| In vitro systems for ovarian follicle maturation will provide an important link for clinicians to help women and young girls preserve their fertility, which may be compromised due to cancer or other disorders. Cryopreservation of ovaries, and thus the follicles which contain the egg, has been proposed; however, a critical limitation is the insufficient supply of meiotically competent oocytes obtained. The majority of follicles that survive freezing and thawing are immature follicles which will require further development prior to fertilization of the egg. Therefore, systems must be developed to allow these follicles to mature in vitro. The methods developed in this thesis represent an important advancement permitting the development of egg banks from which fertility needs can be met.; By merging principles from tissue engineering with those from follicle biology, I have developed synthetic matrices that promote follicle maturation to produce meiotically competent oocytes. Ovarian follicles are isolated from immature mice and encapsulated and cultured within alginate matrices to maintain an in vivo-like architecture, resulting in follicle maturation and development of meiotically competent oocytes. Utilizing the alginate scaffold, I examined the regulation of granulosa cell and follicle development by the extracellular matrix (ECM) and follicle stimulating hormone (FSH) in a three-dimensional culture system. The emerging picture of follicle development from these studies is that as the follicle progresses through development, it has distinct responses to these stimuli. For example, the transition from secondary to preantral follicle is FSH responsive and promoted by collagen I and RGD peptide modification; additionally, differentiation of these immature granulosa cells is promoted by RGD peptide in isolated granulosa cell cultures. The transition from preantral to antral follicle is FSH dependent and delayed by laminin or fibronectin modification. It is important to note that these distinct signals integrate to regulate the quality of the oocyte, the critical determinant of whether a culture system can be utilized for embryo production. These studies indicate that the extra-follicular ECM milieu and endocrine signals such as FSH both direct this developmental process in vitro, providing a new and exciting method to regulate follicle development for fertility restoration. |
