Inhibitory effects of interleukin-1 on follicle-stimulating hormone induction of aromatase activity, progesterone secretion, and functional luteinizing hormone receptors in cultures of porcine granulosa cells

Effects of interleukin-1 (IL-1) on FSH-induced differentiation of immature porcine granulosa cells in vitro were examined in short-term (48-h) cultures. IL-1 inhibited FSH induction of aromatase activity and of LH-stimulated cAMP accumulation by granulosa cells. Both these inhibitory actions of IL-1 were concentration-dependent. Significant inhibitory effects were observed with as low as 0.05-0.25 ng/ml of IL-1, with maximal effects at 25 ng/ml. IL-1 also significantly inhibited increases in [125I]iodo-LH binding and progesterone secretion induced by FSH, as well as reducing basal levels of aromatase activity and LH-stimulated cAMP accumulation. Studies on the mechanisms of IL-1 actions on FSH-induced differentiation of immature porcine granulosa cells revealed that IL-1 reduced cAMP accumulation by the cells in response to FSH in a time- and concentration-dependent manner. IL-1 also inhibited induction of aromatase activity and LH-stimulated cAMP accumulation induced by dibutyryl cAMP, suggesting that IL-1 also affects the steps distal to cAMP generation. In contrast, IL-1 had no effect on progesterone secretion induced by dibutyryl cAMP, suggesting that post-cAMP steps of progesterone secretion were unaffected by IL-1.     

Involvement of transforming growth factor alpha in the regulation of rat ovarian X-linked inhibitor of apoptosis protein expression and follicular growth by follicle-stimulating hormone

The expression of X-linked inhibitor of apoptosis protein (XIAP), a member of a family of intracellular antiapoptotic proteins, is induced by FSH during follicular development in vivo. Whether the XIAP up-regulation by FSH (100 ng/ml) is a direct action of the gonadotropin and is important in the control of granulosa cell proliferation during follicular growth is unclear. The overall objective of the present study was to examine whether the FSH-induced XIAP expression and granulosa cell proliferation during follicular development is mediated by the secretion and action of intraovarian transforming growth factor alpha (TGFalpha). In rat follicles cultured for 2 and 4 days, FSH stimulated estradiol production, TGFalpha secretion, XIAP expression, and follicular growth. The theca cells are the primary follicular source of FSH-induced TGFalpha, as indicated by in situ hybridization. Intrafollicular injection of a neutralizing anti-TGFalpha antibody (50-200 ng/ml; immunoglobulin G as control) or addition of estradiol-antagonist ICI 182780 (0.5-100 nM) to the culture media suppressed FSH-induced XIAP expression and follicular growth. The effect of ICI 182780 could be partially reversed by high concentrations of estrogen (250 and 500 nM). Whereas TGFalpha (10-20 ng/ml) significantly increased granulosa cell XIAP content and proliferation in primary granulosa cell cultures, FSH alone was ineffective in eliciting the mitogenic response. Our results support the hypothesis that FSH stimulates granulosa cell proliferation via theca TGFalpha secretion and action in response to increased granulosa cell estradiol synthesis, and that XIAP up-regulation in response to FSH suppresses granulosa cell apoptosis and facilitates FSH-induced follicular growth.     

Gossypol inhibits aromatase activity in cultured porcine granulosa cells

The present study investigated whether gossypol inhibited aromatase activity in cultured porcine granulosa cells. Aromatase activity was assayed by measuring (3)H-H(2)O released from [1beta-(3)H]-androstenedione. First, immature porcine granulosa cells were cultured with various doses of follicle stimulating hormone (FSH, 1 to 1000 ng/ml) for 1 to 5 d to determine optimal culture conditions for aromatase activity assay. Second, porcine granulosa cells were cultured with or without FSH in the presence or absence of gossypol. Gossypol, at 4 muM, significantly inhibited FSH-induced aromatase activity while showing no effect on basal aromatase activity. Gossypol did not inhibit cell proliferation during cell culture. These results suggest that gossypol inhibits aromatase activity by interfering with FSH induction of aromatase in cultured porcine granulosa cells.     

