title: Lack of calcium oscillation causes failure of oocyte activation after intracytoplasmic sperm injection in pigs.
abstract: In pigs, the efficiency of embryo production after intracytoplasmic sperm injection (ICSI) is still low because of frequent failure of normal fertilization, which involves formation of two polar bodies and two pronuclei. To clarify the reasons for this, we hypothesized that ICSI does not properly trigger sperm-induced fertilization events, especially intracellular Ca2+signaling, also known as Ca2+oscillation. We also suspected that the use of in vitro-matured oocytes might negatively affect fertilization events and embryonic development of sperm-injected oocytes. Therefore, we compared the patterns of Ca2+oscillation, the efficiency of oocyte activation and normal fertilization, and embryo development to the blastocyst stage among in vivo- or in vitro-matured oocytes after ICSI or in vitro fertilization (IVF). Unexpectedly, we found that the pattern of Ca2+oscillation, such as the frequency and amplitude of Ca2+rises, in oocytes after ICSI was similar to that in oocytes after IVF, irrespective of the oocyte source. However, half of the oocytes failed to become activated after ICSI and showed no Ca2+oscillation. Moreover, the embryonic development of normal fertilized oocytes was reduced when in vitro-matured oocytes were used, irrespective of the fertilization method employed. These findings suggest that low embryo production efficiency after ICSI is attributable mainly to poor developmental ability of in vitro-matured oocytes and a lack of Ca2+oscillation, rather than the pattern of oscillation.
authors.affiliation: Division of Animal Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Ibaraki 305-8602, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Nakai
authors.forename: Junya
authors.initials: J
authors.lastname: Ito
authors.forename: Shun-Ichi
authors.initials: SI
authors.lastname: Suzuki
authors.forename: Dai-Ichiro
authors.initials: DI
authors.lastname: Fuchimoto
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Sembon
authors.forename: Misae
authors.initials: M
authors.lastname: Suzuki
authors.forename: Junko
authors.initials: J
authors.lastname: Noguchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaneko
authors.forename: Akira
authors.initials: A
authors.lastname: Onishi
authors.forename: Naomi
authors.initials: N
authors.lastname: Kashiwazaki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D008297:Male; D009865:Oocytes / Q000378:metabolism*; D020554:Sperm Injections, Intracytoplasmic / Q000662:veterinary*; D013094:Spermatozoa / Q000378:metabolism*; D013552:Swine
chemical_list: D002118:Calcium