In Vitro Systems for the Study of Apoptosis

Abstract

Publisher Summary This chapter provides a brief review of the expanding field of in vitro apoptosis studies. First, the chapter describes the cell-free systems reported thus far and provides some comments on the unique attributes of each system. Second, tentative criteria for validation of new apoptotic systems are proposed. These are based on the current understanding of the morphological and biochemical processes of apoptotic cell death. Finally, the methodologies that have been used for analyzing the systems are described together with a number of the more significant findings achieved from such analyses. The advantage of cell-free systems in the study of apoptosis is that they can overcome the stochastic nature of the onset of apoptotic events in cell populations. Several cell-free systems have been devised that recapitulate the morphological changes of apoptosis using components isolated from cells such as nuclei, cytoplasm, and organelles. These cell-free systems offer several advantages in the biochemical analysis of cell death pathways. The nuclei used as substrates for in vitro apoptosis reactions are typically isolated from healthy cells. Thus, the apoptosis-inducing signal comes from the extracts rather than the nuclei. These extracts seem to show no species or tissue specificity for substrate nuclei. The extracts can induce apoptotic changes in nuclei from a wide variety of sources such as human HeLa cervical carcinoma cells, GM3798 lymphoblastoid cells, Jurkat T cells, CEM T lymphoblastoid cells, mouse S49 cells, mouse liver, hamster liver, rat liver, rat thymocytes, and Xenopus sperm nuclei assembled in vitro. This apparently passive role of nuclei in the execution of apoptosis is consistent with experiments indicating that apoptotic changes can proceed even in cytoplasts, which lack nuclei.