Time-lapse monitoring of mouse embryos produced by injecting sonicated, frozen-thawed sperm heads with high or low chromosomal integrity

Abstract

Purpose: To investigate the first-division kinetics and in vitro development of embryos produced by injecting sonicated sperm heads with high or low chromosomal integrity into oocytes. Methods: Mouse spermatozoa were frozen after separating the sperm heads from the tails by sonication in an EGTA solution (EGTA group) or M2 medium (M2 group). The chromosomal integrity of sonicated mouse spermatozoa was analyzed by injecting the sperm heads into fresh mouse oocytes. The developmental potential of spermatozoa was examined by injecting the sperm heads into vitrified-warming mouse oocytes. We used a time-lapse monitoring system to compare the first-division kinetics. Results: Chromosomal integrity was preserved significantly more frequently in the EGTA group (90.6%) than in the M2 group (32.7%). Blastocysts developed significantly more often in the EGTA group (80.8%) than in the M2 group (39.6%). In the M2 group, with frequent chromosome aberrations, the time between the sperm injection and first cleavage was delayed (18.4 hours), compared to the EGTA group (16.5 hours). All results of the EGTA group were similar to that of fresh epididymal spermatozoa. Conclusion: The EGTA solution for sonication maintained the integrity of sperm chromosomes. Our results revealed a relationship between sperm chromosome integrity and first-division kinetics.