RNA-SYNTHESIS AND SPLICING INTERFERES WITH DNA IN-SITU END LABELING TECHNIQUES USED TO DETECT APOPTOSIS

The detection of DNA fragmentation by the use of the TUNEL technique h as become a standard technique for the detection of apoptosis in tissu e sections, DNA cleavage, detected by the TUNEL technique, is the last irreversible stage of the apoptosis cascade, When the nuclear DNA is cleaved in oligonucleosomal-sized fragments, processes such as transcr iption are completely abolished. The values of apoptotic cell death th at were obtained for atherosclerotic plaques by the TUNEL technique ra nged from less than 2% up to 60%, The latter value would indicate that plaques are in an imminent state of collapse, which is certainly not the case. Other factors that could result in TUNEL labeling have to be considered, Therefore, we developed a co-localization system and stud ied TUNEL labeling together with markers of RNA transcription and spli cing, The present study demonstrates that, besides apoptotic nuclei, n on-apoptotic nuclei that show signs of active gene transcription are l abeled by the TUNEL technique, The fact that the TUNEL technique is no t specific for the executive phase of apoptosis is not surprising, as the technique is only selective (rather than specific) for apoptotic n uclei as these contain a far greater degree of DNA fragmentation than non-apoptotic nuclei. Therefore, we think that the TUNEL technique sho uld be combined with additional techniques, such as markers of transcr iption and morphological criteria.