Abstract not available

In sheep, large ovarian antral follicles grow in waves with a periodicity of every 4 to 5 days; each wave is initiated by a peak in serum concentrations of follicle stimulating hormone (FSH). In the present thesis, follicular data and hormone estimations acquired from daily ultrasonography and blood samples, respectively, were used to study mechanisms regulating the number of follicular waves per estrous cycle. Using additional approaches such as implants releasing estradiol-17â and or progesterone, immunization against gonadotropin releasing hormone (GnRH), and injections of GnRH, the role of pulsed luteinizing hormone (LH) secretion and FSH peaks in follicular wave emergence and growth and the dependency of FSH peaks on pulsed GnRH secretion, were studied in sheep. The viability of aged follicles was also addressed.<p> The results of the present studies showed that ewes with three or four waves per cycle had cycles of the same length. The inter-wave interval was longer for the first and the last or ovulatory wave of the cycle in three compared to four wave cycles. The length of the lifespan and regression phase of the largest follicle of a wave declined across the cycle as FSH peak concentration and amplitude decreased. The maximum follicular diameter of the largest follicle growing in the first wave and the last or ovulatory wave of the cycle was greater compared to other waves of the cycle. Treatment of anestrous ewes with estradiol releasing implants alone completely abolished pulsed LH secretion and suppressed follicular wave development; however, FSH secretion was only minimally affected and the pool of small follicles was not affected. When pulsed secretion of LH was restored by frequent injections of GnRH, follicular waves were re-established. Treatment of anestrous ewes with implants releasing estradiol and progesterone, decreased FSH peak amplitude and abolished LH pulses and follicular waves; the size of the pool of small follicles increased. Immunization against GnRH in anestrous ewes abolished pulsatile LH secretion and suppressed follicular wave emergence; however, FSH peaks continued to occur for several weeks. In cyclic ewes, creating an LH pulse frequency typical of the follicular phase, during the luteal phase of the cycle by giving GnRH, increased maximum diameter of the largest follicle in a wave and serum concentrations of estradiol and progesterone. The enhanced growth of follicles in a wave blocked the next expected FSH peak and its associated follicular wave. Decreasing LH pulse frequencies lower than the minimal frequency seen in the luteal phase, by implants releasing progesterone, did not affect the growth of follicular waves.<p> It was previously demonstrated that treatment of non-prolific WWF ewes with Prostaglandin F2á (PGF2á) and medroxy progesterone acetate (MPA) increased the ovulation rate by adding ovulations from the penultimate wave in addition to the final wave of the cycle; however, fertility was not improved. In the last study of my thesis, we collected follicles, with an extended lifespan, from the penultimate wave of the cycle in ewes given the PGF2á and MPA treatment. We compared their quality with follicles from the final wave of the cycle by looking at the expression of markers of follicular development. The results showed that theca cells of follicles from the final wave had significantly higher mRNA expression for vascular endothelial growth factor (VEGF) compared to follicles from the penultimate wave. Granulosa cells of follicles from the final wave had significantly higher mRNA expression for connexion 43 (Cx43) compared to follicles from the penultimate wave. Protein expression for Cx43, proliferating cell nuclear antigen (PCNA) and Factor VIII was greater in follicles from the final compared to the penultimate wave.<p> We concluded from the present studies that: 1) the mechanism that makes a three wave or four wave cycle is unclear; 2) some level of pulsatile LH secretion is required for an FSH peak to trigger emergence of follicular waves in anestrous ewes; 3) progesterone enhances the inhibitory effects of estradiol on FSH secretion in anestrous ewes, suppressing specifically FSH peak amplitude; 4) an endogenous rhythm may exist that drives the peaks in FSH secretion independent of secretory products from the follicles growing in a wave and pulsed GnRH secretion; 5) follicular waves in ewes, when exposed to an LH pulse frequency similar to the follicular phase, during the luteal phase of the cycle, when serum progesterone concentrations are high, can grow and function like ovulatory follicles growing in the follicular phase of the cycle; 6) expression of some markers of vascularization/ angiogenesis, gap-junctional communication and cell proliferation, appeared to be decreased in follicles from the penultimate compared to the final wave of an estrous cycle, when the lifespan of follicles from the penultimate wave was extended such that they were present in the ovary with follicles from the final wave of the cycle.

