Cautionary note on the use of end-labelling DNA fragments for detection of apoptosis

The gastrointestinal epithelum undergoes a continual process of cell renewal which is partly regulated by apoptosis. The process of growth and differentiation is greatly enhanced in the terminal ileum after massive small bowel resection, a well-established model of intestinal adaptation. We have applied the terminal deoxynucleotidyl transferase (TdT)-mediated UTP nick end-labelling (TUNEL) method to establish the role of apoptosis in intestinal adaption in terminal ileum of control animals after small bowel resection. Healing skin wound and lymph node were used as positive control tissue for apoptotic cells. We report that considerable inter-animal variation was observed in the intestinal tissue. We believe that caution is required in the interpretation of TUNEL staining in intestinal tissue and in its use as a specific marker for apoptosis in this setting.