ULTRASTRUCTURAL CHANGES IN PORCINE OOCYTES AFTER ULTRARAPID FREEZING

Abstract

The objective of the present study was to investigate the ultrastructural changes seen in frozen porcine oocytes at the germinal vesicle and during in vitro maturation when using an ultrarapid freezing technique. The morphological changes were assessed by transmission electron microscopy (TEM). Immature oocytes were collected from pig ovaries at a local slaughter house in Nakorn Prathom province. Some oocytes were matured in vitro for 44 hours at 39oC, 5% CO2 with high humidity. All oocytes were divided into four groups; immature (control group), the in vitro maturation group (control group), frozen immature and frozen mature oocytes. Electron microscopy was used to examine the fine structure of the frozen oocytes (group 3 and 4). The freezing technique induced ultrastructural changes when compared to the unfrozen oocytes inducing; less electron-lucent in the zona pellucida, degeneration of microvilli, extensive vacuolization, changes in the matrix density of the mitochondria and disruption of lipid droplets and the cytoplasmic vesicles membrane. In conclusion, the study showed that the ultrarapid freezing technique demonstrates similar morphological features for the porcine oocytes at both the germinal vesicle and the maturation stage.