Treatment success in IVF-ICSI is mainly limited by female age, but differences in ovarian reserve (OR; the remaining pool of oocytes and their quality) between individuals modify treatment prerequisites among women of similar age. OR may be assessed by OR tests (ORTs). The main aims of this work were to study menstrual cycle length (MCL), basal levels of circulating gonadotrophins, antral follicle count (AFC) and serum Anti-Müllerian hormone (AMH) levels and their associations with and prognostic capacities regarding IVF-ICSI outcome in large cohorts of unselected women. Age-adjusted MCL was positively and linearly associated with pregnancy rates (PRs), live-birth rates (LBRs) and ovarian response to controlled ovarian hyperstimulation. An MCL of &gt;34 days almost doubled the LBR compared with an MCL of &lt;26 days. The grouped variable ‘combined FSH and LH levels’ was superior to both individual gonadotrophin levels and the LH:FSH ratio. The highest mean PR was seen in connection with a combination of FSH &lt;6.7 U/l with LH &gt;4.9 U/l; PRs were lowest when FSH-LH levels were opposite to this (high-low) and intermediate when FSH-LH levels were low-low or high-high. Associations with LBR and ovarian response were similar as those for PR. AFCs and serum AMH levels were positively and log-linearly associated with PR, LBR and ovarian response. Success rates levelled out above AFC 30 or AMH 5 ng/ml. Treatment outcome was superior among women with polycystic ovaries. Among the studied ORTs, logAFC and logAMH concentration correlated most strongly. After multivariate testing, entering all studied ORTs, AMH and female age remained independently associated with LBR. AMH + AFC + age predicted both poor and excessive ovarian responses with high accuracy. Adjusting for age and oocyte yield, all ORTs remained significant for LBR, implying that ORTs also capture information on oocyte quality. In conclusion, measures of OR are strongly associated with PR, LBR and ovarian response in a log-linear fashion, and partly reflect oocyte quality. The OR spectrum is continuous, from small ‘oligofollicular’ ovaries (the low extreme) to polycystic ovaries (the high extreme). Among the studied ORTs, AMH together with age provide the most powerful basal estimate for IVF/ICSI outcome.

In sheep, large ovarian antral follicles grow in waves with a periodicity of every 4 to 5 days; each wave is initiated by a peak in serum concentrations of follicle stimulating hormone (FSH). In the present thesis, follicular data and hormone estimations acquired from daily ultrasonography and blood samples, respectively, were used to study mechanisms regulating the number of follicular waves per estrous cycle. Using additional approaches such as implants releasing estradiol-17â and or progesterone, immunization against gonadotropin releasing hormone (GnRH), and injections of GnRH, the role of pulsed luteinizing hormone (LH) secretion and FSH peaks in follicular wave emergence and growth and the dependency of FSH peaks on pulsed GnRH secretion, were studied in sheep. The viability of aged follicles was also addressed.