementation was assessed in poor-prognosis patients, categorized on the basis of past failure to conceive (mean 3.05 cycles) due to low response to high-dose stimulation (<3 metaphase II oocytes) or poor-quality embryos. Pregnancy rates in both fresh and frozen transfer cycles and the total productivity rates (fresh and frozen pregnancies per egg collection) were compared. In all, 159 patients had 488 treatment cycles: 221 with GH and 241 without GH. These cycles were also compared with 1572 uncategorized cycles from the same period. GH co-treatment significantly improved the clinical pregnancy rate per fresh transfer (P<0.001) as well as per frozen-thawed embryo derived from GH cycles (P<0.05) creating a highly significant productivity rate (P<0.001). The effect was significant across all age groups, especially in younger patients, and was independent of stimulation modality or number of transfers. GH cycles resulted in significantly more babies delivered per transfer than non-GH cycles (20% versus 7%; P<0.001) although less than the uncategorized cycles (53%). The data uniquely show that the effect of GH is directed at oocyte and subsequent embryo quality.

The role of steroids in follicular growth

The steroidogenic pathway within the ovary gives rise to progestins, androgens and oestrogens, all of which act via specific nuclear receptors to regulate reproductive function and maintain fertility. The role of progestins in follicular growth and development is limited, its action confined largely to ovulation, although direct effects on granulosa cell function have been reported. Consistent with these findings, progesterone receptor knockout mice are infertile because they cannot ovulate. Androgens have been shown to promote early follicular growth, but also to impede follicular development by stimulating atresia and apoptosis. The inability of androgens to transduce a signal in mice lacking androgen receptors culminates in reduced fertility. Oestrogens are known to exert effects on granulosa cell growth and differentiation in association with gonadotrophins. Studies with oestrogen receptor knockouts and oestrogen depleted mice have shown us that oestrogen is essential for folliculogenesis beyond the antral stage and is necessary to maintain the female phenotype of ovarian somatic cells. In summary, the action of steroids within the ovary is based on the developmental status of the follicle. In the absence of any single sex steroid, ovarian function and subsequently fertility, are compromised.

Morphodynamics of ovarian follicles during oogenesis in mice

In the mouse, oogonia enter the prophase of the first meiotic division and differentiate into oocyte while developing in the fetal ovary. Shortly after birth, all oocytes are arrested in the dictyate stage of late prophase in the developing follicles; a small number of follicles reach the ovulatory stage; the rest are lost by apoptosis. The resumption of meiotic division and nuclear progression to metaphase II (oocyte maturation) occur in the ovulatory follicles. In this article we review recent morphological data that have clarified how cytokines and glycosaminoglycans (GAGs) are involved in mouse follicular development, atresia, and maturation during oogenesis, as exogenous/endogenous factors. (1) Microvascular networks and angiogenic factors (epidermal growth factor; GAGs) are deeply involved in selective mouse oocyte growth beyond approximately 20-30 microm in diameter. (2) Gonadotropin-inducible neuronal apoptosis inhibitory protein may indirectly affect oocyte survival as a result of the inhibition of apoptotic granulosa-cell death during folliculogenesis. (3) The pattern of oocyte degeneration depends on follicle and oocyte developmental stages, and follicle stimulating hormone accelerates the process of degeneration of oocytes. (4) The process of degeneration of mouse oocytes/eggs is modulated by tumor necrosis factor-alpha that is accumulated in the expanded cumulus during oocyte maturation. (5) A colloidal iron-positive substance was detected in the intercellular spaces of follicular tissue, especially in the cumulus mass. Cells located where the cumulus mass and granulosa cell layer interwound became enlarged during the resumption of oocyte meiosis. Colloidal iron-positive substances accumulated extensively within the intercellular spaces of the enlarged cells.

Follicular Microvasculature and Angiogenic Factors in the Ovaries of Domestic Animals

The genetic and molecular mechanisms that control the development of capillary blood vessels during follicular development are beginning to be elucidated. Ovarian follicles contain and produce angiogenic factors that may act alone or in concert to regulate the process of thecal angiogenesis. These factors are ultimately controlled by endocrine, paracrine and autocrine regulation. A recent study indicated that vascular endothelial growth factor (VEGF) plays an important role in the process of thecal angiogenesis during follicular development. We are developing a novel technology for the induction of follicular development using the technique of in vivo gene administration. Here, we summarize the recent progress of our research.

