Ultrastructure and Development of Vitrified/Warmed Bovine Oocytes Matured with 9-cis Retinoic Acid

Abstract

In this work we analyze the effects of vitrification on the ultrastructure and developmental ability of bovine oocytes matured in the presence of 9-cis-retinoic acid (RA). Bovine cumulus oocyte complexes (COCs) were matured in a basic medium containing 10% fetal calf serum (FCS), 9-cis-RA or polyvinyl alcohol (PVA). Mature oocytes were vitrified using the Open Pulled Straw method with minor modifications. A group of fresh and vitrified/warmed COCs was fixed for ultrastructural analysis, while the remaining oocytes were fertilized in vitro and cultured. Vitrification of mature oocytes produced high rates of degeneration regardless of the in vitro maturation protocol and low number of cleaved embryos. Development rates up to day 8 were similar between groups undergoing vitrification, which were lower than fresh controls. Morphologic alterations were observed in all groups of vitrified oocytes, although in vitro maturation in the presence of 9-cis-RA combined with vitrification led to higher ultrastructural damage. More research is needed to explain the low survival rates of the bovine oocyte after vitrification and warming. 123

Decreased Expression of CD9 in Bovine Oocytes After Cryopreservation and the Relationship to Fertilization Capacity

“…At the present time, however, bovine oocytes are less likely to survive cryopreservation than cleavage‐stage embryos. Bovine oocytes frozen to −196°C exhibit various degrees of cryoinjury, such as damaged zona pellucida (ZP), fragmented cytoplasm, indistinct oolema, increased perivitelline space (Rodríguez et al, ), ruptured mitochondria (Abe et al, ; Hu et al, ), microtubule depolymerization and DNA fragmentation (Stachowiak et al, ; Sharma et al, ; Hara et al, ), and spindle disorganization and disrupted chromosomes (Morato et al, ). Such cryoinjuries negatively impact subsequent development and limit the potential application of cryopreservation.…”

Viability of bovine in vitro matured oocytes following ultra-rapid vitrification

“…It was reported [32][33][34][35], that vitrification process causes changes in the mitochondrial morphology and functions in bovine oocytes. The ultrastructure often shows reduced matrix density in mitochondria with vacuolization and membrane damage [36,33] which were confirmed in our study.…”

“…It was reported [32][33][34][35], that vitrification process causes changes in the mitochondrial morphology and functions in bovine oocytes. The ultrastructure often shows reduced matrix density in mitochondria with vacuolization and membrane damage [36,33] which were confirmed in our study. Nevertheless, organelle alterations in warmed oocytes revealed in our study seem to be reversible, and some post-warm incubation is needed to restore injuries.…”