Steroid production,cell proliferation,and apoptosis in cultured bovine antral and mural granulosa cells: Development of an in vitro model to study estradiol production

This study was undertaken to characterize the relationship between changes in steroid production, cell cycle activity (ie, cell proliferation) and apoptosis in antral and mural bovine granulosa cells cultured in vitro. This was done to select conditions promoting optimal estradiol production by bovine granulosa cells cultured in completely defined conditions. In the first experiment, antral granulosa cells were cultured over the entire 4 days of the culture period in the presence of either 0, 2, or 10 ng/ml of FSH (chronic conditions) or were maintained under minimal FSH support (0.5 ng/ml FSH) for the first 3 days of culture and then were challenged over the fourth day of culture with either 0, 2, or 10 ng/ml FSH (challenged conditions). Compared with cells exposed to constant FSH levels (chronic conditions), the FSH-induced production of estradiol was higher (P < 0.006) and that of progesterone was lower (P < 0.02) over the last 24 h of culture, when antral granulosa cells were maintained under minimal FSH support during the first 3 days of culture (challenged conditions). In the second experiment, dynamics of estradiol and progesterone productions, conversion of [¹⁴C]androstenedione into subsequent steroid metabolites, DNA content, cell cycle activity, and apoptosis (as assessed by flow cytometry) of antral and mural granulosa cells over the first 3 days of culture under minimal FSH support and in response to a challenge with FSH during the last 24 h of culture were evaluated. Estradiol production as well as the conversion of androstenedione into testosterone and estradiol were greater (P< 0.01) in antral than in mural granulosa cells cultured under challenged conditions. A higher proportion of mural than antral granulosa cells were in the proliferative state at the end of culture (P < 0.03). This may be related to the decreased ability of mural cells to produce estradiol. FSH suppressed (P < 0.05) the spontaneous onset of apoptosis in both cell types. These results suggest that functional differences between these two cell compartments need to be considered in studying bovine granulosa cells in vitro. Because of their large (400 to 600%) FSH-induced estradiol production, antral granulosa cells cultured under challenged conditions provide a model that can be used to examine substances for their ability to alter estradiol production and apoptosis in bovine granulosa cells. Mol. Reprod. Dev. 50:170–177, 1998. © 1998 Wiley-Liss, Inc.     

Luteal macrophage conditioned medium affects steroidogenesis in porcine granulosa cells

The purpose of the study was to examine the effect of luteal macrophage conditioned medium (LMCM) on progesterone and estradiol production by cultured granulosa cells. Porcine granulosa cells were cultured for 48 h with or without LMCM in the absence or presence of 100 ng/ml LH, FSH or prolactin. Progesterone and estradiol concentrations were measured by radioimmunoassay. Granulosa cells were analyzed histochemically and immunocytochemically for the activity and presence of Δ5, 3β-hydroxysteroid dehydrogenase (3β-HSD), respectively. LMCM stimulated basal and LH-, FSH- or prolactin-induced progesterone secretion. Similarly, LMCM augmented basal and stimulated activity of 3β-HSD in the examined cells. In contrast, LMCM decreased LH- and prolactin-induced estradiol secretion but increased FSH-induced estradiol secretion. These data demonstrate the clear stimulatory effect of LMCM on granulosal progesterone production. It is concluded that substances secreted by macrophages modulate gonadotropin effect on follicular progesterone secretion in a paracrine manner via 3β-HSD activity.     

Development of a long-term serum-free culture system for immature granulosa cells from diethylstilboestrol-treated prepubertal rabbits: influence of androstenedione and fibronectin on FSH-induced cytodifferentiation

