The Curse Comes Good! Novel Roles for Menstrual Fluid in Endometrial Repair.

While the molecular mechanisms underlying endometrial destruction at menstruation are somewhat understood, the factors which govern post-menstrual repair remain somewhat of a mystery. The elegant electron micrograph work of Ludwig et al. have demonstrated that endometrial re-epithelialization is initiated from the stumps of endometrial glands. However, the signals governing the epithelial migration during re-epithelialization are largely unknown. Using a mouse model of menstruation it has been shown that endometrial repair takes place independently of estrogen. Additionally, factors identified in menstrual effluent such as VEGF and activin A have demonstrated roles in endometrial repair. We propose that menstrual fluid contains 'repair factors' which act in a paracrine manner upon endometrial epithelial cells to enhance re-epithelialization. Menstrual fluid (MF) was collected from normally cycling women on the second day of menstrual bleeding by use of a menstrual cup. Peripheral blood plasma (PB) was collected on the same day by venepuncture to differentiate the effects of specific endometrial factors vs blood borne factors. Samples were normalized for protein content and applied to in vitro wound healing assays utilizing a human endometrial luminal epithelial cell line. The effects of specific VEGF isoforms on endometrial re-epithelialization were also determined in this manner. Epithelial junctional integrity of endometrial epithelial cells grown on Millicell inserts was also determined in the presence of MF or PB by assessment of transepithelial resistance (TER). The presence of specific factors in MF vs PB was determined by ELISA or multiplex analysis. MF enhanced re-epithelialization in vitro on the first 2 days of repair in comparison with PB (P<0.01). MF also enhanced the integrity of epithelial tight junctions assessed by TER, reflecting establishment of a stable polarized monolayer. Assessment of MF has previously identified the presence of VEGF. We demonstrate that VEGF165 mediates more rapid re-epithelialization in vitro versus VEGF121. MF contains factors which mediate endometrial re-epithelialization. MF also enhances endometrial junctional integrity reflecting formation of tight junctions and adherens junctions between epithelial cells, essential for formation of a stable polarized epithelial monolayer. A re-epithelialization factor, VEGF165 enhances endometrial re-epithelialization in vitro. These data have implications for conditions where endometrial repair in compromised such as prolonged menstrual bleeding, a condition which affects up to 17% of women. Identification of repair factors may lead to novel treatments for abnormal uterine bleeding. (platform)