NEURITOGENESIS ON COLLAGEN SUBSTRATES - INVOLVEMENT OF INTEGRIN-LIKE MATRIX RECEPTORS IN RETINAL FIBER OUTGROWTH ON COLLAGEN

Extracellular matrix molecules such as laminin, fibronectin and collagen promote neurite outgrowth in vitro. We have investigated the capacity of hydrated gels of collagen types I-III and monomeric collagen types I-VI on plastic surfaces to support neuritogenesis. The attachment and survival of explants from the day 6 chick embryo were studied and neurite outgrowth measured as mean elongation rate and maximal neurite length. Collagen types I and III, both as three-dimensional gels or as native monomers supported neuritogenesis equal to or better than laminin. Collagen type V also supported neurite out-growth although less effectively. Collagen types II, IV and VI, as well as denatured collagens of all types tested, did not support outgrowth. The monoclonal anti-beta1 integrin antibody (CSAT), as well as rabbit polyclonal antibodies directed to the integrin beta1-chain, effectively inhibited neurite outgrowth on permissive collagenous substrata, indicating that collagen-binding integrins were involved in the neuritogenesis. These beta1-integrins were independent of Arg-Gly-Asp (RGD) since neurite formation proceeded in the presence of synthetic RGD-containing peptides. Fluorescence immunohistochemistry revealed the presence of the integrin beta1-chain on the outgrowing neurites. The results suggest a possible function of collagen and collagen-binding integrins in the development of the visual system.