title: The presence of 1 mM glycine in vitrification solutions protects oocyte mitochondrial homeostasis and improves blastocyst development.
abstract: OBJECTIVE
  Embryos generated from oocytes which have been vitrified have lower blastocyst development rates than embryos generated from fresh oocytes. This is indicative of a level of irreversible damage to the oocyte possibly due to exposure to high cryoprotectant levels and osmotic stress. This study aimed to assess the effects of vitrification on the mitochondria of mature mouse oocytes while also examining the ability of the osmolyte glycine, to maintain cell function after vitrification.
  
  
  METHODS
  Oocytes were cryopreserved via vitrification with or without 1 mM Glycine and compared to fresh oocyte controls. Oocytes were assessed for mitochondrial distribution and membrane potential as well as their ability to fertilise. Blastocyst development and gene expression was also examined.
  
  
  RESULTS
  Vitrification altered mitochondrial distribution and membrane potential, which did not recover after 2 h of culture. Addition of 1 mM glycine to the vitrification media prevented these perturbations. Furthermore, blastocyst development from oocytes that were vitrified with glycine was significantly higher compared to those vitrified without glycine (83.9 % vs. 76.5 % respectively; p<0.05) and blastocysts derived from oocytes that were vitrified without glycine had significantly decreased levels of IGF2 and Glut3 compared to control blastocysts however those derived from oocytes vitrified with glycine had comparable levels of these genes compared to fresh controls.
  
  
  CONCLUSIONS
  Addition of 1 mM glycine to the vitrification solutions improved the ability of the oocyte to maintain its mitochondrial physiology and subsequent development and therefore could be considered for routine inclusion in cryopreservation solutions.
authors.affiliation: Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, University of Adelaide, Adelaide, South Australia, Australia. dzander@repromed.com.au
authors.forename: Deirdre
authors.initials: D
authors.lastname: Zander-Fox
authors.forename: Kara S
authors.initials: KS
authors.lastname: Cashman
authors.forename: Michelle
authors.initials: M
authors.lastname: Lane
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects*; D002452:Cell Count; D033481:Chromosomes, Mammalian / Q000187:drug effects / Q000378:metabolism; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D046149:Embryo Culture Techniques; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro; D018507:Gene Expression Regulation, Developmental; D005998:Glycine / Q000494:pharmacology*; D006706:Homeostasis; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects*; D008941:Spindle Apparatus; D013997:Time Factors; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents; D003470:Culture Media; D005998:Glycine