Role of serum-free defined medium in regulation of LH receptor in cultured rat granulosa cells

Optimized culture system to maximize ovarian cell growth and functionality in vitro

Ovaries are the primary physiological source of female sex hormones, which play a crucial role in maintaining ovarian cycle, determining secondary sexual characteristics and preparing the endometrium for implantation. In vitro follicle engineering has been used to investigate follicle development, including ovarian hormone production and gamete maturation. To engineer functional follicles, culture and expansion of the primary ovarian cells are essential. However, the phenotypic and functional characteristics of primary ovarian cells are often lost during culture. The objective of this study is to develop an optimized culture system for maintaining ovarian cell growth and functionality. Granulosa cells (GCs) and theca cells (TCs) were isolated from female rats. The addition of follicle-stimulating hormone (FSH) or luteinizing hormone (LH) to the basal culture media significantly enhanced the secretion of estradiol from GCs and androstenedione from TCs. Serum concentrations of 5% and 10% had a similar role in promoting ovarian cell expansion and secretion of estradiol and androstenedione hormones from both types of cells. Growth differentiation factor 9 (GDF9), bone morphogenic protein 15 (BMP15), BMP7 and basic fibroblast growth factor (bFGF) enhanced GC proliferation and estradiol production, respectively. Among them, the effect of bFGF was most significant. bFGF also enhanced TC proliferation. When GCs and TCs were cultured in 5% serum, gonadotropin and bFGF-containing medium, they proliferated exponentially throughout the culture period of up to 40 days while maintaining their functional characteristics. Taken together, these results indicate that our medium formula is optimal for maximizing proliferation of functionally differentiated ovarian cells.

In vivo regulation of the steroidogenic activity of rat luteal cells by insulin

The aim of the present study was to determine the long-term effects of insulin treatment on luteal cell function. For this purpose, superovulated prepubertal rats were treated with insulin (group I) or vehicle (group C) for 9 days. Serum progesterone (P4) levels were increased in the insulin-treated group (55 +/- 10 vs 134 +/- 31 ng/ml, P < 0.05). Isolated luteal cells were incubated 3 h, and P4 and 20 alpha-hydroxy-progesterone (20 alpha-OH-P) were measured in the incubation media. A decrease in P4 levels and an increase in 20 alpha-OH-P values [P4 (ng/ml): C = 26.6 +/- 0.3; I = 20 +/- 2; 20 alpha-OH-P (ng/ml): C = 62 +/- 2; I: 120 +/- 7; P < 0.01] were observed in group I. In addition, progestagen (P4 + 20 alpha-OH-P) levels were higher in group I (C = 88 +/- 2; I = 140 +/- 9 ng/ml; P < 0.001). When cytochrome P450scc contents were measured by immunoblotting, a marked increase was observed in luteal cells obtained from group I. LH receptor numbers were decreased in luteal cells isolated from group I (C = 388,834 +/- 14,146; I = 303,057 +/- 13,392 sites/cell; P < 0.001) with a concomitantly diminished LH responsiveness. It is concluded that in vivo treatment of superovulated rats with insulin increases luteal progestagen production by increasing the content of cytochrome P450scc.

Characterization of follicular fluid stimulatory factor upon FSH-induced granulosa cell differentiation

The modulatory role of follicular fluid (FF) upon gonadotropin-induced granulosa cell (GC) differentiation has been previously demonstrated. In the present study, the stimulatory factor of large-antral FF (LFF) was partially characterized. Addition of ovine FSH to porcine GC culture increased 125I-hCG specific binding about 6-fold and progesterone (P4) secretion 15-fold. The FSH-induced 125I-hCG specific binding was increased 1.9-fold by LFF and decreased 7.7-fold in the presence of small-antral FF (SFF). It is suggested that SFF may contain an inhibitory factor which is overcome by a stimulatory factor accumulated in FF with follicular growth. An initial purification of LFF stimulatory factor was achieved by two-step ethanol elution. The obtained LFF purified fraction increased the FSH-induced 125I-hCG specific binding 1.5-fold and P4 secretion 4.3-fold compared to GC cultured with FSH + LFF. Addition of LH alone increased the P4 secretion 2.3-, 3.4-, and 6 fold in GC precultured with FSH alone, FSH + neat LFF, and FSH + LFF purified fraction, respectively, as compared to GC precultured in plain medium. Therefore, the LFF stimulatory increase of 125I-hCG specific binding may represent an increase of functional LH receptors. Freezing and thawing of LFF 4 times, exposing LFF to urea for 24 h, heating at 60 C for 20 min, and tryptic digestion each abolished the LFF stimulatory effect upon the FSH-dependent increase of 125I-hCG specific binding and P4 secretion. Thus, the LFF stimulatory activity could be attributed to one or more proteins.

