Matrix-degrading metalloproteinases play a major role in tissue remodeling. Recent studies have shown that enzymes of this class are constitutively expressed primarily by stromal cells and not by epithelium. Here we present immunohistochemical evidence that matrilysin is localized within epidermal cells in developing skin and in tumor cells of cutaneous malignancies. The expression of matrilysin protein in developing fetal skin (6-15 weeks) is localized primarily to the germinative basal cell layer of fetal epidermis and early appendageal buds. The buds continue to express matrilysin during mesenchymal invasion. As development progresses (15-19 weeks) matrilysin is concentrated only in cells at the distal portion of the invading follicular and sweat gland appendageal cords. In adult skin, matrilysin was localized specifically to the outer root sheath of the hair follicles and the secretory cells of the eccrine glands but was absent in the epidermis. Nodulocystic, keratotic, adenoid basal cell carcinomas (BCCs) did not express matrilysin. In contrast, in the more aggressive morpheaform (infiltrative) BCCs and recurrent BCCs, matrilysin was localized at the tumor-stromal interface. In squamous cell carcinomas matrilysin was present in tumor cells at the stromal interface surrounding the tumor nests. The demonstration of matrilysin protein in germinal basal cells during fetal skin development and its presence in tumor cells at the stromal junction suggests that this enzyme may contribute to the proteolytic activity associated with cell-extracellular matrix interactions during appendageal development and tumor invasion.
- matrix metalloproteinase / morphogenesis / cell invasion / skin tumors