Women's business: understanding uterine bleeding

The author describes research examining the molecular and cellular interactions within the endometrium that govern the initiation of menstruation. The fall in progesterone in the late secretory phase of the cycle affects the progesterone-receptor positive stromal cells, which, via communication with the epithelial cells, result in production of chemokines, cytokines and other factors that promote trafficking and activation of leukocytes in the tissue. These and the stromal cells produce MMPs and other proteases that activate MMPs, thus altering the balance between active MMPs and TIMPs at foci, resulting in the tissue breakdown at menstruation. (non-author abstract)