<p> The results of the present studies showed that ewes with three or four waves per cycle had cycles of the same length. The inter-wave interval was longer for the first and the last or ovulatory wave of the cycle in three compared to four wave cycles. The length of the lifespan and regression phase of the largest follicle of a wave declined across the cycle as FSH peak concentration and amplitude decreased. The maximum follicular diameter of the largest follicle growing in the first wave and the last or ovulatory wave of the cycle was greater compared to other waves of the cycle. Treatment of anestrous ewes with estradiol releasing implants alone completely abolished pulsed LH secretion and suppressed follicular wave development; however, FSH secretion was only minimally affected and the pool of small follicles was not affected. When pulsed secretion of LH was restored by frequent injections of GnRH, follicular waves were re-established. Treatment of anestrous ewes with implants releasing estradiol and progesterone, decreased FSH peak amplitude and abolished LH pulses and follicular waves; the size of the pool of small follicles increased. Immunization against GnRH in anestrous ewes abolished pulsatile LH secretion and suppressed follicular wave emergence; however, FSH peaks continued to occur for several weeks. In cyclic ewes, creating an LH pulse frequency typical of the follicular phase, during the luteal phase of the cycle by giving GnRH, increased maximum diameter of the largest follicle in a wave and serum concentrations of estradiol and progesterone. The enhanced growth of follicles in a wave blocked the next expected FSH peak and its associated follicular wave. Decreasing LH pulse frequencies lower than the minimal frequency seen in the luteal phase, by implants releasing progesterone, did not affect the growth of follicular waves.<p> It was previously demonstrated that treatment of non-prolific WWF ewes with Prostaglandin F2á (PGF2á) and medroxy progesterone acetate (MPA) increased the ovulation rate by adding ovulations from the penultimate wave in addition to the final wave of the cycle; however, fertility was not improved. In the last study of my thesis, we collected follicles, with an extended lifespan, from the penultimate wave of the cycle in ewes given the PGF2á and MPA treatment. We compared their quality with follicles from the final wave of the cycle by looking at the expression of markers of follicular development. The results showed that theca cells of follicles from the final wave had significantly higher mRNA expression for vascular endothelial growth factor (VEGF) compared to follicles from the penultimate wave. Granulosa cells of follicles from the final wave had significantly higher mRNA expression for connexion 43 (Cx43) compared to follicles from the penultimate wave. Protein expression for Cx43, proliferating cell nuclear antigen (PCNA) and Factor VIII was greater in follicles from the final compared to the penultimate wave.<p> We concluded from the present studies that: 1) the mechanism that makes a three wave or four wave cycle is unclear; 2) some level of pulsatile LH secretion is required for an FSH peak to trigger emergence of follicular waves in anestrous ewes; 3) progesterone enhances the inhibitory effects of estradiol on FSH secretion in anestrous ewes, suppressing specifically FSH peak amplitude; 4) an endogenous rhythm may exist that drives the peaks in FSH secretion independent of secretory products from the follicles growing in a wave and pulsed GnRH secretion; 5) follicular waves in ewes, when exposed to an LH pulse frequency similar to the follicular phase, during the luteal phase of the cycle, when serum progesterone concentrations are high, can grow and function like ovulatory follicles growing in the follicular phase of the cycle; 6) expression of some markers of vascularization/ angiogenesis, gap-junctional communication and cell proliferation, appeared to be decreased in follicles from the penultimate compared to the final wave of an estrous cycle, when the lifespan of follicles from the penultimate wave was extended such that they were present in the ovary with follicles from the final wave of the cycle.

