Zona opening with 308 nm XeCl excimer laser improves fertilization by spermatozoa from long-term vasectomized mice

Spermatozoa from long-term vasectomized mice have greatly reduced fertilizing ability in vivo and in vitro, which makes this a useful animal model for male factor infertility. The purpose of this study was to evaluate the 308 nm XeCl excimer laser for opening the zona pellucida to enhance the fertilization rate with spermatozoa from vasectomized males. Inseminating zona-intact (control) oocytes with 5 x 10(6) spermatozoa/ml resulted in only 6% fertilization and 33.3% development to the blastocyst stage; zona-opened oocytes showed significant improvement with 31.5% fertilization, 90% cleavage to the 2-cell stage, and 72.2% blastocyst formation. Out of the 130 oocytes in the experimental group, zona ablation was performed successfully on 127 and only three were damaged. These results suggest that laser micromanipulation for assisted fertilization potentially offers a simplified and precise method for mechanical zona cutting.