Effect of epidermal growth factor on steroidogenesis by caprine granulosa cells in culture: interaction with FSH

Ultrastructure of Sheep Primordial Follicles Cultured in the Presence of Indol Acetic Acid, EGF, and FSH

The aim of this study was to investigate the ultrastructural characteristics of primordial follicles after culturing of sheep ovarian cortical slices in the presence of indol acetic acid (IAA), Epidermal Growth Factor (EGF), and FSH. To evaluate ultrastructure of primordial follicles cultured in MEM (control) or in MEM containing IAA, EGF, and FSH, fragments of cultured tissue were processes for transmission electron microscopy. Except in the control, primordial follicles cultured in supplemented media for 6 d were ultrastructurally normal. They had oocyte with intact nucleus and the cytoplasm contained heterogeneous-sized lipid droplets and numerous round or elongated mitochondria with intact parallel cristae were observed. Rough endoplasmic reticulum (RER) was rarely found. The granulosa cells cytoplasm contained a great number of mitochondria and abundant RER. In conclusion, the presence of IAA, EGF, and FSH helped to maintain ultrastructural integrity of sheep primordial follicles cultured in vitro.

In vitro culture of sheep lamb ovarian cortical tissue in a sequential culture medium

PURPOSE

This study evaluates the effect of a sequential culture system on the follicular development of sheep lamb ovaries, aiming to establish an available in vitro culture system for ovarian culture.

METHODS

Lamb ovarian cortical fragments were cultured on a steel mesh with a nitrocellulose membrane pre-coated by type 1 collagen. Several culture media were used for the determinations, specifically, a control medium (alpha-MEM), a constant medium (control medium supplemented with 75 ng/mL human recombinant EGF, 200 mIU/mL sheep FSH, 100 ng/mL human recombinant GDF-9, and 100 ng/mL human recombinant bFGF), and a sequential medium (control medium supplemented with sequential growth factors added on different days). Ovarian tissues, both fresh and cultured, were processed for histological and apoptotic assays, while spent culture media were processed for hormone assays.

RESULTS

It was found that the growth of lamb primordial follicles can be initiated during culture in vitro. Compared to the control medium, sequential culture medium significantly increased the percentage of secondary follicles in cultures, while the follicle and oocyte diameters of primary and secondary follicles were also observed to increase in this medium. The constant medium was found to increase the number and diameter of secondary follicles only 18 days after culture. After this same period of time, some normal antral follicles were found in the sequential medium, while a few abnormal antral-like follicles were found in the control medium. Moreover, sequential medium appeared to significantly increase estradiol and inhibin production, especially 10-18 days after culture. The highest percentage of normal follicles and the lowest apoptotic cell rates were observed in the sequential medium, suggesting that a sequential addition style of culture can improve follicle and tissue viability.

CONCLUSIONS

The sequential addition of FSH, EGF, GDF-9,and bFGF can stimulate primordial follicle transmittal into the later development stages, even as far as the antral stage, improve the survival rate of follicles, and maintain follicular viability.

Expression of mRNA and protein localization of epidermal growth factor and its receptor in goat ovaries

To examine the possibility that epidermal growth factor (EGF) and its receptor (EGF-R) are expressed throughout folliculogenesis, we studied the presence and distribution of EGF and EGF-R in goat ovaries. Ovaries of goats were collected and either fixed in paraformaldehyde for immunohistochemical localization of proteins, or used for the isolation of follicles, luteal cells and ovarian surface epithelium to study mRNA expression for EGF and EGF-R, using the reverse transcriptase polymerase chain reaction. EGF protein and mRNA were found in primordial, primary and secondary follicles as well as in small and large antral follicles and in surface epithelium, but in corpora lutea only the protein could be detected. Antral follicles expressed EGF mRNA in oocyte, cumulus, mural granulosa and theca cells. For EGF-R, both protein and mRNA were present at all stages of follicular development and in all antral follicular compartments. EGF-R protein and mRNA were also found in corpora lutea and surface epithelium. It is concluded that EGF and its receptor are expressed in goat ovarian follicles at all stages of follicle development, in corpora lutea, and in ovarian surface epithelium.

Influences of FSH and EGF on primordial follicles during in vitro culture of caprine ovarian cortical tissue

Factors that control the onset of folliculogenesis are critical to female gamete production, but poorly understood. The aim of the present study was to investigate the effects of FSH and EGF on the activation and growth of goat primordial follicles in vitro. To this end, pieces of goat ovarian cortex were cultured in vitro for 1, 3 or 5 days, at 39 degrees C in an atmosphere containing 5% CO(2), in minimum essential medium supplemented with insulin, transferrin, selenium, pyruvate, glutamine, hypoxanthine, BSA, penicillin, streptomycin and fungizone and with or without FSH (100 ng/ml) and/or EGF (100 ng/ml). At the end of the culture periods, the relative proportions of primordial, intermediate, primary and secondary follicles were calculated and compared with those in non-cultured tissue. In addition, mitotic activity of granulosa cells was studied by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In brief, it was found that goat primordial follicles activate spontaneously during culture in vitro and, while neither FSH nor EGF affected the proportion of primordial follicles that entered the growth phase, both stimulated an increase in oocyte and follicle diameter, especially in intermediate and primary follicles cultured for 5 days. On the other hand, there was no significant effect of culture or either growth factor on the proportion of PCNA-stained growing follicles. Contrary to expectations, neither FSH nor EGF affected follicle viability or integrity during culture, since the percentages of intact follicles did not differ between control, FSH and/or EGF containing medium. In conclusion, this study demonstrated that goat primordial follicles activate spontaneously in vitro, and that both FSH and EGF stimulate an increase in follicle size by promoting oocyte growth.