title: Germinal vesicle transfer between fresh and cryopreserved immature mouse oocytes.
abstract: BACKGROUND
  We assessed the maturational competence and the chromosomal pattern of mouse oocytes reconstructed by germinal vesicle (GV) transfer technique using nuclear and/or cytoplasmic components from cryopreserved GV stage oocytes.
  
  
  METHODS
  From 657 GV oocytes (326 fresh and 331 frozen/thawed), four groups of reconstructed oocytes were obtained by micromanipulation and electrofusion: fresh GV-fresh cytoplast (FF), thawed GV-thawed cytoplast (TT), fresh GV-thawed cytoplast (FT), thawed GV-fresh cytoplast (TF). All reconstructed oocytes were cultured in vitro to metaphase II.
  
  
  RESULTS
  Survival rate after manipulation and electrofusion, as well as progression to metaphase II, did not differ significantly among the four groups. Comparing reconstructed oocytes with fresh and thawed control pools, the only difference was a slightly but significantly higher maturation rate in the TT pool versus matched controls (P < 0.01). Cytogenetic analysis of 25 reconstructed oocytes showed the expected number of 20 chromosomes in 88% of them.
  
  
  CONCLUSIONS
  We conclude that both nuclear and cytoplasmic components derived from cryopreserved immature oocytes are suitable for GV transfer procedure, and generate chromosomally normal oocytes able to progress to metaphase II in vitro. The possibility of using cryostored immature oocytes as a source of nuclei and cytoplasm could help in applying GV transfer procedure, both in research and clinical settings.
authors.affiliation: Program for In vitro Fertilization, Reproductive Surgery and Infertility, NYU School of Medicine, New York, USA. femoffa@hotmail.com
authors.forename: Federica
authors.initials: F
authors.lastname: Moffa
authors.forename: Francesca
authors.initials: F
authors.lastname: Comoglio
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Krey
authors.forename: James A
authors.initials: JA
authors.lastname: Grifo
authors.forename: Alberto
authors.initials: A
authors.lastname: Revelli
authors.forename: Marco
authors.initials: M
authors.lastname: Massobrio
authors.forename: John
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001562:Benzimidazoles; D002470:Cell Survival; D002478:Cells, Cultured; D015925:Cryopreservation; D020732:Cytogenetic Analysis; D003593:Cytoplasm / Q000502:physiology; D004247:DNA / Q000032:analysis; D005260:Female; D005456:Fluorescent Dyes; D008677:Metaphase; D051379:Mice; D008846:Micromanipulation; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000502:physiology* / Q000648:ultrastructure*
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; D004247:DNA; C017807:bisbenzimide ethoxide trihydrochloride