Changes of messenger RNA expression of angiogenic factors and related receptors during follicular development in gilts

The interaction between angiogenic factors and related receptors is closely associated with follicular angiogenesis. The present study was performed to determine the relationships between the capillary network and mRNA expression of several angiogenic factors and related receptors during porcine follicular development. Ovaries in gilts were collected 72 h after eCG (1250 IU) treatment for histological observation. Granulosa cells and thecal tissues in small (diameter, <4 mm), medium (diameter, 4-5 mm), or large (diameter, >5 mm) individual follicles were collected for detection of mRNA expression of vascular endothelial growth factor (VEGF) 120, VEGF 164, basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) in granulosa cells and fms-like tyrosine kinase (Flt-1), fetal liver kinase (Flk-1) or the murine homologue of kinase domain region (KDR), bFGF receptor (bFGF-R), and EGF receptor (EGF-R) in thecal tissue by semiquantitative reverse transcription-polymerase chain reaction. The eCG treatment resulted in the emergence of healthy preovulatory follicles (diameter, >6.0 mm) that possessed more capillaries in the thecal cell layer and a significant increase in the percentage of atretic follicles of 1.0-2.9 mm in diameter. The number of capillaries in the thecal cell layer increased significantly in healthy follicles larger than 3 mm in diameter in the eCG group compared with those in controls. The expression of VEGF 120, VEGF 164, and bFGF mRNAs increased in granulosa cells of medium and large follicles from ovaries of prepubertal gilts after eCG treatment. The Flt-1, Flk-1/KDR, and bFGF-R mRNA expression increased in theca cells of medium and large follicles after eCG treatment. The expression of EGF mRNA increased in granulosa cells of small, medium, and large follicles from ovaries after eCG treatment, but the mRNA expression of EGF-R in thecal tissue did not change. These data indicate that preovulatory follicles possessed a larger capillary network and expressed more mRNAs of angiogenic factors in granulosa cells and related receptors in thecal tissue. We concluded that VEGF 120, VEGF 164, bFGF, and EGF may be greatly involved in the angiogenic process of follicular development in prepubertal gilts with eCG treatment.

Overview of structural and functional lesions in endocrine organs of animals

The objective of this review is to summarize the pathogenic mechanisms responsible for perturbations of endocrine function and development of structural lesions that result in important diseases in domestic and laboratory animals. For each major category, several specific disease problems have been selected to illustrate the functional and morphologic lesions that are characteristic for either a naturally occurring endocrinopathy or endocrine disturbances induced by the administration of large doses of xenobiotic chemicals. The major pathogenic mechanisms responsible for disruption of endocrine function include primary hyperfunction, secondary hyperfunction, primary hypofunction, secondary hypofunction, endocrine hyperactivity secondary to other conditions, hypersecretion of hormones by nonendocrine tumors, failure of target cells to respond to a hormone, failure of fetal endocrine function, abnormal degradation (increased or decreased rate) of hormone, and iatrogenic syndromes of hormone excess (direct and indirect). Disorders of the endocrine system are encountered in a wide variety of domestic and laboratory animal species and often present challenging diagnostic problems. The development of proliferative lesions, usually hyperplasia and benign tumors, in endocrine organs and hormone-responsive tissues are common findings in chronic studies with high doses of many nongenotoxic xenobiotic chemicals administered to sensitive rodent species and may have limited significance for human safety assessment.

Quantitative and qualitative analysis of the effectiveness of a mechanical method for the isolation of preantral follicles from ovine ovaries

