Acantholysis and spongiosis are associated with loss of syndecan-1 expression

Background: Syndecan-1, a heparan sulfate proteoglycan present on the membr ane of keratinocytes, functions in intercellular adhesion. Acantholysis and spongiosis are both characterized by diminished intercellular adhesion tha t may lead to blister formation. In spongiotic conditions, desmosomal stret ching occurs prior to cell separation while in acantholytic conditions, cel l separation occurs without stretching. While many of the structural relati onships have been described, the molecular interactions regulating keratino cyte to keratinocyte adhesion are not yet fully understood. Methods: Sections from ten cases of Grover's disease, two pemphigus vulgari s, one pemphigus foliaceus, one bullous pemphigoid, two herpes simplex, and ten spongiotic dermatitis were stained with BB-4, a monoclonal anti-syndec an-1 antibody. Results: Nine of ten Grover's, all three pemphigus, and both herpes cases s howed absent or markedly decreased syndecan-1 expression by acantholytic ke ratinocytes, with a sharp delineation from adjacent unaffected skin. The re maining Grover's case showed moderate loss of syndecan-1 expression. Te pem phigus foliaceus case showed retention of staining along the basal cell lay er, but expression was lost in the mid stratum spinosum. All ten spongiotic cases showed a diffuse mild decrease in staining, with loss of syndecan-1 expression surrounding microvesicles. Bullous pemphigoid, as expected, did not show loss of syndecan expression. Conclusions: The loss of syndecan-1 expression evident in acantholytic cond itions and, to a lesser extent in spongiotic conditions, may contribute to the decreased intercellular adhesion characteristic of these lesions.