Vascular smooth muscle α-actin distribution around endometrial arterioles during the menstrual cycle: increased expression during the perimenopause and lack of correlation with menorrhagia

Menorrhagia affects −9% of all women, increasing to 20% during the perimenopause. The majority of menstrual loss occurs through the spiral arterioles — specialized endometrial vessels that are intimately involved in controlling menstruation. Our aim was to compare the distribution of vascular smooth muscle α-actin using immunohisto-chemical techniques in the endometrium of women before and during the perimenopause and with or without menor-rhagia. We hypothesized that differences in vessel numbers and types exhibiting α-actin staining would exist between these groups, reflecting structural/functional differences. The results showed that perimenopausal menorrhagic women had significantly more smooth muscle α-actin expression than non-perimenopausal controls in four out of five menstrual cycle stages (P