The preantral follicles are the major source of oocytes and its utilization has been investigated as an important tool to store large numbers of female gametes for further utilization in reproductive programs. The aim of the present study was to perform quantitative and qualitative analyses of the efficacy of a mechanical method for isolating of preantral follicles from the ovaries of fetuses and from nonpregnant and pregnant ewes, using as reference the population of preantral follicles in situ. In the isolation method the ovaries were cut into fragments in the tissue chopper. Then, the suspension was filtered through nylon mesh filters. The number of isolated follicles per ovary was 1655, 4735 and 4770, respectively, for the fetus, nonpregnant ewe and pregnant ewe. The number of in situ preantral follicles per ovary was 32961, 16627 and 17794, respectively, for the fetus, nonpregnant ewe and pregnant ewe. The follicle recovery rate (number of isolated preantral follicles/number of in situ preantral follicles x 100) was higher in adult ewes (26 and 28%, respectively, for nonpregnant and pregnant ewes) than in fetuses (5%). Histological analysis showed that very few preantral follicles (less than 0.26% in situ and 0.46% after the isolation procedure) were degenerated. In conclusion, this study showed that a mechanical method could be used effectively to isolate a large number of intact ovine preantral follicles. In the future, with improvements in culture systems, the isolation of a great number of oocytes enclosed in preantral follicles will make a valuable contribution to the rare breeds and endangered species, agricultural efficiency and basic research in folliculogenesis.

Secretion of IGF-1 by ovine granulosa cells: effects of growth hormone and follicle stimulating hormone

Insulin-like growth factor-1 (IGF-1) is implicated in follicle development and is considered to mediate the actions of growth hormone (GH) and gonadotrophins at the ovarian level. However, the expression and secretion of IGF-1 by the ovary are controversial, partly because of species and cell-type specificity. The present study investigated whether IGF-1 is produced by ovine granulosa cells and whether its production is regulated by GH and follicle stimulating hormone (FSH). Follicles (>/=4.0 mm) were obtained from ewes during seasonal anoestrus. Granulosa cells were cultured for a total period of 96 h in Dulbecco's modified Eagle's medium (DMEM)/Ham's F-12 medium supplemented with BSA (0.1%, w:v), transferrin (0.5 microg/ml) and testosterone (100 ng/ml). In the first set of experiments, cells were incubated in the presence of bovine calf serum (BCS) (2.5%) for the initial 48 h of culture. The cells were then cultured for the next 48 h in medium without BCS, but containing either GH (0, 2, 20, and 200 ng/ml) or FSH (0, 20, 200, and 2000 ng/ml). The medium was assayed for oestradiol (E), progesterone (P) and IGF-1. There were six wells per treatment and the experiment was carried out four times. Control granulosa cells maintained both IGF-1 and E secretion, with only low levels of progesterone output. In all experiments, both GH and FSH produced significant (P<0.001) dose-related increases in E, IGF-1 and P secretion into the medium. The maximum responses to GH (20 or 200 ng/ml) were 402% for E and 528% for IGF-1 compared with controls. The maximum responses to FSH (200 or 2000 ng/ml) were 460% for E and 514% for IGF-1. The objective of the second set of experiments was to determine the effect of the progestogenic status of cells on IGF-1 production. Granulosa cells were cultured both in the presence and absence of BCS (2.5% in the medium) during the initial 48 h of culture. For the next 48 h, cells were cultured in serum-free medium. Addition of BCS to the medium during the initial 48 h of culture stimulated progesterone production. However, it did not affect either IGF-1 or oestradiol secretion between 49 and 96 h of culture, or the cell numbers at the end of culture. In conclusion, (1) IGF-1 is secreted by granulosa cells irrespective of their progestogenic status and (2) concomitant increases in E and IGF-1 production by granulosa cells as a result of GH and/or FSH treatment suggest a role for GH and FSH in the regulation of ovarian function.

The role of estrogen in folliculogenesis

Gonadotrophins are fundamental to the mechanisms regulating follicle status and development. Follicles in the ovary are either quiescent or committed to one of two pathways: growth or atresia. The requirement for gonadotrophins by the follicles varies with development: committed follicles grow independently of gonadotrophins (primarily FSH) until the late preantral stage when antrum formation is contingent upon FSH. The involvement of estrogen in regulating gonadotrophin secretion is well documented and while evidence for a local regulatory role of estrogen in the ovary mounts, an obligatory role for estrogen in the folliculogenic process has not been established. The availability of a wide range of gene-disrupted mice termed 'knockouts', is providing information relevant to the study of folliculogenesis. Mice deficient in either estrogen or estrogen receptors, are infertile primarily due to either a block in folliculogenesis prior to antrum formation or as a consequence of failing to ovulate. Blocking estrogen stimulated, post-receptor molecules such as cyclin D2, severely retards granulosa cell proliferation and leads to infertility, although the contribution of estrogen in this model is not so clear given that FSH also stimulates cyclin D2. Similar problems dissociating the roles of FSH and estrogen are evident with the FSH deficient animal models. Nevertheless, estrogen is clearly an important and probably obligatory regulator of folliculogenesis, especially in the post antral stage. The exact points in the folliculogenic process where estrogen exerts its principal effects remains to be elucidated.

