Pilot Study On The Technique Of Human Oocyte Cryopreservation By Slow-freezing Method

ObjectiveInvestigation on human mature(MII) and immature(GV/MI) oocytes cryopreservation by slow-freezing method, analyzing the developmental potentiality of the oocytes and the influential factors. We aim to establish the connection among the freeze procedure, the stage of oocyte maturation and the post-thaw oocyte's fertilizability and the early embryo developmental capacity and intend to search after a fit technique of slow-freezing method for human oocytes cryopreservation.MethodsA total of 67 mature oocytes were obtained from consented infertility patients undergoing IVF-ET treatment, who donated their superfluous oocytes. These oocytes were divided into three groups randomly and froze-thawed in different conditions. To compare these groups' developmental potentiality in different concentrations of SSS and different methods of removing granules. 25 fresh oocytes from patients undergoing IVF-ET treatment were served as control group. The effects of cryopreservation on the oocyte's developmental potentialityity were analyzed.A total of 82 immature oocytes, obtained from ovarian tissue during gynecological operation, were randomly divided into two groups. The immature oocytes of freezing group were in vitro matured after froze-thawed. The immature oocytes of control group were in vitro matured without froze. To observe the developmental potentiality of theoocytes of two groups. Analyzing the important factors that influence the developmental potentiality of the post-thaw immature oocytes.Results1 The rate of post-thaw survival of the immature oocytes was 66.67%. For immature oocytes, There was no significant differences in the maturation rate(47.37% vs 28%), fertilization rate(66.67% vs 57.14%), cleavage rate(33.33% vs 50.00%) and high-quality embryo rate(25.00% vs 50.00%) between freezing group and control group(P<0.05). No one blastocyst was achieved in two groups.2 For mature oocytes, in Group A, the rate of post-thaw surivival, fertilization and cleavage was 33.33%, 25.00% and 50.00%, respectively. No one high-quality embryo, morula and blastocyst was achieved in Group A. In Group B, the rate of post-thaw surivival, fertilization, cleavage, high-quality embryo, morual and blastocyst was 52.38%, 63.64%, 57.14%, 50.00%, 25.00% and 25.00%, respectively. In Group C, the rate of post-thaw surivival, fertilization, cleavage, high-quality embryo, morual and blastocyst was 77.27%, 70.59%, 75.00%, 55.56%, 2.22% and 11.11%, respectively. In control group, the rate of fertilization, cleavage and high-quality embryo was 80.00%, 85.00% and 52.94%, respectively. The rate of post-thaw survival(33.33% vs 52.38%), fertilization(25.00% vs 63.64%) and cleavage(50.00% vs 57.14%) of Group A were less than that of Group B, but there were no significant differences between two groups(P>0.05). There were no significant differences in the rate of post-thaw survival (52.38% vs 77.27%), fertilization(63.64% vs 70.59%), cleavage(57.14% vs 75.00%), high-quality embryo(50.00% vs 55.56%), morula(25.00% vs 22.22%) and blastocyst(25.00% vs 11.11%) between Group B and Group C(P>0.05). No significant differences were found in the rate of fertilization (70.59% vs 80.00%), cleavage (75.00% vs 85.00%) and high-quality embryo (55.56% vs 52.94%) between freezing group(Group C) and control group (P>0.05).