105 COMPARATIVE ULTRASTRUCTURE OF IN VITRO-PRODUCED BOVINE BLASTOCYSTS (BOS INDICUS) DERIVED FROM IN VITRO FERTILIZATION, SNC, AND PARTHENOGENESIS

Abstract

It is known that embryos produced in vitro may have structural alterations that often compromise the normal embryo development, generating a high rate of pregnancy loss. The study of these changes is of great importance because it may elucidate the cause of embryonic loss during the first trimester of pregnancy. Thus, the objective of this study was to characterize and compare ultrastructurally bovine blastocysts in the 7th day of development produced by IVF, cloning by somatic cell nuclear transfer (SCNT), and parthenogenesis. In vitro-produced embryos were derived from in vitro-matured oocytes. The somatic cell used to make cloning was fibroblasts of adult cows, and the protocol for parthenogenetic activation of the embryos was done with ionomycin-DMAP. The blastocysts derived from the different experimental groups were fixed in 2.5% glutaraldehyde and processed for transmission electron microscopy evaluation. The results showed that blastocysts derived by SNC and parthenogenesis exhibited a significantly reduced size; the inner cell mass and the blastocoel were not well defined compared with IVF embryos, indicating a less-advanced state of development. Furthermore, organelles of blastocysts derived from SCNT and parthenogenesis were fewer in number and had changes in form, when compared with IVF blastocysts. In parthenogenetic embryos there was the presence of phagosomes, suggesting a high degradation activity of cellular. Mitochondria showed the most significant changes. Although they occur in large quantities in all blastocysts, the morphology of them was impaired in SNC and parthenogenetic embryos (vacuolization, abnormal shape). Such modifications could suggest changes in mitochondria functionality, which may decrease cellular metabolic activity. Thus, we find that the D7 blastocysts derived from SCNT and parthenogenesis showed several ultrastructural differences compared with IVF embryos, with particular reference to a reduced number and morphology of embryo organelles.