The effect of epidermal growth factor on the preimplantation development, implantation and its receptor expression in mouse embryos

OBJECTIVE

To investigate the influence of epidermal growth factor (EGF) on preimplantation development, implantation, and expression of epidermal growth factor receptor (EGFR) itself in mouse embryos.

MATERIALS AND METHOD

Eight-cell stage mouse embryos were cultured for 48 hours with EGF at concentrations of 0.1, 1.0, 10 and 100 ng/ml. Embryos not treated with EGF were served as control. The percentages of embryos which developed to the expanded, hatched blastocyst stage and in vitro implantation at 48 hours were determined. Reverse transcription-polymerase chain reaction (RT-PCR) has been used to examine the expression of EGFR in developed hatched blastocysts. Following reverse transcription, strategically designed nested primers, optimized for specificity, were used for amplification from the cDNA equivalent of a single embryo. The products were then verified by restriction enzyme digestion and sequence analysis. Results were analyzed with chi 2 test and Student's t-test as appropriate, and statistical significance was defined as p < 0.05.

RESULTS

The percentages of fully expanded blastocysts at 48 hours in all the EGF treated group were not significantly different from the control. The percentages of hatched blastocysts were significantly higher in the EGF treatment group at 0.1 ng/ml (90.5 +/- 9.8%) compared to the control (82.1 +/- 7.2%), 1.0 ng/ml (82.2 +/- 12.7%), and 100 mg/ml (81.9 +/- 11.8%) (p < 0.05, p < 0.05, p < 0.05, respectively). The percentages of hatched blastocysts were significantly higher in the EGF treatment group at 10 ng/ml (89.4 +/- 7.5%) compared to the control, and 100 ng/ml (p < 0.05, p < 0.05, respectively). The percentages of attached blastocysts in vitro were significantly higher following incubation with EGF at concentrations of 0.1 ng/ml (37.0 +/- 17.0%), 1.0 ng/ml (32.0 +/- 14.3%), 10 ng/ml (21.3 +/- 7.2%) compared to the control (9.5 +/- 7.7%) (p < 0.05, p < 0.05, p < 0.05, respectively). The attachment rates in 0.1 ng/ml and 1.0 ng/ml EGF treatment groups were also significantly higher than those in other EGF treatment groups. Embryo development and attachment were not significantly inhibited or enhanced in cultures supplemented with 100 ng/ml EGF compared to the control. The mRNA concentration of EGFR in embryos treated with 0.1 ng/ml of EGF was significantly higher than those of the control and other EGF treatment groups.

CONCLUSION

EGF may have a stimulatory role in later stage embryonic development, implantation and expression of EGFR in hatched blastocyst itself at the specific concentration.

A sparsely vascularised zone in the cortex of the bovine ovary

We consider that the microvascular bed may play a role in the initiation and maintenance of growth from primordial to primary follicles. Therefore, using immunochemistry, we examined microvessels in calf and cow ovaries to identify the presence of factor VIII-related antigen endothelial cells. A vessel-poor zone was observed in the cortex of immature and mature cow ovaries. Primordial and primary follicles were assembled in this zone. It is concluded that follicular dormancy is likely to be maintained by the scarcity of microvessels and thus by the consequent poverty of the blood supply.

The ovarian renin-angiotensin system in reproductive physiology

The identification of the presence of prorenin, renin, angiotensinogen, angiotensin-converting enzyme, angiotensin II (Ang II), and Ang II receptors in the ovary suggests that there is a functional ovarian renin-angiotensin system (RAS). It could play a significant role in such areas of ovarian physiology as follicular development, steroidogenesis, oocyte maturation, ovulation, and follicle atresia. Expression of the ovarian RAS is regulated by gonadotropins. Ang II, a bioactive octapeptide of RAS, has important effects as a paracrine/autocrine regulator at different stages of the reproductive cycle. Ang II modulates ovarian steroidogenesis and formation of the corpus luteum and also stimulates oocyte maturation and ovulation via Ang II receptors on granulosa cells. In addition, increasing evidence demonstrates that Ang II is a major factor in regulating the function of atretic follicles. In any physiologic system, aberrations result in the development of pathologic states. Disturbances in the ovarian RAS can be the cause or the result of such reproductive disorders as polycystic ovary syndrome, ovarian hyperstimulation syndrome, ovarian tumors, and ectopic pregnancy. Data support the concept of an active and regulated RAS in ovarian follicles. Species differences observed in the expression of ovarian RAS suggest varying functional roles among species with respect to ovarian physiology.

