title: Comparison of pre- and post-implantation development following the application of three artificial activating stimuli in a mouse model with round-headed sperm cells deficient for oocyte activation.
abstract: OBJECTIVE
  Does the application of three different artificial activating stimuli lead to a difference in pre- and post-implantation embryo development in the wobbler mouse, a mouse model with oocyte activation deficient round-headed sperm cells similar to human globozoospermia?
  
  
  CONCLUSIONS
  No gross differences were found between strontium chloride, electrical pulses or ionomycin with respect to the pre- and post-implantation development in the wobbler mouse.
  
  
  BACKGROUND
  Fertilization failure following intra-cytoplasmic sperm injection (ICSI) occurs in 1-3% of the ICSI cycles in human assisted reproduction technology (ART) and has been successfully overcome by different artificial activating stimuli. No comparison has been made yet in terms of their efficiency and safety.
  
  
  METHODS
  Calcium release and embryo development were compared between oocytes fertilized by wobbler and wild-type (WT) sperm following ICSI with or without three different artificial activating agents. Preimplantation development was assessed on 70 injected oocytes on average per group. On average, 10 foster mothers were used per activating group to compare post-implantation development.
  
  
  METHODS
  We used the wobbler mouse model that possesses oocyte activation deficient round-headed sperm cells. First, the calcium release following ICSI using wobbler sperm was compared with that of WT sperm. Outcome measures were the percentage of oocytes that showed calcium release and their mean amount of calcium rises. Secondly, the pre- and post-implantation development was assessed following ICSI with wobbler sperm plus artificial oocyte activation using either: (i) strontium chloride (Wob-Sr), (ii) electrical pulses (Wob-E) or (iii) ionomycin (Wob-I). Outcome measures were the activation, cleavage and blastocyst rates and the assessment of blastocyst quality by differential staining. Following mouse embryo transfer, pregnancy and birth rates as well as mean litter sizes were examined. Finally, pups were followed up until 8 weeks of age and then mated with fertile controls to assess their fertility.
  
  
  RESULTS
  The percentage of oocytes showing calcium rises as well as the number of calcium rises per oscillating oocyte were significantly lower in the wobbler group when compared with the WT group (9.3 versus 96% and 2.1 calcium rises versus 31 calcium rises) (P < 0.001). The fertilization rate was significantly lower in the wobbler group (11.4%) when compared with the WT group (92.1%) and the artificial activation groups (strontium chloride: 99%, electrical pulses: 99% and ionomycin: 81%, respectively) (P < 0.001). Post-implantation development did not differ significantly between the WT and artificial activation groups, with pregnancy rates in favor of strontium chloride and electrical pulses. The weight of the male pups did not differ between the study groups, whereas the weight of the female pups originating from Wob-Sr embryos was significantly lower at weeks 2, 3 and 4 when compared with female pups originating from WT embryos. However, the latter difference was not observed at later time points, nor in the other artificial activating groups. All offspring mated successfully with fertile controls.
  
  
  CONCLUSIONS
  Results in animal models should be extrapolated with caution to a subfertile human population. Also, ionomycin is currently the most widely used artificial oocyte activating agent in human ART.
  
  
  CONCLUSIONS
  The low frequency of observed calcium rises and the low activation rate make the wobbler mouse a highly suitable model to study oocyte activation deficiency. Strontium chloride and electrical pulses were more efficient means to restore fertilization rates and to support pre- and post-implantation embryonic development than ionomycin.
  
  
  BACKGROUND
  This work was supported by the Flemish foundation of Scientific Research (FWO-Vlaanderen) (aspirant clinical research mandate to F.V.M., fundamental clinical research mandate to P.D.S.); and Ghent University grant (KAN-BOF E/01321/01 to B.H.). The authors have no competing interests to declare.
authors.affiliation: Department for Reproductive Medicine, University Hospital Ghent, De Pintelaan 185-1P4, 9000 Ghent, Belgium. frauke.vandenmeerschaut@ugent.be
authors.forename: F
authors.initials: F
authors.lastname: Vanden Meerschaut
authors.forename: D
authors.initials: D
authors.lastname: Nikiforaki
authors.forename: C
authors.initials: C
authors.lastname: De Roo
authors.forename: S
authors.initials: S
authors.lastname: Lierman
authors.forename: C
authors.initials: C
authors.lastname: Qian
authors.forename: T
authors.initials: T
authors.lastname: Schmitt-John
authors.forename: P
authors.initials: P
authors.lastname: De Sutter
authors.forename: B
authors.initials: B
authors.lastname: Heindryckx
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D004195:Disease Models, Animal; D004594:Electrophysiology; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D007248:Infertility, Male; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D051379:Mice; D009865:Oocytes / Q000166:cytology*; D011247:Pregnancy; D011270:Pregnancy, Animal; D020554:Sperm Injections, Intracytoplasmic; D013094:Spermatozoa / Q000002:abnormalities* / Q000378:metabolism* / Q000473:pathology; D013324:Strontium / Q000494:pharmacology
chemical_list: D015759:Ionomycin; C025700:strontium chloride; D002118:Calcium; D013324:Strontium