Search

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 (Δ Ψ m) 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. The female reproductive system is more vulnerable to ageing, and advanced maternal age affects embryo development. Pre-implanted embryos grown in the lab also exhibit ageing like characteristics due to in vitro conditions. We employed cycloastragenol, a naturally occurring substance with reported anti-aging and healing properties, in embryo growth media. Cycloastragenol greatly increased telomerase expression levels, enhanced embryo quality, and increased the embryo's ability for implantation. We suggest that cycloastragenol might constitute a valuable addition to media used for oocyte maturation and embryo development. [ABSTRACT FROM AUTHOR]

This study investigated the use of bovine serum albumin (BSA) plus insulin–transferrin–sodium selenite (ITS) and/or epidermal growth factor (EGF) as alternatives to fetal bovine serum (FBS) in embryo culture medium. The developmental ability and quality of bovine embryos were determined by assessing their cell number, lipid content, gene expression and cryotolerance, as well as the invasion ability of trophoblasts. The percentage of embryos that underwent cleavage and formed a blastocyst was higher (P < 0.01) in medium containing ITS plus EGF and BSA than in medium containing FBS. Culture with ITS plus EGF and BSA also increased the hatching ability of blastocysts and the total cell number per blastocyst. Furthermore, the beneficial effects of BAS plus ITS and EGF on embryos were associated with a significantly reduced intracellular lipid content, which increased their cryotolerance. An invasion assay confirmed that culture with ITS plus EGF and BSA significantly improved the invasion ability of trophoblasts. Real-time quantitative polymerase chain reaction analysis showed that the mRNA levels of matrix metalloproteinase-2 (MMP2) and MMP9 , acyl-CoA synthetase long-chain family member 3, acyl-coenzyme A dehydrogenase long-chain and hydroxymethylglutaryl-CoA reductase significantly increased upon culture with ITS plus EGF and BSA. Moreover, protein expression levels of matrix metalloproteinase-2 and -9 increased (P < 0.01) in medium supplemented with ITS plus EGF and BSA compared with medium supplemented with FBS. Taken together, these data suggest that supplementation of medium with ITS plus EGF and BSA improves in vitro bovine embryo production, cryotolerance and invasion ability of trophoblasts. Conventional media supplemented with fetal bovine serum (FBS) have the disadvantage of variations in serum from lot-to-lot that can affect the reproducibility of experimental findings. Here, we showed that supplementation of in vitro culture medium with insulin–transferrin–sodium selenite plus epidermal growth factor and bovine serum albumin, as alternatives to FBS, can consistently support the development of in vitro -produced bovine embryos and effectively improve invasion ability of trophoblasts via induction of matrix metalloproteinases. [ABSTRACT FROM AUTHOR]