Embryo splitting can increase the quantity but not the quality of blastocysts

• Published in: Taiwanese journal of obstetrics & gynecology 2012-06, Vol.51 (2), p.236-239
• Main Authors: Tang, Hsun-Han, Tsai, Yung-Chieh, Kuo, Cheng-Tsung
• Format: Article
• Language: English
• Subjects: blastomeres; embryo biopsy; embryo splitting; Internal Medicine; in vitro fertilization; Obstetrics and Gynecology
• ISSN: 1028-4559
• DOI: 10.1016/j.tjog.2012.04.012

Abstract Objective In this study, we investigated the developmental potential of single blastomeres that were obtained from 4-cell mice embryos that were split during the blastocyst stage. Materials and Methods Imprinting Control Region (ICR) mice (age: 6–8 weeks), were superovulated and mated with a single fertile male of the same strain. We obtained 2-cell embryos that were then cultured in 4 groups (×4) with Human tubal fluid (HTF) supplemented with 12% fetal bovine serum. When these embryos reached the 4-cell stage, their zonae pellucidae were removed and every single blastomere was isolated by repeated pipetting with Ca/Mg2+ -free medium. The isolated blastomeres (study group) and the intact embryos (control group) were then cultured to determine the blastocyst formation rate and quality. Results We collected a total of 936 embryos from 524 morphologically intact, top-grade embryos in the 4-cell stage from 80 stimulated mice. We used 356 of these embryos to isolate the blastomeres. The remaining 168 embryos were cultured as controls. A total of 1312 single blastomeres were obtained and cultured in vitro . Among these, 620 blastocysts were harvested from the original embryos compared with 136 blastocysts that were harvested from the control group. The overall blastocyst formation rate was 174.2% (620 blastocysts from 356 embryos) for the study group compared with 81.5% (136 blastocysts from 168 embryos) for the control group. The study group was 43.3% (268 of 620) top-grade blastocysts compared with 91% (152 of 168) of the control group. Taken together, the percentage of top-grade blastocysts obtained per original embryo in the split group was 75.4% (174.2% × 43.3%) compared with 74.2% (81.5% × 91%) for the control group. Conclusions Embryo splitting can increase the number of blastocysts. However, the percentage of available top-grade blastocysts is the same compared with nonsplit embryos. Embryo splitting may not be a cost-effective technique for the generation of high-quality mouse blastocysts.