THE 72-KDA AND THE 92-KDA GELATINASES, BUT NOT THEIR INHIBITORS TIMP-1 AND TIMP-2, ARE EXPRESSED IN EARLY PSORIATIC LESIONS

Psoriasis is histologically characterized by hyperkeratosis and papill omatosis with elongated vessels in the upper dermis. In order to evalu ate the role of gelatinases in remodelling psoriatic skin in this stud y we examined the production of the 72-kDa (gelatinase A), 92-kDa coll agenase (gelatinase B) and their tissue inhibitors TIMP-2 and TIMP-1. A total of 19 patients affected by different types of psoriasis were i ncluded in this study. An immunohistochemical study on cryosections wa s performed using antibodies to 72-kDa gelatinase, 92-kDa gelatinase, TIMP-1, TIMP-2, laminin, collagen types I, III, IV, VII. mRNA expressi on for gelatinases and their inhibitors were also analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). In 14 of 19 patients there was a positivity in 92-kDa protein expression in keratinocytes. The 92-kDa gelatinase protein was also present in the upper dermis wi th prevalence around blood vessels. In 15 of 19 patients the 72-kDa wa s localized in the upper dermis, almost exclusively in the papillary d ermis but absent in epidermis. TIMP-1 and TIMP-2 were both negative in all cases in immunoperoxidase and RT-PCR. Using RT-PCR we show that t he 72-kDa mRNA is expressed exclusively in the dermis, on the contrary the 92-kDa was present in epidermis and dermis. Type I, III, IV and V II collagens did not show any alteration or disruption. Overexpression and production of gelatinases without inhibitory effects suggest a ro le of these proteins in remodelling the psoriatic skin probably induci ng the typical histological pattern of papillomatosis.