Expression of apoptosis and proliferating cell nuclear antigen (PCNA) in the cardiac conduction system in crib death (SIDS)

Aim of this study is to determine the expression of apoptosis and Proliferating Cell Nuclear Antigen (PCNA) in the cardiac conduction system in crib death and explained death (ED) cases. Postnatal morphogenesis of the conducting tissue is an important part of its normal development. In the atrio-ventricular node (AVN) and His bundle (HB) it consists of degeneration, cell death and replacing in an orderly programmed way. However, its nature and its relation to crib death is not yet fully explained. Apoptosis and PCNA were investigated in 8 heart conduction systems of infants dying of crib death and in 3 conduction systems of infants dying of ED as controls. The cardiac conduction system was removed in two blocks: the first included the sino-atrial node (SAN) and the crista terminalis, the second contained the atrio-ventricular node (AVN), His bundle (HB), bifurcation, and bundle branches. In the conduction systems as well as in the common myocardium the PCNA Labeling Index (PCNA-LI) was found to be negative in all cases. The apoptotic indices (AI) in SIDS and in ED were found to have no statistically significant differences (p>0.05). The SAN, in both groups, showed an AI similar to the one detected in common myocardium. In almost all cases, TUNEL labeling was detected in peripheral region of the AVN, close to the atrial myocardium. The AI was higher in the AVN, HB and the initial tract of bundle branches than in the common myocardium (p<0.05; Student's t test).