Activation, Pronuclear Formation, and Development In Vitro of Pig Oocytes Following Intracytoplasmic Injection of Freeze-Dried Spermatozoa1

Activation, Pronuclear Formation, and Development In Vitro of Pig Oocytes Following Intracytoplasmic Injection of Freeze-Dried Spermatozoa
June 23, 2004
In-Kiu Kwon, Ki-Eun Park and Koji Niwa
Biology of Reproduction
The fertilization of pig oocytes following intracytoplasmic injection of freeze-dried spermatozoa was evaluated. Activation and male pronuclear (MPN) formation were better in oocytes injected with isolated freeze-dried sperm heads than whole freeze-dried spermatozoa, but cleaved embryos were generally difficult to develop to the morula or blastocyst stage. When spermatozoa were freeze-dried for 24 h, oocyte activation and MPN formation in activated oocytes after sperm head injection were inhibited. Embryo development to the blastocyst stage was only obtained after injecting sperm heads isolated from spermatozoa freeze-dried for 4 h and stored at 4?C. The proportion of embryos that developed to the blastocyst stage was not increased by the treatment of injected oocytes with Ca ionophore (5?10 ?M). Increasing the sperm storage time did not affect oocyte activation or MPN formation, but blastocyst development was observed only after 1 mo of storage. These results demonstrate that pig oocytes can be fertilized with appropriately freeze-dried spermatozoa and that the fertilized oocytes can develop to the blastocyst stage.
1 Supported in part by a Grant-in-Aid for Creative Scientific Research from the Japan Society for the Promotion of Science (13GS0008).
2 Correspondence. FAX: 81 86 251 8388; kniwa@cc.okayama-u.ac.jp