Influence of culturing temperature and proteinase inhibitors on the spontaneously occurring changes in the organ culture of psoriatic skin

Abstract

Skin explants from involved psoriatic lesions showed dissociation of keratinocytes, dermal-epidermal separation and degenerative changes such as cytoplasmic swelling of subcorneal prickled cells within 24 h after culture initiation at 37°C in the absence of fetal bovine serum (FBS). These histological changes developed time dependently, while normal skin explants did not exhibit such phenomena. Some of the uninvolved psoriatic skin explants showed only degerative change 48 to 72 h after culture initiation at 37°C. To determine the nature of these spontaneously occurring changes in psoriatic skin explants and then to approach the pathogenesis of psoriasis, the effects of FBS, various proteinase inhibitors (PIs) and culturing temperature (37, 31, 24°C) were examined in skin organ culture of normal and involved psoriatic skin. At 37°C, only serine PIs (5 or 10 mg/ml of soybean trypsin inhibitor (SBTI), 1000 KIU/ml of aprotinin, or 2 mg/ml of comostat mesilate in the medium) or FBS (20% in the medium) could suppress the occurrence of dissociation of keratinocytes and dermal-epidermal separation but not the degenerative change in involved psoriatic skin explants, while other types of PIs did not exhibit any such inhibition. When the culturing temperature was reduced from 37°C to 31 or 24°C, the formation of dissociation of keratinocytes and dermal-epidermal separation was almost non-existent and only moderate degenerative change was observed. The addition of FBS or serine PIs to the culture at 31°C revealed the formation of very weak degenerative change. Furthermore, the addition of two different serine PIs, 2 mg/ml of camostat mesilate and 5 mg/ml of SBTI, almost completely inhibited not only dissociation of keratinocytes and dermal-epidermal separation but also degenerative change in involved psoriatic skin explants cultured at a reduced temperature (31°C). These results indicate that there were elevated levels of serine proteinase(s) in psoriatic epidermis which might be involved in dissociation of keratinocytes and/or dermal-epidermal separation with a possible heat-activation system, and may furthermore be involved in degeneration at higher layers of the psoriatic epidermis.