Advanced maternal age has been shown to influence follicular and luteal dynamics in bovine ovary resulting in reduced fertility. The overall objective of the four studies presented in this thesis is to identify the maternal age-associated transcriptional changes in granulosa cells of the dominant follicles during follicle development. In the first study, mRNA expression levels of housekeeping genes were measured by real–time quantitative PCR (RT-qPCR) in granulosa cells of dominant follicles and FSH-stimulated follicles to select and validate suitable reference genes for relative gene expression analyses during maternal and follicular aging. Stability of six reference genes (GAPDH, ACTB, EIF2B2, UBE2D2, SF3A1 and RNF20) was analyzed using GeNorm, DeltaCT and NormFinder programs and comprehensive ranking order was determined based on these programs. Geometric mean of multiple genes (UBE2D2, EIF2B2, GAPDH and SF3A1) was more appropriate reference control than individual genes for the comparison of relative gene expression among dominant and FSH-stimulated follicles during maternal and/or follicular aging studies. In the second study, maternal age-associated changes in the transcriptome of granulosa cells recovered at the time of selection of the dominant follicle from aged (n=3) and young cows (n=3) were determined by EmbryoGENE bovine oligo-microarrays (EMBV3, Agilent Technology). The mRNA expression of five transcripts (CYP19A1, PCNA, GJA1, TPM2, and VNN1) was confirmed in a different set of granulosa cell samples by RT-qPCR to validate microarray data. A total of 169 genes/isoforms were differentially expressed (≥ 2-fold-change; P ≤ 0.05) in aged cows vs. young cows. These transcripts revealed inefficient 1) control of gonadotropins, and gonadotropin-induced changes in the cytoskeleton and extracellular matrix, 2) lipid metabolism and steroidogenesis 3) cell proliferation, cell cycle control and intercellular communication, and 4) higher oxidative stress responses in aged cows vs. young cows. In the third study, changes in the transcriptome of granulosa cells of the preovulatory follicle 24 h after LH treatment from aged (n= 3) and young (n=3) were determined. A total of 1340 genes were expressed differentially (≥ 2-fold change; P ≤ 0.05) in aged cows vs. young cows. The mRNA expression of five transcripts (RGS2, PTGS2, TNFAIP6, VNN1, NR5A2 and GADD45B) was confirmed in a different set of granulosa cell samples to validate microarray data. These transcripts were related to delayed 1) response to LH treatment 2) cellular differentiation and luteinization and 3) progesterone synthesis. Intra-follicle levels of progesterone were lower (P < 0.05) in aged cows compared to young and mid-aged cows. The fourth study compared the aged-associated changes in the transcriptome of granulosa cells during follicle development from the time of dominant follicle selection to preovulatory stage (24 h after LH). In comparison to young cows, aged cows expressed fewer differentially expressed genes/isoforms (1206 vs. 2260, respectively) at ≥ 2-fold-change (P ≤ 0.05) in the granulosa cells of the preovulatory (24 h after LH treatment) vs. the dominant follicle at selection. These transcripts in aged cows were related to late and inefficient 1) organization of cytoskeleton and cytoplasm, 2) differentiation, 3) lipid and cholesterol metabolism, 4) proliferation and 5) higher response to oxidative stress and free radical scavenging in the preovulatory follicles vs. the dominant follicle at selection. In conclusion, maternal age-alters the gene expression of granulosa cells of the dominant follicles during follicle development and results in a compromised follicular environment.

