Cryopreservation of mouse embryos at morula/compact stage

Purpose: The objective of this article was to study mouse morula/compact st age embryo postthaw survival rates and postthaw developmental potential. Methods: Mouse morula/compact stage embryos were classified into 3 substage s. Their morphological behavior during the freezing and thawing process wer e examined Postthaw survival rates and blastocyst formation rates were comp ared between the three substages and the pronucleate and the 2-cell stage e mbryos. Finally, Postthaw fully compacted and late compact embryos were tra nsferred to foster mothers. Results: Blastomeres of early compacting embryos separated from each other during the freezing process whereas in fully compacted and late compact sta ges the blastomeres remain compacted. Fully compacted and late compact stag e embryos had higher Postthaw survival rates than other stages, though thos e weve not statistically significant (P > 0.05). These two substages had si gnificantly higher blastocyst formation rates than Postthaw pronucleate and early compacting embryos (P < 0.01). A total of 72 Postthaw fully compacte d and late compact embryos were transferred and 20 live offspring were deli vered. Conclusions After passing early compacting stage, fully compacted and late compact stage mouse embryos have high Postthaw survival rates and significa ntly higher blastocyst formation rates Successful cryopreservation of embry os at these two substages has a significant value in embryo selection. The results obtained in this study may provide useful information for human ass isted reproductive technology.