Effects of granulosa cell co-culture on preimplantation development of cloned bovine embryo

Abstract

In 1996, the use of Somatic cell nuclear transfer (SCNT) technology to the birth of Dolly sheep - the first cloned mammal in the world opened up a lot of new research options. However, several objective factors greatly affect the success rate of the mentioned method as well as give us a low rate of embryo formation. Meanwhile, co-culture method is reported to increase efficiency in embryo formation and stimulate embryo growth. The aim of this study was to co-culture granulosa cells with bovine oocytes to evaluate their impact on embryonic developmental competence associated with oocytes that subsequently reach or not the blastocyst stage. The embryos incubated in a medium without granulosa cells would serve as a control, while the other group would be evaluated and compared to the control group. The embryo's developmental phases would be documented, and the quality of each embryo would be carefully reviewed. Reconstructed oocytes proceeded through five major stages: 2-cell stage, 4-cell stage, 8-cell stage, morula stage, and blastocyst stage. All of this would be recorded and quantified in order to determine the rate of development as well as the effect of co-culture on the embryos. The results showed that treatment with granulosa cell coculture could considerably increase the embryo development in three replications. Although the rate of embryonic development from 2-cell stage to 8-cell stage within co-culture group was not significantly different with those recorded in control group, the data still indicated that the higher proportion in number of embryo growth obtained from two co-culture groups in every single stage. When it comes to the blastulation, the rate of blastocyst formation is recorded as 41.45% which has increased manyfold compared to the control group (P<0.05). Besides, co-culture enhances the quality of bovine blastocysts generated by SCNT via the increase in the total cell number of yielded blastocysts in the tested group