Ovarian follicle development is a complex process that requires bidirectional communication between a centrally located oocyte and its surrounding somatic cells. Paracrine, autocrine, and endocrine signaling play vital roles in this developmental process, and numerous signaling pathways have been identified as key regulators of follicle maturation. We investigated the patterns of gene expression during the process of follicle maturation in vivo for comparison with those during in vitro follicle maturation. Primary, two-layered secondary, and multi-layered secondary follicles were isolated from mouse ovaries for gene expression analysis. Through the use of Illumina Beadarray technology, gene expression profiles of in vivo growing follicles at these three different stages of development were examined and a subset of differentially expressed genes were identified. Of most interest, insulin-like growth factor 1 and transforming growth factor beta receptor II were up-regulated and the glycoprotein and sperm receptor zona pellucida 3 was down regulated during folliculogenesis. Biological interpretation of the microarray data, facilitated by Ingenuity Pathway Analysis, indicated that the beta-estradiol, Akt, and tumor necrosis factor pathways might also be tied to proper development. Transcript abundance of genes well known to be involved in the developmental process as well as novel genes uncovered from the microarray analysis was confirmed by real time PCR. A culture system based on encapsulating immature follicles in alginate hydrogels has been developed to facilitate in vitro follicle maturation. Real time PCR analysis of in vitro grown follicles indicates that the expression patterns for several genes mimic that observed in vivo. These studies are leading to the development of a culture environment that more closely mimics the in vivo ovarian environment, allowing for maximal follicle growth, viability, and maturation.

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