Gene expression profiling of human oocytes at different maturational stages and after in vitro maturation

The purpose of this study was to catalog genes expressed in human oocytes at germinal vesicle (GV) or metaphase II (MII) stage and to compare gene profiles between oocytes matured in vivo (in vivo-MII) and in vitro (IVM-MII).

University-based research utilizing unfertilized oocytes analyzed for > 29,000 genes with RNA amplification and microarray.

GV, in vivo-MII, and IVM-MII oocytes expressed 12,219, 9735, and 8510 genes, respectively. There was extensive overlap among the 3 groups, but also some significant differences. In particular, in vivo-MII and IVM-MII oocytes shared very similar patterns of gene expression. However, some immature patterns of expression, reminiscent of GVs, persisted in IVM-MIIs.

In vitro maturation is an attractive strategy for IVF treatment; however, current IVM methods produce oocytes that perform poorly in the context of IVF. Data from the current study suggest that although IVM-MII oocytes closely resemble in vivo-MII oocytes for cellular pathways related to nuclear maturity, several pathways associated with cytoplasmic functions continue to be expressed in an immature manner. Additionally, IVM-MII oocytes have differences in the expression of genes related to cellular storage and homeostasis. Differentially expressed genes/pathways provide clues for the optimization of IVM techniques.