Granulosa cells from diethylstilboestrol-treated prepubertal rabbits were cultured for 6 days in M199 with FSH (1-100 ng ml(-1)) in uncoated or fibronectin-coated plates with or without androstenedione to define the time course profile of oestradiol and progesterone secretion, and the possible modulator role of androstenedione and fibronectin during FSH-induced rabbit granulosa cell differentiation. Every 48 h, cultures were photographed and samples of medium were collected and assayed by ELISA for oestradiol and progesterone. FSH increased oestradiol secretion in a dose-dependent manner. Androstenedione augmented FSH-stimulated oestradiol secretion, and led to a decrease in secretion of oestradiol with time in culture. FSH stimulated progesterone secretion in a dose-dependent manner. This was increased by androstenedione with 10 ng FSH ml(-1) (0-96 h) and 1 ng FSH ml(-1) (96-144 h). FSH-stimulated (100 ng ml(-1)) progesterone secretion decreased at 48-96 h. Fibronectin prevented this decrease, without affecting oestradiol or progesterone secretion at other time points. FSH caused cell reaggregation at 48 h. In conclusion, this serum-free culture system is appropriate for the study of mechanisms of rabbit granulosa cell differentiation. FSH induced cytodifferentiation and reaggregation of granulosa cells. Androstenedione appeared to act synergistically with FSH to promote steroidogenesis. Fibronectin sustained progesterone secretion during differentiation.     

The effect of tumor necrosis factor/cachectin on follicle-stimulating hormone-induced aromatase activity in cultured rat granulosa cells

We investigated the effects of tumor necrosis factor (TNF)/cachectin on follicle-stimulating hormone (FSH)-induced aromatase activity in cultured rat granulosa cells using the stereospecific transfer of 3H from [1 beta-3H] androstenedione into 3H2O. TNF (10 pg/ml-10 ng/ml) inhibited FSH (250 ng/ml)-induced aromatase activity in a concentration-dependent manner, and 10 ng/ml of TNF completely abolished the FSH-induced aromatase activity. A time course analysis of the effects of TNF showed that TNF had no effect on induced aromatase activity, but inhibited the further induction of the enzyme by FSH. TNF (10 ng/ml) also inhibited the ability of TGF beta (1 ng/ml) to enhance aromatase activity and increase progesterone synthesis. Thus, TNF is a component of the complex array of proteins that modulate ovarian function and, as such, may play a physiological role in the regulation of the granulosa cell. In view of its association with cachexia, it may also play a pathophysiological role in the suppression of reproductive function during chronic illness.     

Follistatin inhibits activin-induced differentiation of rat follicular granulosa cells in vitro.

The effect of follistatin on activin-induced granulosa cell differentiation was investigated in freshly harvested granulosa cells from diethylstilbestrol (DES)-treated rats. Activin induced a remarkable change in granulosa cellular morphology from elongated fibroblast-like to round cells, which follistatin prevented. Follistatin itself had no influence on the cellular morphology. We studied the action of follistatin on activin-induced differentiation of granulosa cells cultured in a chemically defined medium. Addition of activin (30 ng/ml) to the culture increased the FSH binding site approximately 2-fold compared with the control (spontaneous expression) level, whereas follistatin reduced the activin-induced expression level to the control level in a concentration-dependent manner. Activin (30 ng/ml) markedly augmented FSH-induced hCG binding and progesterone production by approximately 20-fold, and these effects were suppressed by follistatin in a concentration-dependent manner. Similarly, addition of follistatin to the culture induced a concentration-dependent decrease of activin-enhanced inhibin-producing activity, but had no effect on FSH-induced inhibin production. These results suggest that follistatin/activin-binding protein binds to activin stoichiometrically to suppress the activin-induced differentiation of rat granulosa cell in vitro, but follistatin itself has no direct effect on activin-independent reactions.     

Transforming growth factor-beta(1) regulates differentiation of porcine granulosa cells in vitro

