Quantification of Apoptosis in Mouse Atherosclerotic Lesions

Apoptosis is a key process occurring in atherosclerosis, both in humans and in animal models. Apoptosis occurs in all cell types studied thus far, and thus lineage marking is often necessary. Apoptosis should be ascertained using a combination of morphological features and activation of specific pathways (e.g., terminal UTP nick end labeling-TUNEL). Both TUNEL and cryptic epitope antibodies (e.g., cleaved caspase 3) can be used, although they will often give different frequencies. Apoptotic frequency but not rate can be estimated from these methods, as we do not know the timing of apoptosis or how much of the process is marked by each method. We describe the morphological and immunohistochemical methods used in our laboratory to detect apoptotic cells in animal and human atherosclerotic plaques.