Which methodology is commonly used to identify cellular apoptosis in tissues?

The TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) assay is commonly utilized to identify cellular apoptosis because it specifically labels DNA strand breaks that occur as a result of apoptosis. During apoptotic cell death, there is fragmentation of DNA, and the TUNEL assay works by incorporating labeled nucleotides at these sites of DNA damage. This allows for the visualization of apoptotic cells under a microscope, making it a powerful tool in histopathology for assessing the extent of cell death within tissue samples.

In contrast, immunohistochemistry is primarily used for detecting specific proteins in tissues and may not directly indicate cellular apoptosis. Western blotting focuses on the analysis of proteins and their expression levels, rather than the identification of cells undergoing apoptosis. Cell viability assays assess the overall health and number of living cells, but they do not provide specific information about the cellular processes involved in apoptosis. Thus, the TUNEL assay stands out as the most direct and effective method for identifying apoptotic cells within tissues.