Transforming growth factor-beta (TGF-beta) is a potential regulator of ovarian function and follicular development. It is speculated that TGF-beta mediates the events in the follicle which culminate in ovulation of the oocyte. The complex processes which ultimately leads to this natural phenomenon must involve interactions between the 2 major follicular cell types, theca and granulosa cells, and the oocyte. Furthermore, a complex local regulatory system must exist to determine which follicles should undergo development and, eventually, which of those should ovulate or undergo atresia. To begin to understand this perplexing process, we must first understand the variables which control the function of each individual cell type. This study investigated the effect of TGF-beta(1) on FSH-induced porcine granulosa cell differentiation in vitro. Transforming growth factor-beta(1) was shown to inhibit progesterone production at high concentrations (0.1 and 10.0 ng/ml) after 12-, 24- and 48-hour treatment. However, TGF-beta(1) produced a biphasic effect on FSH-induced progesterone production during the 12-hour interval between the 36- and 48- hour treatment periods; TGF-beta(1) stimulated progesterone production at a low concentration (0.001 ng/ml) and inhibited production at high concentrations (0.1 and 10.0 ng/ml). The results obtained from the biphasic effect were not observed during any of the other incubation periods or intervals investigated. These results show that TGF-beta(1) has opposing effects on the differentiation of porcine granulosa cells as compared with those on rat granulosa cells. Moreover, TGF-beta(1) can produce opposing effects within the porcine granulosa cell itself which are specific to the concentration and treatment period used. The results of this study seem to suggest that TGF-beta(1) is species- and time-specific in its regulatory actions on FSH-induced porcine granulosa cell differentiation.     

Ghrelin and obestatin can promote human ovarian granulosa cell functions and FSH effects

The aim of the present in-vitro experiments was to examine the direct influence of ghrelin and obestatin on viability, proliferation and progesterone release by human ovarian granulosa cells and their response to FSH administration. Human granulosa cells were cultured in presence of ghrelin or obestatin (both at 0, 1, 10 or 100 ng/ml) alone or in the presence of FSH (10 ng/ml). Cell viability, accumulation of proliferation markers PCNA and cyclin B1 and release of progesterone were analyzed by Trypan blue extrusion test, quantitative immunocytochemistry and ELISA. Ghrelin, obestatin and FSH up-regulated all the measured ovarian cell parameters. Moreover, both ghrelin and obestatin promoted all the stimulatory effects of FSH. The obtained results demonstrate the direct stimulatory action of ghrelin, obestatin and FSH on basic ovarian cell functions, as well as the ability of metabolic hormones to improve FSH action on human ovarian cells.     

Kisspeptin as autocrine/paracrine regulator of human ovarian cell functions: Possible interrelationships with FSH and its receptor

The present study aims to examine the role of kisspeptin (KP), FSH, and its receptor (FSHR), and their interrelationships in the control of basic human ovarian granulosa cells functions. We investigated: (1) the ability of granulosa cells to produce KP and FSHR, (2) the role of KP in the control of ovarian functions, and (3) the ability of KP to affect FSHR and to modify the FSH action on ovarian functions. The effects of KP alone (0, 10 and 100 ng/mL); or of KP (10 and 100 ng/mL) in combination with FSH (10 ng/mL) on cultured human granulosa cells were assessed. Viability, markers of proliferation (PCNA and cyclin B1) and apoptosis (bax and caspase 3), as well as accumulation of KP, FSHR, and steroid hormones, IGF-I, oxytocin (OT), and prostaglandin E2 (PGE2) release were analyzed by the Trypan blue exclusion test, quantitative immunocytochemistry, and ELISA. KP given at a low dose (10 ng/mL) stimulated viability, proliferation, inhibited apoptosis, promoted the release of progesterone (P4), estradiol (E2), IGF-I, OT, and PGE2, the accumulation of FSHR, but not testosterone (T) release. KP given at a high dose (100 ng/mL) had the opposite, inhibitory effect. FSH stimulated cell viability, proliferation and inhibited apoptosis, promoted P4, T, E2, IGF-I, and OT, but not PGE2 release. Furthermore, KP at a low dose promoted the stimulatory effect of FSH on viability, proliferation, P4, E2, and OT release, promoted its inhibitory action on apoptosis, but did not modify its action on T, IGF-I, and PGE2 output. KP at a high dose prevented and inverted FSH action. These results suggest an intra-ovarian production and a functional interrelationship between KP and FSH/FSHR in direct regulation of basic ovarian cell functions (viability, proliferation, apoptosis, and hormones release). The capability of KP to stimulate FSHR, the ability of FSH to promote ovarian functions, as well as the similarity of KP (10 ng/mL) and FSH action on granulosa cells’ viability, proliferation, apoptosis, steroid hormones, IGF-I, OT, and PGE2 release, suggest that FSH influence these cells could be mediated by KP. Moreover, the capability of KP (100 ng/mL) to decrease FSHR accumulation, basal and FSH-induced ovarian parameters, suggest that KP can suppress some ovarian granulosa cell functions via down-regulation of FSHR. These observations propose the existence of the FSH-KP axis up-regulating human ovarian cell functions.     

