Hydrostatic pressure improves in-vitro maturation of oocytes derived from vitrified-warmed mouse ovaries

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. materials and 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). conclusion: 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.