Immunohistological study of wound healing in periodontal tissue of rats. Distribution of fibronectin and laminin after flap operation

Abstract

This study describes the distribution of fibronectin and laminin in periodontal tissue of rats after a flap operation. After full thickness flaps were raised, the roots were surgically exposed and planed. Animals were sacrificed at 12 hours, and 1, 3, 5, 7, 14, 28 and 56 days after the wounding. The block specimens were fixed in formalin, decalcified with EDTA, made into serial paraffin sections, and examined after hematoxylin and eosin staining, after Masson-trichrome staining and by indirect immunofluorescence for the presence of fibronectin and laminin. After the wounding, fibronectin was detected in the fibrin clot, and the migratory epithelial cells crossed over this fibrin clot (12 hours-5 days). Fibronectin was deposited heavily in the granulation tissue. When the gingival connective tissue had matured, fibronectin diminished (5-14 days). On the root surface, a layer of fibronectin was present in the region where connective tissue fibers were oriented parallel to the root surface, while no fibronectin was seen at the site of reattachment of the regenerated collagen bundle (14-56 days). Laminin was present in the basement membrane of normal epithelium and blood vessels, but was absent from the internal basal lamina. After the wounding, laminin was absent from the basement membrane zone of the distal site of the migrating epithelium (1-3 days). Upon completion of wound reepithelialization at 5-7 days after wounding, laminin reappeared throughout the basement membrane except the internal basal lamina. These results suggest that fibronectin may be important in the regeneration of epithelium, connective tissue and connective tissue attachment during repair by functioning as an extracellular provisional matrix for migrating cells. On the other hand laminin may be important in maintaining the normal epithelium.