Apoptosis in the human female reproductive tract

Throughout fetal and adult life, the balance of cell proliferation and cell death determines the size of cell populations in tissues throughout the body. Apoptosis, or programmed cell death, is the physiologic process of cell deletion. Cell death is critical in morphogenesis in the embryo and fetus as well as in maintaining tissue homeostasis in the adult. Throughout the menstrual cycle, cell death and renewal occur in the female reproductive tract in a highly regulated sequence. The process of follicular atresia and the cyclic shedding of the endometrium involve the process of apoptosis. In pathologic states, resistance to cell death by apoptosis may play a fundamental role in tumorigenesis. Because apoptosis is such a fundamental biologic process in a variety of physiologic and pathologic states, many unique to the female reproductive tract, it is imperative that clinicians be conversant with the rapidly expanding information in this area. Although apoptotic cell death has been recognized histologically for over 20 years (1), the molecular mechanisms that regulate apoptosis have only recently begun to be elucidated. The identification of some of these regulators, such as the p53 gene, has improved our understanding of the mechanisms of tumor response to chemotherapy. This review will summarize our current knowledge of the mechanisms of apoptosis in the ovary and endometrium, and in the normal development and malignant transformation of the breast.