Successful in vitro maturation of oocytes: a matter of follicular differentiation.

Folliculogenesis is remarkably similar in cattle and humans. In this review, we consider the known differences and provide a possible explanation for the greater success of oocyte in vitro maturation in cattle. Two different parallel processes that are critical for oocyte competence acquisition are examined. The first occurs in the follicle and in turn influences the oocyte, the second occurs within the oocyte itself and involves the gradual cessation of the transcription machinery with additional changes observable in the chromatin structure. We expect this insight to contribute to the improvement of human fertility programs based on in vitro fertilization, and particularly to the development of controlled ovarian stimulation protocols that yield more high-quality oocytes and thereby improve the clinical performance of treatments for infertility.