A mouse model of induced menstruation.

A: Ovariectomized (ovx) mice were treated with estradiol (E2) injections and progesterone (P4) releasing implants to stimulate endometrial proliferation and differentiation. Decidualization was induced by injection of oil into one uterus horn. Endometrial bleeding in response to removal of the P4 implant was monitored by vaginal smears or blood collection with tampon-like cotton pads. Uteri collected at indicated points of time were used for histology and analysis of gene expression, leukocyte content and enzymatic activity, respectively. B: Cotton swabs were used to take vaginal smears from mice. Based on a scoring system bleeding intensity was evaluated according to erythrocyte density in H/E stained vaginal smears.