Expression Profiles of Genes Controlling Maturation of Sheep Cumulus Oocyte Complexes follow Vitrification

Ebrahimi B *, Rezazadeh Valojerdi M , Eftekhari Yazdi P , Baharvand H ,


Objective: This study was conducted to compare the expression of maturation genes of sheep cumulus-oocyte complexes follow vitrification by conventional and cryotop methods. Materials and Methods: cumulus-oocyte complexes (COCs) were harvested from slaughtered sheep ovaries. COCs were divided into three groups: Control Conventional Vitrification & Cryotop Vitrification. In control group COCs were transferred immediately to in vitro maturation medium (IVM). Vitrification was done by DMSO& EG. The viability of vitrified-warmed COCs was assessed morphologically. Vitrified-warmed COCs were matured like the control group and oocytes nuclear stage was determined by Hoechst staining. Oocytes were subjected for assessment of maturation genes expression by Real-Time quantitative RT-PCR. Results: Cryotop vitrification had higher percent of healthy COCs after warming (83.84%) and also showed a significant difference with conventional vitrification. Mature oocytes (MII) were 51.94% and 48.81% in the control and cryotop groups respectively. Conventional vitrification showed a significant difference with control group in the expression of GDF9 BMP15 & BMPRII genes also GDF9 & BMP15 in the conventional vitrification had a significant difference with cryotop vitrification. The relative expression of BMP15 & BMPRII was significantly different between control and cryotop groups. ALK5 expression was evaluated too. Conclusion: According to the less success of immature sheep oocytes cryopreservation it seems that vitrification by cryotop can reduce cryoinjuries and increase the viability post-thaw quality and maturation rate of COCs. This kind of vitrification causes the least expression changes of maturation genes in comparison with conventional vitrification.