Relationship between keratinocyte adhesion and death: anoikis in acantholytic diseases

Loss of attachment to the substratum may trigger apoptosis in epithelial cells (anoikis). It is less clear whether apoptosis may be triggered by disruption of cell-cell contacts, as happens in acantholytic diseases. Biopsy specimens were obtained from the border of skin lesions from four patients with pemphigus vulgaris (PV), four patients with pemphigus foliaceus (PF), three patients with Darier's disease (DD), two patients with Darier's-type Grover's disease (GD), and two patients with benign familial pemphigus Hailey-Hailey disease (HH). Control skin was obtained from five healthy volunteers. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling) and confocal laser scanning microscopy was employed to detect the nuclei containing fragmented DNA in apoptotic cells. In PV and PF, TUNEL-stained apoptotic keratinocytes were abundantly present in the regions of acantholysis and in the cohesive epidermis below the blisters. Apoptotic keratinocytes had pyknotic, condensed nuclei. In DD, GD and HH, the number of TUNEL-stained keratinocytes was lower, apoptotic keratinocytes were confined to the regions of dyskeratosis and acantholysis, and pyknosis was absent. In conclusion, disruption of cell-cell contacts in acantholytic skin disorders may in some cases cause apoptosis of keratinocytes. Further studies are needed to determine whether the observed differences in the pattern of apoptosis are due to targeting of different junctional elements (adherens junctions in PV and PF versus desmosomes in DD, GD and HH).