EXPRESSION OF LAMININ-5, FIBRONECTIN, AND EPITHELIUM-ASSOCIATED INTEGRINS IN RECURRENT APHTHOUS ULCERS

Recurrent aphthous ulceration (RAU) is characterized by an ulcerated l esion that persists longer than traumatic ulcers of similar size. This delayed healing phase of the lesion was investigated for extracellula r matrix components and matrix receptors (integrins). The hypothesis t ested was that aphthous ulcers may lack key extracellular matrix compo nents, or their receptors, that are necessary for the migration of mar ginal keratinocytes from the ulcer edge. We immunocytochemically stain ed biopsy specimens of RAUs and non-involved mucosal specimens from HI V+ and non-infected individuals to investigate the presence and distri bution of molecules reported to be associated with reepithelialization of mucosal and cutaneous wounds. Fibronectin, laminin type 5 (kalinin ), and integrin subunits beta 1, beta 4, alpha 6, and alpha v were con sistently found at the margins of RAU, as they are in traumatic ulcers . The alpha 5 and beta 6 subunits were not always present. We also fou nd alpha v in the intact stratified squamous epithelium adjacent to ul cers. Immunohistochemical stains showed disruption in the deposition o f laminin 5 and an apparent lack of fibronectin at the edges of some u lcers. Although these tissue results do not determine which integrin s ubunits are paired with each other, they do show some alterations in t heir expression in RAU. Absence of one or more of these molecules at t he migrating front may contribute to delayed epithelial regeneration. It is likely that the absence or inappropriate expression of keratinoc yte integrins or their extracellular matrix receptors occurs after the causative factors (currently unknown) of the lesion are gone. The rea son for the altered expression of these molecules may be related to th e secretory products (including lymphokines and proteinases) of the ly mphocytic infiltrate.