Defining apoptosis: Players and systems

OBJECTIVE: To summarize the basic principles and concepts of apoptosis and some of the information to date regarding the nature of the regulation of apoptosis at the molecular level. METHODS: In the past few years, research in cell and molecular biology has led to a much better understanding of the underlying mechanisms that regulate apoptosis. RESULTS: Positive and negative regulatory elements that function in specific cell types to activate apoptosis have been identified. This activation involves signaling pathways that activate distinct proteolytic cascades that lead to the execution of cell death. CONCLUSION: Homeostasis involves a delicate balance between the processes of proliferation, differentiation, and death by apoptosis. The current challenge is to understand how specific stimuli regulate the execution of programmed cell death in basic reproductive cells and how these interactions are integrated into the overall physiology and pathophysiology of reproduction during life. Copyright (C) 1997 by the Society for Gynecologic Investigation.