Analysis of apoptosis: Basic principles and protocols

Apoptosis is a distinct form of cell demise. Originally defined by cellular morphology, apoptosis can now be characterized at the molecular, biochemical, and cellular levels. The detection of apoptosis has become more important, not only in the interests of scientific investigation, but also because of its significance in clinical practice. For example, since apoptosis has been implicated in a variety of devastating diseases such as cancer, therapies targeting apoptosis are being developed. To evaluate the effectiveness of the treatment, one would have to assess the apoptotic response before, during, and after the therapy. For the typical apoptosis, a set of characteristics in cell structure and biochemistry has been well defined. In combination, these provide the basis for apoptosis detection in a given setting. The methodology for analyzing these characteristics is as diverse as the research subjects. Several books devoted to the methodology of apoptosis analysis have recently been published (1-3). Readers may find detailed experimental protocols in these books. This chapter provides an overview of the basic approaches used in analyzing apoptosis, the principle and the basic methodology, in order to provide a quick guide for readers to use when deciding which methods are available and appropriate for their own study. We start with the determination of cell viability and the morphology of dying cells. We then discuss approaches for examining apoptotic changes on the cell membrane, in the cytosol, and in the nucleus. We also summarize some of the common sources of reagents for apoptosis research.