Comparative stepwise pattern of reactive oxygen species production during in vitro development of fertilized and nuclear transferred goat embryos

A unique feature of embryo metabolism is production of reactive oxygen species (ROS). It is well established that during in vitro culture, ROS levels increase over normal ranges observed for embryos developed in vivo. This study evaluates and compares the stepwise pattern of ROS production during in vitro development of reconstructed goat embryos produced by zona-free method of somatic cell nuclear transfer (SCNT). Furthermore, the pattern of ROS production of SCNT embryos were compared with zona free embryos derived from in vitro fertilization (IVF).
In this experimental study, zona-free oocytes, SCNT and IVF embryos at different stages of in vitro development (2, 4, 8, 16-cells, morula, and blastocyst) were used for assessment of ROS production using 2, 7-dichloro dihydroflourescein diacetate (DCHFDA) probe and the result were presented as fold increase or decrease relative zona free oocytes.
The relative level of ROS compared to metaphase-II (MII) oocytes insignificantly decrease during early stages post embryo reconstitution and regained its value by 8-cell and morula stage and, significantly increase compared to MII oocytes by blastocyst stage.
The pattern of ROS change in SCNT embryos is similar to zona free IVF derived embryos, except it decrease from two cell stage and regain its value at morula stage. The sudden rise in ROS at blastocyst stage, further emphasizes the special need of IVF and SCNT derived embryos during this stage of development.