Some fibroblast growth factors (FGFs) affect ovarian follicle cell growth and/or differentiation. Whereas many FGFs activate several FGF receptors, FGF7 and FGF10 primarily activate only one, FGFR2B. As FGF7 is produced by bovine theca cells and acts on granulosa cells, we tested the hypothesis that FGF10 may also play a role in folliculogenesis in cattle. Reverse transcription-polymerase chain reaction demonstrated the presence of FGF10 mRNA in the oocytes and theca cells of the antral follicles, as well as in the preantral follicles. FGF10 protein was detected by immunohistochemistry in the oocytes of the preantral and antral follicles, and in the granulosa and theca cells of the antral follicles. FGF10 expression in theca cells changed during follicle development; mRNA abundance decreased with increasing follicular estradiol concentration in healthy follicles, and was lowest in highly atretic follicles. Culturing of granulosa cells in serum-free medium revealed FSH regulation of FGF10 receptor expression. The addition of FGF10 to cultured granulosa cells decreased the level of estradiol but did not alter cell proliferation. These data support a role for FGF10 in signaling to granulosa cells from theca cells and/or the oocyte.

Paracrine cell signaling is believed to be important for ovarian follicle development, and a role for some members of the fibroblast growth factor (FGF) family has been suggested. In the present study, we tested the hypothesis that FGF-8 and its cognate receptors (FGFR3c and FGFR4) are expressed in bovine antral follicles. RT-PCR was used to analyze bovine Fgf8, Fgfr3c and Fgfr4 mRNA levels in oocytes, and granulosa and theca cells. Fgf8 expression was detected in oocytes and in granulosa and theca cells; this expression pattern differs from that reported in rodents. Granulosa and theca cells, but not oocytes, expressed Fgfr3c, and expression in granulosa cells increased significantly with follicle estradiol content, a major indicator of follicle health. Fgfr4 expression was restricted to theca cells in the follicle, and decreased significantly with increasing follicle size. To investigate the potential regulation of Fgfr3c expression in the bovine granulosa, cells were cultured in serum-free medium with FSH or IGF-I; gene expression was upregulated by FSH but not by IGF-I. The FSH-responsive and developmentally regulated patterns of Fgfr3c mRNA expression suggest that this receptor is a potential mediator of paracrine signaling to granulosa cells during antral follicle growth in cattle. IntroductionAntral ovarian follicle growth in monovular species is regulated by a number of factors, the most well known of which are the gonadotropins. Follicles are considered to be follicle-stimulating hormone (FSH)-dependent until dominance occurs, after which they become luteinizing hormone-dependent (reviewed by Fortune et al. 2001, Ginther et al. 2001. It has also become clear that growth factors are key stimulatory/regulatory molecules. Several lines of evidence point to a critical role for members of the transforming growth factor-b (TGF-b) superfamily, especially growth/differentiation factor 9 and bone morphogenetic protein 15 (reviewed by Gilchrist et al. 2004, Juengel et al. 2004, Shimasaki et al. 2004.The fibroblast growth factor (FGF) family is emerging as a group of factors that are potentially important for follicle growth. For example, FGF-7 is expressed in theca cells, its receptor is expressed in granulosa cells (Parrott & Skinner 1998, Berisha et al. 2004, and FGF-7 stimulated bovine granulosa cell proliferation and inhibited steroidogenesis (Parrott & Skinner 1998). Another potentially interesting member of this family is FGF-8. Widely expressed in fetal tissues, this factor is predominantly expressed in the gonads of adult rodents and ruminants (MacArthur et al. 1995a, Buratini et al. 2005. Within the ovary, Fgf8 gene expression occurs only in the oocyte in adult mice (Valve et al. 1997), which suggests a potential role in signaling of follicular cells by the oocyte.There are five known FGF receptor (FGFR) genes (Kim et al. 2001, Sleeman et al. 2001, of which FGF-8 preferentially activates FGFR4 and the 'c' splice form of FGFR3 (Ornitz et al. 1996). mRNAs encoding Fgfr4 or Fgfr3c were not consiste...

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Angiotensin II (AngII) is best known for its role in blood pressure regulation, but it also has documented actions in the reproductive system. There are two AngII receptors, type 1 (AGTR1) and type 2 (AGTR2). AGTR2 mediates the noncardiovascular effects of AngII and is expressed in the granulosa cell layer in rodents and is associated with follicle atresia. In contrast, expression of AGTR2 is reported to occur only in theca cells in cattle. The objective of the present study was to determine whether AngII also plays a role in follicle atresia in cattle. RT-PCR demonstrated AGTR2 mRNA in both granulosa and theca cells of bovine follicles. The presence of AGTR2 protein was confirmed by immunofluorescence. Abundance of AGTR2 mRNA in granulosa cells was higher in healthy compared with atretic follicles, whereas in theca cells, it did not change. Granulosa cells were cultured in serum-free medium, and treatment with hormones that increase estradiol secretion (FSH, IGF-I, and bone morphogenetic protein-7) increased AGTR2 mRNA and protein levels, whereas fibroblast growth factors inhibited estradiol secretion and AGTR2 protein levels. The addition of AngII or an AGTR2-specific agonist to granulosa cells in culture did not affect estradiol secretion or cell proliferation but inhibited abundance of mRNA encoding serine protease inhibitor E2, a protein involved in tissue remodeling. Because estradiol secretion is a major marker of nonatretic granulosa cells, these data suggest that AngII is not associated with follicle atresia in cattle but may have other specific roles during follicle growth.

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