The role of brain-derived neurotrophic factor in mouse oocyte maturation in vitro

Brain-derived neurotrophic factor (BDNF) can promote developmental competence in mammalian oocytes during in vitro maturation (IVM), but the role of BDNF in oocyte maturation at cellular level is not still clear. In this study, mouse cumulus-enclosed oocytes subjected to IVM were fertilized and cultured to blastocyst stage. Meiotic spindle configuration and cortical granules distribution during oocyte maturation in vitro were assessed by using immunofluorescence and laser confocal microscopy. The results showed that BDNF contributed to the complete preimplantation development of mouse oocytes compared to the control oocytes (13.78% vs. 5.92%; P<0.05). Further, BDNF did not accelerate nuclear maturation of IVM oocytes. For the BDNF-treated oocytes at meiosis I, Meiotic spindle areas were significantly smaller and the number of cytoplasmic microtubule organizing centers was greater than that in the control, and the percentages of oocytes showed spindles positioned near the oolemma and a well-formed cortical granule-free domain were significantly higher than that of the control. These morphological characteristics of the BDNF-treated oocytes were much closer to the oocytes matured in vivo than those of the control oocytes. In conclusion, BDNF can promote the developmental competence of mouse IVM oocytes, by improving the meiotic spindle configuration and location and cortical granules distribution at meiosis 1.