title: The relationship between pregnancy outcome and smooth endoplasmic reticulum clusters in MII human oocytes.
abstract: BACKGROUND
  During ICSI, we occasionally observe pronucleus sized translucent vacuoles. We investigated why these vacuoles occur and determined the effect on pregnancy outcome.
  
  
  METHODS
  Translucent vacuole-positive oocytes and the corresponding cohort were examined by transmission electron microscopy (TEM) and histochemical staining with DiI and ER-Tracker. Stimulation methods, hormonal levels, patients' condition and grade of transferred embryos were compared between vacuole-positive and vacuole-negative cycles.
  
  
  RESULTS
  By TEM, we confirmed that the vacuoles were tubular-type smooth endoplasmic reticulum clusters (sERCs). Numerous small sERCs were also observed in the oocytes from the same cohort. Veeck's grades of transferred embryos were higher in sERC-positive cycles and fertilization rate was similar to those of sERC-negative cycles. However, in sERC-positive cycles, significantly lower pregnancy and higher biochemical pregnancy rates were shown. Serum estradiol levels on the day of hCG administration were significantly higher in sERC-positive cycles.
  
  
  CONCLUSIONS
  The presence of sERCs is associated with lower chances of successful pregnancy, even in sERC-negative oocytes from the same cohort that are transferred along with the sERC-positive oocytes. High estradiol levels could be one of the causes of sERC formation.
authors.affiliation: Nagai Clinic, Misato, Saitama 341-0004, Japan. midori@nagai-cl.com
authors.forename: J
authors.initials: J
authors.lastname: Otsuki
authors.forename: A
authors.initials: A
authors.lastname: Okada
authors.forename: K
authors.initials: K
authors.lastname: Morimoto
authors.forename: Y
authors.initials: Y
authors.lastname: Nagai
authors.forename: H
authors.initials: H
authors.lastname: Kubo
mesh_terms: D015331:Cohort Studies; D004624:Embryo Transfer; D018871:Endoplasmic Reticulum, Smooth / Q000648:ultrastructure*; D004958:Estradiol / Q000097:blood; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008677:Metaphase; D008854:Microscopy, Electron; D009865:Oocytes / Q000166:cytology* / Q000648:ultrastructure*; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic; D014617:Vacuoles / Q000648:ultrastructure
chemical_list: D004958:Estradiol