ICSI受孕失敗主因為精子無法形成原核PN

ICSI受孕失敗主因為精子無法形成原核PN
>50%ICSI受孕失敗之精子頭部並未融合於卵細胞質中




http://www.biolreprod.org/content/68/4/1341.full

Failure of Male Pronucleus Formation Is the Major Cause of Lack of Fertilization and Embryo Development in Pig Oocytes Subjected to Intracytoplasmic Sperm Injection1

1. Jang-Won Lee, 
2. X. Cindy Tian and 
3. Xiangzhong Yang2

+Author Affiliations

1. Department of Animal Science/Center for Regenerative Biology, University of Connecticut, Storrs, Connecticut 06269

 

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Abstract

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 16–20 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.

FIG. 1.

The process of ICSI in pig oocytes and the development of blastocysts from ICSI embryos. A) A spermatozoon (arrowhead) is aspirated into the injection pipette. B) A centrifuged oocyte with a visible polar body (arrow) is secured by a holding pipette and the spermatozoon (arrowhead) is about to be injected. C) The spermatozoon (arrowhead) is expelled into the cytoplasm of the oocyte. D) Blastocysts derived from ICSI oocytes after 168 h of in vitro culture

FIG. 2.

Nuclear morphology of abnormal ICSI embryos stained with Hoechst. A) An embryo with two pronuclei (PN) and two polar bodies (Pb) 16–18 h after ICSI, suggesting normal fertilization. B) A two-cell embryo 24 h after ICSI, suggesting normal embryonic development. C) An oocyte with an intact sperm (is), a pronucleus, and a polar body 16–18 h after ICSI.D) An activated embryo that failed to cleave has one intact sperm head and two pronuclei. E and F) After 168 h of in vitro culture, embryos with many nuclei in the cytoplasm still contain an intact sperm head (E) or a decondensed sperm head (ds; F), suggesting embryo development was derived from the female pronucleus only