Tissue transglutaminase in the small intestine of the mouse as a marker for apoptotic cells. Colocalization with DNA fragmentation

Besides the morphological changes in cells undergoing apoptosis, such as ch romatin condensation and cell shrinkage, histological demonstration of DNA fragmentation by in situ end labeling (ISEL) has been widely used for the d emonstration of apoptotic cells in tissue sections. Although DNA fragmentat ion can be demonstrated in apoptotic cells and apoptotic bodies in most cas es, there is no clear correlation of ISEL staining with apoptosis. It has o ften been demonstrated that, in many morphologically intact cells, nuclei w ith fragmented DNA can be found. Thus staining with ISEL for the detection of apoptosis is useful only in connection with other markers for apoptosis as, for example, characteristic morphological changes. Here we show that ti ssue transglutaminase protein is unequivocally expressed in apoptotic enter ocytes as shown by DNA fragmentation and morphology. Tissue transglutaminas e is not expressed in enterocytes with healthy morphology, although DNA fra gmentation call be demonstrated in these cells. Thus the immunohistochemica l demonstration of tissue transglutaminase may serve as a simple marker for apoptotic epithelial cells in tissue sections.