A developmental study on the capacity of rabbit granulosa cells to respond to trophic hormones and secrete progesterone in vitro

Becoming female: Ovarian differentiation from an evolutionary perspective

Differentiation of the bipotential gonadal primordium into ovaries and testes is a common process among vertebrate species. While vertebrate ovaries eventually share the same functions of producing oocytes and estrogens, ovarian differentiation relies on different morphogenetic, cellular, and molecular cues depending on species. The aim of this review is to highlight the conserved and divergent features of ovarian differentiation through an evolutionary perspective. From teleosts to mammals, each clade or species has a different story to tell. For this purpose, this review focuses on three specific aspects of ovarian differentiation: ovarian morphogenesis, the evolution of the role of estrogens on ovarian differentiation and the molecular pathways involved in granulosa cell determination and maintenance.

Changes in 3 beta-hydroxysteroid dehydrogenase activity in the developing rabbit ovary

The presence of 3 beta-hydroxysteroid dehydrogenase in the maturing rabbit ovary was demonstrated biochemically and histochemically. Enzyme activity was negligible to absent in ovaries from rabbits less than 44 days old. The greatest activity was located in the microsomal fraction of ovaries from mature rabbits. The enzyme characteristics were: Vmax = 33.1 +/- 9.6 nmol/min/mg protein and Km = 2.16 +/- 0.28 microM. Ovaries from pregnant hyperglycemic rabbits had enzyme which showed a Vmax of 51.4 +/- 8.2 nmol/min/mg protein and Km = 2.41 +/- 0.31 microM. These results indicate that rabbit ovarian tissue becomes steroidogenically active at a time when gonadotropin levels are elevated.

Epidermal growth factor antagonizes ovarian theca-interstitial cytodifferentiation

This study was aimed at testing the hypothesis that epidermal growth factor (EGF) can modulate the gonadotropin-dependent differentiation of theca-interstitial cells in vitro. Addition of EGF to chemically defined culture medium severely antagonized the ability of hCG to transform undifferentiated theca-interstitial cells into active androgen-producing cells. The inhibitory action of EGF was dose-dependent, hormone-specific, and independent of granulosa cells. Since ovarian androgens are obligatory precursors to estrogen formation and induce atresia, a repressive action of EGF on theca-interstitial cytodifferentiation has new implications for understanding the way in which follicles develop in the ovary.

Estimation of inhibin-like activity in spent medium from rat ovarian granulosa cells during long-term culture

Granulosa cells were isolated from antral follicles of intact, adult female rats by treatment with EGTA and hypertonic sucrose, and were kept in culture for 1, 15 or 37 days. The amount of inhibin-like activity in spent rat granulosa-cell media (rGCCM) was assessed by using a bioassay for inhibin (measurement of the unstimulated release of FSH and LH by pituitary cells in culture). After 1 day in culture, inhibin-like activity was detected in rGCCM of 0.016-0.8 X 10(5) cultured granulosa cells per dish. In the bioassay, maximal suppression of FHS occurred when 0.8 X 10(5) granulosa cells were plated. With this or a larger number of cells in long-term cultures, pooled rGCCM, collected up to 37 days after plating, suppressed levels of FSH (and not of LH) in the inhibin bioassay in parallel with the suppression found after addition of charcoal-treated bovine follicular fluid (bFF), which served as a standard. The amount of inhibin-like activity of rGCCM (relative to the amount present in bFF, which was given a potency of 1) ranged between 0.05 and 0.90 X 10(-3). Release of inhibin-like activity could not be estimated on day 4, and was low from days 29 to 37 in culture. Except after 1 day of culture, no substantial amounts of progesterone were detected in the media. It is concluded that granulosa cells collected from adult, intact female rats have and retain the capacity to secrete inhibin-like activity in vitro, under basal conditions in long-term cultures.

The role of cyclic AMP in the induction of estrogen and progestin synthesis in cultured granulosa cells

The role of cyclic AMP in the induction of enzymes involved in estrogen and progestin biosynthesis in undifferentiated granulosa cells was investigated. When granulosa cells from immature hypophysectomized, DES-treated rats were cultured for 2 days in serum-free medium with aromatase substrate (10(-7) M androstenedione) together with graded doses of FSH, prostaglandin E2 (PGE2), cholera toxin (CT), or dibutyryl cyclic AMP (Bu2cAmP), there was a dose-related increase in estrogen (E) production. The induction of E production by saturating doses of FSH, PGE2, CT, and Bu2cAmP required a lag phase of approximately 24 h, after which the E response increased sharply to maximum levels at day 3, and then declined gradually to day 5. Treatment for 24 h ((day 0-1) with FSH, together with 1 microgram/ml of either actinomycin D or cycloheximide, completely abolished the stimulatory action of FSH on E production. When the inhibitors were removed, the FSH-induced increases in E returned to near normal levels after a 24-h lag period. Similar effects of the inhibitors upon E production by CT, PGE2 and Bu2cAMP were observed. As with E, the production of progesterone and 20 alpha-dihydroprogesterone was markedly stimulated by FSH, PGE2, CT and Bu2cAmP, and the results of the time course, dose response, and inhibitor experiments were similar to those for E production. These results indicate that FSH induces the de novo synthesis of enzymes required for both estrogen and progestin biosynthesis by undifferentiated granulosa cells and suggest that this action is mediated by cyclic AMP.

