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Abstract
In each estrous cycle dominant follicles are selected from a growing pool to develop to the preovulatory stage and to ovulate. Those follicles that do not ovulate must be eliminated in order to maintain the constant mass and homeostasis of the ovary. Granulosa cells are lost by apoptosis at the onset of follicular atresia, whereas apoptotic thecal cells are identified at later stages of atresia. Since transforming growth factor (TGF) α and TGFβ1 have been implicated in the regulation of thecal cell physiology we have localized these growth factors by immunohistochemistry in sections of ovaries from 25-day-old rats, an age at which the ovary exhibits a wave of atresia of preantral follicles. Thecal cells contained TGFα and TGFβ1 throughout the entire process of follicular atresia. To determine if these growth factors could influence thecal cell death, thecal/interstitial cells were isolated from 25-day-old rats, and maintained in culture with growth factors. Subconfluent cultures treated with TGFα or TGFβ1 alone remained healthy whereas in the presence of both TGFα and TGFβ1 there was light microscopical evidence of rounding up of cells and detachment from the monolayer. Chromatin condensation and internucleosomal fragmentation, characteristic of apoptosis, were observed by nucleic acid staining and fluorescence microscopy of thecal/interstitial cells treated with TGFα plus TGFβ1. Further evidence that these cells were undergoing apoptosis came from DNA analysis and the demonstration of DNA laddering. This response of thecal/interstitial cells to TGFα plus TGFβ1 was density dependent; confluent cultures were protected from the induction of apoptosis under these conditions. We conclude that thecal cells are eliminated from atretic follicles by the active and strictly regulated process of apoptosis involving the combined actions of TGFα and TGFβ1.
Journal of Endocrinology (1997) 153, 169–178
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Abstract
Androgen receptor (AR) distribution and developmental regulation in the rat ovary were examined by semiquantitative immunohistochemistry. Ovarian AR mRNA levels were also determined by Northern analysis of total RNA and compared with the levels of cytochrome P450aromatase (P450arom), an established marker of preovulatory follicular maturity. Hypophysectomized immature female rats were treated with recombinant human (rh)-FSH and/or rh-LH, or human menopausal gonadotrophin (HMG). AR was predominately located in granulosa cells. There was no indication of specific AR immunoreactivity in thecal cells, but scattered stromal cells did stain positively. In control and LH-treated ovaries, only small preantral/early antral follicles were present. Granulosa cells in these follicles showed intense AR immunostaining. Treatment with FSH, FSH and LH or HMG stimulated varying degrees of preovulatory follicular development. In these follicles, the intensity of AR immunostaining progressively declined as follicular development progressed. In intact immature rats treated with FSH, the abundance of ovarian AR mRNA was significantly decreased to 35% of the control value while combined treatment of FSH and LH resulted in further down-regulation of AR mRNA expression to 17% of the control value. A decrease in the abundance of AR mRNA was accompanied by a simultaneous increase in the abundance of P450arom mRNA. Similar results were obtained in hypophysectomized immature rats treated with FSH and LH, suggesting an inverse relationship between AR mRNA expression and granulosa cell maturity. These results suggest that (1) the AR is most abundant in the granulosa cells of rat ovaries and (2) the expression of AR and its mRNA are developmentally regulated, being down-regulated during FSH-stimulated preovulatory follicular development.
Journal of Endocrinology (1995) 145, 535–543
Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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Department of Reproductive Medicine, Westmead Hospital, University of Sydney, New South Wales 2145, Australia
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preovulatory follicular growth (reviewed in McGee & Hsueh 2000 , Hillier 2001 ). In contrast, the primordial follicles are generally thought to be FSH-independent. Primordial follicles are present and develop up to the late preantral stage in the ovaries of
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Abstract
The acquisition of FSH receptor during preantral folliculogenesis is believed to be a key step in the subsequent development of follicles. We examined the interaction between activin and cAMP in FSH receptor induction in rat granulosa cells by measuring 125I-FSH binding and FSH receptor mRNA. In the 125I-FSH binding study, 0·2 mm 8-Br-cAMP and 1 μm forskolin were maximally effective in FSH receptor induction (169 and 220% respectively of control), while higher concentrations gave attenuated responses. It appears that cAMP has ambivalent effects on FSH receptor induction depending on the concentration and length of exposure. Activin alone dramatically increased the number of FSH receptors (314% of control). Moreover, synergistic effects of activin and 8-Br-cAMP or forskolin were observed on FSH receptor induction: a combination of activin (80 ng/ml) and low doses of 8-Br-cAMP (0·2 mm) or forskolin (1 μm) was most effective (160 or 140% of that induced by activin alone) and receptor levels reached a maximum at 24 h. These levels then markedly decreased after 72 h of incubation. Northern blot analysis revealed that the combination of activin (80 ng/ml) and 8-Br-cAMP (0·2 mm) or forskolin (1 μm) increased FSH receptor mRNA to about 140% of that induced by activin alone. These results indicate that activin and cAMP induced FSH receptor synergistically. However, activin did not enhance the production of cAMP induced by forskolin. In addition, a protein kinase A inhibitor (H89) (2 μm), which inhibited the effects of forskolin, had no effect on the action of activin. Taken together, the present findings suggest that the action of activin is not via a cAMP pathway, and that activin works co-operatively with cAMP on folliculogenesis.
Journal of Endocrinology (1995) 147, 103–110
Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Faculty of Veterinary Medicine, PPGCV, State University of Ceara, Fortaleza, CE, Brazil
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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mRNA for activin and their receptors in bovine and rodent preantral follicles (i.e. primordial, primary and secondary follicles), in vitro studies with isolated primary and secondary follicles have demonstrated that, in these species, activin-A is
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activin-A stimulates pre-antral follicle development in bovine ( Hulshof et al. 1997 ) and rodent isolated follicles ( Liu et al. 1998 , Smitz et al. 1998 , Zhao et al. 2001 ), increases FSH receptor and FSH-induced luteinising hormone (LH
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Division of Endocrinology and Metabolism, Center for Human Reproduction, Department of Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, PO Box 693, Rochester, New York 14642, USA
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. 1998 ) demonstrate that androgens (testosterone) in a positive feedback loop increases AR expression in the theca and GCs of preantral follicles, while studies in rats have shown that AR expression is developmentally regulated ( Tetsuka et al . 1995
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Department of Anatomical Sciences, School of Medicine, Iran University of Medical Science, Tehran, Iran
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). In humans, VEGFA165, VEGFA121, VEGFA189 and its receptors’ mRNA and proteins have been found in preantral follicles ( Abir et al . 2010 a ). The in vitro growth of ovarian follicles and maturation depend on several parameters. Reactive oxygen
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preantral stages (transitional and primary) in PA and control animals ( Fig. 2 ). The difference between PA animals and controls was not significant. Figure 2 Proportion of primordial and growing follicles in the foetal sheep ovary. There was no effect of
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Hurk R 1997 Bovine preantral follicles and activin: immunohistochemistry for activin and activin receptor and the effect of bovine activin A in vitro . Theriogenology 48 133 –142. Johnson AL , Bridgham JT & Wagner B
