LH Plays a Role to Enhance the Nuclear and Cytoplasm Synchronization During In vitro Maturation of Ovine Oocytes

This study is aimed to investigate the effect of luteinizing hormone (LH) on maturation and fertilization in vitro of ovine oocytes. The ovine oocytes were cultured in vitro in medium with or without LH, and then checked by confocal laser scanning microscope to observe the distribution of cortical granules stained with FITC-LCA during different maturation periods. Similarly, some in vitro matured oocytes were also fertilized in vitro for analysis of their developmental potentiality further. After being cultured in vitro for 4 h, there were significant differences about the rate of germinal vesicle break down (GVBD) between the treatment (with LH) and the control groups (without any hormones) (36.76% vs 18%, P<0.05). Further, there were also significant differences of the cleavage and blastocyst rates between these two groups (67.15% vs 42.37%, 21.9% vs 12.71%, P<0.05, respectively). The distribution of cortical granules appeared to spread from the edges to the central site of sheep oocytes following their delaying durations of maturation in vitro. It can be concluded that LH may play a role to delay the occurence of GVBD, prolong the maturation duration of cytoplasm, and enhance the nuclear and cytoplasm synchronization of ovine oocytes matured in vitro and finally improve their in vitro developmental potentiality.