Histologic and autoradiographic study of the in vitro effects of FGF-2 and FSH on isolated bovine preantral follicles: Preliminary investigation

Bovine early preantral follicles (40 to 65 microm diameter) were cultured for 24 or 48 h in the presence of 0, 10, 50 or 100 ng/ml of basic fibroblast growth factor (FGF-2), porcine FSH (pFSH) or both (ratio 1:1); the follicles were also exposed throughout the entire culture period to 2 microCi/ml ((3)H) thymidine. The effects of these factors on oocyte morphology and follicular DNA synthesis were then analyzed. Autoradiography was performed on histological serial sections of follicles after the culture period. Oocyte morphology of each follicle and the rate of follicular DNA synthesis were evaluated at the same time. Oocyte morphology was considerably altered in the presence of exogenous FSH. This effect seemed to be reduced by FGF-2, at least up to 24 h of culture. Analyzable incorporation of ((3)H) thymidine was only detected after 48 h of culture. The FGF-2 significantly increased the number of labeled nuclei per follicle whereas pFSH did not. This responsiveness of granulosa cells to FGF-2 disappeared in the presence of pFSH. No correlation was found between the number of labeled nuclei per follicle and the morphology of its oocyte. These results suggest that in cultured bovine early preantral follicles, pFSH induces oocyte degeneration and that this degeneration seems to be attenuated by FGF-2. In addition, FGF-2 lead to an increase in follicular DNA synthesis that disappeared in the presence of pFSH.

Long-term co-culture of bovine granulosa cells with microvascular endothelial cells: effect on cell growth and cell death

The intraovarian axis between granulosa cells and thecal cells is regulated by locally produced autocrine and paracrine factors. Until now, microvascular endothelial cells (MVEC) have not been included in such studies. Bovine granulosa cells from medium-sized antral follicles were plated at low density into the lower compartment of 24-well-culture plates on day 0. MVEC derived from bovine corpus luteum were seeded on appropriate inserts and placed as the upper compartment on day 1. Control granulosa cell cultures and MVEC co-cultures were maintained in serum-containing medium. On day 21, control cultures displayed an epithelioid monolayer and the coculture displayed a multilayer. Histochemical staining for 3 beta-HSD activity and for the lipid droplet stain with the fluorescent dye Nile Red were strong, suggesting augmented steroidogenesis in the multilayer. Yet the progesterone levels of supernants corrected for 10,000 cells were similar in monolayers and in multilayers. Co-cultures contained approximately three times more granulosa cells than control cultures as evaluated with a Coulter counter. Additionally, the occurrence of dead cells was quantified with the fluorescent DNA stain, ethidium homodimer, in 11-day-old control cultures and MVEC co-cultures which were deprived of serum, MVEC, or both for an additional 40 h. Serum and MVEC suppressed the occurrence of granulosa cell death. It is concluded that MVEC produce survival factors for the growth and maintenance of granulosa cells.

Bovine blastocyst development after follicle-stimulating hormone and platelet-derived growth factor treatment for oocyte maturation in vitro

