The effects of cycloastragenol on bovine embryo development, implantation potential and telomerase activity

Abstract

Context Telomerase reverse transcriptase is a key factor responsible for structural and cellular alterations in aged oocytes and changes in the structure of the zona pellucida and mitochondria. Telomerase expression is reduced in aged cumulus oocyte complexes, and its activation or enhanced expression would be beneficial for in vitro oocyte maturation and in vitro embryo development. Aims This study aimed to investigate telomerase activation by cycloastragenol and its effect on bovine oocyte in vitro maturation, fertilisation, and early embryo development. Methods We used qPCR, Western blot, immunofluorescence, reactive oxygen species (ROS) assay,TUNEL assay, JC-1 assay, and invasion assay to analyse the affect of cycloastragenol (CAG) on bovine oocyte maturation, embryo development, embryo quality and implantation potential. Key results Cycloastragenol treatment of oocytes in in vitro maturation (IVM) media significantly (P < 0.05) improved oocyte IVM (90.87%), embryo cleavage (90.78%), blastocyst hatching (27.04%), and embryo implantation potential. Telomerase also interacts with mitochondria, and JC-1 staining results showed significantly (P < 0.05) higher mitochondrial membrane potential (ΔΨm) in the CAG-treated group. Furthermore, the inner cell mass (OCT4 and SOX2) and trophoblasts (CDX2) of the control and CAG groups were examined. Moreover, CAG treatment to primary cultured bovine cumulus cells substantially enhanced telomerase activity. Conclusions Telomerase activation via cycloastragenol is beneficial for bovine oocyte IVM and for the production of high-quality bovine embryos. Implications Cycloastragenol is a natural telomerase activator, and could be useful as a permanent component of oocyte maturation media.