Intracytoplasmic Sperm Injection after Vitrification of Immature Oocytes in Follicular Fluid Increases Bovine Embryo Production

ABSTRACT

Background: Despite the low efficiency caused by its harmful effects, vitrification is the technique of choice for oocyte cryopeservation, especially at the germinal vesicle (GV) stage. This enables the banking of female gametes without linkage to the male genotype. Follicular fluid (FF), in vivo, is known to provide an adequate environment to the immature oocyte. The intra-cytoplasmic sperm injection (ICSI), by the other hand, can be used to bypass any sperm penetration disorder, including the ones caused by cryopreservation. This study aimed to evaluate oocyte vitrification in FF based solution, and to asses ICSI efficiency in the fertilization of vitrified/warmed bovine GV oocytes.Material, Methods & Results: Follicles of 2-8 mm in diameter were aspirated from bovine ovaries obtained from a slaughterhouse, selected and maintained into FF from aspiration, until their allocation in the experimental groups. The FF used to prepare the vitrification solution was centrifuged, heat inactivated, filtered through a 0.22 mm pore and stored at -20C. Oocyte vitrification was done into one of these three solutions The standard solution TCM-Hepes (TH-Vitri) was compared to a totally FF based solution (FF-Vitri), and to a 5050 (v/v) mix of both solutions (THFF-Vitri). Oocytes were submitted to in vitro embryo production in order to assess embryo production efficiency. A second set