Introdução: A síndrome antifosfolípide é uma doença autoimune caracterizada por eventos trombóticos e/ou obstétricos adversos associados à presença de anticorpos antifosfolípides. Considera-se síndrome antifosfolípide primária (SAFP) quando não há outra doença autoimune ou inflamatória associada. Objetivos: Avaliar marcadores de reserva ovariana em mulheres com SAFP e a associação entre estes marcadores e dados clínicos, laboratoriais e anticorpo anti-corpo lúteo (anti-CoL). Métodos: Realizou-se estudo transversal em 18 pacientes com SAFP e 24 controles. A reserva ovariana foi avaliada na fase folicular precoce através das dosagens de hormônio folículo estimulante (FSH), hormônio luteinizante (LH), estradiol e hormônio anti-Mülleriano (HAM), pela técnica de ELISA, e contagem ultrassonográfica de folículos antrais (CFA). O anti-CoL foi avaliado através de immunoblot. Todas as análises foram realizadas após suspensão de contraceptivo hormonal por, no mínimo, 6 meses e retorno das menstruações. O teste t foi utilizado para comparar médias ± desvio padrão e o teste de Mann-Whitney, para comparar medianas (variação). O teste exato de Fisher foi utilizado para comparar diferenças entre variáveis categóricas. Adotou-se nível de significância de 5% (p<0,05). Resultados: A média da idade foi similar em pacientes com SAFP e controles (33,0 ± 5,0 vs. 30,4 ± 7,0 anos, p=0,19). Houve maior frequência de CFA baixa (<=10) (56% vs. 22%, p=0,04) e muito baixa (<=5) (37% vs. 9%, p=0,04) em pacientes com SAFP quando comparadas aos controles. Em relação ao HAM, observou-se tendência de maior frequência de concentração sérica reduzida (<1,0 ng/mL), baixa (<0,5 ng/mL) e muito baixa (<0,2 ng/mL) em pacientes com SAFP (p=0,08; p=0,07 and p=0,07; respectivamente). As concetrações séricas de FSH, LH e estradiol foram semelhantes em pacientes e controles (p>0,05). Não houve associação entre baixa reserva ovariana e tipos específicos de anticorpos antifosfolípides. A presença do anti-CoL foi observada apenas em pacientes com SAFP (11% vs. 0%, p=0,177) e não foi relacionada a parâmetros de reserva ovariana. Conclusões: Pacientes com SAFP apresentaram reserva ovariana diminuída, com prevalência maior do que 50%, o que reforça o aconselhamento reprodutivo e planejamento familiar / Introduction: Antiphospholipid syndrome is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity associated with antiphospholipid antibodies. Primary APS (PAPS) is diagnosed when no other autoimmune or inflammatory diseases are present. Objective: to determine ovarian reserve in PAPS women and to evaluate the association between ovarian reserve tests and clinical and laboratorial parameters, and anti-corpus luteum antibody (anti-CoL). Methods: In this cross sectional study, 18 PAPS patients and 24 healthy women were evaluated at early follicular phase with measurement of follicle stimulating hormone (FSH), estradiol, and anti-Müllerian hormone (AMH), carried out by ELISA test, and sonographic antral follicle count (AFC). Serum measurement of anti-CoL was determined by immunoblot analysis. All analyses were performed after at least 6 months from the last intake of hormonal contraceptive and resumption of menstruation. Data were compared by t-test and Mann-Whitney test in continuous variables and by Fisher\'s exact test in categorical variables. The level of significance was set at 5% (p<0.05). Results: The mean age was comparable in PAPS and controls (33.0 ± 5.0 vs. 30.4 ± 7.0 years; p=0.19). Regarding ovarian reserve tests, the frequencies of low AFC (<= 10) (56% vs. 22%, p=0.04) and very low AFC (<= 5) (37% vs. 9%, p=0.04) were significantly higher in PAPS patients than controls. Trends of higher frequencies of reduced (<1.0 ng/mL), low (<0.5 ng/mL) and negligible (<0.2 ng/mL) AMH levels were found in PAPS patients (p=0.08; p=0.07 and p=0.07; respectively). FSH, LH and estradiol were similar in patients and controls. There was no association between low ovarian reserve and specific types of antiphospholipid antibodies. Anti-CoL was solely observed in PAPS patients (11% vs. 0%; p=0.177) and was not related to ovarian reserve tests. Conclusion: Women suffering from PAPS possessed reduced ovarian reserve, with prevalence greater than 50%, emphasizing fertility counseling and family planning