Effects of Fusarium mycotoxins on steroid production by porcine granulosa cells

Fusarium mycotoxins, such as trichothecenes and zearalenone, are common grain and foodstuffs contaminants. Some of these like deoxynivalenol (DON) can negatively impact pregnancy success in swine, but evidence for direct ovarian effects of DON, zearalenone, and its major metabolite, alpha-zearalenol (ZEA) is meager. To evaluate the effects of two mycotoxins, DON and ZEA on porcine granulosa cell(s) (GC) proliferation, steroidogenesis and gene expression, pig GC from small follicles (1-5mm) were cultured for 2 days in 5% fetal bovine serum and 5% porcine serum-containing medium followed by 2 days in serum-free medium containing control (no mycotoxins) or mycotoxins (at various doses/combinations). Both DON and ZEA had biphasic effects on IGF-I-induced estradiol production, increasing estradiol production at smaller doses and inhibiting at larger doses. ZEA at 3,000 ng/mL (9.37 microM) increased IGF-I-induced progesterone production and at 30 ng/mL (0.0937 microM) and 300 ng/mL (0.937 microM) were without effect, but these doses of ZEA increased FSH-induced progesterone production. ZEA at 3,000 ng/mL inhibited FSH plus IGF-I-induced CYP19A1 and CYP11A1 mRNA abundance. DON inhibited progesterone production at 100 ng/mL (0.337 microM) and 1,000 ng/mL (3.37 microM) but at 10 ng/mL (0.0337 microM) was without effect. DON at 1,000 ng/mL (but not at 10 ng/mL) completely inhibited FSH plus IGF-I-induced CYP19A1 and CYP11A1 mRNA abundance. The concomitant treatment of ZEA had little effect on the dose response to DON. DON increased IGF-I-induced cell numbers at 10 and 100 ng/mL and inhibited cell numbers at 1,000 ng/mL, whereas ZEA had no effect on GC numbers. Only a combined treatment of DON and ZEA increased serum-induced cell proliferation. In conclusion, mycotoxins have direct dose-dependent effects on GC proliferation, steroidogenesis and gene expression. These direct ovarian effects could be one mechanism whereby contaminating Fusarium mycotoxins in feedstuffs could impact reproductive performance in swine.     

Different action of ovine GH on porcine theca and granulosa cells proliferation and insulin-like growth factors I- and II-stimulated estradiol production

Growth hormone (GH) and insulin-like growth factors (IGFs) are recognized as regulators of ovarian function. This study was designed to compare the effect of GH and IGFs added alone or together on porcine theca interna and granulosa cells proliferation and steroidogenesis. Moreover, the effect of GH on IGF-I secretion was examined. Cells were isolated from medium size follicles and cultured in vitro for 48 h in serum free medium. Estradiol and IGF-I medium concentrations were determined by radioimmunoassays. Proliferation was evaluated by alamar blue assay and by radiolabelled thymidine incorporation. GH increased IGF secretion by granulosa cells while decreased its secretion by theca cells. Proliferation of both cell types was stimulated by IGF-I and IGF-II (30 ng/ml) and modestly inhibited by GH (100 ng/ml). Insulin-like growth factor II increased, in a statistically significant manner, estradiol secretion by both cell types, while IGF-I stimulated estradiol secretion to a greater extent by granulosa then by theca cells. The synergistic action of GH and IGFs on estradiol secretion was stimulatory in theca cells and inhibitory in granulosa cells. These data demonstrate that despite its direct action on estradiol secretion by granulosa and theca cells, GH also modulated estradiol secretion induced by IGFs. Differences in the estradiol production in response to GH alone and the effect of the synergistic action of GH and IGFs suggest that different cellular mechanisms for these hormones are triggered in each cell type.     