LH stimulation of estrogen secretion by cultured rat granulosa cells

The direct effect of LH on estrogen secretion by rat granulosa cells was investigated. Ovarian granulosa cells from immature hypophysectomized diethylstilbestrol-treated rats were primed with FSH for 2 days in vitro to induce LH receptors. After the FSH priming, the granulosa cells were washed, and recultured for 4 additional days in media containing aromatase substrate (10(-7) M androstenedione) and purified FSH or LH. After the incubations, estrogen (E), progesterone (P) and 20 alpha-dihydroprogesterone (20 alpha-OH-P) in the media were measured by RIA. When granulosa cells from hypophysectomized DES-treated rats were cultured for 6 days with FSH and androstenedione, the production of E, P and 20 alpha-OH-P was stimulated to a maximum of 100-, 200- and 270-fold, respectively, above that of control levels. In contrast, LH did not increase steroidogenesis in these cells. Following 2 days of FSH priming in vitro, however, the cultured granulosa cells exhibited marked increases (400-600%) in E, P and 20 alpha-OH-P production in response to LH treatment over a 4-day incubation period. This stimulatory effect of LH on estrogen and progestin production was dose-related; the minimum and maximum effective doses of LH for steroid production were 3 and 30 ng/ml, respectively, and the ED50 was calculated to be 6 ng/ml of LH. As with LH, FSH also stimulated steroidogenesis in a dose-related manner and the apparent ED50 of FSH on steroidogenesis was 45 ng/ml. To investigate whether LH can also stimulate aromatase activity in granulosa cells primed with FSH in vivo, immature hypophysectomized DES-treated rats were injected for 2 days with FSH after which the granulosa cells were isolated and cultured for 4 days in medium containing 10(-7) M androstenedione and LH or FSH. Both LH and FSH stimulated E, P and 20 alpha-OH-P production, and the maximum steroidogenic responses of LH and FSH were similar to those observed in cultured granulosa cells primed with FSH in vitro. THese results have demonstrated that LH is effective in stimulating both estrogen and progestin secretion in rat granulosa cells pretreated with FSH. This suggests an important role of LH in the direct control of both aromatization and luteinization in the granulosa cell.

Morphogenetic reaggregation and luteinization of mouse preantral follicle cells

Small (60-90 micrometer) and large (100-130 micrometer) preantral follicles were isolated from adult mouse ovaries by a collagenase-dissection technique. These follicles were composed of resting oocytes surrounded either by granulosa cells, only, or by granulosa and undifferentiated theca cells. Further enzymatic dissociation of primary follicles yielded monodisperse cells characterized by abundant rough endoplasmic reticulum, microfilament-rich pseudopodia and only scant lipid droplets. These cells reaggregated, when explanted in stationary culture, forming epithelial cords and structures macroscopically reminiscent of native ovarian follicles. Anticipated association of follicular cells in epithelial-like monolayers was rare (less than or equal to 10% of all cultured cells). Formation and growth of both follicle-like (FLS) and cord-like (CLS) structures occurred within 24 hours of culture, continued for 14 days, and was inhibited by cytochalasin B, but not by neuraminidase. FLS and CLS, as well as cell monolayers, underwent luteinization, as indicated by the presence in the culture medium of radioimmunoassayable progesterone and by frequent cytological features suggestive of active steroidogenesis. The present report indicates that (a) specific cell affinities exist among immature follicular cells which may play a role in folliculogenesis; and (b) follicular cells are endowed, from their early developmental stages with intrinsic steroidogenic capabilities which become phenotypically expressed after escape from the intraovarian environment.

