Effect of Incubation Temperature and Warming Solutions on the Viability and Maturation of Vitrified-thawed Human Immature Oocytes

ObjectiveTo investigate the viability and maturation of frozen-thawed human immature oocytes exposed to different temperature of vitrification and warming solutions.MethodsThe immature oocytes in germinal vesicle (GV) and matephase I (Mi) stages were collected from our ICSI patients and exposed to different temperature of vitrification and warming solutions before frozen in the freezing/thawing procedures. The different temperature groups were as follows: Group A, equilibration solution at 37 °C, vitrification solution at room temperature, warming solution at 37 °C; Group B, both vitrification and warming solution at room temperature; Group C, both vitrification and warming solutions at 37 °C; Group D, the frozen-thawed oocytes and the fresh oocytes were cultured for in vitro maturation. The survival rate and maturation rate were compared among groups. The oocytes were examined using immunofluorescent stainingand confocal microscopy to check the spindle configuration and chromosome arrangement.ResultsThe survival rates and Mn rates of GV stage oocytes in groups A, B, C were 100%(15/15), 81.3%(13/16), 68.8%(11/16) and 33.3%(2/6), 83.3%(10/12),72.7% (8/11), respectively. The survival rate of group C was significantly lower than that of the control (P<0.05). The normal spindle and chromosome configuration were only observed in group B, with the rates of 20% (2/20) and 10% (1/10), respectively. The survival rates of Mi stage in groups A, B, C were 71.4%(10/14), 100% (12/12) and 83.3%(10/12), no significantly difference from that of the control (100%, 14/14). The Mn rates of Mi stage in groups A, B and C were 0%(0/14), 66. 7%(8/12) and 80% (8/10), respectively. The M II rate in group A was significantly lower than that in other groups (P<0.01). Only one oocyte in group C was found with normal spindle and chromosome configurations.ConclusionThe appropriate operation temperature of vitrification and warming solutions can improve the outcomes of the vitrified-thawed human immature oocytes.