Monitoring Cellular Proliferation and Apoptosis in Atherosclerosis Plaques and Intimal Thickenings

Immunohistochemistry for specific proteins characteristic of proliferative or apoptotic cells allows for monitoring of these cell behaviors in biological tissues samples, including atherosclerotic plaques and intimal thickenings. Proliferating cell nuclear antigen (PCNA) and Ki-67 are widely used markers of cell proliferation and cleaved caspase-3 is a well-established marker of apoptosis that can be detected in tissue samples using immunohistochemistry. This technique enables quantification of the abundance of these proteins and provides information on the distribution of these biomarkers in tissues. By combining with immunohistochemistry for specific cell type markers, it is also possible to determine which cell types are proliferating or undergoing apoptosis. Here, we detail protocols for immunohistochemistry of PCNA, Ki-67, and cleaved caspase-3 for evaluation of cellular proliferation and apoptosis in atherosclerotic plaques in vivo. In addition, we outline methods for the quantification and localization of cell proliferation using bromodeoxyuridine/5-bromo-2'-deoxyuridine (BrdU) and ethynyldeoxyuridine/5-ethynyl-2 ́-deoxyuridine(EdU) labeled tissue samples collected from animals exposed to BrdU or EdU.