Effects of cigarette smoke on fertilization and embryo development in vivo.
OBJECTIVE
To determine the effects of smoking on eggs and subsequent embryo development by maternal exposure to cigarette smoke.


METHODS
Mice were exposed to cigarette smoke or cigarette smoke condensate (CSC) for 4 weeks and then examined for development and telomere function of embryos in vitro after fertilization. In addition, the effects of continuous smoke on embryo development and telomere length were determined by treating mice for 4 weeks, followed by continuous exposure to cigarette smoke or CSC after fertilization.


METHODS
Laboratory study.


METHODS
CD1 mice.


METHODS
Mice were exposed to cigarette smoke or CSC.


METHODS
The percentage (rate) of blastocyst development, quality of embryos assessed by total cell number, apoptosis, Oct4 expression (a molecular marker of embryonic stem cells), telomere length and loss, and chromosomal instability were compared between smoke- and CSC- treated mice and sham-treated mice.


RESULTS
Mice exposed to cigarette smoke or CSC for 4 weeks exhibited increased egg fragmentation or delayed fertilization, thus reducing development to blastocysts in vitro. Fragmented eggs showed increased reactive oxygen species. Mice exposed to smoke or CSC showed increased apoptosis and altered expression of Oct4 in developed embryos. The effects of smoke or CSC on embryo development showed a dose-dependent relationship to exposure time. Exposure to smoke or CSC beginning 4 weeks before fertilization altered expression of Oct4 and increased apoptosis in blastocysts. Notably, the rate of abnormal embryos significantly increased in the smoke and CSC groups. Smoke and CSC shortened telomeres in embryos, but their telomere shortening was not enough to induce major chromosome abnormalities in mice, which have unusually long telomeres.


CONCLUSIONS
Together, the whole animal exposure model shows that cigarette smoke induces oxidative stress, telomere shortening, and apoptosis, and compromises embryo development in vivo.
Huang
Junjiu
J
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, Florida; College of Life Sciences, Sun Yat-Sen University, Guangzhou, People's Republic of China.
Okuka
Maja
M
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, Florida.
McLean
Mark
M
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, Florida.
Keefe
David L
DL
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, Florida. Electronic address: dkeefe@health.usf.edu.
Liu
Lin
L
Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, Florida; College of Life Science, Nankai University, Tianjin, People's Republic of China. Electronic address: liutelom@yahoo.com.
D000818:Animals; D004622:Embryo, Mammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047108:Embryonic Development / Q000187:drug effects*; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D019570:Inhalation Exposure / Q000009:adverse effects; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D051379:Mice; D011247:Pregnancy; D017382:Reactive Oxygen Species / Q000378:metabolism; D012906:Smoke / Q000009:adverse effects*; D014026:Nicotiana; D014028:Tobacco Smoke Pollution / Q000009:adverse effects
D017382:Reactive Oxygen Species; D012906:Smoke; D014028:Tobacco Smoke Pollution