Abstract
Analysis of tissue turnover, the balance between cell proliferation and cell death, can provide important information about our understanding of the biological characteristics of various tissues and their functions. Especially it is very important to study apoptosis, one of the modes of cell death, in surgical pathology specimens. It is very important to note that the whole concept of cell death including apoptosis and oncosis is based on the morphological findings. Therefore, an analysis of morphological features of the cells undergoing the processes of various modes of cell death is very important. DNA fragmentation can be detected in situ by labeling 3′-OH ends with biotinylated deoxyuridine triphosphate (dUTP) through the action of terminal deoxynucleotidyl transferase (TdT).
Since then, this method, subsequently termed 3′-OH nick end labeling, or TdT-mediated dUTP-biotin nick end labeling (TUNEL), has been widely used to detect cells with DNA fragmentation, especially in surgical pathology materials of human disorders. This TUNEL method is now being incorporated into many pathology laboratories throughout the world. However, increasing evidence suggest that TUNEL method is by no means specific for the detection of apoptosis and this method may also detect cells which are committed to, but not yet in the process of apoptosis. Therefore, it is very important to correlate the findings of TUNEL with morphological features of surgical pathology specimens. In addition, it is also important to note that over-fixation is associated with false negative results and insufficient fixation is likely to be associated with false positive results. Therefore, the processing of the specimens including fixation and others is critical in performing TUNEL and its interpretation.
