title: Hydrostatic pressure improves in-vitro maturation of oocytes derived from vitrified-warmed mouse ovaries.
abstract: BACKGROUND
  Cryopreservation has limited successes and in-vitro maturation is used to improve its results. Hydrostatic pressure (HP) plays an important role in follicular development.
  
  
  OBJECTIVE
  This study was designed to examine the effects of HP on in-vitro maturation of oocytes and cell death in cumulus cells derived from vitrified-warmed mouse ovaries.
  
  
  METHODS
  Preovulatory follicles were harvested from non-vitrified and vitrified-warmed 6-8 week-old female NMRI mouse ovaries and randomly assigned to following groups: non-vitrified (control), non-vitrified with HP exposure (treatment I), vitrified-warmed (treatment II) and vitrified-warmed with HP exposure (treatment III). The follicles of treatments I and III were subjected to HP (20 mmHg) for 30 min and after that all groups were cultured for 24h and assessed for in-vitro maturation of oocytes. The viability and apoptosis of cumulus cells and oocytes were assessed using supravital nuclear staining and TUNEL assay, respectively.
  
  
  RESULTS
  Oocytes harvested follicles in both control and treatment II had a significantly lower percentage of metaphase II oocytes (MII) than the treatment I and III (23.5±3.1, 15.03±4.6 and 32.7±3.2, 25.5±4.6; respectively) (p<0.05). Viability of the cumulus cells reduced in treatment I, II and III (83.4, 83.3 and 77.7%) compared to control (86.9%), (p<0.05). The apoptotic index in cumulus and oocyte complexes in treatments I and III (10.7±0.8 and 15.3±0.8) was higher than in control and treatment II (6.7±0.5 and 9.7±0.5) (p<0.05).
  
  
  CONCLUSIONS
  These results demonstrate that HP had a mild effect on cell death incidence in cumulus cells without any effect on oocyte. However, it can be used as a mechanical force to improve in-vitro maturation of oocytes derived from vitrified-warmed mouse ovaries.
authors.affiliation: Fertility and Infertility Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Rashidi
authors.affiliation: Department of Biology, Faculty of Sciences, Razi University, Kermanshah, Iran.
authors.forename: Mehri
authors.initials: M
authors.lastname: Azadbakht
authors.affiliation: Fertility and Infertility Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran.
authors.forename: Mozafar
authors.initials: M
authors.lastname: Khazaei
keywords: Cell death; Hydrostatic pressure; In-vitro maturation; Mouse; Vitrification