Development of Psoriasis Model in Vitro

Song, In Hwan; Sung, Eon Ki; Kim, Joo Yung; Lee, Yung Chang; Lee, Moo Sam

Abstract

Psoriasis is a disease caused by hyperproliferation of keratinocytes. Pathogenesis of psoriasis is still unclear, but many reports suggest that psoriatic keratinocytes themselves may have some factors of pathogenesis. The author developed artificial psoriatic skin by culturing keratinocytes of psoriasis skin over collagen lattice which was constructed with collagen and normal fibroblasts. After the keratinocytes had grown to full layers of stratification, expression patterns of differentiation marks and ultrastructural changes were investigated by immunohistochemistry and electron microscope. The results were very similar to those of psoriasis skin in vivo as follows. Cytokeratin (CK)10, marker of initiation of differentiation of keratinocytes, was expressed in the spinous layer. CK14, marker of basal cells of stratified squamous epithelium, was expressed in the basal and spinous layer. CK16 and CK17, markers of fast turnover of squamous epithelium, were expressed in the spinous layer. Involucrin, marker of terminal differentiation of squamous epithelium, was expressed weakely over the lower spinous layer. In immuno electron microscopical study, involucrin was expressed but confined to cornified cell envelops in the horney layer. Mitochondria, rER and ribosomes were abundant in the basal layer. They continued to appear in the upper spinous layer but intermediate filaments were scarce. Keratohyalin granules were visible in some parts of the granular layer zone, but the granules were smaller and fewer. In the horney layer, cells were thicker than normal and there were many lipid droplets within the cells. Intercellular spaces were enlarged at the basal layer but disappeared in the upper spinous layer. In these results, non systematic expression of differentiation markers and ultrastructural changes suggest that psoriasis is a disease caused by hyperproliferation of keratinocytes concurrent with unstable maturation and degeneration. Artificial psoriatic skin, in exclusion of systemic or dermal effects, showed very similar results with psoriasis skin in vitro. So it was concluded that psoriasis keratinocytes had some factors of pathogenesis and this kind of model on artificial psoriatic skin can be used for further studying of psoriasis.