Envolvimento da subfamília do fator de crescimento fibroblástico 7 (FGF7) no controle da foliculogênese antral em bovinos / Involvement of fibroblast growth factor 7 (FGF7) subfamily in the control of antral folliculogenesis in cattle

Os mecanismos que coordenam o desenvolvimento folicular ainda não são completamente conhecidos e, portanto, constituem o alvo de numerosas investigações, seja por facilitarem a compreensão da fisiologia ou por serem promissoras ferramentas para a reprodução assistida. Recentemente, diversos peptídeos ovarianos de ação local têm sido descritos por participarem do controle de todas as fases do desenvolvimento folicular, bem como da modulação de hormônios esteróides ovarianos e gonadotrofinas; entre esses peptídeos estão os fatores de crescimento fibroblástico (FGFs). Os FGFs têm sido extensamente investigados em diversas fases do desenvolvimento folicular e parecem controlar processos como atresia folicular, esteroidogênese, bem como o desenvolvimento folicular pré-antral, sendo a subfamília do FGF7 uma das mais investigadas neste contexto. Assim, esta revisão tem como objetivo sumarizar a participação da subfamília do FGF7 no controle da foliculogênese antral de bovinos.

The mechanisms that coordinate follicular development are not well known and are, therefore, target of numerous investigations for facilitateing the understanding of physiology or as promising tools for assisted reproduction. Recently, several ovarian peptides with local action have been reported to participate in the control of follicular development in all stages and modulation of gonadotropins andovarian steroid hormones. In this context, fibroblast growth factors (FGFs) have been extensively investigated in different stages of follicular development and seem to control processes such as follicular atresia, steroidogenesis, and pre-antral follicle development, where FGF7 subfamily is one of the most investigated. Therefore, the objective of this review is to summarize the participation of the FGF7 subfamily in the control of bovine antral folliculogenesis.

Envolvimento da subfamília do fator de crescimento fibroblástico 7 (FGF7) no controle da foliculogênese antral em bovinos / Involvement of fibroblast growth factor 7 (FGF7) subfamily in the control of antral folliculogenesis in cattle

Os mecanismos que coordenam o desenvolvimento folicular ainda não são completamente conhecidos e, portanto, constituem o alvo de numerosas investigações, seja por facilitarem a compreensão da fisiologia ou por serem promissoras ferramentas para a reprodução assistida. Recentemente, diversos peptídeos ovarianos de ação local têm sido descritos por participarem do controle de todas as fases do desenvolvimento folicular, bem como da modulação de hormônios esteróides ovarianos e gonadotrofinas; entre esses peptídeos estão os fatores de crescimento fibroblástico (FGFs). Os FGFs têm sido extensamente investigados em diversas fases do desenvolvimento folicular e parecem controlar processos como atresia folicular, esteroidogênese, bem como o desenvolvimento folicular pré-antral, sendo a subfamília do FGF7 uma das mais investigadas neste contexto. Assim, esta revisão tem como objetivo sumarizar a participação da subfamília do FGF7 no controle da foliculogênese antral de bovinos. (AU)

The mechanisms that coordinate follicular development are not well known and are, therefore, target of numerous investigations for facilitateing the understanding of physiology or as promising tools for assisted reproduction. Recently, several ovarian peptides with local action have been reported to participate in the control of follicular development in all stages and modulation of gonadotropins andovarian steroid hormones. In this context, fibroblast growth factors (FGFs) have been extensively investigated in different stages of follicular development and seem to control processes such as follicular atresia, steroidogenesis, and pre-antral follicle development, where FGF7 subfamily is one of the most investigated. Therefore, the objective of this review is to summarize the participation of the FGF7 subfamily in the control of bovine antral folliculogenesis. (AU)

Luteinizing Hormone Receptor (LHR): basic concepts in cattle and other mammals. A review

Acquisition of the luteinizing hormone receptor (LHR) on granulosa cells of the dominant follicle is essential to physiological LH-mediated effects on the final stages of follicular growth, final maturation of the oocyte, ovulation and luteinization of the follicular wall.Therefore, LHR plays a key role in the final maturation of the dominant follicle from follicular dominance to ovulation. In this review, the basic molecular aspects of LHR (gene structure, alternative splicing and ligand mediated activation) and the physiological regulatory aspects (changes in LHR expression during antral follicle growth and a post-transcriptional model for downregulation of LHR transcripts) are addressed. Despite the accumulation of considerable amounts of information about LHR, a comprehensive and broad model for the role of LHR in bovine antral follicle growth is missing. Questions such as the function for alternative LHR transcripts, their transcriptional and translational regulation, and how the transcripts go to the cell surface and interact with ligands remain to be elucidated in bovine and other species.

