Distribution of basal lamina type IV collagen and laminin in normal rat tongue mucosa and experimental oral carcinoma: ultrastructural immunolocalization and immunogold quantitation.

The relationship of basal lamina, a form of specialised extracellular matrix which separates epithelial cells and other cell types from adjacent stroma, to the behaviour of malignant neoplasms of epithelial origin is not well understood. However, it is widely acknowledged that the properties of local invasion and metastasis of carcinomas are linked to extracellular matrix (including basal lamina) changes. In the present study, the distribution of the major basal lamina components, type IV collagen and laminin, in normal rat tongue mucosa and experimentally induced oral carcinomas was investigated using post-embedding immunogold techniques and electron microscopy. The expression of these components was also quantitatively analysed using morphometry and immunocytochemistry. Results indicated that type IV collagen and laminin were confined to the lamina densa of normal oral epithelial basal lamina, and that both components were also detected in the lamina densa of basal lamina associated with carcinomas, and in the extracellular matrix of tumours. Furthermore, laminin was detected within stromal fibroblasts in normal tissues and experimental carcinomas. Quantitative analysis indicated that expression of laminin was significantly increased in carcinomas. In contrast, type IV collagen expression was significantly decreased. The quantitative changes observed in the two basal lamina constituents may be related to the process of tumour invasion, reflecting altered metabolic activities of tumour and stromal cells. These observations may be of use in understanding the architectural characteristics of oral mucosa basal lamina and in assessing the malignant potential of epithelial dysplasias or "premalignant" lesions.