expression of heat shock protein (hsp a1a) and mnsod genes following vitrification of mouse mii oocytes with cryotop method

background: the aim of this study was to investigate the effects of two vitrification protocols on mouse metaphase stage ii (mii) oocytes and evaluate their effects on the expression of heat shock protein a1a (hsp a1a) and mnsod genes. materials and methods: groups of approximately 15 oocytes without cumulus complexes were collected and vitrified with 10% (v/v) ethylene glycol (eg) + 10% (v/v) dimethylsulphoxide (dmso) + 0.5m sucrose in group a (vsi) and 14.5% (v/v) eg + 14.5% proh + 0.5m sucrose in group b (vsii), respectively. thawing after vitrification was performd by placing the oocytes into 1m sucrose for 1 minute and two diluted solutions, each for 3 minutes. after thawing, the oocytes were fertilized and cultured in vitro to develop into the pronuclear stage. the survival rate of vitrified-warmed oocytes and rate of fertilization were evaluated. in addition, gene expressions (hsp a1a, mnsod and β actin) of vitrified-warmed oocytes were also examined by reverse transcription polymerase chain reaction (rt-pcr). results: survival rates of each group were separately compared to the control. the result showed significant differences between each experimental group compared to the control (p≤ 0.001). the survival rate of oocytes after warming was higher in vsi (91.2% ± 1.7) compared to vsii (89.2% ± 1.5) but there were no significant differences between the two groups. the rate of fertilization was significantly (p≤0.05) reduced in vitrified-warmed (vsi: 39% ± 5.8; vsii: 34% ± 5.7) oocytes compared to the control (88.36% ± 2.3). the expression of mnsod increased in the vitrified-warmed oocytes when compared to control oocytes. we also detected hsp a1a only in the control and vsi group. conclusion: vitrification of oocytes by cryotop resulted in high survival rate; low developmental competence and fertilization rate of vitrified-warmed oocytes which may be a result of changing expression of important genes after thawing.