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

Menorrhagia affects approximately 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 alpha-actin using immunohistochemical techniques in the endometrium of women before and during the perimenopause and with or without menorrhagia. We hypothesized that differences in vessel numbers and types exhibiting alpha-actin staining would exist between these groups, reflecting structural/functional differences. The results showed that perimenopausal menorrhagic women had significantly more smooth muscle alpha-actin expression than non-perimenopausal controls in four out of five menstrual cycle stages (P < 0.05), while perimenopausal non-menorrhagic women demonstrated a significant increase at the mid-proliferative stage only (P < 0.007). No significant differences occurred between women with or without menorrhagia before or during the perimenopause. Perimenopausal women had significantly more straight arterioles (P < 0.02) than women prior to perimenopause at the late secretory stage, while non-perimenopausal women demonstrated significantly higher numbers of spiral arterioles (P < 0.002) in the early secretory stage, although this difference had disappeared by the late secretory stage. In conclusion, we found no major differences in endometrial vascular smooth muscle alpha-actin staining between women with and without menorrhagia, but significant increases in alpha-actin staining in women showing perimenopausal symptoms.