Morphometric quantification of apoptotic stages in cell culture

Apoptosis is an active process of self-destruction, whereby cells undergo physiological cell death. It occurs during development and regulation of tissue homeostasis or as a result of changes in environmental stimuli. Chromatin condensation and nuclear fragmentation, which are typical features of apoptotic nuclei, are usually quantified by fluorescent DNA dyes. The present study reports a reliable method to analyze morphological apoptotic stages in cultured cells, using light microscopy. We used the human neuroblastoma cell line SK-N-BE as a model to study apoptosis induced by inadequate cell-matrix interactions. Apoptosis was detected on cells cultured for different time intervals on polyHEMA, poly-L-lysine or collagen I. Quantitative morphometric and densitometric analysis after hematoxylin nuclear staining and caspase-3 immunocytochemistry, as markers of occurring apoptosis, were performed. Our method identifies different stages of caspase-3 activation and the subsequent DNA fragmentation and condensation. This experimental procedure enables us to detect slight differences in apoptosis progression by morphological analysis.