Study Of Mouse Morulae And Blastocysts Cryopreservation

Objective:To study the toxic effects of the different concentration of the two cyroprotectants and the different exposure time on the mouse morulae and blastocysts; To compare the developmental potential of mouse morulae, early blastocysts and blastocysts cyropreserved by vitrification , slow- freezing with ethylene glycol or glycerol; To find out the stage which can withstand cyropreservation best in the late development stage of preimplanted mouse embryo.Methed: 1.The embryotoxicity of cyroprotectants was tested by exposing the morulae and blastocysts to FB1 medium which contained 1.5M EG or 1.5M GC for 20min, 6.0M EG FB1 medium for 5min at the room tempreture, compared with FB1 medium contained no cyroprotectant as the control group. The developmental rate after cutured in the M16 medium were examed. 2 morulae, early blastocysts and blastocysts werecryopreserved by vitrification , slow- freezing with EG or GC ,compared the developmental rates after thawing.3 compared the developmental rates when these three stage embryos cryopreserved by vitrification.Results: When morulae, early blastocysts and blastocysts exposed to 1.5M EG or 1.5M GC FB1 medium for20min, 6.0M EG FB1 medium for 5min at the room tempreture , the rates of embryos develop to the next stage during the culture have no statistically significant compared with the control group.2 Both blastocyst rates and hatching rates have no significant different when vitrification compared with EG slow-freezing after the morulae thawing(85.7%vs71.1%, 59. 5%vs42. 2%),but both ofthem higher than GC protocol ( P<0. 01 , P<0.05 ) .Byvitrification , slow-freezing with EG or GC, the expanded blastocystrates of thawed early blastocysts respectively are 65. 7%, 26. 2%, 41%, hatching rates are 51. 4%, 19%, 28. 2%; the re-expanded blastocyst rates are 43.8%, 21. 1%, 22. 5%, and hatching rates are 29. 2%, 10. 5%, 10%. At the early blastocyst and blastocyst stage , the developmental rates by vitrification are higher than by two slow-freezing, but no differents between EG and GC protocol.Conclusion :1.5M EG, 1.5M GC and 6. OM EG appears low toxic effect on mouse morula and blastocyst stage in the freezing protocol. Vitrification make a better results than slow-freezing at early blastocyst and blastocyst stage,EG slow-freezing protocol as good as vitrification for morulae. In slow-freezing , EG is more adaptable to morulae than GC,but has no siginificant in early blastocyst and blastocyst stage. And that the morula is likely the most feasible stage for embryo vitrification.