Vitrification assessment of buffalo (Bubalus bubalis)‎ oocytes : morphological and molecular aspects

Abstract EN

Successful cryopreservation of oocytes would preserve the genetic material from superior animals.

However, oocyte cryopreservation is relatively less successful comparing to embryos and spermatozoa due to the extreme sensitivity to chilling.

Therefore, the objective of this study was to determine the effect of vitrification process before or after oocyte maturation on the expression level of three quality related genes and on the nuclear and cytoplasmic maturation rates of vitrified immature buffalo oocytes.

Oocytes were collected and vitrified either immediately after collection as immature oocyte then thawed and matured in vitro (IV group) or vitrified after maturation (MV group).

Fresh collected and matured oocytes were used as control group.

Maturation rate was determined by cumulus cells expansion (cytoplasmic maturation) and by presence of first polar body (nuclear maturation).

The mRNA expression analysis was performed to assess the expression of three quality related genes (SOD1, BAX and MAPK14).

The results demonstrated that cryopreservation of immature oocytes did not affect cytoplasmic maturation but significantly reduced the extrusion of the first polar body to 10.6 % compared to 34.1% of control group.

BAX transcript showed no significant differences among all groups, although it was down-regulated in IV group and up-regulated in MV ones.

However, SOD1 was significantly (P< 0.05) down-regulated in MV group and up-regulated in IV group compared to control group.

MAPK14 was significantly (P< 0.05) down-regulated in IV group.

In conclusion, this study indicated the deleterious effect of vitrification process on nuclear maturation and expression level of the selected genes in buffalo oocytes.