HISTOCHEMICAL-STUDIES OF HYALURONAN AND THE HYALURONAN RECEPTOR ICAM-1 IN PSORIASIS

Histochemical stainings of frozen sections of human normal and psoriat ic skin were used to study the localization of hyaluronan (HA) and int ercellular adhesion molecule 1 (ICAM-1). HA staining was found in ail areas oi the shin, with the exception of the stratum corneum, in both normal and psoriatic cases without any apparent quantitative differenc es between the conditions. The staining for ICAM-1 was detected in ves sels in normal skin and at lower levels in norma; areas of the shin in patients with psoriasis. However, in these patients the staining incr eased io about the same level as in normal skin after hyaluronidase tr eatment of the sections prior to staining. in psoriatic lesions, disti nct staining for ICAM-1 was localized mainly to vessels and infiltrati ng leukocytes. Treatment of the sections with hyaluronidase increased the staining of vessels only slightly, but more strongly around leukoc ytes. These findings show that ICAM-1 is predominantly free from bound HA on vessel endothelium in psoriasis lesions but not on vessels in n ormal areas of the shin, and suggests that systematically administered HA, previously shown to reduce chronic inflammation in animal models, might have a beneficial effect in psoriasis via blocking of endotheli al ICAM-1 and thereby causing a reduced invasion of leukocytes into th e skin