Introdução: A síndrome antifosfolípide é uma doença autoimune caracterizada por eventos trombóticos e/ou obstétricos adversos associados à presença de anticorpos antifosfolípides. Considera-se síndrome antifosfolípide primária (SAFP) quando não há outra doença autoimune ou inflamatória associada. Objetivos: Avaliar marcadores de reserva ovariana em mulheres com SAFP e a associação entre estes marcadores e dados clínicos, laboratoriais e anticorpo anti-corpo lúteo (anti-CoL). Métodos: Realizou-se estudo transversal em 18 pacientes com SAFP e 24 controles. A reserva ovariana foi avaliada na fase folicular precoce através das dosagens de hormônio folículo estimulante (FSH), hormônio luteinizante (LH), estradiol e hormônio anti-Mülleriano (HAM), pela técnica de ELISA, e contagem ultrassonográfica de folículos antrais (CFA). O anti-CoL foi avaliado através de immunoblot. Todas as análises foram realizadas após suspensão de contraceptivo hormonal por, no mínimo, 6 meses e retorno das menstruações. O teste t foi utilizado para comparar médias ± desvio padrão e o teste de Mann-Whitney, para comparar medianas (variação). O teste exato de Fisher foi utilizado para comparar diferenças entre variáveis categóricas. Adotou-se nível de significância de 5% (p<0,05). Resultados: A média da idade foi similar em pacientes com SAFP e controles (33,0 ± 5,0 vs. 30,4 ± 7,0 anos, p=0,19). Houve maior frequência de CFA baixa (<=10) (56% vs. 22%, p=0,04) e muito baixa (<=5) (37% vs. 9%, p=0,04) em pacientes com SAFP quando comparadas aos controles. Em relação ao HAM, observou-se tendência de maior frequência de concentração sérica reduzida (<1,0 ng/mL), baixa (<0,5 ng/mL) e muito baixa (<0,2 ng/mL) em pacientes com SAFP (p=0,08; p=0,07 and p=0,07; respectivamente). As concetrações séricas de FSH, LH e estradiol foram semelhantes em pacientes e controles (p>0,05). Não houve associação entre baixa reserva ovariana e tipos específicos de anticorpos antifosfolípides. A presença do anti-CoL foi observada apenas em pacientes com SAFP (11% vs. 0%, p=0,177) e não foi relacionada a parâmetros de reserva ovariana. Conclusões: Pacientes com SAFP apresentaram reserva ovariana diminuída, com prevalência maior do que 50%, o que reforça o aconselhamento reprodutivo e planejamento familiar / Introduction: Antiphospholipid syndrome is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity associated with antiphospholipid antibodies. Primary APS (PAPS) is diagnosed when no other autoimmune or inflammatory diseases are present. Objective: to determine ovarian reserve in PAPS women and to evaluate the association between ovarian reserve tests and clinical and laboratorial parameters, and anti-corpus luteum antibody (anti-CoL). Methods: In this cross sectional study, 18 PAPS patients and 24 healthy women were evaluated at early follicular phase with measurement of follicle stimulating hormone (FSH), estradiol, and anti-Müllerian hormone (AMH), carried out by ELISA test, and sonographic antral follicle count (AFC). Serum measurement of anti-CoL was determined by immunoblot analysis. All analyses were performed after at least 6 months from the last intake of hormonal contraceptive and resumption of menstruation. Data were compared by t-test and Mann-Whitney test in continuous variables and by Fisher\'s exact test in categorical variables. The level of significance was set at 5% (p<0.05). Results: The mean age was comparable in PAPS and controls (33.0 ± 5.0 vs. 30.4 ± 7.0 years; p=0.19). Regarding ovarian reserve tests, the frequencies of low AFC (<= 10) (56% vs. 22%, p=0.04) and very low AFC (<= 5) (37% vs. 9%, p=0.04) were significantly higher in PAPS patients than controls. Trends of higher frequencies of reduced (<1.0 ng/mL), low (<0.5 ng/mL) and negligible (<0.2 ng/mL) AMH levels were found in PAPS patients (p=0.08; p=0.07 and p=0.07; respectively). FSH, LH and estradiol were similar in patients and controls. There was no association between low ovarian reserve and specific types of antiphospholipid antibodies. Anti-CoL was solely observed in PAPS patients (11% vs. 0%; p=0.177) and was not related to ovarian reserve tests. Conclusion: Women suffering from PAPS possessed reduced ovarian reserve, with prevalence greater than 50%, emphasizing fertility counseling and family planning

