Effects of Androgens on Early Development of Mouse Follicles in Organ-Cultured Ovaries.

Abstract

Abstract:Ovaries from 4-day-old mice were organ-cultured and the effects of progesterone, androstenedione and estradiol-17β on early follicular development were investigated. Both androstenedione (40-1,000 ng/ml) and estradiol-17β (8-1,000 ng/ml) promoted proliferation of granulosa cells in developing follicles, while progesterone showed no remarkable effect. Cyproterone acetate (4,000 ng/ml), an androgen receptor antagonist, partially inhibited the granulosa cell proliferation induced by androstenedione (40 ng/ml). Dihydrotestosterone (8-1,000 ng/ml), which is not converted to estrogens, also induced proliferation of granulosa cells. These results suggest that androgens directly promote proliferation of granulosa cells in early developing mouse follicles in vitro. Key words: Androstenedione, Granulosa cell, Mouse, Organ culture, Ovary.After birth, mouse oocytes increase in volume with an arrested nucleus at the diplotene stage of the first meiotic prophase, and ovarian follicles develop as granulosa cells proliferate within them. Oocyte growth is initially accompanied by a thickening of the flattened primitive granulosa cells to a cuboidal shape, and then by proliferation of granulosa cells. As the granulosa cells proliferate, a thecal layer appears on the surface of the follicle [1,2]. Before the follicles develop their thecal layer, negligible amounts of steroid hormones are produced in the ovaries. During thecal formation, the follicles begin steroid hormone synthesis [3,4], and then develop markedly. In later developmental stages, the follicles produce progestins, androgens and estrogens by gonadotropic stimulation [5,6], and these steroids are thought to regulate follicular development in ovaries [7][8][9].In organ-cultured mouse ovaries, oocyte growth proceeds normally, though proliferation of granulosa cells is severely retarded [10] unless stimulated by exogenous FSH [11, Ikeda et al., unpublished data], and the organ culture system of ovaries is thought to allow the effects of steroid hormones on the proliferation of granulosa cells to be examined in a highly controlled environment. In practise, the effects of estrogens on the early development of follicles have been examined in organ-cultured mouse ovaries and estrogens promoted proliferation of granulosa cells in follicles of ovaries from both 4-day-[12] and 8-day-old mice [11]. Kent [13] reported that pregnenolone, testosterone and estradiol-17β stimulated the growth of small follicles in organ-cultured ovaries from 15-day-old mice. In that experiment, however, follicular development was assessed without respect to the growth of oocytes which is one of the major factors determining follicular size in the early stages.Using the organ culture system of mouse ovaries, we examined the effect of steroid hormones on the proliferation of granulosa cells with respect to oocyte growth in early developing follicles. Ovaries from 4-day-old mice were cultured and the effects of three steroid hormones, progesterone, androstenedione and estradiol-17β, on follicul...

Oocyte growth in vitro: potential model for studies of oocyte–granulosa cell interactions

“…Besides the factors described above, estradiol [66] and androstenedione [67,68] are potent stimulators of follicular growth in vitro. IGF-I also enhances granulosa cell proliferation, maintenance of follicular integrity, and the survival of oocytes in vitro [29,32].…”

“…Besides FSH, antral formation of mouse preantral follicles is promoted by the addition of dbcAMP [69] and androstenedione [67,68] to the medium. Activin A has also been shown to promote follicular antrum formation in the rat [70] and humans [35].…”

Conditions affecting growth and developmental competence of mammalian oocytes in vitro

“…Furthermore, androgens directly promote the growth and antral formation of mouse pre-antral follicles in vitro . Similarly, in organ-cultured ovaries isolated from 4-day-old mice, androstenedione induced proliferation of granulosa cells (Ikeda et al 1999). Moreover, both studies confirmed the promotional effect of dihydrotestosterone, which does not convert to estrogens.…”

“…1998). Similarly, in organ‐cultured ovaries isolated from 4‐day‐old mice, androstenedione induced proliferation of granulosa cells (Ikeda et al . 1999).…”

Isolation of Ovarian Components Essential for Growth and Development of Mammalian Oocytes <i>In Vitro</i>

“…Although some positive effects of activin A on preantral follicle growth have been reported [28,35,74], impaired follicle viability because of activin A treatment has also been reported [75]. Estradiol [13] and androstenedione [76,77] are other potent stimulators of follicular growth in vitro that will be discussed later.…”