Possible role of monkey gingival fibroblasts in external basement membrane maintenance.

Morphological and immunocytochemical investigations were made of the interface between the junctional epithelium and connective tissue in gingiva from young monkeys (Macaca fuscata). Some fibroblasts with conspicuous cytoplasmic organelles, including the elements of rough endoplasmic reticulum, the Golgi apparatus, and mitochondria, were found close to the external basement membrane in the connective tissue underlying the junctional epithelium. Occasionally, cytoplasmic cell processes either made contact with the lamina densa of the basement membrane or came into direct contact with the plasma membrane of the basal layer of junctional epithelium cells. Fragments of a structure like that of the basement membrane were observed between the process and the basal cells. Fibroblasts could be seen very close to the disrupted portion created by the passage of leukocytes migrating into the junctional epithelium through the external basement membrane. Immunoperoxidase methods demonstrated a positive reaction product for laminin on the external basement membrane. This product was observed in the rough endoplasmic reticulum of junctional epithelium cells and of gingival connective tissue fibroblasts located close to the junctional epithelium basement membrane. The cytoplasm of fibroblasts distant from the epithelium, however, demonstrated no immunoreactivity. These results suggest that, in cooperation with epithelial cells, some fibroblasts located near the junctional epithelium can produce such basement membrane components as laminin and that these components may serve to stabilize and/or restore previously assembled basement membrane.