DIFFERENTIAL EXPRESSION OF CD44S AND CD4V10 PROTEINS AND SYNDECAN IN NORMAL AND IRRADIATED MOUSE EPIDERMIS

The role of the CD44s adhesion molecule, its epithelial isoforms and i ts relationship to epidermal proteoglycans such as syndecan was studie d in normal and irradiated mouse skin. In normal mouse skin, only 10% of basal cells are strongly CD44s-immunopositive, with a cytoplasmic e xpression pattern. Double-label experiments with the basal cell marker keratin 14 confirmed the epithelial nature of the strongly CD44s-posi tive cell type in the basal layer. Some spinous keratinocytes and the majority of the remaining basal cells exhibited a weak membranous stai ning pattern. In contrast, the epithelial isoform, CD44v10, was strong ly present in all basal and suprabasal epithelial cells of the epiderm is, with a membranous staining pattern. Syndecan was found in the gran ular layer of the normal epidermis only. After 1 week of daily irradia tion, the entire basal cell layer of the epidermis expressed CD44s in the membrane, but with a varying degree of staining intensity. This re activity spread to the upper spinous layer after 3 weeks of treatment. In hyperproliferative epidermis, there was no difference in the stain ing patterns between CD44s and CD44v10. The expression of syndecan swi tched from the granular layer to the basal and lower spinous layers af ter 2 weeks of daily irradiation. Immunoreactivity for syndecan was al so strongly enhanced in the dermis of irradiated samples. The results suggest an important role for syndecan and CD44 in proliferative proce sses during radiation-induced accelerated repopulation.