Bovine embryonic viability after in vitro fertilisation (IVF) was affected by addition of platelet-derived growth factor (PDGF) or growth factor combinations to gonadotrophin-supplemented serum-free medium for in vitro maturation (IVM). Thus, 0.1, 1.0 or 10.0 ng PDGF/ml combined with 500 ng follicle-stimulating hormone (FSH)/ml enhanced oocyte maturation as reflected by greater proportions (p < 0.05) of matured and inseminated oocytes developing to blastocysts in vitro than were afforded by PDGF alone, i.e. 32.4%, 28.2% and 31.0% respectively vs. 11.4%, 13.5% and 8.6% respectively. By contrast, luteinising hormone (LH, 500 ng/ml) combined with the same concentrations of PDGF did not increase the proportions of oocytes developing to blastocysts (16.2%, 12.5% and 16.9%). Epidermal growth factor (EGF) + insulin-like growth factor-I (IGF-I) with or without PDGF when added to low concentrations of FSH or LH did not significantly improve cleavage or morula development. Significant improvement (p < 0.05) in blastocyst formation was seen when FSH was supplemented with either EGF (38.0%) or EGF+IGF-I+PDGF (40.7%) compared with FSH alone (27.4%) or FSH+LH (24.3%), but no improvement followed FSH+EGF+IGF-I (33.6%) or FSH+LH+EGF+IGF-I+PDGF (29.2%) treatments for IVM. Results revealed a positive influence on blastocyst development of FSH and PDGF or EGF +/- PDGF during IVM and suggest the possibility of a concerted action of gonadotrophins with growth factors in physiological (functional) oocyte maturation.

Intercellular communication between cultured granulosa cells of the marmoset (Callithrix jacchus)

The influence of follicle-stimulating hormone, forskolin, insulin-like growth factor type I, epidermal growth factor, and 12-tetradecanoyl-phorbol-13-acetate on marmoset granulosa cell communication via gap junctions was investigated by morphological means and microinjection of carboxyfluorescein. Gap junctions between neighbouring granulosa cells were present in all groups. The number, but not length, of gap junctions between marmoset granulosa cells increased when the cells had been treated with follicle-stimulating hormone, insulin-like growth factor type I, and follicle-stimulating hormone plus insulin-like growth factor type I. No effect on gap junctions was seen, after exposure of the cells to the other three substances. Carboxyfluorescein and counting of the surrounding labelled cells showed that supplementation with follicle-stimulating hormone, forskolin, insulin-like growth factor type I and epidermal growth factor from the beginning of cultivation led to an increase in stained cells after 48 h. When treatment was started in 48 h cultures the substances reached their maximal activity within 30 min (forskolin and epidermal growth factor) or 3 h (follicle-stimulating hormone and insulin-like growth factor type I). Spreading of the fluorescent dye was inhibited when the medium was supplemented with 12-tetradecanoyl-phorbol-13-acetate. This effect was maximal after 30 min. Additive effects regarding the coupling of the cells were seen by combining of epidermal growth factor with follicle-stimulating hormone, but not with insulin-like growth factor type I or forskolin plus follicle-stimulating hormone.

The ovary

The functions of the ovary can be described as a storehouse for oocytes as well as a factory to produce mature oocytes at the appropriate time for fertilization and hormones at the appropriate time and in the appropriate quantities to assure fertility. A complex multiple-job specification such as this requires control processes which allow all facets to operate successfully at the same time, and in a co-ordinated manner. This can only be achieved by hypothesizing control at several levels, namely, externally via gonadotrophins (and perhaps GH and prolactin), and internally via local regulators, where the local regulators control the gonadotrophin-independent processes and fine tune the gonadotrophin-dependent processes. The available evidence is consistent with a role for local regulators in the control of follicular and luteal function in the ovary. In most cases, however, the nature of the local regulator involved in a particular process is not known. On the other hand, the list of candidates continues to increase (see Table 1). A priority for future research will be to firmly establish many of these substances as local regulators and to understand how and when they exert their actions, particularly in vivo. A particularly complex question concerns the potential interaction between the local regulators which have either similar or opposing actions. The clinical significance of local regulation in the ovary is yet to be fully appreciated. The addition of GH to gonadotrophin therapy for ovulation induction (Homburg et al, 1988) is the first example of the application of findings from basic research on local regulators in the ovary. It may be that clinical syndromes such as resistant ovary syndrome, polycystic ovarian disease and luteinized unruptured follicle have some perturbation of local regulator production or action, which, if defined, would underline the importance of local regulation and could offer a means of treatment.

Fertilizability and subsequent developmental ability of bovine oocytes matured in medium containing epidermal growth factor (EGF)

We have previously shown that epidermal growth factor (EGF) is capable of promoting maturation of bovine cumulus-oocyte complexes in chemically defined serum-free medium. In this study, fertilizability and subsequent developmental capacity of bovine oocytes matured in EGF-containing medium were evaluated. Fetal bovine serum (FBS, 10%) and EGF at 10 ng/ml in Dulbecco's modified Eagles medium with Ham's nutrient mixture F-12 (DME/F12) significantly increased the rate of formation of two pronuclei compared with the rate obtained from DME-F12 alone (P<0.05). Early embryonic development was assessed during 48 h in culture. Data were evaluated in terms of cleavage and four- to eight-cell formation. Oocytes matured in 10 ng/ml EGF showed significantly higher rates of cleavage (P<0.01) and four- to eight-cell formation than did oocytes matured in control medium (P<0.05). Bovine oocytes matured in the presence of EGF can be normally fertilized and can cleave and develop in vitro up to the eight-cell stage.

