title: Laser-assisted in vitro fertilization facilitates fertilization of vitrified-warmed C57BL/6 mouse oocytes with fresh and frozen-thawed spermatozoa, producing live pups.
abstract: The utility of cryopreserved mouse gametes for reproduction of transgenic mice depends on development of assisted reproductive technologies, including vitrification of unfertilized mouse oocytes. Due to hardening of the zona pellucida, spermatozoa are often unable to penetrate vitrified-warmed (V-W) oocytes. Laser-assisted in vitro fertilization (LAIVF) facilitates fertilization by allowing easier penetration of spermatozoa through a perforation in the zona. We investigated the efficiency of V-W C57BL/6NTac oocytes drilled by the XYClone laser, compared to fresh oocytes. By using DAP213 for cryoprotection, 83% (1,470/1,762) of vitrified oocytes were recovered after warming and 78% were viable. Four groups were evaluated for two-cell embryo and live offspring efficiency: 1) LAIVF using V-W oocytes, 2) LAIVF using fresh oocytes, 3) conventional IVF using V-W oocytes and 4) conventional IVF using fresh oocytes. First, the groups were tested using fresh C57BL/6NTac spermatozoa (74% motile, 15 million/ml). LAIVF markedly improved the two-cell embryo efficiency using both V-W (76%, 229/298) and fresh oocytes (69%, 135/197), compared to conventional IVF (7%, 12/182; 6%, 14/235, respectively). Then, frozen-thawed C57BL/6NTac spermatozoa (35% motile, 15 million/ml) were used and LAIVF was again found to enhance fertilization efficiency, with two-cell embryo rates of 87% (298/343) using V-W oocytes (P<0.05, compared to fresh spermatozoa), and 73% (195/266) using fresh oocytes. Conventional IVF with frozen-thawed spermatozoa using V-W (6%, 10/168) and fresh (5%, 15/323) oocytes produced few two-cell embryos. Although live offspring efficiency following embryo transfer was greater with conventional IVF (35%, 18/51; LAIVF: 6%, 50/784), advantage was seen with LAIVF in live offspring obtained from total oocytes (5%, 50/1,010; conventional IVF: 2%, 18/908). Our results demonstrated that zona-drilled V-W mouse oocytes can be used for IVF procedures using both fresh and frozen-thawed spermatozoa, producing live pups. The ability to cryopreserve mouse gametes for LAIVF may facilitate management of large-scale transgenic mouse production facilities.
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Woods
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Peimin
authors.initials: P
authors.lastname: Qi
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rosalia
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Tony
authors.initials: T
authors.lastname: Chavarria
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Allan
authors.initials: A
authors.lastname: Discua
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Mkandawire
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: James G
authors.initials: JG
authors.lastname: Fox
authors.affiliation: Transgenic Core Facility, Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Alexis
authors.initials: A
authors.lastname: García
mesh_terms: D000818:Animals; D002465:Cell Movement; D002470:Cell Survival; D015925:Cryopreservation; D004622:Embryo, Mammalian; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro; D007834:Lasers; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009865:Oocytes / Q000166:cytology*; D011247:Pregnancy; D018873:Pregnancy Rate; D013094:Spermatozoa / Q000166:cytology*