Follicle-stimulating hormone regulation of cytochrome P-450 side-chain cleavage messenger ribonucleic acid accumulation by porcine granulosa cells isolated from small and medium follicles

The experiments described here were conducted to examine regulation of cytochrome P-450 side-chain cleavage (SCC) mRNA accumulation in porcine granulosa cells isolated from small (1-4-mm) and medium (5-6-mm) follicles. Granulosa cells were cultured under the following conditions: 1) for 48 h or 96 h with 0, 50, or 200 ng/ml porcine FSH; 2) for 96 h with 200 ng/ml FSH and aminoglutethimide (100 microM); and 3) for 96 h with forskolin (100 microM). Total RNA was extracted and examined by Northern and dot-blot hybridization analysis, and culture media were assayed for progesterone concentration. Northern blot analysis revealed a single band approximately 2.1 kb in size. Accumulation of SCC mRNA by granulosa cells was both FSH dose- and culture time-dependent (p less than 0.05) with maximal increases approximately 4.5 times control levels. Aminoglutethimide reduced progesterone production by about 80% while having no effect on granulosa cell accumulation of SCC mRNA compared to cells stimulated with 200 ng/ml of FSH. Forskolin-treated cells produced significantly more progesterone than did cells treated with FSH, but accumulation of SCC mRNA was similar. In response to FSH, concentration of SCC mRNA did not vary with follicle size, but granulosa cells from small follicles produced significantly more progesterone than did those from medium follicles. These results demonstrate that concentration of SCC mRNA in cultured porcine granulosa cells is FSH dose-dependent, does not vary significantly in cells from small- and medium-sized follicles, and is correlated with progesterone production, but may not parallel progesterone secretion. This last observation indicates that control at sites other than SCC mRNA can affect progesterone production.     

Effects of insulin-like growth factor-II on proliferation and differentiation of ovarian granulosa cells.

The effects of insulin-like growth factor-II (IGF-II) on the proliferation and differentiation of ovarian granulosa cells were studied in cultured human and porcine granulosa cells. IGF-II significantly increased basal progesterone secretion in granulosa cells at concentrations of 1-100 ng/ml. A stimulatory effect was also observed in gonadotropin-stimulated porcine granulosa cells treated with IGF-II. The secretion of estradiol by basal and gonadotropin-stimulated porcine granulosa cells was also significantly increased by adding IGF-II. IGF-II led to dose-dependent increases in [3H]thymidine incorporation into DNA and in the number of granulosa cells. To further characterize the cellular mechanisms underlying the stimulatory effects of IGF-II on the proliferation and differentiation of granulosa cells, we investigated the intermediary roles of cyclic AMP and intracellular Ca2+ concentration ([Ca2+]i). Treatment with 100 ng/ml IGF-II produced a significant increase in the basal accumulation of cyclic AMP in porcine granulosa cells. However, no change of [Ca2+]i by IGF-II was noted. IGF-II produced effects in accumulation that were similar to those of IGF-I. Our findings suggest that IGF-II may be a general stimulator in the proliferation and differentiation of granulosa cells, and that cyclic AMP may be a second messenger for the effects of IGF-II in ovarian granulosa cells.     

FSH and growth factors affect the growth and endocrine function in vitro of granulosa cells of bovine preantral follicles

