Effect of transportation in liquid nitrogen on viability of bovine oocytes

Oocyte cryopreservation has significantly increased as freezing technology improves. Excess oocytes obtained during assisted reproduction technology therapies can be stored safely and indefinitely with cryopreservation. This technology promises improvement in the establishment of oocytes banks, permitting female genetic material to be stored unfertilized until the desired male germplasm is selected. However, there is concern regarding the transportation effect as the movement to and from the central laboratory may have adverse effects on vitrified oocytes. Currently, studies on the effect of transportation towards the viability of oocytes are still scarce. Studies showed that vibrations that occur during transportation will disrupt the cells cytoskeleton. In contrast, it has also been suggested that the low frequency of vibration facilitates the pregnancy rate of embryo. The objectives of this study were 1) to investigate the effect of transportation on oocytes and 2) to determine the viability of oocytes after transportation. In this study, bovine ovaries that were collected from slaughterhouses were sliced to retrieve oocytes for in vitro maturation (IVM). After 24 hours of IVM, the oocytes were vitrified using open-pulled straw and plunged directly into liquid nitrogen. The vitrified oocytes were divided into three groups whereby one was the control group and other groups were exposed to vibrations of 180 and 300 rpm for one hour (to simulate transportation via airplanes and trucks), respectively. The viability of oocytes was examined using fluorescein diacetate stain. Result showed that there was no significant difference between control and experimental groups (P>0.05). The viability of control, truck and airplane groups recorded were 95%, 100% and 100%, respectively. The mechanical vibration is suggested to have no harmful effect but serves as a stimulation to induce intracellular communication which is essential in cell differentiation. In conclusion, the vibration had no adverse effect on the viability of vitrified bovine oocytes.