Diversity of Menstrual Cycle, Formation of Decidual Cells, and Lack of Endometrial Glands in Spiny Mouse.

Recent discovery of menstruation in the Egyptian spiny mouse (Acomys cahirinus) highlighted this species as a feasible model for the study of menstrual cycle physiology. However, reports on active menstrual bleeding in this animal were contradictory, so we set out to reproduce major findings in the field. Using vaginal smear microscopy and occult blood assay, we have failed to detect menstrual bleeding in spiny mice from our colony at Lomonosov Moscow State University. Otherwise, we demonstrated appearance of well-defined decidual cells during the late secretory phase of the cycle that correlated with an increase in serum progesterone. Comparing the uteri of spiny mice from our colony vs. CD1 strain laboratory mice housed in the same animal unit, we have found several noteworthy features: (1) absence of endometrial glands, (2) higher volume of nerve fibers in the endometrium, and (3) spiral-like arteries in myometrium. Taking results of other groups into account, our results highlight putative diversity of menstrual cycles in spiny mice from different colonies and demonstrate important differences in uterus structure compared to M. musculus.