BOR - Papers in Press, published online ahead of print
October 30, 2002.
Biol Reprod 2002, 10.1095/biolreprod.102.009001
BIOLOGY OF REPRODUCTION 68, 13411347 (2003)
DOI: 10.1095/biolreprod.102.009001
© 2003 by the Society for the Study of Reproduction, Inc.
Failure of Male Pronucleus Formation Is the Major Cause of Lack of Fertilization and Embryo Development in Pig Oocytes Subjected to Intracytoplasmic Sperm Injection1
Jang-Won Leea,
X. Cindy Tiana, and
Xiangzhong Yang2,a
a Department of Animal Science/Center for Regenerative Biology, University of Connecticut, Storrs, Connecticut 06269
The objectives of this study were 1) to compare the efficiency of intracytoplasmic sperm injection (ICSI) with and without additional artificial stimulation using frozen-thawed sperm and in vitro-matured porcine oocytes and 2) to determine the nuclear anomalies of ICSI oocytes that failed to fertilize or develop. In experiments 1 and 2, we evaluated the effects of additional activation treatments, e.g., electrical stimulus, Ca ionophore (A23187), and/or cycloheximide, on fertilization and development of ICSI porcine oocytes. Significantly higher fertilization, cleavage, and blastocyst rates were obtained for oocytes treated with a combination of ICSI and electrical activation (EA) (P < 0.05) than for those treated with ICSI alone. However, different combinations of electrical and chemical activation treatments did not further improve the rates of fertilization, cleavage, and blastocyst development for ICSI embryos. To elucidate the association between sperm head decondensation and oocyte activation and to investigate the cause of embryonic development failure, in experiment 3 we evaluated the nuclear morphology of oocytes 1620 h after ICSI. Nearly 100% of oocytes showed female pronucleus formation after ICSI regardless of activation treatment. However, failure of male pronucleus formation with intact or swelling sperm heads was observed in some ICSI embryos, suggesting that these embryos underwent cell division with the female pronucleus only. Artificial activation (EA and A23187) had a beneficial effect on embryonic development, sperm decondensation was independent of the resumption of meiosis, and the failure of formation of a male pronucleus was the major cause for fertilization failure in porcine ICSI embryos.
1 This manuscript is scientific contribution 2102 to the Storrs Agricultural Experimental Station at the University of Connecticut.
2 Correspondence. FAX: 860 486 0534; jyang{at}canr.uconn.edu
Copyright © 2003 by the Society for the Study of Reproduction.