Effects of insulin-like growth factor I and growth hormone in cultured human granulosa cells

Human granulosa cells, obtained either from natural or stimulated cycles, were cultured, and the response to IGF-I and GH was analyzed. It was found that IGF-I alone stimulated thymidine incorporation in both types of granulosa cells. Furthermore, IGF-I alone and in combination with FSH or LH enhanced estradiol and progesterone production. In a limited series of experiments, GH in combination with FSH was found to stimulate steroidogenesis in granulosa cells obtained from natural, but not from stimulated, cycles.

The effect of co-treatment with recombinant bovine somatotrophin on plasma progesterone concentration and number of embryos collected from superovulated Holstein heifers

Mature Holstein heifers were induced to superovulate with twice-daily injections of porcine follicle-stimulating hormone (FSH), and were given either 20 mg i.m. of recombinant bovine somatotrophin (rBST) or saline with each FSH injection. The animals were artificially inseminated and the embryos were collected nonsurgically at Day 7. There was no significant difference in the mean (+/-S.D) total number of embryos collected from rBST-treated animals (8.3+/-5.3) when compared with that of the controls (7.2+/-6.6), or in the mean number of transferable embryos (5.3+/-4.0 vs 5.2+/-4.5). However, co-treatment with rBST tended to increase the ovulatory response, and it significantly increased plasma progesterone concentrations at Day 6 (P = 0.04). Based on these latter observations, we conclude that treatment with rBST enhanced the superovulatory response in heifers.

Regulation by growth factors of Leydig cell differentiated functions

In this paper the effects of growth factors on the differentiated function of pig Leydig cells and other steroidogenic cells are reviewed. Two types of action have been observed, i.e. positive or negative acute effects on testosterone secretion, and long-term trophic effects of hCG receptor and responsiveness to hCG. Among the growth factors, insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF beta-1) are of particular interest. IGF-I is required for the maintenance and probably the expression of differentiated functions of several steroidogenic cells, including the Leydig cells. TGF beta-1 has effects opposite to IGF-I on Leydig cell functions. When considering effects of growth factors on Leydig cells, caution should be taken in extrapolating results obtained in one species to another.

Modulation of hen granulosa cell steroidogenesis and plasminogen activator activity hy transforming growth factor alpha

Studies were conducted with chicken granulosa cells to evaluate the relative efficacy of human recombinant transforming growth factor alpha (TGF alpha) versus murine epidermal growth factor (EGF) to affect cyclic adenosine monophosphate (cAMP) accumulation and progesterone production stimulated by luteinizing hormone (LH) or steroid output induced by a cAMP analogue, and to modulate plasminogen activator (PA) activity. Increasing concentrations of EGF (33-328 nM) and TGF alpha (0.04-18 nM) were found to inhibit cAMP formation stimulated by LH in a dose-dependent manner, with calculated half-maximal inhibitory doses (ID50's) of 97.1 and 0.27 nM, respectively. Similarly, a 470-fold difference in the ability of TGF alpha (ID50 = 0.13 nM) versus EGF (ID50 = 61.3 nM) to half-maximally suppress LH-induced progesterone production was observed in the same cells. Progesterone production stimulated by a cAMP analogue (8-bromo-cAMP, 1 mM) was also attenuated by EGF (ID50 = 75.9 nM) and TGF alpha (ID50 = 0.08 nM), suggesting a post-cAMP site of inhibition by these growth factors on steroidogenesis. Finally, a 260-fold to 330-fold difference in the efficacy of TGF alpha versus EGF to half-maximally stimulate cell-associated and secreted PA activity was observed. From these data, we propose that TGF alpha may serve an important role in regulating follicular growth and maturation in the domestic hen via its ability to affect granulosa cell steroidogenesis and plasminogen activator activity.