Development Ability of Vitrified Mouse Oocytes Assessed by Two Fertilization Methods: Intracytoplasmic Sperm Injection (ICSI) and Laser Assisted IVF

Assessment of the development ability of oocytes following vitrification and thawing is an important step for the optimization of “in vitro” fertilization techniques. The classic “in vitro” fertilization of vitrified-thawed oocytes in mice is often inefficient because of incomplete capacitation of spermatozoa in the absence of surrounding cumulus cells. The aim of this study was to compare the fertilization and embryo development efficiency of vitrified-thawed oocytes assessed by two modern “ in vitro ” fertilization methods: Intracytoplasmic sperm injection (ICSI) and laser assisted IVF (ZD-IVF) and to overcome the incomplete capacitation of spermatozoa and the zona pellucida hardening following vitrification. A total of 110 oocytes, obtained from superovulated B6D2F1 females were vitrified using the OPS method and subsequently warmed on a later date. Surviving oocytes (n=96, 87.3%) were randomly allocated for fertilization by ICSI (n=56, group 1) or laser assisted IVF (n=60, group 2) using fresh spermatozoa from CD1 stud males. Fertilization was achieved in 37 (66%) of the oocytes from group 1 and 38 (63%) from group 2. The developmental rate of 4 cells stage embryos, morulae and blastocysts (36±60%, 35±58.5%, 19±53%) in the first group was similar comparing with the second group (34±60.7%, 32±57.1%, 28±50%). We conclude that the fertilization and embryo development efficiency of vitrified-thawed oocytes can be enhanced significantly using ICSI or Laser Assisted IVF. These data also suggest that by using one of these methods we can overcome the incomplete capacitation of spermatozoa and the zona pellucida hardening following vitrification.