Deposition of extracellular matrix along the pathways of migrating fibroblasts

Fibroblasts from rat, mouse and chick embryos cultured on poly-lysine/fibronectin- or poly-lysine/laminin-coated dishes were stained with antibodies directed to extracellular matrix molecules. The staining showed that cells had migrated during culture and deposited extracellular matrix components along their migration trails. Depending on the antigen, the staining of the matrix revealed fibrils, spots or a diffuse smear along the migration pathways. The major matrix components were fibronectin and heparan sulfate proteoglycan; however, laminin nidogen, tenascin, glia-derived nexin (GDN) and chondroitin-4-sulfate proteoglycan were also found. The migration trails were also detectable by scanning electron microscopy. Here, the fibrils were the prominent structures. The deposition of matrix was independent from the substratum: fibronectin was deposited on laminin, plain poly-lysine, basal lamina and even on fibronectin. Functional assays using anti-fibronectin or an antiserum to embryonic pigment epithelium basement membrane disturbed the formation of matrix fibrils, but did not inhibit cell attachment and translocation. Likewise, heparin in the culture medium only partially inhibited cell migration, despite the fact that it disturbed the formation of proper matrix fibrils. Our results suggest that the deposition of extracellular matrix by cells may not be mandatory for attachment and translocation. However, the deposition of matrix along defined trails might be important for the pathfinding of cells or nerve fibers that appear later in development.