Structural analysis of extracellular matrix prior to the migration of cephalic neural crest cells

Cephalic neural crest cells enter cell free areas containing abundant extracellular matrix (ECM). Previous histochemical studies have identified both sulfated and non-sulfated glycosaminoglycans within this matrix. In the present study, ultrastructural examination of the ECM demonstrated an anastomosing network of pleomorphic, cetyl pyridinium chloride-dependent strands within cell free spaces and in association with the basement membrane of the surface ectoderm. Thin section analysis revealed that the strands consisted of three components: (1) 3-5 nm filament meshwork; (2) electron dense amorphous material and (3) 30 nm granules. In contrast, the ECM associated with the basement membrane consisted principally of a continuum of electron dense, amorphous material. The molecular ordering of ECM within crest cell pathways was compared to the well-characterized, hyaluronate-rich, premigratory matrix of cardiac jelly.