Regulation of inhibin production by rat granulosa cells

Inhibin production by cultured granulosa cells from immature diethylstilbestrol (DES)-primed rats was studied in relation to estradiol and progesterone production. The inhibin content in culture media was assayed with a specific radioimmunoassay (RIA) using an antibody to porcine 32 kDa inhibin that recognizes rat inhibin as well. Inhibin production was about 10 ng/ml/2 X 10(4) cells/72 h at the basal levels and was maximally stimulated with 25 ng/ml of follicle stimulating hormone (FSH) to 45 ng/ml which was 4.5 times the basal levels, with an ED50 value of 2.0 ng/ml. A cyclic AMP analog (dibutyryl cyclic AMP) or reagents that promote cAMP production were also effective in inhibin production, indicating that FSH stimulates inhibin production through a cAMP-dependent pathway. Luteinizing hormone (LH) was not effective in producing inhibin from freshly prepared granulosa cells, whereas granulosa cells pre-incubated with FSH for 48 h because responsive to LH regarding inhibin production. Testosterone sensitized the granulosa cells to the FSH stimulation, whereas hydrocortisone (4 ng/ml) decreased the sensitivity of granulosa cells by increasing the ED50 value for inhibin production by FSH about 10 times. A similar effect was observed regarding estradiol production, while progesterone production due to stimulation by FSH was enhanced by the hydrocortisone treatment. Insulin and platelet extract both stimulated inhibin production and enhanced the maximal response of inhibin production due to stimulation by FSH without altering, or even increasing the ED50 values. Epidermal growth factor (EGF), (D-Leu6)Des-Gly10-LHRH N-ethylamide (GnRH agonist) and 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent protein kinase C activator, inhibited both inhibin production and estradiol or progesterone production. Consequently, the regulation of inhibin production was similar to that of estradiol production, but markedly different from that of progesterone. However, inhibin and estradiol production were modulated differently by various growth factors and hormones. These phenomena might account for possible discrete changes in the plasma levels of inhibin and estradiol in vivo.

Secretion of anti-Müllerian hormone by immature bovine Sertoli cells in primary culture, studied by a competition-type radioimmunoassay: lack of modulation by either FSH or testosterone

Secretion of anti-Müllerian hormone (AMH) by immature bovine Sertoli cells in primary culture was studied through a competition-type RIA employing a polyclonal antibody and 125I-labelled purified AMH. This RIA is approximately 10 times more sensitive than the solid-phase two-site monoclonal antibody-based RIA described previously. Biosynthesis and secretion of AMH by cultured Sertoli cells require approximately 48 h, are not influenced by FSH or testosterone and steadily decrease over a one-week period of culture. Cyclic AMP response to FSH stimulation is normal in cultured cells. Whether the factors responsible for the extinction of AMH production in vitro are in any way related to those operating during normal maturation, which lead to repression of AMH biosynthesis in adult Sertoli cells, is not known at the present time and deserves further study.

Long-term multiplication of the Chinese hamster ovary (CHO) cell line in a serum-free medium

A new synthetic medium (referred to as GC3) that supports the growth of the Chinese hamster ovary cell line has been developed. It is composed of a 1:1 mixture of Ham's F12 and modified Eagle's minimum essential (MEM.S) mediums supplemented with transferrin (10 micrograms/ml), insulin (80 mU/ml), and selenium (1 X 10(-7) M). Other more simple supplementations of our basal medium MEM.S/F12 (transferrin + insulin, transferrin + selenium, ferrous iron + selenium) also give good cell growth responses. Fibronectin or serum pretreatment is not needed for cellular attachment and spreading. Our culture system is characterized by a continuous serum-free cultivation (more than 200 doublings), a clonal growth, a high density proliferation, and a rapid growth rate near that of cells in serum-supplemented medium.

Effect of serum and 12-O-tetradecanoyl-phorbol-13-acetate on FSH-stimulated conversion of 4-androstene-3,17-dione to oestrogens in cell and organ cultures of suckling mouse ovaries

The effect of serum and 12-O-tetradecanoylphorbol-13-acetate (TPA) on the FSH-stimulated oestrogen production was studied in both cell and organ cultures. Ovaries were removed from (WB X C57BL/6)F1 mice at 9-days of age, and the conversion of 4-androstene-3,17 -dione to oestrogens was stimulated by the addition of FSH in vitro. Either 10% serum (fetal calf, mouse, rat and horse) or 0.1 microM TPA markedly inhibited the FSH-stimulated oestrogen production by dispersed and cultured ovarian cells. In contrast, neither serum nor TPA influenced the oestrogen production in the organ culture. This suggests that the presence of tissue architecture may prevent the inhibitory effect of serum and TPA on the FSH-stimulated oestrogen production.