Centrosome abnormalities during porcine oocyte aging.

Centrosomes are critically important for maintaining meiotic spindle integrity in the meiosis II (MII) stage where oocytes are arrested in most mammalian species before fertilization takes place. In women of advanced ages or during in vitro fertilization (IVF) procedures, aneuploidy is frequently seen as a result of oocyte aging, which is strongly related to centrosome instability. Abnormal distribution of centrosomes and microtubules has been reported in aging human and mouse oocytes. This study reports the dynamic changes of centrosomes and the microtubule cytoskeleton in porcine oocytes during aging and treatment by caffeine to restore spindle integrity in aging oocytes. We tested the effects of caffeine on the MII spindle with focus on microtubules and on the centrosome proteins gamma-tubulin and NuMA (nuclear mitotic apparatus protein). The results revealed that in porcine oocytes aged for 48 hr., centrosomes were absent and spindles became abnormal and disorganized; however, caffeine could prevent these changes or restore centrosome integrity in the meiotic spindle poles and displayed similar MII spindles as those seen in fresh oocytes.