The hypothesis was tested that bovine preantral follicles can be stimulated to grow in vitro by FSH and by the mitogens, epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), but not by transforming growth factor-beta (TGFbeta), which generally inhibits EGF and bFGF action. Preantral follicles, 60 to 179 mum in diameter, were isolated from fetal ovaries by treatment with collagenase and DNase and cultured for 6 d in serum-free medium, with or without FSH and growth factors. Basic FGF (50 ng/ml), and to a lesser extent FSH (100 ng/ml) and EGF (50 ng/ml), stimulated thymidine incorporation by granulosa cells in bovine preantral follicles compared to control cultures (8-, 4- and 2.5-fold the labeling index of the controls; P < 0.05). Alone TGFbeta (10 ng/ml) had no effect on (3)H-thymidine incorporation, but it completely inhibited the bFGF- but not the FSH-stimulated increase in the labeling index and mean follicular diameter of preantral follicles (P < 0.05). By the end of the culture period oocytes in most treatments had degenerated, and the few surviving oocytes were in preantral follicles cultured with FSH or bFGF. Progesterone accumulation was greater (P < 0.05) in the presence of FSH (100 ng/ml) or EGF (50 ng/ml) than with bFGF, TGFbeta or control medium. Basic FGF strongly inhibited the effect of FSH on progesterone secretion (P < 0.05). Only FSH stimulated the conversion of exogenous testosterone to estradiol and both bFGF and TGFbeta markedly inhibited FSH-stimulated estradiol accumulation. These results indicate that proliferation of granulosa cells of bovine preantral follicles can be stimulated by bFGF, FSH and EGF, whereas TGFbeta inhibits growth, and that they are steroidogenically active in culture. Basic FGF and TGFbeta antagonize FSH-stimulated steroid production by granulosa cells of cultured bovine preantral follicles.     

The role of IGF-I, cAMP/protein kinase A and MAP-kinase in the control of steroid secretion, cyclic nucleotide production, granulosa cell proliferation and preimplantation embryo development in rabbits

The aim of this study was to investigate the actions of insulin-like growth factor I (IGF-I) on the secretory and proliferative functions of rabbit ovarian cells and on early embryogenesis. It was found that addition of IGF-I at a lower concentration (1 ng/ml) stimulated progesterone secretion by cultured rabbit granulosa cells, whilst higher concentrations of IGF-I (10, 100 ng/ml) were inhibitory. IGF-I had no effect on estradiol secretion. Cyclic AMP secretion was slightly increased after addition of IGF-I at 10 ng/ml, but not by higher concentrations. Cyclic GMP secretion was stimulated by IGF-I at 100 ng/ml only. A blocker of protein kinase A, Rp-cAMPS, did not alter progesterone and estradiol secretion but did prevent the action of IGF-I on progesterone secretion. An immunocytochemical study demonstrated that IGF-I significantly increased the proportion of proliferating cell nuclear antigen-positive (PCNA-positive) cells. Rp-cAMP did not change cell proliferation but partially prevented the proliferation-stimulating effect of IGF-I. IGF-I (100 ng/ml) significantly increased the proportion of divided zygotes and the number of embryos reaching the morula/blastocyst stage. Blockers of PKA, Rp-cAMPS and KT5720, reversed the effects of IGF-I on zygote cleavage and embryo development. Addition of IGF-I (100 ng/ml) significantly increased MAPK within the cells (proportion showing immunoreactivity to ERK-1 and ERK-3 antibodies and intensity of a 42 kDa band related to ERK-2). Rp-cAMPS suppressed the basal ERK-2 immunoreactivity but not that of ERK-1 or ERK-3. It completely inhibited the IGF-I-induced activation of ERK-3 but not that of ERK-1 or ERK-2. This in vitro study demonstrates that IGF-I is a potent stimulator of ovarian secretion, proliferation and embryogenesis in rabbit. Its effects are mediated by cAMP/PKA- and, probably by, MAPK-dependent intracellular mechanisms.     

Microfilaments and FSH stimulation of rat granulosa cell steroidogenesis in vitro

