DIFFERENTIATION-ASSOCIATED LOCALIZATION OF SMALL PROLINE-RICH PROTEININ NORMAL AND DISEASED HUMAN SKIN

The expression of SPRR (small proline-rich protein) was investigated i n normal human skin and in diseased skin from patients with psoriasis, squamous cell carcinoma, basal cell epithelioma, naevus pigmentosus, ichthyosis vulgaris and several inflammatory skin diseases, by immunoh istochemical staining, A polyclonal antibody was raised against a synt hetic peptide for a C-terminal common region for SPRR1 and SPRR3. In i mmunoblot analysis, a positive band of 18 kDa was detected, which show ed the presence of SPRR1 in human epidermal keratinocytes, In normal e pidermis, positive staining for SPRR was observed in keratinocytes in the granular layer and the uppermost or two spinous cell layers, with no staining of the other spinous or basal layers. The staining was obv ious at the cell periphery, weak at the cytoplasm, and absent in the n ucleus, Staining was observed in several outer layers of the follicula r infundibulum to the isthmus. No staining was detected in the inner r oot sheath of the hair follicles, hair matrix, sebaceous gland, eccrin e gland, eccrine duct, melanocytes, Langerhans cells or fibroblasts, T he arrectores pilorum, striated muscles, muscle layers of vessels, and myoepithelia of eccrine gland, were weakly stained. In psoriatic skin , stained keratinocytes were distributed in the spinous cell layers ex cept for the basal layer. In ichthyosis vulgaris, SPRR was barely expr essed in the uppermost living cell layers of the epidermis. In epiderm olytic hyperkeratosis, degenerated squamous cells widely expressed SPR R, In Darier's disease, dyskeratotic cells were clearly stained. In sq uamous cell carcinoma, staining was observed in keratotic cells around horny pearls, In basal cell epithelioma, naevus pigmentosus, and mali gnant melanoma, the tumour cells or naevus cells were not stained. The distribution of SPRR was similar to that of involucrin in normal and several diseased skin, except for ichthyosis vulgaris. We conclude tha t SPRR is expressed in close association with epidermal differentiatio n in normal skin and skin diseases. The alteration of the expression o f the proteins correlated to terminal differentiation, and differs fro m disease to disease.