Confirmed dioestrus in pseudopregnant mice using vaginal exfoliative cytology improves embryo transfer implantation rate

Reprod Biomed Online. 2015 Oct;31(4):538-43. doi: 10.1016/j.rbmo.2015.06.020. Epub 2015 Jul 8.


Embryo transfer is a commonly performed surgical technique. In mice, protocols typically specify pairing recipient females with vasectomized males to induce a receptive uterine environment for embryo implantation. However, this induced receptive state is not always maintained until implantation occurs. The use of a well-characterized correlation between oestrous state and exfoliative vaginal cytology was therefore evaluated to assess uterine receptivity immediately before embryo transfer. Eight- to 12-week-old virgin female CD1 mice (n = 22) were paired overnight with vasectomized males and successfully mated, indicated by the presence of a vaginal plug. These dams underwent embryo transfer 3 days later with embryos obtained from superovulated 4-week-old F1 (C57BL/6 × CBA) females. Non-invasive vaginal lavage was conducted immediately before transfer. Dams were killed 6 days after transfer and the uterus collected for histological analysis. Embryo implantation rate in mice was 96% when cytological analysis of the lavage samples signified dioestrus (n = 6), whereas the implantation rate was <15% (n = 16) when cytology signified other stages of oestrous. This simple, quick, non-invasive measure of receptivity was accurate and easily adopted and, when applied prospectively, will avoid unnecessary surgery and subsequent culling of non-suitable recipients, while maximizing the implantation potential of each recipient female.

Keywords: blastocyst; mouse; optimization; pregnancy; recipient; smear.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Diestrus / physiology*
  • Embryo Implantation*
  • Embryo Transfer / methods*
  • Female
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred CBA
  • Pregnancy
  • Pseudopregnancy / physiopathology*
  • Therapeutic Irrigation
  • Uterus / anatomy & histology
  • Uterus / physiology
  • Vagina / cytology
  • Vagina / physiology