Research Progress on Vitrification Injury of Oocytes in Livestock
Vitrification cryopreservation of oocytes is crucial for accelerating the livestock breeding,increasing the production efficiency,maintaining the species diversity,and rescuing endangered species.At present,the vitrification technique has been widely used in the oocyte cryopreservation of various domestic animals including pig,cow,and sheep.Nevertheless,compared with fresh oocytes,the competence of maturation,fertilization,cleavage,and blastocyst formation from vitrified oocytes was still greatly compromised.It dramatically discourages the practical application of oocyte cryopreservation.The freezing injury is the key factor determining the efficiency and quality of oocyte cryopreservation.It includes broken zona pellucida,membrane lipid phase transition,DNA damage,chromosomal abnormalities,aberrant distribution of cortical particles,impaired structure and function of endoplasmic reticulum and mitochondria,and abnormal spindle morphology.Furthermore,vitrification could cause the disorders of cell physiological state,such as oxidative stress and calcium dyshomeostasis,which are related with the compromised oocyte development.To further increase the effectiveness of oocyte vitrification and facilitate the improvement of cryopreservation technology,it is necessary to clarify the underlying mechanisms of freezing injury.The author reviews the types,origins,and repair strategies of various freezing injuries to provide reference for improving the efficiency and quality of oocyte vitrification.