Mesut Çevik

Effects of leukemia inhibitory factor and insulin-like growth factor-I on the cell allocation and cryotolerance of bovine blastocysts

The present study examined the developmental capacity and cryotolerance of cultured bovine embryos in defined media (synthetic oviduct fluid, SOF) supplemented with insulin-like growth factor I (IGF-I) and leukemia inhibitor factor (LIF). The objectives of the present study were: (1) to examine the effects IGF-I and LIF on bovine embryo development potential and (2) to investigate the cryotolerance and survivability of vitrified blastocysts obtained from embryos cultured in a defined media. We studied the development of bovine embryos produced in vitro and cultured (in four different treatments) until Day 7 after fertilization. In Experiment 1, zygotes were cultured to the blastocyst stage and differentially stained for determine the count of cells. In Experiment 2, zygotes were vitrified before staining. LIF alone or combined with IGF-I was significantly effective on in vitro bovine embryo development especially ratio to reach blastocyst. The cells for both ICM and TE decreased by the effect of freezing in all treatment groups in the Experiment 2 compared with Experiment 1. Interestingly, the LIF treatment showed fewest variations. In addition to this, for average number of ICM and TE cells, LIF treatment showed fewest variation compared with other treatments (ICM: 23.5 vs 19.5, TE: 53.6 vs 51). These results are the first to demonstrate that the addition of IGF-I along with LIF to the culture medium was found to be beneficial for bovine embryonic development based on cellular cryotolerance after vitrification.

Effect of growth factors on oocyte maturation and allocations of inner cell mass and trophectoderm cells of cloned bovine embryos.

This study was conducted to determine the additive effects of exogenous growth factors during in vitro oocyte maturation (IVM) and the sequential culture of nuclear transfer (NT) embryos. Oocyte maturation and culture of reconstructed embryos derived from bovine granulosa cells were performed in culture medium supplemented with either epidermal growth factor (EGF) alone or a combination of EGF with insulin-like growth factor-I (IGF-I). The maturation rates of oocytes matured in the presence of EGF or the EGF + IGF-I combination were significantly higher than those of oocytes matured in the presence of only fetal calf serum (FCS) (P 0.05). IGF-I alone or in combination with EGF in sequential embryo culture medium significantly increased the ratio of inner cell mass (ICM) to total blastocyst cells (P < 0.05). Our results showed that the addition of growth factors to IVM and sequential culture media of cloned bovine embryos increased the ICM without changing the total cell number. These unknown and uncontrolled effects of growth factors can alter the allocation of ICM and trophectoderm cells (TE) in NT embryos. A decrease in TE cell numbers could be a reason for developmental abnormalities in embryos in the cloning system.