Embryonic dormancy phenomenon in obstructed healthy mouse fallopian tubes

Purpose: A mouse model of unilateral oviductal obstruction was designed to study whether healthy oviducts can support embryo development in an advance d stage toward blastocyst hatching and implantation when the embryos in the contralateral side normally move into the uterine cavity. Methods: The oviducts of 80 female ICR mice (aged 5-8 weeks) were ligated u nilaterally 12-40 hr postcoitus. The ligated oviducts were isolated from da y 4 to 19.5 postcoitus. Embryos within the ligated oviducts were then flush ed out to record the developmental stage and compared with the conceptuses in the contralateral uterine horns with unligated oviducts. Embryos recover ed from ligated oviducts were then cultured in vitro to observe their poten tial for further development. Results: In 33 mice, 53.4% (163/305) and 86.1% (241/280) of the morphologic ally normal blastocysts had hatched from the zona pellucida within the obst ructed tube and contralateral uterine horns, respectively, on the 5th day p ostcoitus. The data demonstrated that the hatching process could take place within the obstructed fallopian tube, but the timing was delayed. From 5.5 to 19.5 days postcoitus, a total of 362 implanted embryos were obtained in unligated control uterine horns, but none of the 404 embryos in the artifi cially obstructed oviducts were implanted. The embryos within the ligated t ubes were dormant in the hatched blastocyst stage as demonstrated by their ability to continue growing (98.2%) when removed from the oviduct to an in vitro environment. Conclusions: In this study, We demonstrate that mouse embryos can hatch, al though delayed, in obstructed healthy oviducts. Tubal pregnancy is not like ly to happen in artificially obstructed healthy mouse fallopian tubes, sinc e all the viable embryos were dormant at the hatched blastocyst stage.