Up-regulation of serpin SCCA1 is associated with epidermal barrier disruption

Parakeratosis, the persistent presence of nuclei in the stratum corneum (SC) is associated with serious disruption of skin barrier function. Squamous cell carcinoma antigen 1 (SCCA1) is strongly up-regulated in inflamed and parakeratotic skin.

To find a biochemical marker for the SC barrier disruption, especially the disruption associated with parakeratosis.

An ELISA assay system was established to quantify SCCA1 in the extract of tape-stripped cornified cells. Transepidermal water loss (TEWL) and other skin parameters were measured and compared with the amount of SCCA1. Localization of SCCA1 was investigated immunohistochemically in various skin diseases with parakeratosis. Nuclei and SCCA1 on the skin surface were detected by staining of corniocytes collected on an adhesive-coated slide glass.

SCCA1 showed strong up-regulation in lesional skin with psoriasis (466-fold), hayfever skin caused by Japanese ceder pollen (232-fold) and sun-exposed skin of healthy individuals (90-fold) compared to their normal sun-protected skin. The increased levels of SCCA1 were well correlated with increased values of TEWL and the number of parakeratotic cells in the SC. Furthermore, subjects with high levels of SCCA1 in the epidermis were more susceptible to barrier disruption by external stimuli, and this was accompanied with a further increase of SCCA1. We confirmed that localization of SCCA1 was limited to parakeratotic areas by using the skin surface staining technique. Immunohistochemical study also demonstrated that SCCA1 was always present at high levels in parakeratotic epidermis.

All of our findings indicate that SCCA1 plays an important role in the induction of epidermal barrier disruption. SCCA1 may be a critical determinant of barrier function in the epidermis.