Sequential appearance of fibronectin and collagen in experimental granulation tissue

The sequential appearance of fibronectin and collagenous proteins was studied by immunofluorescence in experimental granulation tissue in the mouse. Granulation tissue was induced by subcutaneous implantation of viscous cellulose sponges into the neck. When sponges were invaded by granulation tissue, fibronectin appeared early together with the invading fibroblasts. Interstitial collagens, type III and type I, appeared 2 to 7 days later. When the collagen had matured into bundles, fibronectin diminished or disappeared. The results suggest that fibronectin functions as a primary matrix for organization of the collagenous connective tissue during the tissue repair process.