Les performances reproductrices des espèces d’intérêt agronomique sont dépendantes d’une régulation minutieuse de la folliculogenèse ovarienne. Parmi les régulateurs impliqués, il y a les facteurs de croissance fibroblastiques (FGFs), stimulant notamment la phosphorylation des protéines kinases activées par des agents mitogènes (MAPKs), afin de contrôler le devenir du follicule mais aussi les évènements qui y sont associés tels que la stéroïdogenèse, l’angiogenèse, la formation du corps jaune. Dans plusieurs types cellulaires non ovariens, des phosphatases à double spécificité (DUSPs), dont l’expression est induite en réponse à des facteurs de croissance, déphosphorylent les MAPKs. La présence et la régulation des DUSPs dans l’ovaire des mammifères est cependant peu documentée. Ces travaux de thèse avaient ainsi pour objectifs, (1) de déterminer la présence des DUSPs, (2) leur régulation par les FGFs et (3) leur rôle dans les cellules de granulosa de vache et de brebis. Dans la première étude effectuée chez la brebis, les ARNm codant pour 16 DUSPs ont été détectés, et leur profil d’expression a été dressé dans des cellules de granulosa issues de follicules antraux. Puis, les niveaux d’ARNm pour DUSP1, DUSP2, DUSP5 et DUSP6, ainsi que les niveaux de protéines pour DUSP1 et DUSP6 ont été augmentés par FGF2 mais pas par FGF8 ou FGF18. L’inhibition de DUSP1/6 et DUSP1 a également suggéré un rôle pour DUSP6 dans la déphosphorylation de MAPK8 chez la brebis. Avec la deuxième étude chez la vache, il ressort que la régulation de ces trois DUSPs semble bien conservée car les niveaux d’ARNm pour DUSP1, DUSP5 et DUSP6 et de protéines pour DUSP5 et DUSP6 ont été augmentés en réponse à FGF2. De plus, en s’intéressant au contrôle de l’expression de DUSP1, DUSP5 et DUSP6, il est ressorti que l’accumulation d’ARNm pour DUSP5 et DUSP6 nécessitait l’activation de MAPK3/1, et la signalisation calcique pour les ARNm pour DUSP6. D’après l’ensemble de ces données, DUSP1, DUSP5 et DUSP6 sont régulées de manière complexe dans les cellules de granulosa, et peuvent être désignées comme des phosphatases participant à la signalisation des FGFs ; cela contribue ainsi à une meilleure compréhension des mécanismes régulatoires de la folliculogenèse chez les ruminants. / The reproductive performance of species of agronomic interest is dependent on the careful regulation of ovarian folliculogenesis. Among the regulators involved are fibroblast growth factors (FGFs) that stimulate the phosphorylation of mitogen-activated protein kinases (MAPKs) to control the fate of the follicle and associated events such as steroidogenesis, angiogenesis and corpus luteum formation. In several non-ovarian cell types, dual specificity phosphatases (DUSPs), whose expression is induced in response to growth factors, dephosphorylate MAPKs. However, the presence and regulation of DUSPs in the mammalian ovary are poorly documented. The objectives of this thesis were (1) to determine the presence of DUSPs, (2) their regulation by FGFs and (3) their role in cow and sheep granulosa cells. In the first study in sheep, mRNAs encoding 16 DUSPs were detected and profiled in granulosa cells from antral follicles. Subsequently, DUSP1, DUSP2, DUSP5 and DUSP6 mRNA levels, as well as proteins for DUSP1 and DUSP6, were increased by FGF2 but not FGF8 or FGF18. Inhibition of DUSP1/6 and DUSP1 also suggested a role for DUSP6 in the dephosphorylation of MAPK8 in sheep. In the second study in the cow, the regulation of these three DUSPs appeared to be well conserved as DUSP1, DUSP5 and DUSP6 mRNA levels and DUSP5, DUSP6 protein levels were increased in response to FGF2. In addition, by focusing on the control of DUSP1, DUSP5 and DUSP6 expression, it was found that the accumulation of DUSP5 and DUSP6 mRNAs required the activation of MAPK3/1, and calcium signaling for DUSP6 mRNA. Taken together, these data suggest that DUSP1, DUSP5 and DUSP6 are regulated in a complex manner in granulosa cells, and can be designated as phosphatases involved in FGF signaling, thus contributing to a better understanding of the regulatory mechanisms of folliculogenesis in ruminants.