Increasing Pregnancy Rate in Mice Using Vaginal Cy-tology in Different Phases of Estrus Cycle in Mice

Background: Determining different stages of the estrus cycle is an effective method for tracking various stages of the cycle, as well as selection of mature mice that are ready for pregnan-cy or pseudo-pregnancy. Determining different phases of the estrus cycle is possible by examining the changes in vaginal smear epithelial cells, which is not only quick and inexpensive, but also one of the most accurate methods for identifying vari-ous stages of mouse estrus cycle. The stages of estrus period were determined according to the proportions and morphology of leukocytes and epithelial cells. In the proestrus dominance stage only nucleated cells are observed. The estrus phase con-sists of the Cornified cells. The next stage, Metestrus, represent the same percentage of Cornified cells, nucleated cells and leu-kocytes. Finally, in the diestrus stage leukocytes are dominant. Materials and Methods: In order to prepare sterile speci-mens from mouse vagina, physiological sterile sodium chloride (0.9% NaCl) was used and the samples were stained using 0.1% crystal violet dye. After vaginal smear and determination of es-trus cycle stages, the mice were mated individually for with va-sectomized male mice overnight, and the mice vaginal plaque was observed and recorded the following morning.Results: 30 ten weeks old mice were selected, of which 11 mice were in the Proestrus and Estrus cycle. Of these 11 mice, 81.8% were positive for plaque and ready for mating. The rest mice were in the Metestrus and Diestrus cycle, of which only 2 (10.5%) mice showed positive plaque, i.e. ready for mating. Conclusion: Mice that are in the Proestrus and Estrus stages are ready to mate and after mating, pregnancy or pseudopreg-nancy is achievable. Therefore, the proestrus and estrus cycle, can be considered as the best time for embryo transfer to recipi-ent mice.

کلیدواژه ها:

Pregnancy ، Mice ، Vaginal Cytology ، Estrus Cycle