Luteinizing Hormone Receptor (LHR): basic concepts in cattle and other mammals. A review

Acquisition of the luteinizing hormone receptor (LHR) on granulosa cells of the dominant follicle is essential to physiological LH-mediated effects on the final stages of follicular growth, final maturation of the oocyte, ovulation and luteinization of the follicular wall.Therefore, LHR plays a key role in the final maturation of the dominant follicle from follicular dominance to ovulation. In this review, the basic molecular aspects of LHR (gene structure, alternative splicing and ligand mediated activation) and the physiological regulatory aspects (changes in LHR expression during antral follicle growth and a post-transcriptional model for downregulation of LHR transcripts) are addressed. Despite the accumulation of considerable amounts of information about LHR, a comprehensive and broad model for the role of LHR in bovine antral follicle growth is missing. Questions such as the function for alternative LHR transcripts, their transcriptional and translational regulation, and how the transcripts go to the cell surface and interact with ligands remain to be elucidated in bovine and other species.(AU)

Expression of fibroblast growth factor 13 (Fgf13) mRNA in bovine antral follicles and corpora lutea

Recent studies have suggested a paracrine role for several fibroblast growth factors (FGFs) in the regulation of follicle and luteal development. Fgf13 is a non-secreted FGF that has been previously localized to the developing gonads, but it is not known if it is expressed in the adult ovary. The objective of the present study was to determine the expression pattern of Fgf13 mRNA in the bovine ovary. Fgf13 mRNA expression was examined by semiquantitative RT-PCR using Gapdh as the internal control gene in theca and granulosa cells, corpora lutea (CL) and oocytes collected from abattoir ovaries. Follicles were grouped according to estradiol content (20-100 and >100 ng/ml) and size (5-7, 8-10 and >10 mm diameter). CL samples were morphologically classified into four developmental stages. Fgf13 mRNA expression was assessed in pools containing 50 oocytes aspirated from follicles larger than 4 mm in diameter. ANOVA was used to test for the main effects of follicle size group, and estradiol concentration group in granulosa and theca cells, and to test the effect of CL developmental stage on Fgf13 mRNA abundance. Fgf13 mRNA was detected in the CL and in somatic follicle cells, but not in oocytes. Thecal Fgf13 expression increased with increasing follicle diameter but did not change with intrafollicular estradiol concentrations. No evidence of developmental regulation of Fgf13 mRNA expression was observed in granulosa cells and CL. The present data demonstrate for the first time the expression of an intracellular FGF in the bovine ovary and suggests that Fgf13 mRNA is upregulated in bovine theca cells during antral follicle growth.

Expression of fibroblast growth factor 13 (Fgf13) mRNA in bovine antral follicles and corpora lutea

Recent studies have suggested a paracrine role for several fibroblast growth factors (FGFs) in the regulation of follicle and luteal development. Fgf13 is a non-secreted FGF that has been previously localized to the developing gonads, but it is not known if it is expressed in the adult ovary. The objective of the present study was to determine the expression pattern of Fgf13 mRNA in the bovine ovary. Fgf13 mRNA expression was examined by semiquantitative RT-PCR using Gapdh as the internal control gene in theca and granulosa cells, corpora lutea (CL) and oocytes collected from abattoir ovaries. Follicles were grouped according to estradiol content (<5, 5-20, >20-100 and >100 ng/ml) and size (5-7, 8-10 and >10 mm diameter). CL samples were morphologically classified into four developmental stages. Fgf13 mRNA expression was assessed in pools containing 50 oocytes aspirated from follicles larger than 4 mm in diameter. ANOVA was used to test for the main effects of follicle size group, and estradiol concentration group in granulosa and theca cells, and to test the effect of CL developmental stage on Fgf13 mRNA abundance. Fgf13 mRNA was detected in the CL and in somatic follicle cells, but not in oocytes. Thecal Fgf13 expression increased with increasing follicle diameter but did not change with intrafollicular estradiol concentrations. No evidence of developmental regulation of Fgf13 mRNA expression was observed in granulosa cells and CL. The present data demonstrate for the first time the expression of an intracellular FGF in the bovine ovary and suggests that Fgf13 mRNA is upregulated in bovine theca cells during antral follicle growth.(AU)

Growth factors and steroidogenesis in the bovine placenta

The control of placental hormone biosynthesiscritical during gestation, since their coordinated action is essential for the normal progress of pregnancy. Hormonal synthesis regulation in placenta is still not elucidated and differs from that observed in other steroidogenic tissues since specific tropic hormones have not yet been identified. Cellular localization of growth factors in the placenta, including VEGF, EG-VEGF and bFGF, ponts that these factors have additional roles in the organ besides their well known modulation on cell proliferation and angiogenesis. In vitro experiments bring new evidence that growth factors play regulatory roles modulating processes related to steroid hormone secretion in the placenta. Importance of local estrogen function has beenhighlighted and a key enzyme for its synthesis is aromatase cytochrome P450. The objective of this review was to describe some aspects of placentalsteroidogenesis, mainly focusing on aromatase cytochrome P450 steroidogenic enzyme expression and growth factors as others potential modulators of hormonal synthesis in the organ.

Growth factors and steroidogenesis in the bovine placenta

The control of placental hormone biosynthesiscritical during gestation, since their coordinated action is essential for the normal progress of pregnancy. Hormonal synthesis regulation in placenta is still not elucidated and differs from that observed in other steroidogenic tissues since specific tropic hormones have not yet been identified. Cellular localization of growth factors in the placenta, including VEGF, EG-VEGF and bFGF, ponts that these factors have additional roles in the organ besides their well known modulation on cell proliferation and angiogenesis. In vitro experiments bring new evidence that growth factors play regulatory roles modulating processes related to steroid hormone secretion in the placenta. Importance of local estrogen function has beenhighlighted and a key enzyme for its synthesis is aromatase cytochrome P450. The objective of this review was to describe some aspects of placentalsteroidogenesis, mainly focusing on aromatase cytochrome P450 steroidogenic enzyme expression and growth factors as others potential modulators of hormonal synthesis in the organ.(AU)