Markers of apoptosis in cardiovascular tissues: focus on Annexin V

In the last decade, apoptosis (or programmed cell death) has become appreciated as an important process in the development of the cardiovascular system. Moreover, apoptosis contributes to the adaptation of the system to the environment. We are at the beginning of understanding its relevance to cardiovascular physiology and pathology. This understanding forms the key to implement apoptosis in diagnosis and therapy of cardiovascular diseases. New avenues for pharmacological intervention are expected to arise from the synergy of our knowledge about the molecular mechanisms of apoptosis, and how apoptosis integrates in the complex environment of the cardiovascular tissue. The latter strongly depends on techniques to measure apoptosis. Currently, we are facing a relative paucity in available techniques, covering both specificity and sensitivity, and furthermore allowing quantitative analysis, preferably in combination with morphology. This field, however, is rapidly evolving and is fed by the expanding knowledge about the molecular mechanisms of apoptosis. In this paper we will briefly review the available techniques to detect and/or quantify apoptosis. These methods are based on the analysis of cellular morphology, either by light- or electron microscopy, DNA fragmentation (TdT-mediated X-dUTP nick end labeling or in situ nick end labeling), or cytoplasmic and membrane changes. Furthermore, the advantages and limitations of these techniques for their use in cardiovascular research will be outlined. In the text we will refer to available reviews and protocols which discuss the techniques in more detail. The main part of this article will, however, focus on a recently introduced technique, the Annexin V-based apoptosis detection assay. The principle, characteristics, pro's and contra's of this new apoptosis detection assay will be discussed.