Extracellular matrix and intermediate filaments in the first stages and repair of experimental gingivitis in man.

By the indirect immunoperoxidase labelling procedure the expressions of type I and III collagens, laminin and fibronectin and of KL1 cytokeratin and vimentin were examined in the first stages and repair of experimental gingivitis in young subjects. A two month longitudinal study was performed using the tissue from buccal marginal gingival biopsies of four subjects taken sequentially at five specific times: before and during plaque accumulation, and during plaque elimination. The sites examined microscopically were the coronal half of the junctional epithelium and the underlining infiltrated connective tissue fraction. No clinical change could be observed during the study period. Histological examination showed reversible cellular changes during the accumulation of plaque. There were increases in vascularization and cellularity and loss of collagen. They recovered 56 days after plaque elimination their baseline level. Electron microscopic examination showed myofibroblastic aspects in some fibroblasts. The changes in the expression of laminin, fibronectin and KL1 in the J.E. might be due to a proliferation rate enhancement, and suggest an adaptation to the alterations brought about by the inflammatory process. They also reinforce the hypothesis that this epithelium resembles a developmental tissue. Type I collagen demonstrated the "collagen loss-repair" cycle shown in connective tissue by the histological study. The rise in type III collagen and the vimentin fall, both at the initial stage, suggest that these protein profiles may yield information for clinical research purposes during the very early inflammatory process. The variations in fibronectin indicate its key role in the early inflammatory and repair processes. Finally, the variations in matrix and cytoskeletal proteins variations, as well as the morphological modifications observed, were nearly all reversible.