Patterns of cell death: the significance of apoptosis for dermatology.

Development, function, remodelling, and senescence of multicellular organisms depend on the coordinated occurrence of physiological, actively induced cell death in two major patterns: terminal differentiation and programmed cell death (apoptosis). Apoptosis is a highly selective form of "cell suicide" with characteristic morphological and biochemical features: chromatin condensation, formation of apoptotic bodies, and DNA fragmentation by activation of endonucleases. Here, we outline the current understanding of apoptosis and its subtypes, discuss their biological functions, and delineate why apoptosis is relevant to the skin and its diseases. We distinguish apoptosis from necrosis, and discuss the regulation of apoptosis by selected genes, hormones, growth factors and cytokines. The epidermis and the regressing hair follicle offer interesting models for studying the as yet ill-understood biology of epithelial cell apoptosis. The selective manipulation of cell death programs may become part of the therapeutic arsenal of clinical dermatology.