Endocrine studies of normal and polycystic ovarian tissues in vitro

The purpose of this study was to compare the steroidogenic potential of the granulosa, theca, and medullary tissues from polycystic and normal ovaries. These ovarian endocrine compartments were isolated from appropriate ovaries and were cultured in vitro for three days in the absence (control) and presence of follicle-stimulating hormone (FSH)/luteinizing hormone (LH) (1 lU/ml), N6,O2-dibutyryladenosine-3':5''-cyclic monophosphoric acid (Bu2cAMP) (10(-2)M), and adrenocorticotropic hormone (ACTH) (1.3 U/ml). After the incubation, steroids in the media were measured by radioimmunoassay. Granulosa cells (10(5) cells per dish) from 4 to 7 mm follicles of normal and polycystic ovaries secreted progesterone spontaneously during the culture period and the production of progesterone was markedly stimulated (between tenfold and thirtyfold) by gonadotropins and Bu2cAMP but not by ACTH. Little, if any, androgen (androstenedione, dehydroepiandrosterone, and testosterone) or estrogen (estrone and estradiol) accumulated in the media of any granulosa cell culture. The control cultures of theca tissue from normal and polycystic ovaries secreted large amounts of androstenedione and progesterone and the production of these steroids by normal and polycystic ovary theca was stimulated in most cases by LH/FSH and Bu2cAMP but not by ACTH. Both normal and polycystic ovary theca secreted some testosterone and dehydroepiandrosterone but little, if any, estrone or estradiol accumulated in any theca culture. The medullary tissue of normal and polycystic ovaries produced only trace amounts of steroids in vitro except for the results from one polycystic ovary with hyperthecosis in which case significant quantities of C19 and C18 steroids were secreted. These experiments have demonstrated that isolated granulosa and theca cells from midantral follicles of normal and polycystic ovaries have a similar capacity to secrete C21 and C19 steroids in the absence and presence of trophic agents. Therefore, it seems probable that chronic anovulation in patients with polycystic ovaries is not caused by an obvious deficiency in the de novo steroidogenic potential of the multiple midantral follicles of the polycystic ovaries or by the absence of gonadotropin receptors on the polycystic ovary follicular cells.

Development-dependent responses of ovarian follicles to FSH and hCG

Ovarian follicles removed from immature rats (preantral follicles) and immature rats treated in vivo with follicle stimulating hormone (FSH) (antral follicles) released progesterone in vitro in response to either human chorionic gonadotropin (hCG), hFSH, or DBcAMP in a time- and concentration-dependent fashion. Antral follicles produced approximately 20 times more progesterone than preantral follicles in response to both FSH and hCG at 10(-7) M and approximately 5 times more progesterone in response to 8 X 10(-3) M DBcAMP. After in vitro incubations, follicles were transplanted beneath the kidney capsules of recipient rats to assess their ability to luteinize after hormonal stimulation. Only antral follicles incubated with hCG, hFSH, and DBcAMP formed ectopic corpora lutea. Adenylate cyclase activity in preantral and antral follicle granulosa cells increased in response to both 10 mM KF and 10(-6) M hFSH with no major differences observed between membranes prepared from preantral or antral follicle granulosa cells. These results demonstrate that follicular maturation is associated with major changes in the ability of the granulosa cells to produce progesterone and luteinize in response to hormonal stimulation and that these changes may be, in part, independent of a functional hormone-responsive adenylate cyclase system.

Microtubule and microfilament rearrangements during capping of concanavalin A receptors on cultured ovarian granulosa cells

Thin-section electron microscope analysis of rat and rabbit-cultured granulosa cells treated with concanavalin A (Con A) at 37 degrees C revealed coordinated changes in the cytoplasmic disposition of microfilaments, thick filaments, and microtubules during cap formation and internalization of lectin-receptor complexes. Con A-receptor clustering is accompanied by an accumulation of subplasmalemmal microfilaments which assemble into a loosely woven ring as patches of receptor move centrally on the cell surface. Periodic densities appear in the microfilament ring which becomes reduced in diameter as patches coalesce to form a single central cap. Microtubules and thick filaments emerge associated with the capped membrane. Capping is followed by endocytosis of the con A-receptor complexes. During this process, the microfilament ring is displaced basally into the cytoplasm and endocytic vesicles are transported to the paranuclear Golgi complex along microtubules and thick filaments. Eventually, these vesicles aggregate near the cell center where they are embedded in a dense meshwork of thick filaments. Freeze-fracture analysis of Con A-capped granulosa cells revealed no alteration in the arrangement of peripheral intramembrane particles but large, smooth domains were conspicuous in the capped region of the plasma membrane. The data are discussed with reference to the participation of microtubules and microfilaments in the capping process.

Mechanism of action of luteinizing hormone and follicle-stimulating hormone on the ovary in vitro

The mechanism of action of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) upon various cell types of the mammalian ovary is reviewed. Emphasis is placed upon in vitro studies using organ and cell culture as well as short-term incubations. FSH and LH actions upon the following ovarian functions are discussed: steroidogenesis and metabolism of the ovary as a whole and of the isolated follicle and its component cell types, the granulosa and thecal cells, as well as folliculogenesis and follicular growth, oocyte maturation, follicular rupture, and corpus luteum maintenance and steroidogenesis. The roles of gonadotropin receptors, AMP, prostaglandins, protein kinase, and protein synthesis in these LH and FSH actions are discussed. Intra-ovarian regulation of LH and FSH action is reviewed, including a discussion of the possible roles of follicular fluid inhibitors upon oocyte maturation and granulosa cell luteinization.

