Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 68-82). Also available on the World Wide Web.

At birth, the mammalian ovary has a finite number of dormant primordial follicles. Repeated daily dosing of rats with the occupational chemical, 4- vinylcyclohexene diepoxide (VCD), depletes the ovary of small pre-antral follicles (primordial and primary follicles) through an increase in the natural process of atresia (apoptosis). In addition, in vitro exposure of postnatal day 4 (PND4) rat ovaries to VCD causes a similar depletion of ovarian follicles. Since many growth factors play crucial roles in the promotion of early folliculogenesis and follicle survival, it is possible that any number of factors and subsequent signaling pathways could be disrupted in response to VCD exposure. Therefore, the studies in this work address the hypothesis that VCD disrupts oocyte-granulosa cell survival pathways in the rat ovary, thereby compromising cell-cell communication and causing follicle cell death. The results from the first aim reveal that through the use of genomic analyses a subset of genes were determined to be affected via in vivo and in vitro exposure routes to VCD. The results of the second aim show that two transforming growth factor β (TGFβ) growth factors, growth and differentiation factor-9 (GDF-9), and bone morphogenetic factor-4 (BMP-4), are not likely involved in VCD-induced ovotoxicity as they were unable to prevent ovarian follicle loss in the presence of VCD. The results of the third aim reveal that expression of the c-Kit receptor, present on the oocytes, is decreased and its ligand, Kit Ligand (KL), produced from the granulosa cells, is increased in response to in vitro VCD exposure. In addition, attenuation of VCD-induced follicle loss occurs in the presence of exogenous KL. Finally, the results of the fourth aim examines the involvement of the AKT signaling molecule in response to VCD exposure, in which the active phosphorylated AKT is determined to be down-regulated by VCD. Taken together, these studies show that VCD is able to disrupt at least one of the cellular survival pathways that are crucial to maintain the ovarian follicle. As a result, a breakdown in cell-cell communication may occur at that level and contribute to an increase in follicular atresia and eventual cell death.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Magíster en biología de la reproducción / El Síndrome de Ovario Poliquístico (SOP), es una disfunción endocrino-ginecológica de alta prevalencia en mujeres en edad fértil (5 al 10%). Se estima que el 64% de estas pacientes pueden presentar hiperandrogenismo e hiperinsulinemia. Antecedentes de literatura sugieren que elevados niveles de andrógenos e insulina conducirían a una desregulación en la señalización de FSH, lo que explicaría en parte la disfunción en los procesos de esteroidogénesis y angiogénesis en el SOP. Las vías de señalización activadas por FSH no han sido completamente dilucidadas en esta patología, por esto su evaluación podría contribuir a explicar la disfunción en el desarrollo folicular de las mujeres con SOP. La hipótesis de este trabajo propone: “FSH activa las vías de señalización PKA, MAPK, PI3K y PKC modulando la esteroidogénesis y el potencial angiogénico en células de la granulosa luteinizadas humanas. El efecto estimulatorio de FSH sobre las vías de señalización esta desregulado en las células de la granulosa luteinizadas cultivadas en condiciones hiperinsulínicas e hiperandrogénicas, disminuyendo la esteroidogénesis y aumentando la angiogénesis”. Este estudio se realizó en células de la granulosa (CG) provenientes de mujeres normales que participan del Programa IVF debido a infertilidad por factor masculino exclusivo. Las CG, fueron cultivadas en medio control y en medio hiperinsulínico e hiperandrogénico (medio I+T), y estimuladas con FSH a diferentes tiempos. Los resultados muestran que FSH estimula la fosforilación de las vías PKA y MAPK, y la secreción de progesterona, las cuales disminuyeron significativamente en CG cultivadas en medio I + T comparado con el medio control (P<0,05). La presente investigación destaca que el potencial angiogénico y los niveles del factor pro-angiogénico, VEGF, fueron significativamente mayores en CG estimuladas con FSH en medio I + T comparándolas con el medio control (P<0,05). FSH regula el potencial angiogénico, la secreción de VEGF y progesterona, a través de la vía de señalización MAPK, mientras que la vía de señalización PKA, dependiente de FSH, solo estaría regulando la producción de progesterona. Estos resultados sugieren, que el exceso de andrógenos e insulina alteran el microambiente folicular, modificando el efecto de FSH sobre las vías de señalización que regulan la esteroidogénesis y la angiogénesis. / Polycystic Ovarian Syndrome (PCOS) is an endocrine-gynecological dysfunction with high prevalence in fertile women (5 to 10%). It is estimated that 64% of these patients may present hyperandrogenism and hyperinsulinemia. Is believed that high levels of androgens and insulin would lead to deregulation of FSH signaling. This notion could explain a dysfunction in the processes of steroidogenesis and angiogenesis in PCOS. The signaling pathways activated by FSH have not been completely elucidated in this pathology, therefore its evaluation could contribute to explain the dysfunction in the follicular development of women with PCOS. The hypothesis of this work was: "FSH activates the signaling pathways PKA, MAPK, PI3K and PKC that are involved in steroidogenesis and angiogenic potential in human luteinized granulosa cells. The FSH stimulatory effect on signaling pathways is deregulated in luteinized granulosa cells cultured under hyperinsulinic and hyperandrogenic conditions, decreasing steroidogenesis and increasing angiogenesis ". This study was performed on granulosa cells (GC) collected from normal women participating in the IVF Program due to exclusive male factor infertility. GC, were cultured in control medium and in hyperinsulinic and hyperandrogenic medium (I + T medium), and stimulated with FSH at different times. The results show that FSH stimulates phosphorylation of the PKA and MAPK pathways, and progesterone secretion, which decreased significantly in GC cultivated in I + T medium compared to the control medium (P <0.05). Interestingly, angiogenic potential and VEGF, pro-angiogenic factor levels, were significantly higher in GC stimulated with FSH in I + T medium compared to the control medium (P <0.05). FSH regulates the angiogenic potential, secretion of VEGF and progesterone through the MAPK signaling pathway, whereas the PKA signaling pathway, FSH dependent, only regulates the production of progesterone. These results suggest that excess androgens and insulin alter the follicular microenvironment, modifying the effect of FSH on the signaling pathways that regulate steroidogenesis and angiogenesis.

Graduation date: 1999

Graduation date: 1996

Thesis (Ph. D.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thèse (M.Sc.)--Université Laval, 2008. / Bibliogr.: f. 126-136. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.