Embryonic behavior of two-cell mouse embryos frozen by the one- and two-step ultrarapid techniques.
OBJECTIVE
A modified two-step ultrarapid freezing technique was compared to the one-step ultrarapid freezing technique. Two-cell mouse embryos were frozen-thawed using the two freezing protocols, and postthaw cryoprotectant removal was carried out in either a single- or a multiple-step procedure.


RESULTS
Statistically similar cryosurvival (96.95-100%) and blastocyst formation rates (87.95-91.47%) were obtained with both freezing groups. In addition, the method of cryoprotectant removal did not have any significant effect on the survival and development of the frozen-thawed embryos in both groups. Blastocysts formed following single-step cryoprotectant removal had significantly lower inner cell mass counts in the one-step than in the two-step group (26.14 and 27.59, respectively; P < 0.05). Embryo transfer studies showed that the implantation and fetal formation rates of embryos frozen by the two-step technique (61.67 and 60.0%, respectively) were similar to those of embryos frozen by the one-step technique (74.12 and 71.76%, respectively).


CONCLUSIONS
These results demonstrate that the ultrarapid two-step technique is as effective in cryopreserving two-cell mouse embryos as the ultrarapid one-step technique.
Vasuthevan
S
S
Department of Obstetrics and Gynaecology, National University Hospital, Singapore.
Ng
S C
SC
Bongso
A
A
Ratnam
S S
SS
D000818:Animals; D002970:Cleavage Stage, Ovum / Q000187:drug effects / Q000502:physiology; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL / Q000196:embryology; D008808:Mice, Inbred CBA / Q000196:embryology; D011247:Pregnancy
D003451:Cryoprotective Agents