A synergistic effect of androgen on the stimulation of progesterone secretion by FSH in cultured rat granulosa cells

Granulosa cells from preovulatory follicles (PO) or from the enlarged preantral follicles of hypophysectomized immature diethylstilbestrol-treated (Hx-DES) rats were cultured with various combinations of FSH, androst-4-ene-3,17-dione (Ad), estradiol-17beta and dibutyryl cyclic AMP (dbcAMP). Progestin levels (progesterone and 20alpha-dihydroprogesterone) in the medium after 2 days of culture were assayed by radioimmunoassay. The control levels of the two progestins were lower for Hx-DES than for PO cells. Rat FSH (NIAMD-1-3;0.1 mug/ml) caused a 2-fold rise in progestin accumulation in both PO and Hx-DES cultures, dbcAMP (1 mM) increased progestin accumulation in PO cultures 4-5-fold, and to an even greater extent (10-20 fold) in Hx-DES cultures. Androstenedione (1.0 mug/ml) augmented progestin accumulation (1.5-3-fold), and synergized the steroidogenic action of FSH: in cells from Hx-DES rats, combined treatment with FSH and Ad caused a 5-10-fold increase over the values obtained with FSH alone. Testosterone and 5alpha-dihydrotestosterone, but not estradiol-17beta or estrone, mimicked these effects of Ad, Ad did not synergize the action of dbcAMP on progestin levels in Hx-DES cultures. It is proposed that androgen may play a role in the development of the FSH-responsive mechanism in preantral granulosa cells.

Spontaneous maturation of oocytes isolated from ovaries of immature hypophysectomized rats

Oocytes were collected from preantral follicles (200-300 mu in diameter) from 30-day-old immature rats 7 days after hypophysectomy. The ova were cultured in vitro for 17 hrs in a chemically defined medium and scored cytologically for meiotic maturation. Of 534 oocytes that were cultured 89% resumed meiosis; however, 98% of these oocytes arrested in either metaphase or anaphase I. In contrast, 82% of the oocytes isolated from preovulatory follicles (approximately 600 mu in diameter) of adult proestrus rats progressed to metaphase II. These results are discussed in terms of functional FSH and LH receptors on the granulosa cells.

Membrane-microtubule interactions: concanavalin A capping induced redistribution of cytoplasmic microtubules and colchicine binding proteins

The relationship between microtubules and concanavalin A surface receptors during concanavalin A capping in primary cultures of rabbit ovarian granulosa cells was examined by electron microscopic and fluorescence labeling techniques. Cells treated with concanavalin A and hemocyanin at 4 degree or 37 degree and then incubated at 37 degree for 1 hr formed large juxtanuclear caps that were observed with shadow cast replicas of the cell surface. Thin section analysis of capped cells revealed an abundance of microtubules immediately beneath the cap which were arranged approximately perpendicular to the plane of the membrane. The capping process was unaffected by the antimicrotubule agents colchicine or vinblastine. Further, vinblastine treatment of capped calls resulted in the formation of numerous paracrystals that were confined to the cytoplasm underlying the capped region of the membrane; uncapped cells displayed paracrystals that were randomly dispersed in the cytoplasm. Exposure of fixed cells to fluorescein thiocarbamyl colchicine, which localizes colchicine binding proteins, revealed an intensely fluorescent region that corresponded to the cap; this staining pattern was absent in uncapped cells. These findings indicate that concanavalin A mediated capping modifies the cytoplasmic disposition of microtubules and colchicine binding proteins. Further, it is suggested that the capped region of the plasma membrane is a preferred site of microtubule polymerization.

Structural modifications of lutein cell gap junctions during pregnancy in the rat and the mouse

By use of lanthanum tracer and freeze-fracture procedures it was found that granulosa-lutein cells of the pregnant mouse and rat ovaries are connected by gap junctions and septate-like zones of contact. Lutein cell gap junctions enlarge and become partially internalized by the end of the first week of gestation. Expansion of the gap junction domain appears to be due initially to intercalation of particles along borders of small gap junctions devoid of smaller non-junctional particles. The number of gap junction lined processes appearing at the cell border increases concomitantly with hypertrophy of the lutein cell during the second week of pregnancy. Strands of particulate or grooved membrane emanate from the margin of larger gap junctions undergoing interiorization. Most large gap junctions are intimately associated with elements of the smooth endoplasmic reticulum. Spherical gap junctional profiles assume a deeper location in the lutein cell and may form concentric arrays by term while true surface gap junctions appear to fragment in the post-partum corpus luteum. The modifications observed are interpreted with respect to biogenesis of the gap junction and the hormonal control of lutein cell function.