Human fetal ovarian culture permits meiotic progression and chromosome pairing process

Background: The female meiotic process seems to be crucial for aneuploidy in humans. The first stages of mammalian female meiosis take place during the fetal period. Therefore, only little is known about female meiosis. The goal of this study was to develop a culture technique that permits human oocytes to progress through meiotic prophase, to provide a system to study human female meiosis. Method: Fetal ovaries from four cases were cultured up to 35 days in α-minimal essential medium, 2% human serum albumin, 5 μg/ml insulin, 5 μg/ml transferrin, 5 ng/ml selenium and 100 IU/ml penicillin-100 μg/ml streptomycin. Results and conclusions: Although ovarian response to culture conditions varied, human oocytes survived in vitro up to 5 weeks. In three cases, we observed significant variation in stages of meiosis among the cultures. The homologous chromosome pairing process was studied for the first time in cultured oocytes, and the results suggested that the pairing process was completed following the same features described previously for euploid oocytes, as followed by the chromosome-13 pairing process and synaptonemal complex formation. Although a higher proportion of degenerated oocytes were observed as culture time increased, we also observed oogonial entrance to meiotic prophase.