The secretion of progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-dihydroprogesterone) by granulosa cells from 30-day-old rats pretreated with PMSG (4 i.u.; i.p.) was significantly increased in a time- and concentration-dependent manner by FSH or cytochalasin B. Whereas FSH markedly stimulated progestagen secretion during 3 h of incubation, a significant enhancement of the steroidogenic response was not noted until 12 h of exposure to the inhibitor in vitro. Although cytochalasin B also enhanced the submaximal stimulation of progestagen production by FSH (15 ng/ml), it was ineffective in the presence of maximal stimulatory concentration of the gonadotrophin (150 ng/nl). With increasing concentrations of cytochalasin B, the ability of FSH to further stimulate progestagen secretion was progressively reduced. Granulosa cells cultured in medium alone contained a prominent cytoplasmic array of microfilaments which was markedly reduced by FSH or cytochalasin B. FSH and, to a greater extent, cytochalasin B elicited concentration-dependent reductions in the mean area occupied by the cells on the culture surface, the contour index (a size-independent representation of cell profile irregularity) and cell perimeter, indicating that the cells underwent less spreading and were more spherical and regular in outline in the presence of either agent. The FSH-induced reductions in the three shape-related parameters were augmented by cytochalasin B although the influence of the FSH on the mean area and perimeter was progressively reduced in the presence of higher concentrations of cytochalasin B.(ABSTRACT TRUNCATED AT 250 WORDS)     

Secretion of follicle-regulatory protein by porcine granulosa cells

Follicle-regulatory protein (FRP) affects ovarian steroidogenesis and thus follicular maturation. However, secretion of FRP by cells from different-sized follicles as well as the modulation of FRP production by gonadotropins and locally produced steroids are unknown. To evaluate which cell type secretes FRP, theca and granulosa cells were obtained from porcine follicles. In addition, the effects of follicle-stimulating hormone (FSH) and steroids on FRP secretion from granulosa cells of small (less than 3 mm), medium (3-6 mm), and large (greater than 8 mm) porcine follicles and theca cells of large follicles were determined. Granulosa cells were obtained from follicular aspirates, whereas theca cells were recovered after digestion of the stereomicroscopically removed thecal layer. Both were cultured in monolayer in serum-free medium. Granulosa cells were treated as follows: 1) control; 2) FSH (250 ng/ml); 3) progesterone (500 ng/ml, 3 micrograms/ml), or estradiol-17 beta (500 ng/ml, 4 micrograms/ml), or dihydrotestosterone (500 ng/ml, 1 microgram/ml); 4) FSH + progesterone, or estradiol-17 beta, or dihydrotestosterone. Theca cells received the same treatment except that human chorionic gonadotropin (hCG) (5m IU/ml) was used in place of FSH. At 48 or 96 h, media were removed and FRP was quantitated by an Enzyme-Linked Immunosorbent Assay (ELISA). FRP was identified in granulosal medium from follicles of all sizes, but was not present in thecal cultures. At 48 h, granulosa cells from small and medium-sized follicles produced more FRP (20.04 +/- 4.4, 35.42 +/- 4.1 immunoreactive units [IRU]) than cells from large (3.53 +/- 0.97 IRU) follicles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tumor necrosis factor-alpha inhibits follicle-stimulating hormone-induced differentiation in cultured rat granulosa cells

We have investigated the effects of TNF-alpha on FSH-induced LH receptor expression, cAMP and progesterone production in cultured rat granulosa cells. TNF-alpha (0.5-100 ng/ml) inhibits the stimulating action of FSH on LH receptor formation in a dose-dependent manner with an IC50 of 1 ng/ml and an almost complete suppression of LH receptor induction for 50-100 ng/ml TNF-alpha. The inhibitory effect of TNF-alpha is not due to variations in cell number or viability but rather to a reduction of the LH receptor content per cell with no change in binding affinity (KD = 0.8 x 10(-10)M). TNF-alpha also inhibits the FSH-induced cAMP production but at a lower extent, with a maximum reduction of 60% for 100 ng/ml TNF-alpha. Moreover, TNF-alpha impairs the LH receptor formation induced by forskolin, cholera toxin or 8-Bromo-cAMP, indicating that the cytokine also acts at a step distal to FSH receptor and to cAMP formation. Finally, TNF-alpha decreases dramatically the progesterone synthesis that is stimulated by FSH, with a reduction to undetectable levels on and after 10 ng/ml TNF-alpha. These results suggest that TNF-alpha may drastically reduce the capacity of granulosa cells to differentiate upon FSH stimulation and to respond to LH during the physiological ovarian follicular maturation. Such anti-gonadotropic action of TNF-alpha on granulosa cell differentiation may be also relevant to the alteration of ovarian function during physiopathological processes like inflammatory or infection diseases.